libio/fmemopen.c

   1 /* fmemopen implementation.
   2    Copyright (C) 2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 /* fmemopen() from 2.22 and forward works as defined by POSIX.  It also
  20    provides an older symbol, version 2.2.5, that behaves different regarding
  21    SEEK_END (libio/oldfmemopen.c).  */
  22
  23
  24 #include <errno.h>
  25 #include <libio.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <stdint.h>
  29 #include <string.h>
  30 #include <sys/types.h>
  31 #include "libioP.h"
  32
  33
  34 typedef struct fmemopen_cookie_struct fmemopen_cookie_t;
  35 struct fmemopen_cookie_struct
  36 {
  37   char        *buffer;   /* memory buffer.  */
  38   int         mybuffer;  /* allocated my buffer?  */
  39   int         append;    /* buffer open for append?  */
  40   size_t      size;      /* buffer length in bytes.  */
  41   _IO_off64_t pos;       /* current position at the buffer.  */
  42   size_t      maxpos;    /* max position in buffer.  */
  43 };
  44
  45
  46 static ssize_t
  47 fmemopen_read (void *cookie, char *b, size_t s)
  48 {
  49   fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
  50
  51   if (c->pos + s > c->maxpos)
  52     {
  53       if ((size_t) c->pos == c->maxpos)
  54         return 0;
  55       s = c->size - c->pos;
  56     }
  57
  58   memcpy (b, &(c->buffer[c->pos]), s);
  59
  60   c->pos += s;
  61   if ((size_t) c->pos > c->maxpos)
  62     c->maxpos = c->pos;
  63
  64   return s;
  65 }
  66
  67
  68 static ssize_t
  69 fmemopen_write (void *cookie, const char *b, size_t s)
  70 {
  71   fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;;
  72   _IO_off64_t pos = c->append ? c->maxpos : c->pos;
  73   int addnullc;
  74
  75   addnullc = (s == 0 || b[s - 1] != '\0');
  76
  77   if (pos + s + addnullc > c->size)
  78     {
  79       if ((size_t) (c->pos + addnullc) >= c->size)
  80         {
  81           __set_errno (ENOSPC);
  82           return 0;
  83         }
  84       s = c->size - pos - addnullc;
  85     }
  86
  87   memcpy (&(c->buffer[pos]), b, s);
  88
  89   pos += s;
  90   if ((size_t) pos > c->maxpos)
  91     {
  92       c->maxpos = pos;
  93       if (addnullc)
  94         c->buffer[c->maxpos] = '\0';
  95     }
  96
  97   return s;
  98 }
  99
 100
 101 static int
 102 fmemopen_seek (void *cookie, _IO_off64_t *p, int w)
 103 {
 104   _IO_off64_t np;
 105   fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
 106
 107   switch (w)
 108     {
 109     case SEEK_SET:
 110       np = *p;
 111       break;
 112
 113     case SEEK_CUR:
 114       np = c->pos + *p;
 115       break;
 116
 117     case SEEK_END:
 118       np = c->maxpos + *p;
 119       break;
 120
 121     default:
 122       return -1;
 123     }
 124
 125   if (np < 0 || (size_t) np > c->size)
 126     return -1;
 127
 128   *p = c->pos = np;
 129
 130   return 0;
 131 }
 132
 133
 134 static int
 135 fmemopen_close (void *cookie)
 136 {
 137   fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
 138
 139   if (c->mybuffer)
 140     free (c->buffer);
 141   free (c);
 142
 143   return 0;
 144 }
 145
 146
 147 FILE *
 148 __fmemopen (void *buf, size_t len, const char *mode)
 149 {
 150   cookie_io_functions_t iof;
 151   fmemopen_cookie_t *c;
 152
 153   c = (fmemopen_cookie_t *) calloc (sizeof (fmemopen_cookie_t), 1);
 154   if (c == NULL)
 155     return NULL;
 156
 157   c->mybuffer = (buf == NULL);
 158
 159   if (c->mybuffer)
 160     {
 161       c->buffer = (char *) malloc (len);
 162       if (c->buffer == NULL)
 163         {
 164           free (c);
 165           return NULL;
 166         }
 167       c->buffer[0] = '\0';
 168     }
 169   else
 170     {
 171       if (__glibc_unlikely ((uintptr_t) len > -(uintptr_t) buf))
 172         {
 173           free (c);
 174           __set_errno (EINVAL);
 175           return NULL;
 176         }
 177
 178       c->buffer = buf;
 179
 180       /* POSIX states that w+ mode should truncate the buffer.  */
 181       if (mode[0] == 'w' && mode[1] == '+')
 182         c->buffer[0] = '\0';
 183
 184       if (mode[0] == 'a')
 185         c->maxpos = strnlen (c->buffer, len);
 186     }
 187
 188
 189   /* Mode   |  starting position (cookie::pos) |          size (cookie::size)
 190      ------ |----------------------------------|-----------------------------
 191      read   |          beginning of the buffer |                size argument
 192      write  |          beginning of the buffer |                         zero
 193      append |    first null or size buffer + 1 |  first null or size argument
 194    */
 195
 196   c->size = len;
 197
 198   if (mode[0] == 'r')
 199     c->maxpos = len;
 200
 201   c->append = mode[0] == 'a';
 202   if (c->append)
 203     c->pos = c->maxpos;
 204   else
 205     c->pos = 0;
 206
 207   iof.read = fmemopen_read;
 208   iof.write = fmemopen_write;
 209   iof.seek = fmemopen_seek;
 210   iof.close = fmemopen_close;
 211
 212   return _IO_fopencookie (c, mode, iof);
 213 }
 214 libc_hidden_def (__fmemopen)
 215 versioned_symbol (libc, __fmemopen, fmemopen, GLIBC_2_22);