The Tor Browser: nsprpub/pr/src/misc/prlong.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/prlong.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/prlong.c

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "prlong.h"
 static PRInt64 ll_zero = LL_INIT( 0x00000000,0x00000000 );
 static PRInt64 ll_maxint = LL_INIT( 0x7fffffff, 0xffffffff );
 static PRInt64 ll_minint = LL_INIT( 0x80000000, 0x00000000 );
 static PRUint64 ll_maxuint = LL_INIT( 0xffffffff, 0xffffffff );
 PR_IMPLEMENT(PRInt64) LL_Zero(void) { return ll_zero; }
 PR_IMPLEMENT(PRInt64) LL_MaxInt(void) { return ll_maxint; }
 PR_IMPLEMENT(PRInt64) LL_MinInt(void) { return ll_minint; }
 PR_IMPLEMENT(PRUint64) LL_MaxUint(void) { return ll_maxuint; }
 #ifndef 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(PRUint32 *qp, PRUint32 *rp, PRUint64 a, PRUint32 b)
 {
     PRUint32 d1, d0, q1, q0;
     PRUint32 r1, r0, m;
     d1 = _hi16(b);
     d0 = _lo16(b);
     r1 = a.hi % d1;
     q1 = a.hi / d1;
     m = q1 * d0;
     r1 = (r1 << 16) | _hi16(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) | _lo16(a.lo);
     if (r0 < m) {
         q0--, r0 += b;
         if (r0 >= b
 	    && r0 < m) {
 	    q0--, r0 += b;
 	}
     }
     *qp = (q1 << 16) | q0;
     *rp = r0 - m;
 }
 static PRUint32 CountLeadingZeros(PRUint32 a)
 {
     PRUint32 t;
     PRUint32 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;
 }
 PR_IMPLEMENT(void) ll_udivmod(PRUint64 *qp, PRUint64 *rp, PRUint64 a, PRUint64 b)
 {
     PRUint32 n0, n1, n2;
     PRUint32 q0, q1;
     PRUint32 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;
 		    LL_SUB(a, a, b);
 		} else {
 		    q0 = 0;
 		}
 		q1 = 0;
 		if (rp) {
 		    rp->lo = n0;
 		    rp->hi = n1;
 		}
 	    } else {
 		PRInt64 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);
 		LL_MUL32(m, q0, b.lo);
 		if ((m.hi > n1) || ((m.hi == n1) && (m.lo > n0))) {
 		    q0--;
 		    LL_SUB(m, m, b);
 		}
 		q1 = 0;
 		/* Remainder is ((n1 n0) - (m1 m0)) >> lsh */
 		if (rp) {
 		    a.lo = n0, a.hi = n1;
 		    LL_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 /* !HAVE_LONG_LONG */

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nsprpub/pr/src/misc/prlong.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/prlong.c