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