lib/getline.c

   1 /* getline.c -- Replacement for GNU C library function getline
   2
   3 Copyright (C) 1993 Free Software Foundation, Inc.
   4
   5 This program is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful, but
  11 WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program; if not, write to the Free Software
  17 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
  18
  19 /* Written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
  20
  21 #ifdef HAVE_CONFIG_H
  22 #include <config.h>
  23 #endif
  24
  25 #include <sys/types.h>
  26 #include <stdio.h>
  27 #define NDEBUG
  28 #include <assert.h>
  29
  30 #if STDC_HEADERS
  31 #include <stdlib.h>
  32 #else
  33 char *malloc (), *realloc ();
  34 #endif
  35
  36 /* Always add at least this many bytes when extending the buffer.  */
  37 #define MIN_CHUNK 64
  38
  39 /* Read up to (and including) a TERMINATOR from STREAM into *LINEPTR
  40    + OFFSET (and null-terminate it). *LINEPTR is a pointer returned from
  41    malloc (or NULL), pointing to *N characters of space.  It is realloc'd
  42    as necessary.  Return the number of characters read (not including the
  43    null terminator), or -1 on error or EOF.  */
  44
  45 int
  46 getstr (lineptr, n, stream, terminator, offset)
  47      char **lineptr;
  48      size_t *n;
  49      FILE *stream;
  50      char terminator;
  51      int offset;
  52 {
  53   int nchars_avail;             /* Allocated but unused chars in *LINEPTR.  */
  54   char *read_pos;               /* Where we're reading into *LINEPTR. */
  55   int ret;
  56
  57   if (!lineptr || !n || !stream)
  58     return -1;
  59
  60   if (!*lineptr)
  61     {
  62       *n = MIN_CHUNK;
  63       *lineptr = malloc (*n);
  64       if (!*lineptr)
  65         return -1;
  66     }
  67
  68   nchars_avail = *n - offset;
  69   read_pos = *lineptr + offset;
  70
  71   for (;;)
  72     {
  73       register int c = getc (stream);
  74
  75       /* We always want at least one char left in the buffer, since we
  76          always (unless we get an error while reading the first char)
  77          NUL-terminate the line buffer.  */
  78
  79       assert(*n - nchars_avail == read_pos - *lineptr);
  80       if (nchars_avail < 1)
  81         {
  82           /* make sure that
  83            *   1.  nchars_avail is at least one
  84            *   2.  always make *n a multiple of MIN_CHUNK just larger
  85            *       than condition 1 requires
  86            */
  87           *n = ((read_pos - *lineptr + 1) + 1)/MIN_CHUNK * MIN_CHUNK;
  88           nchars_avail = *n + *lineptr - read_pos;
  89           *lineptr = realloc (*lineptr, *n);
  90           if (!*lineptr)
  91             return -1;
  92           read_pos = *n - nchars_avail + *lineptr;
  93           assert(*n - nchars_avail == read_pos - *lineptr);
  94         }
  95
  96       if (c == EOF || ferror (stream))
  97         {
  98           /* Return partial line, if any.  */
  99           if (read_pos == *lineptr)
 100             return -1;
 101           else
 102             break;
 103         }
 104
 105       *read_pos++ = c;
 106       nchars_avail--;
 107
 108       if (c == terminator)
 109         /* Return the line.  */
 110         break;
 111     }
 112
 113   /* Done - NUL terminate and return the number of chars read.  */
 114   *read_pos = '\0';
 115
 116   ret = read_pos - (*lineptr + offset);
 117   return ret;
 118 }
 119
 120 int
 121 getline (lineptr, n, stream)
 122      char **lineptr;
 123      size_t *n;
 124      FILE *stream;
 125 {
 126   return getstr (lineptr, n, stream, '\n', 0);
 127 }