Hi Ed, Couldn't you use the iostreams copy() algorithm? So I guess your code would look something like: io::filtering_istream decompressFilter; decompressFilter.push(io::gzip_decompressor()); std::strstream streamOfCompressedData; streamOfCompressedData.write((char*)compressedHTML, 586); decompressFilter.push(streamOfCompressedData); std::ostrstream output; io::copy(decompressFilter, output); I haven't actually tested this code snippet, but it should get you what you are looking for. You probably still have to flush the data by calling sync(). Hope this helps. --Rob Ed Sykes wrote:
Hi,
I'm trying to use a filtering istream with a gzip decompressor attached. I've got it all working but the one part that I am having trouble with is figuring out the most effective way of consuming the decompressed data. I'd like to be able to get hold of all the decompressed data in one go, rather than reading out a word at a time using the >> operator. It seems to me that the most logical way of doing it, given what I have read about the way streams work, would be to use rdbuf() to get the streambuffer and then send that to a stringstream. However when I try this the filtering_istream throws an exception of type boost::iostreams::gzip_error. I do know however that the data integrity is fine since I am able to use >> to push data into a std::string.
Instinctively I realise that the filtering_istream doesn't have an internal buffer as such and using the >> operator pulls data from the source, through the decompressor and into the type on the right hand side. This leaves me confused as to what the best way of getting the data out is if I can't use the filtering_istream as a typical stream inheriting from basic_istream.
I think that perhaps I'm misunderstanding a fundamental principle of how to use the filtering_istream and I'm hoping that someone on the list can point me in the right direction of how I should achieve a read of all the decompressed data. So does anyone have any idea how I should proceed? I've included the code I have thus far below.
Thanks in advance, Ed.
#include "zlib.h" #include
#include #include #include #include <strstream> #include <string> namespace io = boost::iostreams;
void DecompressIntoStringStream() { unsigned char compressedHTML[] = { 0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0xec, 0x7d, 0x7b, 0x77, 0xdb, 0xb6, 0xb2, 0xef, 0xdf, 0xf5, 0x5a, 0xfb, 0x3b, 0x30, 0xca, 0xae, 0x65, 0xd7, 0x7a, 0xbf, 0x6c, 0x4b, 0xa6, 0x7b, 0x1c, 0x3f, 0x92, 0xb4, 0x79, 0x78, 0xc7, 0x4e, 0xb3, 0x7b, 0x7b, 0x7b, 0xb2, 0x28, 0x92, 0xb2, 0x18, 0x53, 0x24, 0x43, 0x52, 0x72, 0x14, 0x27, 0x5f, 0xe3, 0x7e, 0x81, 0xf3, 0x45, 0xef, 0x6f, 0x06, 0x00, 0x09, 0x4a, 0xf2, 0x2b, 0xe9, 0x3e, 0xfb, 0xdc, 0xb5, 0x6e, 0xbb, 0x22, 0x93, 0x20, 0x1e, 0x83, 0xc1, 0x60, 0x30, 0x98, 0x19, 0x0c, 0xf6, 0x1e, 0x1d, 0xbd, 0x3e, 0x3c, 0xff, 0xfd, 0xf4, 0xd8, 0x78, 0x76, 0xfe, 0xf2, 0x85, 0x71, 0xfa, 0xf6, 0xc9, 0x8b, 0xe7, 0x87, 0x46, 0xa9, 0x5a, 0xaf, 0xbf, 0x6b, 0x1f, 0xd6, 0xeb, 0x47, 0xe7, 0x47, 0xe2, 0x43, 0xa7, 0xd6, 0x68, 0x1a, 0xe7, 0xb1, 0x15, 0x24, 0x5e, 0xea, 0x85, 0x81, 0xe5, 0xd7, 0xeb, 0xc7, 0xaf, 0x4a, 0x46, 0x69, 0x9c, 0xa6, 0x51, 0xbf, 0x5e, 0xbf, 0xba, 0xba, 0xaa, 0x5d, 0xb5, 0x6b, 0x61, 0x7c, 0x51, 0x3f, 0x7f, 0x53, 0x1f, 0xa7, 0x13, 0xbf, 0x53, 0xf7, 0xc3, 0x30, 0x71, 0x6b, 0x4e, 0xea, 0x94, 0xf6, 0xd7, 0xf6, 0x28, 0xc9, 0xf0, 0xad, 0xe0, 0xc2, 0x2c, 0xb9, 0x41, 0xf5, 0xe9, 0x13, 0x4e, 0x73, 0x2d, 0x07, 0x9f, 0x12, 0x3b, 0xf6, 0xa2, 0x94, 0x3f, 0x4e, 0xad, 0x0b, 0xd7, 0xfc, 0x60, 0xcd, 0x2c, 0x91, 0xb6, 0xbf, 0x36, 0xb3, 0x62, 0x23, 0x08, 0xaf, 0xcc, 0xc0, 0xbd, 0x32, 0x8e, 0xac, 0xd4, 0xad, 0xa4, 0x4d, 0xb3, 0x51, 0x49, 0x5b, 0xf4, 0xd3, 0xa6, 0x9f, 0x0e, 0xfd, 0x74, 0xe9, 0xa7, 0x87, 0x9f, 0xf7, 0x9e, 0x4b, 0xcf, 0xe3, 0x08, 0x3f, 0x56, 0x88, 0x1f, 0xdb, 0x36, 0xcb, 0xe5, 0xca, 0xdc, 0x8f, 0xf0, 0x67, 0x80, 0xb2, 0xa8, 0xab, 0x76, 0xe1, 0xa6, 0xe7, 0xde, 0xc4, 0xdd, 0xd8, 0x1c, 0x70, 0xf5, 0x33, 0x37, 0x36, 0x4b, 0xcd, 0xd2, 0x60, 0x6d, 0xaf, 0xae, 0x5a, 0xdd, 0x4b, 0xbd, 0xd4, 0x77, 0xf7, 0x7f, 0xb7, 0xc6, 0x61, 0xf8, 0xc8, 0x78, 0xfb, 0xab, 0xb1, 0x6e, 0x4d, 0xa2, 0x81, 0xf1, 0x3c, 0x76, 0xd1, 0x03, 0x67, 0xaf, 0x2e, 0x3e, 0xef, 0x4d, 0xdc, 0xd4, 0x32, 0x08, 0x01, 0x55, 0xf7, 0xe3, 0xd4, 0x9b, 0x99, 0xa5, 0xc3, 0x30, 0x48, 0xdd, 0x20, 0xad, 0x9e, 0xcf, 0x23, 0xb7, 0x64, 0xd8, 0xe2, 0xcd, 0x2c, 0xa5, 0xee, 0xa7, 0x94, 0x71, 0x32, 0x30, 0xec, 0xb1, 0x15, 0x27, 0x6e, 0x6a, 0x7a, 0x49, 0x58, 0xdd, 0xd9, 0xe9, 0xee, 0x56, 0x9b, 0x84, 0x88, 0xa5, 0x8a, 0x4e, 0x9f, 0x1f, 0x9e, 0x55, 0x5f, 0x58, 0x43, 0xd7, 0xcf, 0xab, 0x29, 0x6f, 0x70, 0x6a, 0xb3, 0xd6, 0x2c, 0x60, 0xdd, 0xb3, 0x63, 0x8b, 0xf1, 0x1e, 0x5b, 0xa9, 0x17, 0x5c, 0x24, 0xb3, 0x46, 0xab, 0x46, 0xc8, 0x2e, 0x19, 0xbe, 0x11, 0x1b, 0x1b, 0xf6, 0x67, 0xa3, 0x69, 0xf8, 0xf4, 0x13, 0xd0, 0x4f, 0x48, 0x3f, 0x33, 0xfc, 0x6c, 0x1a, 0x17, 0x6e, 0x60, 0xa4, 0xf1, 0xd4, 0x35, 0x46, 0x61, 0x9c, 0xd5, 0x38, 0xbd, 0xac, 0xcd, 0xa9, 0xd7, 0x35, 0x3b, 0x9c, 0x94, 0x6e, 0x2f, 0xaf, 0x0f, 0x7d, 0x9c, 0x58, 0x76, 0x11, 0x88, 0xa6, 0x0e, 0x44, 0x60, 0x34, 0x8c, 0x04, 0xff, 0x66, 0xf8, 0xe7, 0x1b, 0x8d, 0xfb, 0xb6, 0xbd, 0x58, 0x6c, 0xb3, 0xbc, 0x2f, 0x50, 0x15, 0x58, 0x13, 0xd7, 0x2c, 0x39, 0xae, 0x18, 0x2f, 0x90, 0x63, 0x8e, 0xa5, 0xd2, 0x0d, 0x83, 0x66, 0x3c, 0x0b, 0x27, 0xae, 0x71, 0x0a, 0xfa, 0x32, 0xfe, 0x8f, 0x71, 0xe6, 0x5a, 0xb1, 0x3d, 0x36, 0xd2, 0xb1, 0x6b, 0x5c, 0xb9, 0x43, 0x03, 0x63, 0xca, 0xcf, 0xb2, 0xe8, 0x3b, 0x24, 0x1d, 0x79, 0xb1, 0x6b, 0xa7, 0x61, 0x3c, 0xaf, 0x18, 0x89, 0x77, 0x11, 0x18, 0xd3, 0x88, 0xd1, 0x64, 0x19, 0xa3, 0xd8, 0x75, 0x0d, 0x99, 0xd1, 0x9d, 0x58, 0x9e, 0x6f, 0x58, 0xb6, 0x1d, 0x4e, 0x83, 0x94, 0x6b, 0x19, 0x79, 0xb2, 0x2a, 0x1f, 0xb4, 0x9a, 0xa4, 0xc8, 0x1d, 0x4e, 0x54, 0xee, 0x13, 0x2f, 0xb0, 0x02, 0xdb, 0xad, 0x18, 0x67};
io::filtering_istream decompressFilter; decompressFilter.push(io::gzip_decompressor());
std::strstream streamOfCompressedData; streamOfCompressedData.write((char*)compressedHTML, 586); decompressFilter.push(streamOfCompressedData);
std::stringstream output; try { output << decompressFilter.rdbuf(); } catch(std::exception& exc) { exc; // dummy code to allow me to inspect exc: int i = 0; i; } }