Function bidirectionalIndexOf

docs/app/js/sanddance-app.js:113293–113334

(buffer, val, byteOffset, encoding, dir)

// - encoding - an optional encoding, relevant is val is a string
// - dir - true for indexOf, false for lastIndexOf
function bidirectionalIndexOf(buffer, val, byteOffset, encoding, dir) {
    // Empty buffer means no match
    if (buffer.length === 0) return -1;
    // Normalize byteOffset
    if (typeof byteOffset === "string") {
        encoding = byteOffset;
        byteOffset = 0;
    } else if (byteOffset > 0x7fffffff) byteOffset = 0x7fffffff;
    else if (byteOffset < -2147483648) byteOffset = -2147483648;
    byteOffset = +byteOffset // Coerce to Number.
    ;
    if (numberIsNaN(byteOffset)) // byteOffset: it it's undefined, null, NaN, "foo", etc, search whole buffer
    byteOffset = dir ? 0 : buffer.length - 1;
    // Normalize byteOffset: negative offsets start from the end of the buffer
    if (byteOffset < 0) byteOffset = buffer.length + byteOffset;
    if (byteOffset >= buffer.length) {
        if (dir) return -1;
        else byteOffset = buffer.length - 1;
    } else if (byteOffset < 0) {
        if (dir) byteOffset = 0;
        else return -1;
    }
    // Normalize val
    if (typeof val === "string") val = Buffer.from(val, encoding);
    // Finally, search either indexOf (if dir is true) or lastIndexOf
    if (Buffer.isBuffer(val)) {
        // Special case: looking for empty string/buffer always fails
        if (val.length === 0) return -1;
        return arrayIndexOf(buffer, val, byteOffset, encoding, dir);
    } else if (typeof val === "number") {
        val = val & 0xFF // Search for a byte value [0-255]
        ;
        if (typeof Uint8Array.prototype.indexOf === "function") {
            if (dir) return Uint8Array.prototype.indexOf.call(buffer, val, byteOffset);
            else return Uint8Array.prototype.lastIndexOf.call(buffer, val, byteOffset);
        }
        return arrayIndexOf(buffer, [
            val
        ], byteOffset, encoding, dir);
    }
    throw new TypeError("val must be string, number or Buffer");
}
function arrayIndexOf(arr, val, byteOffset, encoding, dir) {
    var indexSize = 1;
    var arrLength = arr.length;