/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* ***** BEGIN LICENSE BLOCK ***** * Version: MPL 1.1/GPL 2.0/LGPL 2.1 * * The contents of this file are subject to the Mozilla Public License Version * 1.1 (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * http://www.mozilla.org/MPL/ * * Software distributed under the License is distributed on an "AS IS" basis, * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License * for the specific language governing rights and limitations under the * License. * * The Original Code is Mozilla Communicator client code, released * March 31, 1998. * * The Initial Developer of the Original Code is * Netscape Communications Corporation. * Portions created by the Initial Developer are Copyright (C) 1998 * the Initial Developer. All Rights Reserved. * * Contributor(s): * * Alternatively, the contents of this file may be used under the terms of * either of the GNU General Public License Version 2 or later (the "GPL"), * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), * in which case the provisions of the GPL or the LGPL are applicable instead * of those above. If you wish to allow use of your version of this file only * under the terms of either the GPL or the LGPL, and not to allow others to * use your version of this file under the terms of the MPL, indicate your * decision by deleting the provisions above and replace them with the notice * and other provisions required by the GPL or the LGPL. If you do not delete * the provisions above, a recipient may use your version of this file under * the terms of any one of the MPL, the GPL or the LGPL. * * ***** END LICENSE BLOCK ***** */ #include "jsstddef.h" #include "jstypes.h" #include "jslong.h" #ifndef JS_HAVE_LONG_LONG /* ** Divide 64-bit a by 32-bit b, which must be normalized so its high bit is 1. */ static void norm_udivmod32(JSUint32 *qp, JSUint32 *rp, JSUint64 a, JSUint32 b) { JSUint32 d1, d0, q1, q0; JSUint32 r1, r0, m; d1 = jshi16(b); d0 = jslo16(b); r1 = a.hi % d1; q1 = a.hi / d1; m = q1 * d0; r1 = (r1 << 16) | jshi16(a.lo); if (r1 < m) { q1--, r1 += b; if (r1 >= b /* i.e., we didn't get a carry when adding to r1 */ && r1 < m) { q1--, r1 += b; } } r1 -= m; r0 = r1 % d1; q0 = r1 / d1; m = q0 * d0; r0 = (r0 << 16) | jslo16(a.lo); if (r0 < m) { q0--, r0 += b; if (r0 >= b && r0 < m) { q0--, r0 += b; } } *qp = (q1 << 16) | q0; *rp = r0 - m; } static JSUint32 CountLeadingZeros(JSUint32 a) { JSUint32 t; JSUint32 r = 32; if ((t = a >> 16) != 0) r -= 16, a = t; if ((t = a >> 8) != 0) r -= 8, a = t; if ((t = a >> 4) != 0) r -= 4, a = t; if ((t = a >> 2) != 0) r -= 2, a = t; if ((t = a >> 1) != 0) r -= 1, a = t; if (a & 1) r--; return r; } JS_PUBLIC_API(void) jsll_udivmod(JSUint64 *qp, JSUint64 *rp, JSUint64 a, JSUint64 b) { JSUint32 n0, n1, n2; JSUint32 q0, q1; JSUint32 rsh, lsh; n0 = a.lo; n1 = a.hi; if (b.hi == 0) { if (b.lo > n1) { /* (0 q0) = (n1 n0) / (0 D0) */ lsh = CountLeadingZeros(b.lo); if (lsh) { /* * Normalize, i.e. make the most significant bit of the * denominator be set. */ b.lo = b.lo << lsh; n1 = (n1 << lsh) | (n0 >> (32 - lsh)); n0 = n0 << lsh; } a.lo = n0, a.hi = n1; norm_udivmod32(&q0, &n0, a, b.lo); q1 = 0; /* remainder is in n0 >> lsh */ } else { /* (q1 q0) = (n1 n0) / (0 d0) */ if (b.lo == 0) /* user wants to divide by zero! */ b.lo = 1 / b.lo; /* so go ahead and crash */ lsh = CountLeadingZeros(b.lo); if (lsh == 0) { /* * From (n1 >= b.lo) * && (the most significant bit of b.lo is set), * conclude that * (the most significant bit of n1 is set) * && (the leading quotient digit q1 = 1). * * This special case is necessary, not an optimization * (Shifts counts of 32 are undefined). */ n1 -= b.lo; q1 = 1; } else { /* * Normalize. */ rsh = 32 - lsh; b.lo = b.lo << lsh; n2 = n1 >> rsh; n1 = (n1 << lsh) | (n0 >> rsh); n0 = n0 << lsh; a.lo = n1, a.hi = n2; norm_udivmod32(&q1, &n1, a, b.lo); } /* n1 != b.lo... */ a.lo = n0, a.hi = n1; norm_udivmod32(&q0, &n0, a, b.lo); /* remainder in n0 >> lsh */ } if (rp) { rp->lo = n0 >> lsh; rp->hi = 0; } } else { if (b.hi > n1) { /* (0 0) = (n1 n0) / (D1 d0) */ q0 = 0; q1 = 0; /* remainder in (n1 n0) */ if (rp) { rp->lo = n0; rp->hi = n1; } } else { /* (0 q0) = (n1 n0) / (d1 d0) */ lsh = CountLeadingZeros(b.hi); if (lsh == 0) { /* * From (n1 >= b.hi) * && (the most significant bit of b.hi is set), * conclude that * (the most significant bit of n1 is set) * && (the quotient digit q0 = 0 or 1). * * This special case is necessary, not an optimization. */ /* * The condition on the next line takes advantage of that * n1 >= b.hi (true due to control flow). */ if (n1 > b.hi || n0 >= b.lo) { q0 = 1; a.lo = n0, a.hi = n1; JSLL_SUB(a, a, b); } else { q0 = 0; } q1 = 0; if (rp) { rp->lo = n0; rp->hi = n1; } } else { JSInt64 m; /* * Normalize. */ rsh = 32 - lsh; b.hi = (b.hi << lsh) | (b.lo >> rsh); b.lo = b.lo << lsh; n2 = n1 >> rsh; n1 = (n1 << lsh) | (n0 >> rsh); n0 = n0 << lsh; a.lo = n1, a.hi = n2; norm_udivmod32(&q0, &n1, a, b.hi); JSLL_MUL32(m, q0, b.lo); if ((m.hi > n1) || ((m.hi == n1) && (m.lo > n0))) { q0--; JSLL_SUB(m, m, b); } q1 = 0; /* Remainder is ((n1 n0) - (m1 m0)) >> lsh */ if (rp) { a.lo = n0, a.hi = n1; JSLL_SUB(a, a, m); rp->lo = (a.hi << rsh) | (a.lo >> lsh); rp->hi = a.hi >> lsh; } } } } if (qp) { qp->lo = q0; qp->hi = q1; } } #endif /* !JS_HAVE_LONG_LONG */