variableLengthQuantity.ts

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import { VSBuffer } from '../vs/base/common/buffer';

/** Reads a 32-bit integer from the buffer */
export function readVariableLengthQuantity(buffer: VSBuffer, offset: number): { value: number; consumed: number } {
	let result = 0;
	let consumed = 0;
	let byte: number;

	do {
		byte = buffer.readUInt8(offset + consumed);
		result |= (byte & 0x7f) << (consumed * 7);
		consumed++;
	} while (byte & 0x80);

	return { value: result, consumed };
}

/** Writes a 32 bit integer to the buffer */
export function writeVariableLengthQuantity(i: number): VSBuffer {
	if (i !== (i | 0)) {
		throw new Error(`${i} is not an int32.`);
	}

	const result: number[] = [];
	do {
		let byte = i & 0x7f;
		i >>>= 7;
		if (i !== 0) {
			byte |= 0x80;
		}
		result.push(byte);
	} while (i !== 0);

	return VSBuffer.fromByteArray(result);
}