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Unified Diff: runtime/lib/bigint.dart

Issue 1044503002: Refactor bigint shifting code in preparation of shifting intrinsics. (Closed) Base URL: http://dart.googlecode.com/svn/branches/bleeding_edge/dart/
Patch Set: Created 5 years, 9 months ago
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Index: runtime/lib/bigint.dart
===================================================================
--- runtime/lib/bigint.dart (revision 44750)
+++ runtime/lib/bigint.dart (working copy)
@@ -171,13 +171,13 @@
// Return this << n*_DIGIT_BITS.
_Bigint _dlShift(int n) {
- var used = _used;
+ final used = _used;
if (used == 0) {
return _ZERO;
}
- var r_used = used + n;
- var digits = _digits;
- var r_digits = new Uint32List(r_used + (r_used & 1));
+ final r_used = used + n;
+ final digits = _digits;
+ final r_digits = new Uint32List(r_used + (r_used & 1));
var i = used;
while (--i >= 0) {
r_digits[i + n] = digits[i];
@@ -195,7 +195,7 @@
if (n == 0 && r_digits == x_digits) {
return x_used;
}
- var r_used = x_used + n;
+ final r_used = x_used + n;
assert(r_digits.length >= r_used + (r_used & 1));
var i = x_used;
while (--i >= 0) {
@@ -213,20 +213,20 @@
// Return this >> n*_DIGIT_BITS.
_Bigint _drShift(int n) {
- var used = _used;
+ final used = _used;
if (used == 0) {
return _ZERO;
}
- var r_used = used - n;
+ final r_used = used - n;
if (r_used <= 0) {
return _neg ? _MINUS_ONE : _ZERO;
}
- var digits = _digits;
- var r_digits = new Uint32List(r_used + (r_used & 1));
+ final digits = _digits;
+ final r_digits = new Uint32List(r_used + (r_used & 1));
for (var i = n; i < used; i++) {
r_digits[i - n] = digits[i];
}
- var r = new _Bigint(_neg, r_used, r_digits);
+ final r = new _Bigint(_neg, r_used, r_digits);
if (_neg) {
// Round down if any bit was shifted out.
for (var i = 0; i < n; i++) {
@@ -242,7 +242,7 @@
// Return r_used.
static int _drShiftDigits(Uint32List x_digits, int x_used, int n,
Uint32List r_digits) {
- var r_used = x_used - n;
+ final r_used = x_used - n;
if (r_used <= 0) {
return 0;
}
@@ -256,26 +256,37 @@
return r_used;
}
+ // r_digits[0..r_used-1] = x_digits[0..x_used-1] << n.
+ static void _lsh(Uint32List x_digits, int x_used, int n,
+ Uint32List r_digits) {
+ final ds = n ~/ _DIGIT_BITS;
+ final bs = n % _DIGIT_BITS;
+ final cbs = _DIGIT_BITS - bs;
+ final bm = (1 << cbs) - 1;
+ var c = 0;
+ var i = x_used;
+ while (--i >= 0) {
+ final d = x_digits[i];
+ r_digits[i + ds + 1] = (d >> cbs) | c;
+ c = (d & bm) << bs;
+ }
+ r_digits[ds] = c;
+ i = ds;
+ while (--i >= 0) {
+ r_digits[i] = 0;
+ }
+ }
+
// Return this << n.
_Bigint _lShift(int n) {
- var ds = n ~/ _DIGIT_BITS;
- var bs = n % _DIGIT_BITS;
+ final ds = n ~/ _DIGIT_BITS;
+ final bs = n % _DIGIT_BITS;
if (bs == 0) {
return _dlShift(ds);
}
- var cbs = _DIGIT_BITS - bs;
- var bm = (1 << cbs) - 1;
var r_used = _used + ds + 1;
- var digits = _digits;
var r_digits = new Uint32List(r_used + (r_used & 1));
- var c = 0;
- var i = _used;
- while (--i >= 0) {
- final d = digits[i];
- r_digits[i + ds + 1] = (d >> cbs) | c;
- c = (d & bm) << bs;
- }
- r_digits[ds] = c;
+ _lsh(_digits, _used, n, r_digits);
return new _Bigint(_neg, r_used, r_digits);
}
@@ -283,27 +294,14 @@
// Return r_used.
static int _lShiftDigits(Uint32List x_digits, int x_used, int n,
Uint32List r_digits) {
- var ds = n ~/ _DIGIT_BITS;
- var bs = n % _DIGIT_BITS;
+ final ds = n ~/ _DIGIT_BITS;
+ final bs = n % _DIGIT_BITS;
if (bs == 0) {
return _dlShiftDigits(x_digits, x_used, ds, r_digits);
}
- var cbs = _DIGIT_BITS - bs;
- var bm = (1 << cbs) - 1;
var r_used = x_used + ds + 1;
assert(r_digits.length >= r_used + (r_used & 1));
- var c = 0;
- var i = x_used;
- while (--i >= 0) {
- final d = x_digits[i];
- r_digits[i + ds + 1] = (d >> cbs) | c;
- c = (d & bm) << bs;
- }
- r_digits[ds] = c;
- i = ds;
- while (--i >= 0) {
- r_digits[i] = 0;
- }
+ _lsh(x_digits, x_used, n, r_digits);
if (r_digits[r_used - 1] == 0) {
r_used--; // Clamp result.
} else if (r_used.isOdd) {
@@ -312,32 +310,42 @@
return r_used;
}
+ // r_digits[0..r_used-1] = x_digits[0..x_used-1] >> n.
+ static void _rsh(Uint32List x_digits, int x_used, int n,
+ Uint32List r_digits) {
+ final ds = n ~/ _DIGIT_BITS;
+ final bs = n % _DIGIT_BITS;
+ final cbs = _DIGIT_BITS - bs;
+ final bm = (1 << bs) - 1;
+ var c = x_digits[ds] >> bs;
+ final last = x_used - ds - 1;
+ for (var i = 0; i < last; i++) {
+ final d = x_digits[i + ds + 1];
+ r_digits[i] = ((d & bm) << cbs) | c;
+ c = d >> bs;
+ }
+ r_digits[last] = c;
+ }
+
// Return this >> n.
_Bigint _rShift(int n) {
- var ds = n ~/ _DIGIT_BITS;
- var bs = n % _DIGIT_BITS;
+ final ds = n ~/ _DIGIT_BITS;
+ final bs = n % _DIGIT_BITS;
if (bs == 0) {
return _drShift(ds);
}
- var r_used = _used - ds;
+ final used = _used;
+ final r_used = used - ds;
if (r_used <= 0) {
return _neg ? _MINUS_ONE : _ZERO;
}
- var cbs = _DIGIT_BITS - bs;
- var bm = (1 << bs) - 1;
- var digits = _digits;
- var r_digits = new Uint32List(r_used + (r_used & 1));
- r_digits[0] = digits[ds] >> bs;
- var used = _used;
- for (var i = ds + 1; i < used; i++) {
- final d = digits[i];
- r_digits[i - ds - 1] |= (d & bm) << cbs;
- r_digits[i - ds] = d >> bs;
- }
- var r = new _Bigint(_neg, r_used, r_digits);
+ final digits = _digits;
+ final r_digits = new Uint32List(r_used + (r_used & 1));
+ _rsh(digits, used, n, r_digits);
+ final r = new _Bigint(_neg, r_used, r_digits);
if (_neg) {
// Round down if any bit was shifted out.
- if ((digits[ds] & bm) != 0) {
+ if ((digits[ds] & ((1 << bs) - 1)) != 0) {
return r._sub(_ONE);
}
for (var i = 0; i < ds; i++) {
@@ -353,8 +361,8 @@
// Return r_used.
static int _rShiftDigits(Uint32List x_digits, int x_used, int n,
Uint32List r_digits) {
- var ds = n ~/ _DIGIT_BITS;
- var bs = n % _DIGIT_BITS;
+ final ds = n ~/ _DIGIT_BITS;
+ final bs = n % _DIGIT_BITS;
if (bs == 0) {
return _drShiftDigits(x_digits, x_used, ds, r_digits);
}
@@ -362,15 +370,8 @@
if (r_used <= 0) {
return 0;
}
- var cbs = _DIGIT_BITS - bs;
- var bm = (1 << bs) - 1;
assert(r_digits.length >= r_used + (r_used & 1));
- r_digits[0] = x_digits[ds] >> bs;
- for (var i = ds + 1; i < x_used; i++) {
- final d = x_digits[i];
- r_digits[i - ds - 1] |= (d & bm) << cbs;
- r_digits[i - ds] = d >> bs;
- }
+ _rsh(x_digits, x_used, n, r_digits);
if (r_digits[r_used - 1] == 0) {
r_used--; // Clamp result.
} else if (r_used.isOdd) {
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