TypeScript strings.startsWithUTF8BOM函数代码示例

	public static toRawText(rawText:string): editorCommon.IRawText {
		// Count the number of lines that end with \r\n
		var carriageReturnCnt = 0,
			lastCarriageReturnIndex = -1;
		while ((lastCarriageReturnIndex = rawText.indexOf('\r', lastCarriageReturnIndex + 1)) !== -1) {
			carriageReturnCnt++;
		}

		// Split the text into liens
		var lines = rawText.split(/\r\n|\r|\n/);

		// Remove the BOM (if present)
		var BOM = '';
		if (strings.startsWithUTF8BOM(lines[0])) {
			BOM = strings.UTF8_BOM_CHARACTER;
			lines[0] = lines[0].substr(1);
		}

		var lineFeedCnt = lines.length - 1;
		var EOL = '';
		if (lineFeedCnt === 0) {
			// This is an empty file or a file with precisely one line
			EOL = DEFAULT_PLATFORM_EOL;
		} else if (carriageReturnCnt > lineFeedCnt / 2) {
			// More than half of the file contains \r\n ending lines
			EOL = '\r\n';
		} else {
			// At least one line more ends in \n
			EOL = '\n';
		}

		return {
			BOM: BOM,
			EOL: EOL,
			lines: lines,
			length: rawText.length
		};
	}

	public acceptChunk(chunk: string): void {
		if (chunk.length === 0) {
			return;
		}

		if (this.chunks.length === 0) {
			if (strings.startsWithUTF8BOM(chunk)) {
				this.BOM = strings.UTF8_BOM_CHARACTER;
				chunk = chunk.substr(1);
			}
		}

		const lastChar = chunk.charCodeAt(chunk.length - 1);
		if (lastChar === CharCode.CarriageReturn || (lastChar >= 0xD800 && lastChar <= 0xDBFF)) {
			// last character is \r or a high surrogate => keep it back
			this._acceptChunk1(chunk.substr(0, chunk.length - 1), false);
			this._hasPreviousChar = true;
			this._previousChar = lastChar;
		} else {
			this._acceptChunk1(chunk, false);
			this._hasPreviousChar = false;
			this._previousChar = lastChar;
		}
	}

function guessMimeTypeByFirstline(firstLine: string): string | null {
	if (startsWithUTF8BOM(firstLine)) {
		firstLine = firstLine.substr(1);
	}

	if (firstLine.length > 0) {

		// We want to prioritize associations based on the order they are registered so that the last registered
		// association wins over all other. This is for https://github.com/Microsoft/vscode/issues/20074
		for (let i = registeredAssociations.length - 1; i >= 0; i--) {
			const association = registeredAssociations[i];
			if (!association.firstline) {
				continue;
			}

			const matches = firstLine.match(association.firstline);
			if (matches && matches.length > 0) {
				return association.mime;
			}
		}
	}

	return null;
}

	public static colorize(modeService: IModeService, text: string, mimeType: string, options: IColorizerOptions | null | undefined): Promise<string> {
		let tabSize = 4;
		if (options && typeof options.tabSize === 'number') {
			tabSize = options.tabSize;
		}

		if (strings.startsWithUTF8BOM(text)) {
			text = text.substr(1);
		}
		let lines = text.split(/\r\n|\r|\n/);
		let language = modeService.getModeId(mimeType);
		if (!language) {
			return Promise.resolve(_fakeColorize(lines, tabSize));
		}

		// Send out the event to create the mode
		modeService.triggerMode(language);

		const tokenizationSupport = TokenizationRegistry.get(language);
		if (tokenizationSupport) {
			return _colorize(lines, tabSize, tokenizationSupport);
		}

		const tokenizationSupportPromise = TokenizationRegistry.getPromise(language);
		if (tokenizationSupportPromise) {
			// A tokenizer will be registered soon
			return new Promise<string>((resolve, reject) => {
				tokenizationSupportPromise.then(tokenizationSupport => {
					_colorize(lines, tabSize, tokenizationSupport).then(resolve, reject);
				}, reject);
			});
		}

		return new Promise<string>((resolve, reject) => {
			let listener: IDisposable | null = null;
			let timeout: TimeoutTimer | null = null;

			const execute = () => {
				if (listener) {
					listener.dispose();
					listener = null;
				}
				if (timeout) {
					timeout.dispose();
					timeout = null;
				}
				const tokenizationSupport = TokenizationRegistry.get(language!);
				if (tokenizationSupport) {
					_colorize(lines, tabSize, tokenizationSupport).then(resolve, reject);
					return;
				}
				resolve(_fakeColorize(lines, tabSize));
			};

			// wait 500ms for mode to load, then give up
			timeout = new TimeoutTimer();
			timeout.cancelAndSet(execute, 500);
			listener = TokenizationRegistry.onDidChange((e) => {
				if (e.changedLanguages.indexOf(language!) >= 0) {
					execute();
				}
			});
		});
	}