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

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