/*
 * Pixelflut binary UDP protocol, shared by the renderer and the benchmark.
 *
 * Packet layout (little-endian on the wire):
 *
 *   +------+---------+  pixelflut_packet
 *   | cmd  | subcmd  |  2-byte header
 *   +------+---------+---------+----+----+----+  pixelflut_pixel[0]
 *   |   x (u16)      | y (u16) | r  | g  | b  |  7 bytes
 *   +----------------+---------+----+----+----+
 *   |                   ...                   |  PIXELS_PER_PACKET pixels
 *   +----------------------------------------+
 */

#ifndef PIXELFLUT_H
#define PIXELFLUT_H

#include <stdint.h>

/* Header bytes. */
#define PIXELFLUT_CMD_SET    0x00 /* "set pixels" command ... */
#define PIXELFLUT_SUBCMD_RGB 0x01 /* ... with 3-byte RGB colours */

/* Pixels batched into a single UDP datagram. */
#define PIXELS_PER_PACKET 120

#pragma pack(push, 1)
/* A single pixel as it appears on the wire. */
struct pixelflut_pixel {
	uint16_t x; /* little-endian */
	uint16_t y; /* little-endian */
	uint8_t r;
	uint8_t g;
	uint8_t b;
};

/* A full datagram: header followed by a batch of pixels. */
struct pixelflut_packet {
	uint8_t cmd;
	uint8_t subcmd;
	struct pixelflut_pixel pixels[PIXELS_PER_PACKET];
};
#pragma pack(pop)

_Static_assert(sizeof(struct pixelflut_pixel) == 7,
               "pixel must be exactly 7 bytes on the wire");
_Static_assert(sizeof(struct pixelflut_packet) == 2 + 7 * PIXELS_PER_PACKET,
               "packet must be header + PIXELS_PER_PACKET pixels, no padding");

#endif /* PIXELFLUT_H */