deno.land / std@0.177.1 / io / buf_reader.ts
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import { assert } from "../_util/asserts.ts";import { copy } from "../bytes/copy.ts";import type { Reader } from "../types.d.ts";
const DEFAULT_BUF_SIZE = 4096;const MIN_BUF_SIZE = 16;const MAX_CONSECUTIVE_EMPTY_READS = 100;const CR = "\r".charCodeAt(0);const LF = "\n".charCodeAt(0);
export class BufferFullError extends Error { override name = "BufferFullError"; constructor(public partial: Uint8Array) { super("Buffer full"); }}
export class PartialReadError extends Error { override name = "PartialReadError"; partial?: Uint8Array; constructor() { super("Encountered UnexpectedEof, data only partially read"); }}
/** Result type returned by of BufReader.readLine(). */export interface ReadLineResult { line: Uint8Array; more: boolean;}
export class BufReader implements Reader { #buf!: Uint8Array; #rd!: Reader; // Reader provided by caller. #r = 0; // buf read position. #w = 0; // buf write position. #eof = false; // private lastByte: number; // private lastCharSize: number;
/** return new BufReader unless r is BufReader */ static create(r: Reader, size: number = DEFAULT_BUF_SIZE): BufReader { return r instanceof BufReader ? r : new BufReader(r, size); }
constructor(rd: Reader, size: number = DEFAULT_BUF_SIZE) { if (size < MIN_BUF_SIZE) { size = MIN_BUF_SIZE; } this.#reset(new Uint8Array(size), rd); }
/** Returns the size of the underlying buffer in bytes. */ size(): number { return this.#buf.byteLength; }
buffered(): number { return this.#w - this.#r; }
// Reads a new chunk into the buffer. #fill = async () => { // Slide existing data to beginning. if (this.#r > 0) { this.#buf.copyWithin(0, this.#r, this.#w); this.#w -= this.#r; this.#r = 0; }
if (this.#w >= this.#buf.byteLength) { throw Error("bufio: tried to fill full buffer"); }
// Read new data: try a limited number of times. for (let i = MAX_CONSECUTIVE_EMPTY_READS; i > 0; i--) { const rr = await this.#rd.read(this.#buf.subarray(this.#w)); if (rr === null) { this.#eof = true; return; } assert(rr >= 0, "negative read"); this.#w += rr; if (rr > 0) { return; } }
throw new Error( `No progress after ${MAX_CONSECUTIVE_EMPTY_READS} read() calls`, ); };
/** Discards any buffered data, resets all state, and switches * the buffered reader to read from r. */ reset(r: Reader) { this.#reset(this.#buf, r); }
#reset = (buf: Uint8Array, rd: Reader) => { this.#buf = buf; this.#rd = rd; this.#eof = false; // this.lastByte = -1; // this.lastCharSize = -1; };
/** reads data into p. * It returns the number of bytes read into p. * The bytes are taken from at most one Read on the underlying Reader, * hence n may be less than len(p). * To read exactly len(p) bytes, use io.ReadFull(b, p). */ async read(p: Uint8Array): Promise<number | null> { let rr: number | null = p.byteLength; if (p.byteLength === 0) return rr;
if (this.#r === this.#w) { if (p.byteLength >= this.#buf.byteLength) { // Large read, empty buffer. // Read directly into p to avoid copy. const rr = await this.#rd.read(p); const nread = rr ?? 0; assert(nread >= 0, "negative read"); // if (rr.nread > 0) { // this.lastByte = p[rr.nread - 1]; // this.lastCharSize = -1; // } return rr; }
// One read. // Do not use this.fill, which will loop. this.#r = 0; this.#w = 0; rr = await this.#rd.read(this.#buf); if (rr === 0 || rr === null) return rr; assert(rr >= 0, "negative read"); this.#w += rr; }
// copy as much as we can const copied = copy(this.#buf.subarray(this.#r, this.#w), p, 0); this.#r += copied; // this.lastByte = this.buf[this.r - 1]; // this.lastCharSize = -1; return copied; }
/** reads exactly `p.length` bytes into `p`. * * If successful, `p` is returned. * * If the end of the underlying stream has been reached, and there are no more * bytes available in the buffer, `readFull()` returns `null` instead. * * An error is thrown if some bytes could be read, but not enough to fill `p` * entirely before the underlying stream reported an error or EOF. Any error * thrown will have a `partial` property that indicates the slice of the * buffer that has been successfully filled with data. * * Ported from https://golang.org/pkg/io/#ReadFull */ async readFull(p: Uint8Array): Promise<Uint8Array | null> { let bytesRead = 0; while (bytesRead < p.length) { try { const rr = await this.read(p.subarray(bytesRead)); if (rr === null) { if (bytesRead === 0) { return null; } else { throw new PartialReadError(); } } bytesRead += rr; } catch (err) { if (err instanceof PartialReadError) { err.partial = p.subarray(0, bytesRead); } else if (err instanceof Error) { const e = new PartialReadError(); e.partial = p.subarray(0, bytesRead); e.stack = err.stack; e.message = err.message; e.cause = err.cause; throw err; } throw err; } } return p; }
/** Returns the next byte [0, 255] or `null`. */ async readByte(): Promise<number | null> { while (this.#r === this.#w) { if (this.#eof) return null; await this.#fill(); // buffer is empty. } const c = this.#buf[this.#r]; this.#r++; // this.lastByte = c; return c; }
/** readString() reads until the first occurrence of delim in the input, * returning a string containing the data up to and including the delimiter. * If ReadString encounters an error before finding a delimiter, * it returns the data read before the error and the error itself * (often `null`). * ReadString returns err != nil if and only if the returned data does not end * in delim. * For simple uses, a Scanner may be more convenient. */ async readString(delim: string): Promise<string | null> { if (delim.length !== 1) { throw new Error("Delimiter should be a single character"); } const buffer = await this.readSlice(delim.charCodeAt(0)); if (buffer === null) return null; return new TextDecoder().decode(buffer); }
/** `readLine()` is a low-level line-reading primitive. Most callers should * use `readString('\n')` instead or use a Scanner. * * `readLine()` tries to return a single line, not including the end-of-line * bytes. If the line was too long for the buffer then `more` is set and the * beginning of the line is returned. The rest of the line will be returned * from future calls. `more` will be false when returning the last fragment * of the line. The returned buffer is only valid until the next call to * `readLine()`. * * The text returned from ReadLine does not include the line end ("\r\n" or * "\n"). * * When the end of the underlying stream is reached, the final bytes in the * stream are returned. No indication or error is given if the input ends * without a final line end. When there are no more trailing bytes to read, * `readLine()` returns `null`. * * Calling `unreadByte()` after `readLine()` will always unread the last byte * read (possibly a character belonging to the line end) even if that byte is * not part of the line returned by `readLine()`. */ async readLine(): Promise<ReadLineResult | null> { let line: Uint8Array | null = null;
try { line = await this.readSlice(LF); } catch (err) { let partial; if (err instanceof PartialReadError) { partial = err.partial; assert( partial instanceof Uint8Array, "bufio: caught error from `readSlice()` without `partial` property", ); }
// Don't throw if `readSlice()` failed with `BufferFullError`, instead we // just return whatever is available and set the `more` flag. if (!(err instanceof BufferFullError)) { throw err; }
partial = err.partial;
// Handle the case where "\r\n" straddles the buffer. if ( !this.#eof && partial && partial.byteLength > 0 && partial[partial.byteLength - 1] === CR ) { // Put the '\r' back on buf and drop it from line. // Let the next call to ReadLine check for "\r\n". assert(this.#r > 0, "bufio: tried to rewind past start of buffer"); this.#r--; partial = partial.subarray(0, partial.byteLength - 1); }
if (partial) { return { line: partial, more: !this.#eof }; } }
if (line === null) { return null; }
if (line.byteLength === 0) { return { line, more: false }; }
if (line[line.byteLength - 1] == LF) { let drop = 1; if (line.byteLength > 1 && line[line.byteLength - 2] === CR) { drop = 2; } line = line.subarray(0, line.byteLength - drop); } return { line, more: false }; }
/** `readSlice()` reads until the first occurrence of `delim` in the input, * returning a slice pointing at the bytes in the buffer. The bytes stop * being valid at the next read. * * If `readSlice()` encounters an error before finding a delimiter, or the * buffer fills without finding a delimiter, it throws an error with a * `partial` property that contains the entire buffer. * * If `readSlice()` encounters the end of the underlying stream and there are * any bytes left in the buffer, the rest of the buffer is returned. In other * words, EOF is always treated as a delimiter. Once the buffer is empty, * it returns `null`. * * Because the data returned from `readSlice()` will be overwritten by the * next I/O operation, most clients should use `readString()` instead. */ async readSlice(delim: number): Promise<Uint8Array | null> { let s = 0; // search start index let slice: Uint8Array | undefined;
while (true) { // Search buffer. let i = this.#buf.subarray(this.#r + s, this.#w).indexOf(delim); if (i >= 0) { i += s; slice = this.#buf.subarray(this.#r, this.#r + i + 1); this.#r += i + 1; break; }
// EOF? if (this.#eof) { if (this.#r === this.#w) { return null; } slice = this.#buf.subarray(this.#r, this.#w); this.#r = this.#w; break; }
// Buffer full? if (this.buffered() >= this.#buf.byteLength) { this.#r = this.#w; // #4521 The internal buffer should not be reused across reads because it causes corruption of data. const oldbuf = this.#buf; const newbuf = this.#buf.slice(0); this.#buf = newbuf; throw new BufferFullError(oldbuf); }
s = this.#w - this.#r; // do not rescan area we scanned before
// Buffer is not full. try { await this.#fill(); } catch (err) { if (err instanceof PartialReadError) { err.partial = slice; } else if (err instanceof Error) { const e = new PartialReadError(); e.partial = slice; e.stack = err.stack; e.message = err.message; e.cause = err.cause; throw err; } throw err; } }
// Handle last byte, if any. // const i = slice.byteLength - 1; // if (i >= 0) { // this.lastByte = slice[i]; // this.lastCharSize = -1 // }
return slice; }
/** `peek()` returns the next `n` bytes without advancing the reader. The * bytes stop being valid at the next read call. * * When the end of the underlying stream is reached, but there are unread * bytes left in the buffer, those bytes are returned. If there are no bytes * left in the buffer, it returns `null`. * * If an error is encountered before `n` bytes are available, `peek()` throws * an error with the `partial` property set to a slice of the buffer that * contains the bytes that were available before the error occurred. */ async peek(n: number): Promise<Uint8Array | null> { if (n < 0) { throw Error("negative count"); }
let avail = this.#w - this.#r; while (avail < n && avail < this.#buf.byteLength && !this.#eof) { try { await this.#fill(); } catch (err) { if (err instanceof PartialReadError) { err.partial = this.#buf.subarray(this.#r, this.#w); } else if (err instanceof Error) { const e = new PartialReadError(); e.partial = this.#buf.subarray(this.#r, this.#w); e.stack = err.stack; e.message = err.message; e.cause = err.cause; throw err; } throw err; } avail = this.#w - this.#r; }
if (avail === 0 && this.#eof) { return null; } else if (avail < n && this.#eof) { return this.#buf.subarray(this.#r, this.#r + avail); } else if (avail < n) { throw new BufferFullError(this.#buf.subarray(this.#r, this.#w)); }
return this.#buf.subarray(this.#r, this.#r + n); }}
std
Version Info
10 months ago
