github.com/mattn/go@v0.0.0-20171011075504-07f7db3ea99f/src/math/bits/make_examples.go (about)

     1  // Copyright 2017 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  // +build ignore
     6  
     7  // This program generates example_test.go.
     8  
     9  package main
    10  
    11  import (
    12  	"bytes"
    13  	"fmt"
    14  	"io/ioutil"
    15  	"log"
    16  	"math/bits"
    17  )
    18  
    19  const header = `// Copyright 2017 The Go Authors. All rights reserved.
    20  // Use of this source code is governed by a BSD-style
    21  // license that can be found in the LICENSE file.
    22  
    23  // Code generated by go run make_examples.go. DO NOT EDIT.
    24  
    25  package bits_test
    26  
    27  import (
    28  	"fmt"
    29  	"math/bits"
    30  )
    31  `
    32  
    33  func main() {
    34  	w := bytes.NewBuffer([]byte(header))
    35  
    36  	for _, e := range []struct {
    37  		name string
    38  		in   int
    39  		out  [4]interface{}
    40  	}{
    41  		{
    42  			name: "LeadingZeros",
    43  			in:   1,
    44  			out:  [4]interface{}{bits.LeadingZeros8(1), bits.LeadingZeros16(1), bits.LeadingZeros32(1), bits.LeadingZeros64(1)},
    45  		},
    46  		{
    47  			name: "TrailingZeros",
    48  			in:   14,
    49  			out:  [4]interface{}{bits.TrailingZeros8(14), bits.TrailingZeros16(14), bits.TrailingZeros32(14), bits.TrailingZeros64(14)},
    50  		},
    51  		{
    52  			name: "OnesCount",
    53  			in:   14,
    54  			out:  [4]interface{}{bits.OnesCount8(14), bits.OnesCount16(14), bits.OnesCount32(14), bits.OnesCount64(14)},
    55  		},
    56  		{
    57  			name: "RotateLeft",
    58  			in:   15,
    59  			out:  [4]interface{}{bits.RotateLeft8(15, 2), bits.RotateLeft16(15, 2), bits.RotateLeft32(15, 2), bits.RotateLeft64(15, 2)},
    60  		},
    61  		{
    62  			name: "Reverse",
    63  			in:   19,
    64  			out:  [4]interface{}{bits.Reverse8(19), bits.Reverse16(19), bits.Reverse32(19), bits.Reverse64(19)},
    65  		},
    66  		{
    67  			name: "ReverseBytes",
    68  			in:   15,
    69  			out:  [4]interface{}{nil, bits.ReverseBytes16(15), bits.ReverseBytes32(15), bits.ReverseBytes64(15)},
    70  		},
    71  		{
    72  			name: "Len",
    73  			in:   8,
    74  			out:  [4]interface{}{bits.Len8(8), bits.Len16(8), bits.Len32(8), bits.Len64(8)},
    75  		},
    76  	} {
    77  		for i, size := range []int{8, 16, 32, 64} {
    78  			if e.out[i] == nil {
    79  				continue // function doesn't exist
    80  			}
    81  			f := fmt.Sprintf("%s%d", e.name, size)
    82  			fmt.Fprintf(w, "\nfunc Example%s() {\n", f)
    83  			switch e.name {
    84  			case "RotateLeft", "Reverse", "ReverseBytes":
    85  				fmt.Fprintf(w, "\tfmt.Printf(\"%%0%db\\n\", %d)\n", size, e.in)
    86  				if e.name == "RotateLeft" {
    87  					fmt.Fprintf(w, "\tfmt.Printf(\"%%0%db\\n\", bits.%s(%d, 2))\n", size, f, e.in)
    88  				} else {
    89  					fmt.Fprintf(w, "\tfmt.Printf(\"%%0%db\\n\", bits.%s(%d))\n", size, f, e.in)
    90  				}
    91  				fmt.Fprintf(w, "\t// Output:\n")
    92  				fmt.Fprintf(w, "\t// %0*b\n", size, e.in)
    93  				fmt.Fprintf(w, "\t// %0*b\n", size, e.out[i])
    94  			default:
    95  				fmt.Fprintf(w, "\tfmt.Printf(\"%s(%%0%db) = %%d\\n\", %d, bits.%s(%d))\n", f, size, e.in, f, e.in)
    96  				fmt.Fprintf(w, "\t// Output:\n")
    97  				fmt.Fprintf(w, "\t// %s(%0*b) = %d\n", f, size, e.in, e.out[i])
    98  			}
    99  			fmt.Fprintf(w, "}\n")
   100  		}
   101  	}
   102  
   103  	if err := ioutil.WriteFile("example_test.go", w.Bytes(), 0666); err != nil {
   104  		log.Fatal(err)
   105  	}
   106  }