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beakr/Decompress.cpp

Created September 24, 2014 16:13
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  1. beakr created this gist Sep 24, 2014.
    114 changes: 114 additions & 0 deletions Decompress.cpp
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,114 @@
    #include <cstdio>
    #include <string>
    #include <cstring>
    #include <cstdlib>
    #include "zlib.h"
    #include "zconf.h"
    using namespace std;

    bool gzipInflate( const std::string& compressedBytes, std::string& uncompressedBytes ) {
    if ( compressedBytes.size() == 0 ) {
    uncompressedBytes = compressedBytes ;
    return true ;
    }

    uncompressedBytes.clear() ;

    unsigned full_length = compressedBytes.size() ;
    unsigned half_length = compressedBytes.size() / 2;

    unsigned uncompLength = full_length ;
    char* uncomp = (char*) calloc( sizeof(char), uncompLength );

    z_stream strm;
    strm.next_in = (Bytef *) compressedBytes.c_str();
    strm.avail_in = compressedBytes.size() ;
    strm.total_out = 0;
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;

    bool done = false ;

    if (inflateInit2(&strm, (16+MAX_WBITS)) != Z_OK) {
    free( uncomp );
    return false;
    }

    while (!done) {
    // If our output buffer is too small
    if (strm.total_out >= uncompLength ) {
    // Increase size of output buffer
    char* uncomp2 = (char*) calloc( sizeof(char), uncompLength + half_length );
    memcpy( uncomp2, uncomp, uncompLength );
    uncompLength += half_length ;
    free( uncomp );
    uncomp = uncomp2 ;
    }

    strm.next_out = (Bytef *) (uncomp + strm.total_out);
    strm.avail_out = uncompLength - strm.total_out;

    // Inflate another chunk.
    int err = inflate (&strm, Z_SYNC_FLUSH);
    if (err == Z_STREAM_END) done = true;
    else if (err != Z_OK) {
    break;
    }
    }

    if (inflateEnd (&strm) != Z_OK) {
    free( uncomp );
    return false;
    }

    for ( size_t i=0; i<strm.total_out; ++i ) {
    uncompressedBytes += uncomp[ i ];
    }
    free( uncomp );
    return true ;
    }

    /* Reads a file into memory. */
    bool loadBinaryFile( const std::string& filename, std::string& contents ) {
    // Open the gzip file in binary mode
    FILE* f = fopen( filename.c_str(), "rb" );
    if ( f == NULL )
    return false ;

    // Clear existing bytes in output vector
    contents.clear();

    // Read all the bytes in the file
    int c = fgetc( f );
    while ( c != EOF ) {
    contents += (char) c ;
    c = fgetc( f );
    }
    fclose (f);

    return true ;
    }

    int main() {
    // Read the gzip file data into memory
    std::string fileData ;
    if ( !loadBinaryFile( "archive.gz", fileData ) ) {
    printf( "Error loading input file." );
    return 0 ;
    }

    // Uncompress the file data
    std::string data ;
    if ( !gzipInflate( fileData, data ) ) {
    printf( "Error decompressing file." );
    return 0 ;
    }

    // Print the data
    printf( "Data: \"" );
    for ( size_t i=0; i<data.size(); ++i ) {
    printf( "%c", data[i] );
    }
    printf ( "\"\n" );
    return 0;
    }