fix: don't try to grow the buffer more than allowed by the system

Closes: image-js/fast-png#42

src/IOBuffer.ts

@@ -1,4 +1,4 @@
-import { isHostBigEndian } from './env';
+import { increaseBufferSize, isHostBigEndian } from './env';
 import { decode, encode } from './text';
 
 const defaultByteLength = 1024 * 8;
@@ -246,13 +246,11 @@ export class IOBuffer {
   public ensureAvailable(byteLength = 1): this {
     if (!this.available(byteLength)) {
       const lengthNeeded = this.offset + byteLength;
-      const newLength = lengthNeeded * 2;
-      const newArray = new Uint8Array(newLength);
-      newArray.set(new Uint8Array(this.buffer));
-      this.buffer = newArray.buffer;
-      this.length = newLength;
-      this.byteLength = newLength;
-      this._data = new DataView(this.buffer);
+      const newBuffer = increaseBufferSize(this.buffer, lengthNeeded);
+      this.buffer = newBuffer;
+      this.length = newBuffer.byteLength;
+      this.byteLength = newBuffer.byteLength;
+      this._data = new DataView(newBuffer);
     }
     return this;
   }

src/__tests__/write.test.ts

@@ -122,6 +122,9 @@ describe('write data', () => {
     theBuffer.seek(20);
     theBuffer.ensureAvailable(30);
     expect(theBuffer.byteLength).toBeGreaterThanOrEqual(50);
+    expect(() => theBuffer.ensureAvailable(Number.MAX_SAFE_INTEGER)).toThrow(
+      RangeError,
+    );
   });
 
   it('writeUtf8', () => {

src/env.ts

@@ -13,3 +13,61 @@ function detectEndianness() {
   const view = new Uint32Array(array.buffer);
   return !((view[0] = 1) & array[0]);
 }
+
+/**
+ * Returns a new buffer with the same contents as the input buffer, but with a larger size.
+ * Try to at least double the size of the buffer to avoid frequent reallocations.
+ * @param buffer - The buffer to increase the size of.
+ * @param minimumSize - The minimum size of the new buffer.
+ * @returns The new buffer.
+ */
+export function increaseBufferSize(
+  buffer: ArrayBuffer,
+  minimumSize: number,
+): ArrayBuffer {
+  let maxAllowedLength = 2 ** 29; // 512MB
+  if (minimumSize > maxAllowedLength) {
+    // The check is expensive, don't do it until a large buffer is requested.
+    maxAllowedLength = getMaxUint8ArrayLength();
+    if (minimumSize > maxAllowedLength) {
+      throw new RangeError(
+        `Cannot create a buffer with more than ${maxAllowedLength} bytes`,
+      );
+    }
+  }
+  // Don't try to allocate more than the maximum allowed length.
+  const doubleOrMax = Math.min(buffer.byteLength * 2, maxAllowedLength);
+  const newLength = Math.max(doubleOrMax, minimumSize);
+  const newBuffer = new ArrayBuffer(newLength);
+  new Uint8Array(newBuffer).set(new Uint8Array(buffer));
+  return newBuffer;
+}
+
+let maxUint8ArrayLength: number | undefined;
+
+/**
+ * Detects and returns the maximum length that of an `ArrayBuffer`.
+ * @returns The maximum length that an `ArrayBuffer` can have.
+ */
+export function getMaxUint8ArrayLength() {
+  return (
+    maxUint8ArrayLength ?? (maxUint8ArrayLength = detectMaxUint8ArrayLength())
+  );
+}
+
+function detectMaxUint8ArrayLength() {
+  // Use a binary search to find the maximum length of an Uint8Array.
+  let low = 1;
+  let high = Number.MAX_SAFE_INTEGER - 1;
+  while (low < high) {
+    const mid = Math.trunc((low + high) / 2);
+    try {
+      // eslint-disable-next-line no-new
+      new Uint8Array(mid);
+      low = mid + 1;
+    } catch {
+      high = mid;
+    }
+  }
+  return low - 1;
+}

src/text.ts

@@ -1,10 +1,21 @@
+/**
+ * Decode a Uint8Array to a string.
+ * @param bytes - The Uint8Array to decode.
+ * @param encoding - The encoding to use. Defaults to 'utf8'.
+ * @returns The decoded string.
+ */
 export function decode(bytes: Uint8Array, encoding = 'utf8'): string {
   const decoder = new TextDecoder(encoding);
   return decoder.decode(bytes);
 }
 
 const encoder = new TextEncoder();
 
+/**
+ * Encode a string as UTF-8 to a Uint8Array.
+ * @param str - The string to encode.
+ * @returns The encoded Uint8Array.
+ */
 export function encode(str: string): Uint8Array {
   return encoder.encode(str);
 }

tsconfig.json

@@ -5,6 +5,7 @@
     "sourceMap": true,
     "strict": true,
     "target": "es2022",
+    "lib": ["es2022"],
     "skipLibCheck": true,
     "allowJs": false,
     "noEmit": true