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/*
* zsync - client side rsync over http
* Copyright (C) 2004,2005,2007,2009 Colin Phipps <cph@moria.org.uk>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the Artistic License v2 (see the accompanying
* file COPYING for the full license terms), or, at your option, any later
* version of the same license.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* COPYING file for details.
*/
#include "zsglobal.h"
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include "zlib/zlib.h"
#include <sys/types.h>
#include <sys/stat.h>
#ifdef WITH_DMALLOC
# include <dmalloc.h>
#endif
/* fputlong(filehandle, long)
* Writes a 32bit int as raw bytes in little-endian to the given filehandle.
* Returns 0 if successful; otherwise ferror(filehandle) to see the error */
static int fputlong(FILE * f, unsigned long x) {
int n;
for (n = 0; n < 4; n++) {
if (fputc((int)(x & 0xff), f) == EOF)
return -1;
x >>= 8;
}
return 0;
}
/* time = get_mtime(filehandle)
* Get the mtime of a file from an open filehandle; or 0 if unavailable */
time_t get_mtime(FILE * f) {
struct stat s;
if (fstat(fileno(f), &s) == 0)
return s.st_mtime;
else
return 0;
}
/* filehandle = optimal_gzip(filehandle, out_filename_str, blocksize)
* Constructs a compressed version of the data in the file referenced by the
* supplied filehandle; this is saved in a file with the filename supplied as
* the second parameter. The compressed version is optimised for the zsync
* algorithm with the supplied blocksize. The function returns a handle to the
* compressed file (opened for r+w but rewound to the start of the file,
* ready for reading.
*/
/* Algorithm: simple really. We construct a gzip (have to write header with
* mtime, footer with length and crc; we do a standard zlib compress on the
* content _except_ that we supply one block (of the size that zsync will be
* using) and a Z_PARTIAL_FLUSH at the end of each one, so zlib breaks the
* compression runs at exactly the places zsync will start/stop retrieving data.
*/
FILE *optimal_gzip(FILE * ffin, const char *fout, size_t blocksize) {
time_t mtime = get_mtime(ffin);
/* Open output file (for writing, but also reading so we can return the
* handle for reading by the caller. */
FILE *ffout = fopen(fout, "wb+");
if (!ffout) {
perror("open");
return NULL;
}
/* Write gzip header */
if (fwrite("\x1f\x8b\x08\x00", 4, 1, ffout) != 1) {
perror("write");
return NULL;
}
if (fputlong(ffout, mtime) == -1) {
perror("write");
return NULL;
}
if (fwrite("\x00\x03", 2, 1, ffout) != 1) {
perror("write");
return NULL;
}
{ /* Now write compressed content */
z_stream zs;
unsigned char *inbuf = malloc(blocksize);
unsigned char *outbuf = malloc(blocksize + 500);
int err, r;
unsigned long crc = crc32(0L, Z_NULL, 0);
/* Set up zlib object */
zs.zalloc = Z_NULL;
zs.zfree = Z_NULL;
zs.opaque = NULL;
zs.total_in = 0;
zs.total_out = 0;
/* windowBits is passed < 0 to suppress zlib header */
err = deflateInit2(&zs, 9,
Z_DEFLATED, -MAX_WBITS, 8, Z_DEFAULT_STRATEGY);
/* Until end of file or error */
for (r = 1; r > 0;) {
r = fread(inbuf, 1, blocksize, ffin);
if (r < 0)
break;
/* Maintain running crc (for footer) */
crc = crc32(crc, inbuf, r);
/* Set up compressor for this block */
zs.next_in = inbuf;
zs.avail_in = r;
zs.next_out = outbuf;
zs.avail_out = blocksize + 500;
/* Compress with partial flush at the end of this block
* unless EOF, in which case finish */
err = deflate(&zs, r ? Z_PARTIAL_FLUSH : Z_FINISH);
switch (err) {
case Z_STREAM_END:
case Z_OK:
{
size_t w = zs.next_out - outbuf;
if (w != fwrite(outbuf, 1, w, ffout)) {
perror("write");
r = -1;
}
}
break;
default:
fprintf(stderr, "zlib error: %s (%d)\n", zs.msg, err);
r = -1;
}
}
/* Write gzip footer */
if (fputlong(ffout, crc) == -1) {
perror("write");
return NULL;
}
if (fputlong(ffout, zs.total_in) == -1) {
perror("write");
return NULL;
}
/* Clean up */
fflush(ffout);
free(outbuf);
free(inbuf);
if (fclose(ffin) != 0 || r != 0) {
fclose(ffout);
return NULL;
}
}
/* Return rewound handle on the compressed data to the caller */
rewind(ffout);
return ffout;
}
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