tostring_test.go

     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  // Formatting of reflection types and values for debugging.
     6  // Not defined as methods so they do not need to be linked into most binaries;
     7  // the functions are not used by the library itself, only in tests.
     8  
     9  package reflect_test
    10  
    11  import (
    12  	. "reflect"
    13  	"strconv"
    14  )
    15  
    16  // valueToString returns a textual representation of the reflection value val.
    17  // For debugging only.
    18  func valueToString(val Value) string {
    19  	var str string
    20  	if !val.IsValid() {
    21  		return "<zero Value>"
    22  	}
    23  	typ := val.Type()
    24  	switch val.Kind() {
    25  	case Int, Int8, Int16, Int32, Int64:
    26  		return strconv.FormatInt(val.Int(), 10)
    27  	case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
    28  		return strconv.FormatUint(val.Uint(), 10)
    29  	case Float32, Float64:
    30  		return strconv.FormatFloat(val.Float(), 'g', -1, 64)
    31  	case Complex64, Complex128:
    32  		c := val.Complex()
    33  		return strconv.FormatFloat(real(c), 'g', -1, 64) + "+" + strconv.FormatFloat(imag(c), 'g', -1, 64) + "i"
    34  	case String:
    35  		return val.String()
    36  	case Bool:
    37  		if val.Bool() {
    38  			return "true"
    39  		} else {
    40  			return "false"
    41  		}
    42  	case Pointer:
    43  		v := val
    44  		str = typ.String() + "("
    45  		if v.IsNil() {
    46  			str += "0"
    47  		} else {
    48  			str += "&" + valueToString(v.Elem())
    49  		}
    50  		str += ")"
    51  		return str
    52  	case Array, Slice:
    53  		v := val
    54  		str += typ.String()
    55  		str += "{"
    56  		for i := 0; i < v.Len(); i++ {
    57  			if i > 0 {
    58  				str += ", "
    59  			}
    60  			str += valueToString(v.Index(i))
    61  		}
    62  		str += "}"
    63  		return str
    64  	case Map:
    65  		t := typ
    66  		str = t.String()
    67  		str += "{"
    68  		str += "<can't iterate on maps>"
    69  		str += "}"
    70  		return str
    71  	case Chan:
    72  		str = typ.String()
    73  		return str
    74  	case Struct:
    75  		t := typ
    76  		v := val
    77  		str += t.String()
    78  		str += "{"
    79  		for i, n := 0, v.NumField(); i < n; i++ {
    80  			if i > 0 {
    81  				str += ", "
    82  			}
    83  			str += valueToString(v.Field(i))
    84  		}
    85  		str += "}"
    86  		return str
    87  	case Interface:
    88  		return typ.String() + "(" + valueToString(val.Elem()) + ")"
    89  	case Func:
    90  		v := val
    91  		return typ.String() + "(" + strconv.FormatUint(uint64(v.Pointer()), 10) + ")"
    92  	default:
    93  		panic("valueToString: can't print type " + typ.String())
    94  	}
    95  }
    96
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