source: branches/3.2/mindi-busybox/libbb/read_printf.c @ 3186

Last change on this file since 3186 was 2725, checked in by bruno, 8 years ago
  • Update mindi-busybox to 1.18.3 to avoid problems with the tar command which is now failing on recent versions with busybox 1.7.3
  • Property svn:eol-style set to native
File size: 9.0 KB
Line 
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 source tree.
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 "archive.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}
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