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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 "../_util/assert.ts";
const DEFAULT_BUFFER_SIZE = 32 * 1024;
/** copy N size at the most.
* If read size is lesser than N, then returns nread
* */
export async function copyN(
r: Reader,
dest: Writer,
size: number
): Promise<number> {
let bytesRead = 0;
let buf = new Uint8Array(DEFAULT_BUFFER_SIZE);
while (bytesRead < size) {
if (size - bytesRead < DEFAULT_BUFFER_SIZE) {
buf = new Uint8Array(size - bytesRead);
}
const result = await r.read(buf);
const nread = result ?? 0;
bytesRead += nread;
if (nread > 0) {
let n = 0;
while (n < nread) {
n += await dest.write(buf.slice(n, nread));
}
assert(n === nread, "could not write");
}
if (result === null) {
break;
}
}
return bytesRead;
}
/** Read big endian 16bit short from BufReader */
export async function readShort(buf: BufReader): Promise<number | null> {
const high = await buf.readByte();
if (high === null) return null;
const low = await buf.readByte();
if (low === null) throw new Deno.errors.UnexpectedEof();
return (high << 8) | low;
}
/** Read big endian 32bit integer from BufReader */
export async function readInt(buf: BufReader): Promise<number | null> {
const high = await readShort(buf);
if (high === null) return null;
const low = await readShort(buf);
if (low === null) 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 | null> {
const high = await readInt(buf);
if (high === null) return null;
const low = await readInt(buf);
if (low === null) 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;
}
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