@oazmi/build-tools
Version:
general deno build tool scripts which I practically use in all of my typescript repos
78 lines (77 loc) • 3.25 kB
JavaScript
// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
import * as dntShim from "../../../../../_dnt.shims.js";
import { copy as copyBytes } from "../../bytes/0.223.0/copy.js";
import { assert } from "../../assert/0.223.0/assert.js";
const DEFAULT_BUFFER_SIZE = 32 * 1024;
/**
* Read a range of bytes from a file or other resource that is readable and
* seekable. The range start and end are inclusive of the bytes within that
* range.
*
* ```ts
* import { assertEquals } from "@std/assert/assert-equals";
* import { readRange } from "@std/io/read-range";
*
* // Read the first 10 bytes of a file
* const file = await Deno.open("example.txt", { read: true });
* const bytes = await readRange(file, { start: 0, end: 9 });
* assertEquals(bytes.length, 10);
* ```
*
* @deprecated (will be removed after 1.0.0) Use the {@link https://developer.mozilla.org/en-US/docs/Web/API/Streams_API | Web Streams API} instead.
*/
export async function readRange(r, range) {
// byte ranges are inclusive, so we have to add one to the end
let length = range.end - range.start + 1;
assert(length > 0, "Invalid byte range was passed.");
await r.seek(range.start, dntShim.Deno.SeekMode.Start);
const result = new Uint8Array(length);
let off = 0;
while (length) {
const p = new Uint8Array(Math.min(length, DEFAULT_BUFFER_SIZE));
const nread = await r.read(p);
assert(nread !== null, "Unexpected EOF reach while reading a range.");
assert(nread > 0, "Unexpected read of 0 bytes while reading a range.");
copyBytes(p, result, off);
off += nread;
length -= nread;
assert(length >= 0, "Unexpected length remaining after reading range.");
}
return result;
}
/**
* Read a range of bytes synchronously from a file or other resource that is
* readable and seekable. The range start and end are inclusive of the bytes
* within that range.
*
* ```ts
* import { assertEquals } from "@std/assert/assert-equals";
* import { readRangeSync } from "@std/io/read-range";
*
* // Read the first 10 bytes of a file
* const file = Deno.openSync("example.txt", { read: true });
* const bytes = readRangeSync(file, { start: 0, end: 9 });
* assertEquals(bytes.length, 10);
* ```
*
* @deprecated (will be removed after 1.0.0) Use the {@link https://developer.mozilla.org/en-US/docs/Web/API/Streams_API | Web Streams API} instead.
*/
export function readRangeSync(r, range) {
// byte ranges are inclusive, so we have to add one to the end
let length = range.end - range.start + 1;
assert(length > 0, "Invalid byte range was passed.");
r.seekSync(range.start, dntShim.Deno.SeekMode.Start);
const result = new Uint8Array(length);
let off = 0;
while (length) {
const p = new Uint8Array(Math.min(length, DEFAULT_BUFFER_SIZE));
const nread = r.readSync(p);
assert(nread !== null, "Unexpected EOF reach while reading a range.");
assert(nread > 0, "Unexpected read of 0 bytes while reading a range.");
copyBytes(p, result, off);
off += nread;
length -= nread;
assert(length >= 0, "Unexpected length remaining after reading range.");
}
return result;
}