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#ifndef BYTEME_ZLIB_BUFFER_READER_HPP
#define BYTEME_ZLIB_BUFFER_READER_HPP
#include "zlib.h"
#include <stdexcept>
#include <vector>
#include "Reader.hpp"
/**
* @file ZlibBufferReader.hpp
*
* @brief Read bytes from a Zlib-compressed buffer.
*/
namespace byteme {
/**
* @brief Read and decompress bytes from a Zlib-compressed buffer.
*
* This is basically a wrapper around Zlib's inflate method, with correct closing and error checking.
*/
class ZlibBufferReader : public Reader {
private:
/**
* @cond
*/
struct ZStream {
ZStream(int mode) {
/* allocate inflate state */
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
strm.avail_in = 0;
strm.next_in = Z_NULL;
/* See:
* https://stackoverflow.com/questions/1838699/how-can-i-decompress-a-gzip-stream-with-zlib
* https://stackoverflow.com/questions/29003909/why-is-a-different-zlib-window-bits-value-required-for-extraction-compared-with
*/
int ret = 0;
if (mode == 0) { // DEFLATE
ret = inflateInit2(&strm, -MAX_WBITS);
} else if (mode == 1) { // Zlib
ret = inflateInit2(&strm, MAX_WBITS);
} else if (mode == 2) { // Gzip
ret = inflateInit2(&strm, 16+MAX_WBITS);
} else if (mode == 3) { // Gzip/Zlib auto-detected
ret = inflateInit2(&strm, 32+MAX_WBITS);
} else {
throw std::runtime_error("mode must be 0 (DEFLATE), 1 (Zlib), 2 (Gzip) or 3 (automatic");
}
if (ret != Z_OK) {
throw 1;
}
}
~ZStream() {
(void)inflateEnd(&strm);
return;
}
// Delete the remaining constructors.
ZStream(const ZStream&) = delete;
ZStream(ZStream&&) = delete;
ZStream& operator=(const ZStream&) = delete;
ZStream& operator=(ZStream&&) = delete;
z_stream strm;
};
/**
* @endcond
*/
public:
/**
* @param buffer Pointer to an array containing the compressed data.
* @param len Length of the `buffer` array.
* @param mode Compression of the stream - DEFLATE (0), Zlib (1) or Gzip (2).
* Default of 3 will auto-detect between Zlib and Gzip based on the headers.
* @param buffer_size Size of the buffer to use for reading.
*/
ZlibBufferReader(const unsigned char* buffer, size_t len, int mode = 3, size_t buffer_size = 65536) : zstr(mode), buffer_(buffer_size) {
zstr.strm.avail_in = len;
zstr.strm.next_in = const_cast<unsigned char*>(buffer); // cast is purely for C compatibility.
}
bool load() {
/* This function is stolen from the loop in 'inf()' at
* http://www.zlib.net/zpipe.c, with some shuffling of code to make it
* a bit more C++-like.
*/
if (!okay) {
return false;
}
// Not entirely sure why we need to check for this, but
// https://zlib.net/zpipe.c does it, and so will we; because not doing
// so seems to occasionally result in infinite loops.
if (zstr.strm.avail_in == 0) {
return false;
}
zstr.strm.avail_out = buffer_.size();
zstr.strm.next_out = buffer_.data();
int ret = inflate(&(zstr.strm), Z_NO_FLUSH);
switch (ret) {
case Z_STREAM_ERROR:
case Z_NEED_DICT:
case Z_DATA_ERROR:
case Z_MEM_ERROR:
throw std::runtime_error("zlib error");
case Z_STREAM_END:
okay = false;
break;
}
read = buffer_.size() - zstr.strm.avail_out;
return true;
}
const unsigned char* buffer() const {
return buffer_.data();
}
size_t available() const {
return read;
}
private:
ZStream zstr;
std::vector<unsigned char> buffer_;
size_t read = 0;
bool okay = true;
};
}
#endif
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