deno.land / std@0.166.0 / node / string_decoder.ts
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import { Buffer } from "./buffer.ts";import { normalizeEncoding as castEncoding, notImplemented } from "./_utils.ts";
enum NotImplemented { "ascii", "latin1", "utf16le",}
function normalizeEncoding(enc?: string): string { const encoding = castEncoding(enc ?? null); if (encoding && encoding in NotImplemented) notImplemented(encoding); if (!encoding && typeof enc === "string" && enc.toLowerCase() !== "raw") { throw new Error(`Unknown encoding: ${enc}`); } return String(encoding);}
/** * Check is `ArrayBuffer` and not `TypedArray`. Typescript allowed `TypedArray` to be passed as `ArrayBuffer` and does not do a deep check */
function isBufferType(buf: Buffer) { return buf instanceof ArrayBuffer && buf.BYTES_PER_ELEMENT;}
/* * Checks the type of a UTF-8 byte, whether it's ASCII, a leading byte, or a * continuation byte. If an invalid byte is detected, -2 is returned. * */function utf8CheckByte(byte: number): number { if (byte <= 0x7f) return 0; else if (byte >> 5 === 0x06) return 2; else if (byte >> 4 === 0x0e) return 3; else if (byte >> 3 === 0x1e) return 4; return byte >> 6 === 0x02 ? -1 : -2;}
/* * Checks at most 3 bytes at the end of a Buffer in order to detect an * incomplete multi-byte UTF-8 character. The total number of bytes (2, 3, or 4) * needed to complete the UTF-8 character (if applicable) are returned. * */function utf8CheckIncomplete( self: StringDecoderBase, buf: Buffer, i: number,): number { let j = buf.length - 1; if (j < i) return 0; let nb = utf8CheckByte(buf[j]); if (nb >= 0) { if (nb > 0) self.lastNeed = nb - 1; return nb; } if (--j < i || nb === -2) return 0; nb = utf8CheckByte(buf[j]); if (nb >= 0) { if (nb > 0) self.lastNeed = nb - 2; return nb; } if (--j < i || nb === -2) return 0; nb = utf8CheckByte(buf[j]); if (nb >= 0) { if (nb > 0) { if (nb === 2) nb = 0; else self.lastNeed = nb - 3; } return nb; } return 0;}
/* * Validates as many continuation bytes for a multi-byte UTF-8 character as * needed or are available. If we see a non-continuation byte where we expect * one, we "replace" the validated continuation bytes we've seen so far with * a single UTF-8 replacement character ('\ufffd'), to match v8's UTF-8 decoding * behavior. The continuation byte check is included three times in the case * where all of the continuation bytes for a character exist in the same buffer. * It is also done this way as a slight performance increase instead of using a * loop. * */function utf8CheckExtraBytes( self: StringDecoderBase, buf: Buffer,): string | undefined { if ((buf[0] & 0xc0) !== 0x80) { self.lastNeed = 0; return "\ufffd"; } if (self.lastNeed > 1 && buf.length > 1) { if ((buf[1] & 0xc0) !== 0x80) { self.lastNeed = 1; return "\ufffd"; } if (self.lastNeed > 2 && buf.length > 2) { if ((buf[2] & 0xc0) !== 0x80) { self.lastNeed = 2; return "\ufffd"; } } }}
/* * Attempts to complete a multi-byte UTF-8 character using bytes from a Buffer. * */function utf8FillLastComplete( this: StringDecoderBase, buf: Buffer,): string | undefined { const p = this.lastTotal - this.lastNeed; const r = utf8CheckExtraBytes(this, buf); if (r !== undefined) return r; if (this.lastNeed <= buf.length) { buf.copy(this.lastChar, p, 0, this.lastNeed); return this.lastChar.toString(this.encoding, 0, this.lastTotal); } buf.copy(this.lastChar, p, 0, buf.length); this.lastNeed -= buf.length;}
/* * Attempts to complete a partial non-UTF-8 character using bytes from a Buffer * */function utf8FillLastIncomplete( this: StringDecoderBase, buf: Buffer,): string | undefined { if (this.lastNeed <= buf.length) { buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, this.lastNeed); return this.lastChar.toString(this.encoding, 0, this.lastTotal); } buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, buf.length); this.lastNeed -= buf.length;}
/* * Returns all complete UTF-8 characters in a Buffer. If the Buffer ended on a * partial character, the character's bytes are buffered until the required * number of bytes are available. * */function utf8Text(this: StringDecoderBase, buf: Buffer, i: number): string { const total = utf8CheckIncomplete(this, buf, i); if (!this.lastNeed) return buf.toString("utf8", i); this.lastTotal = total; const end = buf.length - (total - this.lastNeed); buf.copy(this.lastChar, 0, end); return buf.toString("utf8", i, end);}
/* * For UTF-8, a replacement character is added when ending on a partial * character. * */function utf8End(this: Utf8Decoder, buf?: Buffer): string { const r = buf && buf.length ? this.write(buf) : ""; if (this.lastNeed) return r + "\ufffd"; return r;}
function utf8Write( this: Utf8Decoder | Base64Decoder, buf: Buffer | string,): string { if (typeof buf === "string") { return buf; } if (buf.length === 0) return ""; let r; let i; // Because `TypedArray` is recognized as `ArrayBuffer` but in the reality, there are some fundamental difference. We would need to cast it properly const normalizedBuffer: Buffer = isBufferType(buf) ? buf : Buffer.from(buf); if (this.lastNeed) { r = this.fillLast(normalizedBuffer); if (r === undefined) return ""; i = this.lastNeed; this.lastNeed = 0; } else { i = 0; } if (i < buf.length) { return r ? r + this.text(normalizedBuffer, i) : this.text(normalizedBuffer, i); } return r || "";}
function base64Text(this: StringDecoderBase, buf: Buffer, i: number): string { const n = (buf.length - i) % 3; if (n === 0) return buf.toString("base64", i); this.lastNeed = 3 - n; this.lastTotal = 3; if (n === 1) { this.lastChar[0] = buf[buf.length - 1]; } else { this.lastChar[0] = buf[buf.length - 2]; this.lastChar[1] = buf[buf.length - 1]; } return buf.toString("base64", i, buf.length - n);}
function base64End(this: Base64Decoder, buf?: Buffer): string { const r = buf && buf.length ? this.write(buf) : ""; if (this.lastNeed) { return r + this.lastChar.toString("base64", 0, 3 - this.lastNeed); } return r;}
function simpleWrite( this: StringDecoderBase, buf: Buffer | string,): string { if (typeof buf === "string") { return buf; } return buf.toString(this.encoding);}
function simpleEnd(this: GenericDecoder, buf?: Buffer): string { return buf && buf.length ? this.write(buf) : "";}
class StringDecoderBase { public lastChar: Buffer; public lastNeed = 0; public lastTotal = 0; constructor(public encoding: string, nb: number) { this.lastChar = Buffer.allocUnsafe(nb); }}
class Base64Decoder extends StringDecoderBase { public end = base64End; public fillLast = utf8FillLastIncomplete; public text = base64Text; public write = utf8Write;
constructor(encoding?: string) { super(normalizeEncoding(encoding), 3); }}
class GenericDecoder extends StringDecoderBase { public end = simpleEnd; public fillLast = undefined; public text = utf8Text; public write = simpleWrite;
constructor(encoding?: string) { super(normalizeEncoding(encoding), 4); }}
class Utf8Decoder extends StringDecoderBase { public end = utf8End; public fillLast = utf8FillLastComplete; public text = utf8Text; public write = utf8Write;
constructor(encoding?: string) { super(normalizeEncoding(encoding), 4); }}
/* * StringDecoder provides an interface for efficiently splitting a series of * buffers into a series of JS strings without breaking apart multi-byte * characters. * */export class StringDecoder { public encoding: string; public end: (buf?: Buffer) => string; public fillLast: ((buf: Buffer) => string | undefined) | undefined; public lastChar: Buffer; public lastNeed: number; public lastTotal: number; public text: (buf: Buffer, n: number) => string; public write: (buf: Buffer) => string;
constructor(encoding?: string) { const normalizedEncoding = normalizeEncoding(encoding); let decoder: Utf8Decoder | Base64Decoder | GenericDecoder; switch (normalizedEncoding) { case "utf8": decoder = new Utf8Decoder(encoding); break; case "base64": decoder = new Base64Decoder(encoding); break; default: decoder = new GenericDecoder(encoding); } this.encoding = decoder.encoding; this.end = decoder.end; this.fillLast = decoder.fillLast; this.lastChar = decoder.lastChar; this.lastNeed = decoder.lastNeed; this.lastTotal = decoder.lastTotal; this.text = decoder.text; this.write = decoder.write; }}// Allow calling StringDecoder() without newconst PStringDecoder = new Proxy(StringDecoder, { apply(_target, thisArg, args) { // @ts-ignore tedious to replicate types ... return Object.assign(thisArg, new StringDecoder(...args)); },});
export default { StringDecoder: PStringDecoder };
std
Version Info
a year ago
