77 lines
2.7 KiB
C
77 lines
2.7 KiB
C
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/**
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* slot.h — Framecache shared memory slot definitions.
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*
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* Layout per slot (/dev/shm/framecache/<slot_id>):
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* [fc_header_t — 4KB aligned]
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* [fc_frame_t × ring_depth — each FC_FRAME_HDR_SIZE + frame_size bytes]
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*
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* Writer advances write_cursor atomically and posts the named semaphore.
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* Each consumer tracks its own read_cursor independently — writer never blocks.
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*/
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#pragma once
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#include <stdint.h>
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#include <stdatomic.h>
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#include <semaphore.h>
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#define FC_MAGIC 0x46524D43u /* "FRMC" */
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#define FC_VERSION 1u
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#define FC_RING_DEPTH 120u /* ~2s at 59.94fps */
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#define FC_HEADER_SIZE 4096u /* 4KB header block */
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#define FC_FRAME_HDR_SIZE 24u /* pts_us(8) + wall_us(8) + size(4) + pad(4) */
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#define FC_MAX_SLOT_ID 64u
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/* Pixel format codes */
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#define FC_PIX_UYVY422 0u
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typedef struct {
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uint32_t magic; /* FC_MAGIC */
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uint32_t version; /* FC_VERSION */
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uint32_t width;
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uint32_t height;
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uint32_t fps_num;
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uint32_t fps_den;
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uint32_t pixel_format; /* FC_PIX_UYVY422 */
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uint32_t frame_size; /* width * height * 2 */
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uint32_t ring_depth; /* FC_RING_DEPTH */
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uint32_t _reserved;
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_Atomic uint64_t write_cursor; /* monotonically increasing frame index */
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_Atomic uint64_t dropped_frames;
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char source_type[32]; /* "deltacast" | "blackmagic" | "srt" | "rtmp" */
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char slot_id[FC_MAX_SLOT_ID];
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uint8_t _pad[FC_HEADER_SIZE - 112];
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} fc_header_t;
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/* Per-frame metadata + data (variable length — use fc_frame_at() accessor) */
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typedef struct {
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uint64_t pts_us;
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uint64_t wall_us;
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uint32_t size;
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uint32_t _pad;
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uint8_t data[]; /* frame_size bytes */
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} fc_frame_t;
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/* Compile-time size check */
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_Static_assert(sizeof(fc_header_t) == FC_HEADER_SIZE,
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"fc_header_t must be exactly FC_HEADER_SIZE bytes");
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_Static_assert(sizeof(fc_frame_t) == FC_FRAME_HDR_SIZE,
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"fc_frame_t header must be exactly FC_FRAME_HDR_SIZE bytes");
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/**
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* Compute total shm size for a slot given frame_size.
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* = FC_HEADER_SIZE + ring_depth * (FC_FRAME_HDR_SIZE + frame_size)
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*/
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static inline size_t fc_slot_shm_size(uint32_t frame_size) {
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return (size_t)FC_HEADER_SIZE
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+ (size_t)FC_RING_DEPTH * ((size_t)FC_FRAME_HDR_SIZE + frame_size);
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}
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/**
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* Return pointer to frame at ring index idx within a mapped shm base.
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*/
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static inline fc_frame_t *fc_frame_at(void *base, uint32_t frame_size, uint64_t idx) {
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uint8_t *frames = (uint8_t *)base + FC_HEADER_SIZE;
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return (fc_frame_t *)(frames + (idx % FC_RING_DEPTH)
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* ((size_t)FC_FRAME_HDR_SIZE + frame_size));
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}
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