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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
import { copy } from "../bytes/copy.ts";import {  assert,  assertEquals,  assertRejects,  assertThrows,} from "../assert/mod.ts";import { readRange, readRangeSync } from "./read_range.ts";import type { Closer, Reader, ReaderSync } from "./types.ts";
// N controls how many iterations of certain checks are performed.const N = 100;let testBytes: Uint8Array | undefined;
export function init() {  if (testBytes === undefined) {    testBytes = new Uint8Array(N);    for (let i = 0; i < N; i++) {      testBytes[i] = "a".charCodeAt(0) + (i % 26);    }  }}
class MockFile  implements Deno.Seeker, Deno.SeekerSync, Reader, ReaderSync, Closer {  #buf: Uint8Array;  #closed = false;  #offset = 0;
  get closed() {    return this.#closed;  }
  constructor(buf: Uint8Array) {    this.#buf = buf;  }
  close() {    this.#closed = true;  }
  read(p: Uint8Array): Promise<number | null> {    if (this.#offset >= this.#buf.length) {      return Promise.resolve(null);    }    const nread = Math.min(p.length, 16_384, this.#buf.length - this.#offset);    if (nread === 0) {      return Promise.resolve(0);    }    copy(this.#buf.subarray(this.#offset, this.#offset + nread), p);    this.#offset += nread;    return Promise.resolve(nread);  }
  readSync(p: Uint8Array): number | null {    if (this.#offset >= this.#buf.length) {      return null;    }    const nread = Math.min(p.length, 16_384, this.#buf.length - this.#offset);    if (nread === 0) {      return 0;    }    copy(this.#buf.subarray(this.#offset, this.#offset + nread), p);    this.#offset += nread;    return nread;  }
  seek(offset: number, whence: Deno.SeekMode): Promise<number> {    assert(whence === Deno.SeekMode.Start);    if (offset >= this.#buf.length) {      return Promise.reject(new RangeError("attempted to seek past end"));    }    this.#offset = offset;    return Promise.resolve(this.#offset);  }
  seekSync(offset: number, whence: Deno.SeekMode): number {    assert(whence === Deno.SeekMode.Start);    if (offset >= this.#buf.length) {      throw new RangeError("attempted to seek past end");    }    this.#offset = offset;    return this.#offset;  }}
Deno.test({  name: "readRange",  async fn() {    init();    assert(testBytes);    const file = new MockFile(testBytes);    const actual = await readRange(file, { start: 0, end: 9 });    assertEquals(actual, testBytes.subarray(0, 10));  },});
Deno.test({  name: "readRange - invalid range",  async fn() {    init();    assert(testBytes);    const file = new MockFile(testBytes);    await assertRejects(      async () => {        await readRange(file, { start: 100, end: 0 });      },      Error,      "Invalid byte range was passed.",    );  },});
Deno.test({  name: "readRange - read past EOF",  async fn() {    init();    assert(testBytes);    const file = new MockFile(testBytes);    await assertRejects(      async () => {        await readRange(file, { start: 99, end: 100 });      },      Error,      "Unexpected EOF reach while reading a range.",    );  },});
Deno.test({  name: "readRangeSync",  fn() {    init();    assert(testBytes);    const file = new MockFile(testBytes);    const actual = readRangeSync(file, { start: 0, end: 9 });    assertEquals(actual, testBytes.subarray(0, 10));  },});
Deno.test({  name: "readRangeSync - invalid range",  fn() {    init();    assert(testBytes);    const file = new MockFile(testBytes);    assertThrows(      () => {        readRangeSync(file, { start: 100, end: 0 });      },      Error,      "Invalid byte range was passed.",    );  },});
Deno.test({  name: "readRangeSync - read past EOF",  fn() {    init();    assert(testBytes);    const file = new MockFile(testBytes);    assertThrows(      () => {        readRangeSync(file, { start: 99, end: 100 });      },      Error,      "Unexpected EOF reach while reading a range.",    );  },});