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#include "libbb.h"
10
11#define ZIPPED (ENABLE_FEATURE_SEAMLESS_LZMA \
12	|| ENABLE_FEATURE_SEAMLESS_BZ2 \
13	|| ENABLE_FEATURE_SEAMLESS_GZ \
14	/* || ENABLE_FEATURE_SEAMLESS_Z */ \
15)
16
17#if ZIPPED
18# include "unarchive.h"
19#endif
20
21
22/* Suppose that you are a shell. You start child processes.
23 * They work and eventually exit. You want to get user input.
24 * You read stdin. But what happens if last child switched
25 * its stdin into O_NONBLOCK mode?
26 *
27 * *** SURPRISE! It will affect the parent too! ***
28 * *** BIG SURPRISE! It stays even after child exits! ***
29 *
30 * This is a design bug in UNIX API.
31 *      fcntl(0, F_SETFL, fcntl(0, F_GETFL) | O_NONBLOCK);
32 * will set nonblocking mode not only on _your_ stdin, but
33 * also on stdin of your parent, etc.
34 *
35 * In general,
36 *      fd2 = dup(fd1);
37 *      fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL) | O_NONBLOCK);
38 * sets both fd1 and fd2 to O_NONBLOCK. This includes cases
39 * where duping is done implicitly by fork() etc.
40 *
41 * We need
42 *      fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD) | O_NONBLOCK);
43 * (note SETFD, not SETFL!) but such thing doesn't exist.
44 *
45 * Alternatively, we need nonblocking_read(fd, ...) which doesn't
46 * require O_NONBLOCK dance at all. Actually, it exists:
47 *      n = recv(fd, buf, len, MSG_DONTWAIT);
48 *      "MSG_DONTWAIT:
49 *      Enables non-blocking operation; if the operation
50 *      would block, EAGAIN is returned."
51 * but recv() works only for sockets!
52 *
53 * So far I don't see any good solution, I can only propose
54 * that affected readers should be careful and use this routine,
55 * which detects EAGAIN and uses poll() to wait on the fd.
56 * Thankfully, poll() doesn't care about O_NONBLOCK flag.
57 */
58ssize_t FAST_FUNC nonblock_safe_read(int fd, void *buf, size_t count)
59{
60	struct pollfd pfd[1];
61	ssize_t n;
62
63	while (1) {
64		n = safe_read(fd, buf, count);
65		if (n >= 0 || errno != EAGAIN)
66			return n;
67		/* fd is in O_NONBLOCK mode. Wait using poll and repeat */
68		pfd[0].fd = fd;
69		pfd[0].events = POLLIN;
70		safe_poll(pfd, 1, -1); /* note: this pulls in printf */
71	}
72}
73
74// Reads one line a-la fgets (but doesn't save terminating '\n').
75// Reads byte-by-byte. Useful when it is important to not read ahead.
76// Bytes are appended to pfx (which must be malloced, or NULL).
77char* FAST_FUNC xmalloc_reads(int fd, char *buf, size_t *maxsz_p)
78{
79	char *p;
80	size_t sz = buf ? strlen(buf) : 0;
81	size_t maxsz = maxsz_p ? *maxsz_p : (INT_MAX - 4095);
82
83	goto jump_in;
84	while (sz < maxsz) {
85		if ((size_t)(p - buf) == sz) {
86 jump_in:
87			buf = xrealloc(buf, sz + 128);
88			p = buf + sz;
89			sz += 128;
90		}
91		/* nonblock_safe_read() because we are used by e.g. shells */
92		if (nonblock_safe_read(fd, p, 1) != 1) { /* EOF/error */
93			if (p == buf) { /* we read nothing */
94				free(buf);
95				return NULL;
96			}
97			break;
98		}
99		if (*p == '\n')
100			break;
101		p++;
102	}
103	*p = '\0';
104	if (maxsz_p)
105		*maxsz_p  = p - buf;
106	p++;
107	return xrealloc(buf, p - buf);
108}
109
110// Read (potentially big) files in one go. File size is estimated
111// by stat. Extra '\0' byte is appended.
112void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
113{
114	char *buf;
115	size_t size, rd_size, total;
116	size_t to_read;
117	struct stat st;
118
119	to_read = maxsz_p ? *maxsz_p : (INT_MAX - 4095); /* max to read */
120
121	/* Estimate file size */
122	st.st_size = 0; /* in case fstat fails, assume 0 */
123	fstat(fd, &st);
124	/* /proc/N/stat files report st_size 0 */
125	/* In order to make such files readable, we add small const */
126	size = (st.st_size | 0x3ff) + 1;
127
128	total = 0;
129	buf = NULL;
130	while (1) {
131		if (to_read < size)
132			size = to_read;
133		buf = xrealloc(buf, total + size + 1);
134		rd_size = full_read(fd, buf + total, size);
135		if ((ssize_t)rd_size == (ssize_t)(-1)) { /* error */
136			free(buf);
137			return NULL;
138		}
139		total += rd_size;
140		if (rd_size < size) /* EOF */
141			break;
142		if (to_read <= rd_size)
143			break;
144		to_read -= rd_size;
145		/* grow by 1/8, but in [1k..64k] bounds */
146		size = ((total / 8) | 0x3ff) + 1;
147		if (size > 64*1024)
148			size = 64*1024;
149	}
150	buf = xrealloc(buf, total + 1);
151	buf[total] = '\0';
152
153	if (maxsz_p)
154		*maxsz_p = total;
155	return buf;
156}
157
158#ifdef USING_LSEEK_TO_GET_SIZE
159/* Alternatively, file size can be obtained by lseek to the end.
160 * The code is slightly bigger. Retained in case fstat approach
161 * will not work for some weird cases (/proc, block devices, etc).
162 * (NB: lseek also can fail to work for some weird files) */
163
164// Read (potentially big) files in one go. File size is estimated by
165// lseek to end.
166void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
167{
168	char *buf;
169	size_t size;
170	int fd;
171	off_t len;
172
173	fd = open(filename, O_RDONLY);
174	if (fd < 0)
175		return NULL;
176
177	/* /proc/N/stat files report len 0 here */
178	/* In order to make such files readable, we add small const */
179	size = 0x3ff; /* read only 1k on unseekable files */
180	len = lseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */
181	if (len != (off_t)-1) {
182		xlseek(fd, 0, SEEK_SET);
183		size = maxsz_p ? *maxsz_p : (INT_MAX - 4095);
184		if (len < size)
185			size = len;
186	}
187
188	buf = xmalloc(size + 1);
189	size = read_close(fd, buf, size);
190	if ((ssize_t)size < 0) {
191		free(buf);
192		return NULL;
193	}
194	buf = xrealloc(buf, size + 1);
195	buf[size] = '\0';
196
197	if (maxsz_p)
198		*maxsz_p = size;
199	return buf;
200}
201#endif
202
203// Read (potentially big) files in one go. File size is estimated
204// by stat.
205void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
206{
207	char *buf;
208	int fd;
209
210	fd = open(filename, O_RDONLY);
211	if (fd < 0)
212		return NULL;
213
214	buf = xmalloc_read(fd, maxsz_p);
215	close(fd);
216	return buf;
217}
218
219/* Die with an error message if we can't read the entire buffer. */
220void FAST_FUNC xread(int fd, void *buf, size_t count)
221{
222	if (count) {
223		ssize_t size = full_read(fd, buf, count);
224		if ((size_t)size != count)
225			bb_error_msg_and_die("short read");
226	}
227}
228
229/* Die with an error message if we can't read one character. */
230unsigned char FAST_FUNC xread_char(int fd)
231{
232	char tmp;
233	xread(fd, &tmp, 1);
234	return tmp;
235}
236
237void* FAST_FUNC xmalloc_xopen_read_close(const char *filename, size_t *maxsz_p)
238{
239	void *buf = xmalloc_open_read_close(filename, maxsz_p);
240	if (!buf)
241		bb_perror_msg_and_die("can't read '%s'", filename);
242	return buf;
243}
244
245/* Used by e.g. rpm which gives us a fd without filename,
246 * thus we can't guess the format from filename's extension.
247 */
248#if ZIPPED
249void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
250{
251	const int fail_if_not_detected = 1;
252	union {
253		uint8_t b[4];
254		uint16_t b16[2];
255		uint32_t b32[1];
256	} magic;
257	int offset = -2;
258# if BB_MMU
259	IF_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
260	enum { xformer_prog = 0 };
261# else
262	enum { xformer = 0 };
263	const char *xformer_prog;
264# endif
265
266	/* .gz and .bz2 both have 2-byte signature, and their
267	 * unpack_XXX_stream wants this header skipped. */
268	xread(fd, magic.b16, sizeof(magic.b16[0]));
269	if (ENABLE_FEATURE_SEAMLESS_GZ
270	 && magic.b16[0] == GZIP_MAGIC
271	) {
272# if BB_MMU
273		xformer = unpack_gz_stream;
274# else
275		xformer_prog = "gunzip";
276# endif
277		goto found_magic;
278	}
279	if (ENABLE_FEATURE_SEAMLESS_BZ2
280	 && magic.b16[0] == BZIP2_MAGIC
281	) {
282# if BB_MMU
283		xformer = unpack_bz2_stream;
284# else
285		xformer_prog = "bunzip2";
286# endif
287		goto found_magic;
288	}
289	if (ENABLE_FEATURE_SEAMLESS_XZ
290	 && magic.b16[0] == XZ_MAGIC1
291	) {
292		offset = -6;
293		xread(fd, magic.b32, sizeof(magic.b32[0]));
294		if (magic.b32[0] == XZ_MAGIC2) {
295# if BB_MMU
296			xformer = unpack_xz_stream;
297			/* unpack_xz_stream wants fd at position 6, no need to seek */
298			//xlseek(fd, offset, SEEK_CUR);
299# else
300			xformer_prog = "unxz";
301# endif
302			goto found_magic;
303		}
304	}
305
306	/* No known magic seen */
307	if (fail_if_not_detected)
308		bb_error_msg_and_die("no gzip"
309			IF_FEATURE_SEAMLESS_BZ2("/bzip2")
310			IF_FEATURE_SEAMLESS_XZ("/xz")
311			" magic");
312	xlseek(fd, offset, SEEK_CUR);
313	return;
314
315 found_magic:
316# if !BB_MMU
317	/* NOMMU version of open_transformer execs
318	 * an external unzipper that wants
319	 * file position at the start of the file */
320	xlseek(fd, offset, SEEK_CUR);
321# endif
322	open_transformer(fd, xformer, xformer_prog);
323}
324#endif /* ZIPPED */
325
326int FAST_FUNC open_zipped(const char *fname)
327{
328#if !ZIPPED
329	return open(fname, O_RDONLY);
330#else
331	char *sfx;
332	int fd;
333
334	fd = open(fname, O_RDONLY);
335	if (fd < 0)
336		return fd;
337
338	sfx = strrchr(fname, '.');
339	if (sfx) {
340		sfx++;
341		if (ENABLE_FEATURE_SEAMLESS_LZMA && strcmp(sfx, "lzma") == 0)
342			/* .lzma has no header/signature, just trust it */
343			open_transformer(fd, unpack_lzma_stream, "unlzma");
344		else
345		if ((ENABLE_FEATURE_SEAMLESS_GZ && strcmp(sfx, "gz") == 0)
346		 || (ENABLE_FEATURE_SEAMLESS_BZ2 && strcmp(sfx, "bz2") == 0)
347		 || (ENABLE_FEATURE_SEAMLESS_XZ && strcmp(sfx, "xz") == 0)
348		) {
349			setup_unzip_on_fd(fd /*, fail_if_not_detected: 1*/);
350		}
351	}
352
353	return fd;
354#endif
355}
356
357void* FAST_FUNC xmalloc_open_zipped_read_close(const char *fname, size_t *maxsz_p)
358{
359	int fd;
360	char *image;
361
362	fd = open_zipped(fname);
363	if (fd < 0)
364		return NULL;
365
366	image = xmalloc_read(fd, maxsz_p);
367	if (!image)
368		bb_perror_msg("read error from '%s'", fname);
369	close(fd);
370
371	return image;
372}
373