transmission/libtransmission/block-info.h

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// This file Copyright © 2021-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0), GPLv3 (SPDX: GPL-3.0),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#pragma once
#include "transmission.h"
#include "tr-assert.h"
struct tr_block_info
{
static auto constexpr BlockSize = uint32_t{ 1024 * 16 };
uint64_t total_size = 0;
uint64_t piece_size = 0;
uint64_t n_pieces = 0;
tr_block_index_t n_blocks = 0;
uint32_t final_block_size = 0;
uint32_t final_piece_size = 0;
tr_block_info() = default;
tr_block_info(uint64_t total_size_in, uint64_t piece_size_in)
{
initSizes(total_size_in, piece_size_in);
}
void initSizes(uint64_t total_size_in, uint64_t piece_size_in);
[[nodiscard]] constexpr auto blockCount() const
{
return n_blocks;
}
// return the number of bytes in `block`
[[nodiscard]] constexpr auto blockSize(tr_block_index_t block) const
{
return block + 1 == n_blocks ? final_block_size : BlockSize;
}
[[nodiscard]] constexpr auto pieceCount() const
{
return n_pieces;
}
[[nodiscard]] constexpr auto pieceSize() const
{
return piece_size;
}
// return the number of bytes in `piece`
[[nodiscard]] constexpr auto pieceSize(tr_piece_index_t piece) const
{
return piece + 1 == n_pieces ? final_piece_size : pieceSize();
}
[[nodiscard]] constexpr tr_block_span_t blockSpanForPiece(tr_piece_index_t piece) const
{
if (!isInitialized())
{
return {};
}
return { pieceLoc(piece).block, pieceLastLoc(piece).block + 1 };
}
[[nodiscard]] constexpr auto totalSize() const
{
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]] bool operator==(Location const& that) const
{
return this->byte == that.byte;
}
[[nodiscard]] bool operator<(Location const& that) const
{
return this->byte < that.byte;
}
};
// Location of the first byte in `block`.
[[nodiscard]] Location constexpr blockLoc(tr_block_index_t block) const
{
TR_ASSERT(block < n_blocks);
return byteLoc(uint64_t{ block } * BlockSize);
}
// Location of the last byte in `block`.
[[nodiscard]] Location constexpr blockLastLoc(tr_block_index_t block) const
{
if (!isInitialized())
{
return {};
}
return byteLoc(uint64_t{ block } * BlockSize + blockSize(block) - 1);
}
// Location of the first byte (+ optional offset and length) in `piece`
[[nodiscard]] Location constexpr pieceLoc(tr_piece_index_t piece, uint32_t offset = 0, uint32_t length = 0) const
{
TR_ASSERT(piece < n_pieces);
return byteLoc(uint64_t{ piece } * pieceSize() + offset + length);
}
// Location of the last byte in `piece`.
[[nodiscard]] Location constexpr pieceLastLoc(tr_piece_index_t piece) const
{
if (!isInitialized())
{
return {};
}
return byteLoc(uint64_t{ piece } * pieceSize() + pieceSize(piece) - 1);
}
// Location of the torrent's nth byte
[[nodiscard]] Location constexpr byteLoc(uint64_t byte) const
{
TR_ASSERT(byte <= total_size);
if (!isInitialized())
{
return {};
}
auto loc = Location{};
loc.byte = byte;
if (byte == totalSize()) // handle 0-byte files at the end of a torrent
{
loc.block = blockCount() - 1;
loc.piece = pieceCount() - 1;
}
else
{
loc.block = byte / BlockSize;
loc.piece = byte / 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;
}
[[nodiscard]] static uint32_t bestBlockSize(uint64_t piece_size);
private:
[[nodiscard]] bool constexpr isInitialized() const
{
return piece_size != 0;
}
};