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grpc-js: extract reusable stream decoding logic
This commit pulls the stream decoding logic into a separate class so that it can be reused by the server code.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,98 @@ | ||
| /* | ||
| * Copyright 2019 gRPC authors. | ||
| * | ||
| * 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. | ||
| * | ||
| */ | ||
|
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| enum ReadState { | ||
| NO_DATA, | ||
| READING_SIZE, | ||
| READING_MESSAGE | ||
| } | ||
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| export class StreamDecoder { | ||
| private readState: ReadState = ReadState.NO_DATA; | ||
| private readCompressFlag: Buffer = Buffer.alloc(1); | ||
| private readPartialSize: Buffer = Buffer.alloc(4); | ||
| private readSizeRemaining = 4; | ||
| private readMessageSize = 0; | ||
| private readPartialMessage: Buffer[] = []; | ||
| private readMessageRemaining = 0; | ||
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| write(data: Buffer): Buffer|null { | ||
| let readHead = 0; | ||
| let toRead: number; | ||
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| while (readHead < data.length) { | ||
| switch (this.readState) { | ||
| case ReadState.NO_DATA: | ||
| this.readCompressFlag = data.slice(readHead, readHead + 1); | ||
| readHead += 1; | ||
| this.readState = ReadState.READING_SIZE; | ||
| this.readPartialSize.fill(0); | ||
| this.readSizeRemaining = 4; | ||
| this.readMessageSize = 0; | ||
| this.readMessageRemaining = 0; | ||
| this.readPartialMessage = []; | ||
| break; | ||
| case ReadState.READING_SIZE: | ||
| toRead = Math.min(data.length - readHead, this.readSizeRemaining); | ||
| data.copy( | ||
| this.readPartialSize, 4 - this.readSizeRemaining, readHead, | ||
| readHead + toRead); | ||
| this.readSizeRemaining -= toRead; | ||
| readHead += toRead; | ||
| // readSizeRemaining >=0 here | ||
| if (this.readSizeRemaining === 0) { | ||
| this.readMessageSize = this.readPartialSize.readUInt32BE(0); | ||
| this.readMessageRemaining = this.readMessageSize; | ||
| if (this.readMessageRemaining > 0) { | ||
| this.readState = ReadState.READING_MESSAGE; | ||
| } else { | ||
| const message = Buffer.concat( | ||
| [this.readCompressFlag, this.readPartialSize], 5); | ||
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| this.readState = ReadState.NO_DATA; | ||
| return message; | ||
| } | ||
| } | ||
| break; | ||
| case ReadState.READING_MESSAGE: | ||
| toRead = Math.min(data.length - readHead, this.readMessageRemaining); | ||
| this.readPartialMessage.push(data.slice(readHead, readHead + toRead)); | ||
| this.readMessageRemaining -= toRead; | ||
| readHead += toRead; | ||
| // readMessageRemaining >=0 here | ||
| if (this.readMessageRemaining === 0) { | ||
| // At this point, we have read a full message | ||
| const framedMessageBuffers = [ | ||
| this.readCompressFlag, this.readPartialSize | ||
| ].concat(this.readPartialMessage); | ||
| const framedMessage = | ||
| Buffer.concat(framedMessageBuffers, this.readMessageSize + 5); | ||
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| this.readState = ReadState.NO_DATA; | ||
| return framedMessage; | ||
| } | ||
| break; | ||
| default: | ||
| throw new Error('Unexpected read state'); | ||
| } | ||
| } | ||
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| return null; | ||
| } | ||
| } |