Es ist mir gelungen, einen Kompressor zu entwickeln, der den wachsenden Puffer Teil für Teil durch den Kanal mit einer begrenzten Eingangsgröße sendet. Ich gebe hier die Antwort für jeden, der an dem gleichen Problem arbeitet. Thx zu Mark Adler und zu MSalters, um mich zum richtigen Weg zu führen.
class zStreamManager {
public:
zStreamManager();
~zStreamManager();
void endStream();
void addToStream(const void *inData, size_t inDataSize);
private:
// Size of base64 encoded is about 4*originalSize/3 + (3 to 6)
// so with maximum output size of 4096, 3050 max zipped out
// buffer will be fine
const size_t CHUNK_IN = 1024, CHUNK_OUT = 3050;
const std::string base64Chars =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"/";
bool deallocated = true;
z_stream stream;
std::vector<uint8_t> outBuffer;
std::string base64Encode(std::vector<uint8_t> &str);
};
zStreamManager::~zStreamManager() {
endStream();
}
void zStreamManager::endStream() {
if(!deallocated) {
deallocated = true;
uint8_t tempBuffer[CHUNK_IN];
int response = Z_OK;
unsigned int have;
while(response == Z_OK) {
if (stream.avail_out == 0) {
outBuffer.insert(outBuffer.end(), tempBuffer, tempBuffer + CHUNK_IN);
stream.next_out = tempBuffer;
stream.avail_out = CHUNK_IN;
}
response = deflate(&stream, Z_FINISH);
}
have = CHUNK_IN - stream.avail_out;
if(have)
outBuffer.insert(outBuffer.end(), tempBuffer, tempBuffer + have);
deflateEnd(&stream);
if(outBuffer.size())
SEND << outBuffer << "$";
}
}
void zStreamManager::addToStream(const void *inData, size_t inDataSize) {
if(deallocated) {
deallocated = false;
stream.zalloc = 0;
stream.zfree = 0;
stream.opaque = 0;
deflateInit(&stream, 9);
}
std::vector<uint8_t> tempBuffer(inDataSize);
unsigned int have;
stream.next_in = reinterpret_cast<uint8_t *>(const_cast<void*>(inData));
stream.avail_in = inDataSize;
stream.next_out = &tempBuffer[0];
stream.avail_out = inDataSize;
while (stream.avail_in != 0) {
deflate(&stream, Z_SYNC_FLUSH);
if (stream.avail_out == 0) {
outBuffer.insert(outBuffer.end(), tempBuffer.begin(), tempBuffer.begin() + inDataSize);
stream.next_out = &tempBuffer[0];
stream.avail_out = inDataSize;
}
}
have = inDataSize - stream.avail_out;
if(have)
outBuffer.insert(outBuffer.end(), tempBuffer.begin(), tempBuffer.begin() + have);
while(outBuffer.size() >= CHUNK_OUT) {
std::vector<uint8_t> zipped;
zipped.insert(zipped.end(), outBuffer.begin(), outBuffer.begin() + CHUNK_OUT);
outBuffer.erase(outBuffer.begin(), outBuffer.begin() + CHUNK_OUT);
if(zipped.size())
SEND << zipped << "|";
}
}
std::string zStreamManager::base64Encode(std::vector<uint8_t> &str) {
/* ALTERED VERSION OF René Nyffenegger BASE64 CODE
Copyright (C) 2004-2008 René Nyffenegger
This source code is provided 'as-is', without any express or implied
warranty. In no event will the author be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this source code must not be misrepresented; you must not
claim that you wrote the original source code. If you use this source code
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original source code.
3. This notice may not be removed or altered from any source distribution.
René Nyffenegger [email protected]
*/
unsigned char const* bytes_to_encode = &str[0];
unsigned int in_len = str.size();
std::string ret;
int i = 0, j = 0;
unsigned char char_array_3[3], char_array_4[4];
while(in_len--) {
char_array_3[i++] = *(bytes_to_encode++);
if (i == 3) {
char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
char_array_4[3] = char_array_3[2] & 0x3f;
for(i = 0; (i <4) ; i++)
ret += base64Chars[char_array_4[i]];
i = 0;
}
}
if(i) {
for(j = i; j < 3; j++)
char_array_3[j] = '\0';
char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
char_array_4[3] = char_array_3[2] & 0x3f;
for(j = 0; (j < i + 1); j++)
ret += base64Chars[char_array_4[j]];
while((i++ < 3))
ret += '=';
}
return ret;
}
Ein Anwendungsfall:
zStreamManager zm;
string growingBuffer = "";
bool somethingToSend = true;
while(somethingToSend) {
RECEIVE(&growingBuffer);
if(growingBuffer.size()) {
zm.addToStream(growingBuffer.c_str(), growingBuffer.size());
growingBuffer.clear();
} else {
somethingToSend = false;
}
}
zm.endStream();
Mit RECEIVE
und SEND
, den verwendeten Methoden für den Puffer zu empfangen und es über den Kanal zu senden. Zum Dekomprimieren wird jeder Teil durch das '|' Zeichen und das Ende des gesamten Puffers wird durch '$' begrenzt. Jeder Teil muss base64 decodiert und dann verkettet werden. Letztendlich kann es mit zlib wie alle anderen komprimierten Daten dekomprimiert werden.
Keine Ahnung über Zlib wirklich, aber schauen Sie sich LZMA an, die Ihrer Meinung nach mit Ihrer Situation umgehen könnte. http://7-zip.org/sdk.html – antipattern