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251 lines
8.3 KiB
TypeScript
251 lines
8.3 KiB
TypeScript
// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
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// This module is browser compatible.
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import { assert } from "@std/assert/assert";
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import { copy } from "@std/bytes/copy";
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import type { Reader, ReaderSync, Writer, WriterSync } from "./types.ts";
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// MIN_READ is the minimum ArrayBuffer size passed to a read call by
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// buffer.ReadFrom. As long as the Buffer has at least MIN_READ bytes beyond
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// what is required to hold the contents of r, readFrom() will not grow the
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// underlying buffer.
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const MIN_READ = 32 * 1024;
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const MAX_SIZE = 2 ** 32 - 2;
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/** A variable-sized buffer of bytes with `read()` and `write()` methods.
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*
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* Buffer is almost always used with some I/O like files and sockets. It allows
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* one to buffer up a download from a socket. Buffer grows and shrinks as
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* necessary.
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*
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* Buffer is NOT the same thing as Node's Buffer. Node's Buffer was created in
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* 2009 before JavaScript had the concept of ArrayBuffers. It's simply a
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* non-standard ArrayBuffer.
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*
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* ArrayBuffer is a fixed memory allocation. Buffer is implemented on top of
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* ArrayBuffer.
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*
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* Based on {@link https://golang.org/pkg/bytes/#Buffer | Go Buffer}.
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*/
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export class Buffer implements Writer, WriterSync, Reader, ReaderSync {
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#buf: Uint8Array; // contents are the bytes buf[off : len(buf)]
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#off = 0; // read at buf[off], write at buf[buf.byteLength]
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constructor(ab?: ArrayBufferLike | ArrayLike<number>) {
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this.#buf = ab === undefined ? new Uint8Array(0) : new Uint8Array(ab);
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}
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/** Returns a slice holding the unread portion of the buffer.
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*
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* The slice is valid for use only until the next buffer modification (that
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* is, only until the next call to a method like `read()`, `write()`,
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* `reset()`, or `truncate()`). If `options.copy` is false the slice aliases the buffer content at
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* least until the next buffer modification, so immediate changes to the
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* slice will affect the result of future reads.
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* @param [options={ copy: true }]
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*/
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bytes(options = { copy: true }): Uint8Array {
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if (options.copy === false) return this.#buf.subarray(this.#off);
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return this.#buf.slice(this.#off);
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}
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/** Returns whether the unread portion of the buffer is empty. */
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empty(): boolean {
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return this.#buf.byteLength <= this.#off;
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}
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/** A read only number of bytes of the unread portion of the buffer. */
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get length(): number {
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return this.#buf.byteLength - this.#off;
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}
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/** The read only capacity of the buffer's underlying byte slice, that is,
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* the total space allocated for the buffer's data. */
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get capacity(): number {
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return this.#buf.buffer.byteLength;
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}
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/** Discards all but the first `n` unread bytes from the buffer but
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* continues to use the same allocated storage. It throws if `n` is
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* negative or greater than the length of the buffer. */
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truncate(n: number) {
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if (n === 0) {
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this.reset();
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return;
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}
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if (n < 0 || n > this.length) {
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throw Error("bytes.Buffer: truncation out of range");
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}
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this.#reslice(this.#off + n);
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}
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reset() {
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this.#reslice(0);
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this.#off = 0;
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}
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#tryGrowByReslice(n: number) {
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const l = this.#buf.byteLength;
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if (n <= this.capacity - l) {
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this.#reslice(l + n);
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return l;
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}
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return -1;
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}
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#reslice(len: number) {
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assert(len <= this.#buf.buffer.byteLength);
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this.#buf = new Uint8Array(this.#buf.buffer, 0, len);
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}
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/** Reads the next `p.length` bytes from the buffer or until the buffer is
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* drained. Returns the number of bytes read. If the buffer has no data to
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* return, the return is EOF (`null`). */
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readSync(p: Uint8Array): number | null {
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if (this.empty()) {
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// Buffer is empty, reset to recover space.
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this.reset();
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if (p.byteLength === 0) {
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// this edge case is tested in 'bufferReadEmptyAtEOF' test
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return 0;
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}
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return null;
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}
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const nread = copy(this.#buf.subarray(this.#off), p);
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this.#off += nread;
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return nread;
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}
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/** Reads the next `p.length` bytes from the buffer or until the buffer is
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* drained. Resolves to the number of bytes read. If the buffer has no
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* data to return, resolves to EOF (`null`).
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*
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* NOTE: This methods reads bytes synchronously; it's provided for
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* compatibility with `Reader` interfaces.
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*/
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read(p: Uint8Array): Promise<number | null> {
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const rr = this.readSync(p);
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return Promise.resolve(rr);
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}
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writeSync(p: Uint8Array): number {
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const m = this.#grow(p.byteLength);
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return copy(p, this.#buf, m);
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}
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/** NOTE: This methods writes bytes synchronously; it's provided for
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* compatibility with `Writer` interface. */
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write(p: Uint8Array): Promise<number> {
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const n = this.writeSync(p);
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return Promise.resolve(n);
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}
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#grow(n: number) {
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const m = this.length;
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// If buffer is empty, reset to recover space.
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if (m === 0 && this.#off !== 0) {
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this.reset();
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}
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// Fast: Try to grow by means of a reslice.
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const i = this.#tryGrowByReslice(n);
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if (i >= 0) {
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return i;
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}
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const c = this.capacity;
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if (n <= Math.floor(c / 2) - m) {
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// We can slide things down instead of allocating a new
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// ArrayBuffer. We only need m+n <= c to slide, but
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// we instead let capacity get twice as large so we
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// don't spend all our time copying.
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copy(this.#buf.subarray(this.#off), this.#buf);
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} else if (c + n > MAX_SIZE) {
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throw new Error("The buffer cannot be grown beyond the maximum size.");
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} else {
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// Not enough space anywhere, we need to allocate.
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const buf = new Uint8Array(Math.min(2 * c + n, MAX_SIZE));
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copy(this.#buf.subarray(this.#off), buf);
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this.#buf = buf;
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}
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// Restore this.#off and len(this.#buf).
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this.#off = 0;
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this.#reslice(Math.min(m + n, MAX_SIZE));
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return m;
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}
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/** Grows the buffer's capacity, if necessary, to guarantee space for
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* another `n` bytes. After `.grow(n)`, at least `n` bytes can be written to
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* the buffer without another allocation. If `n` is negative, `.grow()` will
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* throw. If the buffer can't grow it will throw an error.
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*
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* Based on Go Lang's
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* {@link https://golang.org/pkg/bytes/#Buffer.Grow | Buffer.Grow}. */
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grow(n: number) {
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if (n < 0) {
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throw Error("Buffer.grow: negative count");
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}
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const m = this.#grow(n);
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this.#reslice(m);
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}
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/** Reads data from `r` until EOF (`null`) and appends it to the buffer,
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* growing the buffer as needed. It resolves to the number of bytes read.
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* If the buffer becomes too large, `.readFrom()` will reject with an error.
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*
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* Based on Go Lang's
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* {@link https://golang.org/pkg/bytes/#Buffer.ReadFrom | Buffer.ReadFrom}. */
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async readFrom(r: Reader): Promise<number> {
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let n = 0;
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const tmp = new Uint8Array(MIN_READ);
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while (true) {
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const shouldGrow = this.capacity - this.length < MIN_READ;
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// read into tmp buffer if there's not enough room
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// otherwise read directly into the internal buffer
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const buf = shouldGrow
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? tmp
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: new Uint8Array(this.#buf.buffer, this.length);
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const nread = await r.read(buf);
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if (nread === null) {
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return n;
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}
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// write will grow if needed
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if (shouldGrow) this.writeSync(buf.subarray(0, nread));
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else this.#reslice(this.length + nread);
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n += nread;
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}
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}
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/** Reads data from `r` until EOF (`null`) and appends it to the buffer,
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* growing the buffer as needed. It returns the number of bytes read. If the
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* buffer becomes too large, `.readFromSync()` will throw an error.
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*
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* Based on Go Lang's
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* {@link https://golang.org/pkg/bytes/#Buffer.ReadFrom | Buffer.ReadFrom}. */
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readFromSync(r: ReaderSync): number {
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let n = 0;
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const tmp = new Uint8Array(MIN_READ);
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while (true) {
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const shouldGrow = this.capacity - this.length < MIN_READ;
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// read into tmp buffer if there's not enough room
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// otherwise read directly into the internal buffer
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const buf = shouldGrow
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? tmp
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: new Uint8Array(this.#buf.buffer, this.length);
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const nread = r.readSync(buf);
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if (nread === null) {
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return n;
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}
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// write will grow if needed
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if (shouldGrow) this.writeSync(buf.subarray(0, nread));
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else this.#reslice(this.length + nread);
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n += nread;
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}
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}
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}
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