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) 2008,2009 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 extern ssize_t zread __P((int, char *, size_t));
  38 extern ssize_t zreadc __P((int, char *));
  39 extern ssize_t zreadintr __P((int, char *, size_t));
  40 extern ssize_t zreadcintr __P((int, char *));
  41
  42 typedef ssize_t breadfunc_t __P((int, char *, size_t));
  43 typedef ssize_t creadfunc_t __P((int, char *));
  44
  45 /* Initial memory allocation for automatic growing buffer in zreadlinec */
  46 #define GET_LINE_INITIAL_ALLOCATION 16
  47
  48 /* Derived from GNU libc's getline.
  49    The behavior is almost the same as getline. See man getline.
  50    The differences are
  51         (1) using file descriptor instead of FILE *,
  52         (2) the order of arguments; the file descriptor comes the first, and
  53         (3) the addtion of thired argument, UNBUFFERED_READ; this argument
  54             controls whether get_line uses buffering or not to get a byte data
  55             from FD. get_line uses zreadc if UNBUFFERED_READ is zero; and
  56             uses zread if UNBUFFERED_READ is non-zero.
  57
  58    Returns number of bytes read or -1 on error. */
  59
  60 ssize_t
  61 zgetline (fd, lineptr, n, unbuffered_read)
  62      int fd;
  63      char **lineptr;
  64      size_t *n;
  65      int unbuffered_read;
  66 {
  67   int nr, retval;
  68   char *line, c;
  69
  70   if (lineptr == 0 || n == 0 || (*lineptr == 0 && *n != 0))
  71     return -1;
  72
  73   nr = 0;
  74   line = *lineptr;
  75
  76   while (1)
  77     {
  78       retval = unbuffered_read ? zread (fd, &c, 1) : zreadc(fd, &c);
  79
  80       if (retval <= 0)
  81         {
  82           if (line && nr > 0)
  83             line[nr] = '\0';
  84           break;
  85         }
  86
  87       if (nr + 2 >= *n)
  88         {
  89           size_t new_size;
  90
  91           new_size = (*n == 0) ? GET_LINE_INITIAL_ALLOCATION : *n * 2;
  92           line = (*n >= new_size) ? NULL : xrealloc (*lineptr, new_size);
  93
  94           if (line)
  95             {
  96               *lineptr = line;
  97               *n = new_size;
  98             }
  99           else
 100             {
 101               if (*n > 0)
 102                 {
 103                   (*lineptr)[*n - 1] = '\0';
 104                   nr = *n - 2;
 105                 }
 106               break;
 107             }
 108         }
 109
 110       line[nr] = c;
 111       nr++;
 112
 113       if (c == '\n')
 114         {
 115           line[nr] = '\0';
 116           break;
 117         }
 118     }
 119
 120   return nr - 1;
 121 }