math_test.go

     1  // Copyright 2025 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package strconv_test
     6  
     7  import (
     8  	"math"
     9  	. "strconv"
    10  	"testing"
    11  )
    12  
    13  var pow10Tests = []struct {
    14  	exp10 int
    15  	mant  uint128
    16  	exp2  int
    17  	ok    bool
    18  }{
    19  	{-349, uint128{0, 0}, 0, false},
    20  	{-348, uint128{0xFA8FD5A0081C0288, 0x1732C869CD60E453}, -1157, true},
    21  	{0, uint128{0x8000000000000000, 0x0000000000000000}, 0, true},
    22  	{347, uint128{0xD13EB46469447567, 0x4B7195F2D2D1A9FB}, 1152, true},
    23  	{348, uint128{0, 0}, 0, false},
    24  }
    25  
    26  func TestPow10(t *testing.T) {
    27  	for _, tt := range pow10Tests {
    28  		mant, exp2, ok := Pow10(tt.exp10)
    29  		if mant != tt.mant || exp2 != tt.exp2 {
    30  			t.Errorf("pow10(%d) = %#016x, %#016x, %d, %v want %#016x,%#016x, %d, %v",
    31  				tt.exp10, mant.Hi, mant.Lo, exp2, ok,
    32  				tt.mant.Hi, tt.mant.Lo, tt.exp2, tt.ok)
    33  		}
    34  	}
    35  }
    36  
    37  func u128(hi, lo uint64) uint128 {
    38  	return uint128{Hi: hi, Lo: lo}
    39  }
    40  
    41  var umul192Tests = []struct {
    42  	x   uint64
    43  	y   uint128
    44  	hi  uint64
    45  	mid uint64
    46  	lo  uint64
    47  }{
    48  	{0, u128(0, 0), 0, 0, 0},
    49  	{^uint64(0), u128(^uint64(0), ^uint64(0)), ^uint64(1), ^uint64(0), 1},
    50  }
    51  
    52  func TestUmul192(t *testing.T) {
    53  	for _, tt := range umul192Tests {
    54  		hi, mid, lo := Umul192(tt.x, tt.y)
    55  		if hi != tt.hi || mid != tt.mid || lo != tt.lo {
    56  			t.Errorf("umul192(%#x, {%#x,%#x}) = %#x, %#x, %#x, want %#x, %#x, %#x",
    57  				tt.x, tt.y.Hi, tt.y.Lo, hi, mid, lo, tt.hi, tt.mid, tt.lo)
    58  		}
    59  	}
    60  }
    61  
    62  func TestMulLog10_2(t *testing.T) {
    63  	for x := -1600; x <= +1600; x++ {
    64  		iMath := mulLog10_2(x)
    65  		fMath := int(math.Floor(float64(x) * math.Ln2 / math.Ln10))
    66  		if iMath != fMath {
    67  			t.Errorf("mulLog10_2(%d) failed: %d vs %d\n", x, iMath, fMath)
    68  		}
    69  	}
    70  }
    71  
    72  func TestMulLog2_10(t *testing.T) {
    73  	for x := -500; x <= +500; x++ {
    74  		iMath := mulLog2_10(x)
    75  		fMath := int(math.Floor(float64(x) * math.Ln10 / math.Ln2))
    76  		if iMath != fMath {
    77  			t.Errorf("mulLog2_10(%d) failed: %d vs %d\n", x, iMath, fMath)
    78  		}
    79  	}
    80  }
    81
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