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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [zlib/] [examples/] [gzlog.c] - Blame information for rev 745

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Line No. Rev Author Line
1 745 jeremybenn
/*
2
 * gzlog.c
3
 * Copyright (C) 2004 Mark Adler
4
 * For conditions of distribution and use, see copyright notice in gzlog.h
5
 * version 1.0, 26 Nov 2004
6
 *
7
 */
8
 
9
#include <string.h>             /* memcmp() */
10
#include <stdlib.h>             /* malloc(), free(), NULL */
11
#include <sys/types.h>          /* size_t, off_t */
12
#include <unistd.h>             /* read(), close(), sleep(), ftruncate(), */
13
                                /* lseek() */
14
#include <fcntl.h>              /* open() */
15
#include <sys/file.h>           /* flock() */
16
#include "zlib.h"               /* deflateInit2(), deflate(), deflateEnd() */
17
 
18
#include "gzlog.h"              /* interface */
19
#define local static
20
 
21
/* log object structure */
22
typedef struct {
23
    int id;                 /* object identifier */
24
    int fd;                 /* log file descriptor */
25
    off_t extra;            /* offset of extra "ap" subfield */
26
    off_t mark_off;         /* offset of marked data */
27
    off_t last_off;         /* offset of last block */
28
    unsigned long crc;      /* uncompressed crc */
29
    unsigned long len;      /* uncompressed length (modulo 2^32) */
30
    unsigned stored;        /* length of current stored block */
31
} gz_log;
32
 
33
#define GZLOGID 19334       /* gz_log object identifier */
34
 
35
#define LOCK_RETRY 1            /* retry lock once a second */
36
#define LOCK_PATIENCE 1200      /* try about twenty minutes before forcing */
37
 
38
/* acquire a lock on a file */
39
local int lock(int fd)
40
{
41
    int patience;
42
 
43
    /* try to lock every LOCK_RETRY seconds for LOCK_PATIENCE seconds */
44
    patience = LOCK_PATIENCE;
45
    do {
46
        if (flock(fd, LOCK_EX + LOCK_NB) == 0)
47
            return 0;
48
        (void)sleep(LOCK_RETRY);
49
        patience -= LOCK_RETRY;
50
    } while (patience > 0);
51
 
52
    /* we've run out of patience -- give up */
53
    return -1;
54
}
55
 
56
/* release lock */
57
local void unlock(int fd)
58
{
59
    (void)flock(fd, LOCK_UN);
60
}
61
 
62
/* release a log object */
63
local void log_clean(gz_log *log)
64
{
65
    unlock(log->fd);
66
    (void)close(log->fd);
67
    free(log);
68
}
69
 
70
/* read an unsigned long from a byte buffer little-endian */
71
local unsigned long make_ulg(unsigned char *buf)
72
{
73
    int n;
74
    unsigned long val;
75
 
76
    val = (unsigned long)(*buf++);
77
    for (n = 8; n < 32; n += 8)
78
        val += (unsigned long)(*buf++) << n;
79
    return val;
80
}
81
 
82
/* read an off_t from a byte buffer little-endian */
83
local off_t make_off(unsigned char *buf)
84
{
85
    int n;
86
    off_t val;
87
 
88
    val = (off_t)(*buf++);
89
    for (n = 8; n < 64; n += 8)
90
        val += (off_t)(*buf++) << n;
91
    return val;
92
}
93
 
94
/* write an unsigned long little-endian to byte buffer */
95
local void dice_ulg(unsigned long val, unsigned char *buf)
96
{
97
    int n;
98
 
99
    for (n = 0; n < 4; n++) {
100
        *buf++ = val & 0xff;
101
        val >>= 8;
102
    }
103
}
104
 
105
/* write an off_t little-endian to byte buffer */
106
local void dice_off(off_t val, unsigned char *buf)
107
{
108
    int n;
109
 
110
    for (n = 0; n < 8; n++) {
111
        *buf++ = val & 0xff;
112
        val >>= 8;
113
    }
114
}
115
 
116
/* initial, empty gzip file for appending */
117
local char empty_gz[] = {
118
    0x1f, 0x8b,                 /* magic gzip id */
119
    8,                          /* compression method is deflate */
120
    4,                          /* there is an extra field */
121
    0, 0, 0, 0,                 /* no modification time provided */
122
    0, 0xff,                    /* no extra flags, no OS */
123
    20, 0, 'a', 'p', 16, 0,     /* extra field with "ap" subfield */
124
    32, 0, 0, 0, 0, 0, 0, 0,    /* offset of uncompressed data */
125
    32, 0, 0, 0, 0, 0, 0, 0,    /* offset of last block */
126
    1, 0, 0, 0xff, 0xff,        /* empty stored block (last) */
127
    0, 0, 0, 0,                 /* crc */
128
    0, 0, 0, 0                  /* uncompressed length */
129
};
130
 
131
/* initialize a log object with locking */
132
void *gzlog_open(char *path)
133
{
134
    unsigned xlen;
135
    unsigned char temp[20];
136
    unsigned sub_len;
137
    int good;
138
    gz_log *log;
139
 
140
    /* allocate log structure */
141
    log = malloc(sizeof(gz_log));
142
    if (log == NULL)
143
        return NULL;
144
    log->id = GZLOGID;
145
 
146
    /* open file, creating it if necessary, and locking it */
147
    log->fd = open(path, O_RDWR | O_CREAT, 0600);
148
    if (log->fd < 0) {
149
        free(log);
150
        return NULL;
151
    }
152
    if (lock(log->fd)) {
153
        close(log->fd);
154
        free(log);
155
        return NULL;
156
    }
157
 
158
    /* if file is empty, write new gzip stream */
159
    if (lseek(log->fd, 0, SEEK_END) == 0) {
160
        if (write(log->fd, empty_gz, sizeof(empty_gz)) != sizeof(empty_gz)) {
161
            log_clean(log);
162
            return NULL;
163
        }
164
    }
165
 
166
    /* check gzip header */
167
    (void)lseek(log->fd, 0, SEEK_SET);
168
    if (read(log->fd, temp, 12) != 12 || temp[0] != 0x1f ||
169
        temp[1] != 0x8b || temp[2] != 8 || (temp[3] & 4) == 0) {
170
        log_clean(log);
171
        return NULL;
172
    }
173
 
174
    /* process extra field to find "ap" sub-field */
175
    xlen = temp[10] + (temp[11] << 8);
176
    good = 0;
177
    while (xlen) {
178
        if (xlen < 4 || read(log->fd, temp, 4) != 4)
179
            break;
180
        sub_len = temp[2];
181
        sub_len += temp[3] << 8;
182
        xlen -= 4;
183
        if (memcmp(temp, "ap", 2) == 0 && sub_len == 16) {
184
            good = 1;
185
            break;
186
        }
187
        if (xlen < sub_len)
188
            break;
189
        (void)lseek(log->fd, sub_len, SEEK_CUR);
190
        xlen -= sub_len;
191
    }
192
    if (!good) {
193
        log_clean(log);
194
        return NULL;
195
    }
196
 
197
    /* read in "ap" sub-field */
198
    log->extra = lseek(log->fd, 0, SEEK_CUR);
199
    if (read(log->fd, temp, 16) != 16) {
200
        log_clean(log);
201
        return NULL;
202
    }
203
    log->mark_off = make_off(temp);
204
    log->last_off = make_off(temp + 8);
205
 
206
    /* get crc, length of gzip file */
207
    (void)lseek(log->fd, log->last_off, SEEK_SET);
208
    if (read(log->fd, temp, 13) != 13 ||
209
        memcmp(temp, "\001\000\000\377\377", 5) != 0) {
210
        log_clean(log);
211
        return NULL;
212
    }
213
    log->crc = make_ulg(temp + 5);
214
    log->len = make_ulg(temp + 9);
215
 
216
    /* set up to write over empty last block */
217
    (void)lseek(log->fd, log->last_off + 5, SEEK_SET);
218
    log->stored = 0;
219
    return (void *)log;
220
}
221
 
222
/* maximum amount to put in a stored block before starting a new one */
223
#define MAX_BLOCK 16384
224
 
225
/* write a block to a log object */
226
int gzlog_write(void *obj, char *data, size_t len)
227
{
228
    size_t some;
229
    unsigned char temp[5];
230
    gz_log *log;
231
 
232
    /* check object */
233
    log = (gz_log *)obj;
234
    if (log == NULL || log->id != GZLOGID)
235
        return 1;
236
 
237
    /* write stored blocks until all of the input is written */
238
    do {
239
        some = MAX_BLOCK - log->stored;
240
        if (some > len)
241
            some = len;
242
        if (write(log->fd, data, some) != some)
243
            return 1;
244
        log->crc = crc32(log->crc, data, some);
245
        log->len += some;
246
        len -= some;
247
        data += some;
248
        log->stored += some;
249
 
250
        /* if the stored block is full, end it and start another */
251
        if (log->stored == MAX_BLOCK) {
252
            (void)lseek(log->fd, log->last_off, SEEK_SET);
253
            temp[0] = 0;
254
            dice_ulg(log->stored + ((unsigned long)(~log->stored) << 16),
255
                     temp + 1);
256
            if (write(log->fd, temp, 5) != 5)
257
                return 1;
258
            log->last_off = lseek(log->fd, log->stored, SEEK_CUR);
259
            (void)lseek(log->fd, 5, SEEK_CUR);
260
            log->stored = 0;
261
        }
262
    } while (len);
263
    return 0;
264
}
265
 
266
/* recompress the remaining stored deflate data in place */
267
local int recomp(gz_log *log)
268
{
269
    z_stream strm;
270
    size_t len, max;
271
    unsigned char *in;
272
    unsigned char *out;
273
    unsigned char temp[16];
274
 
275
    /* allocate space and read it all in (it's around 1 MB) */
276
    len = log->last_off - log->mark_off;
277
    max = len + (len >> 12) + (len >> 14) + 11;
278
    out = malloc(max);
279
    if (out == NULL)
280
        return 1;
281
    in = malloc(len);
282
    if (in == NULL) {
283
        free(out);
284
        return 1;
285
    }
286
    (void)lseek(log->fd, log->mark_off, SEEK_SET);
287
    if (read(log->fd, in, len) != len) {
288
        free(in);
289
        free(out);
290
        return 1;
291
    }
292
 
293
    /* recompress in memory, decoding stored data as we go */
294
    /* note: this assumes that unsigned is four bytes or more */
295
    /*       consider not making that assumption */
296
    strm.zalloc = Z_NULL;
297
    strm.zfree = Z_NULL;
298
    strm.opaque = Z_NULL;
299
    if (deflateInit2(&strm, Z_BEST_COMPRESSION, Z_DEFLATED, -15, 8,
300
        Z_DEFAULT_STRATEGY) != Z_OK) {
301
        free(in);
302
        free(out);
303
        return 1;
304
    }
305
    strm.next_in = in;
306
    strm.avail_out = max;
307
    strm.next_out = out;
308
    while (len >= 5) {
309
        if (strm.next_in[0] != 0)
310
            break;
311
        strm.avail_in = strm.next_in[1] + (strm.next_in[2] << 8);
312
        strm.next_in += 5;
313
        len -= 5;
314
        if (strm.avail_in != 0) {
315
            if (len < strm.avail_in)
316
                break;
317
            len -= strm.avail_in;
318
            (void)deflate(&strm, Z_NO_FLUSH);
319
            if (strm.avail_in != 0 || strm.avail_out == 0)
320
                break;
321
        }
322
    }
323
    (void)deflate(&strm, Z_SYNC_FLUSH);
324
    (void)deflateEnd(&strm);
325
    free(in);
326
    if (len != 0 || strm.avail_out == 0) {
327
        free(out);
328
        return 1;
329
    }
330
 
331
    /* overwrite stored data with compressed data */
332
    (void)lseek(log->fd, log->mark_off, SEEK_SET);
333
    len = max - strm.avail_out;
334
    if (write(log->fd, out, len) != len) {
335
        free(out);
336
        return 1;
337
    }
338
    free(out);
339
 
340
    /* write last empty block, crc, and length */
341
    log->mark_off = log->last_off = lseek(log->fd, 0, SEEK_CUR);
342
    temp[0] = 1;
343
    dice_ulg(0xffffL << 16, temp + 1);
344
    dice_ulg(log->crc, temp + 5);
345
    dice_ulg(log->len, temp + 9);
346
    if (write(log->fd, temp, 13) != 13)
347
        return 1;
348
 
349
    /* truncate file to discard remaining stored data and old trailer */
350
    ftruncate(log->fd, lseek(log->fd, 0, SEEK_CUR));
351
 
352
    /* update extra field to point to new last empty block */
353
    (void)lseek(log->fd, log->extra, SEEK_SET);
354
    dice_off(log->mark_off, temp);
355
    dice_off(log->last_off, temp + 8);
356
    if (write(log->fd, temp, 16) != 16)
357
        return 1;
358
    return 0;
359
}
360
 
361
/* maximum accumulation of stored blocks before compressing */
362
#define MAX_STORED 1048576
363
 
364
/* close log object */
365
int gzlog_close(void *obj)
366
{
367
    unsigned char temp[8];
368
    gz_log *log;
369
 
370
    /* check object */
371
    log = (gz_log *)obj;
372
    if (log == NULL || log->id != GZLOGID)
373
        return 1;
374
 
375
    /* go to start of most recent block being written */
376
    (void)lseek(log->fd, log->last_off, SEEK_SET);
377
 
378
    /* if some stuff was put there, update block */
379
    if (log->stored) {
380
        temp[0] = 0;
381
        dice_ulg(log->stored + ((unsigned long)(~log->stored) << 16),
382
                 temp + 1);
383
        if (write(log->fd, temp, 5) != 5)
384
            return 1;
385
        log->last_off = lseek(log->fd, log->stored, SEEK_CUR);
386
    }
387
 
388
    /* write last block (empty) */
389
    if (write(log->fd, "\001\000\000\377\377", 5) != 5)
390
        return 1;
391
 
392
    /* write updated crc and uncompressed length */
393
    dice_ulg(log->crc, temp);
394
    dice_ulg(log->len, temp + 4);
395
    if (write(log->fd, temp, 8) != 8)
396
        return 1;
397
 
398
    /* put offset of that last block in gzip extra block */
399
    (void)lseek(log->fd, log->extra + 8, SEEK_SET);
400
    dice_off(log->last_off, temp);
401
    if (write(log->fd, temp, 8) != 8)
402
        return 1;
403
 
404
    /* if more than 1 MB stored, then time to compress it */
405
    if (log->last_off - log->mark_off > MAX_STORED) {
406
        if (recomp(log))
407
            return 1;
408
    }
409
 
410
    /* unlock and close file */
411
    log_clean(log);
412
    return 0;
413
}

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