Add BytePusher example

examples/CMakeLists.txt

@@ -143,6 +143,7 @@ add_sdl_example_executable(pen-drawing-lines SOURCES pen/01-drawing-lines/drawin
 add_sdl_example_executable(game-snake SOURCES game/01-snake/snake.c)
 add_sdl_example_executable(game-woodeneye-008 SOURCES game/02-woodeneye-008/woodeneye-008.c)
 add_sdl_example_executable(game-infinite-monkeys SOURCES game/03-infinite-monkeys/infinite-monkeys.c)
+add_sdl_example_executable(game-bytepusher SOURCES game/04-bytepusher/bytepusher.c)
 
 # When you add an example, remember to add the Visual Studio project as well:
 # - Add a new example in examples/

examples/game/04-bytepusher/README.txt

@@ -0,0 +1,4 @@
+An implementation of the BytePusher VM
+
+For example programs and more information about BytePusher, see
+https://esolangs.org/wiki/BytePusher

examples/game/04-bytepusher/bytepusher.c

@@ -0,0 +1,428 @@
+/*
+ * An implementation of the BytePusher VM.
+ *
+ * For example programs and more information about BytePusher, see
+ * https://esolangs.org/wiki/BytePusher
+ *
+ * This code is public domain. Feel free to use it for any purpose!
+ */
+
+#define SDL_MAIN_USE_CALLBACKS
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+#include <stdarg.h>
+
+#define SCREEN_W 256
+#define SCREEN_H 256
+#define RAM_SIZE 0x1000000
+#define FRAMES_PER_SECOND 60
+#define SAMPLES_PER_FRAME 256
+#define NS_PER_SECOND (Uint64)SDL_NS_PER_SECOND
+#define MAX_AUDIO_LATENCY_FRAMES 5
+
+#define IO_KEYBOARD 0
+#define IO_PC 2
+#define IO_SCREEN_PAGE 5
+#define IO_AUDIO_BANK 6
+
+typedef struct {
+    Uint8 ram[RAM_SIZE + 8];
+    Uint8 screenbuf[SCREEN_W * SCREEN_H];
+    Uint64 last_tick;
+    Uint64 tick_acc;
+    SDL_Window* window;
+    SDL_Renderer* renderer;
+    SDL_Surface* screen; 
+    SDL_Texture* screentex;
+    SDL_Texture* rendertarget; /* we need this render target for text to look good */
+    SDL_AudioStream* audiostream;
+    char status[SCREEN_W / 8];
+    int status_ticks;
+    Uint16 keystate;
+    bool display_help;
+    bool positional_input;
+} BytePusher;
+
+static const struct {
+    const char *key;
+    const char *value;
+} extended_metadata[] = {
+    { SDL_PROP_APP_METADATA_URL_STRING, "https://examples.libsdl.org/SDL3/game/04-bytepusher/" },
+    { SDL_PROP_APP_METADATA_CREATOR_STRING, "SDL team" },
+    { SDL_PROP_APP_METADATA_COPYRIGHT_STRING, "Placed in the public domain" },
+    { SDL_PROP_APP_METADATA_TYPE_STRING, "game" }
+};
+
+static inline Uint16 read_u16(const BytePusher* vm, Uint32 addr) {
+    const Uint8* ptr = &vm->ram[addr];
+    return ((Uint16)ptr[0] << 8) | ((Uint16)ptr[1]);
+}
+
+static inline Uint32 read_u24(const BytePusher* vm, Uint32 addr) {
+    const Uint8* ptr = &vm->ram[addr];
+    return ((Uint32)ptr[0] << 16) | ((Uint32)ptr[1] << 8) | ((Uint32)ptr[2]);
+}
+
+static void set_status(BytePusher* vm, const char* fmt, ...) {
+    va_list args;
+    va_start(args, fmt);
+    SDL_vsnprintf(vm->status, sizeof(vm->status), fmt, args);
+    va_end(args);
+    vm->status[sizeof(vm->status) - 1] = 0;
+    vm->status_ticks = FRAMES_PER_SECOND * 3;
+}
+
+static bool load(BytePusher* vm, SDL_IOStream* stream, bool closeio) {
+    size_t bytes_read = 0;
+    bool ok = true;
+
+    SDL_memset(vm->ram, 0, RAM_SIZE);
+
+    if (!stream) {
+        return false;
+    }
+
+    while (bytes_read < RAM_SIZE) {
+        size_t read = SDL_ReadIO(stream, &vm->ram[bytes_read], RAM_SIZE - bytes_read);
+        bytes_read += read;
+        if (read == 0) {
+            ok = SDL_GetIOStatus(stream) == SDL_IO_STATUS_EOF;
+            break;
+        }
+    }
+    if (closeio) {
+        SDL_CloseIO(stream);
+    }
+
+    SDL_ClearAudioStream(vm->audiostream);
+
+    vm->display_help = !ok;
+    return ok;
+}
+
+static const char* filename(const char* path) {
+    size_t i = SDL_strlen(path) + 1;
+    while (i > 0) {
+        i -= 1;
+        if (path[i] == '/' || path[i] == '\\') {
+            return path + i + 1;
+        }
+    }
+    return path;
+}
+
+static bool load_file(BytePusher* vm, const char* path) {
+    if (load(vm, SDL_IOFromFile(path, "rb"), true)) {
+        set_status(vm, "loaded %s", filename(path));
+        return true;
+    } else {
+        set_status(vm, "load failed: %s", filename(path));
+        return false;
+    }
+}
+
+static void print(BytePusher* vm, int x, int y, const char* str) {
+    SDL_SetRenderDrawColor(vm->renderer, 0, 0, 0, SDL_ALPHA_OPAQUE);
+    SDL_RenderDebugText(vm->renderer, (float)(x + 1), (float)(y + 1), str);
+    SDL_SetRenderDrawColor(vm->renderer, 0xff, 0xff, 0xff, SDL_ALPHA_OPAQUE);
+    SDL_RenderDebugText(vm->renderer, (float)x, (float)y, str);
+    SDL_SetRenderDrawColor(vm->renderer, 0, 0, 0, SDL_ALPHA_OPAQUE);
+}
+
+SDL_AppResult SDL_AppInit(void** appstate, int argc, char* argv[]) {
+    BytePusher* vm;
+    SDL_Palette* palette;
+    SDL_Rect usable_bounds;
+    SDL_AudioSpec audiospec = { SDL_AUDIO_S8, 1, SAMPLES_PER_FRAME * FRAMES_PER_SECOND };
+    SDL_DisplayID primary_display;
+    SDL_PropertiesID texprops;
+    int zoom = 2;
+    int i;
+    Uint8 r, g, b;
+    (void)argc;
+    (void)argv;
+
+    if (!SDL_SetAppMetadata("SDL 3 BytePusher", "1.0", "com.example.SDL3BytePusher")) {
+        return SDL_APP_FAILURE;
+    }
+
+    for (i = 0; i < (int)SDL_arraysize(extended_metadata); i++) {
+        if (!SDL_SetAppMetadataProperty(extended_metadata[i].key, extended_metadata[i].value)) {
+            return SDL_APP_FAILURE;
+        }
+    }
+
+    if (!SDL_Init(SDL_INIT_AUDIO | SDL_INIT_VIDEO)) {
+        return SDL_APP_FAILURE;
+    }
+
+    if (!(vm = SDL_calloc(1, sizeof(*vm)))) {
+        return SDL_APP_FAILURE;
+    }
+    *(BytePusher**)appstate = vm;
+
+    vm->display_help = true;
+
+    primary_display = SDL_GetPrimaryDisplay();
+    if (SDL_GetDisplayUsableBounds(primary_display, &usable_bounds)) {
+        int zoom_w = (usable_bounds.w - usable_bounds.x) * 2 / 3 / SCREEN_W;
+        int zoom_h = (usable_bounds.h - usable_bounds.y) * 2 / 3 / SCREEN_H;
+        zoom = zoom_w < zoom_h ? zoom_w : zoom_h;
+        if (zoom < 1) {
+            zoom = 1;
+        }
+    }
+
+    if (!SDL_CreateWindowAndRenderer("SDL 3 BytePusher",
+        SCREEN_W * zoom, SCREEN_H * zoom, SDL_WINDOW_RESIZABLE,
+        &vm->window, &vm->renderer
+    )) {
+        return SDL_APP_FAILURE;
+    }
+
+    if (!SDL_SetRenderLogicalPresentation(
+        vm->renderer, SCREEN_W, SCREEN_H, SDL_LOGICAL_PRESENTATION_INTEGER_SCALE
+    )) {
+        return SDL_APP_FAILURE;
+    }
+
+    if (!(vm->screen = SDL_CreateSurfaceFrom(
+        SCREEN_W, SCREEN_H, SDL_PIXELFORMAT_INDEX8, vm->screenbuf, SCREEN_W
+    ))) {
+        return SDL_APP_FAILURE;
+    }
+
+    if (!(palette = SDL_CreateSurfacePalette(vm->screen))) {
+        return SDL_APP_FAILURE;
+    }
+    i = 0;
+    for (r = 0; r < 6; ++r) {
+        for (g = 0; g < 6; ++g) {
+            for (b = 0; b < 6; ++b, ++i) {
+                SDL_Color color = { r * 0x33, g * 0x33, b * 0x33, SDL_ALPHA_OPAQUE };
+                palette->colors[i] = color;
+            }
+        }
+    }
+    for (; i < 256; ++i) {
+        SDL_Color color = { 0, 0, 0, SDL_ALPHA_OPAQUE };
+        palette->colors[i] = color;
+    }
+
+    texprops = SDL_CreateProperties();
+    SDL_SetNumberProperty(texprops, SDL_PROP_TEXTURE_CREATE_ACCESS_NUMBER, SDL_TEXTUREACCESS_STREAMING);
+    SDL_SetNumberProperty(texprops, SDL_PROP_TEXTURE_CREATE_WIDTH_NUMBER, SCREEN_W);
+    SDL_SetNumberProperty(texprops, SDL_PROP_TEXTURE_CREATE_HEIGHT_NUMBER, SCREEN_H);
+    vm->screentex = SDL_CreateTextureWithProperties(vm->renderer, texprops);
+    SDL_SetNumberProperty(texprops, SDL_PROP_TEXTURE_CREATE_ACCESS_NUMBER, SDL_TEXTUREACCESS_TARGET);
+    vm->rendertarget = SDL_CreateTextureWithProperties(vm->renderer, texprops);
+    SDL_DestroyProperties(texprops);
+    if (!vm->screentex || !vm->rendertarget) {
+        return SDL_APP_FAILURE;
+    }
+    SDL_SetTextureScaleMode(vm->screentex, SDL_SCALEMODE_NEAREST);
+    SDL_SetTextureScaleMode(vm->rendertarget, SDL_SCALEMODE_NEAREST);
+
+    if (!(vm->audiostream = SDL_OpenAudioDeviceStream(
+        SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, &audiospec, NULL, NULL
+    ))) {
+        return SDL_APP_FAILURE;
+    }
+    SDL_SetAudioStreamGain(vm->audiostream, 0.1f); /* examples are loud! */
+    SDL_ResumeAudioStreamDevice(vm->audiostream);
+
+    set_status(vm, "renderer: %s", SDL_GetRendererName(vm->renderer));
+
+    vm->last_tick = SDL_GetTicksNS();
+    vm->tick_acc = NS_PER_SECOND;
+
+    return SDL_APP_CONTINUE;
+}
+
+SDL_AppResult SDL_AppIterate(void* appstate) {
+    BytePusher* vm = (BytePusher*)appstate;
+
+    Uint64 tick = SDL_GetTicksNS();
+    Uint64 delta = tick - vm->last_tick;
+    bool updated, skip_audio;
+
+    vm->last_tick = tick;
+
+    vm->tick_acc += delta * FRAMES_PER_SECOND;
+    updated = vm->tick_acc >= NS_PER_SECOND;
+    skip_audio = vm->tick_acc >= MAX_AUDIO_LATENCY_FRAMES * NS_PER_SECOND;
+
+    if (skip_audio) {
+        // don't let audio fall too far behind
+        SDL_ClearAudioStream(vm->audiostream);
+    }
+
+    while (vm->tick_acc >= NS_PER_SECOND) {
+        Uint32 pc;
+        int i;
+
+        vm->tick_acc -= NS_PER_SECOND;
+
+        vm->ram[IO_KEYBOARD] = (Uint8)(vm->keystate >> 8);
+        vm->ram[IO_KEYBOARD + 1] = (Uint8)(vm->keystate);
+
+        pc = read_u24(vm, IO_PC);
+        for (i = 0; i < SCREEN_W * SCREEN_H; ++i) {
+            Uint32 src = read_u24(vm, pc);
+            Uint32 dst = read_u24(vm, pc + 3);
+            vm->ram[dst] = vm->ram[src];
+            pc = read_u24(vm, pc + 6);
+        }
+
+        if (!skip_audio || vm->tick_acc < NS_PER_SECOND) {
+            SDL_PutAudioStreamData(
+                vm->audiostream,
+                &vm->ram[(Uint32)read_u16(vm, IO_AUDIO_BANK) << 8],
+                SAMPLES_PER_FRAME
+            );
+        }
+    }
+
+    if (updated) {
+        SDL_Surface *tex;
+
+        SDL_SetRenderTarget(vm->renderer, vm->rendertarget);
+
+        if (!SDL_LockTextureToSurface(vm->screentex, NULL, &tex)) {
+            return SDL_APP_FAILURE;
+        }
+        vm->screen->pixels = &vm->ram[(Uint32)vm->ram[IO_SCREEN_PAGE] << 16];
+        SDL_BlitSurface(vm->screen, NULL, tex, NULL);
+        SDL_UnlockTexture(vm->screentex);
+
+        SDL_RenderTexture(vm->renderer, vm->screentex, NULL, NULL);
+    }
+
+    if (vm->display_help) {
+        print(vm, 4, 4, "Drop a BytePusher file in this");
+        print(vm, 8, 12, "window to load and run it!");
+        print(vm, 4, 28, "Press ENTER to switch between");
+        print(vm, 8, 36, "positional and symbolic input.");
+    }
+
+    if (vm->status_ticks > 0) {
+        vm->status_ticks -= 1;
+        print(vm, 4, SCREEN_H - 12, vm->status);
+    }
+
+    SDL_SetRenderTarget(vm->renderer, NULL);
+    SDL_RenderClear(vm->renderer);
+    SDL_RenderTexture(vm->renderer, vm->rendertarget, NULL, NULL);
+    SDL_RenderPresent(vm->renderer);
+
+    return SDL_APP_CONTINUE;
+}
+
+static Uint16 keycode_mask(SDL_Keycode key) {
+    int index;
+    if (key >= SDLK_0 && key <= SDLK_9) {
+        index = key - SDLK_0;
+    } else if (key >= SDLK_A && key <= SDLK_F) {
+        index = key - SDLK_A + 10;
+    } else {
+        return 0;
+    }
+    return (Uint16)1 << index;
+}
+
+static Uint16 scancode_mask(SDL_Scancode scancode) {
+    int index;
+    switch (scancode) {
+        case SDL_SCANCODE_1: index = 0x1; break;
+        case SDL_SCANCODE_2: index = 0x2; break;
+        case SDL_SCANCODE_3: index = 0x3; break;
+        case SDL_SCANCODE_4: index = 0xc; break;
+        case SDL_SCANCODE_Q: index = 0x4; break;
+        case SDL_SCANCODE_W: index = 0x5; break;
+        case SDL_SCANCODE_E: index = 0x6; break;
+        case SDL_SCANCODE_R: index = 0xd; break;
+        case SDL_SCANCODE_A: index = 0x7; break;
+        case SDL_SCANCODE_S: index = 0x8; break;
+        case SDL_SCANCODE_D: index = 0x9; break;
+        case SDL_SCANCODE_F: index = 0xe; break;
+        case SDL_SCANCODE_Z: index = 0xa; break;
+        case SDL_SCANCODE_X: index = 0x0; break;
+        case SDL_SCANCODE_C: index = 0xb; break;
+        case SDL_SCANCODE_V: index = 0xf; break;
+        default: return 0;
+    }
+    return (Uint16)1 << index;
+}
+
+SDL_AppResult SDL_AppEvent(void* appstate, SDL_Event* event) {
+    BytePusher* vm = (BytePusher*)appstate;
+
+    switch (event->type) {
+        case SDL_EVENT_QUIT:
+            return SDL_APP_SUCCESS;
+
+        case SDL_EVENT_DROP_FILE:
+            load_file(vm, event->drop.data);
+            break;
+        
+        case SDL_EVENT_KEY_DOWN:
+#ifndef __EMSCRIPTEN__
+            if (event->key.key == SDLK_ESCAPE) {
+                return SDL_APP_SUCCESS;
+            }
+#endif
+            if (event->key.key == SDLK_RETURN) {
+                vm->positional_input = !vm->positional_input;
+                vm->keystate = 0;
+                if (vm->positional_input) {
+                    set_status(vm, "switched to positional input");
+                } else {
+                    set_status(vm, "switched to symbolic input");
+                }
+            }
+            if (vm->positional_input) {
+                vm->keystate |= scancode_mask(event->key.scancode);
+            } else {
+                vm->keystate |= keycode_mask(event->key.key);
+            }
+            break;
+        
+        case SDL_EVENT_KEY_UP: 
+            if (vm->positional_input) {
+                vm->keystate &= ~scancode_mask(event->key.scancode);
+            } else {
+                vm->keystate &= ~keycode_mask(event->key.key);
+            }
+            break;
+    }
+
+    return SDL_APP_CONTINUE;
+}
+
+void SDL_AppQuit(void* appstate, SDL_AppResult result) {
+    if (result == SDL_APP_FAILURE) {
+        SDL_Log("Error: %s", SDL_GetError());
+    }
+    if (appstate) {
+        BytePusher* vm = (BytePusher*)appstate;
+        if (vm->audiostream) {
+            SDL_DestroyAudioStream(vm->audiostream);
+        }
+        if (vm->rendertarget) {
+            SDL_DestroyTexture(vm->rendertarget);
+        }
+        if (vm->screentex) {
+            SDL_DestroyTexture(vm->screentex);
+        }
+        if (vm->screen) {
+            SDL_DestroySurface(vm->screen);
+        }
+        if (vm->renderer) {
+            SDL_DestroyRenderer(vm->renderer);
+        }
+        if (vm->window) {
+            SDL_DestroyWindow(vm->window);
+        }
+        SDL_free(vm);
+    }
+}