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 // The Error interface identifies a run time error.
   8 type Error interface {
   9         error
  10
  11         // RuntimeError is a no-op function but
  12         // serves to distinguish types that are runtime
  13         // errors from ordinary errors: a type is a
  14         // runtime error if it has a RuntimeError method.
  15         RuntimeError()
  16 }
  17
  18 // A TypeAssertionError explains a failed type assertion.
  19 type TypeAssertionError struct {
  20         interfaceString string
  21         concreteString  string
  22         assertedString  string
  23         missingMethod   string // one method needed by Interface, missing from Concrete
  24 }
  25
  26 func (*TypeAssertionError) RuntimeError() {}
  27
  28 func (e *TypeAssertionError) Error() string {
  29         inter := e.interfaceString
  30         if inter == "" {
  31                 inter = "interface"
  32         }
  33         if e.concreteString == "" {
  34                 return "interface conversion: " + inter + " is nil, not " + e.assertedString
  35         }
  36         if e.missingMethod == "" {
  37                 return "interface conversion: " + inter + " is " + e.concreteString +
  38                         ", not " + e.assertedString
  39         }
  40         return "interface conversion: " + e.concreteString + " is not " + e.assertedString +
  41                 ": missing method " + e.missingMethod
  42 }
  43
  44 // For calling from C.
  45 func NewTypeAssertionError(ps1, ps2, ps3 *string, pmeth *string, ret *interface{}) {
  46         var s1, s2, s3, meth string
  47
  48         if ps1 != nil {
  49                 s1 = *ps1
  50         }
  51         if ps2 != nil {
  52                 s2 = *ps2
  53         }
  54         if ps3 != nil {
  55                 s3 = *ps3
  56         }
  57         if pmeth != nil {
  58                 meth = *pmeth
  59         }
  60
  61         // For gccgo, strip out quoted strings.
  62         s1 = unquote(s1)
  63         s2 = unquote(s2)
  64         s3 = unquote(s3)
  65
  66         *ret = &TypeAssertionError{s1, s2, s3, meth}
  67 }
  68
  69 // Remove quoted strings from gccgo reflection strings.
  70 func unquote(s string) string {
  71         ls := len(s)
  72         var i int
  73         for i = 0; i < ls; i++ {
  74                 if s[i] == '\t' {
  75                         break
  76                 }
  77         }
  78         if i == ls {
  79                 return s
  80         }
  81         var q bool
  82         r := make([]byte, len(s))
  83         j := 0
  84         for i = 0; i < ls; i++ {
  85                 if s[i] == '\t' {
  86                         q = !q
  87                 } else if !q {
  88                         r[j] = s[i]
  89                         j++
  90                 }
  91         }
  92         return string(r[:j])
  93 }
  94
  95 // An errorString represents a runtime error described by a single string.
  96 type errorString string
  97
  98 func (e errorString) RuntimeError() {}
  99
 100 func (e errorString) Error() string {
 101         return "runtime error: " + string(e)
 102 }
 103
 104 // For calling from C.
 105 func NewErrorString(s string, ret *interface{}) {
 106         *ret = errorString(s)
 107 }
 108
 109 // An errorCString represents a runtime error described by a single C string.
 110 type errorCString uintptr
 111
 112 func (e errorCString) RuntimeError() {}
 113
 114 func cstringToGo(uintptr) string
 115
 116 func (e errorCString) Error() string {
 117         return "runtime error: " + cstringToGo(uintptr(e))
 118 }
 119
 120 // For calling from C.
 121 func NewErrorCString(s uintptr, ret *interface{}) {
 122         *ret = errorCString(s)
 123 }
 124
 125 type stringer interface {
 126         String() string
 127 }
 128
 129 func typestring(interface{}) string
 130
 131 // For calling from C.
 132 // Prints an argument passed to panic.
 133 // There's room for arbitrary complexity here, but we keep it
 134 // simple and handle just a few important cases: int, string, and Stringer.
 135 func Printany(i interface{}) {
 136         switch v := i.(type) {
 137         case nil:
 138                 print("nil")
 139         case stringer:
 140                 print(v.String())
 141         case error:
 142                 print(v.Error())
 143         case int:
 144                 print(v)
 145         case string:
 146                 print(v)
 147         default:
 148                 print("(", typestring(i), ") ", i)
 149         }
 150 }
 151
 152 // called from generated code
 153 func panicwrap(pkg, typ, meth string) {
 154         panic("value method " + pkg + "." + typ + "." + meth + " called using nil *" + typ + " pointer")
 155 }