wvgzip.cc

00001 /*
00002  * Worldvisions Weaver Software:
00003  *   Copyright (C) 1997-2002 Net Integration Technologies, Inc.
00004  * 
00005  * Gzip encoder/decoder based on zlib.
00006  */
00007 #include "wvgzip.h"
00008 #include <zlib.h>
00009 #include <assert.h>
00010 
00011 #define ZBUFSIZE 10240
00012 
00013 
00014 WvGzipEncoder::WvGzipEncoder(Mode _mode, size_t _out_limit) :
00015     out_limit(_out_limit), tmpbuf(ZBUFSIZE), mode(_mode)
00016 {
00017     ignore_decompression_errors = false;
00018     full_flush = false;
00019     init();
00020 }
00021 
00022 
00023 WvGzipEncoder::~WvGzipEncoder()
00024 {
00025     close();
00026 }
00027 
00028 
00029 void WvGzipEncoder::init()
00030 {
00031     zstr = new z_stream;
00032     memset(zstr, 0, sizeof(*zstr));
00033     zstr->zalloc = Z_NULL;
00034     zstr->zfree = Z_NULL;
00035     zstr->opaque = NULL;
00036     zstr->msg = NULL;
00037     
00038     int retval;
00039     if (mode == Deflate)
00040         retval = deflateInit(zstr, Z_DEFAULT_COMPRESSION);
00041     else
00042         retval = inflateInit(zstr);
00043     
00044     if (retval != Z_OK)
00045     {
00046         seterror("error %s initializing gzip %s: %s", retval,
00047             mode == Deflate ? "compressor" : "decompressor",
00048             zstr->msg ? zstr->msg : "unknown");
00049         return;
00050     }
00051     zstr->next_in = zstr->next_out = NULL;
00052     zstr->avail_in = zstr->avail_out = 0;
00053 }
00054 
00055 void WvGzipEncoder::close()
00056 {
00057     if (mode == Deflate)
00058         deflateEnd(zstr);
00059     else
00060         inflateEnd(zstr);
00061 
00062     delete zstr;
00063 
00064 }
00065 
00066 bool WvGzipEncoder::_encode(WvBuf &inbuf, WvBuf &outbuf, bool flush)
00067 {
00068     bool success;
00069     output = 0;
00070     for (;;)
00071     {
00072         prepare(& inbuf);
00073         bool alldata = inbuf.used() == 0;
00074         success = process(outbuf, flush && alldata, false);
00075         if (zstr->avail_in != 0)
00076         {
00077             // unget unused data
00078             inbuf.unget(zstr->avail_in);
00079             zstr->avail_in = 0;
00080         }
00081         if (! success)
00082             return false;
00083         if (alldata || (out_limit && (output == out_limit)))
00084             return true;
00085     }
00086 }
00087 
00088 
00089 bool WvGzipEncoder::_finish(WvBuf &outbuf)
00090 {
00091     prepare(NULL);
00092     return process(outbuf, false, true);
00093 }
00094 
00095 
00096 bool WvGzipEncoder::_reset()
00097 {
00098     close();
00099     init();
00100     return true;
00101 }
00102 
00103 
00104 void WvGzipEncoder::prepare(WvBuf *inbuf)
00105 {
00106     assert(zstr->avail_in == 0);
00107     if (inbuf && inbuf->used() != 0)
00108     {
00109         size_t avail = inbuf->optgettable();
00110         zstr->avail_in = avail;
00111         zstr->next_in = const_cast<Bytef*>(
00112             (const Bytef*)inbuf->get(avail));
00113     }
00114     else
00115     {
00116         zstr->avail_in = 0;
00117         zstr->next_in = (Bytef*)""; // so it's not NULL
00118     }
00119 }
00120 
00121 
00122 bool WvGzipEncoder::process(WvBuf &outbuf, bool flush, bool finish)
00123 {
00124     int flushmode = finish ? Z_FINISH :
00125         flush ? (full_flush ? Z_FULL_FLUSH : Z_SYNC_FLUSH) : Z_NO_FLUSH;
00126     int retval;
00127     do
00128     {
00129         // process the next chunk
00130         tmpbuf.zap();
00131         size_t avail_out = tmpbuf.free();
00132         if (out_limit)
00133             avail_out = tmpbuf.free() < (out_limit - output) ? tmpbuf.free()
00134                 : (out_limit - output);
00135 
00136         zstr->avail_out = avail_out;
00137         zstr->next_out = tmpbuf.alloc(avail_out);
00138         if (mode == Deflate)
00139             retval = deflate(zstr, flushmode);
00140         else
00141             retval = inflate(zstr, flushmode);
00142         tmpbuf.unalloc(zstr->avail_out);
00143 
00144         output += avail_out - zstr->avail_out;
00145 
00146         // consume pending output
00147         outbuf.merge(tmpbuf);
00148 
00149         if (retval == Z_DATA_ERROR && mode == Inflate
00150             && ignore_decompression_errors)
00151             retval = inflateSync(zstr);
00152     } while (retval == Z_OK && (!out_limit || (out_limit == output)));
00153 
00154     if (retval == Z_STREAM_END)
00155         setfinished();
00156     else if (retval != Z_OK && retval != Z_BUF_ERROR &&
00157              !(retval == Z_DATA_ERROR && mode == Inflate
00158                && ignore_decompression_errors))
00159     {
00160         seterror("error %s during gzip %s: %s", retval,
00161             mode == Deflate ? "compression" : "decompression",
00162             zstr->msg ? zstr->msg : "unknown");
00163         return false;
00164     }
00165 
00166     return true;
00167 }
00168 

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