diff --git a/internal/gcimporter/iexport.go b/internal/gcimporter/iexport.go index deeb67f315a..085e4ce4155 100644 --- a/internal/gcimporter/iexport.go +++ b/internal/gcimporter/iexport.go @@ -2,9 +2,227 @@ // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. -// Indexed binary package export. -// This file was derived from $GOROOT/src/cmd/compile/internal/gc/iexport.go; -// see that file for specification of the format. +// Indexed package export. +// +// The indexed export data format is an evolution of the previous +// binary export data format. Its chief contribution is introducing an +// index table, which allows efficient random access of individual +// declarations and inline function bodies. In turn, this allows +// avoiding unnecessary work for compilation units that import large +// packages. +// +// +// The top-level data format is structured as: +// +// Header struct { +// Tag byte // 'i' +// Version uvarint +// StringSize uvarint +// DataSize uvarint +// } +// +// Strings [StringSize]byte +// Data [DataSize]byte +// +// MainIndex []struct{ +// PkgPath stringOff +// PkgName stringOff +// PkgHeight uvarint +// +// Decls []struct{ +// Name stringOff +// Offset declOff +// } +// } +// +// Fingerprint [8]byte +// +// uvarint means a uint64 written out using uvarint encoding. +// +// []T means a uvarint followed by that many T objects. In other +// words: +// +// Len uvarint +// Elems [Len]T +// +// stringOff means a uvarint that indicates an offset within the +// Strings section. At that offset is another uvarint, followed by +// that many bytes, which form the string value. +// +// declOff means a uvarint that indicates an offset within the Data +// section where the associated declaration can be found. +// +// +// There are five kinds of declarations, distinguished by their first +// byte: +// +// type Var struct { +// Tag byte // 'V' +// Pos Pos +// Type typeOff +// } +// +// type Func struct { +// Tag byte // 'F' or 'G' +// Pos Pos +// TypeParams []typeOff // only present if Tag == 'G' +// Signature Signature +// } +// +// type Const struct { +// Tag byte // 'C' +// Pos Pos +// Value Value +// } +// +// type Type struct { +// Tag byte // 'T' or 'U' +// Pos Pos +// TypeParams []typeOff // only present if Tag == 'U' +// Underlying typeOff +// +// Methods []struct{ // omitted if Underlying is an interface type +// Pos Pos +// Name stringOff +// Recv Param +// Signature Signature +// } +// } +// +// type Alias struct { +// Tag byte // 'A' or 'B' +// Pos Pos +// TypeParams []typeOff // only present if Tag == 'B' +// Type typeOff +// } +// +// // "Automatic" declaration of each typeparam +// type TypeParam struct { +// Tag byte // 'P' +// Pos Pos +// Implicit bool +// Constraint typeOff +// } +// +// typeOff means a uvarint that either indicates a predeclared type, +// or an offset into the Data section. If the uvarint is less than +// predeclReserved, then it indicates the index into the predeclared +// types list (see predeclared in bexport.go for order). Otherwise, +// subtracting predeclReserved yields the offset of a type descriptor. +// +// Value means a type, kind, and type-specific value. See +// (*exportWriter).value for details. +// +// +// There are twelve kinds of type descriptors, distinguished by an itag: +// +// type DefinedType struct { +// Tag itag // definedType +// Name stringOff +// PkgPath stringOff +// } +// +// type PointerType struct { +// Tag itag // pointerType +// Elem typeOff +// } +// +// type SliceType struct { +// Tag itag // sliceType +// Elem typeOff +// } +// +// type ArrayType struct { +// Tag itag // arrayType +// Len uint64 +// Elem typeOff +// } +// +// type ChanType struct { +// Tag itag // chanType +// Dir uint64 // 1 RecvOnly; 2 SendOnly; 3 SendRecv +// Elem typeOff +// } +// +// type MapType struct { +// Tag itag // mapType +// Key typeOff +// Elem typeOff +// } +// +// type FuncType struct { +// Tag itag // signatureType +// PkgPath stringOff +// Signature Signature +// } +// +// type StructType struct { +// Tag itag // structType +// PkgPath stringOff +// Fields []struct { +// Pos Pos +// Name stringOff +// Type typeOff +// Embedded bool +// Note stringOff +// } +// } +// +// type InterfaceType struct { +// Tag itag // interfaceType +// PkgPath stringOff +// Embeddeds []struct { +// Pos Pos +// Type typeOff +// } +// Methods []struct { +// Pos Pos +// Name stringOff +// Signature Signature +// } +// } +// +// // Reference to a type param declaration +// type TypeParamType struct { +// Tag itag // typeParamType +// Name stringOff +// PkgPath stringOff +// } +// +// // Instantiation of a generic type (like List[T2] or List[int]) +// type InstanceType struct { +// Tag itag // instanceType +// Pos pos +// TypeArgs []typeOff +// BaseType typeOff +// } +// +// type UnionType struct { +// Tag itag // interfaceType +// Terms []struct { +// tilde bool +// Type typeOff +// } +// } +// +// +// +// type Signature struct { +// Params []Param +// Results []Param +// Variadic bool // omitted if Results is empty +// } +// +// type Param struct { +// Pos Pos +// Name stringOff +// Type typOff +// } +// +// +// Pos encodes a file:line:column triple, incorporating a simple delta +// encoding scheme within a data object. See exportWriter.pos for +// details. package gcimporter diff --git a/internal/gcimporter/iimport.go b/internal/gcimporter/iimport.go index 136aa03653c..01c4023e2af 100644 --- a/internal/gcimporter/iimport.go +++ b/internal/gcimporter/iimport.go @@ -3,7 +3,7 @@ // license that can be found in the LICENSE file. // Indexed package import. -// See cmd/compile/internal/gc/iexport.go for the export data format. +// See iexport.go for the export data format. // This file is a copy of $GOROOT/src/go/internal/gcimporter/iimport.go.