Diff of /trunk/mkinitrd-magellan/busybox/libbb/read.c

Parent Directory | Revision Log | Patch

	revision 532 by niro, Sat Sep 1 22:45:15 2007 UTC	revision 816 by niro, Fri Apr 24 18:33:46 2009 UTC
#	Line 9	Line 9
9
10	#include "libbb.h"	#include "libbb.h"
11
12	ssize_t safe_read(int fd, void *buf, size_t count)	#define ZIPPED (ENABLE_FEATURE_SEAMLESS_LZMA \
13		|| ENABLE_FEATURE_SEAMLESS_BZ2 \
14		|| ENABLE_FEATURE_SEAMLESS_GZ \
15		/* || ENABLE_FEATURE_SEAMLESS_Z */ \
16		)
17
18		#if ZIPPED
19		#include "unarchive.h"
20		#endif
21
22		ssize_t FAST_FUNC safe_read(int fd, void *buf, size_t count)
23	{	{
24	ssize_t n;	ssize_t n;
25
#	Line 20  ssize_t safe_read(int fd, void *buf, siz	Line 30  ssize_t safe_read(int fd, void *buf, siz
30	return n;	return n;
31	}	}
32
33		/* Suppose that you are a shell. You start child processes.
34		* They work and eventually exit. You want to get user input.
35		* You read stdin. But what happens if last child switched
36		* its stdin into O_NONBLOCK mode?
37		*
38		* *** SURPRISE! It will affect the parent too! ***
39		* *** BIG SURPRISE! It stays even after child exits! ***
40		*
41		* This is a design bug in UNIX API.
42		*      fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0) | O_NONBLOCK);
43		* will set nonblocking mode not only on _your_ stdin, but
44		* also on stdin of your parent, etc.
45		*
46		* In general,
47		*      fd2 = dup(fd1);
48		*      fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL, 0) | O_NONBLOCK);
49		* sets both fd1 and fd2 to O_NONBLOCK. This includes cases
50		* where duping is done implicitly by fork() etc.
51		*
52		* We need
53		*      fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD, 0) | O_NONBLOCK);
54		* (note SETFD, not SETFL!) but such thing doesn't exist.
55		*
56		* Alternatively, we need nonblocking_read(fd, ...) which doesn't
57		* require O_NONBLOCK dance at all. Actually, it exists:
58		*      n = recv(fd, buf, len, MSG_DONTWAIT);
59		*      "MSG_DONTWAIT:
60		*      Enables non-blocking operation; if the operation
61		*      would block, EAGAIN is returned."
62		* but recv() works only for sockets!
63		*
64		* So far I don't see any good solution, I can only propose
65		* that affected readers should be careful and use this routine,
66		* which detects EAGAIN and uses poll() to wait on the fd.
67		* Thankfully, poll() doesn't care about O_NONBLOCK flag.
68		*/
69		ssize_t FAST_FUNC nonblock_safe_read(int fd, void *buf, size_t count)
70		{
71		struct pollfd pfd[1];
72		ssize_t n;
73
74		while (1) {
75		n = safe_read(fd, buf, count);
76		if (n >= 0 || errno != EAGAIN)
77		return n;
78		/* fd is in O_NONBLOCK mode. Wait using poll and repeat */
79		pfd[0].fd = fd;
80		pfd[0].events = POLLIN;
81		safe_poll(pfd, 1, -1);
82		}
83		}
84
85	/*	/*
86	* Read all of the supplied buffer from a file.	* Read all of the supplied buffer from a file.
87	* This does multiple reads as necessary.	* This does multiple reads as necessary.
88	* Returns the amount read, or -1 on an error.	* Returns the amount read, or -1 on an error.
89	* A short read is returned on an end of file.	* A short read is returned on an end of file.
90	*/	*/
91	ssize_t full_read(int fd, void *buf, size_t len)	ssize_t FAST_FUNC full_read(int fd, void *buf, size_t len)
92	{	{
93	ssize_t cc;	ssize_t cc;
94	ssize_t total;	ssize_t total;
#	Line 36  ssize_t full_read(int fd, void *buf, siz	Line 98  ssize_t full_read(int fd, void *buf, siz
98	while (len) {	while (len) {
99	cc = safe_read(fd, buf, len);	cc = safe_read(fd, buf, len);
100
101	if (cc < 0)	if (cc < 0) {
102	return cc; /* read() returns -1 on failure. */	if (total) {
103		/* we already have some! */
104		/* user can do another read to know the error code */
105		return total;
106		}
107		return cc; /* read() returns -1 on failure. */
108		}
109	if (cc == 0)	if (cc == 0)
110	break;	break;
111	buf = ((char *)buf) + cc;	buf = ((char *)buf) + cc;
112	total += cc;	total += cc;
113	len -= cc;	len -= cc;
#	Line 50  ssize_t full_read(int fd, void *buf, siz	Line 116  ssize_t full_read(int fd, void *buf, siz
116	return total;	return total;
117	}	}
118
119	// Die with an error message if we can't read the entire buffer.	/* Die with an error message if we can't read the entire buffer. */
120	void xread(int fd, void *buf, size_t count)	void FAST_FUNC xread(int fd, void *buf, size_t count)
121	{	{
122	if (count) {	if (count) {
123	ssize_t size = full_read(fd, buf, count);	ssize_t size = full_read(fd, buf, count);
124	if (size != count)	if ((size_t)size != count)
125	bb_error_msg_and_die("short read");	bb_error_msg_and_die("short read");
126	}	}
127	}	}
128
129	// Die with an error message if we can't read one character.	/* Die with an error message if we can't read one character. */
130	unsigned char xread_char(int fd)	unsigned char FAST_FUNC xread_char(int fd)
131	{	{
132	char tmp;	char tmp;
133	xread(fd, &tmp, 1);	xread(fd, &tmp, 1);
134	return tmp;	return tmp;
135	}	}
136
137	// Read one line a-la fgets. Works only on seekable streams	// Reads one line a-la fgets (but doesn't save terminating '\n').
138	char *reads(int fd, char *buffer, size_t size)	// Reads byte-by-byte. Useful when it is important to not read ahead.
139		// Bytes are appended to pfx (which must be malloced, or NULL).
140		char* FAST_FUNC xmalloc_reads(int fd, char *buf, size_t *maxsz_p)
141	{	{
142	char *p;	char *p;
143		size_t sz = buf ? strlen(buf) : 0;
144		size_t maxsz = maxsz_p ? *maxsz_p : MAXINT(size_t);
145
146	if (size < 2)	goto jump_in;
147	return NULL;	while (sz < maxsz) {
148	size = full_read(fd, buffer, size-1);	if ((size_t)(p - buf) == sz) {
149	if ((ssize_t)size <= 0)	jump_in:
150	return NULL;	buf = xrealloc(buf, sz + 128);
151		p = buf + sz;
152	buffer[size] = '\0';	sz += 128;
153	p = strchr(buffer, '\n');	}
154	if (p) {	/* nonblock_safe_read() because we are used by e.g. shells */
155	off_t offset;	if (nonblock_safe_read(fd, p, 1) != 1) { /* EOF/error */
156	*p++ = '\0';	if (p == buf) { /* we read nothing */
157	// avoid incorrect (unsigned) widening	free(buf);
158	offset = (off_t)(p-buffer) - (off_t)size;	return NULL;
159	// set fd position right after '\n'	}
160	if (offset && lseek(fd, offset, SEEK_CUR) == (off_t)-1)	break;
161	return NULL;	}
162		if (*p == '\n')
163		break;
164		p++;
165	}	}
166	return buffer;	*p = '\0';
167		if (maxsz_p)
168		*maxsz_p  = p - buf;
169		p++;
170		return xrealloc(buf, p - buf);
171	}	}
172
173	ssize_t read_close(int fd, void *buf, size_t size)	ssize_t FAST_FUNC read_close(int fd, void *buf, size_t size)
174	{	{
175	int e;	/*int e;*/
176	size = full_read(fd, buf, size);	size = full_read(fd, buf, size);
177	e = errno;	/*e = errno;*/
178	close(fd);	close(fd);
179	errno = e;	/*errno = e;*/
180	return size;	return size;
181	}	}
182
183	ssize_t open_read_close(const char *filename, void *buf, size_t size)	ssize_t FAST_FUNC open_read_close(const char *filename, void *buf, size_t size)
184	{	{
185	int fd = open(filename, O_RDONLY);	int fd = open(filename, O_RDONLY);
186	if (fd < 0)	if (fd < 0)
#	Line 113  ssize_t open_read_close(const char *file	Line 188  ssize_t open_read_close(const char *file
188	return read_close(fd, buf, size);	return read_close(fd, buf, size);
189	}	}
190
191	void *xmalloc_open_read_close(const char *filename, size_t *sizep)
192		// Read (potentially big) files in one go. File size is estimated
193		// by stat. Extra '\0' byte is appended.
194		void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
195		{
196		char *buf;
197		size_t size, rd_size, total;
198		size_t to_read;
199		struct stat st;
200
201		to_read = maxsz_p ? *maxsz_p : MAXINT(ssize_t); /* max to read */
202
203		/* Estimate file size */
204		st.st_size = 0; /* in case fstat fails, assume 0 */
205		fstat(fd, &st);
206		/* /proc/N/stat files report st_size 0 */
207		/* In order to make such files readable, we add small const */
208		size = (st.st_size | 0x3ff) + 1;
209
210		total = 0;
211		buf = NULL;
212		while (1) {
213		if (to_read < size)
214		size = to_read;
215		buf = xrealloc(buf, total + size + 1);
216		rd_size = full_read(fd, buf + total, size);
217		if ((ssize_t)rd_size == (ssize_t)(-1)) { /* error */
218		free(buf);
219		return NULL;
220		}
221		total += rd_size;
222		if (rd_size < size) /* EOF */
223		break;
224		if (to_read <= rd_size)
225		break;
226		to_read -= rd_size;
227		/* grow by 1/8, but in [1k..64k] bounds */
228		size = ((total / 8) | 0x3ff) + 1;
229		if (size > 64*1024)
230		size = 64*1024;
231		}
232		xrealloc(buf, total + 1);
233		buf[total] = '\0';
234
235		if (maxsz_p)
236		*maxsz_p = total;
237		return buf;
238		}
239
240		#ifdef USING_LSEEK_TO_GET_SIZE
241		/* Alternatively, file size can be obtained by lseek to the end.
242		* The code is slightly bigger. Retained in case fstat approach
243		* will not work for some weird cases (/proc, block devices, etc).
244		* (NB: lseek also can fail to work for some weird files) */
245
246		// Read (potentially big) files in one go. File size is estimated by
247		// lseek to end.
248		void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
249	{	{
250	char *buf;	char *buf;
251	size_t size = sizep ? *sizep : INT_MAX;	size_t size;
252	int fd = xopen(filename, O_RDONLY);	int fd;
253		off_t len;
254
255		fd = open(filename, O_RDONLY);
256		if (fd < 0)
257		return NULL;
258
259	/* /proc/N/stat files report len 0 here */	/* /proc/N/stat files report len 0 here */
260	/* In order to make such files readable, we add small const */	/* In order to make such files readable, we add small const */
261	off_t len = xlseek(fd, 0, SEEK_END) + 256;	size = 0x3ff; /* read only 1k on unseekable files */
262	xlseek(fd, 0, SEEK_SET);	len = lseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */
263		if (len != (off_t)-1) {
264		xlseek(fd, 0, SEEK_SET);
265		size = maxsz_p ? *maxsz_p : INT_MAX;
266		if (len < size)
267		size = len;
268		}
269
	if (len > size)
	bb_error_msg_and_die("file '%s' is too big", filename);
	size = len;
270	buf = xmalloc(size + 1);	buf = xmalloc(size + 1);
271	size = read_close(fd, buf, size);	size = read_close(fd, buf, size);
272	if ((ssize_t)size < 0)	if ((ssize_t)size < 0) {
273	bb_perror_msg_and_die("'%s'", filename);	free(buf);
274		return NULL;
275		}
276	xrealloc(buf, size + 1);	xrealloc(buf, size + 1);
277	buf[size] = '\0';	buf[size] = '\0';
278	if (sizep) *sizep = size;
279		if (maxsz_p)
280		*maxsz_p = size;
281		return buf;
282		}
283		#endif
284
285		// Read (potentially big) files in one go. File size is estimated
286		// by stat.
287		void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
288		{
289		char *buf;
290		int fd;
291
292		fd = open(filename, O_RDONLY);
293		if (fd < 0)
294		return NULL;
295
296		buf = xmalloc_read(fd, maxsz_p);
297		close(fd);
298		return buf;
299		}
300
301		void* FAST_FUNC xmalloc_xopen_read_close(const char *filename, size_t *maxsz_p)
302		{
303		void *buf = xmalloc_open_read_close(filename, maxsz_p);
304		if (!buf)
305		bb_perror_msg_and_die("can't read '%s'", filename);
306	return buf;	return buf;
307	}	}
308
309		int FAST_FUNC open_zipped(const char *fname)
310		{
311		#if !ZIPPED
312		return open(fname, O_RDONLY);
313		#else
314		unsigned char magic[2];
315		char *sfx;
316		int fd;
317		#if BB_MMU
318		USE_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
319		enum { xformer_prog = 0 };
320		#else
321		enum { xformer = 0 };
322		const char *xformer_prog;
323		#endif
324
325		fd = open(fname, O_RDONLY);
326		if (fd < 0)
327		return fd;
328
329		sfx = strrchr(fname, '.');
330		if (sfx) {
331		if (ENABLE_FEATURE_SEAMLESS_LZMA && strcmp(sfx, ".lzma") == 0)
332		/* .lzma has no header/signature, just trust it */
333		open_transformer(fd, unpack_lzma_stream, "unlzma");
334		else
335		if ((ENABLE_FEATURE_SEAMLESS_GZ && strcmp(sfx, ".gz") == 0)
336		|| (ENABLE_FEATURE_SEAMLESS_BZ2 && strcmp(sfx, ".bz2") == 0)
337		) {
338		/* .gz and .bz2 both have 2-byte signature, and their
339		* unpack_XXX_stream want this header skipped. */
340		xread(fd, &magic, 2);
341		#if ENABLE_FEATURE_SEAMLESS_GZ
342		#if BB_MMU
343		xformer = unpack_gz_stream;
344		#else
345		xformer_prog = "gunzip";
346		#endif
347		#endif
348		if (!ENABLE_FEATURE_SEAMLESS_GZ
349		|| magic[0] != 0x1f || magic[1] != 0x8b
350		) {
351		if (!ENABLE_FEATURE_SEAMLESS_BZ2
352		|| magic[0] != 'B' || magic[1] != 'Z'
353		) {
354		bb_error_msg_and_die("no gzip"
355		USE_FEATURE_SEAMLESS_BZ2("/bzip2")
356		" magic");
357		}
358		#if BB_MMU
359		xformer = unpack_bz2_stream;
360		#else
361		xformer_prog = "bunzip2";
362		#endif
363		} else {
364		#if !BB_MMU
365		/* NOMMU version of open_transformer execs
366		* an external unzipper that wants
367		* file position at the start of the file */
368		xlseek(fd, 0, SEEK_SET);
369		#endif
370		}
371		open_transformer(fd, xformer, xformer_prog);
372		}
373		}
374
375		return fd;
376		#endif
377		}
378
379		void* FAST_FUNC xmalloc_open_zipped_read_close(const char *fname, size_t *maxsz_p)
380		{
381		int fd;
382		char *image;
383
384		fd = open_zipped(fname);
385		if (fd < 0)
386		return NULL;
387
388		image = xmalloc_read(fd, maxsz_p);
389		if (!image)
390		bb_perror_msg("read error from '%s'", fname);
391		close(fd);
392
393		return image;
394		}

---

Colored Diff Long Colored Diff Full Colored Diff Unidiff Context Diff Side by Side

Legend: Removed from v.532   changed lines   Added in v.816