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504 lines
17 KiB
504 lines
17 KiB
/* gzappend -- command to append to a gzip file |
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Copyright (C) 2003, 2012 Mark Adler, all rights reserved |
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version 1.2, 11 Oct 2012 |
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This software is provided 'as-is', without any express or implied |
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warranty. In no event will the author be held liable for any damages |
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arising from the use of this software. |
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Permission is granted to anyone to use this software for any purpose, |
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including commercial applications, and to alter it and redistribute it |
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freely, subject to the following restrictions: |
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1. The origin of this software must not be misrepresented; you must not |
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claim that you wrote the original software. If you use this software |
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in a product, an acknowledgment in the product documentation would be |
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appreciated but is not required. |
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2. Altered source versions must be plainly marked as such, and must not be |
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misrepresented as being the original software. |
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3. This notice may not be removed or altered from any source distribution. |
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Mark Adler madler@alumni.caltech.edu |
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*/ |
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/* |
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* Change history: |
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* |
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* 1.0 19 Oct 2003 - First version |
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* 1.1 4 Nov 2003 - Expand and clarify some comments and notes |
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* - Add version and copyright to help |
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* - Send help to stdout instead of stderr |
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* - Add some preemptive typecasts |
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* - Add L to constants in lseek() calls |
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* - Remove some debugging information in error messages |
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* - Use new data_type definition for zlib 1.2.1 |
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* - Simplfy and unify file operations |
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* - Finish off gzip file in gztack() |
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* - Use deflatePrime() instead of adding empty blocks |
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* - Keep gzip file clean on appended file read errors |
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* - Use in-place rotate instead of auxiliary buffer |
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* (Why you ask? Because it was fun to write!) |
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* 1.2 11 Oct 2012 - Fix for proper z_const usage |
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* - Check for input buffer malloc failure |
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*/ |
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/* |
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gzappend takes a gzip file and appends to it, compressing files from the |
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command line or data from stdin. The gzip file is written to directly, to |
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avoid copying that file, in case it's large. Note that this results in the |
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unfriendly behavior that if gzappend fails, the gzip file is corrupted. |
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This program was written to illustrate the use of the new Z_BLOCK option of |
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zlib 1.2.x's inflate() function. This option returns from inflate() at each |
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block boundary to facilitate locating and modifying the last block bit at |
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the start of the final deflate block. Also whether using Z_BLOCK or not, |
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another required feature of zlib 1.2.x is that inflate() now provides the |
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number of unusued bits in the last input byte used. gzappend will not work |
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with versions of zlib earlier than 1.2.1. |
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gzappend first decompresses the gzip file internally, discarding all but |
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the last 32K of uncompressed data, and noting the location of the last block |
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bit and the number of unused bits in the last byte of the compressed data. |
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The gzip trailer containing the CRC-32 and length of the uncompressed data |
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is verified. This trailer will be later overwritten. |
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Then the last block bit is cleared by seeking back in the file and rewriting |
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the byte that contains it. Seeking forward, the last byte of the compressed |
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data is saved along with the number of unused bits to initialize deflate. |
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A deflate process is initialized, using the last 32K of the uncompressed |
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data from the gzip file to initialize the dictionary. If the total |
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uncompressed data was less than 32K, then all of it is used to initialize |
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the dictionary. The deflate output bit buffer is also initialized with the |
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last bits from the original deflate stream. From here on, the data to |
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append is simply compressed using deflate, and written to the gzip file. |
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When that is complete, the new CRC-32 and uncompressed length are written |
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as the trailer of the gzip file. |
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*/ |
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#include <stdio.h> |
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#include <stdlib.h> |
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#include <string.h> |
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#include <fcntl.h> |
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#include <unistd.h> |
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#include "zlib.h" |
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#define local static |
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#define LGCHUNK 14 |
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#define CHUNK (1U << LGCHUNK) |
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#define DSIZE 32768U |
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/* print an error message and terminate with extreme prejudice */ |
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local void bye(char *msg1, char *msg2) |
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{ |
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fprintf(stderr, "gzappend error: %s%s\n", msg1, msg2); |
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exit(1); |
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} |
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/* return the greatest common divisor of a and b using Euclid's algorithm, |
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modified to be fast when one argument much greater than the other, and |
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coded to avoid unnecessary swapping */ |
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local unsigned gcd(unsigned a, unsigned b) |
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{ |
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unsigned c; |
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while (a && b) |
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if (a > b) { |
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c = b; |
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while (a - c >= c) |
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c <<= 1; |
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a -= c; |
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} |
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else { |
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c = a; |
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while (b - c >= c) |
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c <<= 1; |
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b -= c; |
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} |
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return a + b; |
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} |
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/* rotate list[0..len-1] left by rot positions, in place */ |
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local void rotate(unsigned char *list, unsigned len, unsigned rot) |
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{ |
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unsigned char tmp; |
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unsigned cycles; |
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unsigned char *start, *last, *to, *from; |
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/* normalize rot and handle degenerate cases */ |
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if (len < 2) return; |
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if (rot >= len) rot %= len; |
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if (rot == 0) return; |
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/* pointer to last entry in list */ |
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last = list + (len - 1); |
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/* do simple left shift by one */ |
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if (rot == 1) { |
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tmp = *list; |
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memmove(list, list + 1, len - 1); |
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*last = tmp; |
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return; |
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} |
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/* do simple right shift by one */ |
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if (rot == len - 1) { |
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tmp = *last; |
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memmove(list + 1, list, len - 1); |
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*list = tmp; |
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return; |
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} |
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/* otherwise do rotate as a set of cycles in place */ |
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cycles = gcd(len, rot); /* number of cycles */ |
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do { |
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start = from = list + cycles; /* start index is arbitrary */ |
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tmp = *from; /* save entry to be overwritten */ |
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for (;;) { |
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to = from; /* next step in cycle */ |
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from += rot; /* go right rot positions */ |
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if (from > last) from -= len; /* (pointer better not wrap) */ |
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if (from == start) break; /* all but one shifted */ |
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*to = *from; /* shift left */ |
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} |
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*to = tmp; /* complete the circle */ |
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} while (--cycles); |
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} |
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/* structure for gzip file read operations */ |
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typedef struct { |
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int fd; /* file descriptor */ |
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int size; /* 1 << size is bytes in buf */ |
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unsigned left; /* bytes available at next */ |
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unsigned char *buf; /* buffer */ |
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z_const unsigned char *next; /* next byte in buffer */ |
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char *name; /* file name for error messages */ |
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} file; |
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/* reload buffer */ |
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local int readin(file *in) |
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{ |
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int len; |
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len = read(in->fd, in->buf, 1 << in->size); |
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if (len == -1) bye("error reading ", in->name); |
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in->left = (unsigned)len; |
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in->next = in->buf; |
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return len; |
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} |
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/* read from file in, exit if end-of-file */ |
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local int readmore(file *in) |
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{ |
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if (readin(in) == 0) bye("unexpected end of ", in->name); |
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return 0; |
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} |
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#define read1(in) (in->left == 0 ? readmore(in) : 0, \ |
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in->left--, *(in->next)++) |
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/* skip over n bytes of in */ |
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local void skip(file *in, unsigned n) |
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{ |
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unsigned bypass; |
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if (n > in->left) { |
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n -= in->left; |
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bypass = n & ~((1U << in->size) - 1); |
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if (bypass) { |
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if (lseek(in->fd, (off_t)bypass, SEEK_CUR) == -1) |
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bye("seeking ", in->name); |
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n -= bypass; |
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} |
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readmore(in); |
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if (n > in->left) |
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bye("unexpected end of ", in->name); |
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} |
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in->left -= n; |
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in->next += n; |
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} |
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/* read a four-byte unsigned integer, little-endian, from in */ |
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unsigned long read4(file *in) |
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{ |
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unsigned long val; |
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val = read1(in); |
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val += (unsigned)read1(in) << 8; |
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val += (unsigned long)read1(in) << 16; |
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val += (unsigned long)read1(in) << 24; |
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return val; |
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} |
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/* skip over gzip header */ |
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local void gzheader(file *in) |
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{ |
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int flags; |
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unsigned n; |
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if (read1(in) != 31 || read1(in) != 139) bye(in->name, " not a gzip file"); |
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if (read1(in) != 8) bye("unknown compression method in", in->name); |
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flags = read1(in); |
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if (flags & 0xe0) bye("unknown header flags set in", in->name); |
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skip(in, 6); |
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if (flags & 4) { |
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n = read1(in); |
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n += (unsigned)(read1(in)) << 8; |
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skip(in, n); |
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} |
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if (flags & 8) while (read1(in) != 0) ; |
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if (flags & 16) while (read1(in) != 0) ; |
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if (flags & 2) skip(in, 2); |
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} |
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/* decompress gzip file "name", return strm with a deflate stream ready to |
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continue compression of the data in the gzip file, and return a file |
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descriptor pointing to where to write the compressed data -- the deflate |
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stream is initialized to compress using level "level" */ |
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local int gzscan(char *name, z_stream *strm, int level) |
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{ |
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int ret, lastbit, left, full; |
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unsigned have; |
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unsigned long crc, tot; |
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unsigned char *window; |
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off_t lastoff, end; |
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file gz; |
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/* open gzip file */ |
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gz.name = name; |
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gz.fd = open(name, O_RDWR, 0); |
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if (gz.fd == -1) bye("cannot open ", name); |
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gz.buf = malloc(CHUNK); |
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if (gz.buf == NULL) bye("out of memory", ""); |
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gz.size = LGCHUNK; |
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gz.left = 0; |
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/* skip gzip header */ |
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gzheader(&gz); |
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/* prepare to decompress */ |
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window = malloc(DSIZE); |
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if (window == NULL) bye("out of memory", ""); |
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strm->zalloc = Z_NULL; |
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strm->zfree = Z_NULL; |
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strm->opaque = Z_NULL; |
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ret = inflateInit2(strm, -15); |
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if (ret != Z_OK) bye("out of memory", " or library mismatch"); |
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/* decompress the deflate stream, saving append information */ |
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lastbit = 0; |
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lastoff = lseek(gz.fd, 0L, SEEK_CUR) - gz.left; |
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left = 0; |
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strm->avail_in = gz.left; |
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strm->next_in = gz.next; |
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crc = crc32(0L, Z_NULL, 0); |
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have = full = 0; |
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do { |
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/* if needed, get more input */ |
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if (strm->avail_in == 0) { |
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readmore(&gz); |
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strm->avail_in = gz.left; |
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strm->next_in = gz.next; |
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} |
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/* set up output to next available section of sliding window */ |
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strm->avail_out = DSIZE - have; |
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strm->next_out = window + have; |
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/* inflate and check for errors */ |
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ret = inflate(strm, Z_BLOCK); |
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if (ret == Z_STREAM_ERROR) bye("internal stream error!", ""); |
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if (ret == Z_MEM_ERROR) bye("out of memory", ""); |
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if (ret == Z_DATA_ERROR) |
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bye("invalid compressed data--format violated in", name); |
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/* update crc and sliding window pointer */ |
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crc = crc32(crc, window + have, DSIZE - have - strm->avail_out); |
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if (strm->avail_out) |
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have = DSIZE - strm->avail_out; |
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else { |
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have = 0; |
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full = 1; |
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} |
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/* process end of block */ |
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if (strm->data_type & 128) { |
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if (strm->data_type & 64) |
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left = strm->data_type & 0x1f; |
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else { |
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lastbit = strm->data_type & 0x1f; |
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lastoff = lseek(gz.fd, 0L, SEEK_CUR) - strm->avail_in; |
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} |
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} |
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} while (ret != Z_STREAM_END); |
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inflateEnd(strm); |
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gz.left = strm->avail_in; |
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gz.next = strm->next_in; |
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/* save the location of the end of the compressed data */ |
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end = lseek(gz.fd, 0L, SEEK_CUR) - gz.left; |
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/* check gzip trailer and save total for deflate */ |
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if (crc != read4(&gz)) |
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bye("invalid compressed data--crc mismatch in ", name); |
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tot = strm->total_out; |
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if ((tot & 0xffffffffUL) != read4(&gz)) |
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bye("invalid compressed data--length mismatch in", name); |
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/* if not at end of file, warn */ |
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if (gz.left || readin(&gz)) |
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fprintf(stderr, |
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"gzappend warning: junk at end of gzip file overwritten\n"); |
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/* clear last block bit */ |
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lseek(gz.fd, lastoff - (lastbit != 0), SEEK_SET); |
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if (read(gz.fd, gz.buf, 1) != 1) bye("reading after seek on ", name); |
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*gz.buf = (unsigned char)(*gz.buf ^ (1 << ((8 - lastbit) & 7))); |
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lseek(gz.fd, -1L, SEEK_CUR); |
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if (write(gz.fd, gz.buf, 1) != 1) bye("writing after seek to ", name); |
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/* if window wrapped, build dictionary from window by rotating */ |
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if (full) { |
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rotate(window, DSIZE, have); |
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have = DSIZE; |
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} |
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/* set up deflate stream with window, crc, total_in, and leftover bits */ |
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ret = deflateInit2(strm, level, Z_DEFLATED, -15, 8, Z_DEFAULT_STRATEGY); |
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if (ret != Z_OK) bye("out of memory", ""); |
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deflateSetDictionary(strm, window, have); |
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strm->adler = crc; |
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strm->total_in = tot; |
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if (left) { |
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lseek(gz.fd, --end, SEEK_SET); |
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if (read(gz.fd, gz.buf, 1) != 1) bye("reading after seek on ", name); |
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deflatePrime(strm, 8 - left, *gz.buf); |
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} |
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lseek(gz.fd, end, SEEK_SET); |
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/* clean up and return */ |
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free(window); |
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free(gz.buf); |
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return gz.fd; |
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} |
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/* append file "name" to gzip file gd using deflate stream strm -- if last |
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is true, then finish off the deflate stream at the end */ |
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local void gztack(char *name, int gd, z_stream *strm, int last) |
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{ |
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int fd, len, ret; |
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unsigned left; |
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unsigned char *in, *out; |
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/* open file to compress and append */ |
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fd = 0; |
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if (name != NULL) { |
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fd = open(name, O_RDONLY, 0); |
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if (fd == -1) |
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fprintf(stderr, "gzappend warning: %s not found, skipping ...\n", |
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name); |
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} |
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/* allocate buffers */ |
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in = malloc(CHUNK); |
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out = malloc(CHUNK); |
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if (in == NULL || out == NULL) bye("out of memory", ""); |
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/* compress input file and append to gzip file */ |
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do { |
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/* get more input */ |
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len = read(fd, in, CHUNK); |
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if (len == -1) { |
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fprintf(stderr, |
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"gzappend warning: error reading %s, skipping rest ...\n", |
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name); |
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len = 0; |
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} |
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strm->avail_in = (unsigned)len; |
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strm->next_in = in; |
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if (len) strm->adler = crc32(strm->adler, in, (unsigned)len); |
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/* compress and write all available output */ |
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do { |
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strm->avail_out = CHUNK; |
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strm->next_out = out; |
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ret = deflate(strm, last && len == 0 ? Z_FINISH : Z_NO_FLUSH); |
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left = CHUNK - strm->avail_out; |
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while (left) { |
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len = write(gd, out + CHUNK - strm->avail_out - left, left); |
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if (len == -1) bye("writing gzip file", ""); |
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left -= (unsigned)len; |
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} |
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} while (strm->avail_out == 0 && ret != Z_STREAM_END); |
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} while (len != 0); |
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/* write trailer after last entry */ |
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if (last) { |
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deflateEnd(strm); |
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out[0] = (unsigned char)(strm->adler); |
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out[1] = (unsigned char)(strm->adler >> 8); |
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out[2] = (unsigned char)(strm->adler >> 16); |
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out[3] = (unsigned char)(strm->adler >> 24); |
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out[4] = (unsigned char)(strm->total_in); |
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out[5] = (unsigned char)(strm->total_in >> 8); |
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out[6] = (unsigned char)(strm->total_in >> 16); |
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out[7] = (unsigned char)(strm->total_in >> 24); |
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len = 8; |
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do { |
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ret = write(gd, out + 8 - len, len); |
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if (ret == -1) bye("writing gzip file", ""); |
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len -= ret; |
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} while (len); |
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close(gd); |
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} |
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/* clean up and return */ |
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free(out); |
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free(in); |
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if (fd > 0) close(fd); |
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} |
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/* process the compression level option if present, scan the gzip file, and |
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append the specified files, or append the data from stdin if no other file |
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names are provided on the command line -- the gzip file must be writable |
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and seekable */ |
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int main(int argc, char **argv) |
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{ |
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int gd, level; |
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z_stream strm; |
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/* ignore command name */ |
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argc--; argv++; |
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/* provide usage if no arguments */ |
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if (*argv == NULL) { |
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printf( |
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"gzappend 1.2 (11 Oct 2012) Copyright (C) 2003, 2012 Mark Adler\n" |
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); |
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printf( |
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"usage: gzappend [-level] file.gz [ addthis [ andthis ... ]]\n"); |
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return 0; |
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} |
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/* set compression level */ |
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level = Z_DEFAULT_COMPRESSION; |
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if (argv[0][0] == '-') { |
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if (argv[0][1] < '0' || argv[0][1] > '9' || argv[0][2] != 0) |
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bye("invalid compression level", ""); |
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level = argv[0][1] - '0'; |
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if (*++argv == NULL) bye("no gzip file name after options", ""); |
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} |
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/* prepare to append to gzip file */ |
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gd = gzscan(*argv++, &strm, level); |
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/* append files on command line, or from stdin if none */ |
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if (*argv == NULL) |
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gztack(NULL, gd, &strm, 1); |
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else |
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do { |
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gztack(*argv, gd, &strm, argv[1] == NULL); |
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} while (*++argv != NULL); |
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return 0; |
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}
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