refactor: rewrite Blob implementation (#9309)

Co-authored-by: Kitson Kelly <me@kitsonkelly.com>

1 files changed, 294 insertions, 0 deletions

diff --git a/op_crates/fetch/21_blob.js b/op_crates/fetch/21_blob.js
new file mode 100644
index 000000000..552441b21
--- /dev/null
+++ b/op_crates/fetch/21_blob.js
@@ -0,0 +1,294 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+// @ts-check
+/// <reference no-default-lib="true" />
+/// <reference path="../../core/lib.deno_core.d.ts" />
+/// <reference path="../web/internal.d.ts" />
+/// <reference path="../web/lib.deno_web.d.ts" />
+/// <reference path="./internal.d.ts" />
+/// <reference path="./lib.deno_fetch.d.ts" />
+/// <reference lib="esnext" />
+
+((window) => {
+  // TODO(lucacasonato): this needs to not be hardcoded and instead depend on
+  // host os.
+  const isWindows = false;
+
+  /**
+   * @param {string} input
+   * @param {number} position
+   * @returns {{result: string, position: number}}
+   */
+  function collectCodepointsNotCRLF(input, position) {
+    // See https://w3c.github.io/FileAPI/#convert-line-endings-to-native and
+    // https://infra.spec.whatwg.org/#collect-a-sequence-of-code-points
+    const start = position;
+    for (
+      let c = input.charAt(position);
+      position < input.length && !(c === "\r" || c === "\n");
+      c = input.charAt(++position)
+    );
+    return { result: input.slice(start, position), position };
+  }
+
+  /**
+   * @param {string} s
+   * @returns {string}
+   */
+  function convertLineEndingsToNative(s) {
+    const nativeLineEnding = isWindows ? "\r\n" : "\n";
+
+    let { result, position } = collectCodepointsNotCRLF(s, 0);
+
+    while (position < s.length) {
+      const codePoint = s.charAt(position);
+      if (codePoint === "\r") {
+        result += nativeLineEnding;
+        position++;
+        if (position < s.length && s.charAt(position) === "\n") {
+          position++;
+        }
+      } else if (codePoint === "\n") {
+        position++;
+        result += nativeLineEnding;
+      }
+      const { result: token, position: newPosition } = collectCodepointsNotCRLF(
+        s,
+        position,
+      );
+      position = newPosition;
+      result += token;
+    }
+
+    return result;
+  }
+
+  /**
+   * @param  {...Uint8Array} bytesArrays
+   * @returns {Uint8Array} 
+   */
+  function concatUint8Arrays(...bytesArrays) {
+    let byteLength = 0;
+    for (const bytes of bytesArrays) {
+      byteLength += bytes.byteLength;
+    }
+    const finalBytes = new Uint8Array(byteLength);
+    let current = 0;
+    for (const bytes of bytesArrays) {
+      finalBytes.set(bytes, current);
+      current += bytes.byteLength;
+    }
+    return finalBytes;
+  }
+
+  const utf8Encoder = new TextEncoder();
+  const utf8Decoder = new TextDecoder();
+
+  /** @typedef {BufferSource | Blob | string} BlobPart */
+
+  /** 
+     * @param {BlobPart[]} parts
+     * @param {string} endings
+     * @returns {Uint8Array}
+     */
+  function processBlobParts(parts, endings) {
+    /** @type {Uint8Array[]} */
+    const bytesArrays = [];
+    for (const element of parts) {
+      if (element instanceof ArrayBuffer) {
+        bytesArrays.push(new Uint8Array(element.slice(0)));
+      } else if (ArrayBuffer.isView(element)) {
+        const buffer = element.buffer.slice(
+          element.byteOffset,
+          element.byteOffset + element.byteLength,
+        );
+        bytesArrays.push(new Uint8Array(buffer));
+      } else if (element instanceof Blob) {
+        bytesArrays.push(
+          new Uint8Array(element[_byteSequence].buffer.slice(0)),
+        );
+      } else if (typeof element === "string") {
+        let s = element;
+        if (endings == "native") {
+          s = convertLineEndingsToNative(s);
+        }
+        bytesArrays.push(utf8Encoder.encode(s));
+      } else {
+        throw new TypeError("Unreachable code (invalild element type)");
+      }
+    }
+    return concatUint8Arrays(...bytesArrays);
+  }
+
+  /**
+   * @param {string} str 
+   * @returns {string}
+   */
+  function normalizeType(str) {
+    let normalizedType = str;
+    if (!/^[\x20-\x7E]*$/.test(str)) {
+      normalizedType = "";
+    }
+    return normalizedType.toLowerCase();
+  }
+
+  const _byteSequence = Symbol("[[ByteSequence]]");
+
+  class Blob {
+    /** @type {string} */
+    #type;
+
+    /** @type {Uint8Array} */
+    [_byteSequence];
+
+    /** 
+     * @param {BlobPart[]} [blobParts]
+     * @param {BlobPropertyBag} [options]
+     */
+    constructor(blobParts, options) {
+      if (blobParts === undefined) {
+        blobParts = [];
+      }
+      if (typeof blobParts !== "object") {
+        throw new TypeError(
+          `Failed to construct 'Blob'. blobParts cannot be converted to a sequence.`,
+        );
+      }
+
+      const parts = [];
+      const iterator = blobParts[Symbol.iterator]?.();
+      if (iterator === undefined) {
+        throw new TypeError(
+          "Failed to construct 'Blob'. The provided value cannot be converted to a sequence",
+        );
+      }
+      while (true) {
+        const { value: element, done } = iterator.next();
+        if (done) break;
+        if (
+          ArrayBuffer.isView(element) || element instanceof ArrayBuffer ||
+          element instanceof Blob
+        ) {
+          parts.push(element);
+        } else {
+          parts.push(String(element));
+        }
+      }
+
+      if (!options || typeof options === "function") {
+        options = {};
+      }
+      if (typeof options !== "object") {
+        throw new TypeError(
+          `Failed to construct 'Blob'. options is not an object.`,
+        );
+      }
+      const endings = options.endings?.toString() ?? "transparent";
+      const type = options.type?.toString() ?? "";
+
+      /** @type {Uint8Array} */
+      this[_byteSequence] = processBlobParts(parts, endings);
+      this.#type = normalizeType(type);
+    }
+
+    /** @returns {number} */
+    get size() {
+      return this[_byteSequence].byteLength;
+    }
+
+    /** @returns {string} */
+    get type() {
+      return this.#type;
+    }
+
+    /** 
+     * @param {number} [start]
+     * @param {number} [end]
+     * @param {string} [contentType]
+     * @returns {Blob}
+     */
+    slice(start, end, contentType) {
+      const O = this;
+      /** @type {number} */
+      let relativeStart;
+      if (start === undefined) {
+        relativeStart = 0;
+      } else {
+        start = Number(start);
+        if (start < 0) {
+          relativeStart = Math.max(O.size + start, 0);
+        } else {
+          relativeStart = Math.min(start, O.size);
+        }
+      }
+      /** @type {number} */
+      let relativeEnd;
+      if (end === undefined) {
+        relativeEnd = O.size;
+      } else {
+        end = Number(end);
+        if (end < 0) {
+          relativeEnd = Math.max(O.size + end, 0);
+        } else {
+          relativeEnd = Math.min(end, O.size);
+        }
+      }
+      /** @type {string} */
+      let relativeContentType;
+      if (contentType === undefined) {
+        relativeContentType = "";
+      } else {
+        relativeContentType = normalizeType(String(contentType));
+      }
+      return new Blob([
+        O[_byteSequence].buffer.slice(relativeStart, relativeEnd),
+      ], { type: relativeContentType });
+    }
+
+    /**
+     * @returns {ReadableStream<Uint8Array>}
+     */
+    stream() {
+      const bytes = this[_byteSequence];
+      const stream = new ReadableStream({
+        type: "bytes",
+        /** @param {ReadableByteStreamController} controller */
+        start(controller) {
+          const chunk = new Uint8Array(bytes.buffer.slice(0));
+          if (chunk.byteLength > 0) controller.enqueue(chunk);
+          controller.close();
+        },
+      });
+      return stream;
+    }
+
+    /**
+     * @returns {Promise<string>}
+     */
+    async text() {
+      const buffer = await this.arrayBuffer();
+      return utf8Decoder.decode(buffer);
+    }
+
+    /**
+     * @returns {Promise<ArrayBuffer>}
+     */
+    async arrayBuffer() {
+      const stream = this.stream();
+      let bytes = new Uint8Array();
+      for await (const chunk of stream) {
+        bytes = concatUint8Arrays(bytes, chunk);
+      }
+      return bytes.buffer;
+    }
+
+    get [Symbol.toStringTag]() {
+      return "Blob";
+    }
+  }
+
+  window.__bootstrap.blob = {
+    Blob,
+    _byteSequence,
+  };
+})(this);