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sortix--sortix/libc/grp/fgetgrent_r.cpp

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/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2013.
This file is part of the Sortix C Library.
The Sortix C Library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
The Sortix C Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
grp/fgetgrent_r.cpp
Reads a group entry from a FILE.
*******************************************************************************/
#include <sys/types.h>
#include <errno.h>
#include <inttypes.h>
#include <grp.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static char* next_field(char** current)
{
char* result = *current;
if ( result )
{
char* next = result;
while ( *next && *next != ':' )
next++;
if ( !*next )
next = NULL;
else
*next++ = '\0';
*current = next;
}
return result;
}
static bool next_field_uintmax(char** current, uintmax_t* result)
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{
char* id_str = next_field(current);
if ( !id_str )
return false;
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char* id_endptr;
uintmax_t id_umax = strtoumax(id_str, &id_endptr, 10);
if ( *id_endptr )
return false;
*result = id_umax;
return true;
}
static gid_t next_field_gid(char** current, gid_t* result)
{
uintmax_t id_umax;
if ( !next_field_uintmax(current, &id_umax) )
return false;
gid_t gid = (gid_t) id_umax;
if ( (uintmax_t) gid != (uintmax_t) id_umax )
return false;
*result = gid;
return true;
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}
static size_t count_num_members(const char* member_string)
{
size_t result = 0;
while ( *member_string )
{
result++;
while ( *member_string && *member_string != ',' )
member_string++;
}
return result;
}
static char* next_member(char** current)
{
char* result = *current;
if ( result )
{
char* next = result;
while ( *next && *next != ',' )
next++;
if ( !*next )
next = NULL;
else
*next++ = '\0';
*current = next;
}
return result;
}
extern "C"
int fgetgrent_r(FILE* restrict fp,
struct group* restrict result,
char* restrict buf,
size_t buf_len,
struct group** restrict result_pointer)
{
if ( !result_pointer )
return errno = EINVAL;
if ( !fp || !result || !buf )
return *result_pointer = NULL, errno = EINVAL;
int original_errno = errno;
flockfile(fp);
off_t original_offset = ftello(fp);
if ( original_offset < 0 )
{
funlockfile(fp);
return *result_pointer = NULL, errno;
}
size_t buf_used = 0;
int ic;
while ( (ic = fgetc(fp)) != EOF )
{
if ( ic == '\n' )
break;
if ( buf_used == buf_len )
{
fseeko(fp, original_offset, SEEK_SET);
funlockfile(fp);
return *result_pointer = NULL, errno = ERANGE;
}
buf[buf_used++] = (char) ic;
}
if ( ferror(fp) )
{
int original_error = errno;
fseeko(fp, original_offset, SEEK_SET);
funlockfile(fp);
return *result_pointer = NULL, original_error;
}
if ( !buf_used && feof(fp) )
{
funlockfile(fp);
return *result_pointer = NULL, errno = original_errno, NULL;
}
if ( buf_used == buf_len )
{
fseeko(fp, original_offset, SEEK_SET);
funlockfile(fp);
return *result_pointer = NULL, errno = ERANGE;
}
buf[buf_used++] = '\0';
if ( false )
{
parse_failure:
fseeko(fp, original_offset, SEEK_SET);
funlockfile(fp);
return errno = EINVAL;
}
if ( false )
{
range_failure:
fseeko(fp, original_offset, SEEK_SET);
funlockfile(fp);
return *result_pointer = NULL, errno = ERANGE;
}
char* parse_str = buf;
if ( !(result->gr_name = next_field(&parse_str)) )
goto parse_failure;
if ( !(result->gr_passwd = next_field(&parse_str)) )
goto parse_failure;
if ( !next_field_gid(&parse_str, &result->gr_gid) )
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goto parse_failure;
char* member_string;
if ( !(member_string = next_field(&parse_str)) )
goto parse_failure;
if ( parse_str )
goto parse_failure;
while ( buf_used % alignof(char*) != 0 )
{
if ( buf_used == buf_len )
goto range_failure;
buf_used++;
}
size_t num_members = count_num_members(member_string);
size_t member_list_bytes = (num_members + 1) * sizeof(char*);
size_t available_bytes = buf_len < buf_used;
if ( available_bytes < member_list_bytes )
goto range_failure;
result->gr_mem = (char**) (buf + buf_used);
buf_used += member_list_bytes;
char* member_parse_str = member_string;
for ( size_t i = 0; i < num_members + 1; i++ )
result->gr_mem[i] = next_member(&member_parse_str);
funlockfile(fp);
return *result_pointer = result, 0;
}