// Copyright 2015 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 fixed implements fixed-point integer types.
 package fixed // import "golang.org/x/image/math/fixed"
 
 import (
 	"fmt"
 )
 
 // TODO: implement fmt.Formatter for %f and %g.
 
 // I returns the integer value i as an Int26_6.
 //
 // For example, passing the integer value 2 yields Int26_6(128).
 func I(i int) Int26_6 {
 	return Int26_6(i << 6)
 }
 
 // Int26_6 is a signed 26.6 fixed-point number.
 //
 // The integer part ranges from -33554432 to 33554431, inclusive. The
 // fractional part has 6 bits of precision.
 //
 // For example, the number one-and-a-quarter is Int26_6(1<<6 + 1<<4).
 type Int26_6 int32
 
 // String returns a human-readable representation of a 26.6 fixed-point number.
 //
 // For example, the number one-and-a-quarter becomes "1:16".
 func (x Int26_6) String() string {
 	const shift, mask = 6, 1<<6 - 1
 	if x >= 0 {
 		return fmt.Sprintf("%d:%02d", int32(x>>shift), int32(x&mask))
 	}
 	x = -x
 	if x >= 0 {
 		return fmt.Sprintf("-%d:%02d", int32(x>>shift), int32(x&mask))
 	}
 	return "-33554432:00" // The minimum value is -(1<<25).
 }
 
 // Floor returns the greatest integer value less than or equal to x.
 //
 // Its return type is int, not Int26_6.
 func (x Int26_6) Floor() int { return int((x + 0x00) >> 6) }
 
 // Round returns the nearest integer value to x. Ties are rounded up.
 //
 // Its return type is int, not Int26_6.
 func (x Int26_6) Round() int { return int((x + 0x20) >> 6) }
 
 // Ceil returns the least integer value greater than or equal to x.
 //
 // Its return type is int, not Int26_6.
 func (x Int26_6) Ceil() int { return int((x + 0x3f) >> 6) }
 
 // Mul returns x*y in 26.6 fixed-point arithmetic.
 func (x Int26_6) Mul(y Int26_6) Int26_6 {
 	return Int26_6((int64(x)*int64(y) + 1<<5) >> 6)
 }
 
 // Int52_12 is a signed 52.12 fixed-point number.
 //
 // The integer part ranges from -2251799813685248 to 2251799813685247,
 // inclusive. The fractional part has 12 bits of precision.
 //
 // For example, the number one-and-a-quarter is Int52_12(1<<12 + 1<<10).
 type Int52_12 int64
 
 // String returns a human-readable representation of a 52.12 fixed-point
 // number.
 //
 // For example, the number one-and-a-quarter becomes "1:1024".
 func (x Int52_12) String() string {
 	const shift, mask = 12, 1<<12 - 1
 	if x >= 0 {
 		return fmt.Sprintf("%d:%04d", int64(x>>shift), int64(x&mask))
 	}
 	x = -x
 	if x >= 0 {
 		return fmt.Sprintf("-%d:%04d", int64(x>>shift), int64(x&mask))
 	}
 	return "-2251799813685248:0000" // The minimum value is -(1<<51).
 }
 
 // Floor returns the greatest integer value less than or equal to x.
 //
 // Its return type is int, not Int52_12.
 func (x Int52_12) Floor() int { return int((x + 0x000) >> 12) }
 
 // Round returns the nearest integer value to x. Ties are rounded up.
 //
 // Its return type is int, not Int52_12.
 func (x Int52_12) Round() int { return int((x + 0x800) >> 12) }
 
 // Ceil returns the least integer value greater than or equal to x.
 //
 // Its return type is int, not Int52_12.
 func (x Int52_12) Ceil() int { return int((x + 0xfff) >> 12) }
 
 // Mul returns x*y in 52.12 fixed-point arithmetic.
 func (x Int52_12) Mul(y Int52_12) Int52_12 {
 	const M, N = 52, 12
 	lo, hi := muli64(int64(x), int64(y))
 	ret := Int52_12(hi<<M | lo>>N)
 	ret += Int52_12((lo >> (N - 1)) & 1) // Round to nearest, instead of rounding down.
 	return ret
 }
 
 // muli64 multiplies two int64 values, returning the 128-bit signed integer
 // result as two uint64 values.
 //
 // This implementation is similar to $GOROOT/src/runtime/softfloat64.go's mullu
 // function, which is in turn adapted from Hacker's Delight.
 func muli64(u, v int64) (lo, hi uint64) {
 	const (
 		s    = 32
 		mask = 1<<s - 1
 	)
 
 	u1 := uint64(u >> s)
 	u0 := uint64(u & mask)
 	v1 := uint64(v >> s)
 	v0 := uint64(v & mask)
 
 	w0 := u0 * v0
 	t := u1*v0 + w0>>s
 	w1 := t & mask
 	w2 := uint64(int64(t) >> s)
 	w1 += u0 * v1
 	return uint64(u) * uint64(v), u1*v1 + w2 + uint64(int64(w1)>>s)
 }
 
 // P returns the integer values x and y as a Point26_6.
 //
 // For example, passing the integer values (2, -3) yields Point26_6{128, -192}.
 func P(x, y int) Point26_6 {
 	return Point26_6{Int26_6(x << 6), Int26_6(y << 6)}
 }
 
 // Point26_6 is a 26.6 fixed-point coordinate pair.
 //
 // It is analogous to the image.Point type in the standard library.
 type Point26_6 struct {
 	X, Y Int26_6
 }
 
 // Add returns the vector p+q.
 func (p Point26_6) Add(q Point26_6) Point26_6 {
 	return Point26_6{p.X + q.X, p.Y + q.Y}
 }
 
 // Sub returns the vector p-q.
 func (p Point26_6) Sub(q Point26_6) Point26_6 {
 	return Point26_6{p.X - q.X, p.Y - q.Y}
 }
 
 // Mul returns the vector p*k.
 func (p Point26_6) Mul(k Int26_6) Point26_6 {
 	return Point26_6{p.X * k / 64, p.Y * k / 64}
 }
 
 // Div returns the vector p/k.
 func (p Point26_6) Div(k Int26_6) Point26_6 {
 	return Point26_6{p.X * 64 / k, p.Y * 64 / k}
 }
 
 // In returns whether p is in r.
 func (p Point26_6) In(r Rectangle26_6) bool {
 	return r.Min.X <= p.X && p.X < r.Max.X && r.Min.Y <= p.Y && p.Y < r.Max.Y
 }
 
 // Point52_12 is a 52.12 fixed-point coordinate pair.
 //
 // It is analogous to the image.Point type in the standard library.
 type Point52_12 struct {
 	X, Y Int52_12
 }
 
 // Add returns the vector p+q.
 func (p Point52_12) Add(q Point52_12) Point52_12 {
 	return Point52_12{p.X + q.X, p.Y + q.Y}
 }
 
 // Sub returns the vector p-q.
 func (p Point52_12) Sub(q Point52_12) Point52_12 {
 	return Point52_12{p.X - q.X, p.Y - q.Y}
 }
 
 // Mul returns the vector p*k.
 func (p Point52_12) Mul(k Int52_12) Point52_12 {
 	return Point52_12{p.X * k / 4096, p.Y * k / 4096}
 }
 
 // Div returns the vector p/k.
 func (p Point52_12) Div(k Int52_12) Point52_12 {
 	return Point52_12{p.X * 4096 / k, p.Y * 4096 / k}
 }
 
 // In returns whether p is in r.
 func (p Point52_12) In(r Rectangle52_12) bool {
 	return r.Min.X <= p.X && p.X < r.Max.X && r.Min.Y <= p.Y && p.Y < r.Max.Y
 }
 
 // R returns the integer values minX, minY, maxX, maxY as a Rectangle26_6.
 //
 // For example, passing the integer values (0, 1, 2, 3) yields
 // Rectangle26_6{Point26_6{0, 64}, Point26_6{128, 192}}.
 //
 // Like the image.Rect function in the standard library, the returned rectangle
 // has minimum and maximum coordinates swapped if necessary so that it is
 // well-formed.
 func R(minX, minY, maxX, maxY int) Rectangle26_6 {
 	if minX > maxX {
 		minX, maxX = maxX, minX
 	}
 	if minY > maxY {
 		minY, maxY = maxY, minY
 	}
 	return Rectangle26_6{
 		Point26_6{
 			Int26_6(minX << 6),
 			Int26_6(minY << 6),
 		},
 		Point26_6{
 			Int26_6(maxX << 6),
 			Int26_6(maxY << 6),
 		},
 	}
 }
 
 // Rectangle26_6 is a 26.6 fixed-point coordinate rectangle. The Min bound is
 // inclusive and the Max bound is exclusive. It is well-formed if Min.X <=
 // Max.X and likewise for Y.
 //
 // It is analogous to the image.Rectangle type in the standard library.
 type Rectangle26_6 struct {
 	Min, Max Point26_6
 }
 
 // Add returns the rectangle r translated by p.
 func (r Rectangle26_6) Add(p Point26_6) Rectangle26_6 {
 	return Rectangle26_6{
 		Point26_6{r.Min.X + p.X, r.Min.Y + p.Y},
 		Point26_6{r.Max.X + p.X, r.Max.Y + p.Y},
 	}
 }
 
 // Sub returns the rectangle r translated by -p.
 func (r Rectangle26_6) Sub(p Point26_6) Rectangle26_6 {
 	return Rectangle26_6{
 		Point26_6{r.Min.X - p.X, r.Min.Y - p.Y},
 		Point26_6{r.Max.X - p.X, r.Max.Y - p.Y},
 	}
 }
 
 // Intersect returns the largest rectangle contained by both r and s. If the
 // two rectangles do not overlap then the zero rectangle will be returned.
 func (r Rectangle26_6) Intersect(s Rectangle26_6) Rectangle26_6 {
 	if r.Min.X < s.Min.X {
 		r.Min.X = s.Min.X
 	}
 	if r.Min.Y < s.Min.Y {
 		r.Min.Y = s.Min.Y
 	}
 	if r.Max.X > s.Max.X {
 		r.Max.X = s.Max.X
 	}
 	if r.Max.Y > s.Max.Y {
 		r.Max.Y = s.Max.Y
 	}
 	// Letting r0 and s0 be the values of r and s at the time that the method
 	// is called, this next line is equivalent to:
 	//
 	// if max(r0.Min.X, s0.Min.X) >= min(r0.Max.X, s0.Max.X) || likewiseForY { etc }
 	if r.Empty() {
 		return Rectangle26_6{}
 	}
 	return r
 }
 
 // Union returns the smallest rectangle that contains both r and s.
 func (r Rectangle26_6) Union(s Rectangle26_6) Rectangle26_6 {
 	if r.Empty() {
 		return s
 	}
 	if s.Empty() {
 		return r
 	}
 	if r.Min.X > s.Min.X {
 		r.Min.X = s.Min.X
 	}
 	if r.Min.Y > s.Min.Y {
 		r.Min.Y = s.Min.Y
 	}
 	if r.Max.X < s.Max.X {
 		r.Max.X = s.Max.X
 	}
 	if r.Max.Y < s.Max.Y {
 		r.Max.Y = s.Max.Y
 	}
 	return r
 }
 
 // Empty returns whether the rectangle contains no points.
 func (r Rectangle26_6) Empty() bool {
 	return r.Min.X >= r.Max.X || r.Min.Y >= r.Max.Y
 }
 
 // In returns whether every point in r is in s.
 func (r Rectangle26_6) In(s Rectangle26_6) bool {
 	if r.Empty() {
 		return true
 	}
 	// Note that r.Max is an exclusive bound for r, so that r.In(s)
 	// does not require that r.Max.In(s).
 	return s.Min.X <= r.Min.X && r.Max.X <= s.Max.X &&
 		s.Min.Y <= r.Min.Y && r.Max.Y <= s.Max.Y
 }
 
 // Rectangle52_12 is a 52.12 fixed-point coordinate rectangle. The Min bound is
 // inclusive and the Max bound is exclusive. It is well-formed if Min.X <=
 // Max.X and likewise for Y.
 //
 // It is analogous to the image.Rectangle type in the standard library.
 type Rectangle52_12 struct {
 	Min, Max Point52_12
 }
 
 // Add returns the rectangle r translated by p.
 func (r Rectangle52_12) Add(p Point52_12) Rectangle52_12 {
 	return Rectangle52_12{
 		Point52_12{r.Min.X + p.X, r.Min.Y + p.Y},
 		Point52_12{r.Max.X + p.X, r.Max.Y + p.Y},
 	}
 }
 
 // Sub returns the rectangle r translated by -p.
 func (r Rectangle52_12) Sub(p Point52_12) Rectangle52_12 {
 	return Rectangle52_12{
 		Point52_12{r.Min.X - p.X, r.Min.Y - p.Y},
 		Point52_12{r.Max.X - p.X, r.Max.Y - p.Y},
 	}
 }
 
 // Intersect returns the largest rectangle contained by both r and s. If the
 // two rectangles do not overlap then the zero rectangle will be returned.
 func (r Rectangle52_12) Intersect(s Rectangle52_12) Rectangle52_12 {
 	if r.Min.X < s.Min.X {
 		r.Min.X = s.Min.X
 	}
 	if r.Min.Y < s.Min.Y {
 		r.Min.Y = s.Min.Y
 	}
 	if r.Max.X > s.Max.X {
 		r.Max.X = s.Max.X
 	}
 	if r.Max.Y > s.Max.Y {
 		r.Max.Y = s.Max.Y
 	}
 	// Letting r0 and s0 be the values of r and s at the time that the method
 	// is called, this next line is equivalent to:
 	//
 	// if max(r0.Min.X, s0.Min.X) >= min(r0.Max.X, s0.Max.X) || likewiseForY { etc }
 	if r.Empty() {
 		return Rectangle52_12{}
 	}
 	return r
 }
 
 // Union returns the smallest rectangle that contains both r and s.
 func (r Rectangle52_12) Union(s Rectangle52_12) Rectangle52_12 {
 	if r.Empty() {
 		return s
 	}
 	if s.Empty() {
 		return r
 	}
 	if r.Min.X > s.Min.X {
 		r.Min.X = s.Min.X
 	}
 	if r.Min.Y > s.Min.Y {
 		r.Min.Y = s.Min.Y
 	}
 	if r.Max.X < s.Max.X {
 		r.Max.X = s.Max.X
 	}
 	if r.Max.Y < s.Max.Y {
 		r.Max.Y = s.Max.Y
 	}
 	return r
 }
 
 // Empty returns whether the rectangle contains no points.
 func (r Rectangle52_12) Empty() bool {
 	return r.Min.X >= r.Max.X || r.Min.Y >= r.Max.Y
 }
 
 // In returns whether every point in r is in s.
 func (r Rectangle52_12) In(s Rectangle52_12) bool {
 	if r.Empty() {
 		return true
 	}
 	// Note that r.Max is an exclusive bound for r, so that r.In(s)
 	// does not require that r.Max.In(s).
 	return s.Min.X <= r.Min.X && r.Max.X <= s.Max.X &&
 		s.Min.Y <= r.Min.Y && r.Max.Y <= s.Max.Y
 }