gzip compress/decompress + refactor

src/coders/gzip.cpp

@@ -0,0 +1,56 @@
+#include "gzip.h"
+
+#define ZLIB_CONST
+#include <zlib.h>
+#include <math.h>
+#include <memory>
+#include "byte_utils.h"
+
+std::vector<ubyte> gzip::compress(const ubyte* src, size_t size) {
+    size_t buffer_size = 23+size*1.01;
+    std::vector<ubyte> buffer;
+    buffer.resize(buffer_size);
+
+    // zlib struct
+    z_stream defstream {};
+    defstream.zalloc = Z_NULL;
+    defstream.zfree = Z_NULL;
+    defstream.opaque = Z_NULL;
+    defstream.avail_in = size;
+    defstream.next_in = src;
+    defstream.avail_out = buffer_size;
+    defstream.next_out = buffer.data();
+
+    // compression
+    deflateInit2(&defstream, Z_DEFAULT_COMPRESSION, Z_DEFLATED, 
+                 16 + MAX_WBITS, 8, Z_DEFAULT_STRATEGY);
+    deflate(&defstream, Z_FINISH);
+    deflateEnd(&defstream);
+
+    size_t compressed_size = defstream.next_out - buffer.data();
+    buffer.resize(compressed_size);
+    return buffer;
+}
+
+std::vector<ubyte> gzip::decompress(const ubyte* src, size_t size) {
+    // getting uncompressed data length from gzip footer
+    size_t decompressed_size = *(uint32_t*)(src+size-4);
+    std::vector<ubyte> buffer;
+    buffer.resize(decompressed_size);
+
+    // zlib struct
+    z_stream infstream;
+    infstream.zalloc = Z_NULL;
+    infstream.zfree = Z_NULL;
+    infstream.opaque = Z_NULL;
+    infstream.avail_in = size;
+    infstream.next_in = src;
+    infstream.avail_out = decompressed_size;
+    infstream.next_out = buffer.data();
+
+    inflateInit2(&infstream, 16+MAX_WBITS);
+    inflate(&infstream, Z_NO_FLUSH);
+    inflateEnd(&infstream);
+
+    return buffer;
+}