1/* vi: set sw=4 ts=4: */
2/*
3 * Utility routines.
4 *
5 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
6 *
7 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
8 */
9
10#include "libbb.h"
11
12ssize_t safe_read(int fd, void *buf, size_t count)
13{
14	ssize_t n;
15
16	do {
17		n = read(fd, buf, count);
18	} while (n < 0 && errno == EINTR);
19
20	return n;
21}
22
23/*
24 * Read all of the supplied buffer from a file.
25 * This does multiple reads as necessary.
26 * Returns the amount read, or -1 on an error.
27 * A short read is returned on an end of file.
28 */
29ssize_t full_read(int fd, void *buf, size_t len)
30{
31	ssize_t cc;
32	ssize_t total;
33
34	total = 0;
35
36	while (len) {
37		cc = safe_read(fd, buf, len);
38
39		if (cc < 0)
40			return cc;	/* read() returns -1 on failure. */
41		if (cc == 0)
42			break;
43		buf = ((char *)buf) + cc;
44		total += cc;
45		len -= cc;
46	}
47
48	return total;
49}
50
51// Die with an error message if we can't read the entire buffer.
52void xread(int fd, void *buf, size_t count)
53{
54	if (count) {
55		ssize_t size = full_read(fd, buf, count);
56		if (size != count)
57			bb_error_msg_and_die("short read");
58	}
59}
60
61// Die with an error message if we can't read one character.
62unsigned char xread_char(int fd)
63{
64	char tmp;
65	xread(fd, &tmp, 1);
66	return tmp;
67}
68
69// Read one line a-la fgets. Works only on seekable streams
70char *reads(int fd, char *buffer, size_t size)
71{
72	char *p;
73
74	if (size < 2)
75		return NULL;
76	size = full_read(fd, buffer, size-1);
77	if ((ssize_t)size <= 0)
78		return NULL;
79
80	buffer[size] = '\0';
81	p = strchr(buffer, '\n');
82	if (p) {
83		off_t offset;
84		*p++ = '\0';
85		// avoid incorrect (unsigned) widening
86		offset = (off_t)(p-buffer) - (off_t)size;
87		// set fd position right after '\n'
88		if (offset && lseek(fd, offset, SEEK_CUR) == (off_t)-1)
89			return NULL;
90	}
91	return buffer;
92}
93
94// Read one line a-la fgets. Reads byte-by-byte.
95// Useful when it is important to not read ahead.
96char *xmalloc_reads(int fd, char *buf)
97{
98	char *p;
99	int sz = buf ? strlen(buf) : 0;
100
101	goto jump_in;
102	while (1) {
103		if (p - buf == sz) {
104 jump_in:
105			buf = xrealloc(buf, sz + 128);
106			p = buf + sz;
107			sz += 128;
108		}
109		if (safe_read(fd, p, 1) != 1) { /* EOF/error */
110			if (p == buf) {
111				/* we read nothing [and buf was NULL initially] */
112				free(buf);
113				return NULL;
114			}
115			break;
116		}
117		if (*p == '\n')
118			break;
119		p++;
120	}
121	*p++ = '\0';
122	return xrealloc(buf, p - buf);
123}
124
125ssize_t read_close(int fd, void *buf, size_t size)
126{
127	/*int e;*/
128	size = full_read(fd, buf, size);
129	/*e = errno;*/
130	close(fd);
131	/*errno = e;*/
132	return size;
133}
134
135ssize_t open_read_close(const char *filename, void *buf, size_t size)
136{
137	int fd = open(filename, O_RDONLY);
138	if (fd < 0)
139		return fd;
140	return read_close(fd, buf, size);
141}
142
143// Read (potentially big) files in one go. File size is estimated by
144// lseek to end.
145void *xmalloc_open_read_close(const char *filename, size_t *sizep)
146{
147	char *buf;
148	size_t size = sizep ? *sizep : INT_MAX;
149	int fd;
150	off_t len;
151
152	fd = xopen(filename, O_RDONLY);
153	/* /proc/N/stat files report len 0 here */
154	/* In order to make such files readable, we add small const */
155	len = xlseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */
156	xlseek(fd, 0, SEEK_SET);
157	if (len < size)
158		size = len;
159	buf = xmalloc(size + 1);
160	size = read_close(fd, buf, size);
161	if ((ssize_t)size < 0)
162		bb_perror_msg_and_die("'%s'", filename);
163	xrealloc(buf, size + 1);
164	buf[size] = '\0';
165	if (sizep)
166		*sizep = size;
167	return buf;
168}
169