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# 4c0b050e9a25 retro-remote-debug-controller / core / retro_control.h
3.7 KiB · Objective-C · last changed docs: full sweep to 0.3.0 / four platforms 3 months ago source blame history raw
961b3c61 Andy McCall 1 
/* retro_control.h — portable emulator control server (see ../SPEC.md).
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 *
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 * A retro-platform emulator implements the small read-only backend below and
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 * calls retro_control_start(). The shared server (retro_control.c) owns the
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 * socket loop, HTTP parsing, PPM/JSON encoding, and control flow
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 * (pause / step / free-run). It always binds 127.0.0.1. Contract version is
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 * RETRO_CONTROL_CONTRACT (below); the server advertises the highest level whose
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 * backend callbacks are all present.
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 *
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 * Integration is three calls in the emulator's main loop:
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 *   retro_control_service();                 // once per iteration (cheap)
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 *   if (!retro_control_running()) { idle; }  // gate advancing the machine
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 *   ... run one instruction / frame ...
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 *   if (frame_completed) retro_control_on_frame();
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 *
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 * Threading: the server runs on its own thread but never touches machine state
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 * there. State-reading endpoints (/mem, /regs, /screenshot) are executed inside
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 * retro_control_service() ON THE EMULATOR THREAD, so every read is consistent.
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 * The backend callbacks are therefore called from the emulator thread (except
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 * get_frame_count, which the server may also read for /status — make it a plain
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 * atomic-ish counter read).
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 */
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#ifndef RETRO_CONTROL_H
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#define RETRO_CONTROL_H
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#include <stdint.h>
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#include <stddef.h>
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#define RETRO_CONTROL_CONTRACT "0.1.0"
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/* Native framebuffer pixel layout; the server swizzles to PPM RGB. */
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typedef enum {
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    RETRO_PIX_RGB888 = 0,   /* 3 bytes/px: R,G,B                       */
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    RETRO_PIX_RGBA8888,     /* 4 bytes/px: R,G,B,A                     */
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    RETRO_PIX_BGRA8888      /* 4 bytes/px: B,G,R,A (x16 framebuffer)   */
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} retro_pix_fmt_t;
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typedef struct {
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    const uint8_t *pixels;  /* start of the current complete frame     */
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    int width;
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    int height;
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    retro_pix_fmt_t fmt;
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} retro_framebuffer_t;
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/* The emulator implements these. Any may be NULL: the matching endpoint then
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 * returns 501 Not Implemented. */
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typedef struct retro_control_backend {
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    const char *platform;   /* "x16" | "neo6502" | "agon" | ...        */
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    const char *emulator;   /* human name, e.g. "x16emu"               */
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    /* Debug-read up to min(len, out_cap) bytes at addr into out, side-effect
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     * free. bank is the optional bank selector (<0 = current bank). Returns the
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     * number of bytes written. */
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    uint32_t (*read_mem)(uint32_t addr, int32_t bank, uint32_t len,
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                         uint8_t *out, uint32_t out_cap);
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    /* Write a JSON object of registers into buf (NUL-terminated). */
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    void (*get_regs_json)(char *buf, size_t cap);
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    /* Report the current complete-frame framebuffer. */
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    void (*get_framebuffer)(retro_framebuffer_t *out);
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    /* Monotonic completed-frame counter. */
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    uint64_t (*get_frame_count)(void);
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} retro_control_backend_t;
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/* Start the server thread bound to 127.0.0.1:port. Non-blocking; 0 on success,
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 * negative on error. backend must outlive the server. */
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int  retro_control_start(int port, const retro_control_backend_t *backend);
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/* Drain a pending control request. Call once per main-loop iteration, at an
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 * instruction/frame boundary. Cheap no-op when idle and when control is off. */
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void retro_control_service(void);
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/* Nonzero => the machine should advance this iteration. Returns 1 always when
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 * control is off or the machine is free-running; 0 when paused with no steps
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 * left. */
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int  retro_control_running(void);
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/* Call when a video frame completes. Drives /step (decrements the step budget,
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 * halts and answers when it reaches zero). No-op when control is off. */
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void retro_control_on_frame(void);
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/* Stop the server (optional; process exit is fine too). */
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void retro_control_stop(void);
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#endif /* RETRO_CONTROL_H */