A C++ library for logging very fast and without allocating.
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#pragma once
#ifdef __cplusplus
#include <vector>
#include <chrono>
#endif
/**
* @brief Describes what should happen if the allocated buffer is full and no logs can be written
*/
enum SL_ON_SINK_FULL {
SL_OVERFLOW = 1, /**< When the sink is full, we want to drop the oldest data even if it is not written yet */
SL_WAIT = 2 /**< When the sink is full, we want to wait for the next write. Do that if log keeping is critical */
};
/**
* @brief Describes what type of IO should be used to log your data
*/
enum SL_SINK_IO_TYPE {
SL_DIRECT_IO = 1, /**< Use IO that ensure data is written on disk as soon as possible. Useful for debugging. */
SL_MMAPED_IO = 2, /**< Use IO that ensures that logging data will survive a software crash by using a memory mapped file as buffer. You can later expunge that buffer to get the useful information out. */
SL_FASTEST_IO = 3, /**< Write with the highest throughput. */
SL_EXTERNAL_IO = 4 /**< Do not handle any IO. Writes to a memory mapped file and let another process handle the IO. */
};
/**
* @brief What type of buffer should we use?
*/
enum SL_BUFFER_TYPE {
SL_EXTERNAL = 1, /**< Use a provided memory mapped non-temporary file */
SL_SHARED = 2, /**< Use an automatically generated temporary file */
SL_INTERNAL = 3 /**< Use internal memory. Compatible only with the SL_SINK_IO_TYPE: SL_DIRECT_IO and SL_FASTEST_IO. */
};
/**
* @brief On what basis do we generate new files for logs?
*/
enum SL_ROLL_LOGS {
SL_BY_TIME = 1, /**< Will create a new log every n-hours */
SL_BY_SIZE = 2, /**< Will create a new log every n-KB */
SL_NEVER = 0 /**< Will never split the log. Use when doing external logging. */
};
#ifndef __cplusplus
typedef enum SL_ON_SINK_FULL SL_ON_SINK_FULL;
typedef enum SL_SINK_IO_TYPE SL_SINK_IO_TYPE;
typedef enum SL_BUFFER_TYPE SL_BUFFER_TYPE;
typedef enum SL_ROLL_LOGS SL_ROLL_LOGS;
#endif
#ifdef __cpp_concepts
/**
* @brief Represents the behaviour if the buffer would be overflowing.
*/
enum class overflow_response_t {
must_wait = 0, /**< Represents that on overflow, the writer should wait using the strategy provided wait function. */
must_overflow = 1, /**< Represents that on overflow, the writer should push the fence and keep on writing immediately, even if the log would get corrupt. */
must_drop = must_wait /**< UNUSED, may be used in the future to mean that the current write should be dropped. */
};
/**
* @brief This concept maps an overflow strategy.
*/
template<typename T>
concept OverflowStrategy = requires (T strategy) {
{T::on_overflow} -> std::same_as<const overflow_response_t&>;
{strategy.wait()};
};
/**
* @brief This concept represents something that should be writable and mapped to valid memory within the software.
*
* @details This is used for mapping allocated buffers made from buffer strategies.
*/
template<typename T>
concept BufferLike = requires (T buffer) {
{buffer.data()} -> std::same_as<char*>;
{buffer.size()} -> std::same_as<size_t>;
};
/**
* @brief This concept maps a buffer strategy.
*/
template<typename T>
concept BufferStrategy = requires (T strategy, size_t size) {
{strategy.build_buffer(size)} -> BufferLike;
};
/**
* @brief This concept maps a sink strategy.
*/
template<typename T>
concept SinkStrategy = requires (T strategy, int fd, std::string_view data) {
{strategy.write(fd, data)};
};
/**
* @brief This concept maps an output strategy.
*/
template<typename T>
concept OutputStrategy = requires (T strategy, std::string_view source, int fd) {
{strategy.chunk(source)} -> std::same_as<std::pair<std::string_view, std::string_view>>;
{strategy.on_write_completed_event(source, fd)} -> std::same_as<int>;
};
#endif
#ifdef __cplusplus
#ifndef __cpp_concepts
#define OverflowStrategy typename
#define BufferStrategy typename
#define SinkStrategy typename
#define OutputStrategy typename
#endif
/**
* @brief Represent a mapped buffer. You should generally not touch this as it is internal representation for strategies.
*/
struct mapped_buffer {
char* _data;
size_t _size;
/**
* @return the data pointer of the buffer
*/
[[nodiscard]] char* data() const { return _data; }
/**
* @return the size of the allocated buffer
*/
[[nodiscard]] size_t size() const { return _size; }
};
struct BufferStrategyInternal {
using buffer_type = std::vector<char>;
static_assert(BufferLike<buffer_type>);
buffer_type build_buffer(size_t);
};
struct BufferStrategyShared {
using buffer_type = mapped_buffer;
static_assert(BufferLike<buffer_type>);
buffer_type build_buffer(size_t);
};
struct BufferStrategyExternal {
using buffer_type = mapped_buffer;
static_assert(BufferLike<buffer_type>);
buffer_type build_buffer(size_t);
};
struct SinkStrategyDirect {
void write(int fd, std::string_view data);
};
struct SinkStrategyFastest {
void write(int fd, std::string_view data);
};
struct SinkStrategyMmaped {
void write(int fd, std::string_view data);
};
struct SinkStrategyExternal {
void write(int fd, std::string_view data);
};
struct OverflowStrategyWait {
static constexpr overflow_response_t on_overflow = overflow_response_t::must_wait;
void wait();
};
struct OverflowStrategyContinue {
static constexpr overflow_response_t on_overflow = overflow_response_t::must_overflow;
void wait();
};
struct OutputStrategyTimed {
std::chrono::seconds interval;
std::chrono::time_point<std::chrono::file_clock> last_change;
std::pair<std::string_view, std::string_view> chunk(std::string_view);
int on_write_completed_event(std::string_view, int);
};
struct OutputStrategySized {
uint64_t interval;
uint64_t written_bytes;
std::pair<std::string_view, std::string_view> chunk(std::string_view);
int on_write_completed_event(std::string_view, int);
};
struct OutputStrategySimple {
std::pair<std::string_view, std::string_view> chunk(std::string_view);
int on_write_completed_event(std::string_view, int);
};
#endif