move math out of runtime.

a step toward enforcing package boundaries,
necessary to eliminate global package name space.

R=r
DELTA=581  (310 added, 271 deleted, 0 changed)
OCL=35805
CL=35823

src/pkg/math/Makefile

@@ -16,6 +16,7 @@ ALLGOFILES=\
 	asin.go\
 	atan.go\
 	atan2.go\
+	bits.go\
 	const.go\
 	exp.go\
 	fabs.go\
@@ -25,12 +26,12 @@ ALLGOFILES=\
 	log.go\
 	pow.go\
 	pow10.go\
-	runtime.go\
 	sin.go\
 	sinh.go\
 	sqrt.go\
 	tan.go\
 	tanh.go\
+	unsafe.go\
 
 NOGOFILES=\
 	$(subst _$(GOARCH).$O,.go,$(OFILES_$(GOARCH)))

src/pkg/math/bits.go

@@ -0,0 +1,105 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+const (
+	uvnan = 0x7FF0000000000001;
+	uvinf = 0x7FF0000000000000;
+	uvneginf = 0xFFF0000000000000;
+	mask = 0x7FF;
+	shift = 64 - 11 - 1;
+	bias = 1022;
+)
+
+// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
+func Inf(sign int) float64 {
+	var v uint64;
+	if sign >= 0 {
+		v = uvinf;
+	} else {
+		v = uvneginf;
+	}
+	return Float64frombits(v);
+}
+
+// NaN returns an IEEE 754 ``not-a-number'' value.
+func NaN() float64 {
+	return Float64frombits(uvnan);
+}
+
+// IsNaN returns whether f is an IEEE 754 ``not-a-number'' value.
+func IsNaN(f float64) (is bool) {
+	x := Float64bits(f);
+	return uint32(x>>shift) & mask == mask && x != uvinf && x != uvneginf;
+}
+
+// IsInf returns whether f is an infinity, according to sign.
+// If sign > 0, IsInf returns whether f is positive infinity.
+// If sign < 0, IsInf returns whether f is negative infinity.
+// If sign == 0, IsInf returns whether f is either infinity.
+func IsInf(f float64, sign int) bool {
+	x := Float64bits(f);
+	return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
+}
+
+// Frexp breaks f into a normalized fraction
+// and an integral power of two.
+// It returns frac and exp satisfying f == frac × 2<sup>exp</sup>,
+// with the absolute value of frac in the interval [½, 1).
+func Frexp(f float64) (frac float64, exp int) {
+	if f == 0 {
+		return;
+	}
+	x := Float64bits(f);
+	exp = int((x>>shift)&mask) - bias;
+	x &^= mask<<shift;
+	x |= bias<<shift;
+	frac = Float64frombits(x);
+	return;
+}
+
+// Ldexp is the inverse of Frexp.
+// It returns frac × 2<sup>exp</sup>.
+func Ldexp(frac float64, exp int) float64 {
+	x := Float64bits(frac);
+	exp += int(x>>shift) & mask;
+	if exp <= 0 {
+		return 0;	// underflow
+	}
+	if exp >= mask {	// overflow
+		if frac < 0 {
+			return Inf(-1);
+		}
+		return Inf(1);
+	}
+	x &^= mask<<shift;
+	x |= uint64(exp)<<shift;
+	return Float64frombits(x);
+}
+
+// Modf returns integer and fractional floating-point numbers
+// that sum to f.
+// Integer and frac have the same sign as f.
+func Modf(f float64) (int float64, frac float64) {
+	if f < 1 {
+		if f < 0 {
+			int, frac = Modf(-f);
+			return -int, -frac;
+		}
+		return 0, f;
+	}
+
+	x := Float64bits(f);
+	e := uint(x>>shift)&mask - bias;
+
+	// Keep the top 11+e bits, the integer part; clear the rest.
+	if e < 64-11 {
+		x &^= 1<<(64-11-e) - 1;
+	}
+	int = Float64frombits(x);
+	frac = f - int;
+	return;
+}
+

src/pkg/math/runtime.go

@@ -1,52 +0,0 @@
-// Copyright 2009 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package math
-
-// implemented in C, in ../../runtime
-// perhaps one day the implementations will move here.
-
-// Float32bits returns the IEEE 754 binary representation of f.
-func Float32bits(f float32) (b uint32)
-
-// Float32frombits returns the floating point number corresponding
-// to the IEEE 754 binary representation b.
-func Float32frombits(b uint32) (f float32)
-
-// Float64bits returns the IEEE 754 binary representation of f.
-func Float64bits(f float64) (b uint64)
-
-// Float64frombits returns the floating point number corresponding
-// the IEEE 754 binary representation b.
-func Float64frombits(b uint64) (f float64)
-
-// Frexp breaks f into a normalized fraction
-// and an integral power of two.
-// It returns frac and exp satisfying f == frac × 2<sup>exp</sup>,
-// with the absolute value of frac in the interval [½, 1).
-func Frexp(f float64) (frac float64, exp int)
-
-// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
-func Inf(sign int32) (f float64)
-
-// IsInf returns whether f is an infinity, according to sign.
-// If sign > 0, IsInf returns whether f is positive infinity.
-// If sign < 0, IsInf returns whether f is negative infinity.
-// If sign == 0, IsInf returns whether f is either infinity.
-func IsInf(f float64, sign int) (is bool)
-
-// IsNaN returns whether f is an IEEE 754 ``not-a-number'' value.
-func IsNaN(f float64) (is bool)
-
-// Ldexp is the inverse of Frexp.
-// It returns frac × 2<sup>exp</sup>.
-func Ldexp(frac float64, exp int) (f float64)
-
-// Modf returns integer and fractional floating-point numbers
-// that sum to f.
-// Integer and frac have the same sign as f.
-func Modf(f float64) (integer float64, frac float64)
-
-// NaN returns an IEEE 754 ``not-a-number'' value.
-func NaN() (f float64)

src/pkg/math/unsafe.go

@@ -0,0 +1,30 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+import "unsafe"
+
+// Float32bits returns the IEEE 754 binary representation of f.
+func Float32bits(f float32) uint32 {
+	return *(*uint32)(unsafe.Pointer(&f));
+}
+
+// Float32frombits returns the floating point number corresponding
+// to the IEEE 754 binary representation b.
+func Float32frombits(b uint32) float32 {
+	return *(*float32)(unsafe.Pointer(&b));
+}
+
+// Float64bits returns the IEEE 754 binary representation of f.
+func Float64bits(f float64) uint64 {
+	return *(*uint64)(unsafe.Pointer(&f));
+}
+
+// Float64frombits returns the floating point number corresponding
+// the IEEE 754 binary representation b.
+func Float64frombits(b uint64) float64 {
+	return *(*float64)(unsafe.Pointer(&b));
+}
+

src/pkg/runtime/float.c

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package math
 #include "runtime.h"
 
 static	uint64	uvnan		= 0x7FF0000000000001ULL;
@@ -172,47 +171,3 @@ modf(float64 d, float64 *ip)
 	return d - dd;
 }
 
-func Frexp(f float64) (frac float64, exp int32) {
-	frac = frexp(f, &exp);
-}
-
-func Ldexp(frac float64, exp int32) (f float64) {
-	f = ldexp(frac, exp);
-}
-
-func Modf(f float64) (integer float64, frac float64) {
-	frac = modf(f, &integer);
-}
-
-func IsInf(f float64, sign int32) (is bool) {
-	is = isInf(f, sign);
-}
-
-func IsNaN(f float64) (is bool) {
-	is = isNaN(f);
-}
-
-func Inf(sign int32) (f float64) {
-	f = Inf(sign);
-}
-
-func NaN() (f float64) {
-	f = NaN();
-}
-
-func Float32bits(f float32) (b uint32) {
-	b = float32tobits(f);
-}
-
-func Float64bits(f float64) (b uint64) {
-	b = float64tobits(f);
-}
-
-func Float32frombits(b uint32) (f float32) {
-	f = float32frombits(b);
-}
-
-func Float64frombits(b uint64) (f float64) {
-	f = float64frombits(b);
-}
-