[Implement] Naive Buffer.from, and friends

assembly/buffer/index.ts

@@ -1,10 +1,20 @@
 import { BLOCK_MAXSIZE, BLOCK, BLOCK_OVERHEAD } from "rt/common";
 import { E_INVALIDLENGTH, E_INDEXOUTOFRANGE } from "util/error";
 import { Uint8Array } from "typedarray";
+import { ArrayBufferView } from "arraybuffer";
+import { Array } from "array";
+
+// @ts-ignore: Decorator
+@inline
+function assembleBuffer(arrayBuffer: usize, offset: usize, length: u32): Buffer {
+  let pointer = __alloc(offsetof<Buffer>(), idof<Buffer>());
+  store<usize>(pointer, __retain(arrayBuffer), offsetof<Buffer>("buffer"));
+  store<usize>(pointer, arrayBuffer + offset, offsetof<Buffer>("dataStart"));
+  store<u32>(pointer, length, offsetof<Buffer>("byteLength"));
+  return changetype<Buffer>(pointer);
+}
 
 export class Buffer extends Uint8Array {
-  [key: number]: u8;
-
   constructor(size: i32) {
     super(size);
   }
@@ -16,19 +26,89 @@ export class Buffer extends Uint8Array {
   @unsafe static allocUnsafe(size: i32): Buffer {
     // range must be valid
     if (<usize>size > BLOCK_MAXSIZE) throw new RangeError(E_INVALIDLENGTH);
-    let buffer = __alloc(size, idof<ArrayBuffer>());
-    let result = __alloc(offsetof<Buffer>(), idof<Buffer>());
+    return assembleBuffer(__alloc(size, idof<ArrayBuffer>()), 0, size);
+  }
+
+  public static fromArrayBuffer(buffer: ArrayBuffer, byteOffset: i32 = 0, length: i32 = -1): Buffer {
+    length = select(buffer.byteLength, length, length < 0);
+    if (i32(byteOffset < 0) | i32(byteOffset > buffer.byteLength - length)) throw new RangeError(E_INDEXOUTOFRANGE);
+    if (length == 0) return new Buffer(0);
+
+    return assembleBuffer(changetype<usize>(buffer), <usize>byteOffset, <u32>length);
+  }
+
+  public static fromString(value: string, encoding: string = "utf8"): Buffer {
+    let buffer: ArrayBuffer;
+    if (encoding == "utf8" || encoding == "utf-8") {
+      buffer = String.UTF8.encode(value);
+    } else if (encoding == "utf16le") {
+      buffer = String.UTF16.encode(value);
+    } else if (encoding == "hex") {
+      buffer = Buffer.HEX.encode(value);
+    } else if (encoding == "ascii") {
+      buffer = Buffer.ASCII.encode(value);
+    } else {
+      throw new TypeError("Invalid string encoding.");
+    }
+
+    // assemble the buffer
+    return assembleBuffer(changetype<usize>(buffer), 0, buffer.byteLength);
+  }
+
+  public static fromArray<T extends ArrayBufferView>(value: T, offset: i32 = 0, length: i32 = -1): Buffer {
+    length = select(value.length, length, length < 0);
+    if (i32(offset < 0) | i32(offset > value.length)) throw new RangeError(E_INDEXOUTOFRANGE);
+    if (length > value.length - offset) throw new RangeError(E_INVALIDLENGTH);
+    if (length == 0) return new Buffer(0);
+    let arrayBuffer = __alloc(length, idof<ArrayBuffer>());
+    if (value instanceof Array<string>) {
+      for (let i = 0; i < length; i++) {
+        let index = i + offset;
+        let byteValue = parseFloat(unchecked(value[index]));
+        store<u8>(arrayBuffer + <usize>i, <u8>(isFinite(byteValue) ? <u8>byteValue : 0));
+      }
+    } else {
+      for (let i = 0; i < length; i++) {
+        let index = i + offset;
+        let element = isDefined(unchecked(value[index]))
+          ? unchecked(value[index])
+          : value[index];
+
+        if (isFloat(element)) {
+          store<u8>(arrayBuffer + <usize>i, <u8>(isFinite(element) ? <u8>element : 0));
+        } else {
+          store<u8>(arrayBuffer + <usize>i, <u8>element);
+        }
+      }
+    }
+
+    return assembleBuffer(arrayBuffer, 0, length);
+  }
 
-    // set the properties
-    store<usize>(result, __retain(buffer), offsetof<Buffer>("buffer"));
-    store<usize>(result, buffer, offsetof<Buffer>("dataStart"));
-    store<i32>(result, size, offsetof<Buffer>("byteLength"));
+  public static fromBuffer(source: Buffer): Buffer {
+    let length = source.byteLength;
+    let data = __alloc(length, idof<ArrayBuffer>()); // retains
+    memory.copy(data, source.dataStart, length);
+    return assembleBuffer(data, 0, length);
+  }
 
-    // return and retain
-    return changetype<Buffer>(result);
+  // @ts-ignore: Buffer returns on all valid branches
+  public static from<T>(value: T): Buffer {
+    if (value instanceof ArrayBuffer) {
+      return assembleBuffer(changetype<usize>(value), 0, value.byteLength);
+    } else if (value instanceof String) {
+      // @ts-ignore value not instance of `string` does changetype<string>(value) work here?
+      let buffer = String.UTF8.encode(value);
+      return assembleBuffer(changetype<usize>(buffer), 0, buffer.byteLength);
+    } else if (value instanceof Buffer) {
+      return Buffer.fromBuffer(value);
+    } else if (value instanceof ArrayBufferView) {
+      return Buffer.fromArray(value);
+    }
+    ERROR("Cannot call Buffer.from<T>() where T is not a string, Buffer, ArrayBuffer, Array, or Array-like Object.");
   }
 
-  static isBuffer<T>(value: T): bool {
+  public static isBuffer<T>(value: T): bool {
     return value instanceof Buffer;
   }
 
@@ -39,13 +119,7 @@ export class Buffer extends Uint8Array {
     end   = end   < 0 ? max(len + end,   0) : min(end,   len);
     end   = max(end, begin);
 
-    var out = __alloc(offsetof<Buffer>(), idof<Buffer>()); // retains
-    store<usize>(out, __retain(changetype<usize>(this.buffer)), offsetof<Buffer>("buffer"));
-    store<usize>(out, this.dataStart + <usize>begin, offsetof<Buffer>("dataStart"));
-    store<i32>(out, end - begin, offsetof<Buffer>("byteLength"));
-
-    // retains
-    return changetype<Buffer>(out);
+    return assembleBuffer(changetype<usize>(this.buffer), <usize>this.byteOffset + <usize>begin, <u32>end - <u32>begin);
   }
 
   readInt8(offset: i32 = 0): i8 {

assembly/node.d.ts

@@ -3,6 +3,16 @@ declare class Buffer extends Uint8Array {
   static alloc(size: i32): Buffer;
   /** This method allocates a new Buffer of indicated size. This is unsafe because the data is not zeroed. */
   static allocUnsafe(size: i32): Buffer;
+  /** This method creates a Buffer from the given reference. This method is naive and defaults to utf8 encoding for strings. */
+  static from<T>(value: T): Buffer;
+  /** This method creates a buffer from a given string. This method defaults to utf8 encoding. */
+  public static fromString(value: string, encoding?: string): Buffer;
+  /** This method creates a buffer that uses the given ArrayBuffer as an underlying value. */
+  public static fromArrayBuffer(buffer: ArrayBuffer, byteOffset?: i32 , length?: i32): Buffer;
+  /** This method creates a copy of the buffer using memory.copy(). */
+  public static fromBuffer(source: Buffer): Buffer;
+  /** This method creates a new Buffer by copying the underlying values to a new ArrayBuffer and coercing each one to an 8 bit integer value. */
+  public static fromArray<T extends ArrayBufferView<number | string>>(value: T, offset?: i32, length?: i32): Buffer;
   /** This method asserts a value is a Buffer object via `value instanceof Buffer`. */
   static isBuffer<T>(value: T): bool;
   /** Reads a signed integer at the designated offset. */

tests/buffer.spec.ts

@@ -36,7 +36,7 @@ describe("buffer", () => {
     expect(Buffer.alloc(10)).toBeTruthy();
     expect(Buffer.alloc(10)).toHaveLength(10);
     let buff = Buffer.alloc(100);
-    for (let i = 0; i < buff.length; i++) expect<u8>(buff[i]).toBe(0);
+    for (let i = 0; i < buff.length; i++) expect(buff[i]).toBe(0);
     expect(buff.buffer).not.toBeNull();
     expect(buff.byteLength).toBe(100);
     expect(() => { Buffer.alloc(-1); }).toThrow();
@@ -55,6 +55,108 @@ describe("buffer", () => {
     // expect(() => { Buffer.allocUnsafe(BLOCK_MAXSIZE + 1); }).toThrow();
   });
 
+  /**
+   * This specification is a tradeoff, because Buffer.from() takes _many_ parameters.
+   * Instead, the only common parameter is the first one, which results in Buffer.from
+   * acting in a very naive fashion. Perhaps an optional encoding parameter might be
+   * possible for strings, at least. However, this makes things more complicated.
+   * There are no good solutions. Only tradeoffs. Function overloading is the only
+   * way to fix this problem.
+   */
+  test(".from", () => {
+    // Buffer.from uses the array buffer reference
+    let buff = new ArrayBuffer(100);
+    for (let i = 0; i < 100; i++) store<u8>(changetype<usize>(buff), u8(i));
+    let abBuffer = Buffer.from(buff);
+    expect(abBuffer.buffer).toStrictEqual(buff);
+    expect(abBuffer.buffer).toBe(buff);
+
+    // strings are utf8 encoded by default
+    let strBuffer = Buffer.from("Hello world!");
+    let strBufferExpected = create<Buffer>([0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x77, 0x6f, 0x72, 0x6c, 0x64, 0x21]);
+    expect(strBuffer).toStrictEqual(strBufferExpected);
+
+    // buffer returns a new reference view to a new ArrayBuffer
+    let buff2 = Buffer.from(abBuffer);
+    expect(buff2).not.toBe(abBuffer);
+    expect(buff2).toStrictEqual(abBuffer);
+    expect(buff2.buffer).not.toBe(abBuffer.buffer);
+
+    // else if it extends ArrayBufferView simply converts all the values
+    let floats = create<Float32Array>([1.1, 2.2, 3.3]);
+    let floatBuff = Buffer.from(floats);
+    let floatBuffExpected = create<Buffer>([1, 2, 3]);
+    expect(floatBuff).toStrictEqual(floatBuffExpected, "float values");
+
+    let strArrayExpected = create<Buffer>([1, 2, 3, 4, 5, 6, 7, 0, 0, 0]);
+    let stringValues = ["1.1", "2.2", "3.3", "4.4", "5.5", "6.6", "7.7", "Infinity", "NaN", "-Infinity"];
+    let strArrayActual = Buffer.from(stringValues);
+    expect(strArrayActual).toStrictEqual(strArrayExpected, "Array Of Strings");
+  });
+
+  test(".fromString", () => {
+    // public static fromString(value: string, encoding: string = "utf8"): Buffer {
+    // default encoding is utf8
+    let expected = create<Buffer>([0x74, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x61, 0x20, 0x74, 0xc3, 0xa9, 0x73, 0x74])
+    expect(Buffer.from('this is a tést'))
+      .toStrictEqual(expected);
+
+    expect(Buffer.fromString('7468697320697320612074c3a97374', 'hex'))
+      .toStrictEqual(expected);
+  });
+
+  test(".fromArrayBuffer", () => {
+    const arr = new Uint16Array(2);
+
+    arr[0] = 5000;
+    arr[1] = 4000;
+
+    // Shares memory with `arr`.
+    const buf = Buffer.fromArrayBuffer(arr.buffer);
+
+    expect(buf).toStrictEqual(create<Buffer>([0x88, 0x13, 0xa0, 0x0f]));
+
+    // Changing the original Uint16Array changes the Buffer also.
+    arr[1] = 6000;
+    expect(buf).toStrictEqual(create<Buffer>([0x88, 0x13, 0x70, 0x17]));
+
+    // test optional parameters
+    expect(Buffer.fromArrayBuffer(arr.buffer, 1, 2)).toStrictEqual(create<Buffer>([0x13, 0x70]));
+
+    // TODO:
+    // expectFn(() => {
+    //   let value = create<Uint16Array>([5000, 4000]); // 4 bytes
+    //   Buffer.fromArrayBuffer(value.buffer, 5);
+    // }).toThrow("offset out of bounds should throw");
+    // expectFn(() => {
+    //   let value = create<Uint16Array>([5000, 4000]); // 4 bytes
+    //   Buffer.fromArrayBuffer(value.buffer, 2, 3);
+    // }).toThrow("length out of bounds should throw");
+  });
+
+  test(".fromBuffer", () => {
+    let buff1 = create<Buffer>([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+    let buff2 = Buffer.fromBuffer(buff1);
+
+    expect(buff1).not.toBe(buff2);
+    expect(buff1.buffer).not.toBe(buff2.buffer);
+    expect(buff1).toStrictEqual(buff2);
+  });
+
+  test(".fromArray", () => {
+    let buff1 = create<Uint16Array>([3, 6, 9, 12, 15, 18, 21]);
+    let buff2 = Buffer.fromArray(buff1, 2, 4);
+    let expected = create<Buffer>([9, 12, 15, 18]);
+    expect(buff2).toStrictEqual(expected);
+
+    // test string values
+    buff2 = Buffer.fromArray(["9.2", "12.1", "15.3", "18.8"]);
+    expect(buff2).toStrictEqual(expected);
+  });
+
+  // todo: fromArray
+  // todo: fromBuffer
+
   test("#isBuffer", () => {
     let a = "";
     let b = new Uint8Array(0);
@@ -252,7 +354,7 @@ describe("buffer", () => {
     expect(buff.writeInt32LE(-559038737)).toBe(4);
     expect(buff.writeInt32LE(283033613,4)).toBe(8);
     let result = create<Buffer>([0xEF,0xBE,0xAD,0xDE,0x0d,0xc0,0xde,0x10]);
-    expect<Buffer>(buff).toStrictEqual(result);
+    expect(buff).toStrictEqual(result);
     expect(() => {
       let newBuff = new Buffer(1);
       newBuff.writeInt32LE(0);