106 lines
3.4 KiB
TypeScript
106 lines
3.4 KiB
TypeScript
/*
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* Copyright 2019 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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enum ReadState {
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NO_DATA,
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READING_SIZE,
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READING_MESSAGE,
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}
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export class StreamDecoder {
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private readState: ReadState = ReadState.NO_DATA;
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private readCompressFlag: Buffer = Buffer.alloc(1);
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private readPartialSize: Buffer = Buffer.alloc(4);
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private readSizeRemaining = 4;
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private readMessageSize = 0;
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private readPartialMessage: Buffer[] = [];
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private readMessageRemaining = 0;
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write(data: Buffer): Buffer[] {
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let readHead = 0;
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let toRead: number;
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const result: Buffer[] = [];
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while (readHead < data.length) {
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switch (this.readState) {
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case ReadState.NO_DATA:
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this.readCompressFlag = data.slice(readHead, readHead + 1);
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readHead += 1;
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this.readState = ReadState.READING_SIZE;
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this.readPartialSize.fill(0);
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this.readSizeRemaining = 4;
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this.readMessageSize = 0;
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this.readMessageRemaining = 0;
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this.readPartialMessage = [];
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break;
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case ReadState.READING_SIZE:
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toRead = Math.min(data.length - readHead, this.readSizeRemaining);
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data.copy(
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this.readPartialSize,
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4 - this.readSizeRemaining,
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readHead,
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readHead + toRead
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);
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this.readSizeRemaining -= toRead;
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readHead += toRead;
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// readSizeRemaining >=0 here
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if (this.readSizeRemaining === 0) {
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this.readMessageSize = this.readPartialSize.readUInt32BE(0);
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this.readMessageRemaining = this.readMessageSize;
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if (this.readMessageRemaining > 0) {
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this.readState = ReadState.READING_MESSAGE;
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} else {
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const message = Buffer.concat(
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[this.readCompressFlag, this.readPartialSize],
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5
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);
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this.readState = ReadState.NO_DATA;
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result.push(message);
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}
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}
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break;
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case ReadState.READING_MESSAGE:
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toRead = Math.min(data.length - readHead, this.readMessageRemaining);
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this.readPartialMessage.push(data.slice(readHead, readHead + toRead));
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this.readMessageRemaining -= toRead;
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readHead += toRead;
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// readMessageRemaining >=0 here
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if (this.readMessageRemaining === 0) {
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// At this point, we have read a full message
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const framedMessageBuffers = [
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this.readCompressFlag,
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this.readPartialSize,
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].concat(this.readPartialMessage);
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const framedMessage = Buffer.concat(
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framedMessageBuffers,
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this.readMessageSize + 5
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);
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this.readState = ReadState.NO_DATA;
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result.push(framedMessage);
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}
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break;
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default:
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throw new Error('Unexpected read state');
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}
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}
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return result;
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}
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}
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