Proper memory allocators

build/assets/stdlib.c

@@ -3,6 +3,12 @@
 #define BLOCK_SIZE (64 * 1024)
 #define BLOCK_1MB 16
 
+typedef struct header {
+    size_t size : 31;
+    uint8_t is_free : 1;
+} header_t;
+static header_t* head;
+
 static uintptr_t bump_pointer = (uintptr_t)&__heap_base;
 static uintptr_t heap_end = BLOCK_1MB * BLOCK_SIZE;
 IMPORT(grow) void grow(uint32_t blocks);
@@ -19,11 +25,117 @@ static void* bump_alloc(uintptr_t n) {
     return (void*)r;
 }
 
-void* malloc(uintptr_t n) {
-    return bump_alloc(n);
+static header_t* get_next_header(header_t* block) {
+    if (!block) {
+        return NULL;
+    }
+    uint8_t* data = (uint8_t*)(block + 1);
+    uint8_t* next_header = data + block->size;
+    if ((uintptr_t)next_header >= bump_pointer) {
+        return NULL;
+    }
+    return (header_t*)next_header;
 }
 
-void free(void* p) { (void)p; }
+static header_t* get_prev_header(header_t* block) {
+    header_t* curr = head;
+    while (curr) {
+        header_t* next = get_next_header(curr);
+        if (next == block) {
+            return curr;
+        }
+        curr = next;
+    }
+    return NULL;
+}
+
+static header_t* get_free_block(size_t size) {
+    header_t* curr = head;
+    while (curr) {
+        if (curr->is_free && curr->size >= size) {
+            return curr;
+        }
+        curr = get_next_header(curr);
+    }
+    return NULL;
+}
+
+void* malloc(size_t size) {
+    if (!size) {
+        return NULL;
+    }
+
+    header_t* header = get_free_block(size);
+    if (header) {
+        header->is_free = 0;
+        if (header->size > size + sizeof(header_t) * 2) {
+            size_t old_size = header->size;
+            header->size = size;
+
+            header_t* next = get_next_header(header);
+            next->size = old_size - size - sizeof(header_t);
+            next->is_free = 1;
+        }
+        return (void*)(header + 1);
+    }
+    size_t total_size = sizeof(header_t) + size;
+
+    void* block = bump_alloc(total_size);
+    if (!block) {
+        return NULL;
+    }
+
+    header = block;
+    header->size = size;
+    header->is_free = 0;
+
+    if (!head) {
+        head = header;
+    }
+
+    return (void*)(header + 1);
+}
+
+void free(void* block) {
+    if (!block) {
+        return;
+    }
+
+    header_t* header = ((header_t*)block) - 1;
+    if (header->is_free) {
+        return;
+    }
+    header->is_free = 1;
+
+    header_t* next_header = get_next_header(header);
+    if (next_header && next_header->is_free) {
+        header->size += next_header->size + sizeof(header_t);
+    }
+
+    header_t* prev_header = get_prev_header(header);
+    if (prev_header && prev_header->is_free) {
+        prev_header->size += header->size + sizeof(header_t);
+    }
+}
+
+void* realloc(void* block, size_t size) {
+    header_t* header;
+    void* ret;
+
+    if (!block || !size)
+        return malloc(size);
+
+    header = (header_t*)block - 1;
+    if (header->size >= size)
+        return block;
+
+    ret = malloc(size);
+    if (ret) {
+        memcpy(ret, block, header->size);
+        free(block);
+    }
+    return ret;
+}
 
 void* memset(void* s, uint8_t c, uint32_t n) {
     uint8_t* p = (uint8_t*)s;

build/assets/stdlib.h

@@ -6,8 +6,12 @@ extern unsigned char __heap_base;
 #define IMPORT(name) __attribute__((import_module("env"), import_name(#name)))
 #define EXPORT(name) __attribute__((export_name(#name)))
 
-EXPORT(malloc) void* malloc(uintptr_t);
-void free(void*);
+#define NULL ((void*)0)
+
+typedef uint32_t size_t;
+
+EXPORT(malloc) void* malloc(size_t);
+EXPORT(free) void free(void*);
 
 void* memset(void* s, uint8_t c, uint32_t n);
 void* memcpy(void* dest, const void* src, uint32_t n);

src/games/life/index.ts

@@ -8,12 +8,12 @@ const canvas = createCanvas(width, height);
 const context = canvas.getContext('2d')!;
 const imageData = context.createImageData(width, height);
 
-const initField = life.initField as CallableFunction;
 const step = life.step as CallableFunction;
-const pixels = new Uint8Array(life.memory.buffer, life.getPixels(), width * height * 4);
+let pixels: Uint8Array;
 
 export default function main() {
-    initField(Date.now());
+    const pixelsPtr = life.initField(Date.now());
+    pixels = new Uint8Array(life.memory.buffer, pixelsPtr, width * height * 4);
 
     console.log(life, pixels.length);
 

src/games/life/life.c

@@ -4,27 +4,28 @@
 #define width 512
 #define height 512
 
-static uint8_t field[width * height];
-static uint8_t nextField[width * height];
-static uint8_t pixels[width * height * 4];
+static uint8_t* field;
+static uint8_t* nextField;
+static uint8_t* pixels;
 
 static uint8_t rand8(void);
 static int countNeighbours(int x, int y);
 
 EXPORT(getWidth) int get_width(void) { return width; }
 EXPORT(getHeight) int get_height(void) { return height; }
-EXPORT(getPixels) uint8_t* get_pixels(void) { return pixels; }
 
-EXPORT(step) void step(void) 
-{
+EXPORT(step) void step(void) {
     for (int y = 0; y < height; y++) {
         for (int x = 0; x < width; x++) {
             int count = countNeighbours(x, y);
             uint8_t currentCell = field[x + y * width];
             int nextCell = currentCell;
-            if (currentCell && count < 2) nextCell = 0;
-            else if (currentCell && count > 3) nextCell = 0;
-            else if (!currentCell && count == 3) nextCell = 1;
+            if (currentCell && count < 2)
+                nextCell = 0;
+            else if (currentCell && count > 3)
+                nextCell = 0;
+            else if (!currentCell && count == 3)
+                nextCell = 1;
 
             nextField[x + y * width] = nextCell;
         }
@@ -47,12 +48,12 @@ EXPORT(step) void step(void)
     }
 }
 
-static int countNeighbours(int x, int y) 
-{
+static int countNeighbours(int x, int y) {
     int count = 0;
     for (int i = -1; i <= 1; i++) {
         for (int j = -1; j <= 1; j++) {
-            if (i == 0 && j == 0) continue;
+            if (i == 0 && j == 0)
+                continue;
 
             int xx = (x + i + width) % width;
             int yy = (y + j + height) % height;
@@ -71,10 +72,9 @@ static int countNeighbours(int x, int y)
 #define MULT_LO (MULT & 255)
 #define MULT_HI (MULT & 256)
 
-static uint8_t rand_state[STATE_BYTES] = { 0x87, 0xdd, 0xdc, 0x10, 0x35, 0xbc, 0x5c };
+static uint8_t rand_state[STATE_BYTES] = {0x87, 0xdd, 0xdc, 0x10, 0x35, 0xbc, 0x5c};
 
-static uint8_t rand8(void)
-{
+static uint8_t rand8(void) {
     static uint16_t c = 0x42;
     static uint32_t i = 0;
     uint16_t t;
@@ -93,11 +93,16 @@ static uint8_t rand8(void)
     return x;
 }
 
-EXPORT(initField) void init_field(uint32_t randomSeed)
-{
+EXPORT(initField) uint8_t* init_field(uint32_t randomSeed) {
     *((uint32_t*)&rand_state[STATE_BYTES - sizeof(uint32_t)]) = randomSeed; // Voodoo
 
+    field = malloc(width * height);
+    nextField = malloc(width * height);
+    pixels = malloc(width * height * 4);
+
     for (int i = 0; i < width * height; i++) {
         field[i] = rand8() & 1;
     }
+
+    return pixels;
 }