// SPDX-License-Identifier: LGPL-3.0-or-later

/**
 * \file bgp/bytebuf.h
 *
 * Allocator optimized for trivial BGP workflows.
 *
 * \copyright The DoubleFourteen Code Forge (C) All Rights Reserved
 * \author    Lorenzo Cogotti
 */

#ifndef DF_BGP_MEMBUF_H_
#define DF_BGP_MEMBUF_H_

#include "mem.h"

/// Memory alignment for `Bgpbytebuf` allocations.
#define BGP_MEMBUF_ALIGN 4

// NOTE: Need at least 4 bytes alignment for TABLE_DUMPV2 peer lookup tables!

/**
 * \brief Basic fixed-size packed single-threaded byte buffer.
 *
 * Nearly zero-overhead byte pool optimized for typical BGP message
 * allocations. Returns chunks from an internal fixed-size byte buffer
 */
typedef struct {
	size_t size;                                        ///< Buffer block size in bytes
	size_t pos;                                         ///< Current position inside block
	ALIGNED(BGP_MEMBUF_ALIGN, Uint8 base[FLEX_ARRAY]);  ///< Block buffer
} Bgpbytebuf;

/**
 * \brief Create `Bgpbytebuf` with statically sized fixed buffer
 *        (as opposed to a flexible array buffer).
 *
 * This is useful when the buffer should be placed in statically
 * allocated variable, e.g.
 * ```c
 * static BGP_FIXBYTEBUF(4096) bgp_msgBuf = { 4096 };
 * ```
 *
 * May also be used for a `typedef`:
 * ```c
 * typedef BGP_FIXBYTEBUF(1024) Bgpsmallbuf;
 * ```
 *
 * Variables generated by this macro may be used
 * as `allocp` of any API expecting a `MemOps` interface.
 */
#define BGP_FIXBYTEBUF(bufsiz) \
	struct { \
		size_t size;                                   \
		size_t pos;                                    \
		ALIGNED(BGP_MEMBUF_ALIGN, Uint8 base[bufsiz]); \
	}

/// `MemOps` operating over `Bgpbytebuf`, use pointer to `Bgpbytebuf` as `allocp`.
extern const MemOps *const Mem_BgpBufOps;

#endif