Source file src/cmd/compile/internal/typecheck/iexport.go
1 // Copyright 2018 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 // Indexed package export. 6 // 7 // The indexed export data format is an evolution of the previous 8 // binary export data format. Its chief contribution is introducing an 9 // index table, which allows efficient random access of individual 10 // declarations and inline function bodies. In turn, this allows 11 // avoiding unnecessary work for compilation units that import large 12 // packages. 13 // 14 // 15 // The top-level data format is structured as: 16 // 17 // Header struct { 18 // Tag byte // 'i' 19 // Version uvarint 20 // StringSize uvarint 21 // DataSize uvarint 22 // } 23 // 24 // Strings [StringSize]byte 25 // Data [DataSize]byte 26 // 27 // MainIndex []struct{ 28 // PkgPath stringOff 29 // PkgName stringOff 30 // PkgHeight uvarint 31 // 32 // Decls []struct{ 33 // Name stringOff 34 // Offset declOff 35 // } 36 // } 37 // 38 // Fingerprint [8]byte 39 // 40 // uvarint means a uint64 written out using uvarint encoding. 41 // 42 // []T means a uvarint followed by that many T objects. In other 43 // words: 44 // 45 // Len uvarint 46 // Elems [Len]T 47 // 48 // stringOff means a uvarint that indicates an offset within the 49 // Strings section. At that offset is another uvarint, followed by 50 // that many bytes, which form the string value. 51 // 52 // declOff means a uvarint that indicates an offset within the Data 53 // section where the associated declaration can be found. 54 // 55 // 56 // There are five kinds of declarations, distinguished by their first 57 // byte: 58 // 59 // type Var struct { 60 // Tag byte // 'V' 61 // Pos Pos 62 // Type typeOff 63 // } 64 // 65 // type Func struct { 66 // Tag byte // 'F' or 'G' 67 // Pos Pos 68 // TypeParams []typeOff // only present if Tag == 'G' 69 // Signature Signature 70 // } 71 // 72 // type Const struct { 73 // Tag byte // 'C' 74 // Pos Pos 75 // Value Value 76 // } 77 // 78 // type Type struct { 79 // Tag byte // 'T' or 'U' 80 // Pos Pos 81 // TypeParams []typeOff // only present if Tag == 'U' 82 // Underlying typeOff 83 // 84 // Methods []struct{ // omitted if Underlying is an interface type 85 // Pos Pos 86 // Name stringOff 87 // Recv Param 88 // Signature Signature 89 // } 90 // } 91 // 92 // type Alias struct { 93 // Tag byte // 'A' 94 // Pos Pos 95 // Type typeOff 96 // } 97 // 98 // // "Automatic" declaration of each typeparam 99 // type TypeParam struct { 100 // Tag byte // 'P' 101 // Pos Pos 102 // Implicit bool 103 // Constraint typeOff 104 // } 105 // 106 // typeOff means a uvarint that either indicates a predeclared type, 107 // or an offset into the Data section. If the uvarint is less than 108 // predeclReserved, then it indicates the index into the predeclared 109 // types list (see predeclared in bexport.go for order). Otherwise, 110 // subtracting predeclReserved yields the offset of a type descriptor. 111 // 112 // Value means a type, kind, and type-specific value. See 113 // (*exportWriter).value for details. 114 // 115 // 116 // There are twelve kinds of type descriptors, distinguished by an itag: 117 // 118 // type DefinedType struct { 119 // Tag itag // definedType 120 // Name stringOff 121 // PkgPath stringOff 122 // } 123 // 124 // type PointerType struct { 125 // Tag itag // pointerType 126 // Elem typeOff 127 // } 128 // 129 // type SliceType struct { 130 // Tag itag // sliceType 131 // Elem typeOff 132 // } 133 // 134 // type ArrayType struct { 135 // Tag itag // arrayType 136 // Len uint64 137 // Elem typeOff 138 // } 139 // 140 // type ChanType struct { 141 // Tag itag // chanType 142 // Dir uint64 // 1 RecvOnly; 2 SendOnly; 3 SendRecv 143 // Elem typeOff 144 // } 145 // 146 // type MapType struct { 147 // Tag itag // mapType 148 // Key typeOff 149 // Elem typeOff 150 // } 151 // 152 // type FuncType struct { 153 // Tag itag // signatureType 154 // PkgPath stringOff 155 // Signature Signature 156 // } 157 // 158 // type StructType struct { 159 // Tag itag // structType 160 // PkgPath stringOff 161 // Fields []struct { 162 // Pos Pos 163 // Name stringOff 164 // Type typeOff 165 // Embedded bool 166 // Note stringOff 167 // } 168 // } 169 // 170 // type InterfaceType struct { 171 // Tag itag // interfaceType 172 // PkgPath stringOff 173 // Embeddeds []struct { 174 // Pos Pos 175 // Type typeOff 176 // } 177 // Methods []struct { 178 // Pos Pos 179 // Name stringOff 180 // Signature Signature 181 // } 182 // } 183 // 184 // // Reference to a type param declaration 185 // type TypeParamType struct { 186 // Tag itag // typeParamType 187 // Name stringOff 188 // PkgPath stringOff 189 // } 190 // 191 // // Instantiation of a generic type (like List[T2] or List[int]) 192 // type InstanceType struct { 193 // Tag itag // instanceType 194 // Pos pos 195 // TypeArgs []typeOff 196 // BaseType typeOff 197 // } 198 // 199 // type UnionType struct { 200 // Tag itag // interfaceType 201 // Terms []struct { 202 // tilde bool 203 // Type typeOff 204 // } 205 // } 206 // 207 // 208 // 209 // type Signature struct { 210 // Params []Param 211 // Results []Param 212 // Variadic bool // omitted if Results is empty 213 // } 214 // 215 // type Param struct { 216 // Pos Pos 217 // Name stringOff 218 // Type typOff 219 // } 220 // 221 // 222 // Pos encodes a file:line:column triple, incorporating a simple delta 223 // encoding scheme within a data object. See exportWriter.pos for 224 // details. 225 // 226 // 227 // Compiler-specific details. 228 // 229 // cmd/compile writes out a second index for inline bodies and also 230 // appends additional compiler-specific details after declarations. 231 // Third-party tools are not expected to depend on these details and 232 // they're expected to change much more rapidly, so they're omitted 233 // here. See exportWriter's varExt/funcExt/etc methods for details. 234 235 package typecheck 236 237 import ( 238 "strings" 239 ) 240 241 const blankMarker = "$" 242 243 // TparamName returns the real name of a type parameter, after stripping its 244 // qualifying prefix and reverting blank-name encoding. See TparamExportName 245 // for details. 246 func TparamName(exportName string) string { 247 // Remove the "path" from the type param name that makes it unique. 248 ix := strings.LastIndex(exportName, ".") 249 if ix < 0 { 250 return "" 251 } 252 name := exportName[ix+1:] 253 if strings.HasPrefix(name, blankMarker) { 254 return "_" 255 } 256 return name 257 } 258 259 // The name used for dictionary parameters or local variables. 260 const LocalDictName = ".dict" 261