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#ifndef _COMPRESS_STRING_H
#define _COMPRESS_STRING_H
#include <string>
#include <zlib.h>
using namespace std;
/** Compress a STL string using zlib with given compression level and return
* the binary data. */
string compress_string(const string& str, int compressionlevel = Z_BEST_COMPRESSION)
{
z_stream zs; // z_stream is zlib's control structure
memset(&zs, 0, sizeof(zs));
if (deflateInit(&zs, compressionlevel) != Z_OK)
throw(std::runtime_error("deflateInit failed while compressing."));
zs.next_in = (Bytef*)str.data();
zs.avail_in = str.size(); // set the z_stream's input
int ret;
char outbuffer[32768];
std::string outstring;
// retrieve the compressed bytes blockwise
do {
zs.next_out = reinterpret_cast<Bytef*>(outbuffer);
zs.avail_out = sizeof(outbuffer);
ret = deflate(&zs, Z_FINISH);
if (outstring.size() < zs.total_out) {
// append the block to the output string
outstring.append(outbuffer,
zs.total_out - outstring.size());
}
} while (ret == Z_OK);
deflateEnd(&zs);
if (ret != Z_STREAM_END) { // an error occurred that was not EOF
ostringstream oss;
oss << "Exception during zlib compression: (" << ret << ") " << zs.msg;
throw(runtime_error(oss.str()));
}
return outstring;
}
/** Decompress an STL string using zlib and return the original data. */
string decompress_string(const string& str)
{
z_stream zs; // z_stream is zlib's control structure
memset(&zs, 0, sizeof(zs));
if (inflateInit(&zs) != Z_OK)
throw(std::runtime_error("inflateInit failed while decompressing."));
zs.next_in = (Bytef*)str.data();
zs.avail_in = str.size();
int ret;
char outbuffer[32768];
std::string outstring;
// get the decompressed bytes blockwise using repeated calls to inflate
do {
zs.next_out = reinterpret_cast<Bytef*>(outbuffer);
zs.avail_out = sizeof(outbuffer);
ret = inflate(&zs, 0);
if (outstring.size() < zs.total_out) {
outstring.append(outbuffer,
zs.total_out - outstring.size());
}
} while (ret == Z_OK);
inflateEnd(&zs);
if (ret != Z_STREAM_END) { // an error occurred that was not EOF
std::ostringstream oss;
oss << "Exception during zlib decompression: (" << ret << ") "
<< zs.msg;
throw(std::runtime_error(oss.str()));
}
return outstring;
}
#endif
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