55 lines
1.7 KiB
C
55 lines
1.7 KiB
C
/*
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* Pixelflut binary UDP protocol, shared by the renderer and the benchmark.
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*
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* Packet layout (little-endian on the wire):
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*
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* +------+---------+ pixelflut_packet
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* | cmd | subcmd | 2-byte header
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* +------+---------+---------+----+----+----+ pixelflut_pixel[0]
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* | x (u16) | y (u16) | r | g | b | 7 bytes
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* +----------------+---------+----+----+----+
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* | ... | PIXELS_PER_PACKET pixels
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* +----------------------------------------+
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*/
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#ifndef PIXELFLUT_H
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#define PIXELFLUT_H
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#include <stdint.h>
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/* Header bytes. */
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#define PIXELFLUT_CMD_SET 0x00 /* "set pixels" command ... */
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#define PIXELFLUT_SUBCMD_RGB 0x01 /* ... with 3-byte RGB colours */
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/* Pixels batched into a single UDP datagram. Bigger datagrams amortize the
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* per-message send cost over more pixels; keep the packet within the path MTU
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* to avoid IP fragmentation (e.g. 207 pixels ~= 1451 B fits a 1500 B link).
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* Override at build time with -DPIXELS_PER_PACKET=N. */
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#ifndef PIXELS_PER_PACKET
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# define PIXELS_PER_PACKET 120
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#endif
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#pragma pack(push, 1)
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/* A single pixel as it appears on the wire. */
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struct pixelflut_pixel {
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uint16_t x; /* little-endian */
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uint16_t y; /* little-endian */
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uint8_t r;
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uint8_t g;
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uint8_t b;
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};
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/* A full datagram: header followed by a batch of pixels. */
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struct pixelflut_packet {
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uint8_t cmd;
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uint8_t subcmd;
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struct pixelflut_pixel pixels[PIXELS_PER_PACKET];
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};
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#pragma pack(pop)
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_Static_assert(sizeof(struct pixelflut_pixel) == 7,
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"pixel must be exactly 7 bytes on the wire");
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_Static_assert(sizeof(struct pixelflut_packet) == 2 + 7 * PIXELS_PER_PACKET,
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"packet must be header + PIXELS_PER_PACKET pixels, no padding");
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#endif /* PIXELFLUT_H */
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