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 #ifdef HAVE_STDBOOL_H
  14 # include <stdbool.h>
  15 #else  /* ! HAVE_STDBOOL_H */
  16 # define bool int
  17 # define true 1
  18 # define false 0
  19 #endif /* ! HAVE_STDBOOL_H */
  20
  21 /* Largest possible size of buffer that allows SSIZE_MAX to be returned
  22  * to indicate SSIZE_MAX - 1 characters read before the '\n'.  The
  23  * additional 1 is for the terminating NUL. */
  24 #define MAX_AVAIL ((size_t)SSIZE_MAX + 1)
  25
  26 /* Ideal increase in size of line buffer. */
  27 #define GROWTH 128
  28
  29 ssize_t getline(char **lineptr, size_t *n, FILE *stream)
  30 {
  31     char *l;
  32     size_t avail;
  33     size_t used;
  34     int c;
  35     bool last;
  36
  37     if (!lineptr || !n) {
  38         errno = EINVAL;
  39         return -1;
  40     }
  41
  42     l = *lineptr;
  43     if (l)
  44         avail = *n <= MAX_AVAIL ? *n : MAX_AVAIL;
  45     else
  46         avail = *n = 0; /* POSIX allows *lineptr = NULL, *n = 42. */
  47     used = 0;
  48     last = false;
  49     for (;;) {
  50         c = getc(stream);
  51         if (c == EOF) {
  52             if (ferror(stream) || /* errno set by stdlib. */
  53                 !used)            /* EOF with nothing read. */
  54                 return -1;
  55             /* Line will be returned without a \n terminator. */
  56 append_nul:
  57             c = '\0';
  58             last = true;
  59         }
  60
  61         if (used == avail) {
  62             size_t want;
  63             char *new;
  64
  65             if (avail == MAX_AVAIL) {
  66                 errno = EOVERFLOW;
  67                 return -1;
  68             }
  69             want = avail + GROWTH;
  70             if (want > MAX_AVAIL)
  71                 want = MAX_AVAIL;
  72             new = realloc(l, want);
  73             if (!new)
  74                 return -1; /* errno set by stdlib. */
  75             l = *lineptr = new;
  76             avail = *n = want;
  77         }
  78         l[used++] = c;
  79
  80         if (last)
  81             return used - 1; /* Don't include NUL. */
  82
  83         if (c == '\n')
  84             goto append_nul; /* Final half loop. */
  85     }
  86 }