448 lines
14 KiB
C
448 lines
14 KiB
C
/* gzjoin -- command to join gzip files into one gzip file
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Copyright (C) 2004 Mark Adler, all rights reserved
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version 1.0, 11 Dec 2004
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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 11 Dec 2004 - First version
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* 1.1 12 Jun 2005 - Changed ssize_t to long for portability
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*/
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/*
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gzjoin takes one or more gzip files on the command line and writes out a
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single gzip file that will uncompress to the concatenation of the
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uncompressed data from the individual gzip files. gzjoin does this without
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having to recompress any of the data and without having to calculate a new
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crc32 for the concatenated uncompressed data. gzjoin does however have to
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decompress all of the input data in order to find the bits in the compressed
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data that need to be modified to concatenate the streams.
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gzjoin does not do an integrity check on the input gzip files other than
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checking the gzip header and decompressing the compressed data. They are
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otherwise assumed to be complete and correct.
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Each joint between gzip files removes at least 18 bytes of previous trailer
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and subsequent header, and inserts an average of about three bytes to the
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compressed data in order to connect the streams. The output gzip file
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has a minimal ten-byte gzip header with no file name or modification time.
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This program was written to illustrate the use of the Z_BLOCK option of
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inflate() and the crc32_combine() function. gzjoin will not compile with
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versions of zlib earlier than 1.2.3.
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*/
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#include <stdio.h> /* fputs(), fprintf(), fwrite(), putc() */
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#include <stdlib.h> /* exit(), malloc(), free() */
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#include <fcntl.h> /* open() */
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#include <unistd.h> /* close(), read(), lseek() */
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#include "zlib.h"
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/* crc32(), crc32_combine(), inflateInit2(), inflate(), inflateEnd() */
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#define local static
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/* exit with an error (return a value to allow use in an expression) */
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local int bail(char *why1, char *why2)
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{
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fprintf(stderr, "gzjoin error: %s%s, output incomplete\n", why1, why2);
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exit(1);
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return 0;
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}
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/* -- simple buffered file input with access to the buffer -- */
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#define CHUNK 32768 /* must be a power of two and fit in unsigned */
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/* bin buffered input file type */
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typedef struct {
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char *name; /* name of file for error messages */
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int fd; /* file descriptor */
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unsigned left; /* bytes remaining at next */
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unsigned char *next; /* next byte to read */
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unsigned char *buf; /* allocated buffer of length CHUNK */
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} bin;
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/* close a buffered file and free allocated memory */
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local void bclose(bin *in)
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{
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if (in != NULL) {
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if (in->fd != -1)
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close(in->fd);
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if (in->buf != NULL)
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free(in->buf);
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free(in);
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}
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}
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/* open a buffered file for input, return a pointer to type bin, or NULL on
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failure */
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local bin *bopen(char *name)
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{
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bin *in;
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in = malloc(sizeof(bin));
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if (in == NULL)
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return NULL;
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in->buf = malloc(CHUNK);
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in->fd = open(name, O_RDONLY, 0);
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if (in->buf == NULL || in->fd == -1) {
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bclose(in);
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return NULL;
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}
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in->left = 0;
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in->next = in->buf;
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in->name = name;
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return in;
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}
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/* load buffer from file, return -1 on read error, 0 or 1 on success, with
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1 indicating that end-of-file was reached */
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local int bload(bin *in)
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{
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long len;
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if (in == NULL)
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return -1;
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if (in->left != 0)
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return 0;
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in->next = in->buf;
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do {
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len = (long)read(in->fd, in->buf + in->left, CHUNK - in->left);
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if (len < 0)
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return -1;
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in->left += (unsigned)len;
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} while (len != 0 && in->left < CHUNK);
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return len == 0 ? 1 : 0;
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}
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/* get a byte from the file, bail if end of file */
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#define bget(in) (in->left ? 0 : bload(in), \
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in->left ? (in->left--, *(in->next)++) : \
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bail("unexpected end of file on ", in->name))
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/* get a four-byte little-endian unsigned integer from file */
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local unsigned long bget4(bin *in)
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{
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unsigned long val;
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val = bget(in);
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val += (unsigned long)(bget(in)) << 8;
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val += (unsigned long)(bget(in)) << 16;
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val += (unsigned long)(bget(in)) << 24;
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return val;
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}
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/* skip bytes in file */
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local void bskip(bin *in, unsigned skip)
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{
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/* check pointer */
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if (in == NULL)
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return;
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/* easy case -- skip bytes in buffer */
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if (skip <= in->left) {
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in->left -= skip;
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in->next += skip;
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return;
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}
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/* skip what's in buffer, discard buffer contents */
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skip -= in->left;
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in->left = 0;
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/* seek past multiples of CHUNK bytes */
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if (skip > CHUNK) {
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unsigned left;
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left = skip & (CHUNK - 1);
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if (left == 0) {
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/* exact number of chunks: seek all the way minus one byte to check
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for end-of-file with a read */
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lseek(in->fd, skip - 1, SEEK_CUR);
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if (read(in->fd, in->buf, 1) != 1)
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bail("unexpected end of file on ", in->name);
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return;
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}
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/* skip the integral chunks, update skip with remainder */
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lseek(in->fd, skip - left, SEEK_CUR);
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skip = left;
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}
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/* read more input and skip remainder */
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bload(in);
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if (skip > in->left)
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bail("unexpected end of file on ", in->name);
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in->left -= skip;
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in->next += skip;
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}
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/* -- end of buffered input functions -- */
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/* skip the gzip header from file in */
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local void gzhead(bin *in)
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{
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int flags;
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/* verify gzip magic header and compression method */
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if (bget(in) != 0x1f || bget(in) != 0x8b || bget(in) != 8)
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bail(in->name, " is not a valid gzip file");
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/* get and verify flags */
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flags = bget(in);
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if ((flags & 0xe0) != 0)
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bail("unknown reserved bits set in ", in->name);
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/* skip modification time, extra flags, and os */
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bskip(in, 6);
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/* skip extra field if present */
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if (flags & 4) {
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unsigned len;
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len = bget(in);
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len += (unsigned)(bget(in)) << 8;
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bskip(in, len);
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}
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/* skip file name if present */
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if (flags & 8)
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while (bget(in) != 0)
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;
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/* skip comment if present */
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if (flags & 16)
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while (bget(in) != 0)
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;
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/* skip header crc if present */
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if (flags & 2)
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bskip(in, 2);
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}
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/* write a four-byte little-endian unsigned integer to out */
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local void put4(unsigned long val, FILE *out)
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{
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putc(val & 0xff, out);
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putc((val >> 8) & 0xff, out);
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putc((val >> 16) & 0xff, out);
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putc((val >> 24) & 0xff, out);
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}
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/* Load up zlib stream from buffered input, bail if end of file */
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local void zpull(z_streamp strm, bin *in)
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{
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if (in->left == 0)
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bload(in);
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if (in->left == 0)
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bail("unexpected end of file on ", in->name);
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strm->avail_in = in->left;
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strm->next_in = in->next;
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}
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/* Write header for gzip file to out and initialize trailer. */
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local void gzinit(unsigned long *crc, unsigned long *tot, FILE *out)
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{
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fwrite("\x1f\x8b\x08\0\0\0\0\0\0\xff", 1, 10, out);
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*crc = crc32(0L, Z_NULL, 0);
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*tot = 0;
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}
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/* Copy the compressed data from name, zeroing the last block bit of the last
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block if clr is true, and adding empty blocks as needed to get to a byte
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boundary. If clr is false, then the last block becomes the last block of
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the output, and the gzip trailer is written. crc and tot maintains the
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crc and length (modulo 2^32) of the output for the trailer. The resulting
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gzip file is written to out. gzinit() must be called before the first call
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of gzcopy() to write the gzip header and to initialize crc and tot. */
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local void gzcopy(char *name, int clr, unsigned long *crc, unsigned long *tot,
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FILE *out)
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{
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int ret; /* return value from zlib functions */
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int pos; /* where the "last block" bit is in byte */
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int last; /* true if processing the last block */
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bin *in; /* buffered input file */
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unsigned char *start; /* start of compressed data in buffer */
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unsigned char *junk; /* buffer for uncompressed data -- discarded */
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z_off_t len; /* length of uncompressed data (support > 4 GB) */
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z_stream strm; /* zlib inflate stream */
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/* open gzip file and skip header */
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in = bopen(name);
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if (in == NULL)
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bail("could not open ", name);
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gzhead(in);
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/* allocate buffer for uncompressed data and initialize raw inflate
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stream */
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junk = malloc(CHUNK);
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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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strm.avail_in = 0;
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strm.next_in = Z_NULL;
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ret = inflateInit2(&strm, -15);
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if (junk == NULL || ret != Z_OK)
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bail("out of memory", "");
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/* inflate and copy compressed data, clear last-block bit if requested */
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len = 0;
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zpull(&strm, in);
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start = strm.next_in;
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last = start[0] & 1;
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if (last && clr)
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start[0] &= ~1;
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strm.avail_out = 0;
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for (;;) {
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/* if input used and output done, write used input and get more */
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if (strm.avail_in == 0 && strm.avail_out != 0) {
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fwrite(start, 1, strm.next_in - start, out);
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start = in->buf;
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in->left = 0;
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zpull(&strm, in);
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}
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/* decompress -- return early when end-of-block reached */
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strm.avail_out = CHUNK;
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strm.next_out = junk;
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ret = inflate(&strm, Z_BLOCK);
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switch (ret) {
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case Z_MEM_ERROR:
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bail("out of memory", "");
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case Z_DATA_ERROR:
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bail("invalid compressed data in ", in->name);
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}
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/* update length of uncompressed data */
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len += CHUNK - strm.avail_out;
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/* check for block boundary (only get this when block copied out) */
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if (strm.data_type & 128) {
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/* if that was the last block, then done */
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if (last)
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break;
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/* number of unused bits in last byte */
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pos = strm.data_type & 7;
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/* find the next last-block bit */
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if (pos != 0) {
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/* next last-block bit is in last used byte */
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pos = 0x100 >> pos;
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last = strm.next_in[-1] & pos;
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if (last && clr)
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strm.next_in[-1] &= ~pos;
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}
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else {
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/* next last-block bit is in next unused byte */
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if (strm.avail_in == 0) {
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/* don't have that byte yet -- get it */
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fwrite(start, 1, strm.next_in - start, out);
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start = in->buf;
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in->left = 0;
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zpull(&strm, in);
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}
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last = strm.next_in[0] & 1;
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if (last && clr)
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strm.next_in[0] &= ~1;
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}
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}
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}
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/* update buffer with unused input */
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in->left = strm.avail_in;
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in->next = strm.next_in;
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/* copy used input, write empty blocks to get to byte boundary */
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pos = strm.data_type & 7;
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fwrite(start, 1, in->next - start - 1, out);
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last = in->next[-1];
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if (pos == 0 || !clr)
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/* already at byte boundary, or last file: write last byte */
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putc(last, out);
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else {
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/* append empty blocks to last byte */
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last &= ((0x100 >> pos) - 1); /* assure unused bits are zero */
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if (pos & 1) {
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/* odd -- append an empty stored block */
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putc(last, out);
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if (pos == 1)
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putc(0, out); /* two more bits in block header */
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fwrite("\0\0\xff\xff", 1, 4, out);
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}
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else {
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/* even -- append 1, 2, or 3 empty fixed blocks */
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switch (pos) {
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case 6:
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putc(last | 8, out);
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last = 0;
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case 4:
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putc(last | 0x20, out);
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last = 0;
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case 2:
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putc(last | 0x80, out);
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putc(0, out);
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}
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}
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}
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/* update crc and tot */
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*crc = crc32_combine(*crc, bget4(in), len);
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*tot += (unsigned long)len;
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/* clean up */
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inflateEnd(&strm);
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free(junk);
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bclose(in);
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/* write trailer if this is the last gzip file */
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if (!clr) {
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put4(*crc, out);
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put4(*tot, out);
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}
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}
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/* join the gzip files on the command line, write result to stdout */
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int main(int argc, char **argv)
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{
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unsigned long crc, tot; /* running crc and total uncompressed length */
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/* skip command name */
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argc--;
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argv++;
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/* show usage if no arguments */
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if (argc == 0) {
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fputs("gzjoin usage: gzjoin f1.gz [f2.gz [f3.gz ...]] > fjoin.gz\n",
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stderr);
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return 0;
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}
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/* join gzip files on command line and write to stdout */
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gzinit(&crc, &tot, stdout);
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while (argc--)
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gzcopy(*argv++, argc, &crc, &tot, stdout);
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/* done */
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return 0;
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}
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