Libc-1044.1.2/stdio/xprintf_domain.3

.Dd Aug 19, 2012
.Dt XPRINTF_DOMAIN 3
.Os Darwin
.Sh NAME
.Nm copy_printf_domain , free_printf_domain , new_printf_domain ,
.Nm register_printf_domain_function , register_printf_domain_render_std
.Nd extensible printf domains
.Sh SYNOPSIS
.In printf.h
.Ft printf_domain_t
.Fn copy_printf_domain "printf_domain_t domain"
.Ft void
.Fn free_printf_domain "printf_domain_t domain"
.Ft printf_domain_t
.Fn new_printf_domain void
.Ft int
.Fn register_printf_domain_function "printf_domain_t domain" "int spec" "printf_function *render" "printf_arginfo_function *arginfo", "void *context"
.Ft int
.Fn register_printf_domain_render_std "printf_domain_t domain" "const char *specs"
.Sh DESCRIPTION
A printf domain is an extensible printf (see
.Xr xprintf 5 )
structure defining a set of conversion specifiers that
will be used in calls to the routines discussed in
.Xr xprintf 3
and
.Xr xprintf_comp 3 .
Domains can be modified independently of one another, and do not affect the
behavior of the normal printf calls in
.Xr printf 3 .
.Pp
To create a new domain, call
.Fn new_printf_domain ;
the standard POSIX conversion specifiers are defined by default.
To make a copy of an existing domain, use
.Fn copy_printf_domain .
When a domain is no longer needed, call
.Fn free_printf_domain
to release the associated memory.
.Pp
The
.Fn register_printf_domain_function
function is used to add, modify or remove conversion specifiers for a
given domain.
The
.Fa spec
argument is the specifier character, which can be any printable (non-control)
ASCII character,
except for those characters that are used as flag/option characters.
The set of flag/option characters includes the space character, and the
following:
.Pp
.Dl # $ ' * + \&, - \&. 0 1 2 3 4 5 6 7 8 9 \&: \&; L _ h j l q t v z
.Pp
Two user-defined callback function must also be given; see
.Xr xprintf 5
for a description of these callback functions and an example of use.
Setting either or both callbacks to
.Dv NULL
deletes the given specifier from the domain.
Note that while it is permissible to redefine the standard conversion
specifiers, it is not usually recommended as it may cause confusion.
.Pp
The
.Fn register_printf_domain_render_std
function is used to add pre-defined conversion specifiers to the given domain.
The
.Fa specs
argument is a null-terminated C string containing one or more of the following
specifier characters:
.Bl -tag -width ".Li H"
.It Li H
Hex dump.
The
.Sq Li H
specifier takes two arguments; the first is a pointer to the data to
dump, while the second argument is the length of the data, given as type
.Vt unsigned .
Normally, 16 characters are displayed per line, as pairs of hex characters
separated by spaces.
Specifying a field width less than 16 will display that number of characters
per line.
Setting the
.Sq Li +
(showsign) flag will prefix each line with the hex offset of the beginning
character in that line.
Setting the
.Sq Li #
(alternate form) flag will postfix an ASCII representation to each line, with
.Sq Li \&.
representing non-printable characters.
.It Li M
Errno.
The
.Sq Li M
specifier displayed the text representation of the given
.Vt int
argument, expected to be a valid
.Va errno
value (as returned by
.Xr strerror 3 ) .
Invalid errno values are represent by the
.Dq Li errno=
string followed by the decimal and hex values of the argument.
.It Li Q
Quoted.
The
.Sq Li Q
specifier displays a null-terminated string argument as a C string, with
leading and trailing double quotes.
Newlines, carriage-returns and tabs are represented by
.Sq Li \en ,
.Sq Li \er
and
.Sq Li \et ,
respectively, while backslashes and double quotes are preceeded with a
backslash.
All other whitespace characters not including space itself (those in which
.Xr isspace 3
returns true) are displayed as octal escape sequences (a backslash followed by
three octal digits).
All other characters print as themselves.
.It Li T
time_t/timeval/timespec.
The
.Sq Li T
specifier displays the three types of time values as a single decimal value.
The argument should be a pointer to the time value to be converted.
Setting the appropriate flags indicates which type is indicated:
.Bl -tag -width ".Pq none"
.It Li ll
The
.Sq Li ll
(long long) flag indicates the argument points to a
.Vt struct timespec
structure.
The default precision is 9.
.It Li l
The
.Sq Li l
(long) flag indicates the argument points to a
.Vt struct timeval
structure.
The default precision is 6.
.It Pq none
By default, the argument points to a
.Vt time_t
value.
The default precision is 0 (the fractional part is not displayed).
.El
.Pp
If the
.Sq Li #
(alternate form) flag is specified, the value is displayed in years, days,
hours, minutes and seconds, as in:
.Dq Li 3y123d21h59m59s.987654
(zero values are not displayed at all).
Note that the years are 365 days (no leap days).
.It Li V
String vis.
The
.Sq Li V
specifier uses
.Xr strvisx 3
to display the null-terminated C string argument.
The precision value can be used to limit the amount of the string that is
processed (defaults to the entire string).
.Pp
Flag values can be used to obtain different encodings:
.Bl -tag -width "(none)"
.It Li +
The
.Sq Li +
(showsign) flag uses the
.Dq Li VIS_WHITE | VIS_HTTPSTYLE
flag value to
.Xr strvisx 3 .
.It Li 0
The
.Sq Li 0
(leading zero) flag uses the
.Dq Li VIS_WHITE | VIS_OCTAL
flag value to
.Xr strvisx 3 .
.It Li #
The
.Sq Li #
(alternate form) flag uses the
.Dq Li VIS_WHITE
flag value to
.Xr strvisx 3 .
.It Pq none
The default flag value to
.Xr strvisx 3
is
.Dq Li VIS_WHITE | VIS_CSTYLE | VIS_OCTAL .
.El
.El
.Sh RETURN VALUES
The
.Fn new_printf_domain
and
.Fn copy_printf_domain
functions return the new domain, or
.Dv NULL
on failure (usually out of memory condition).
.Pp
The
.Fn register_printf_domain_function
and
.Fn register_printf_domain_render_std
return zero on success and \-1 on failure (usually due to an improper specifier
character or out of memory condition).
.Sh SEE ALSO
.Xr printf 3 ,
.Xr strvisx 3 ,
.Xr xprintf 3 ,
.Xr xprintf_comp 3 ,
.Xr xprintf 5