tools/getline.c

   1 /* getline.c -- Replacement for GNU C library function getline
   2
   3 Copyright (C) 1993, 1996, 2001, 2002 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
  18
  19 /* Written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
  20
  21 #include <assert.h>
  22 #include <stdio.h>
  23
  24 /* Always add at least this many bytes when extending the buffer.  */
  25 #define MIN_CHUNK 64
  26
  27 /* Read up to (and including) a TERMINATOR from STREAM into *LINEPTR
  28    + OFFSET (and null-terminate it). *LINEPTR is a pointer returned from
  29    malloc (or NULL), pointing to *N characters of space.  It is realloc'd
  30    as necessary.  Return the number of characters read (not including the
  31    null terminator), or -1 on error or EOF.
  32    NOTE: There is another getstr() function declared in <curses.h>.  */
  33 static int getstr(char **lineptr, size_t *n, FILE *stream,
  34                   char terminator, size_t offset)
  35 {
  36         int nchars_avail;       /* Allocated but unused chars in *LINEPTR.  */
  37         char *read_pos;         /* Where we're reading into *LINEPTR. */
  38         int ret;
  39
  40         if (!lineptr || !n || !stream)
  41                 return -1;
  42
  43         if (!*lineptr) {
  44                 *n = MIN_CHUNK;
  45                 *lineptr = malloc(*n);
  46                 if (!*lineptr)
  47                         return -1;
  48         }
  49
  50         nchars_avail = *n - offset;
  51         read_pos = *lineptr + offset;
  52
  53         for (;;) {
  54                 register int c = getc(stream);
  55
  56                 /* We always want at least one char left in the buffer, since we
  57                    always (unless we get an error while reading the first char)
  58                    NUL-terminate the line buffer.  */
  59
  60                 assert(*n - nchars_avail == read_pos - *lineptr);
  61                 if (nchars_avail < 2) {
  62                         if (*n > MIN_CHUNK)
  63                                 *n *= 2;
  64                         else
  65                                 *n += MIN_CHUNK;
  66
  67                         nchars_avail = *n + *lineptr - read_pos;
  68                         *lineptr = realloc(*lineptr, *n);
  69                         if (!*lineptr)
  70                                 return -1;
  71                         read_pos = *n - nchars_avail + *lineptr;
  72                         assert(*n - nchars_avail == read_pos - *lineptr);
  73                 }
  74
  75                 if (c == EOF || ferror (stream)) {
  76                         /* Return partial line, if any.  */
  77                         if (read_pos == *lineptr)
  78                                 return -1;
  79                         else
  80                                 break;
  81                 }
  82
  83                 *read_pos++ = c;
  84                 nchars_avail--;
  85
  86                 if (c == terminator)
  87                         /* Return the line.  */
  88                         break;
  89         }
  90
  91         /* Done - NUL terminate and return the number of chars read.  */
  92         *read_pos = '\0';
  93
  94         ret = read_pos - (*lineptr + offset);
  95         return ret;
  96 }
  97
  98 int getline (char **lineptr, size_t *n, FILE *stream)
  99 {
 100         return getstr(lineptr, n, stream, '\n', 0);
 101 }