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Source file src/encoding/gob/encgen.go

Documentation: encoding/gob

     1  // Copyright 2009 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  // encgen writes the helper functions for encoding. Intended to be
     8  // used with go generate; see the invocation in encode.go.
     9  
    10  // TODO: We could do more by being unsafe. Add a -unsafe flag?
    11  
    12  package main
    13  
    14  import (
    15  	"bytes"
    16  	"flag"
    17  	"fmt"
    18  	"go/format"
    19  	"log"
    20  	"os"
    21  )
    22  
    23  var output = flag.String("output", "enc_helpers.go", "file name to write")
    24  
    25  type Type struct {
    26  	lower   string
    27  	upper   string
    28  	zero    string
    29  	encoder string
    30  }
    31  
    32  var types = []Type{
    33  	{
    34  		"bool",
    35  		"Bool",
    36  		"false",
    37  		`if x {
    38  			state.encodeUint(1)
    39  		} else {
    40  			state.encodeUint(0)
    41  		}`,
    42  	},
    43  	{
    44  		"complex64",
    45  		"Complex64",
    46  		"0+0i",
    47  		`rpart := floatBits(float64(real(x)))
    48  		ipart := floatBits(float64(imag(x)))
    49  		state.encodeUint(rpart)
    50  		state.encodeUint(ipart)`,
    51  	},
    52  	{
    53  		"complex128",
    54  		"Complex128",
    55  		"0+0i",
    56  		`rpart := floatBits(real(x))
    57  		ipart := floatBits(imag(x))
    58  		state.encodeUint(rpart)
    59  		state.encodeUint(ipart)`,
    60  	},
    61  	{
    62  		"float32",
    63  		"Float32",
    64  		"0",
    65  		`bits := floatBits(float64(x))
    66  		state.encodeUint(bits)`,
    67  	},
    68  	{
    69  		"float64",
    70  		"Float64",
    71  		"0",
    72  		`bits := floatBits(x)
    73  		state.encodeUint(bits)`,
    74  	},
    75  	{
    76  		"int",
    77  		"Int",
    78  		"0",
    79  		`state.encodeInt(int64(x))`,
    80  	},
    81  	{
    82  		"int16",
    83  		"Int16",
    84  		"0",
    85  		`state.encodeInt(int64(x))`,
    86  	},
    87  	{
    88  		"int32",
    89  		"Int32",
    90  		"0",
    91  		`state.encodeInt(int64(x))`,
    92  	},
    93  	{
    94  		"int64",
    95  		"Int64",
    96  		"0",
    97  		`state.encodeInt(x)`,
    98  	},
    99  	{
   100  		"int8",
   101  		"Int8",
   102  		"0",
   103  		`state.encodeInt(int64(x))`,
   104  	},
   105  	{
   106  		"string",
   107  		"String",
   108  		`""`,
   109  		`state.encodeUint(uint64(len(x)))
   110  		state.b.WriteString(x)`,
   111  	},
   112  	{
   113  		"uint",
   114  		"Uint",
   115  		"0",
   116  		`state.encodeUint(uint64(x))`,
   117  	},
   118  	{
   119  		"uint16",
   120  		"Uint16",
   121  		"0",
   122  		`state.encodeUint(uint64(x))`,
   123  	},
   124  	{
   125  		"uint32",
   126  		"Uint32",
   127  		"0",
   128  		`state.encodeUint(uint64(x))`,
   129  	},
   130  	{
   131  		"uint64",
   132  		"Uint64",
   133  		"0",
   134  		`state.encodeUint(x)`,
   135  	},
   136  	{
   137  		"uintptr",
   138  		"Uintptr",
   139  		"0",
   140  		`state.encodeUint(uint64(x))`,
   141  	},
   142  	// uint8 Handled separately.
   143  }
   144  
   145  func main() {
   146  	log.SetFlags(0)
   147  	log.SetPrefix("encgen: ")
   148  	flag.Parse()
   149  	if flag.NArg() != 0 {
   150  		log.Fatal("usage: encgen [--output filename]")
   151  	}
   152  	var b bytes.Buffer
   153  	fmt.Fprintf(&b, "// Code generated by go run encgen.go -output %s; DO NOT EDIT.\n", *output)
   154  	fmt.Fprint(&b, header)
   155  	printMaps(&b, "Array")
   156  	fmt.Fprint(&b, "\n")
   157  	printMaps(&b, "Slice")
   158  	for _, t := range types {
   159  		fmt.Fprintf(&b, arrayHelper, t.lower, t.upper)
   160  		fmt.Fprintf(&b, sliceHelper, t.lower, t.upper, t.zero, t.encoder)
   161  	}
   162  	source, err := format.Source(b.Bytes())
   163  	if err != nil {
   164  		log.Fatal("source format error:", err)
   165  	}
   166  	fd, err := os.Create(*output)
   167  	_, err = fd.Write(source)
   168  	if err != nil {
   169  		log.Fatal(err)
   170  	}
   171  }
   172  
   173  func printMaps(b *bytes.Buffer, upperClass string) {
   174  	fmt.Fprintf(b, "var enc%sHelper = map[reflect.Kind]encHelper{\n", upperClass)
   175  	for _, t := range types {
   176  		fmt.Fprintf(b, "reflect.%s: enc%s%s,\n", t.upper, t.upper, upperClass)
   177  	}
   178  	fmt.Fprintf(b, "}\n")
   179  }
   180  
   181  const header = `
   182  // Copyright 2014 The Go Authors. All rights reserved.
   183  // Use of this source code is governed by a BSD-style
   184  // license that can be found in the LICENSE file.
   185  
   186  package gob
   187  
   188  import (
   189  	"reflect"
   190  )
   191  
   192  `
   193  
   194  const arrayHelper = `
   195  func enc%[2]sArray(state *encoderState, v reflect.Value) bool {
   196  	// Can only slice if it is addressable.
   197  	if !v.CanAddr() {
   198  		return false
   199  	}
   200  	return enc%[2]sSlice(state, v.Slice(0, v.Len()))
   201  }
   202  `
   203  
   204  const sliceHelper = `
   205  func enc%[2]sSlice(state *encoderState, v reflect.Value) bool {
   206  	slice, ok := v.Interface().([]%[1]s)
   207  	if !ok {
   208  		// It is kind %[1]s but not type %[1]s. TODO: We can handle this unsafely.
   209  		return false
   210  	}
   211  	for _, x := range slice {
   212  		if x != %[3]s || state.sendZero {
   213  			%[4]s
   214  		}
   215  	}
   216  	return true
   217  }
   218  `
   219  

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