lib/linebuffer.c

   1 /* linebuffer.c -- read arbitrarily long lines
   2
   3    Copyright (C) 1986, 1991, 1998-1999, 2001, 2003-2004, 2006-2007, 2009-2024
   4    Free 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 3 of the License, or
   9    (at your option) 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, see <https://www.gnu.org/licenses/>.  */
  18
  19 /* Written by Richard Stallman. */
  20
  21 #include <config.h>
  22
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <sys/types.h>
  27 #include "linebuffer.h"
  28 #include "xalloc.h"
  29
  30 #if USE_UNLOCKED_IO
  31 # include "unlocked-io.h"
  32 #endif
  33
  34 /* Initialize linebuffer LINEBUFFER for use. */
  35
  36 void
  37 initbuffer (struct linebuffer *linebuffer)
  38 {
  39   memset (linebuffer, 0, sizeof *linebuffer);
  40 }
  41
  42 struct linebuffer *
  43 readlinebuffer (struct linebuffer *linebuffer, FILE *stream)
  44 {
  45   return readlinebuffer_delim (linebuffer, stream, '\n');
  46 }
  47
  48 /* Read an arbitrarily long line of text from STREAM into LINEBUFFER.
  49    Consider lines to be terminated by DELIMITER.
  50    Keep the delimiter; append DELIMITER if it's the last line of a file
  51    that ends in a character other than DELIMITER.  Do not NUL-terminate.
  52    Therefore the stream can contain NUL bytes, and the length
  53    (including the delimiter) is returned in linebuffer->length.
  54    Return NULL when stream is empty.  Return NULL and set errno upon
  55    error; callers can distinguish this case from the empty case by
  56    invoking ferror (stream).
  57    Otherwise, return LINEBUFFER.  */
  58 struct linebuffer *
  59 readlinebuffer_delim (struct linebuffer *linebuffer, FILE *stream,
  60                       char delimiter)
  61 {
  62   int c;
  63   char *buffer = linebuffer->buffer;
  64   char *p = linebuffer->buffer;
  65   char *end = buffer + linebuffer->size; /* Sentinel. */
  66
  67   if (feof (stream))
  68     return NULL;
  69
  70   do
  71     {
  72       c = getc (stream);
  73       if (c == EOF)
  74         {
  75           if (p == buffer || ferror (stream))
  76             return NULL;
  77           if (p[-1] == delimiter)
  78             break;
  79           c = delimiter;
  80         }
  81       if (p == end)
  82         {
  83           idx_t oldsize = linebuffer->size;
  84           buffer = xpalloc (buffer, &linebuffer->size, 1, -1, 1);
  85           p = buffer + oldsize;
  86           linebuffer->buffer = buffer;
  87           end = buffer + linebuffer->size;
  88         }
  89       *p++ = c;
  90     }
  91   while (c != delimiter);
  92
  93   linebuffer->length = p - buffer;
  94   return linebuffer;
  95 }
  96
  97 /* Free the buffer that was allocated for linebuffer LINEBUFFER.  */
  98
  99 void
 100 freebuffer (struct linebuffer *linebuffer)
 101 {
 102   free (linebuffer->buffer);
 103 }