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  * SPDX-License-Identifier:     GPL-2.0+
   6  */
   7
   8 /* Written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
   9
  10 #include <assert.h>
  11 #include <stdio.h>
  12
  13 /* Always add at least this many bytes when extending the buffer.  */
  14 #define MIN_CHUNK 64
  15
  16 /* Read up to (and including) a TERMINATOR from STREAM into *LINEPTR
  17    + OFFSET (and null-terminate it). *LINEPTR is a pointer returned from
  18    malloc (or NULL), pointing to *N characters of space.  It is realloc'd
  19    as necessary.  Return the number of characters read (not including the
  20    null terminator), or -1 on error or EOF.
  21    NOTE: There is another getstr() function declared in <curses.h>.  */
  22 static int getstr(char **lineptr, size_t *n, FILE *stream,
  23                   char terminator, size_t offset)
  24 {
  25         int nchars_avail;       /* Allocated but unused chars in *LINEPTR.  */
  26         char *read_pos;         /* Where we're reading into *LINEPTR. */
  27         int ret;
  28
  29         if (!lineptr || !n || !stream)
  30                 return -1;
  31
  32         if (!*lineptr) {
  33                 *n = MIN_CHUNK;
  34                 *lineptr = malloc(*n);
  35                 if (!*lineptr)
  36                         return -1;
  37         }
  38
  39         nchars_avail = *n - offset;
  40         read_pos = *lineptr + offset;
  41
  42         for (;;) {
  43                 register int c = getc(stream);
  44
  45                 /* We always want at least one char left in the buffer, since we
  46                    always (unless we get an error while reading the first char)
  47                    NUL-terminate the line buffer.  */
  48
  49                 assert(*n - nchars_avail == read_pos - *lineptr);
  50                 if (nchars_avail < 2) {
  51                         if (*n > MIN_CHUNK)
  52                                 *n *= 2;
  53                         else
  54                                 *n += MIN_CHUNK;
  55
  56                         nchars_avail = *n + *lineptr - read_pos;
  57                         *lineptr = realloc(*lineptr, *n);
  58                         if (!*lineptr)
  59                                 return -1;
  60                         read_pos = *n - nchars_avail + *lineptr;
  61                         assert(*n - nchars_avail == read_pos - *lineptr);
  62                 }
  63
  64                 if (c == EOF || ferror (stream)) {
  65                         /* Return partial line, if any.  */
  66                         if (read_pos == *lineptr)
  67                                 return -1;
  68                         else
  69                                 break;
  70                 }
  71
  72                 *read_pos++ = c;
  73                 nchars_avail--;
  74
  75                 if (c == terminator)
  76                         /* Return the line.  */
  77                         break;
  78         }
  79
  80         /* Done - NUL terminate and return the number of chars read.  */
  81         *read_pos = '\0';
  82
  83         ret = read_pos - (*lineptr + offset);
  84         return ret;
  85 }
  86
  87 int getline (char **lineptr, size_t *n, FILE *stream)
  88 {
  89         return getstr(lineptr, n, stream, '\n', 0);
  90 }