File compression with zlib without saving to disk and send via socket - c++

Question

I have a server that receives client files, but the transfer in external networks is too slow, reading a bit i found the solution in file compression. I decided to use zlib for compression, i did a search in some examples in the documentation and below follows two I would like to use in my project. My question is, how to use the following examples to compress a file without saving to disk and send via socket (client-side). And receive and decompress the file (server side).
The client application run on Windows, and server application run on Linux.
Client Side:
int def(FILE *source, FILE *dest, int level)
{
int ret, flush;
unsigned have;
z_stream strm;
unsigned char in[CHUNK];
unsigned char out[CHUNK];
/* allocate deflate state */
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
ret = deflateInit(&strm, level);
if (ret != Z_OK)
return ret;
/* compress until end of file */
do {
strm.avail_in = fread(in, 1, CHUNK, source);
if (ferror(source)) {
(void)deflateEnd(&strm);
return Z_ERRNO;
}
flush = feof(source) ? Z_FINISH : Z_NO_FLUSH;
strm.next_in = in;
/* run deflate() on input until output buffer not full, finish
compression if all of source has been read in */
do {
strm.avail_out = CHUNK;
strm.next_out = out;
ret = deflate(&strm, flush); /* no bad return value */
assert(ret != Z_STREAM_ERROR); /* state not clobbered */
have = CHUNK - strm.avail_out;
if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
(void)deflateEnd(&strm);
return Z_ERRNO;
}
} while (strm.avail_out == 0);
assert(strm.avail_in == 0); /* all input will be used */
/* done when last data in file processed */
} while (flush != Z_FINISH);
assert(ret == Z_STREAM_END); /* stream will be complete */
/* clean up and return */
(void)deflateEnd(&strm);
return Z_OK;
}
Server Side:
int inf(FILE *source, FILE *dest)
{
int ret;
unsigned have;
z_stream strm;
unsigned char in[CHUNK];
unsigned char out[CHUNK];
/* allocate inflate state */
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
strm.avail_in = 0;
strm.next_in = Z_NULL;
ret = inflateInit(&strm);
if (ret != Z_OK)
return ret;
/* decompress until deflate stream ends or end of file */
do {
strm.avail_in = fread(in, 1, CHUNK, source);
if (ferror(source)) {
(void)inflateEnd(&strm);
return Z_ERRNO;
}
if (strm.avail_in == 0)
break;
strm.next_in = in;
/* run inflate() on input until output buffer not full */
do {
strm.avail_out = CHUNK;
strm.next_out = out;
ret = inflate(&strm, Z_NO_FLUSH);
assert(ret != Z_STREAM_ERROR); /* state not clobbered */
switch (ret) {
case Z_NEED_DICT:
ret = Z_DATA_ERROR; /* and fall through */
case Z_DATA_ERROR:
case Z_MEM_ERROR:
(void)inflateEnd(&strm);
return ret;
}
have = CHUNK - strm.avail_out;
if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
(void)inflateEnd(&strm);
return Z_ERRNO;
}
} while (strm.avail_out == 0);
/* done when inflate() says it's done */
} while (ret != Z_STREAM_END);
/* clean up and return */
(void)inflateEnd(&strm);
return ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR;
}

Answer 1

One way is to use a Boost Iostream compressor (they support zlib, gzip, bzip2 out of the box) and an ip::tcp::iostream socket from Boost Asio. Something like:
#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/filter/zlib.hpp>
#include <boost/asio/ip/tcp.hpp>
int main() {
boost::asio::ip::tcp::iostream connection;
boost::iostreams::filtering_stream<boost::iostreams::input> connection_reader;
connection_reader.push(boost::iostreams::zlib_decompressor());
connection_reader.push(connection);
boost::iostreams::filtering_stream<boost::iostreams::output> connection_writer;
connection_writer.push(boost::iostreams::zlib_compressor());
connection_writer.push(connection);
auto const url = "127.0.0.1";
connection.connect(url, "http");
// Send.
connection_writer << "hello there\n";
// Receive.
for(std::string line; getline(connection_reader, line);) {
// Process line.
}
}