tools/getline.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /* getline.c -- Replacement for GNU C library function getline
   3  *
   4  * Copyright (C) 1993, 1996, 2001, 2002 Free Software Foundation, Inc.
   5  */
   6
   7 /* Written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
   8
   9 #include <assert.h>
  10 #include <stdio.h>
  11
  12 /* Always add at least this many bytes when extending the buffer.  */
  13 #define MIN_CHUNK 64
  14
  15 /* Read up to (and including) a TERMINATOR from STREAM into *LINEPTR
  16    + OFFSET (and null-terminate it). *LINEPTR is a pointer returned from
  17    malloc (or NULL), pointing to *N characters of space.  It is realloc'd
  18    as necessary.  Return the number of characters read (not including the
  19    null terminator), or -1 on error or EOF.
  20    NOTE: There is another getstr() function declared in <curses.h>.  */
  21 static int getstr(char **lineptr, size_t *n, FILE *stream,
  22                   char terminator, size_t offset)
  23 {
  24         int nchars_avail;       /* Allocated but unused chars in *LINEPTR.  */
  25         char *read_pos;         /* Where we're reading into *LINEPTR. */
  26         int ret;
  27
  28         if (!lineptr || !n || !stream)
  29                 return -1;
  30
  31         if (!*lineptr) {
  32                 *n = MIN_CHUNK;
  33                 *lineptr = malloc(*n);
  34                 if (!*lineptr)
  35                         return -1;
  36         }
  37
  38         nchars_avail = *n - offset;
  39         read_pos = *lineptr + offset;
  40
  41         for (;;) {
  42                 register int c = getc(stream);
  43
  44                 /* We always want at least one char left in the buffer, since we
  45                    always (unless we get an error while reading the first char)
  46                    NUL-terminate the line buffer.  */
  47
  48                 assert(*n - nchars_avail == read_pos - *lineptr);
  49                 if (nchars_avail < 2) {
  50                         if (*n > MIN_CHUNK)
  51                                 *n *= 2;
  52                         else
  53                                 *n += MIN_CHUNK;
  54
  55                         nchars_avail = *n + *lineptr - read_pos;
  56                         *lineptr = realloc(*lineptr, *n);
  57                         if (!*lineptr)
  58                                 return -1;
  59                         read_pos = *n - nchars_avail + *lineptr;
  60                         assert(*n - nchars_avail == read_pos - *lineptr);
  61                 }
  62
  63                 if (c == EOF || ferror (stream)) {
  64                         /* Return partial line, if any.  */
  65                         if (read_pos == *lineptr)
  66                                 return -1;
  67                         else
  68                                 break;
  69                 }
  70
  71                 *read_pos++ = c;
  72                 nchars_avail--;
  73
  74                 if (c == terminator)
  75                         /* Return the line.  */
  76                         break;
  77         }
  78
  79         /* Done - NUL terminate and return the number of chars read.  */
  80         *read_pos = '\0';
  81
  82         ret = read_pos - (*lineptr + offset);
  83         return ret;
  84 }
  85
  86 int getline (char **lineptr, size_t *n, FILE *stream)
  87 {
  88         return getstr(lineptr, n, stream, '\n', 0);
  89 }