array.js

'use strict';

var isArray = Array.isArray;

var ab = ArrayBuffer;
var dv = DataView;

function isTypedArray(a) {
    return ab.isView(a) && !(a instanceof dv);
}
exports.isTypedArray = isTypedArray;

function isArrayOrTypedArray(a) {
    return isArray(a) || isTypedArray(a);
}
exports.isArrayOrTypedArray = isArrayOrTypedArray;

/*
 * Test whether an input object is 1D.
 *
 * Assumes we already know the object is an array.
 *
 * Looks only at the first element, if the dimensionality is
 * not consistent we won't figure that out here.
 */
function isArray1D(a) {
    return !isArrayOrTypedArray(a[0]);
}
exports.isArray1D = isArray1D;

/*
 * Ensures an array has the right amount of storage space. If it doesn't
 * exist, it creates an array. If it does exist, it returns it if too
 * short or truncates it in-place.
 *
 * The goal is to just reuse memory to avoid a bit of excessive garbage
 * collection.
 */
exports.ensureArray = function(out, n) {
    // TODO: typed array support here? This is only used in
    // traces/carpet/compute_control_points
    if(!isArray(out)) out = [];

    // If too long, truncate. (If too short, it will grow
    // automatically so we don't care about that case)
    out.length = n;

    return out;
};

/*
 * TypedArray-compatible concatenation of n arrays
 * if all arrays are the same type it will preserve that type,
 * otherwise it falls back on Array.
 * Also tries to avoid copying, in case one array has zero length
 * But never mutates an existing array
 */
exports.concat = function() {
    var args = [];
    var allArray = true;
    var totalLen = 0;

    var _constructor, arg0, i, argi, posi, leni, out, j;

    for(i = 0; i < arguments.length; i++) {
        argi = arguments[i];
        leni = argi.length;
        if(leni) {
            if(arg0) args.push(argi);
            else {
                arg0 = argi;
                posi = leni;
            }

            if(isArray(argi)) {
                _constructor = false;
            } else {
                allArray = false;
                if(!totalLen) {
                    _constructor = argi.constructor;
                } else if(_constructor !== argi.constructor) {
                    // TODO: in principle we could upgrade here,
                    // ie keep typed array but convert all to Float64Array?
                    _constructor = false;
                }
            }

            totalLen += leni;
        }
    }

    if(!totalLen) return [];
    if(!args.length) return arg0;

    if(allArray) return arg0.concat.apply(arg0, args);
    if(_constructor) {
        // matching typed arrays
        out = new _constructor(totalLen);
        out.set(arg0);
        for(i = 0; i < args.length; i++) {
            argi = args[i];
            out.set(argi, posi);
            posi += argi.length;
        }
        return out;
    }

    // mismatched types or Array + typed
    out = new Array(totalLen);
    for(j = 0; j < arg0.length; j++) out[j] = arg0[j];
    for(i = 0; i < args.length; i++) {
        argi = args[i];
        for(j = 0; j < argi.length; j++) out[posi + j] = argi[j];
        posi += j;
    }
    return out;
};

exports.maxRowLength = function(z) {
    return _rowLength(z, Math.max, 0);
};

exports.minRowLength = function(z) {
    return _rowLength(z, Math.min, Infinity);
};

function _rowLength(z, fn, len0) {
    if(isArrayOrTypedArray(z)) {
        if(isArrayOrTypedArray(z[0])) {
            var len = len0;
            for(var i = 0; i < z.length; i++) {
                len = fn(len, z[i].length);
            }
            return len;
        } else {
            return z.length;
        }
    }
    return 0;
}