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denoland-deno/std/io/util.ts

57 lines
1.6 KiB
TypeScript

// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
const { Buffer, mkdir, open } = Deno;
type File = Deno.File;
type Reader = Deno.Reader;
import * as path from "../path/mod.ts";
import { encode } from "../encoding/utf8.ts";
/**
* Copy bytes from one Uint8Array to another. Bytes from `src` which don't fit
* into `dst` will not be copied.
*
* @param src Source byte array
* @param dst Destination byte array
* @param off Offset into `dst` at which to begin writing values from `src`.
* @return number of bytes copied
*/
export function copyBytes(src: Uint8Array, dst: Uint8Array, off = 0): number {
off = Math.max(0, Math.min(off, dst.byteLength));
const dstBytesAvailable = dst.byteLength - off;
if (src.byteLength > dstBytesAvailable) {
src = src.subarray(0, dstBytesAvailable);
}
dst.set(src, off);
return src.byteLength;
}
export function charCode(s: string): number {
return s.charCodeAt(0);
}
export function stringsReader(s: string): Reader {
return new Buffer(encode(s).buffer);
}
/** Create or open a temporal file at specified directory with prefix and
* postfix
* */
export async function tempFile(
dir: string,
opts: {
prefix?: string;
postfix?: string;
} = { prefix: "", postfix: "" }
): Promise<{ file: File; filepath: string }> {
const r = Math.floor(Math.random() * 1000000);
const filepath = path.resolve(
`${dir}/${opts.prefix || ""}${r}${opts.postfix || ""}`
);
await mkdir(path.dirname(filepath), { recursive: true });
const file = await open(filepath, {
create: true,
read: true,
write: true,
append: true,
});
return { file, filepath };
}