1/* 2 * string1.lex: Handling strings by using input() 3 */ 4 5%{ 6#include <ctype.h> 7#include <malloc.h> 8 9#define ALLOC_SIZE 32 /* for (re)allocating the buffer */ 10 11#define isodigit(x) ((x) >= '0' && (x) <= '7') 12#define hextoint(x) (isdigit((x)) ? (x) - '0' : ((x) - 'A') + 10) 13 14void yyerror(char *message) 15{ 16 printf("\nError: %s\n",message); 17} 18 19%} 20 21%% 22 23\" { 24 int inch,count,max_size; 25 char *buffer; 26 int temp; 27 28 buffer = malloc(ALLOC_SIZE); 29 max_size = ALLOC_SIZE; 30 inch = input(); 31 count = 0; 32 while(inch != EOF && inch != '"' && inch != '\n'){ 33 if(inch == '\\'){ 34 inch = input(); 35 switch(inch){ 36 case '\n': inch = input(); break; 37 case 'b' : inch = '\b'; break; 38 case 't' : inch = '\t'; break; 39 case 'n' : inch = '\n'; break; 40 case 'v' : inch = '\v'; break; 41 case 'f' : inch = '\f'; break; 42 case 'r' : inch = '\r'; break; 43 case 'X' : 44 case 'x' : inch = input(); 45 if(isxdigit(inch)){ 46 temp = hextoint(toupper(inch)); 47 inch = input(); 48 if(isxdigit(inch)){ 49 temp = (temp << 4) + hextoint(toupper(inch)); 50 } else { 51 unput(inch); 52 } 53 inch = temp; 54 } else { 55 unput(inch); 56 inch = 'x'; 57 } 58 break; 59 default: 60 if(isodigit(inch)){ 61 temp = inch - '0'; 62 inch = input(); 63 if(isodigit(inch)){ 64 temp = (temp << 3) + (inch - '0'); 65 } else { 66 unput(inch); 67 goto done; 68 } 69 inch = input(); 70 if(isodigit(inch)){ 71 temp = (temp << 3) + (inch - '0'); 72 } else { 73 unput(inch); 74 } 75 done: 76 inch = temp; 77 } 78 } 79 } 80 buffer[count++] = inch; 81 if(count >= max_size){ 82 buffer = realloc(buffer,max_size + ALLOC_SIZE); 83 max_size += ALLOC_SIZE; 84 } 85 inch = input(); 86 } 87 if(inch == EOF || inch == '\n'){ 88 yyerror("Unterminated string."); 89 } 90 buffer[count] = '\0'; 91 printf("String = \"%s\"\n",buffer); 92 free(buffer); 93 } 94. 95\n 96%% 97 98 99