lib/sh/zgetline.c

   1 /* zgetline - read a line of input from a specified file descriptor and return
   2               a pointer to a newly-allocated buffer containing the data. */
   3
   4 /* Copyright (C) 2008 Free Software Foundation, Inc.
   5
   6    This file is part of GNU Bash, the Bourne Again SHell.
   7
   8    Bash is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    Bash is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with Bash.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include <config.h>
  23
  24 #include <sys/types.h>
  25
  26 #if defined (HAVE_UNISTD_H)
  27 #  include <unistd.h>
  28 #endif
  29
  30 #include <errno.h>
  31 #include "xmalloc.h"
  32
  33 #if !defined (errno)
  34 extern int errno;
  35 #endif
  36
  37 /* Initial memory allocation for automatic growing buffer in zreadlinec */
  38 #define GET_LINE_INITIAL_ALLOCATION 16
  39
  40 /* Derived from GNU libc's getline.
  41    The behavior is almost the same as getline. See man getline.
  42    The differences are
  43         (1) using file descriptor instead of FILE *,
  44         (2) the order of arguments; the file descriptor comes the first, and
  45         (3) the addtion of thired argument, UNBUFFERED_READ; this argument
  46             controls whether get_line uses buffering or not to get a byte data
  47             from FD. get_line uses zreadc if UNBUFFERED_READ is zero; and
  48             uses zread if UNBUFFERED_READ is non-zero.
  49
  50    Returns number of bytes read or -1 on error. */
  51
  52 ssize_t
  53 zgetline (fd, lineptr, n, unbuffered_read)
  54      int fd;
  55      char **lineptr;
  56      size_t *n;
  57      int unbuffered_read;
  58 {
  59   int nr, retval;
  60   char *line, c;
  61
  62   if (lineptr == 0 || n == 0 || (*lineptr == 0 && *n != 0))
  63     return -1;
  64
  65   nr = 0;
  66   line = *lineptr;
  67
  68   while (1)
  69     {
  70       retval = unbuffered_read ? zread (fd, &c, 1) : zreadc(fd, &c);
  71
  72       if (retval <= 0)
  73         {
  74           line[nr] = '\0';
  75           break;
  76         }
  77
  78       if (nr + 2 >= *n)
  79         {
  80          size_t new_size;
  81
  82          new_size = (*n == 0) ? GET_LINE_INITIAL_ALLOCATION : *n * 2;
  83          line = xrealloc (*lineptr, new_size);
  84
  85          if (line)
  86            {
  87              *lineptr = line;
  88              *n = new_size;
  89            }
  90          else
  91            {
  92              if (*n > 0)
  93                {
  94                  (*lineptr)[*n - 1] = '\0';
  95                  nr = *n - 2;
  96                }
  97              break;
  98            }
  99         }
 100
 101       line[nr] = c;
 102       nr++;
 103
 104       if (c == '\n')
 105         {
 106           line[nr] = '\0';
 107           break;
 108         }
 109     }
 110
 111   return nr - 1;
 112 }