\n * These objects are the currency accepted by SJCL's crypto functions.\n *
\n *\n *\n * Most of our crypto primitives operate on arrays of 4-byte words internally,\n * but many of them can take arguments that are not a multiple of 4 bytes.\n * This library encodes arrays of bits (whose size need not be a multiple of 8\n * bits) as arrays of 32-bit words. The bits are packed, big-endian, into an\n * array of words, 32 bits at a time. Since the words are double-precision\n * floating point numbers, they fit some extra data. We use this (in a private,\n * possibly-changing manner) to encode the number of bits actually present\n * in the last word of the array.\n *
\n *\n *\n * Because bitwise ops clear this out-of-band data, these arrays can be passed\n * to ciphers like AES which want arrays of words.\n *
\n */\nsjcl.bitArray = {\n /**\n * Array slices in units of bits.\n * @param {bitArray} a The array to slice.\n * @param {Number} bstart The offset to the start of the slice, in bits.\n * @param {Number} bend The offset to the end of the slice, in bits. If this is undefined,\n * slice until the end of the array.\n * @return {bitArray} The requested slice.\n */\n bitSlice: function (a, bstart, bend) {\n a = sjcl.bitArray._shiftRight(a.slice(bstart/32), 32 - (bstart & 31)).slice(1);\n return (bend === undefined) ? a : sjcl.bitArray.clamp(a, bend-bstart);\n },\n\n /**\n * Extract a number packed into a bit array.\n * @param {bitArray} a The array to slice.\n * @param {Number} bstart The offset to the start of the slice, in bits.\n * @param {Number} blength The length of the number to extract.\n * @return {Number} The requested slice.\n */\n extract: function(a, bstart, blength) {\n // FIXME: this Math.floor is not necessary at all, but for some reason\n // seems to suppress a bug in the Chromium JIT.\n var x, sh = Math.floor((-bstart-blength) & 31);\n if ((bstart + blength - 1 ^ bstart) & -32) {\n // it crosses a boundary\n x = (a[bstart/32|0] << (32 - sh)) ^ (a[bstart/32+1|0] >>> sh);\n } else {\n // within a single word\n x = a[bstart/32|0] >>> sh;\n }\n return x & ((1<