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334 lines (277 loc) · 6.2 KB
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/*
* fResync - MPEG frame-resync utility
* Copyright(c) 2004 of wave++ (Yuri D'Elia) <wavexx@thregr.org>
* Distributed under GNU LGPL without ANY warranty.
*/
// local headers
#include "fIcy.hh"
#include "msg.hh"
#include "mpeg.hh"
#include "copy.hh"
// system headers
#include <fstream>
using std::ifstream;
using std::ofstream;
#include <iostream>
using std::cout;
using std::cerr;
#include <memory>
using std::auto_ptr;
// c system headers
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
/*
* Parameters handling
*/
struct params_t
{
const char* file;
size_t framelen;
size_t maxframes;
bool buffered;
bool simulate;
bool help;
};
bool
parse_params(params_t& buf, int argc, char* const argv[])
{
// real values
int arg;
while((arg = getopt(argc, argv, "bn:m:svh")) != -1)
switch(arg)
{
case 'b':
buf.buffered = true;
break;
case 'n':
buf.maxframes = strtoul(optarg, NULL, 0);
break;
case 'm':
buf.framelen = strtoul(optarg, NULL, 0);
break;
case 's':
buf.simulate = true;
break;
case 'h':
buf.help = true;
break;
case 'v':
verbose = true;
break;
}
argc -= optind;
buf.file = argv[optind];
return (!buf.file);
}
void
show_help()
{
cout << prg << fIcy::fResyncHelp << prg << " v" << fIcy::version <<
" is\n" << fIcy::copyright;
}
bool
init(params_t& buf, int argc, char* argv[])
{
// defaults
prg = argv[0];
buf.buffered = false;
buf.framelen = fIcy::frameLen;
buf.maxframes = fIcy::maxFrames;
verbose = buf.simulate = buf.help = false;
// arguments
bool ret(parse_params(buf, argc, argv));
return (ret && !buf.help);
}
/*
* File truncation utilities
*/
struct region_t
{
size_t start;
size_t size;
};
bool
truncate(const char* file, const region_t& reg)
{
// check whether truncate can be used
if(reg.start == 0)
return truncate(file, reg.size);
// re-open the input file and output file
ifstream in(file);
if(!in || unlink(file))
return true;
ofstream out(file);
if(!out)
return true;
// skip garbage and copy the stream
in.seekg(reg.start);
return copy(out, in, reg.size);
}
/*
* Implementation
*/
bool
search_sync(ifstream& fd, const params_t& params, region_t& reg)
{
// create the buffer as the double of the maximal space possibly needed
size_t mlen(params.framelen * params.maxframes * 2);
auto_ptr<char> buf(new char[mlen]);
// beginning
fd.seekg(0);
fd.read(buf.get(), mlen);
if(!fd)
return true;
reg.start = mpeg::sync_forward(buf.get(), mlen, params.maxframes);
if(reg.start == mlen)
return true;
// end
fd.seekg(-static_cast<ifstream::off_type>(mlen), std::ios_base::end);
size_t pos(fd.tellg());
fd.read(buf.get(), mlen);
if(!fd)
return true;
size_t end(mpeg::sync_reverse(buf.get(), mlen, params.maxframes));
if(!end || (pos + end) <= reg.start)
return true;
reg.size = (pos + end) - reg.start;
return false;
}
bool
search_sync(const char* buf, size_t len, const params_t& params, region_t& reg)
{
// create the buffer as the double of the maximal space possibly needed
size_t mlen(params.framelen * params.maxframes * 2);
if(len < mlen)
mlen = len;
// beginning
reg.start = mpeg::sync_forward(buf, mlen, params.maxframes);
if(reg.start == mlen)
return true;
// end
size_t pos(len - mlen);
size_t end(mpeg::sync_reverse(buf + pos, mlen, params.maxframes));
if(!end || (pos + end) <= reg.start)
return true;
reg.size = (pos + end) - reg.start;
return false;
}
int
resync_buf(const params_t& params)
{
// open the file
ifstream fd(params.file, (params.simulate?
std::ios_base::in: (std::ios_base::in | std::ios_base::out)));
if(!fd)
{
err("cannot open %s for read/write", params.file);
return Exit::fail;
}
// search the offsets
region_t reg;
if(search_sync(fd, params, reg))
{
err("cannot resync %s, try increasing frame size", params.file);
return Exit::fail;
}
msg("sync found at %lu for %lu bytes", reg.start, reg.size);
// save file size
fd.seekg(0, std::ios_base::end);
size_t size(fd.tellg());
fd.close();
// sync the file
if(params.simulate)
{
// offsets only
cout << reg.start << " " << reg.size << std::endl;
}
else if(reg.start != 0 || reg.size != size)
{
// the file needs to be modified
if(truncate(params.file, reg))
{
err("cannot truncate %s", params.file);
return Exit::fail;
}
}
else
msg("no resync needed");
return Exit::success;
}
int
resync_
7ADC
mmap(const params_t& params)
{
// open the file
int fd = open(params.file, O_RDWR);
if(fd == -1)
{
err("cannot open %s for read/write", params.file);
return Exit::fail;
}
// file size
struct stat st;
if(fstat(fd, &st))
{
err("cannot stat %s", params.file);
return Exit::fail;
}
// mmap the file
char* addr = reinterpret_cast<char*>(mmap(NULL, st.st_size,
(PROT_READ | PROT_WRITE), MAP_SHARED, fd, 0));
if(!addr)
{
close(fd);
err("cannot mmap %s", params.file);
return Exit::fail;
}
// search the offsets
bool fail;
region_t reg;
if((fail = search_sync(addr, st.st_size, params, reg)))
err("cannot resync %s, try increasing frame size", params.file);
else
{
msg("sync found at %lu for %lu bytes", reg.start, reg.size);
if(reg.start != 0 || reg.size != static_cast<size_t>(st.st_size))
{
// non-zero offsets
if(reg.start != 0)
{
memmove(addr, addr + reg.start, reg.size);
reg.start = 0;
}
// final truncation
if((fail = ftruncate(fd, reg.size)))
err("cannot truncate %s", params.file);
}
else
msg("no resync needed");
}
// free resources
munmap(addr, st.st_size);
close(fd);
return (fail? Exit::fail: Exit::success);
}
int
main(int argc, char* argv[])
{
// initialize
params_t params;
if(init(params, argc, argv))
{
err("bad parameters; see %s -h", prg);
return Exit::args;
}
if(params.help)
{
show_help();
return Exit::args;
}
return (params.buffered || params.simulate?
resync_buf(params):
resync_mmap(params));
}