diplodocus.org Git - nmh/blob - sbr/getline.c

   1 /*
   2  * getline.c -- replacement getline() implementation
   3  *
   4  * This code is Copyright (c) 2016, by the authors of nmh.  See the
   5  * COPYRIGHT file in the root directory of the nmh distribution for
   6  * complete copyright information.
   7  */
   8
   9 #include <stdlib.h>
  10 #include <stdio.h>
  11 #include <limits.h>
  12 #include <errno.h>
  13
  14 #include <h/mh.h>
  15
  16 /* Largest possible size of buffer that allows SSIZE_MAX to be returned
  17  * to indicate SSIZE_MAX - 1 characters read before the '\n'.  The
  18  * additional 1 is for the terminating NUL. */
  19 #define MAX_AVAIL ((size_t)SSIZE_MAX + 1)
  20
  21 /* Ideal increase in size of line buffer. */
  22 #define GROWTH 128
  23
  24 ssize_t getline(char **lineptr, size_t *n, FILE *stream)
  25 {
  26     char *l;
  27     size_t avail;
  28     size_t used;
  29     int c;
  30     bool last;
  31
  32     if (!lineptr || !n) {
  33         errno = EINVAL;
  34         return -1;
  35     }
  36
  37     l = *lineptr;
  38     if (l)
  39         avail = *n <= MAX_AVAIL ? *n : MAX_AVAIL;
  40     else
  41         avail = *n = 0; /* POSIX allows *lineptr = NULL, *n = 42. */
  42     used = 0;
  43     last = false;
  44     for (;;) {
  45         c = getc(stream);
  46         if (c == EOF) {
  47             if (ferror(stream) || /* errno set by stdlib. */
  48                 !used)            /* EOF with nothing read. */
  49                 return -1;
  50             /* Line will be returned without a \n terminator. */
  51 append_nul:
  52             c = '\0';
  53             last = true;
  54         }
  55
  56         if (used == avail) {
  57             size_t want;
  58             char *new;
  59
  60             if (avail == MAX_AVAIL) {
  61                 errno = EOVERFLOW;
  62                 return -1;
  63             }
  64             want = avail + GROWTH;
  65             if (want > MAX_AVAIL)
  66                 want = MAX_AVAIL;
  67             new = realloc(l, want);
  68             if (!new)
  69                 return -1; /* errno set by stdlib. */
  70             l = *lineptr = new;
  71             avail = *n = want;
  72         }
  73         l[used++] = c;
  74
  75         if (last)
  76             return used - 1; /* Don't include NUL. */
  77
  78         if (c == '\n')
  79             goto append_nul; /* Final half loop. */
  80     }
  81 }