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88 lines
2.5 KiB
TypeScript
88 lines
2.5 KiB
TypeScript
// Loaded from https://deno.land/std@0.81.0/io/ioutil.ts
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// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
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import type { BufReader } from "./bufio.ts";
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type Reader = Deno.Reader;
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type Writer = Deno.Writer;
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import { assert } from "../_util/assert.ts";
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const DEFAULT_BUFFER_SIZE = 32 * 1024;
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/** copy N size at the most.
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* If read size is lesser than N, then returns nread
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* */
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export async function copyN(
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r: Reader,
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dest: Writer,
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size: number,
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): Promise<number> {
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let bytesRead = 0;
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let buf = new Uint8Array(DEFAULT_BUFFER_SIZE);
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while (bytesRead < size) {
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if (size - bytesRead < DEFAULT_BUFFER_SIZE) {
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buf = new Uint8Array(size - bytesRead);
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}
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const result = await r.read(buf);
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const nread = result ?? 0;
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bytesRead += nread;
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if (nread > 0) {
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let n = 0;
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while (n < nread) {
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n += await dest.write(buf.slice(n, nread));
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}
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assert(n === nread, "could not write");
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}
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if (result === null) {
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break;
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}
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}
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return bytesRead;
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}
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/** Read big endian 16bit short from BufReader */
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export async function readShort(buf: BufReader): Promise<number | null> {
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const high = await buf.readByte();
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if (high === null) return null;
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const low = await buf.readByte();
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if (low === null) throw new Deno.errors.UnexpectedEof();
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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 | null> {
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const high = await readShort(buf);
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if (high === null) return null;
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const low = await readShort(buf);
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if (low === null) throw new Deno.errors.UnexpectedEof();
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return (high << 16) | low;
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}
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const MAX_SAFE_INTEGER = BigInt(Number.MAX_SAFE_INTEGER);
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/** Read big endian 64bit long from BufReader */
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export async function readLong(buf: BufReader): Promise<number | null> {
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const high = await readInt(buf);
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if (high === null) return null;
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const low = await readInt(buf);
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if (low === null) throw new Deno.errors.UnexpectedEof();
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const big = (BigInt(high) << 32n) | BigInt(low);
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// We probably should provide a similar API that returns BigInt values.
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if (big > MAX_SAFE_INTEGER) {
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throw new RangeError(
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"Long value too big to be represented as a JavaScript number.",
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);
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}
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return Number(big);
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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 big = BigInt(d);
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for (let i = 0; i < 8; i++) {
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dest[7 - i] = Number(big & 0xffn);
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big >>= 8n;
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}
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return dest;
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}
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