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99 lines
3.5 KiB
TypeScript
99 lines
3.5 KiB
TypeScript
// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
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import { copy as copyBytes } from "@std/bytes/copy";
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import { assert } from "@std/assert/assert";
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import type { Reader, ReaderSync } from "./types.ts";
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const DEFAULT_BUFFER_SIZE = 32 * 1024;
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/**
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* @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.
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*/
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export interface ByteRange {
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/** The 0 based index of the start byte for a range. */
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start: number;
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/** The 0 based index of the end byte for a range, which is inclusive. */
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end: number;
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}
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/**
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* Read a range of bytes from a file or other resource that is readable and
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* seekable. The range start and end are inclusive of the bytes within that
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* range.
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*
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* ```ts
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* import { assertEquals } from "@std/assert/assert_equals";
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* import { readRange } from "@std/io/read_range";
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*
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* // Read the first 10 bytes of a file
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* const file = await Deno.open("example.txt", { read: true });
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* const bytes = await readRange(file, { start: 0, end: 9 });
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* assertEquals(bytes.length, 10);
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* ```
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*
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* @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.
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*/
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export async function readRange(
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r: Reader & Deno.Seeker,
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range: ByteRange,
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): Promise<Uint8Array> {
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// byte ranges are inclusive, so we have to add one to the end
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let length = range.end - range.start + 1;
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assert(length > 0, "Invalid byte range was passed.");
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await r.seek(range.start, Deno.SeekMode.Start);
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const result = new Uint8Array(length);
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let off = 0;
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while (length) {
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const p = new Uint8Array(Math.min(length, DEFAULT_BUFFER_SIZE));
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const nread = await r.read(p);
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assert(nread !== null, "Unexpected EOF reach while reading a range.");
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assert(nread > 0, "Unexpected read of 0 bytes while reading a range.");
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copyBytes(p, result, off);
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off += nread;
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length -= nread;
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assert(length >= 0, "Unexpected length remaining after reading range.");
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}
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return result;
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}
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/**
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* Read a range of bytes synchronously from a file or other resource that is
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* readable and seekable. The range start and end are inclusive of the bytes
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* within that range.
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*
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* ```ts
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* import { assertEquals } from "@std/assert/assert_equals";
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* import { readRangeSync } from "@std/io/read_range";
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*
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* // Read the first 10 bytes of a file
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* const file = Deno.openSync("example.txt", { read: true });
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* const bytes = readRangeSync(file, { start: 0, end: 9 });
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* assertEquals(bytes.length, 10);
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* ```
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*
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* @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.
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*/
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export function readRangeSync(
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r: ReaderSync & Deno.SeekerSync,
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range: ByteRange,
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): Uint8Array {
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// byte ranges are inclusive, so we have to add one to the end
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let length = range.end - range.start + 1;
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assert(length > 0, "Invalid byte range was passed.");
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r.seekSync(range.start, Deno.SeekMode.Start);
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const result = new Uint8Array(length);
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let off = 0;
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while (length) {
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const p = new Uint8Array(Math.min(length, DEFAULT_BUFFER_SIZE));
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const nread = r.readSync(p);
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assert(nread !== null, "Unexpected EOF reach while reading a range.");
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assert(nread > 0, "Unexpected read of 0 bytes while reading a range.");
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copyBytes(p, result, off);
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off += nread;
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length -= nread;
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assert(length >= 0, "Unexpected length remaining after reading range.");
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}
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return result;
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}
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