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) 2008-2020 Free Software Foundation, Inc.
   5
   6    This file is part of GNU Bush, the Bourne Again SHell.
   7
   8    Bush 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    Bush 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 Bush.  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 PARAMS((int, char *, size_t));
  38 extern ssize_t zreadc PARAMS((int, char *));
  39 extern ssize_t zreadintr PARAMS((int, char *, size_t));
  40 extern ssize_t zreadcintr PARAMS((int, char *));
  41
  42 typedef ssize_t breadfunc_t PARAMS((int, char *, size_t));
  43 typedef ssize_t creadfunc_t PARAMS((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 first;
  53         (3) the addition of a fourth argument, DELIM; sets the delimiter to
  54             be something other than newline if desired.  If setting DELIM,
  55             the next argument should be 1; and
  56         (4) the addition of a fifth argument, UNBUFFERED_READ; this argument
  57             controls whether get_line uses buffering or not to get a byte data
  58             from FD. get_line uses zreadc if UNBUFFERED_READ is zero; and
  59             uses zread if UNBUFFERED_READ is non-zero.
  60
  61    Returns number of bytes read or -1 on error. */
  62
  63 ssize_t
  64 zgetline (fd, lineptr, n, delim, unbuffered_read)
  65      int fd;
  66      char **lineptr;
  67      size_t *n;
  68      int delim;
  69      int unbuffered_read;
  70 {
  71   int nr, retval;
  72   char *line, c;
  73
  74   if (lineptr == 0 || n == 0 || (*lineptr == 0 && *n != 0))
  75     return -1;
  76
  77   nr = 0;
  78   line = *lineptr;
  79
  80   while (1)
  81     {
  82       retval = unbuffered_read ? zread (fd, &c, 1) : zreadc(fd, &c);
  83
  84       if (retval <= 0)
  85         {
  86           if (line && nr > 0)
  87             line[nr] = '\0';
  88           break;
  89         }
  90
  91       if (nr + 2 >= *n)
  92         {
  93           size_t new_size;
  94
  95           new_size = (*n == 0) ? GET_LINE_INITIAL_ALLOCATION : *n * 2;
  96           line = (*n >= new_size) ? NULL : xrealloc (*lineptr, new_size);
  97
  98           if (line)
  99             {
 100               *lineptr = line;
 101               *n = new_size;
 102             }
 103           else
 104             {
 105               if (*n > 0)
 106                 {
 107                   (*lineptr)[*n - 1] = '\0';
 108                   nr = *n - 2;
 109                 }
 110               break;
 111             }
 112         }
 113
 114       line[nr] = c;
 115       nr++;
 116
 117       if (c == delim)
 118         {
 119           line[nr] = '\0';
 120           break;
 121         }
 122     }
 123
 124   return nr - 1;
 125 }