1<HTML> 2<HEAD> 3<!-- This HTML file has been created by texi2html 1.52b 4 from gperf.texi on 1 February 2009 --> 5 6<META HTTP-EQUIV="content-type" CONTENT="text/html; charset=UTF-8"> 7<TITLE>Perfect Hash Function Generator</TITLE> 8</HEAD> 9<BODY> 10<H1>User's Guide to <CODE>gperf</CODE> 3.0.4</H1> 11<H2>The GNU Perfect Hash Function Generator</H2> 12<H2>Edition 3.0.4, 1 February 2009</H2> 13<ADDRESS>Douglas C. Schmidt</ADDRESS> 14<ADDRESS>Bruno Haible</ADDRESS> 15<P> 16<P><HR><P> 17<H1>Table of Contents</H1> 18<UL> 19<LI><A NAME="TOC1" HREF="gperf.html#SEC1">GNU GENERAL PUBLIC LICENSE</A> 20<LI><A NAME="TOC2" HREF="gperf.html#SEC2">Contributors to GNU <CODE>gperf</CODE> Utility</A> 21<LI><A NAME="TOC3" HREF="gperf.html#SEC3">2 Introduction</A> 22<LI><A NAME="TOC4" HREF="gperf.html#SEC4">3 Static search structures and GNU <CODE>gperf</CODE></A> 23<LI><A NAME="TOC5" HREF="gperf.html#SEC5">4 High-Level Description of GNU <CODE>gperf</CODE></A> 24<UL> 25<LI><A NAME="TOC6" HREF="gperf.html#SEC6">4.1 Input Format to <CODE>gperf</CODE></A> 26<UL> 27<LI><A NAME="TOC7" HREF="gperf.html#SEC7">4.1.1 Declarations</A> 28<UL> 29<LI><A NAME="TOC8" HREF="gperf.html#SEC8">4.1.1.1 User-supplied <CODE>struct</CODE></A> 30<LI><A NAME="TOC9" HREF="gperf.html#SEC9">4.1.1.2 Gperf Declarations</A> 31<LI><A NAME="TOC10" HREF="gperf.html#SEC10">4.1.1.3 C Code Inclusion</A> 32</UL> 33<LI><A NAME="TOC11" HREF="gperf.html#SEC11">4.1.2 Format for Keyword Entries</A> 34<LI><A NAME="TOC12" HREF="gperf.html#SEC12">4.1.3 Including Additional C Functions</A> 35<LI><A NAME="TOC13" HREF="gperf.html#SEC13">4.1.4 Where to place directives for GNU <CODE>indent</CODE>.</A> 36</UL> 37<LI><A NAME="TOC14" HREF="gperf.html#SEC14">4.2 Output Format for Generated C Code with <CODE>gperf</CODE></A> 38<LI><A NAME="TOC15" HREF="gperf.html#SEC15">4.3 Use of NUL bytes</A> 39<LI><A NAME="TOC16" HREF="gperf.html#SEC16">4.4 The Copyright of the Output</A> 40</UL> 41<LI><A NAME="TOC17" HREF="gperf.html#SEC17">5 Invoking <CODE>gperf</CODE></A> 42<UL> 43<LI><A NAME="TOC18" HREF="gperf.html#SEC18">5.1 Specifying the Location of the Output File</A> 44<LI><A NAME="TOC19" HREF="gperf.html#SEC19">5.2 Options that affect Interpretation of the Input File</A> 45<LI><A NAME="TOC20" HREF="gperf.html#SEC20">5.3 Options to specify the Language for the Output Code</A> 46<LI><A NAME="TOC21" HREF="gperf.html#SEC21">5.4 Options for fine tuning Details in the Output Code</A> 47<LI><A NAME="TOC22" HREF="gperf.html#SEC22">5.5 Options for changing the Algorithms employed by <CODE>gperf</CODE></A> 48<LI><A NAME="TOC23" HREF="gperf.html#SEC23">5.6 Informative Output</A> 49</UL> 50<LI><A NAME="TOC24" HREF="gperf.html#SEC24">6 Known Bugs and Limitations with <CODE>gperf</CODE></A> 51<LI><A NAME="TOC25" HREF="gperf.html#SEC25">7 Things Still Left to Do</A> 52<LI><A NAME="TOC26" HREF="gperf.html#SEC26">8 Bibliography</A> 53<LI><A NAME="TOC27" HREF="gperf.html#SEC27">Concept Index</A> 54</UL> 55<P><HR><P> 56 57<P> 58Copyright (C) 1989-2009 Free Software Foundation, Inc. 59 60</P> 61 62<P> 63Permission is granted to make and distribute verbatim copies of 64this manual provided the copyright notice and this permission notice 65are preserved on all copies. 66 67</P> 68<P> 69Permission is granted to copy and distribute modified versions of this 70manual under the conditions for verbatim copying, provided also that the 71section entitled ���GNU General Public License��� is included 72exactly as in the original, and provided that the entire resulting 73derived work is distributed under the terms of a permission notice 74identical to this one. 75 76</P> 77<P> 78Permission is granted to copy and distribute translations of this manual 79into another language, under the above conditions for modified versions, 80except that the section entitled ���GNU General Public License��� may be 81included in a translation approved by the author instead of in the 82original English. 83 84</P> 85 86 87 88<H1><A NAME="SEC1" HREF="gperf.html#TOC1">GNU GENERAL PUBLIC LICENSE</A></H1> 89<P> 90Version 3, 29 June 2007 91 92</P> 93 94 95<PRE> 96Copyright (C) 2007 Free Software Foundation, Inc. <A HREF="http://fsf.org/">http://fsf.org/</A> 97 98Everyone is permitted to copy and distribute verbatim copies of this 99license document, but changing it is not allowed. 100</PRE> 101 102 103<H2>1.0 Preamble</H2> 104 105<P> 106The GNU General Public License is a free, copyleft license for 107software and other kinds of works. 108 109</P> 110<P> 111The licenses for most software and other practical works are designed 112to take away your freedom to share and change the works. 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The terms of this 721License will continue to apply to the part which is the covered work, 722but the special requirements of the GNU Affero General Public License, 723section 13, concerning interaction through a network will apply to the 724combination as such. 725 726<LI>Revised Versions of this License. 727 728The Free Software Foundation may publish revised and/or new versions 729of the GNU General Public License from time to time. Such new 730versions will be similar in spirit to the present version, but may 731differ in detail to address new problems or concerns. 732 733Each version is given a distinguishing version number. If the Program 734specifies that a certain numbered version of the GNU General Public 735License ���or any later version��� applies to it, you have the option of 736following the terms and conditions either of that numbered version or 737of any later version published by the Free Software Foundation. If 738the Program does not specify a version number of the GNU General 739Public License, you may choose any version ever published by the Free 740Software Foundation. 741 742If the Program specifies that a proxy can decide which future versions 743of the GNU General Public License can be used, that proxy's public 744statement of acceptance of a version permanently authorizes you to 745choose that version for the Program. 746 747Later license versions may give you additional or different 748permissions. However, no additional obligations are imposed on any 749author or copyright holder as a result of your choosing to follow a 750later version. 751 752<LI>Disclaimer of Warranty. 753 754THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 755APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 756HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ���AS IS��� WITHOUT 757WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT 758LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 759A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND 760PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE 761DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR 762CORRECTION. 763 764<LI>Limitation of Liability. 765 766IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 767WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR 768CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, 769INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES 770ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT 771NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR 772LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM 773TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER 774PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 775 776<LI>Interpretation of Sections 15 and 16. 777 778If the disclaimer of warranty and limitation of liability provided 779above cannot be given local legal effect according to their terms, 780reviewing courts shall apply local law that most closely approximates 781an absolute waiver of all civil liability in connection with the 782Program, unless a warranty or assumption of liability accompanies a 783copy of the Program in return for a fee. 784 785</OL> 786 787 788<H2>1.2 END OF TERMS AND CONDITIONS</H2> 789 790 791<H2>1.3 How to Apply These Terms to Your New Programs</H2> 792 793<P> 794If you develop a new program, and you want it to be of the greatest 795possible use to the public, the best way to achieve this is to make it 796free software which everyone can redistribute and change under these 797terms. 798 799</P> 800<P> 801To do so, attach the following notices to the program. It is safest 802to attach them to the start of each source file to most effectively 803state the exclusion of warranty; and each file should have at least 804the ���copyright��� line and a pointer to where the full notice is found. 805 806</P> 807 808<PRE> 809<VAR>one line to give the program's name and a brief idea of what it does.</VAR> 810Copyright (C) <VAR>year</VAR> <VAR>name of author</VAR> 811 812This program is free software: you can redistribute it and/or modify 813it under the terms of the GNU General Public License as published by 814the Free Software Foundation, either version 3 of the License, or (at 815your option) any later version. 816 817This program is distributed in the hope that it will be useful, but 818WITHOUT ANY WARRANTY; without even the implied warranty of 819MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 820General Public License for more details. 821 822You should have received a copy of the GNU General Public License 823along with this program. If not, see <A HREF="http://www.gnu.org/licenses/">http://www.gnu.org/licenses/</A>. 824</PRE> 825 826<P> 827Also add information on how to contact you by electronic and paper mail. 828 829</P> 830<P> 831If the program does terminal interaction, make it output a short 832notice like this when it starts in an interactive mode: 833 834</P> 835 836<PRE> 837<VAR>program</VAR> Copyright (C) <VAR>year</VAR> <VAR>name of author</VAR> 838This program comes with ABSOLUTELY NO WARRANTY; for details type <SAMP>‘show w’</SAMP>. 839This is free software, and you are welcome to redistribute it 840under certain conditions; type <SAMP>‘show c’</SAMP> for details. 841</PRE> 842 843<P> 844The hypothetical commands <SAMP>‘show w’</SAMP> and <SAMP>‘show c’</SAMP> should show 845the appropriate parts of the General Public License. Of course, your 846program's commands might be different; for a GUI interface, you would 847use an ���about box���. 848 849</P> 850<P> 851You should also get your employer (if you work as a programmer) or school, 852if any, to sign a ���copyright disclaimer��� for the program, if necessary. 853For more information on this, and how to apply and follow the GNU GPL, see 854<A HREF="http://www.gnu.org/licenses/">http://www.gnu.org/licenses/</A>. 855 856</P> 857<P> 858The GNU General Public License does not permit incorporating your 859program into proprietary programs. If your program is a subroutine 860library, you may consider it more useful to permit linking proprietary 861applications with the library. If this is what you want to do, use 862the GNU Lesser General Public License instead of this License. But 863first, please read <A HREF="http://www.gnu.org/philosophy/why-not-lgpl.html">http://www.gnu.org/philosophy/why-not-lgpl.html</A>. 864 865</P> 866 867 868<H1><A NAME="SEC2" HREF="gperf.html#TOC2">Contributors to GNU <CODE>gperf</CODE> Utility</A></H1> 869 870 871<UL> 872<LI> 873 874<A NAME="IDX1"></A> 875The GNU <CODE>gperf</CODE> perfect hash function generator utility was 876written in GNU C++ by Douglas C. Schmidt. The general 877idea for the perfect hash function generator was inspired by Keith 878Bostic's algorithm written in C, and distributed to net.sources around 8791984. The current program is a heavily modified, enhanced, and extended 880implementation of Keith's basic idea, created at the University of 881California, Irvine. Bugs, patches, and suggestions should be reported 882to <CODE><bug-gnu-gperf@gnu.org></CODE>. 883 884<LI> 885 886Special thanks is extended to Michael Tiemann and Doug Lea, for 887providing a useful compiler, and for giving me a forum to exhibit my 888creation. 889 890In addition, Adam de Boor and Nels Olson provided many tips and insights 891that greatly helped improve the quality and functionality of <CODE>gperf</CODE>. 892 893<LI> 894 895Bruno Haible enhanced and optimized the search algorithm. He also rewrote 896the input routines and the output routines for better reliability, and 897added a testsuite. 898</UL> 899 900 901 902<H1><A NAME="SEC3" HREF="gperf.html#TOC3">2 Introduction</A></H1> 903 904<P> 905<CODE>gperf</CODE> is a perfect hash function generator written in C++. It 906transforms an <VAR>n</VAR> element user-specified keyword set <VAR>W</VAR> into a 907perfect hash function <VAR>F</VAR>. <VAR>F</VAR> uniquely maps keywords in 908<VAR>W</VAR> onto the range 0..<VAR>k</VAR>, where <VAR>k</VAR> >= <VAR>n-1</VAR>. If <VAR>k</VAR> 909= <VAR>n-1</VAR> then <VAR>F</VAR> is a <EM>minimal</EM> perfect hash function. 910<CODE>gperf</CODE> generates a 0..<VAR>k</VAR> element static lookup table and a 911pair of C functions. These functions determine whether a given 912character string <VAR>s</VAR> occurs in <VAR>W</VAR>, using at most one probe into 913the lookup table. 914 915</P> 916<P> 917<CODE>gperf</CODE> currently generates the reserved keyword recognizer for 918lexical analyzers in several production and research compilers and 919language processing tools, including GNU C, GNU C++, GNU Java, GNU Pascal, 920GNU Modula 3, and GNU indent. Complete C++ source code for <CODE>gperf</CODE> is 921available from <CODE>http://ftp.gnu.org/pub/gnu/gperf/</CODE>. 922A paper describing <CODE>gperf</CODE>'s design and implementation in greater 923detail is available in the Second USENIX C++ Conference proceedings 924or from <CODE>http://www.cs.wustl.edu/~schmidt/resume.html</CODE>. 925 926</P> 927 928 929<H1><A NAME="SEC4" HREF="gperf.html#TOC4">3 Static search structures and GNU <CODE>gperf</CODE></A></H1> 930<P> 931<A NAME="IDX2"></A> 932 933</P> 934<P> 935A <EM>static search structure</EM> is an Abstract Data Type with certain 936fundamental operations, e.g., <EM>initialize</EM>, <EM>insert</EM>, 937and <EM>retrieve</EM>. Conceptually, all insertions occur before any 938retrievals. In practice, <CODE>gperf</CODE> generates a <EM>static</EM> array 939containing search set keywords and any associated attributes specified 940by the user. Thus, there is essentially no execution-time cost for the 941insertions. It is a useful data structure for representing <EM>static 942search sets</EM>. Static search sets occur frequently in software system 943applications. Typical static search sets include compiler reserved 944words, assembler instruction opcodes, and built-in shell interpreter 945commands. Search set members, called <EM>keywords</EM>, are inserted into 946the structure only once, usually during program initialization, and are 947not generally modified at run-time. 948 949</P> 950<P> 951Numerous static search structure implementations exist, e.g., 952arrays, linked lists, binary search trees, digital search tries, and 953hash tables. Different approaches offer trade-offs between space 954utilization and search time efficiency. For example, an <VAR>n</VAR> element 955sorted array is space efficient, though the average-case time 956complexity for retrieval operations using binary search is 957proportional to log <VAR>n</VAR>. Conversely, hash table implementations 958often locate a table entry in constant time, but typically impose 959additional memory overhead and exhibit poor worst case performance. 960 961</P> 962<P> 963<A NAME="IDX3"></A> 964<EM>Minimal perfect hash functions</EM> provide an optimal solution for a 965particular class of static search sets. A minimal perfect hash 966function is defined by two properties: 967 968</P> 969 970<UL> 971<LI> 972 973It allows keyword recognition in a static search set using at most 974<EM>one</EM> probe into the hash table. This represents the ���perfect��� 975property. 976<LI> 977 978The actual memory allocated to store the keywords is precisely large 979enough for the keyword set, and <EM>no larger</EM>. This is the 980���minimal��� property. 981</UL> 982 983<P> 984For most applications it is far easier to generate <EM>perfect</EM> hash 985functions than <EM>minimal perfect</EM> hash functions. Moreover, 986non-minimal perfect hash functions frequently execute faster than 987minimal ones in practice. This phenomena occurs since searching a 988sparse keyword table increases the probability of locating a ���null��� 989entry, thereby reducing string comparisons. <CODE>gperf</CODE>'s default 990behavior generates <EM>near-minimal</EM> perfect hash functions for 991keyword sets. However, <CODE>gperf</CODE> provides many options that permit 992user control over the degree of minimality and perfection. 993 994</P> 995<P> 996Static search sets often exhibit relative stability over time. For 997example, Ada's 63 reserved words have remained constant for nearly a 998decade. It is therefore frequently worthwhile to expend concerted 999effort building an optimal search structure <EM>once</EM>, if it 1000subsequently receives heavy use multiple times. <CODE>gperf</CODE> removes 1001the drudgery associated with constructing time- and space-efficient 1002search structures by hand. It has proven a useful and practical tool 1003for serious programming projects. Output from <CODE>gperf</CODE> is currently 1004used in several production and research compilers, including GNU C, GNU 1005C++, GNU Java, GNU Pascal, and GNU Modula 3. The latter two compilers are 1006not yet part of the official GNU distribution. Each compiler utilizes 1007<CODE>gperf</CODE> to automatically generate static search structures that 1008efficiently identify their respective reserved keywords. 1009 1010</P> 1011 1012 1013<H1><A NAME="SEC5" HREF="gperf.html#TOC5">4 High-Level Description of GNU <CODE>gperf</CODE></A></H1> 1014 1015<P> 1016The perfect hash function generator <CODE>gperf</CODE> reads a set of 1017���keywords��� from an input file (or from the standard input by 1018default). It attempts to derive a perfect hashing function that 1019recognizes a member of the <EM>static keyword set</EM> with at most a 1020single probe into the lookup table. If <CODE>gperf</CODE> succeeds in 1021generating such a function it produces a pair of C source code routines 1022that perform hashing and table lookup recognition. All generated C code 1023is directed to the standard output. Command-line options described 1024below allow you to modify the input and output format to <CODE>gperf</CODE>. 1025 1026</P> 1027<P> 1028By default, <CODE>gperf</CODE> attempts to produce time-efficient code, with 1029less emphasis on efficient space utilization. However, several options 1030exist that permit trading-off execution time for storage space and vice 1031versa. In particular, expanding the generated table size produces a 1032sparse search structure, generally yielding faster searches. 1033Conversely, you can direct <CODE>gperf</CODE> to utilize a C <CODE>switch</CODE> 1034statement scheme that minimizes data space storage size. Furthermore, 1035using a C <CODE>switch</CODE> may actually speed up the keyword retrieval time 1036somewhat. Actual results depend on your C compiler, of course. 1037 1038</P> 1039<P> 1040In general, <CODE>gperf</CODE> assigns values to the bytes it is using 1041for hashing until some set of values gives each keyword a unique value. 1042A helpful heuristic is that the larger the hash value range, the easier 1043it is for <CODE>gperf</CODE> to find and generate a perfect hash function. 1044Experimentation is the key to getting the most from <CODE>gperf</CODE>. 1045 1046</P> 1047 1048 1049<H2><A NAME="SEC6" HREF="gperf.html#TOC6">4.1 Input Format to <CODE>gperf</CODE></A></H2> 1050<P> 1051<A NAME="IDX4"></A> 1052<A NAME="IDX5"></A> 1053<A NAME="IDX6"></A> 1054<A NAME="IDX7"></A> 1055You can control the input file format by varying certain command-line 1056arguments, in particular the <SAMP>‘-t’</SAMP> option. The input's appearance 1057is similar to GNU utilities <CODE>flex</CODE> and <CODE>bison</CODE> (or UNIX 1058utilities <CODE>lex</CODE> and <CODE>yacc</CODE>). Here's an outline of the general 1059format: 1060 1061</P> 1062 1063<PRE> 1064declarations 1065%% 1066keywords 1067%% 1068functions 1069</PRE> 1070 1071<P> 1072<EM>Unlike</EM> <CODE>flex</CODE> or <CODE>bison</CODE>, the declarations section and 1073the functions section are optional. The following sections describe the 1074input format for each section. 1075 1076</P> 1077 1078<P> 1079It is possible to omit the declaration section entirely, if the <SAMP>‘-t’</SAMP> 1080option is not given. In this case the input file begins directly with the 1081first keyword line, e.g.: 1082 1083</P> 1084 1085<PRE> 1086january 1087february 1088march 1089april 1090... 1091</PRE> 1092 1093 1094 1095<H3><A NAME="SEC7" HREF="gperf.html#TOC7">4.1.1 Declarations</A></H3> 1096 1097<P> 1098The keyword input file optionally contains a section for including 1099arbitrary C declarations and definitions, <CODE>gperf</CODE> declarations that 1100act like command-line options, as well as for providing a user-supplied 1101<CODE>struct</CODE>. 1102 1103</P> 1104 1105 1106 1107<H4><A NAME="SEC8" HREF="gperf.html#TOC8">4.1.1.1 User-supplied <CODE>struct</CODE></A></H4> 1108 1109<P> 1110If the <SAMP>‘-t’</SAMP> option (or, equivalently, the <SAMP>‘%struct-type’</SAMP> declaration) 1111<EM>is</EM> enabled, you <EM>must</EM> provide a C <CODE>struct</CODE> as the last 1112component in the declaration section from the input file. The first 1113field in this struct must be of type <CODE>char *</CODE> or <CODE>const char *</CODE> 1114if the <SAMP>‘-P’</SAMP> option is not given, or of type <CODE>int</CODE> if the option 1115<SAMP>‘-P’</SAMP> (or, equivalently, the <SAMP>‘%pic’</SAMP> declaration) is enabled. 1116This first field must be called <SAMP>‘name’</SAMP>, although it is possible to modify 1117its name with the <SAMP>‘-K’</SAMP> option (or, equivalently, the 1118<SAMP>‘%define slot-name’</SAMP> declaration) described below. 1119 1120</P> 1121<P> 1122Here is a simple example, using months of the year and their attributes as 1123input: 1124 1125</P> 1126 1127<PRE> 1128struct month { char *name; int number; int days; int leap_days; }; 1129%% 1130january, 1, 31, 31 1131february, 2, 28, 29 1132march, 3, 31, 31 1133april, 4, 30, 30 1134may, 5, 31, 31 1135june, 6, 30, 30 1136july, 7, 31, 31 1137august, 8, 31, 31 1138september, 9, 30, 30 1139october, 10, 31, 31 1140november, 11, 30, 30 1141december, 12, 31, 31 1142</PRE> 1143 1144<P> 1145<A NAME="IDX8"></A> 1146Separating the <CODE>struct</CODE> declaration from the list of keywords and 1147other fields are a pair of consecutive percent signs, <SAMP>‘%%’</SAMP>, 1148appearing left justified in the first column, as in the UNIX utility 1149<CODE>lex</CODE>. 1150 1151</P> 1152<P> 1153If the <CODE>struct</CODE> has already been declared in an include file, it can 1154be mentioned in an abbreviated form, like this: 1155 1156</P> 1157 1158<PRE> 1159struct month; 1160%% 1161january, 1, 31, 31 1162... 1163</PRE> 1164 1165 1166 1167<H4><A NAME="SEC9" HREF="gperf.html#TOC9">4.1.1.2 Gperf Declarations</A></H4> 1168 1169<P> 1170The declaration section can contain <CODE>gperf</CODE> declarations. They 1171influence the way <CODE>gperf</CODE> works, like command line options do. 1172In fact, every such declaration is equivalent to a command line option. 1173There are three forms of declarations: 1174 1175</P> 1176 1177<OL> 1178<LI> 1179 1180Declarations without argument, like <SAMP>‘%compare-lengths’</SAMP>. 1181 1182<LI> 1183 1184Declarations with an argument, like <SAMP>‘%switch=<VAR>count</VAR>’</SAMP>. 1185 1186<LI> 1187 1188Declarations of names of entities in the output file, like 1189<SAMP>‘%define lookup-function-name <VAR>name</VAR>’</SAMP>. 1190</OL> 1191 1192<P> 1193When a declaration is given both in the input file and as a command line 1194option, the command-line option's value prevails. 1195 1196</P> 1197<P> 1198The following <CODE>gperf</CODE> declarations are available. 1199 1200</P> 1201<DL COMPACT> 1202 1203<DT><SAMP>‘%delimiters=<VAR>delimiter-list</VAR>’</SAMP> 1204<DD> 1205<A NAME="IDX9"></A> 1206Allows you to provide a string containing delimiters used to 1207separate keywords from their attributes. The default is ",". This 1208option is essential if you want to use keywords that have embedded 1209commas or newlines. 1210 1211<DT><SAMP>‘%struct-type’</SAMP> 1212<DD> 1213<A NAME="IDX10"></A> 1214Allows you to include a <CODE>struct</CODE> type declaration for generated 1215code; see above for an example. 1216 1217<DT><SAMP>‘%ignore-case’</SAMP> 1218<DD> 1219<A NAME="IDX11"></A> 1220Consider upper and lower case ASCII characters as equivalent. The string 1221comparison will use a case insignificant character comparison. Note that 1222locale dependent case mappings are ignored. 1223 1224<DT><SAMP>‘%language=<VAR>language-name</VAR>’</SAMP> 1225<DD> 1226<A NAME="IDX12"></A> 1227Instructs <CODE>gperf</CODE> to generate code in the language specified by the 1228option's argument. Languages handled are currently: 1229 1230<DL COMPACT> 1231 1232<DT><SAMP>‘KR-C’</SAMP> 1233<DD> 1234Old-style K&R C. This language is understood by old-style C compilers and 1235ANSI C compilers, but ANSI C compilers may flag warnings (or even errors) 1236because of lacking <SAMP>‘const’</SAMP>. 1237 1238<DT><SAMP>‘C’</SAMP> 1239<DD> 1240Common C. This language is understood by ANSI C compilers, and also by 1241old-style C compilers, provided that you <CODE>#define const</CODE> to empty 1242for compilers which don't know about this keyword. 1243 1244<DT><SAMP>‘ANSI-C’</SAMP> 1245<DD> 1246ANSI C. This language is understood by ANSI C (C89, ISO C90) compilers, 1247ISO C99 compilers, and C++ compilers. 1248 1249<DT><SAMP>‘C++’</SAMP> 1250<DD> 1251C++. This language is understood by C++ compilers. 1252</DL> 1253 1254The default is C. 1255 1256<DT><SAMP>‘%define slot-name <VAR>name</VAR>’</SAMP> 1257<DD> 1258<A NAME="IDX13"></A> 1259This declaration is only useful when option <SAMP>‘-t’</SAMP> (or, equivalently, the 1260<SAMP>‘%struct-type’</SAMP> declaration) has been given. 1261By default, the program assumes the structure component identifier for 1262the keyword is <SAMP>‘name’</SAMP>. This option allows an arbitrary choice of 1263identifier for this component, although it still must occur as the first 1264field in your supplied <CODE>struct</CODE>. 1265 1266<DT><SAMP>‘%define initializer-suffix <VAR>initializers</VAR>’</SAMP> 1267<DD> 1268<A NAME="IDX14"></A> 1269This declaration is only useful when option <SAMP>‘-t’</SAMP> (or, equivalently, the 1270<SAMP>‘%struct-type’</SAMP> declaration) has been given. 1271It permits to specify initializers for the structure members following 1272<VAR>slot-name</VAR> in empty hash table entries. The list of initializers 1273should start with a comma. By default, the emitted code will 1274zero-initialize structure members following <VAR>slot-name</VAR>. 1275 1276<DT><SAMP>‘%define hash-function-name <VAR>name</VAR>’</SAMP> 1277<DD> 1278<A NAME="IDX15"></A> 1279Allows you to specify the name for the generated hash function. Default 1280name is <SAMP>‘hash’</SAMP>. This option permits the use of two hash tables in 1281the same file. 1282 1283<DT><SAMP>‘%define lookup-function-name <VAR>name</VAR>’</SAMP> 1284<DD> 1285<A NAME="IDX16"></A> 1286Allows you to specify the name for the generated lookup function. 1287Default name is <SAMP>‘in_word_set’</SAMP>. This option permits multiple 1288generated hash functions to be used in the same application. 1289 1290<DT><SAMP>‘%define class-name <VAR>name</VAR>’</SAMP> 1291<DD> 1292<A NAME="IDX17"></A> 1293This option is only useful when option <SAMP>‘-L C++’</SAMP> (or, equivalently, 1294the <SAMP>‘%language=C++’</SAMP> declaration) has been given. It 1295allows you to specify the name of generated C++ class. Default name is 1296<CODE>Perfect_Hash</CODE>. 1297 1298<DT><SAMP>‘%7bit’</SAMP> 1299<DD> 1300<A NAME="IDX18"></A> 1301This option specifies that all strings that will be passed as arguments 1302to the generated hash function and the generated lookup function will 1303solely consist of 7-bit ASCII characters (bytes in the range 0..127). 1304(Note that the ANSI C functions <CODE>isalnum</CODE> and <CODE>isgraph</CODE> do 1305<EM>not</EM> guarantee that a byte is in this range. Only an explicit 1306test like <SAMP>‘c >= 'A' && c <= 'Z'’</SAMP> guarantees this.) 1307 1308<DT><SAMP>‘%compare-lengths’</SAMP> 1309<DD> 1310<A NAME="IDX19"></A> 1311Compare keyword lengths before trying a string comparison. This option 1312is mandatory for binary comparisons (see section <A HREF="gperf.html#SEC15">4.3 Use of NUL bytes</A>). It also might 1313cut down on the number of string comparisons made during the lookup, since 1314keywords with different lengths are never compared via <CODE>strcmp</CODE>. 1315However, using <SAMP>‘%compare-lengths’</SAMP> might greatly increase the size of the 1316generated C code if the lookup table range is large (which implies that 1317the switch option <SAMP>‘-S’</SAMP> or <SAMP>‘%switch’</SAMP> is not enabled), since the length 1318table contains as many elements as there are entries in the lookup table. 1319 1320<DT><SAMP>‘%compare-strncmp’</SAMP> 1321<DD> 1322<A NAME="IDX20"></A> 1323Generates C code that uses the <CODE>strncmp</CODE> function to perform 1324string comparisons. The default action is to use <CODE>strcmp</CODE>. 1325 1326<DT><SAMP>‘%readonly-tables’</SAMP> 1327<DD> 1328<A NAME="IDX21"></A> 1329Makes the contents of all generated lookup tables constant, i.e., 1330���readonly���. Many compilers can generate more efficient code for this 1331by putting the tables in readonly memory. 1332 1333<DT><SAMP>‘%enum’</SAMP> 1334<DD> 1335<A NAME="IDX22"></A> 1336Define constant values using an enum local to the lookup function rather 1337than with #defines. This also means that different lookup functions can 1338reside in the same file. Thanks to James Clark <CODE><jjc@ai.mit.edu></CODE>. 1339 1340<DT><SAMP>‘%includes’</SAMP> 1341<DD> 1342<A NAME="IDX23"></A> 1343Include the necessary system include file, <CODE><string.h></CODE>, at the 1344beginning of the code. By default, this is not done; the user must 1345include this header file himself to allow compilation of the code. 1346 1347<DT><SAMP>‘%global-table’</SAMP> 1348<DD> 1349<A NAME="IDX24"></A> 1350Generate the static table of keywords as a static global variable, 1351rather than hiding it inside of the lookup function (which is the 1352default behavior). 1353 1354<DT><SAMP>‘%pic’</SAMP> 1355<DD> 1356<A NAME="IDX25"></A> 1357Optimize the generated table for inclusion in shared libraries. This 1358reduces the startup time of programs using a shared library containing 1359the generated code. If the <SAMP>‘%struct-type’</SAMP> declaration (or, 1360equivalently, the option <SAMP>‘-t’</SAMP>) is also given, the first field of the 1361user-defined struct must be of type <SAMP>‘int’</SAMP>, not <SAMP>‘char *’</SAMP>, because 1362it will contain offsets into the string pool instead of actual strings. 1363To convert such an offset to a string, you can use the expression 1364<SAMP>‘stringpool + <VAR>o</VAR>’</SAMP>, where <VAR>o</VAR> is the offset. The string pool 1365name can be changed through the <SAMP>‘%define string-pool-name’</SAMP> declaration. 1366 1367<DT><SAMP>‘%define string-pool-name <VAR>name</VAR>’</SAMP> 1368<DD> 1369<A NAME="IDX26"></A> 1370Allows you to specify the name of the generated string pool created by 1371the declaration <SAMP>‘%pic’</SAMP> (or, equivalently, the option <SAMP>‘-P’</SAMP>). 1372The default name is <SAMP>‘stringpool’</SAMP>. This declaration permits the use of 1373two hash tables in the same file, with <SAMP>‘%pic’</SAMP> and even when the 1374<SAMP>‘%global-table’</SAMP> declaration (or, equivalently, the option <SAMP>‘-G’</SAMP>) 1375is given. 1376 1377<DT><SAMP>‘%null-strings’</SAMP> 1378<DD> 1379<A NAME="IDX27"></A> 1380Use NULL strings instead of empty strings for empty keyword table entries. 1381This reduces the startup time of programs using a shared library containing 1382the generated code (but not as much as the declaration <SAMP>‘%pic’</SAMP>), at the 1383expense of one more test-and-branch instruction at run time. 1384 1385<DT><SAMP>‘%define word-array-name <VAR>name</VAR>’</SAMP> 1386<DD> 1387<A NAME="IDX28"></A> 1388Allows you to specify the name for the generated array containing the 1389hash table. Default name is <SAMP>‘wordlist’</SAMP>. This option permits the 1390use of two hash tables in the same file, even when the option <SAMP>‘-G’</SAMP> 1391(or, equivalently, the <SAMP>‘%global-table’</SAMP> declaration) is given. 1392 1393<DT><SAMP>‘%define length-table-name <VAR>name</VAR>’</SAMP> 1394<DD> 1395<A NAME="IDX29"></A> 1396Allows you to specify the name for the generated array containing the 1397length table. Default name is <SAMP>‘lengthtable’</SAMP>. This option permits the 1398use of two length tables in the same file, even when the option <SAMP>‘-G’</SAMP> 1399(or, equivalently, the <SAMP>‘%global-table’</SAMP> declaration) is given. 1400 1401<DT><SAMP>‘%switch=<VAR>count</VAR>’</SAMP> 1402<DD> 1403<A NAME="IDX30"></A> 1404Causes the generated C code to use a <CODE>switch</CODE> statement scheme, 1405rather than an array lookup table. This can lead to a reduction in both 1406time and space requirements for some input files. The argument to this 1407option determines how many <CODE>switch</CODE> statements are generated. A 1408value of 1 generates 1 <CODE>switch</CODE> containing all the elements, a 1409value of 2 generates 2 tables with 1/2 the elements in each 1410<CODE>switch</CODE>, etc. This is useful since many C compilers cannot 1411correctly generate code for large <CODE>switch</CODE> statements. This option 1412was inspired in part by Keith Bostic's original C program. 1413 1414<DT><SAMP>‘%omit-struct-type’</SAMP> 1415<DD> 1416<A NAME="IDX31"></A> 1417Prevents the transfer of the type declaration to the output file. Use 1418this option if the type is already defined elsewhere. 1419</DL> 1420 1421 1422 1423<H4><A NAME="SEC10" HREF="gperf.html#TOC10">4.1.1.3 C Code Inclusion</A></H4> 1424 1425<P> 1426<A NAME="IDX32"></A> 1427<A NAME="IDX33"></A> 1428Using a syntax similar to GNU utilities <CODE>flex</CODE> and <CODE>bison</CODE>, it 1429is possible to directly include C source text and comments verbatim into 1430the generated output file. This is accomplished by enclosing the region 1431inside left-justified surrounding <SAMP>‘%{’</SAMP>, <SAMP>‘%}’</SAMP> pairs. Here is 1432an input fragment based on the previous example that illustrates this 1433feature: 1434 1435</P> 1436 1437<PRE> 1438%{ 1439#include <assert.h> 1440/* This section of code is inserted directly into the output. */ 1441int return_month_days (struct month *months, int is_leap_year); 1442%} 1443struct month { char *name; int number; int days; int leap_days; }; 1444%% 1445january, 1, 31, 31 1446february, 2, 28, 29 1447march, 3, 31, 31 1448... 1449</PRE> 1450 1451 1452 1453<H3><A NAME="SEC11" HREF="gperf.html#TOC11">4.1.2 Format for Keyword Entries</A></H3> 1454 1455<P> 1456The second input file format section contains lines of keywords and any 1457associated attributes you might supply. A line beginning with <SAMP>‘#’</SAMP> 1458in the first column is considered a comment. Everything following the 1459<SAMP>‘#’</SAMP> is ignored, up to and including the following newline. A line 1460beginning with <SAMP>‘%’</SAMP> in the first column is an option declaration and 1461must not occur within the keywords section. 1462 1463</P> 1464<P> 1465The first field of each non-comment line is always the keyword itself. It 1466can be given in two ways: as a simple name, i.e., without surrounding 1467string quotation marks, or as a string enclosed in double-quotes, in 1468C syntax, possibly with backslash escapes like <CODE>\"</CODE> or <CODE>\234</CODE> 1469or <CODE>\xa8</CODE>. In either case, it must start right at the beginning 1470of the line, without leading whitespace. 1471In this context, a ���field��� is considered to extend up to, but 1472not include, the first blank, comma, or newline. Here is a simple 1473example taken from a partial list of C reserved words: 1474 1475</P> 1476 1477<PRE> 1478# These are a few C reserved words, see the c.gperf file 1479# for a complete list of ANSI C reserved words. 1480unsigned 1481sizeof 1482switch 1483signed 1484if 1485default 1486for 1487while 1488return 1489</PRE> 1490 1491<P> 1492Note that unlike <CODE>flex</CODE> or <CODE>bison</CODE> the first <SAMP>‘%%’</SAMP> marker 1493may be elided if the declaration section is empty. 1494 1495</P> 1496<P> 1497Additional fields may optionally follow the leading keyword. Fields 1498should be separated by commas, and terminate at the end of line. What 1499these fields mean is entirely up to you; they are used to initialize the 1500elements of the user-defined <CODE>struct</CODE> provided by you in the 1501declaration section. If the <SAMP>‘-t’</SAMP> option (or, equivalently, the 1502<SAMP>‘%struct-type’</SAMP> declaration) is <EM>not</EM> enabled 1503these fields are simply ignored. All previous examples except the last 1504one contain keyword attributes. 1505 1506</P> 1507 1508 1509<H3><A NAME="SEC12" HREF="gperf.html#TOC12">4.1.3 Including Additional C Functions</A></H3> 1510 1511<P> 1512The optional third section also corresponds closely with conventions 1513found in <CODE>flex</CODE> and <CODE>bison</CODE>. All text in this section, 1514starting at the final <SAMP>‘%%’</SAMP> and extending to the end of the input 1515file, is included verbatim into the generated output file. Naturally, 1516it is your responsibility to ensure that the code contained in this 1517section is valid C. 1518 1519</P> 1520 1521 1522<H3><A NAME="SEC13" HREF="gperf.html#TOC13">4.1.4 Where to place directives for GNU <CODE>indent</CODE>.</A></H3> 1523 1524<P> 1525If you want to invoke GNU <CODE>indent</CODE> on a <CODE>gperf</CODE> input file, 1526you will see that GNU <CODE>indent</CODE> doesn't understand the <SAMP>‘%%’</SAMP>, 1527<SAMP>‘%{’</SAMP> and <SAMP>‘%}’</SAMP> directives that control <CODE>gperf</CODE>'s 1528interpretation of the input file. Therefore you have to insert some 1529directives for GNU <CODE>indent</CODE>. More precisely, assuming the most 1530general input file structure 1531 1532</P> 1533 1534<PRE> 1535declarations part 1 1536%{ 1537verbatim code 1538%} 1539declarations part 2 1540%% 1541keywords 1542%% 1543functions 1544</PRE> 1545 1546<P> 1547you would insert <SAMP>‘*INDENT-OFF*’</SAMP> and <SAMP>‘*INDENT-ON*’</SAMP> comments 1548as follows: 1549 1550</P> 1551 1552<PRE> 1553/* *INDENT-OFF* */ 1554declarations part 1 1555%{ 1556/* *INDENT-ON* */ 1557verbatim code 1558/* *INDENT-OFF* */ 1559%} 1560declarations part 2 1561%% 1562keywords 1563%% 1564/* *INDENT-ON* */ 1565functions 1566</PRE> 1567 1568 1569 1570<H2><A NAME="SEC14" HREF="gperf.html#TOC14">4.2 Output Format for Generated C Code with <CODE>gperf</CODE></A></H2> 1571<P> 1572<A NAME="IDX34"></A> 1573 1574</P> 1575<P> 1576Several options control how the generated C code appears on the standard 1577output. Two C functions are generated. They are called <CODE>hash</CODE> and 1578<CODE>in_word_set</CODE>, although you may modify their names with a command-line 1579option. Both functions require two arguments, a string, <CODE>char *</CODE> 1580<VAR>str</VAR>, and a length parameter, <CODE>int</CODE> <VAR>len</VAR>. Their default 1581function prototypes are as follows: 1582 1583</P> 1584<P> 1585<DL> 1586<DT><U>Function:</U> unsigned int <B>hash</B> <I>(const char * <VAR>str</VAR>, unsigned int <VAR>len</VAR>)</I> 1587<DD><A NAME="IDX35"></A> 1588By default, the generated <CODE>hash</CODE> function returns an integer value 1589created by adding <VAR>len</VAR> to several user-specified <VAR>str</VAR> byte 1590positions indexed into an <EM>associated values</EM> table stored in a 1591local static array. The associated values table is constructed 1592internally by <CODE>gperf</CODE> and later output as a static local C array 1593called <SAMP>‘hash_table’</SAMP>. The relevant selected positions (i.e. indices 1594into <VAR>str</VAR>) are specified via the <SAMP>‘-k’</SAMP> option when running 1595<CODE>gperf</CODE>, as detailed in the <EM>Options</EM> section below (see section <A HREF="gperf.html#SEC17">5 Invoking <CODE>gperf</CODE></A>). 1596</DL> 1597 1598</P> 1599<P> 1600<DL> 1601<DT><U>Function:</U> <B>in_word_set</B> <I>(const char * <VAR>str</VAR>, unsigned int <VAR>len</VAR>)</I> 1602<DD><A NAME="IDX36"></A> 1603If <VAR>str</VAR> is in the keyword set, returns a pointer to that 1604keyword. More exactly, if the option <SAMP>‘-t’</SAMP> (or, equivalently, the 1605<SAMP>‘%struct-type’</SAMP> declaration) was given, it returns 1606a pointer to the matching keyword's structure. Otherwise it returns 1607<CODE>NULL</CODE>. 1608</DL> 1609 1610</P> 1611<P> 1612If the option <SAMP>‘-c’</SAMP> (or, equivalently, the <SAMP>‘%compare-strncmp’</SAMP> 1613declaration) is not used, <VAR>str</VAR> must be a NUL terminated 1614string of exactly length <VAR>len</VAR>. If <SAMP>‘-c’</SAMP> (or, equivalently, the 1615<SAMP>‘%compare-strncmp’</SAMP> declaration) is used, <VAR>str</VAR> must 1616simply be an array of <VAR>len</VAR> bytes and does not need to be NUL 1617terminated. 1618 1619</P> 1620<P> 1621The code generated for these two functions is affected by the following 1622options: 1623 1624</P> 1625<DL COMPACT> 1626 1627<DT><SAMP>‘-t’</SAMP> 1628<DD> 1629<DT><SAMP>‘--struct-type’</SAMP> 1630<DD> 1631Make use of the user-defined <CODE>struct</CODE>. 1632 1633<DT><SAMP>‘-S <VAR>total-switch-statements</VAR>’</SAMP> 1634<DD> 1635<DT><SAMP>‘--switch=<VAR>total-switch-statements</VAR>’</SAMP> 1636<DD> 1637<A NAME="IDX37"></A> 1638Generate 1 or more C <CODE>switch</CODE> statement rather than use a large, 1639(and potentially sparse) static array. Although the exact time and 1640space savings of this approach vary according to your C compiler's 1641degree of optimization, this method often results in smaller and faster 1642code. 1643</DL> 1644 1645<P> 1646If the <SAMP>‘-t’</SAMP> and <SAMP>‘-S’</SAMP> options (or, equivalently, the 1647<SAMP>‘%struct-type’</SAMP> and <SAMP>‘%switch’</SAMP> declarations) are omitted, the default 1648action 1649is to generate a <CODE>char *</CODE> array containing the keywords, together with 1650additional empty strings used for padding the array. By experimenting 1651with the various input and output options, and timing the resulting C 1652code, you can determine the best option choices for different keyword 1653set characteristics. 1654 1655</P> 1656 1657 1658<H2><A NAME="SEC15" HREF="gperf.html#TOC15">4.3 Use of NUL bytes</A></H2> 1659<P> 1660<A NAME="IDX38"></A> 1661 1662</P> 1663<P> 1664By default, the code generated by <CODE>gperf</CODE> operates on zero 1665terminated strings, the usual representation of strings in C. This means 1666that the keywords in the input file must not contain NUL bytes, 1667and the <VAR>str</VAR> argument passed to <CODE>hash</CODE> or <CODE>in_word_set</CODE> 1668must be NUL terminated and have exactly length <VAR>len</VAR>. 1669 1670</P> 1671<P> 1672If option <SAMP>‘-c’</SAMP> (or, equivalently, the <SAMP>‘%compare-strncmp’</SAMP> 1673declaration) is used, then the <VAR>str</VAR> argument does not need 1674to be NUL terminated. The code generated by <CODE>gperf</CODE> will only 1675access the first <VAR>len</VAR>, not <VAR>len+1</VAR>, bytes starting at <VAR>str</VAR>. 1676However, the keywords in the input file still must not contain NUL 1677bytes. 1678 1679</P> 1680<P> 1681If option <SAMP>‘-l’</SAMP> (or, equivalently, the <SAMP>‘%compare-lengths’</SAMP> 1682declaration) is used, then the hash table performs binary 1683comparison. The keywords in the input file may contain NUL bytes, 1684written in string syntax as <CODE>\000</CODE> or <CODE>\x00</CODE>, and the code 1685generated by <CODE>gperf</CODE> will treat NUL like any other byte. 1686Also, in this case the <SAMP>‘-c’</SAMP> option (or, equivalently, the 1687<SAMP>‘%compare-strncmp’</SAMP> declaration) is ignored. 1688 1689</P> 1690 1691 1692<H2><A NAME="SEC16" HREF="gperf.html#TOC16">4.4 The Copyright of the Output</A></H2> 1693<P> 1694<A NAME="IDX39"></A> 1695 1696</P> 1697<P> 1698<CODE>gperf</CODE> is under GPL, but that does not cause the output produced 1699by <CODE>gperf</CODE> to be under GPL. The reason is that the output contains 1700only small pieces of text that come directly from <CODE>gperf</CODE>'s source 1701code -- only about 7 lines long, too small for being significant --, and 1702therefore the output is not a ���work based on <CODE>gperf</CODE>��� (in the 1703sense of the GPL version 3). 1704 1705</P> 1706<P> 1707On the other hand, the output produced by <CODE>gperf</CODE> contains 1708essentially all of the input file. Therefore the output is a 1709���derivative work��� of the input (in the sense of U.S. copyright law); 1710and its copyright status depends on the copyright of the input. For most 1711software licenses, the result is that the the output is under the same 1712license, with the same copyright holder, as the input that was passed to 1713<CODE>gperf</CODE>. 1714 1715</P> 1716 1717 1718<H1><A NAME="SEC17" HREF="gperf.html#TOC17">5 Invoking <CODE>gperf</CODE></A></H1> 1719 1720<P> 1721There are <EM>many</EM> options to <CODE>gperf</CODE>. They were added to make 1722the program more convenient for use with real applications. ���On-line��� 1723help is readily available via the <SAMP>‘--help’</SAMP> option. Here is the 1724complete list of options. 1725 1726</P> 1727 1728 1729 1730<H2><A NAME="SEC18" HREF="gperf.html#TOC18">5.1 Specifying the Location of the Output File</A></H2> 1731 1732<DL COMPACT> 1733 1734<DT><SAMP>‘--output-file=<VAR>file</VAR>’</SAMP> 1735<DD> 1736Allows you to specify the name of the file to which the output is written to. 1737</DL> 1738 1739<P> 1740The results are written to standard output if no output file is specified 1741or if it is <SAMP>‘-’</SAMP>. 1742 1743</P> 1744 1745 1746<H2><A NAME="SEC19" HREF="gperf.html#TOC19">5.2 Options that affect Interpretation of the Input File</A></H2> 1747 1748<P> 1749These options are also available as declarations in the input file 1750(see section <A HREF="gperf.html#SEC9">4.1.1.2 Gperf Declarations</A>). 1751 1752</P> 1753<DL COMPACT> 1754 1755<DT><SAMP>‘-e <VAR>keyword-delimiter-list</VAR>’</SAMP> 1756<DD> 1757<DT><SAMP>‘--delimiters=<VAR>keyword-delimiter-list</VAR>’</SAMP> 1758<DD> 1759<A NAME="IDX40"></A> 1760Allows you to provide a string containing delimiters used to 1761separate keywords from their attributes. The default is ",". This 1762option is essential if you want to use keywords that have embedded 1763commas or newlines. One useful trick is to use -e'TAB', where TAB is 1764the literal tab character. 1765 1766<DT><SAMP>‘-t’</SAMP> 1767<DD> 1768<DT><SAMP>‘--struct-type’</SAMP> 1769<DD> 1770Allows you to include a <CODE>struct</CODE> type declaration for generated 1771code. Any text before a pair of consecutive <SAMP>‘%%’</SAMP> is considered 1772part of the type declaration. Keywords and additional fields may follow 1773this, one group of fields per line. A set of examples for generating 1774perfect hash tables and functions for Ada, C, C++, Pascal, Modula 2, 1775Modula 3 and JavaScript reserved words are distributed with this release. 1776 1777<DT><SAMP>‘--ignore-case’</SAMP> 1778<DD> 1779Consider upper and lower case ASCII characters as equivalent. The string 1780comparison will use a case insignificant character comparison. Note that 1781locale dependent case mappings are ignored. This option is therefore not 1782suitable if a properly internationalized or locale aware case mapping 1783should be used. (For example, in a Turkish locale, the upper case equivalent 1784of the lowercase ASCII letter <SAMP>‘i’</SAMP> is the non-ASCII character 1785<SAMP>‘capital i with dot above’</SAMP>.) For this case, it is better to apply 1786an uppercase or lowercase conversion on the string before passing it to 1787the <CODE>gperf</CODE> generated function. 1788</DL> 1789 1790 1791 1792<H2><A NAME="SEC20" HREF="gperf.html#TOC20">5.3 Options to specify the Language for the Output Code</A></H2> 1793 1794<P> 1795These options are also available as declarations in the input file 1796(see section <A HREF="gperf.html#SEC9">4.1.1.2 Gperf Declarations</A>). 1797 1798</P> 1799<DL COMPACT> 1800 1801<DT><SAMP>‘-L <VAR>generated-language-name</VAR>’</SAMP> 1802<DD> 1803<DT><SAMP>‘--language=<VAR>generated-language-name</VAR>’</SAMP> 1804<DD> 1805Instructs <CODE>gperf</CODE> to generate code in the language specified by the 1806option's argument. Languages handled are currently: 1807 1808<DL COMPACT> 1809 1810<DT><SAMP>‘KR-C’</SAMP> 1811<DD> 1812Old-style K&R C. This language is understood by old-style C compilers and 1813ANSI C compilers, but ANSI C compilers may flag warnings (or even errors) 1814because of lacking <SAMP>‘const’</SAMP>. 1815 1816<DT><SAMP>‘C’</SAMP> 1817<DD> 1818Common C. This language is understood by ANSI C compilers, and also by 1819old-style C compilers, provided that you <CODE>#define const</CODE> to empty 1820for compilers which don't know about this keyword. 1821 1822<DT><SAMP>‘ANSI-C’</SAMP> 1823<DD> 1824ANSI C. This language is understood by ANSI C compilers and C++ compilers. 1825 1826<DT><SAMP>‘C++’</SAMP> 1827<DD> 1828C++. This language is understood by C++ compilers. 1829</DL> 1830 1831The default is C. 1832 1833<DT><SAMP>‘-a’</SAMP> 1834<DD> 1835This option is supported for compatibility with previous releases of 1836<CODE>gperf</CODE>. It does not do anything. 1837 1838<DT><SAMP>‘-g’</SAMP> 1839<DD> 1840This option is supported for compatibility with previous releases of 1841<CODE>gperf</CODE>. It does not do anything. 1842</DL> 1843 1844 1845 1846<H2><A NAME="SEC21" HREF="gperf.html#TOC21">5.4 Options for fine tuning Details in the Output Code</A></H2> 1847 1848<P> 1849Most of these options are also available as declarations in the input file 1850(see section <A HREF="gperf.html#SEC9">4.1.1.2 Gperf Declarations</A>). 1851 1852</P> 1853<DL COMPACT> 1854 1855<DT><SAMP>‘-K <VAR>slot-name</VAR>’</SAMP> 1856<DD> 1857<DT><SAMP>‘--slot-name=<VAR>slot-name</VAR>’</SAMP> 1858<DD> 1859<A NAME="IDX41"></A> 1860This option is only useful when option <SAMP>‘-t’</SAMP> (or, equivalently, the 1861<SAMP>‘%struct-type’</SAMP> declaration) has been given. 1862By default, the program assumes the structure component identifier for 1863the keyword is <SAMP>‘name’</SAMP>. This option allows an arbitrary choice of 1864identifier for this component, although it still must occur as the first 1865field in your supplied <CODE>struct</CODE>. 1866 1867<DT><SAMP>‘-F <VAR>initializers</VAR>’</SAMP> 1868<DD> 1869<DT><SAMP>‘--initializer-suffix=<VAR>initializers</VAR>’</SAMP> 1870<DD> 1871<A NAME="IDX42"></A> 1872This option is only useful when option <SAMP>‘-t’</SAMP> (or, equivalently, the 1873<SAMP>‘%struct-type’</SAMP> declaration) has been given. 1874It permits to specify initializers for the structure members following 1875<VAR>slot-name</VAR> in empty hash table entries. The list of initializers 1876should start with a comma. By default, the emitted code will 1877zero-initialize structure members following <VAR>slot-name</VAR>. 1878 1879<DT><SAMP>‘-H <VAR>hash-function-name</VAR>’</SAMP> 1880<DD> 1881<DT><SAMP>‘--hash-function-name=<VAR>hash-function-name</VAR>’</SAMP> 1882<DD> 1883Allows you to specify the name for the generated hash function. Default 1884name is <SAMP>‘hash’</SAMP>. This option permits the use of two hash tables in 1885the same file. 1886 1887<DT><SAMP>‘-N <VAR>lookup-function-name</VAR>’</SAMP> 1888<DD> 1889<DT><SAMP>‘--lookup-function-name=<VAR>lookup-function-name</VAR>’</SAMP> 1890<DD> 1891Allows you to specify the name for the generated lookup function. 1892Default name is <SAMP>‘in_word_set’</SAMP>. This option permits multiple 1893generated hash functions to be used in the same application. 1894 1895<DT><SAMP>‘-Z <VAR>class-name</VAR>’</SAMP> 1896<DD> 1897<DT><SAMP>‘--class-name=<VAR>class-name</VAR>’</SAMP> 1898<DD> 1899<A NAME="IDX43"></A> 1900This option is only useful when option <SAMP>‘-L C++’</SAMP> (or, equivalently, 1901the <SAMP>‘%language=C++’</SAMP> declaration) has been given. It 1902allows you to specify the name of generated C++ class. Default name is 1903<CODE>Perfect_Hash</CODE>. 1904 1905<DT><SAMP>‘-7’</SAMP> 1906<DD> 1907<DT><SAMP>‘--seven-bit’</SAMP> 1908<DD> 1909This option specifies that all strings that will be passed as arguments 1910to the generated hash function and the generated lookup function will 1911solely consist of 7-bit ASCII characters (bytes in the range 0..127). 1912(Note that the ANSI C functions <CODE>isalnum</CODE> and <CODE>isgraph</CODE> do 1913<EM>not</EM> guarantee that a byte is in this range. Only an explicit 1914test like <SAMP>‘c >= 'A' && c <= 'Z'’</SAMP> guarantees this.) This was the 1915default in versions of <CODE>gperf</CODE> earlier than 2.7; now the default is 1916to support 8-bit and multibyte characters. 1917 1918<DT><SAMP>‘-l’</SAMP> 1919<DD> 1920<DT><SAMP>‘--compare-lengths’</SAMP> 1921<DD> 1922Compare keyword lengths before trying a string comparison. This option 1923is mandatory for binary comparisons (see section <A HREF="gperf.html#SEC15">4.3 Use of NUL bytes</A>). It also might 1924cut down on the number of string comparisons made during the lookup, since 1925keywords with different lengths are never compared via <CODE>strcmp</CODE>. 1926However, using <SAMP>‘-l’</SAMP> might greatly increase the size of the 1927generated C code if the lookup table range is large (which implies that 1928the switch option <SAMP>‘-S’</SAMP> or <SAMP>‘%switch’</SAMP> is not enabled), since the length 1929table contains as many elements as there are entries in the lookup table. 1930 1931<DT><SAMP>‘-c’</SAMP> 1932<DD> 1933<DT><SAMP>‘--compare-strncmp’</SAMP> 1934<DD> 1935Generates C code that uses the <CODE>strncmp</CODE> function to perform 1936string comparisons. The default action is to use <CODE>strcmp</CODE>. 1937 1938<DT><SAMP>‘-C’</SAMP> 1939<DD> 1940<DT><SAMP>‘--readonly-tables’</SAMP> 1941<DD> 1942Makes the contents of all generated lookup tables constant, i.e., 1943���readonly���. Many compilers can generate more efficient code for this 1944by putting the tables in readonly memory. 1945 1946<DT><SAMP>‘-E’</SAMP> 1947<DD> 1948<DT><SAMP>‘--enum’</SAMP> 1949<DD> 1950Define constant values using an enum local to the lookup function rather 1951than with #defines. This also means that different lookup functions can 1952reside in the same file. Thanks to James Clark <CODE><jjc@ai.mit.edu></CODE>. 1953 1954<DT><SAMP>‘-I’</SAMP> 1955<DD> 1956<DT><SAMP>‘--includes’</SAMP> 1957<DD> 1958Include the necessary system include file, <CODE><string.h></CODE>, at the 1959beginning of the code. By default, this is not done; the user must 1960include this header file himself to allow compilation of the code. 1961 1962<DT><SAMP>‘-G’</SAMP> 1963<DD> 1964<DT><SAMP>‘--global-table’</SAMP> 1965<DD> 1966Generate the static table of keywords as a static global variable, 1967rather than hiding it inside of the lookup function (which is the 1968default behavior). 1969 1970<DT><SAMP>‘-P’</SAMP> 1971<DD> 1972<DT><SAMP>‘--pic’</SAMP> 1973<DD> 1974Optimize the generated table for inclusion in shared libraries. This 1975reduces the startup time of programs using a shared library containing 1976the generated code. If the option <SAMP>‘-t’</SAMP> (or, equivalently, the 1977<SAMP>‘%struct-type’</SAMP> declaration) is also given, the first field of the 1978user-defined struct must be of type <SAMP>‘int’</SAMP>, not <SAMP>‘char *’</SAMP>, because 1979it will contain offsets into the string pool instead of actual strings. 1980To convert such an offset to a string, you can use the expression 1981<SAMP>‘stringpool + <VAR>o</VAR>’</SAMP>, where <VAR>o</VAR> is the offset. The string pool 1982name can be changed through the option <SAMP>‘--string-pool-name’</SAMP>. 1983 1984<DT><SAMP>‘-Q <VAR>string-pool-name</VAR>’</SAMP> 1985<DD> 1986<DT><SAMP>‘--string-pool-name=<VAR>string-pool-name</VAR>’</SAMP> 1987<DD> 1988Allows you to specify the name of the generated string pool created by 1989option <SAMP>‘-P’</SAMP>. The default name is <SAMP>‘stringpool’</SAMP>. This option 1990permits the use of two hash tables in the same file, with <SAMP>‘-P’</SAMP> and 1991even when the option <SAMP>‘-G’</SAMP> (or, equivalently, the <SAMP>‘%global-table’</SAMP> 1992declaration) is given. 1993 1994<DT><SAMP>‘--null-strings’</SAMP> 1995<DD> 1996Use NULL strings instead of empty strings for empty keyword table entries. 1997This reduces the startup time of programs using a shared library containing 1998the generated code (but not as much as option <SAMP>‘-P’</SAMP>), at the expense 1999of one more test-and-branch instruction at run time. 2000 2001<DT><SAMP>‘-W <VAR>hash-table-array-name</VAR>’</SAMP> 2002<DD> 2003<DT><SAMP>‘--word-array-name=<VAR>hash-table-array-name</VAR>’</SAMP> 2004<DD> 2005<A NAME="IDX44"></A> 2006Allows you to specify the name for the generated array containing the 2007hash table. Default name is <SAMP>‘wordlist’</SAMP>. This option permits the 2008use of two hash tables in the same file, even when the option <SAMP>‘-G’</SAMP> 2009(or, equivalently, the <SAMP>‘%global-table’</SAMP> declaration) is given. 2010 2011<DT><SAMP>‘--length-table-name=<VAR>length-table-array-name</VAR>’</SAMP> 2012<DD> 2013<A NAME="IDX45"></A> 2014Allows you to specify the name for the generated array containing the 2015length table. Default name is <SAMP>‘lengthtable’</SAMP>. This option permits the 2016use of two length tables in the same file, even when the option <SAMP>‘-G’</SAMP> 2017(or, equivalently, the <SAMP>‘%global-table’</SAMP> declaration) is given. 2018 2019<DT><SAMP>‘-S <VAR>total-switch-statements</VAR>’</SAMP> 2020<DD> 2021<DT><SAMP>‘--switch=<VAR>total-switch-statements</VAR>’</SAMP> 2022<DD> 2023<A NAME="IDX46"></A> 2024Causes the generated C code to use a <CODE>switch</CODE> statement scheme, 2025rather than an array lookup table. This can lead to a reduction in both 2026time and space requirements for some input files. The argument to this 2027option determines how many <CODE>switch</CODE> statements are generated. A 2028value of 1 generates 1 <CODE>switch</CODE> containing all the elements, a 2029value of 2 generates 2 tables with 1/2 the elements in each 2030<CODE>switch</CODE>, etc. This is useful since many C compilers cannot 2031correctly generate code for large <CODE>switch</CODE> statements. This option 2032was inspired in part by Keith Bostic's original C program. 2033 2034<DT><SAMP>‘-T’</SAMP> 2035<DD> 2036<DT><SAMP>‘--omit-struct-type’</SAMP> 2037<DD> 2038Prevents the transfer of the type declaration to the output file. Use 2039this option if the type is already defined elsewhere. 2040 2041<DT><SAMP>‘-p’</SAMP> 2042<DD> 2043This option is supported for compatibility with previous releases of 2044<CODE>gperf</CODE>. It does not do anything. 2045</DL> 2046 2047 2048 2049<H2><A NAME="SEC22" HREF="gperf.html#TOC22">5.5 Options for changing the Algorithms employed by <CODE>gperf</CODE></A></H2> 2050 2051<DL COMPACT> 2052 2053<DT><SAMP>‘-k <VAR>selected-byte-positions</VAR>’</SAMP> 2054<DD> 2055<DT><SAMP>‘--key-positions=<VAR>selected-byte-positions</VAR>’</SAMP> 2056<DD> 2057Allows selection of the byte positions used in the keywords' 2058hash function. The allowable choices range between 1-255, inclusive. 2059The positions are separated by commas, e.g., <SAMP>‘-k 9,4,13,14’</SAMP>; 2060ranges may be used, e.g., <SAMP>‘-k 2-7’</SAMP>; and positions may occur 2061in any order. Furthermore, the wildcard '*' causes the generated 2062hash function to consider <STRONG>all</STRONG> byte positions in each keyword, 2063whereas '$' instructs the hash function to use the ���final byte��� 2064of a keyword (this is the only way to use a byte position greater than 2065255, incidentally). 2066 2067For instance, the option <SAMP>‘-k 1,2,4,6-10,'$'’</SAMP> generates a hash 2068function that considers positions 1,2,4,6,7,8,9,10, plus the last 2069byte in each keyword (which may be at a different position for each 2070keyword, obviously). Keywords 2071with length less than the indicated byte positions work properly, since 2072selected byte positions exceeding the keyword length are simply not 2073referenced in the hash function. 2074 2075This option is not normally needed since version 2.8 of <CODE>gperf</CODE>; 2076the default byte positions are computed depending on the keyword set, 2077through a search that minimizes the number of byte positions. 2078 2079<DT><SAMP>‘-D’</SAMP> 2080<DD> 2081<DT><SAMP>‘--duplicates’</SAMP> 2082<DD> 2083<A NAME="IDX47"></A> 2084Handle keywords whose selected byte sets hash to duplicate values. 2085Duplicate hash values can occur if a set of keywords has the same names, but 2086possesses different attributes, or if the selected byte positions are not well 2087chosen. With the -D option <CODE>gperf</CODE> treats all these keywords as 2088part of an equivalence class and generates a perfect hash function with 2089multiple comparisons for duplicate keywords. It is up to you to completely 2090disambiguate the keywords by modifying the generated C code. However, 2091<CODE>gperf</CODE> helps you out by organizing the output. 2092 2093Using this option usually means that the generated hash function is no 2094longer perfect. On the other hand, it permits <CODE>gperf</CODE> to work on 2095keyword sets that it otherwise could not handle. 2096 2097<DT><SAMP>‘-m <VAR>iterations</VAR>’</SAMP> 2098<DD> 2099<DT><SAMP>‘--multiple-iterations=<VAR>iterations</VAR>’</SAMP> 2100<DD> 2101Perform multiple choices of the <SAMP>‘-i’</SAMP> and <SAMP>‘-j’</SAMP> values, and 2102choose the best results. This increases the running time by a factor of 2103<VAR>iterations</VAR> but does a good job minimizing the generated table size. 2104 2105<DT><SAMP>‘-i <VAR>initial-value</VAR>’</SAMP> 2106<DD> 2107<DT><SAMP>‘--initial-asso=<VAR>initial-value</VAR>’</SAMP> 2108<DD> 2109Provides an initial <VAR>value</VAR> for the associate values array. Default 2110is 0. Increasing the initial value helps inflate the final table size, 2111possibly leading to more time efficient keyword lookups. Note that this 2112option is not particularly useful when <SAMP>‘-S’</SAMP> (or, equivalently, 2113<SAMP>‘%switch’</SAMP>) is used. Also, 2114<SAMP>‘-i’</SAMP> is overridden when the <SAMP>‘-r’</SAMP> option is used. 2115 2116<DT><SAMP>‘-j <VAR>jump-value</VAR>’</SAMP> 2117<DD> 2118<DT><SAMP>‘--jump=<VAR>jump-value</VAR>’</SAMP> 2119<DD> 2120<A NAME="IDX48"></A> 2121Affects the ���jump value���, i.e., how far to advance the associated 2122byte value upon collisions. <VAR>Jump-value</VAR> is rounded up to an 2123odd number, the default is 5. If the <VAR>jump-value</VAR> is 0 <CODE>gperf</CODE> 2124jumps by random amounts. 2125 2126<DT><SAMP>‘-n’</SAMP> 2127<DD> 2128<DT><SAMP>‘--no-strlen’</SAMP> 2129<DD> 2130Instructs the generator not to include the length of a keyword when 2131computing its hash value. This may save a few assembly instructions in 2132the generated lookup table. 2133 2134<DT><SAMP>‘-r’</SAMP> 2135<DD> 2136<DT><SAMP>‘--random’</SAMP> 2137<DD> 2138Utilizes randomness to initialize the associated values table. This 2139frequently generates solutions faster than using deterministic 2140initialization (which starts all associated values at 0). Furthermore, 2141using the randomization option generally increases the size of the 2142table. 2143 2144<DT><SAMP>‘-s <VAR>size-multiple</VAR>’</SAMP> 2145<DD> 2146<DT><SAMP>‘--size-multiple=<VAR>size-multiple</VAR>’</SAMP> 2147<DD> 2148Affects the size of the generated hash table. The numeric argument for 2149this option indicates ���how many times larger or smaller��� the maximum 2150associated value range should be, in relationship to the number of keywords. 2151It can be written as an integer, a floating-point number or a fraction. 2152For example, a value of 3 means ���allow the maximum associated value to be 2153about 3 times larger than the number of input keywords���. 2154Conversely, a value of 1/3 means ���allow the maximum associated value to 2155be about 3 times smaller than the number of input keywords���. Values 2156smaller than 1 are useful for limiting the overall size of the generated hash 2157table, though the option <SAMP>‘-m’</SAMP> is better at this purpose. 2158 2159If `generate switch' option <SAMP>‘-S’</SAMP> (or, equivalently, <SAMP>‘%switch’</SAMP>) is 2160<EM>not</EM> enabled, the maximum 2161associated value influences the static array table size, and a larger 2162table should decrease the time required for an unsuccessful search, at 2163the expense of extra table space. 2164 2165The default value is 1, thus the default maximum associated value about 2166the same size as the number of keywords (for efficiency, the maximum 2167associated value is always rounded up to a power of 2). The actual 2168table size may vary somewhat, since this technique is essentially a 2169heuristic. 2170</DL> 2171 2172 2173 2174<H2><A NAME="SEC23" HREF="gperf.html#TOC23">5.6 Informative Output</A></H2> 2175 2176<DL COMPACT> 2177 2178<DT><SAMP>‘-h’</SAMP> 2179<DD> 2180<DT><SAMP>‘--help’</SAMP> 2181<DD> 2182Prints a short summary on the meaning of each program option. Aborts 2183further program execution. 2184 2185<DT><SAMP>‘-v’</SAMP> 2186<DD> 2187<DT><SAMP>‘--version’</SAMP> 2188<DD> 2189Prints out the current version number. 2190 2191<DT><SAMP>‘-d’</SAMP> 2192<DD> 2193<DT><SAMP>‘--debug’</SAMP> 2194<DD> 2195Enables the debugging option. This produces verbose diagnostics to 2196���standard error��� when <CODE>gperf</CODE> is executing. It is useful both for 2197maintaining the program and for determining whether a given set of 2198options is actually speeding up the search for a solution. Some useful 2199information is dumped at the end of the program when the <SAMP>‘-d’</SAMP> 2200option is enabled. 2201</DL> 2202 2203 2204 2205<H1><A NAME="SEC24" HREF="gperf.html#TOC24">6 Known Bugs and Limitations with <CODE>gperf</CODE></A></H1> 2206 2207<P> 2208The following are some limitations with the current release of 2209<CODE>gperf</CODE>: 2210 2211</P> 2212 2213<UL> 2214<LI> 2215 2216The <CODE>gperf</CODE> utility is tuned to execute quickly, and works quickly 2217for small to medium size data sets (around 1000 keywords). It is 2218extremely useful for maintaining perfect hash functions for compiler 2219keyword sets. Several recent enhancements now enable <CODE>gperf</CODE> to 2220work efficiently on much larger keyword sets (over 15,000 keywords). 2221When processing large keyword sets it helps greatly to have over 8 megs 2222of RAM. 2223 2224<LI> 2225 2226The size of the generate static keyword array can get <EM>extremely</EM> 2227large if the input keyword file is large or if the keywords are quite 2228similar. This tends to slow down the compilation of the generated C 2229code, and <EM>greatly</EM> inflates the object code size. If this 2230situation occurs, consider using the <SAMP>‘-S’</SAMP> option to reduce data 2231size, potentially increasing keyword recognition time a negligible 2232amount. Since many C compilers cannot correctly generate code for 2233large switch statements it is important to qualify the <VAR>-S</VAR> option 2234with an appropriate numerical argument that controls the number of 2235switch statements generated. 2236 2237<LI> 2238 2239The maximum number of selected byte positions has an 2240arbitrary limit of 255. This restriction should be removed, and if 2241anyone considers this a problem write me and let me know so I can remove 2242the constraint. 2243</UL> 2244 2245 2246 2247<H1><A NAME="SEC25" HREF="gperf.html#TOC25">7 Things Still Left to Do</A></H1> 2248 2249<P> 2250It should be ���relatively��� easy to replace the current perfect hash 2251function algorithm with a more exhaustive approach; the perfect hash 2252module is essential independent from other program modules. Additional 2253worthwhile improvements include: 2254 2255</P> 2256 2257<UL> 2258<LI> 2259 2260Another useful extension involves modifying the program to generate 2261���minimal��� perfect hash functions (under certain circumstances, the 2262current version can be rather extravagant in the generated table size). 2263This is mostly of theoretical interest, since a sparse table 2264often produces faster lookups, and use of the <SAMP>‘-S’</SAMP> <CODE>switch</CODE> 2265option can minimize the data size, at the expense of slightly longer 2266lookups (note that the gcc compiler generally produces good code for 2267<CODE>switch</CODE> statements, reducing the need for more complex schemes). 2268 2269<LI> 2270 2271In addition to improving the algorithm, it would also be useful to 2272generate an Ada package as the code output, in addition to the current 2273C and C++ routines. 2274</UL> 2275 2276 2277 2278<H1><A NAME="SEC26" HREF="gperf.html#TOC26">8 Bibliography</A></H1> 2279 2280<P> 2281[1] Chang, C.C.: <I>A Scheme for Constructing Ordered Minimal Perfect 2282Hashing Functions</I> Information Sciences 39(1986), 187-195. 2283 2284</P> 2285<P> 2286[2] Cichelli, Richard J. <I>Author's Response to ���On Cichelli's Minimal Perfect Hash 2287Functions Method���</I> Communications of the ACM, 23, 12(December 1980), 729. 2288 2289</P> 2290<P> 2291[3] Cichelli, Richard J. <I>Minimal Perfect Hash Functions Made Simple</I> 2292Communications of the ACM, 23, 1(January 1980), 17-19. 2293 2294</P> 2295<P> 2296[4] Cook, C. R. and Oldehoeft, R.R. <I>A Letter Oriented Minimal 2297Perfect Hashing Function</I> SIGPLAN Notices, 17, 9(September 1982), 18-27. 2298 2299</P> 2300<P> 2301[5] Cormack, G. V. and Horspool, R. N. S. and Kaiserwerth, M. 2302<I>Practical Perfect Hashing</I> Computer Journal, 28, 1(January 1985), 54-58. 2303 2304</P> 2305<P> 2306[6] Jaeschke, G. <I>Reciprocal Hashing: A Method for Generating Minimal 2307Perfect Hashing Functions</I> Communications of the ACM, 24, 12(December 23081981), 829-833. 2309 2310</P> 2311<P> 2312[7] Jaeschke, G. and Osterburg, G. <I>On Cichelli's Minimal Perfect 2313Hash Functions Method</I> Communications of the ACM, 23, 12(December 1980), 2314728-729. 2315 2316</P> 2317<P> 2318[8] Sager, Thomas J. <I>A Polynomial Time Generator for Minimal Perfect 2319Hash Functions</I> Communications of the ACM, 28, 5(December 1985), 523-532 2320 2321</P> 2322<P> 2323[9] Schmidt, Douglas C. <I>GPERF: A Perfect Hash Function Generator</I> 2324Second USENIX C++ Conference Proceedings, April 1990. 2325 2326</P> 2327<P> 2328[10] Schmidt, Douglas C. <I>GPERF: A Perfect Hash Function Generator</I> 2329C++ Report, SIGS 10 10 (November/December 1998). 2330 2331</P> 2332<P> 2333[11] Sebesta, R.W. and Taylor, M.A. <I>Minimal Perfect Hash Functions 2334for Reserved Word Lists</I> SIGPLAN Notices, 20, 12(September 1985), 47-53. 2335 2336</P> 2337<P> 2338[12] Sprugnoli, R. <I>Perfect Hashing Functions: A Single Probe 2339Retrieving Method for Static Sets</I> Communications of the ACM, 20 234011(November 1977), 841-850. 2341 2342</P> 2343<P> 2344[13] Stallman, Richard M. <I>Using and Porting GNU CC</I> Free Software Foundation, 23451988. 2346 2347</P> 2348<P> 2349[14] Stroustrup, Bjarne <I>The C++ Programming Language.</I> Addison-Wesley, 1986. 2350 2351</P> 2352<P> 2353[15] Tiemann, Michael D. <I>User's Guide to GNU C++</I> Free Software 2354Foundation, 1989. 2355 2356</P> 2357 2358 2359<H1><A NAME="SEC27" HREF="gperf.html#TOC27">Concept Index</A></H1> 2360 2361<P> 2362Jump to: 2363<A HREF="#cindex_&">&</A> 2364- 2365<A HREF="#cindex_a">a</A> 2366- 2367<A HREF="#cindex_b">b</A> 2368- 2369<A HREF="#cindex_c">c</A> 2370- 2371<A HREF="#cindex_d">d</A> 2372- 2373<A HREF="#cindex_f">f</A> 2374- 2375<A HREF="#cindex_h">h</A> 2376- 2377<A HREF="#cindex_i">i</A> 2378- 2379<A HREF="#cindex_j">j</A> 2380- 2381<A HREF="#cindex_k">k</A> 2382- 2383<A HREF="#cindex_m">m</A> 2384- 2385<A HREF="#cindex_n">n</A> 2386- 2387<A HREF="#cindex_s">s</A> 2388<P> 2389<H2><A NAME="cindex_&">&</A></H2> 2390<DIR> 2391<LI><A HREF="gperf.html#IDX8"><SAMP>‘%%’</SAMP></A> 2392<LI><A HREF="gperf.html#IDX18"><SAMP>‘%7bit’</SAMP></A> 2393<LI><A HREF="gperf.html#IDX19"><SAMP>‘%compare-lengths’</SAMP></A> 2394<LI><A HREF="gperf.html#IDX20"><SAMP>‘%compare-strncmp’</SAMP></A> 2395<LI><A HREF="gperf.html#IDX17"><SAMP>‘%define class-name’</SAMP></A> 2396<LI><A HREF="gperf.html#IDX15"><SAMP>‘%define hash-function-name’</SAMP></A> 2397<LI><A HREF="gperf.html#IDX14"><SAMP>‘%define initializer-suffix’</SAMP></A> 2398<LI><A HREF="gperf.html#IDX29"><SAMP>‘%define length-table-name’</SAMP></A> 2399<LI><A HREF="gperf.html#IDX16"><SAMP>‘%define lookup-function-name’</SAMP></A> 2400<LI><A HREF="gperf.html#IDX13"><SAMP>‘%define slot-name’</SAMP></A> 2401<LI><A HREF="gperf.html#IDX26"><SAMP>‘%define string-pool-name’</SAMP></A> 2402<LI><A HREF="gperf.html#IDX28"><SAMP>‘%define word-array-name’</SAMP></A> 2403<LI><A HREF="gperf.html#IDX9"><SAMP>‘%delimiters’</SAMP></A> 2404<LI><A HREF="gperf.html#IDX22"><SAMP>‘%enum’</SAMP></A> 2405<LI><A HREF="gperf.html#IDX24"><SAMP>‘%global-table’</SAMP></A> 2406<LI><A HREF="gperf.html#IDX11"><SAMP>‘%ignore-case’</SAMP></A> 2407<LI><A HREF="gperf.html#IDX23"><SAMP>‘%includes’</SAMP></A> 2408<LI><A HREF="gperf.html#IDX12"><SAMP>‘%language’</SAMP></A> 2409<LI><A HREF="gperf.html#IDX27"><SAMP>‘%null-strings’</SAMP></A> 2410<LI><A HREF="gperf.html#IDX31"><SAMP>‘%omit-struct-type’</SAMP></A> 2411<LI><A HREF="gperf.html#IDX25"><SAMP>‘%pic’</SAMP></A> 2412<LI><A HREF="gperf.html#IDX21"><SAMP>‘%readonly-tables’</SAMP></A> 2413<LI><A HREF="gperf.html#IDX10"><SAMP>‘%struct-type’</SAMP></A> 2414<LI><A HREF="gperf.html#IDX30"><SAMP>‘%switch’</SAMP></A> 2415<LI><A HREF="gperf.html#IDX32"><SAMP>‘%{’</SAMP></A> 2416<LI><A HREF="gperf.html#IDX33"><SAMP>‘%}’</SAMP></A> 2417</DIR> 2418<H2><A NAME="cindex_a">a</A></H2> 2419<DIR> 2420<LI><A HREF="gperf.html#IDX44">Array name</A>, <A HREF="gperf.html#IDX45">Array name</A> 2421</DIR> 2422<H2><A NAME="cindex_b">b</A></H2> 2423<DIR> 2424<LI><A HREF="gperf.html#IDX1">Bugs</A> 2425</DIR> 2426<H2><A NAME="cindex_c">c</A></H2> 2427<DIR> 2428<LI><A HREF="gperf.html#IDX43">Class name</A> 2429<LI><A HREF="gperf.html#IDX39">Copyright</A> 2430</DIR> 2431<H2><A NAME="cindex_d">d</A></H2> 2432<DIR> 2433<LI><A HREF="gperf.html#IDX5">Declaration section</A> 2434<LI><A HREF="gperf.html#IDX40">Delimiters</A> 2435<LI><A HREF="gperf.html#IDX47">Duplicates</A> 2436</DIR> 2437<H2><A NAME="cindex_f">f</A></H2> 2438<DIR> 2439<LI><A HREF="gperf.html#IDX4">Format</A> 2440<LI><A HREF="gperf.html#IDX7">Functions section</A> 2441</DIR> 2442<H2><A NAME="cindex_h">h</A></H2> 2443<DIR> 2444<LI><A HREF="gperf.html#IDX35">hash</A> 2445<LI><A HREF="gperf.html#IDX34">hash table</A> 2446</DIR> 2447<H2><A NAME="cindex_i">i</A></H2> 2448<DIR> 2449<LI><A HREF="gperf.html#IDX36">in_word_set</A> 2450<LI><A HREF="gperf.html#IDX42">Initializers</A> 2451</DIR> 2452<H2><A NAME="cindex_j">j</A></H2> 2453<DIR> 2454<LI><A HREF="gperf.html#IDX48">Jump value</A> 2455</DIR> 2456<H2><A NAME="cindex_k">k</A></H2> 2457<DIR> 2458<LI><A HREF="gperf.html#IDX6">Keywords section</A> 2459</DIR> 2460<H2><A NAME="cindex_m">m</A></H2> 2461<DIR> 2462<LI><A HREF="gperf.html#IDX3">Minimal perfect hash functions</A> 2463</DIR> 2464<H2><A NAME="cindex_n">n</A></H2> 2465<DIR> 2466<LI><A HREF="gperf.html#IDX38">NUL</A> 2467</DIR> 2468<H2><A NAME="cindex_s">s</A></H2> 2469<DIR> 2470<LI><A HREF="gperf.html#IDX41">Slot name</A> 2471<LI><A HREF="gperf.html#IDX2">Static search structure</A> 2472<LI><A HREF="gperf.html#IDX37"><CODE>switch</CODE></A>, <A HREF="gperf.html#IDX46"><CODE>switch</CODE></A> 2473</DIR> 2474 2475</P> 2476 2477<P><HR><P> 2478This document was generated on 1 February 2009 using the 2479<A HREF="http://wwwinfo.cern.ch/dis/texi2html/">texi2html</A> 2480translator version 1.52b.</P> 2481</BODY> 2482</HTML> 2483