Add binary mural serialiser and deserialiser

src/UI/serializer.tsx

@@ -0,0 +1,127 @@
+import { Mural } from "../interfaces";
+import { waitForDraw } from "../lib/utils";
+
+const MAGIC_REPEATING = 200;
+const TRANSPARENT = 201;
+
+const VERSION = 1;
+
+export function compressRepeatingArray(index: number, buffer: number[] /* 0xFF */) {
+    const a = buffer[index];
+    const b = buffer[index + 1];
+    const c = buffer[index + 2];
+    const pixelIndex = a === -1 ? TRANSPARENT : a;
+    if (a === b && b === c) {
+        let i = 0;
+        for (; i < Math.min(buffer.length - index, 0xFF); i++) {
+            if (a !== buffer[index + i]) {
+               break;
+            }   
+        }
+        return [MAGIC_REPEATING, i - 1, pixelIndex];
+    }
+    return [pixelIndex];
+}
+
+export function decompressRepeatingArray(buffer: ArrayLike<number>) {
+    const output: number[] = [];
+    const addValue = (value: number) => {
+        output.push(value === TRANSPARENT ? -1 : value);
+    };
+    
+    for (let i = 0; i < buffer.length; i++) {
+        const item = buffer[i];
+        if (item === MAGIC_REPEATING) {
+            const length = buffer[++i];
+            const value = buffer[++i];
+            for (let j = 0; j < length; j++) {
+                addValue(value);
+            }
+        } else {
+            addValue(item);
+        }
+    }
+    return output;
+}
+
+export async function serializeMural(mural: Mural) {
+    const encoder = new TextEncoder();
+    const nameBinary = encoder.encode(mural.name);
+    await waitForDraw();
+    const array: number[] = [];
+    for (let i = 0; i < mural.pixels.length; i++) {
+        for (let j = 0; j < mural.pixels[i].length; j++) {
+            array.push(mural.pixels[i][j]);
+        }
+    }
+    const pixelEncodeBuffer: number[] = [];
+    for (let i = 0; i < array.length; i++) {
+        const rtn = compressRepeatingArray(i, array);
+        if (rtn.length === 1) {
+            pixelEncodeBuffer.push(rtn[0]);
+        } else {
+            pixelEncodeBuffer.push(rtn[0], rtn[1], rtn[2]);
+            i += rtn[1] - 1;
+        }
+    }
+
+    const pixelBuffer = new Uint8Array(pixelEncodeBuffer);
+    const firstHalf = 1 + 4 + 4 + 1 + 2 + nameBinary.byteLength;
+    const buffer = new ArrayBuffer(firstHalf + pixelBuffer.byteLength);
+    const view = new DataView(buffer);
+    view.setUint8(0, VERSION);
+    view.setInt32(1, mural.x, true);
+    view.setInt32(5, mural.y, true);
+    view.setUint16(9, mural.pixels[0].length, true);
+    view.setUint8(11, nameBinary.length);
+    new Uint8Array(buffer).set(nameBinary, 12);
+    new Uint8Array(buffer).set(pixelBuffer, firstHalf);
+ 
+    return buffer;
+}
+
+export async function deserializeMural(buffer: ArrayBuffer): Promise<Mural> {
+    const view = new DataView(buffer);
+    const version = view.getUint8(0);
+    if (version !== VERSION) {
+        throw new Error("Unknown version");
+    }
+    const x = view.getInt32(1, true);
+    const y = view.getInt32(5, true);
+    const width = view.getUint16(9, true);
+    const nameLength = view.getUint8(11);
+
+    const nameBytes = new Uint8Array(buffer, 12, nameLength);
+    const decoder = new TextDecoder();
+    const name = decoder.decode(nameBytes);
+    const pixelBuffer = new Uint8Array(buffer, 12 + nameLength);
+    await waitForDraw();
+    const pixelArray: number[] = decompressRepeatingArray(pixelBuffer);
+
+    const pixels: number[][] = [];
+
+    leg:
+    for (;;) {
+        await waitForDraw();
+        if (!pixelArray.length) {
+            break;
+        }
+        const ref: number[] = [];
+        pixels.push(ref);
+        for (let j = 0; j < width; j++) {
+            const item = pixelArray.shift();    
+            if (item != undefined) { 
+                ref.push(item);
+            } else {
+                break leg;
+            }
+        }
+    }
+
+    return {
+        name,
+        x,
+        y,
+        pixels
+    } as Mural;
+}