1/* zread - read data from file descriptor into buffer with retries */
2
3/* Copyright (C) 1999-2002 Free Software Foundation, Inc.
4
5   This file is part of GNU Bash, the Bourne Again SHell.
6
7   Bash is free software: you can redistribute it and/or modify
8   it under the terms of the GNU General Public License as published by
9   the Free Software Foundation, either version 3 of the License, or
10   (at your option) any later version.
11
12   Bash is distributed in the hope that it will be useful,
13   but WITHOUT ANY WARRANTY; without even the implied warranty of
14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   GNU General Public License for more details.
16
17   You should have received a copy of the GNU General Public License
18   along with Bash.  If not, see <http://www.gnu.org/licenses/>.
19*/
20
21#include <config.h>
22
23#include <sys/types.h>
24
25#if defined (HAVE_UNISTD_H)
26#  include <unistd.h>
27#endif
28
29#include <errno.h>
30
31#if !defined (errno)
32extern int errno;
33#endif
34
35#ifndef SEEK_CUR
36#  define SEEK_CUR 1
37#endif
38
39/* Read LEN bytes from FD into BUF.  Retry the read on EINTR.  Any other
40   error causes the loop to break. */
41ssize_t
42zread (fd, buf, len)
43     int fd;
44     char *buf;
45     size_t len;
46{
47  ssize_t r;
48
49  while ((r = read (fd, buf, len)) < 0 && errno == EINTR)
50    ;
51  return r;
52}
53
54/* Read LEN bytes from FD into BUF.  Retry the read on EINTR, up to three
55   interrupts.  Any other error causes the loop to break. */
56
57#ifdef NUM_INTR
58#  undef NUM_INTR
59#endif
60#define NUM_INTR 3
61
62ssize_t
63zreadretry (fd, buf, len)
64     int fd;
65     char *buf;
66     size_t len;
67{
68  ssize_t r;
69  int nintr;
70
71  for (nintr = 0; ; )
72    {
73      r = read (fd, buf, len);
74      if (r >= 0)
75	return r;
76      if (r == -1 && errno == EINTR)
77	{
78	  if (++nintr >= NUM_INTR)
79	    return -1;
80	  continue;
81	}
82      return r;
83    }
84}
85
86/* Call read(2) and allow it to be interrupted.  Just a stub for now. */
87ssize_t
88zreadintr (fd, buf, len)
89     int fd;
90     char *buf;
91     size_t len;
92{
93  return (read (fd, buf, len));
94}
95
96/* Read one character from FD and return it in CP.  Return values are as
97   in read(2).  This does some local buffering to avoid many one-character
98   calls to read(2), like those the `read' builtin performs. */
99
100static char lbuf[128];
101static size_t lind, lused;
102
103ssize_t
104zreadc (fd, cp)
105     int fd;
106     char *cp;
107{
108  ssize_t nr;
109
110  if (lind == lused || lused == 0)
111    {
112      nr = zread (fd, lbuf, sizeof (lbuf));
113      lind = 0;
114      if (nr <= 0)
115	{
116	  lused = 0;
117	  return nr;
118	}
119      lused = nr;
120    }
121  if (cp)
122    *cp = lbuf[lind++];
123  return 1;
124}
125
126/* Don't mix calls to zreadc and zreadcintr in the same function, since they
127   use the same local buffer. */
128ssize_t
129zreadcintr (fd, cp)
130     int fd;
131     char *cp;
132{
133  ssize_t nr;
134
135  if (lind == lused || lused == 0)
136    {
137      nr = zreadintr (fd, lbuf, sizeof (lbuf));
138      lind = 0;
139      if (nr <= 0)
140	{
141	  lused = 0;
142	  return nr;
143	}
144      lused = nr;
145    }
146  if (cp)
147    *cp = lbuf[lind++];
148  return 1;
149}
150
151void
152zreset ()
153{
154  lind = lused = 0;
155}
156
157/* Sync the seek pointer for FD so that the kernel's idea of the last char
158   read is the last char returned by zreadc. */
159void
160zsyncfd (fd)
161     int fd;
162{
163  off_t off;
164  int r;
165
166  off = lused - lind;
167  r = 0;
168  if (off > 0)
169    r = lseek (fd, -off, SEEK_CUR);
170
171  if (r >= 0)
172    lused = lind = 0;
173}
174