lib/linebuffer.c

   1 /* linebuffer.c -- read arbitrarily long lines
   2
   3    Copyright (C) 1986, 1991, 1998, 1999, 2001, 2003, 2004 Free
   4    Software Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 /* Written by Richard Stallman. */
  21 \f
  22 #ifdef HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <sys/types.h>
  30 #include "linebuffer.h"
  31 #include "xalloc.h"
  32
  33 #if USE_UNLOCKED_IO
  34 # include "unlocked-io.h"
  35 #endif
  36
  37 /* Initialize linebuffer LINEBUFFER for use. */
  38
  39 void
  40 initbuffer (struct linebuffer *linebuffer)
  41 {
  42   memset (linebuffer, 0, sizeof *linebuffer);
  43 }
  44
  45 /* Read an arbitrarily long line of text from STREAM into LINEBUFFER.
  46    Keep the newline; append a newline if it's the last line of a file
  47    that ends in a non-newline character.  Do not null terminate.
  48    Therefore the stream can contain NUL bytes, and the length
  49    (including the newline) is returned in linebuffer->length.
  50    Return NULL when stream is empty.  Return NULL and set errno upon
  51    error; callers can distinguish this case from the empty case by
  52    invoking ferror (stream).
  53    Otherwise, return LINEBUFFER.  */
  54 struct linebuffer *
  55 readlinebuffer (struct linebuffer *linebuffer, FILE *stream)
  56 {
  57   int c;
  58   char *buffer = linebuffer->buffer;
  59   char *p = linebuffer->buffer;
  60   char *end = buffer + linebuffer->size; /* Sentinel. */
  61
  62   if (feof (stream))
  63     return NULL;
  64
  65   do
  66     {
  67       c = getc (stream);
  68       if (c == EOF)
  69         {
  70           if (p == buffer || ferror (stream))
  71             return NULL;
  72           if (p[-1] == '\n')
  73             break;
  74           c = '\n';
  75         }
  76       if (p == end)
  77         {
  78           size_t oldsize = linebuffer->size;
  79           buffer = x2realloc (buffer, &linebuffer->size);
  80           p = buffer + oldsize;
  81           linebuffer->buffer = buffer;
  82           end = buffer + linebuffer->size;
  83         }
  84       *p++ = c;
  85     }
  86   while (c != '\n');
  87
  88   linebuffer->length = p - buffer;
  89   return linebuffer;
  90 }
  91
  92 /* Free the buffer that was allocated for linebuffer LINEBUFFER.  */
  93
  94 void
  95 freebuffer (struct linebuffer *linebuffer)
  96 {
  97   free (linebuffer->buffer);
  98 }