cvmmap-streamer/include/cvmmap_streamer/ipc/contracts.hpp

#pragma once

#include <algorithm>
#include <array>
#include <cstddef>
#include <cstdint>
#include <expected>
#include <functional>
#include <span>
#include <string_view>

namespace cvmmap_streamer::ipc {

constexpr std::size_t kLabelLenMax      = 24;
constexpr std::size_t kShmPayloadOffset = 256;

constexpr std::uint8_t kFrameTopicMagic      = 0x7d;
constexpr std::uint8_t kModuleStatusMagic    = 0x5a;
constexpr std::uint8_t kControlRequestMagic  = 0x3c;
constexpr std::uint8_t kControlResponseMagic = 0x3d;
constexpr std::uint8_t kVersionMajor         = 1;
constexpr std::uint8_t kVersionMinor         = 0;

constexpr std::array<std::uint8_t, 8> kFrameMetadataMagic{
	'C', 'V', '-', 'M', 'M', 'A', 'P', '\0'};

enum class Depth : std::uint8_t {
	U8  = 0,
	S8  = 1,
	U16 = 2,
	S16 = 3,
	S32 = 4,
	F32 = 5,
	F64 = 6,
	F16 = 7,
};

enum class PixelFormat : std::uint8_t {
	RGB = 0,
	BGR,
	RGBA,
	BGRA,
	GRAY,
	YUV,
	YUYV,
};

enum class ModuleStatus : std::int32_t {
	Online      = 0xa1,
	Offline     = 0xa0,
	StreamReset = 0xb0,
};

enum class ParseError {
	BufferTooSmall,
	InvalidSize,
	InvalidMagic,
	UnsupportedVersion,
	InvalidDepth,
	InvalidPixelFormat,
	InvalidModuleStatus,
	PayloadLengthMismatch,
};

enum class SnapshotError {
	InvalidShmLayout,
	DestinationTooSmall,
	TornRead,
};

std::string_view to_string(ParseError error);
std::string_view to_string(SnapshotError error);

struct FrameInfo {
	std::uint16_t width;
	std::uint16_t height;
	std::uint8_t channels;
	Depth depth;
	PixelFormat pixel_format;
	std::uint32_t buffer_size;
};

struct FrameMetadata {
	std::array<std::uint8_t, kFrameMetadataMagic.size()> magic;
	std::uint8_t versions_major;
	std::uint8_t versions_minor;
	std::uint32_t frame_count;
	std::uint64_t timestamp_ns;
	FrameInfo info;
};

struct SyncMessage {
	std::uint8_t versions_major;
	std::uint8_t versions_minor;
	std::uint32_t frame_count;
	std::uint64_t timestamp_ns;
	std::array<std::uint8_t, kLabelLenMax> label_bytes;

	[[nodiscard]]
	std::string_view label() const {
		const auto end = std::find(label_bytes.begin(), label_bytes.end(), static_cast<std::uint8_t>(0));
		return std::string_view{
			reinterpret_cast<const char *>(label_bytes.data()),
			static_cast<std::size_t>(std::distance(label_bytes.begin(), end))};
	}
};

struct ModuleStatusMessage {
	std::uint8_t versions_major;
	std::uint8_t versions_minor;
	ModuleStatus module_status;
	std::array<std::uint8_t, kLabelLenMax> label_bytes;

	[[nodiscard]]
	std::string_view label() const {
		const auto end = std::find(label_bytes.begin(), label_bytes.end(), static_cast<std::uint8_t>(0));
		return std::string_view{
			reinterpret_cast<const char *>(label_bytes.data()),
			static_cast<std::size_t>(std::distance(label_bytes.begin(), end))};
	}
};

struct ControlRequestMessage {
	std::uint8_t versions_major;
	std::uint8_t versions_minor;
	std::int32_t command_id;
	std::array<std::uint8_t, kLabelLenMax> label_bytes;
	std::span<const std::uint8_t> request_payload;

	[[nodiscard]]
	std::string_view label() const {
		const auto end = std::find(label_bytes.begin(), label_bytes.end(), static_cast<std::uint8_t>(0));
		return std::string_view{
			reinterpret_cast<const char *>(label_bytes.data()),
			static_cast<std::size_t>(std::distance(label_bytes.begin(), end))};
	}
};

struct ControlResponseMessage {
	std::uint8_t versions_major;
	std::uint8_t versions_minor;
	std::int32_t command_id;
	std::int32_t response_code;
	std::array<std::uint8_t, kLabelLenMax> label_bytes;
	std::span<const std::uint8_t> response_payload;

	[[nodiscard]]
	std::string_view label() const {
		const auto end = std::find(label_bytes.begin(), label_bytes.end(), static_cast<std::uint8_t>(0));
		return std::string_view{
			reinterpret_cast<const char *>(label_bytes.data()),
			static_cast<std::size_t>(std::distance(label_bytes.begin(), end))};
	}
};

struct ValidatedShmView {
	FrameMetadata metadata;
	std::span<const std::uint8_t> payload;
};

struct CoherentSnapshot {
	FrameMetadata metadata;
	std::size_t bytes_copied;
};

using SnapshotReadHook = std::function<void()>;

std::expected<FrameMetadata, ParseError> parse_frame_metadata(std::span<const std::uint8_t> bytes);
std::expected<SyncMessage, ParseError> parse_sync_message(std::span<const std::uint8_t> bytes);
std::expected<ModuleStatusMessage, ParseError> parse_module_status_message(std::span<const std::uint8_t> bytes);
std::expected<ControlRequestMessage, ParseError> parse_control_request_message(std::span<const std::uint8_t> bytes);
std::expected<ControlResponseMessage, ParseError> parse_control_response_message(std::span<const std::uint8_t> bytes);

std::expected<ValidatedShmView, ParseError> validate_shm_region(std::span<const std::uint8_t> shm_region);

std::expected<CoherentSnapshot, SnapshotError> read_coherent_snapshot(
	std::span<const std::uint8_t> shm_region,
	std::span<std::uint8_t> destination,
	const SnapshotReadHook &before_second_metadata_read = {});

}