Writing large binary files with boost gzip
Hello all, please help! I'm truly banging my head against the wall here. I am trying to write a function that will allow me to write gzipped binary files (~50 MB) and read them again. I have data in memory. Here's my code for writing: namespace io = boost::iostreams; filename = "c:/test.bin.gz"; //My output file int size = 5000000; //Data size in bytes, ~5 MB //Create filtering_ostream io::filtering_ostream out; //Creates a filtering_ostream called out out.push(io::gzip_compressor()); //Assigns the gzip_compressor to out out.push(io::file_sink(filename)); //Assigns a file sink to out char* memblock = new char [size]; //This is my data. In reality memblock will have been created earlier and filled with real data out.write(memblock, size); //Do the writing delete[] memblock; //Clean up As written above the resulting file, c:/test.bin.gz, is corrupt. If I try to decompress it, either with gzip or winrar, I get an error message. However, if I instead set size = 4000000 (~4 MB) (slightly smaller), the resulting file works just fine. My problem therefore is that my actual size is 50 MB... Please help! Anders (not a real programmer)
AMDG On 04/07/2011 12:09 PM, Anders Knudby wrote:
Hello all, please help! I'm truly banging my head against the wall here. I am trying to write a function that will allow me to write gzipped binary files (~50 MB) and read them again. I have data in memory. Here's my code for writing:
namespace io = boost::iostreams;
filename = "c:/test.bin.gz"; //My output file int size = 5000000; //Data size in bytes, ~5 MB
//Create filtering_ostream io::filtering_ostream out; //Creates a filtering_ostream called out out.push(io::gzip_compressor()); //Assigns the gzip_compressor to out out.push(io::file_sink(filename)); //Assigns a file sink to out
char* memblock = new char [size]; //This is my data. In reality memblock will have been created earlier and filled with real data
out.write(memblock, size); //Do the writing
delete[] memblock; //Clean up
As written above the resulting file, c:/test.bin.gz, is corrupt. If I try to decompress it, either with gzip or winrar, I get an error message. However, if I instead set size = 4000000 (~4 MB) (slightly smaller), the resulting file works just fine. My problem therefore is that my actual size is 50 MB...
Have you checked that the stream is closed correctly? I tried on Linux, and it seemed to work fine after a added #includes/main etc. In Christ, Steven Watanabe
Many thanks for the quick response. And apologies for being a total newbie,
but how do I close the stream (and how do I check that it has been closed)?
With normal iostreams I would just write "out.close();", out being the name
of the stream. But that doesn't seem to be the way to do it for
filtering_iostreams?!? And I would think it would close when it goes out of
scope, but I haven't checked. Any help appreciated. I'm pleased it worked
for you on Linux, but I'm largely stuck with Windows for the time being...
Anders
On Thu, Apr 7, 2011 at 4:28 PM, Steven Watanabe
AMDG
On 04/07/2011 12:09 PM, Anders Knudby wrote:
Hello all, please help! I'm truly banging my head against the wall here. I am trying to write a function that will allow me to write gzipped binary files (~50 MB) and read them again. I have data in memory. Here's my code for writing:
namespace io = boost::iostreams;
filename = "c:/test.bin.gz"; //My output file int size = 5000000; //Data size in bytes, ~5 MB
//Create filtering_ostream io::filtering_ostream out; //Creates a filtering_ostream called out out.push(io::gzip_compressor()); //Assigns the gzip_compressor to out out.push(io::file_sink(filename)); //Assigns a file sink to out
char* memblock = new char [size]; //This is my data. In reality memblock will have been created earlier and filled with real data
out.write(memblock, size); //Do the writing
delete[] memblock; //Clean up
As written above the resulting file, c:/test.bin.gz, is corrupt. If I try to decompress it, either with gzip or winrar, I get an error message. However, if I instead set size = 4000000 (~4 MB) (slightly smaller), the resulting file works just fine. My problem therefore is that my actual size is 50 MB...
Have you checked that the stream is closed correctly? I tried on Linux, and it seemed to work fine after a added #includes/main etc.
In Christ, Steven Watanabe _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
-- Anders Knudby, PhD e-mail: knudby@gmail.com skype ID: anders.knudby Man's mind, once stretched by a new idea, never regains its original dimensions. ~ Oliver Wendell Holmes
Anders Knudby wrote:
Many thanks for the quick response. And apologies for being a total newbie, but how do I close the stream (and how do I check that it has been closed)? With normal iostreams I would just write "out.close();", out being the name of the stream. But that doesn't seem to be the way to do it for filtering_iostreams?!? And I would think it would close when it goes out of scope, but I haven't checked. Any help appreciated. I'm pleased it worked for you on Linux, but I'm largely stuck with Windows for the time being...
Can you post a complete small example demonstrating the problem? The destructor should close the stream. The docs for iostreams::stream shows a close method at http://www.boost.org/doc/libs/1_46_1/libs/iostreams/doc/index.html. Please don't top post. Jeff
On Fri, Apr 8, 2011 at 7:43 AM, Jeff Flinn
Anders Knudby wrote:
Many thanks for the quick response. And apologies for being a total newbie, but how do I close the stream (and how do I check that it has been closed)? With normal iostreams I would just write "out.close();", out being the name of the stream. But that doesn't seem to be the way to do it for filtering_iostreams?!? And I would think it would close when it goes out of scope, but I haven't checked. Any help appreciated. I'm pleased it worked for you on Linux, but I'm largely stuck with Windows for the time being...
Can you post a complete small example demonstrating the problem? The destructor should close the stream. The docs for iostreams::stream shows a close method at http://www.boost.org/doc/libs/1_46_1/libs/iostreams/doc/index.html.
Please don't top post.
Jeff
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Ok, here's my entire script. As mentioned in the comments it works fine if
size=5e5. It also runs fine if size=5e6, but then the resulting file is
corrupt (i.e. cannot be gunzipped with the gzip utility). Try it out. I'm
using Visual Studio 2008 in a Windows XP machine.
#include
Ok, here's my entire script. As mentioned in the comments it works fine if size=5e5. It also runs fine if size=5e6, but then the resulting file is corrupt (i.e. cannot be gunzipped with the gzip utility). Try it out. I'm using Visual Studio 2008 in a Windows XP machine.
#include
#include #include using namespace std; namespace io = boost::iostreams;
int main() { //Set filename string outfile = "c:/outfile.bin.gz";
//Set filesize int size = int(5e6); // <- If I change this to '5e5' instead of '5e6', everything works just fine.
//Declare memory block to be compressed to file char* memblock = new char [size];
//Create a filtering_ostream out io::filtering_ostream out;
//Assigns the gzip_compressor to out out.push(io::gzip_compressor());
//Assigns out as a file sink out.push(io::file_sink(outfile));
//Write memblock to out out.write(memblock, size);
//Clean up delete[] memblock; io::close(out); //Note, also tried 'out.close();', 'io::close(out, ios_base::out);' and 'close(out);'. Same result.
return 0; }
Works just fine on linux gcc 4.3.2 boost 1.45. with 5e5, 5e6 and 5e7 size. As a guess, I'd delete memblock after closing the out to be on a safe side, maybe it helps. -- Slava
On Mon, Apr 11, 2011 at 3:35 AM,
Ok, here's my entire script. As mentioned in the comments it works fine if
size=5e5. It also runs fine if size=5e6, but then the resulting file is corrupt (i.e. cannot be gunzipped with the gzip utility). Try it out. I'm using Visual Studio 2008 in a Windows XP machine.
#include
#include #include using namespace std; namespace io = boost::iostreams;
int main() { //Set filename string outfile = "c:/outfile.bin.gz";
//Set filesize int size = int(5e6); // <- If I change this to '5e5' instead of '5e6', everything works just fine.
//Declare memory block to be compressed to file char* memblock = new char [size];
//Create a filtering_ostream out io::filtering_ostream out;
//Assigns the gzip_compressor to out out.push(io::gzip_compressor());
//Assigns out as a file sink out.push(io::file_sink(outfile));
//Write memblock to out out.write(memblock, size);
//Clean up delete[] memblock; io::close(out); //Note, also tried 'out.close();', 'io::close(out, ios_base::out);' and 'close(out);'. Same result.
return 0; }
Works just fine on linux gcc 4.3.2 boost 1.45. with 5e5, 5e6 and 5e7 size. As a guess, I'd delete memblock after closing the out to be on a safe side, maybe it helps.
-- Slava
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If anyone is still interested, this is what I got to work after much
hair-pulling. Maybe someone who understand streams (std and boost) better
than I can explain why this works and my previous attempts created corrupt
files when size was large (again, I'm using Windows, VS 2008). Cheers,
Anders
#include <fstream>
#include <iostream>
#include <sstream>
#include
participants (4)
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