@azure/storage-common
Version:
Azure Storage Common Client Library for JavaScript
97 lines • 3.69 kB
JavaScript
// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.
import { Readable } from "node:stream";
/**
* This class generates a readable stream from the data in an array of buffers.
*/
export class BuffersStream extends Readable {
buffers;
byteLength;
/**
* The offset of data to be read in the current buffer.
*/
byteOffsetInCurrentBuffer;
/**
* The index of buffer to be read in the array of buffers.
*/
bufferIndex;
/**
* The total length of data already read.
*/
pushedBytesLength;
/**
* Creates an instance of BuffersStream that will emit the data
* contained in the array of buffers.
*
* @param buffers - Array of buffers containing the data
* @param byteLength - The total length of data contained in the buffers
*/
constructor(buffers, byteLength, options) {
super(options);
this.buffers = buffers;
this.byteLength = byteLength;
this.byteOffsetInCurrentBuffer = 0;
this.bufferIndex = 0;
this.pushedBytesLength = 0;
// check byteLength is no larger than buffers[] total length
let buffersLength = 0;
for (const buf of this.buffers) {
buffersLength += buf.byteLength;
}
if (buffersLength < this.byteLength) {
throw new Error("Data size shouldn't be larger than the total length of buffers.");
}
}
/**
* Internal _read() that will be called when the stream wants to pull more data in.
*
* @param size - Optional. The size of data to be read
*/
_read(size) {
if (this.pushedBytesLength >= this.byteLength) {
this.push(null);
}
if (!size) {
size = this.readableHighWaterMark;
}
const outBuffers = [];
let i = 0;
while (i < size && this.pushedBytesLength < this.byteLength) {
// The last buffer may be longer than the data it contains.
const remainingDataInAllBuffers = this.byteLength - this.pushedBytesLength;
const remainingCapacityInThisBuffer = this.buffers[this.bufferIndex].byteLength - this.byteOffsetInCurrentBuffer;
const remaining = Math.min(remainingCapacityInThisBuffer, remainingDataInAllBuffers);
if (remaining > size - i) {
// chunkSize = size - i
const end = this.byteOffsetInCurrentBuffer + size - i;
outBuffers.push(this.buffers[this.bufferIndex].slice(this.byteOffsetInCurrentBuffer, end));
this.pushedBytesLength += size - i;
this.byteOffsetInCurrentBuffer = end;
i = size;
break;
}
else {
// chunkSize = remaining
const end = this.byteOffsetInCurrentBuffer + remaining;
outBuffers.push(this.buffers[this.bufferIndex].slice(this.byteOffsetInCurrentBuffer, end));
if (remaining === remainingCapacityInThisBuffer) {
// this.buffers[this.bufferIndex] used up, shift to next one
this.byteOffsetInCurrentBuffer = 0;
this.bufferIndex++;
}
else {
this.byteOffsetInCurrentBuffer = end;
}
this.pushedBytesLength += remaining;
i += remaining;
}
}
if (outBuffers.length > 1) {
this.push(Buffer.concat(outBuffers));
}
else if (outBuffers.length === 1) {
this.push(outBuffers[0]);
}
}
}
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