Function relative

src/platform/vscode-path/path.ts:523–639

(from: string, to: string)

    //  to = 'C:\\orandea\\impl\\bbb'
    // The output of the function should be: '..\\..\\impl\\bbb'
    relative(from: string, to: string): string {
        validateString(from, 'from');
        validateString(to, 'to');

        if (from === to) {
            return '';
        }

        const fromOrig = win32.resolve(from);
        const toOrig = win32.resolve(to);

        if (fromOrig === toOrig) {
            return '';
        }

        from = fromOrig.toLowerCase();
        to = toOrig.toLowerCase();

        if (from === to) {
            return '';
        }

        // Trim any leading backslashes
        let fromStart = 0;
        while (fromStart < from.length && from.charCodeAt(fromStart) === CHAR_BACKWARD_SLASH) {
            fromStart++;
        }
        // Trim trailing backslashes (applicable to UNC paths only)
        let fromEnd = from.length;
        while (fromEnd - 1 > fromStart && from.charCodeAt(fromEnd - 1) === CHAR_BACKWARD_SLASH) {
            fromEnd--;
        }
        const fromLen = fromEnd - fromStart;

        // Trim any leading backslashes
        let toStart = 0;
        while (toStart < to.length && to.charCodeAt(toStart) === CHAR_BACKWARD_SLASH) {
            toStart++;
        }
        // Trim trailing backslashes (applicable to UNC paths only)
        let toEnd = to.length;
        while (toEnd - 1 > toStart && to.charCodeAt(toEnd - 1) === CHAR_BACKWARD_SLASH) {
            toEnd--;
        }
        const toLen = toEnd - toStart;

        // Compare paths to find the longest common path from root
        const length = fromLen < toLen ? fromLen : toLen;
        let lastCommonSep = -1;
        let i = 0;
        for (; i < length; i++) {
            const fromCode = from.charCodeAt(fromStart + i);
            if (fromCode !== to.charCodeAt(toStart + i)) {
                break;
            } else if (fromCode === CHAR_BACKWARD_SLASH) {
                lastCommonSep = i;
            }
        }