transmission/libtransmission/block-info.h

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// This file Copyright © Mnemosyne LLC.
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// 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
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#include "libtransmission/transmission.h"
struct tr_block_info
{
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public:
static auto constexpr BlockSize = uint32_t{ 1024U * 16U };
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tr_block_info() noexcept = default;
tr_block_info(uint64_t const total_size_in, uint32_t const piece_size_in) noexcept
{
init_sizes(total_size_in, piece_size_in);
}
[[nodiscard]] constexpr auto block_count() const noexcept
{
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return n_blocks_;
}
[[nodiscard]] constexpr auto block_size(tr_block_index_t const block) const noexcept
{
return block + 1U == n_blocks_ ? final_block_size_ : BlockSize;
}
[[nodiscard]] constexpr auto piece_count() const noexcept
{
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return n_pieces_;
}
[[nodiscard]] constexpr auto piece_size() const noexcept
{
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return piece_size_;
}
[[nodiscard]] constexpr auto piece_size(tr_piece_index_t const piece) const noexcept
{
return piece + 1U == n_pieces_ ? final_piece_size_ : piece_size();
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}
[[nodiscard]] constexpr auto total_size() const noexcept
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{
return total_size_;
}
struct Location
{
[[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;
}
uint64_t byte = {};
tr_piece_index_t piece = {};
uint32_t piece_offset = {};
tr_block_index_t block = {};
uint32_t block_offset = {};
};
// Location of the torrent's nth byte
[[nodiscard]] constexpr auto byte_loc(uint64_t const byte_idx) const noexcept
{
auto loc = Location{};
if (is_initialized())
{
loc.byte = byte_idx;
if (byte_idx == total_size()) // handle 0-byte files at the end of a torrent
{
loc.block = block_count() - 1U;
loc.piece = piece_count() - 1U;
}
else
{
loc.block = static_cast<tr_block_index_t>(byte_idx / BlockSize);
loc.piece = static_cast<tr_piece_index_t>(byte_idx / piece_size());
}
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 } * piece_size()));
}
return loc;
}
// Location of the first byte in `block`.
[[nodiscard]] constexpr auto block_loc(tr_block_index_t const block) const noexcept
{
return byte_loc(uint64_t{ block } * BlockSize);
}
// Location of the first byte (+ optional offset and length) in `piece`
[[nodiscard]] constexpr auto piece_loc(tr_piece_index_t piece, uint32_t offset = {}, uint32_t length = {}) const noexcept
{
return byte_loc(uint64_t{ piece } * piece_size() + offset + length);
}
[[nodiscard]] constexpr tr_block_span_t block_span_for_piece(tr_piece_index_t const piece) const noexcept
{
if (!is_initialized())
{
return { 0U, 0U };
}
return { piece_loc(piece).block, piece_last_loc(piece).block + 1U };
}
[[nodiscard]] constexpr tr_byte_span_t byte_span_for_piece(tr_piece_index_t const piece) const noexcept
{
if (!is_initialized())
{
return { 0U, 0U };
}
auto const offset = piece_loc(piece).byte;
return { offset, offset + piece_size(piece) };
}
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private:
void init_sizes(uint64_t total_size_in, uint32_t piece_size_in) noexcept;
// Location of the last byte in `piece`.
[[nodiscard]] constexpr Location piece_last_loc(tr_piece_index_t const piece) const noexcept
{
return byte_loc(static_cast<uint64_t>(piece) * piece_size() + piece_size(piece) - 1);
}
[[nodiscard]] constexpr bool is_initialized() const noexcept
{
return piece_size_ != 0U;
}
uint64_t total_size_ = {};
tr_block_index_t n_blocks_ = {};
tr_piece_index_t n_pieces_ = {};
uint32_t final_block_size_ = {};
uint32_t piece_size_ = {};
uint32_t final_piece_size_ = {};
};