94 строки
2.3 KiB
Go
94 строки
2.3 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:generate go run gen.go -output table.go
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// Package f32 implements some linear algebra and GL helpers for float32s.
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//
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// Types defined in this package have methods implementing common
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// mathematical operations. The common form for these functions is
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//
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// func (dst *T) Op(lhs, rhs *T)
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//
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// which reads in traditional mathematical notation as
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//
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// dst = lhs op rhs.
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//
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// It is safe to use the destination address as the left-hand side,
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// that is, dst *= rhs is dst.Mul(dst, rhs).
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//
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// WARNING
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//
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// The interface to this package is not stable. It will change considerably.
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// Only use functions that provide package documentation. Semantics are
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// non-obvious. Be prepared for the package name to change.
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package f32 // import "golang.org/x/mobile/f32"
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import (
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"encoding/binary"
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"fmt"
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"math"
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)
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type Radian float32
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func Cos(x float32) float32 {
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const n = sinTableLen
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i := uint32(int32(x * (n / math.Pi)))
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i += n / 2
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i &= 2*n - 1
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if i >= n {
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return -sinTable[i&(n-1)]
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}
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return sinTable[i&(n-1)]
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}
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func Sin(x float32) float32 {
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const n = sinTableLen
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i := uint32(int32(x * (n / math.Pi)))
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i &= 2*n - 1
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if i >= n {
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return -sinTable[i&(n-1)]
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}
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return sinTable[i&(n-1)]
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}
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func Sqrt(x float32) float32 {
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return float32(math.Sqrt(float64(x))) // TODO(crawshaw): implement
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}
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func Tan(x float32) float32 {
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return float32(math.Tan(float64(x))) // TODO(crawshaw): fast version
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}
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// Bytes returns the byte representation of float32 values in the given byte
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// order. byteOrder must be either binary.BigEndian or binary.LittleEndian.
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func Bytes(byteOrder binary.ByteOrder, values ...float32) []byte {
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le := false
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switch byteOrder {
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case binary.BigEndian:
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case binary.LittleEndian:
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le = true
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default:
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panic(fmt.Sprintf("invalid byte order %v", byteOrder))
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}
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b := make([]byte, 4*len(values))
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for i, v := range values {
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u := math.Float32bits(v)
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if le {
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b[4*i+0] = byte(u >> 0)
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b[4*i+1] = byte(u >> 8)
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b[4*i+2] = byte(u >> 16)
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b[4*i+3] = byte(u >> 24)
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} else {
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b[4*i+0] = byte(u >> 24)
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b[4*i+1] = byte(u >> 16)
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b[4*i+2] = byte(u >> 8)
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b[4*i+3] = byte(u >> 0)
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}
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}
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return b
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}
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