bash-5.1 distribution sources and documentation

[thirdparty/bash.git] / lib / sh / zgetline.c

/* zgetline - read a line of input from a specified file descriptor and return
	      a pointer to a newly-allocated buffer containing the data. */

/* Copyright (C) 2008-2020 Free Software Foundation, Inc.

   This file is part of GNU Bash, the Bourne Again SHell.

   Bash is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   Bash is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with Bash.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <config.h>

#include <sys/types.h>

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include <errno.h>
#include "xmalloc.h"

#if !defined (errno)
extern int errno;
#endif

extern ssize_t zread PARAMS((int, char *, size_t));
extern ssize_t zreadc PARAMS((int, char *));
extern ssize_t zreadintr PARAMS((int, char *, size_t));
extern ssize_t zreadcintr PARAMS((int, char *));

typedef ssize_t breadfunc_t PARAMS((int, char *, size_t));
typedef ssize_t creadfunc_t PARAMS((int, char *));

/* Initial memory allocation for automatic growing buffer in zreadlinec */
#define GET_LINE_INITIAL_ALLOCATION 16

/* Derived from GNU libc's getline.
   The behavior is almost the same as getline. See man getline.
   The differences are
   	(1) using file descriptor instead of FILE *;
	(2) the order of arguments: the file descriptor comes first;
	(3) the addition of a fourth argument, DELIM; sets the delimiter to
	    be something other than newline if desired.  If setting DELIM,
	    the next argument should be 1; and
	(4) the addition of a fifth argument, UNBUFFERED_READ; this argument
	    controls whether get_line uses buffering or not to get a byte data
	    from FD. get_line uses zreadc if UNBUFFERED_READ is zero; and
	    uses zread if UNBUFFERED_READ is non-zero.

   Returns number of bytes read or -1 on error. */

ssize_t
zgetline (fd, lineptr, n, delim, unbuffered_read)
     int fd;
     char **lineptr;
     size_t *n;
     int delim;
     int unbuffered_read;
{
  int nr, retval;
  char *line, c;

  if (lineptr == 0 || n == 0 || (*lineptr == 0 && *n != 0))
    return -1;

  nr = 0;
  line = *lineptr;
  
  while (1)
    {
      retval = unbuffered_read ? zread (fd, &c, 1) : zreadc(fd, &c);

      if (retval <= 0)
	{
	  if (line && nr > 0)
	    line[nr] = '\0';
	  break;
	}

      if (nr + 2 >= *n)
	{
	  size_t new_size;

	  new_size = (*n == 0) ? GET_LINE_INITIAL_ALLOCATION : *n * 2;
	  line = (*n >= new_size) ? NULL : xrealloc (*lineptr, new_size);

	  if (line)
	    {
	      *lineptr = line;
	      *n = new_size;
	    }
	  else
	    {
	      if (*n > 0)
		{
		  (*lineptr)[*n - 1] = '\0';
		  nr = *n - 2;
		}
	      break;
	    }
	}

      line[nr] = c;
      nr++;

      if (c == delim)
	{
	  line[nr] = '\0';
	  break;
	}
    }

  return nr - 1;
}