transmission/libtransmission/block-info.h

160 lines
4.3 KiB
C++

// This file Copyright © 2021-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#pragma once
#include <cstdint> // uint32_t, uint64_t
#include "transmission.h"
struct tr_block_info
{
private:
uint64_t total_size_ = 0;
uint32_t piece_size_ = 0;
tr_piece_index_t n_pieces_ = 0;
tr_block_index_t n_blocks_ = 0;
// should be same type as BlockSize
uint32_t final_block_size_ = 0;
// should be same type as piece_size
uint32_t final_piece_size_ = 0;
public:
static auto constexpr BlockSize = uint32_t{ 1024 * 16 };
tr_block_info() noexcept = default;
tr_block_info(uint64_t total_size_in, uint32_t piece_size_in) noexcept
{
initSizes(total_size_in, piece_size_in);
}
void initSizes(uint64_t total_size_in, uint32_t piece_size_in) noexcept;
[[nodiscard]] constexpr auto blockCount() const noexcept
{
return n_blocks_;
}
[[nodiscard]] constexpr auto blockSize(tr_block_index_t block) const noexcept
{
return block + 1 == n_blocks_ ? final_block_size_ : BlockSize;
}
[[nodiscard]] constexpr auto pieceCount() const noexcept
{
return n_pieces_;
}
[[nodiscard]] constexpr auto pieceSize() const noexcept
{
return piece_size_;
}
[[nodiscard]] constexpr auto pieceSize(tr_piece_index_t piece) const noexcept
{
return piece + 1 == n_pieces_ ? final_piece_size_ : pieceSize();
}
[[nodiscard]] constexpr auto totalSize() const noexcept
{
return total_size_;
}
struct Location
{
uint64_t byte = 0;
tr_piece_index_t piece = 0;
uint32_t piece_offset = 0;
tr_block_index_t block = 0;
uint32_t block_offset = 0;
[[nodiscard]] constexpr bool operator==(Location const& that) const noexcept
{
return this->byte == that.byte;
}
[[nodiscard]] constexpr bool operator<(Location const& that) const noexcept
{
return this->byte < that.byte;
}
};
// Location of the torrent's nth byte
[[nodiscard]] constexpr auto byteLoc(uint64_t byte_idx) const noexcept
{
auto loc = Location{};
if (isInitialized())
{
loc.byte = byte_idx;
if (byte_idx == totalSize()) // handle 0-byte files at the end of a torrent
{
loc.block = blockCount() - 1;
loc.piece = pieceCount() - 1;
}
else
{
loc.block = byte_idx / BlockSize;
loc.piece = byte_idx / pieceSize();
}
loc.block_offset = static_cast<uint32_t>(loc.byte - (uint64_t{ loc.block } * BlockSize));
loc.piece_offset = static_cast<uint32_t>(loc.byte - (uint64_t{ loc.piece } * pieceSize()));
}
return loc;
}
// Location of the first byte in `block`.
[[nodiscard]] constexpr auto blockLoc(tr_block_index_t block) const noexcept
{
return byteLoc(uint64_t{ block } * BlockSize);
}
// Location of the first byte (+ optional offset and length) in `piece`
[[nodiscard]] constexpr auto pieceLoc(tr_piece_index_t piece, uint32_t offset = 0, uint32_t length = 0) const noexcept
{
return byteLoc(uint64_t{ piece } * pieceSize() + offset + length);
}
[[nodiscard]] constexpr tr_block_span_t blockSpanForPiece(tr_piece_index_t piece) const noexcept
{
if (!isInitialized())
{
return { 0U, 0U };
}
return { pieceLoc(piece).block, pieceLastLoc(piece).block + 1 };
}
[[nodiscard]] constexpr tr_byte_span_t byteSpanForPiece(tr_piece_index_t piece) const noexcept
{
if (!isInitialized())
{
return { 0U, 0U };
}
auto const offset = pieceLoc(piece).byte;
return { offset, offset + pieceSize(piece) };
}
private:
// Location of the last byte in `piece`.
[[nodiscard]] constexpr Location pieceLastLoc(tr_piece_index_t piece) const noexcept
{
return byteLoc(static_cast<uint64_t>(piece) * pieceSize() + pieceSize(piece) - 1);
}
[[nodiscard]] constexpr bool isInitialized() const noexcept
{
return piece_size_ != 0;
}
};