zlib.hpp

// Copyright Take Vos 2020.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "../file/file.hpp"
#include "../container/container.hpp"
#include "../parser/parser.hpp"
#include "../macros.hpp"
#include "inflate.hpp"
#include <cstddef>
#include <filesystem>
 
hi_export_module(hikogui.codec.zlib);
 
hi_export namespace hi { inline namespace v1 {
 
[[nodiscard]] inline bstring zlib_decompress(std::span<std::byte const> bytes, std::size_t max_size)
{
    struct zlib_header {
        uint8_t CMF;
        uint8_t FLG;
    };
 
    auto offset = 0_uz;
 
    auto const header = make_placement_ptr<zlib_header>(bytes, offset);
 
    auto const header_chksum = header->CMF * 256 + header->FLG;
    hi_check(header_chksum % 31 == 0, "zlib header checksum failed.");
 
    hi_check((header->CMF & 0xf) == 8, "zlib compression method must be 8");
    hi_check(((header->CMF >> 4) & 0xf) <= 7, "zlib LZ77 window too large");
    hi_check((header->FLG & 0x20) == 0, "zlib must not use a preset dictionary");
 
    if (header->FLG & 0x20) {
        [[maybe_unused]] auto FDICT = make_placement_ptr<big_uint32_buf_t>(bytes, offset);
    }
 
    auto r = inflate(bytes, offset, max_size);
 
    [[maybe_unused]] auto ADLER32 = make_placement_ptr<big_uint32_buf_t>(bytes, offset);
 
    return r;
}
 
[[nodiscard]] inline bstring zlib_decompress(std::filesystem::path const& path, std::size_t max_size = 0x01000000)
{
    return zlib_decompress(as_span<std::byte const>(file_view(path)), max_size);
}
 
}} // namespace hi::v1