lib/core/chunked_stream.js

/**
 * @licstart The following is the entire license notice for the
 * Javascript code in this page
 *
 * Copyright 2020 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @licend The above is the entire license notice for the
 * Javascript code in this page
 */
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.ChunkedStreamManager = exports.ChunkedStream = void 0;

var _util = require("../shared/util.js");

var _core_utils = require("./core_utils.js");

class ChunkedStream {
  constructor(length, chunkSize, manager) {
    this.bytes = new Uint8Array(length);
    this.start = 0;
    this.pos = 0;
    this.end = length;
    this.chunkSize = chunkSize;
    this._loadedChunks = new Set();
    this.numChunks = Math.ceil(length / chunkSize);
    this.manager = manager;
    this.progressiveDataLength = 0;
    this.lastSuccessfulEnsureByteChunk = -1;
  }

  getMissingChunks() {
    const chunks = [];

    for (let chunk = 0, n = this.numChunks; chunk < n; ++chunk) {
      if (!this._loadedChunks.has(chunk)) {
        chunks.push(chunk);
      }
    }

    return chunks;
  }

  getBaseStreams() {
    return [this];
  }

  get numChunksLoaded() {
    return this._loadedChunks.size;
  }

  allChunksLoaded() {
    return this.numChunksLoaded === this.numChunks;
  }

  onReceiveData(begin, chunk) {
    const chunkSize = this.chunkSize;

    if (begin % chunkSize !== 0) {
      throw new Error(`Bad begin offset: ${begin}`);
    }

    const end = begin + chunk.byteLength;

    if (end % chunkSize !== 0 && end !== this.bytes.length) {
      throw new Error(`Bad end offset: ${end}`);
    }

    this.bytes.set(new Uint8Array(chunk), begin);
    const beginChunk = Math.floor(begin / chunkSize);
    const endChunk = Math.floor((end - 1) / chunkSize) + 1;

    for (let curChunk = beginChunk; curChunk < endChunk; ++curChunk) {
      this._loadedChunks.add(curChunk);
    }
  }

  onReceiveProgressiveData(data) {
    let position = this.progressiveDataLength;
    const beginChunk = Math.floor(position / this.chunkSize);
    this.bytes.set(new Uint8Array(data), position);
    position += data.byteLength;
    this.progressiveDataLength = position;
    const endChunk = position >= this.end ? this.numChunks : Math.floor(position / this.chunkSize);

    for (let curChunk = beginChunk; curChunk < endChunk; ++curChunk) {
      this._loadedChunks.add(curChunk);
    }
  }

  ensureByte(pos) {
    if (pos < this.progressiveDataLength) {
      return;
    }

    const chunk = Math.floor(pos / this.chunkSize);

    if (chunk === this.lastSuccessfulEnsureByteChunk) {
      return;
    }

    if (!this._loadedChunks.has(chunk)) {
      throw new _core_utils.MissingDataException(pos, pos + 1);
    }

    this.lastSuccessfulEnsureByteChunk = chunk;
  }

  ensureRange(begin, end) {
    if (begin >= end) {
      return;
    }

    if (end <= this.progressiveDataLength) {
      return;
    }

    const chunkSize = this.chunkSize;
    const beginChunk = Math.floor(begin / chunkSize);
    const endChunk = Math.floor((end - 1) / chunkSize) + 1;

    for (let chunk = beginChunk; chunk < endChunk; ++chunk) {
      if (!this._loadedChunks.has(chunk)) {
        throw new _core_utils.MissingDataException(begin, end);
      }
    }
  }

  nextEmptyChunk(beginChunk) {
    const numChunks = this.numChunks;

    for (let i = 0; i < numChunks; ++i) {
      const chunk = (beginChunk + i) % numChunks;

      if (!this._loadedChunks.has(chunk)) {
        return chunk;
      }
    }

    return null;
  }

  hasChunk(chunk) {
    return this._loadedChunks.has(chunk);
  }

  get length() {
    return this.end - this.start;
  }

  get isEmpty() {
    return this.length === 0;
  }

  getByte() {
    const pos = this.pos;

    if (pos >= this.end) {
      return -1;
    }

    if (pos >= this.progressiveDataLength) {
      this.ensureByte(pos);
    }

    return this.bytes[this.pos++];
  }

  getUint16() {
    const b0 = this.getByte();
    const b1 = this.getByte();

    if (b0 === -1 || b1 === -1) {
      return -1;
    }

    return (b0 << 8) + b1;
  }

  getInt32() {
    const b0 = this.getByte();
    const b1 = this.getByte();
    const b2 = this.getByte();
    const b3 = this.getByte();
    return (b0 << 24) + (b1 << 16) + (b2 << 8) + b3;
  }

  getBytes(length, forceClamped = false) {
    const bytes = this.bytes;
    const pos = this.pos;
    const strEnd = this.end;

    if (!length) {
      if (strEnd > this.progressiveDataLength) {
        this.ensureRange(pos, strEnd);
      }

      const subarray = bytes.subarray(pos, strEnd);
      return forceClamped ? new Uint8ClampedArray(subarray) : subarray;
    }

    let end = pos + length;

    if (end > strEnd) {
      end = strEnd;
    }

    if (end > this.progressiveDataLength) {
      this.ensureRange(pos, end);
    }

    this.pos = end;
    const subarray = bytes.subarray(pos, end);
    return forceClamped ? new Uint8ClampedArray(subarray) : subarray;
  }

  peekByte() {
    const peekedByte = this.getByte();

    if (peekedByte !== -1) {
      this.pos--;
    }

    return peekedByte;
  }

  peekBytes(length, forceClamped = false) {
    const bytes = this.getBytes(length, forceClamped);
    this.pos -= bytes.length;
    return bytes;
  }

  getByteRange(begin, end) {
    if (begin < 0) {
      begin = 0;
    }

    if (end > this.end) {
      end = this.end;
    }

    if (end > this.progressiveDataLength) {
      this.ensureRange(begin, end);
    }

    return this.bytes.subarray(begin, end);
  }

  skip(n) {
    if (!n) {
      n = 1;
    }

    this.pos += n;
  }

  reset() {
    this.pos = this.start;
  }

  moveStart() {
    this.start = this.pos;
  }

  makeSubStream(start, length, dict) {
    if (length) {
      if (start + length > this.progressiveDataLength) {
        this.ensureRange(start, start + length);
      }
    } else {
      if (start >= this.progressiveDataLength) {
        this.ensureByte(start);
      }
    }

    function ChunkedStreamSubstream() {}

    ChunkedStreamSubstream.prototype = Object.create(this);

    ChunkedStreamSubstream.prototype.getMissingChunks = function () {
      const chunkSize = this.chunkSize;
      const beginChunk = Math.floor(this.start / chunkSize);
      const endChunk = Math.floor((this.end - 1) / chunkSize) + 1;
      const missingChunks = [];

      for (let chunk = beginChunk; chunk < endChunk; ++chunk) {
        if (!this._loadedChunks.has(chunk)) {
          missingChunks.push(chunk);
        }
      }

      return missingChunks;
    };

    ChunkedStreamSubstream.prototype.allChunksLoaded = function () {
      if (this.numChunksLoaded === this.numChunks) {
        return true;
      }

      return this.getMissingChunks().length === 0;
    };

    const subStream = new ChunkedStreamSubstream();
    subStream.pos = subStream.start = start;
    subStream.end = start + length || this.end;
    subStream.dict = dict;
    return subStream;
  }

}

exports.ChunkedStream = ChunkedStream;

class ChunkedStreamManager {
  constructor(pdfNetworkStream, args) {
    this.length = args.length;
    this.chunkSize = args.rangeChunkSize;
    this.stream = new ChunkedStream(this.length, this.chunkSize, this);
    this.pdfNetworkStream = pdfNetworkStream;
    this.disableAutoFetch = args.disableAutoFetch;
    this.msgHandler = args.msgHandler;
    this.currRequestId = 0;
    this._chunksNeededByRequest = new Map();
    this._requestsByChunk = new Map();
    this._promisesByRequest = new Map();
    this.progressiveDataLength = 0;
    this.aborted = false;
    this._loadedStreamCapability = (0, _util.createPromiseCapability)();
  }

  onLoadedStream() {
    return this._loadedStreamCapability.promise;
  }

  sendRequest(begin, end) {
    const rangeReader = this.pdfNetworkStream.getRangeReader(begin, end);

    if (!rangeReader.isStreamingSupported) {
      rangeReader.onProgress = this.onProgress.bind(this);
    }

    let chunks = [],
        loaded = 0;
    const promise = new Promise((resolve, reject) => {
      const readChunk = chunk => {
        try {
          if (!chunk.done) {
            const data = chunk.value;
            chunks.push(data);
            loaded += (0, _util.arrayByteLength)(data);

            if (rangeReader.isStreamingSupported) {
              this.onProgress({
                loaded
              });
            }

            rangeReader.read().then(readChunk, reject);
            return;
          }

          const chunkData = (0, _util.arraysToBytes)(chunks);
          chunks = null;
          resolve(chunkData);
        } catch (e) {
          reject(e);
        }
      };

      rangeReader.read().then(readChunk, reject);
    });
    promise.then(data => {
      if (this.aborted) {
        return;
      }

      this.onReceiveData({
        chunk: data,
        begin
      });
    });
  }

  requestAllChunks() {
    const missingChunks = this.stream.getMissingChunks();

    this._requestChunks(missingChunks);

    return this._loadedStreamCapability.promise;
  }

  _requestChunks(chunks) {
    const requestId = this.currRequestId++;
    const chunksNeeded = new Set();

    this._chunksNeededByRequest.set(requestId, chunksNeeded);

    for (const chunk of chunks) {
      if (!this.stream.hasChunk(chunk)) {
        chunksNeeded.add(chunk);
      }
    }

    if (chunksNeeded.size === 0) {
      return Promise.resolve();
    }

    const capability = (0, _util.createPromiseCapability)();

    this._promisesByRequest.set(requestId, capability);

    const chunksToRequest = [];

    for (const chunk of chunksNeeded) {
      let requestIds = this._requestsByChunk.get(chunk);

      if (!requestIds) {
        requestIds = [];

        this._requestsByChunk.set(chunk, requestIds);

        chunksToRequest.push(chunk);
      }

      requestIds.push(requestId);
    }

    if (chunksToRequest.length > 0) {
      const groupedChunksToRequest = this.groupChunks(chunksToRequest);

      for (const groupedChunk of groupedChunksToRequest) {
        const begin = groupedChunk.beginChunk * this.chunkSize;
        const end = Math.min(groupedChunk.endChunk * this.chunkSize, this.length);
        this.sendRequest(begin, end);
      }
    }

    return capability.promise.catch(reason => {
      if (this.aborted) {
        return;
      }

      throw reason;
    });
  }

  getStream() {
    return this.stream;
  }

  requestRange(begin, end) {
    end = Math.min(end, this.length);
    const beginChunk = this.getBeginChunk(begin);
    const endChunk = this.getEndChunk(end);
    const chunks = [];

    for (let chunk = beginChunk; chunk < endChunk; ++chunk) {
      chunks.push(chunk);
    }

    return this._requestChunks(chunks);
  }

  requestRanges(ranges = []) {
    const chunksToRequest = [];

    for (const range of ranges) {
      const beginChunk = this.getBeginChunk(range.begin);
      const endChunk = this.getEndChunk(range.end);

      for (let chunk = beginChunk; chunk < endChunk; ++chunk) {
        if (!chunksToRequest.includes(chunk)) {
          chunksToRequest.push(chunk);
        }
      }
    }

    chunksToRequest.sort(function (a, b) {
      return a - b;
    });
    return this._requestChunks(chunksToRequest);
  }

  groupChunks(chunks) {
    const groupedChunks = [];
    let beginChunk = -1;
    let prevChunk = -1;

    for (let i = 0, ii = chunks.length; i < ii; ++i) {
      const chunk = chunks[i];

      if (beginChunk < 0) {
        beginChunk = chunk;
      }

      if (prevChunk >= 0 && prevChunk + 1 !== chunk) {
        groupedChunks.push({
          beginChunk,
          endChunk: prevChunk + 1
        });
        beginChunk = chunk;
      }

      if (i + 1 === chunks.length) {
        groupedChunks.push({
          beginChunk,
          endChunk: chunk + 1
        });
      }

      prevChunk = chunk;
    }

    return groupedChunks;
  }

  onProgress(args) {
    this.msgHandler.send("DocProgress", {
      loaded: this.stream.numChunksLoaded * this.chunkSize + args.loaded,
      total: this.length
    });
  }

  onReceiveData(args) {
    const chunk = args.chunk;
    const isProgressive = args.begin === undefined;
    const begin = isProgressive ? this.progressiveDataLength : args.begin;
    const end = begin + chunk.byteLength;
    const beginChunk = Math.floor(begin / this.chunkSize);
    const endChunk = end < this.length ? Math.floor(end / this.chunkSize) : Math.ceil(end / this.chunkSize);

    if (isProgressive) {
      this.stream.onReceiveProgressiveData(chunk);
      this.progressiveDataLength = end;
    } else {
      this.stream.onReceiveData(begin, chunk);
    }

    if (this.stream.allChunksLoaded()) {
      this._loadedStreamCapability.resolve(this.stream);
    }

    const loadedRequests = [];

    for (let curChunk = beginChunk; curChunk < endChunk; ++curChunk) {
      const requestIds = this._requestsByChunk.get(curChunk);

      if (!requestIds) {
        continue;
      }

      this._requestsByChunk.delete(curChunk);

      for (const requestId of requestIds) {
        const chunksNeeded = this._chunksNeededByRequest.get(requestId);

        if (chunksNeeded.has(curChunk)) {
          chunksNeeded.delete(curChunk);
        }

        if (chunksNeeded.size > 0) {
          continue;
        }

        loadedRequests.push(requestId);
      }
    }

    if (!this.disableAutoFetch && this._requestsByChunk.size === 0) {
      let nextEmptyChunk;

      if (this.stream.numChunksLoaded === 1) {
        const lastChunk = this.stream.numChunks - 1;

        if (!this.stream.hasChunk(lastChunk)) {
          nextEmptyChunk = lastChunk;
        }
      } else {
        nextEmptyChunk = this.stream.nextEmptyChunk(endChunk);
      }

      if (Number.isInteger(nextEmptyChunk)) {
        this._requestChunks([nextEmptyChunk]);
      }
    }

    for (const requestId of loadedRequests) {
      const capability = this._promisesByRequest.get(requestId);

      this._promisesByRequest.delete(requestId);

      capability.resolve();
    }

    this.msgHandler.send("DocProgress", {
      loaded: this.stream.numChunksLoaded * this.chunkSize,
      total: this.length
    });
  }

  onError(err) {
    this._loadedStreamCapability.reject(err);
  }

  getBeginChunk(begin) {
    return Math.floor(begin / this.chunkSize);
  }

  getEndChunk(end) {
    return Math.floor((end - 1) / this.chunkSize) + 1;
  }

  abort(reason) {
    this.aborted = true;

    if (this.pdfNetworkStream) {
      this.pdfNetworkStream.cancelAllRequests(reason);
    }

    for (const capability of this._promisesByRequest.values()) {
      capability.reject(reason);
    }
  }

}

exports.ChunkedStreamManager = ChunkedStreamManager;