libgo/go/runtime/error.go

   1 // Copyright 2010 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 runtime
   6
   7 import "unsafe"
   8
   9 // The Error interface identifies a run time error.
  10 type Error interface {
  11         error
  12
  13         // RuntimeError is a no-op function but
  14         // serves to distinguish types that are run time
  15         // errors from ordinary errors: a type is a
  16         // run time error if it has a RuntimeError method.
  17         RuntimeError()
  18 }
  19
  20 // A TypeAssertionError explains a failed type assertion.
  21 type TypeAssertionError struct {
  22         interfaceString string
  23         concreteString  string
  24         assertedString  string
  25         missingMethod   string // one method needed by Interface, missing from Concrete
  26 }
  27
  28 func (*TypeAssertionError) RuntimeError() {}
  29
  30 func (e *TypeAssertionError) Error() string {
  31         inter := e.interfaceString
  32         if inter == "" {
  33                 inter = "interface"
  34         }
  35         if e.concreteString == "" {
  36                 return "interface conversion: " + inter + " is nil, not " + e.assertedString
  37         }
  38         if e.missingMethod == "" {
  39                 return "interface conversion: " + inter + " is " + e.concreteString +
  40                         ", not " + e.assertedString
  41         }
  42         return "interface conversion: " + e.concreteString + " is not " + e.assertedString +
  43                 ": missing method " + e.missingMethod
  44 }
  45
  46 // For calling from C.
  47 func NewTypeAssertionError(ps1, ps2, ps3 *string, pmeth *string, ret *interface{}) {
  48         var s1, s2, s3, meth string
  49
  50         if ps1 != nil {
  51                 s1 = *ps1
  52         }
  53         if ps2 != nil {
  54                 s2 = *ps2
  55         }
  56         if ps3 != nil {
  57                 s3 = *ps3
  58         }
  59         if pmeth != nil {
  60                 meth = *pmeth
  61         }
  62
  63         // For gccgo, strip out quoted strings.
  64         s1 = unquote(s1)
  65         s2 = unquote(s2)
  66         s3 = unquote(s3)
  67
  68         *ret = &TypeAssertionError{s1, s2, s3, meth}
  69 }
  70
  71 // Remove quoted strings from gccgo reflection strings.
  72 func unquote(s string) string {
  73         ls := len(s)
  74         var i int
  75         for i = 0; i < ls; i++ {
  76                 if s[i] == '\t' {
  77                         break
  78                 }
  79         }
  80         if i == ls {
  81                 return s
  82         }
  83         var q bool
  84         r := make([]byte, len(s))
  85         j := 0
  86         for i = 0; i < ls; i++ {
  87                 if s[i] == '\t' {
  88                         q = !q
  89                 } else if !q {
  90                         r[j] = s[i]
  91                         j++
  92                 }
  93         }
  94         return string(r[:j])
  95 }
  96
  97 // An errorString represents a runtime error described by a single string.
  98 type errorString string
  99
 100 func (e errorString) RuntimeError() {}
 101
 102 func (e errorString) Error() string {
 103         return "runtime error: " + string(e)
 104 }
 105
 106 // An errorCString represents a runtime error described by a single C string.
 107 // Not "type errorCString uintptr" because of http://golang.org/issue/7084.
 108 type errorCString struct{ cstr uintptr }
 109
 110 func (e errorCString) RuntimeError() {}
 111
 112 func (e errorCString) Error() string {
 113         return "runtime error: " + gostringnocopy((*byte)(unsafe.Pointer(e.cstr)))
 114 }
 115
 116 // For calling from C.
 117 func NewErrorCString(s uintptr, ret *interface{}) {
 118         *ret = errorCString{s}
 119 }
 120
 121 // plainError represents a runtime error described a string without
 122 // the prefix "runtime error: " after invoking errorString.Error().
 123 // See Issue #14965.
 124 type plainError string
 125
 126 func (e plainError) RuntimeError() {}
 127
 128 func (e plainError) Error() string {
 129         return string(e)
 130 }
 131
 132 type stringer interface {
 133         String() string
 134 }
 135
 136 func typestring(x interface{}) string {
 137         e := efaceOf(&x)
 138         return *e._type.string
 139 }
 140
 141 // For calling from C.
 142 // Prints an argument passed to panic.
 143 // There's room for arbitrary complexity here, but we keep it
 144 // simple and handle just a few important cases: int, string, and Stringer.
 145 func printany(i interface{}) {
 146         switch v := i.(type) {
 147         case nil:
 148                 print("nil")
 149         case stringer:
 150                 print(v.String())
 151         case error:
 152                 print(v.Error())
 153         case int:
 154                 print(v)
 155         case string:
 156                 print(v)
 157         default:
 158                 print("(", typestring(i), ") ", i)
 159         }
 160 }
 161
 162 // called from generated code
 163 func panicwrap(pkg, typ, meth string) {
 164         panic(plainError("value method " + pkg + "." + typ + "." + meth + " called using nil *" + typ + " pointer"))
 165 }