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37 lines
1.2 KiB
TypeScript
37 lines
1.2 KiB
TypeScript
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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
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import { BufReader } from "./bufio.ts";
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/* Read big endian 16bit short from BufReader */
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export async function readShort(buf: BufReader): Promise<number> {
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const [high, low] = [await buf.readByte(), await buf.readByte()];
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return (high << 8) | low;
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}
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/* Read big endian 32bit integer from BufReader */
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export async function readInt(buf: BufReader): Promise<number> {
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const [high, low] = [await readShort(buf), await readShort(buf)];
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return (high << 16) | low;
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}
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const BIT32 = 0xffffffff;
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/* Read big endian 64bit long from BufReader */
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export async function readLong(buf: BufReader): Promise<number> {
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const [high, low] = [await readInt(buf), await readInt(buf)];
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// ECMAScript doesn't support 64bit bit ops.
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return high ? high * (BIT32 + 1) + low : low;
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}
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/* Slice number into 64bit big endian byte array */
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export function sliceLongToBytes(d: number, dest = new Array(8)): number[] {
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let mask = 0xff;
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let low = (d << 32) >>> 32;
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let high = (d - low) / (BIT32 + 1);
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let shift = 24;
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for (let i = 0; i < 4; i++) {
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dest[i] = (high >>> shift) & mask;
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dest[i + 4] = (low >>> shift) & mask;
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shift -= 8;
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}
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return dest;
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}
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