pkgbits

package pkgbits

import "internal/pkgbits"

Package pkgbits implements low-level coding abstractions for Unified IR's (UIR) binary export data format.

At a low-level, the exported objects of a package are encoded as a byte array. This array contains byte representations of primitive, potentially variable-length values, such as integers, booleans, strings, and constants.

Additionally, the array may contain values which denote indices in the byte array itself. These are termed "relocations" and allow for references.

The details of mapping high-level Go constructs to primitives are left to other packages.

Index

type AbsElemIdx
type Code
type CodeObj
- func (c CodeObj) Marker() SyncMarker
- func (c CodeObj) Value() int
type CodeType
- func (c CodeType) Marker() SyncMarker
- func (c CodeType) Value() int
type CodeVal
- func (c CodeVal) Marker() SyncMarker
- func (c CodeVal) Value() int
type Decoder
type Encoder
type Field
type Index
type PkgDecoder
type PkgEncoder
type RefTableEntry
type RelElemIdx
type SectionKind
type SyncMarker
- func (i SyncMarker) String() string
type Version
- func (v Version) Has(f Field) bool

Types

type AbsElemIdx

type AbsElemIdx = uint32

An AbsElemIdx, or absolute element index, is an index into the elements that is not relative to some other index.

type Code

type Code interface {
	// Marker returns the SyncMarker for the Code's dynamic type.
	Marker() SyncMarker

	// Value returns the Code's ordinal value.
	Value() int
}

A Code is an enum value that can be encoded into bitstreams.

Code types are preferable for enum types, because they allow Decoder to detect desyncs.

type CodeObj

type CodeObj int

A CodeObj distinguishes among go/types.Object encodings.

const (
	ObjAlias CodeObj = iota
	ObjConst
	ObjType
	ObjFunc
	ObjVar
	ObjStub
)

func (CodeObj) Marker

func (c CodeObj) Marker() SyncMarker

func (CodeObj) Value

func (c CodeObj) Value() int

type CodeType

type CodeType int

A CodeType distinguishes among go/types.Type encodings.

const (
	TypeBasic CodeType = iota
	TypeNamed
	TypePointer
	TypeSlice
	TypeArray
	TypeChan
	TypeMap
	TypeSignature
	TypeStruct
	TypeInterface
	TypeUnion
	TypeTypeParam
)

func (CodeType) Marker

func (c CodeType) Marker() SyncMarker

func (CodeType) Value

func (c CodeType) Value() int

type CodeVal

type CodeVal int

A CodeVal distinguishes among go/constant.Value encodings.

const (
	ValBool CodeVal = iota
	ValString
	ValInt64
	ValBigInt
	ValBigRat
	ValBigFloat
)

func (CodeVal) Marker

func (c CodeVal) Marker() SyncMarker

func (CodeVal) Value

func (c CodeVal) Value() int

type Decoder

type Decoder struct {
	Relocs []RefTableEntry
	Data   strings.Reader

	Idx RelElemIdx
	// contains filtered or unexported fields
}

A Decoder provides methods for decoding an individual element's bitstream data.

func (*Decoder) Bool

func (r *Decoder) Bool() bool

Bool decodes and returns a bool value from the element bitstream.

func (*Decoder) Code

func (r *Decoder) Code(mark SyncMarker) int

Code decodes a Code value from the element bitstream and returns its ordinal value. It's the caller's responsibility to convert the result to an appropriate Code type.

TODO(mdempsky): Ideally this method would have signature "Code[T Code] T" instead, but we don't allow generic methods and the compiler can't depend on generics yet anyway.

func (*Decoder) Int

func (r *Decoder) Int() int

Int decodes and returns an int value from the element bitstream.

func (*Decoder) Int64

func (r *Decoder) Int64() int64

Int64 decodes and returns an int64 value from the element bitstream.

func (*Decoder) Len

func (r *Decoder) Len() int

Len decodes and returns a non-negative int value from the element bitstream.

func (*Decoder) Reloc

func (r *Decoder) Reloc(k SectionKind) RelElemIdx

Reloc decodes a relocation of expected section k from the element bitstream and returns an index to the referenced element.

func (*Decoder) String

func (r *Decoder) String() string

String decodes and returns a string value from the element bitstream.

func (*Decoder) Strings

func (r *Decoder) Strings() []string

Strings decodes and returns a variable-length slice of strings from the element bitstream.

func (*Decoder) Sync

func (r *Decoder) Sync(mWant SyncMarker)

Sync decodes a sync marker from the element bitstream and asserts that it matches the expected marker.

If EnableSync is false, then Sync is a no-op.

func (*Decoder) Uint

func (r *Decoder) Uint() uint

Uint decodes and returns a uint value from the element bitstream.

func (*Decoder) Uint64

func (r *Decoder) Uint64() uint64

Uint64 decodes and returns a uint64 value from the element bitstream.

func (*Decoder) Value

func (r *Decoder) Value() constant.Value

Value decodes and returns a constant.Value from the element bitstream.

func (*Decoder) Version

func (w *Decoder) Version() Version

Version reports the version of the bitstream.

type Encoder

type Encoder struct {
	Relocs   []RefTableEntry
	RelocMap map[RefTableEntry]uint32
	Data     bytes.Buffer // accumulated element bitstream data

	Idx RelElemIdx // index within relocation section
	// contains filtered or unexported fields
}

An Encoder provides methods for encoding an individual element's bitstream data.

func (*Encoder) Bool

func (w *Encoder) Bool(b bool) bool

Bool encodes and writes a bool value into the element bitstream, and then returns the bool value.

For simple, 2-alternative encodings, the idiomatic way to call Bool is something like:

if w.Bool(x != 0) {
	// alternative #1
} else {
	// alternative #2
}

For multi-alternative encodings, use Code instead.

func (*Encoder) Code

func (w *Encoder) Code(c Code)

Code encodes and writes a Code value into the element bitstream.

func (*Encoder) Flush

func (w *Encoder) Flush() RelElemIdx

Flush finalizes the element's bitstream and returns its RelElemIdx.

func (*Encoder) Int

func (w *Encoder) Int(x int)

Int encodes and writes an int value into the element bitstream.

func (*Encoder) Int64

func (w *Encoder) Int64(x int64)

Int64 encodes and writes an int64 value into the element bitstream.

func (*Encoder) Len

func (w *Encoder) Len(x int)

Len encodes and writes a non-negative int value into the element bitstream.

func (*Encoder) Reloc

func (w *Encoder) Reloc(k SectionKind, idx RelElemIdx)

Reloc encodes and writes a relocation for the given (section, index) pair into the element bitstream.

Note: Only the index is formally written into the element bitstream, so bitstream decoders must know from context which section an encoded relocation refers to.

func (*Encoder) String

func (w *Encoder) String(s string)

String encodes and writes a string value into the element bitstream.

Internally, strings are deduplicated by adding them to the strings section (if not already present), and then writing a relocation into the element bitstream.

func (*Encoder) StringRef

func (w *Encoder) StringRef(idx RelElemIdx)

StringRef writes a reference to the given index, which must be a previously encoded string value.

func (*Encoder) Strings

func (w *Encoder) Strings(ss []string)

Strings encodes and writes a variable-length slice of strings into the element bitstream.

func (*Encoder) Sync

func (w *Encoder) Sync(m SyncMarker)

func (*Encoder) Uint

func (w *Encoder) Uint(x uint)

Uint encodes and writes a uint value into the element bitstream.

func (*Encoder) Uint64

func (w *Encoder) Uint64(x uint64)

Uint64 encodes and writes a uint64 value into the element bitstream.

func (*Encoder) Value

func (w *Encoder) Value(val constant.Value)

Value encodes and writes a constant.Value into the element bitstream.

func (*Encoder) Version

func (w *Encoder) Version() Version

Version reports the version of the bitstream.

type Field

type Field int

Field denotes a unit of data in the serialized unified IR bitstream. It is conceptually a like field in a structure.

We only really need Fields when the data may or may not be present in a stream based on the Version of the bitstream.

Unlike much of pkgbits, Fields are not serialized and can change values as needed.

const (
	// Flags in a uint32 in the header of a bitstream
	// that is used to indicate whether optional features are enabled.
	Flags Field = iota

	// Deprecated: HasInit was a bool indicating whether a package
	// has any init functions.
	HasInit

	// Deprecated: DerivedFuncInstance was a bool indicating
	// whether an object was a function instance.
	DerivedFuncInstance

	// ObjAlias has a list of TypeParamNames.
	AliasTypeParamNames

	// Deprecated: DerivedInfoNeeded was a bool indicating
	// whether a type was a derived type.
	DerivedInfoNeeded
)

type Index

type Index int32

An Index represents a bitstream element index *within* (i.e., relative to) a particular section.

type PkgDecoder

type PkgDecoder struct {
	// contains filtered or unexported fields
}

A PkgDecoder provides methods for decoding a package's Unified IR export data.

func NewPkgDecoder

func NewPkgDecoder(pkgPath, input string) PkgDecoder

NewPkgDecoder returns a PkgDecoder initialized to read the Unified IR export data from input. pkgPath is the package path for the compilation unit that produced the export data.

func (*PkgDecoder) AbsIdx

func (pr *PkgDecoder) AbsIdx(k SectionKind, idx RelElemIdx) int

AbsIdx returns the absolute index for the given (section, index) pair.

func (*PkgDecoder) DataIdx

func (pr *PkgDecoder) DataIdx(k SectionKind, idx RelElemIdx) string

DataIdx returns the raw element bitstream for the given (section, index) pair.

func (*PkgDecoder) Fingerprint

func (pr *PkgDecoder) Fingerprint() [8]byte

Fingerprint returns the package fingerprint.

func (*PkgDecoder) NewDecoder

func (pr *PkgDecoder) NewDecoder(k SectionKind, idx RelElemIdx, marker SyncMarker) Decoder

NewDecoder returns a Decoder for the given (section, index) pair, and decodes the given SyncMarker from the element bitstream.

func (*PkgDecoder) NewDecoderRaw

func (pr *PkgDecoder) NewDecoderRaw(k SectionKind, idx RelElemIdx) Decoder

NewDecoderRaw returns a Decoder for the given (section, index) pair.

Most callers should use NewDecoder instead.

func (*PkgDecoder) NumElems

func (pr *PkgDecoder) NumElems(k SectionKind) int

NumElems returns the number of elements in section k.

func (*PkgDecoder) PeekObj

func (pr *PkgDecoder) PeekObj(idx RelElemIdx) (string, string, CodeObj)

PeekObj returns the package path, object name, and CodeObj for the specified object index.

func (*PkgDecoder) PeekPkgPath

func (pr *PkgDecoder) PeekPkgPath(idx RelElemIdx) string

PeekPkgPath returns the package path for the specified package index.

func (*PkgDecoder) PkgPath

func (pr *PkgDecoder) PkgPath() string

PkgPath returns the package path for the package

TODO(mdempsky): Remove; unneeded since CL 391014.

func (*PkgDecoder) RetireDecoder

func (pr *PkgDecoder) RetireDecoder(d *Decoder)

func (*PkgDecoder) StringIdx

func (pr *PkgDecoder) StringIdx(idx RelElemIdx) string

StringIdx returns the string value for the given string index.

func (*PkgDecoder) SyncMarkers

func (pr *PkgDecoder) SyncMarkers() bool

SyncMarkers reports whether pr uses sync markers.

func (*PkgDecoder) TempDecoder

func (pr *PkgDecoder) TempDecoder(k SectionKind, idx RelElemIdx, marker SyncMarker) Decoder

TempDecoder returns a Decoder for the given (section, index) pair, and decodes the given SyncMarker from the element bitstream. If possible the Decoder should be RetireDecoder'd when it is no longer needed, this will avoid heap allocations.

func (*PkgDecoder) TempDecoderRaw

func (pr *PkgDecoder) TempDecoderRaw(k SectionKind, idx RelElemIdx) Decoder

func (*PkgDecoder) TotalElems

func (pr *PkgDecoder) TotalElems() int

TotalElems returns the total number of elements across all sections.

type PkgEncoder

type PkgEncoder struct {
	// contains filtered or unexported fields
}

A PkgEncoder provides methods for encoding a package's Unified IR export data.

func NewPkgEncoder

func NewPkgEncoder(version Version, syncFrames int) PkgEncoder

NewPkgEncoder returns an initialized PkgEncoder.

syncFrames is the number of caller frames that should be serialized at Sync points. Serializing additional frames results in larger export data files, but can help diagnosing desync errors in higher-level Unified IR reader/writer code. If syncFrames is negative, then sync markers are omitted entirely.

func (*PkgEncoder) DumpTo

func (pw *PkgEncoder) DumpTo(out0 io.Writer) (fingerprint [8]byte)

DumpTo writes the package's encoded data to out0 and returns the package fingerprint.

func (*PkgEncoder) NewEncoder

func (pw *PkgEncoder) NewEncoder(k SectionKind, marker SyncMarker) *Encoder

NewEncoder returns an Encoder for a new element within the given section, and encodes the given SyncMarker as the start of the element bitstream.

func (*PkgEncoder) NewEncoderRaw

func (pw *PkgEncoder) NewEncoderRaw(k SectionKind) *Encoder

NewEncoderRaw returns an Encoder for a new element within the given section.

Most callers should use NewEncoder instead.

func (*PkgEncoder) StringIdx

func (pw *PkgEncoder) StringIdx(s string) RelElemIdx

StringIdx adds a string value to the strings section, if not already present, and returns its index.

func (*PkgEncoder) SyncMarkers

func (pw *PkgEncoder) SyncMarkers() bool

SyncMarkers reports whether pw uses sync markers.

type RefTableEntry

type RefTableEntry struct {
	Kind SectionKind
	Idx  RelElemIdx
}

A RefTableEntry is an entry in an element's reference table. All elements are preceded by a reference table which provides locations for referenced elements.

type RelElemIdx

type RelElemIdx = Index

TODO(markfreeman): Make this its own type. A RelElemIdx, or relative element index, is an index into the elements relative to some other index, such as the start of a section.

const (
	PublicRootIdx  RelElemIdx = 0
	PrivateRootIdx RelElemIdx = 1
)

Reserved indices within the SectionMeta section.

type SectionKind

type SectionKind int32 // TODO(markfreeman): Replace with uint8.

A SectionKind indicates a section, as well as the ordering of sections within unified export data. Any object given a dedicated section can be referred to via a section / index pair (and thus dereferenced) in other sections.

const (
	SectionString SectionKind = iota
	SectionMeta
	SectionPosBase
	SectionPkg
	SectionName
	SectionType
	SectionObj
	SectionObjExt
	SectionObjDict
	SectionBody
)

type SyncMarker

type SyncMarker int

SyncMarker is an enum type that represents markers that may be written to export data to ensure the reader and writer stay synchronized.

const (

	// Low-level coding markers.
	SyncEOF SyncMarker
	SyncBool
	SyncInt64
	SyncUint64
	SyncString
	SyncValue
	SyncVal
	SyncRelocs
	SyncReloc
	SyncUseReloc

	// Higher-level object and type markers.
	SyncPublic
	SyncPos
	SyncPosBase
	SyncObject
	SyncObject1
	SyncPkg
	SyncPkgDef
	SyncMethod
	SyncType
	SyncTypeIdx
	SyncTypeParamNames
	SyncSignature
	SyncParams
	SyncParam
	SyncCodeObj
	SyncSym
	SyncLocalIdent
	SyncSelector

	// Private markers (only known to cmd/compile).
	SyncPrivate

	SyncFuncExt
	SyncVarExt
	SyncTypeExt
	SyncPragma

	SyncExprList
	SyncExprs
	SyncExpr
	SyncExprType
	SyncAssign
	SyncOp
	SyncFuncLit
	SyncCompLit

	SyncDecl
	SyncFuncBody
	SyncOpenScope
	SyncCloseScope
	SyncCloseAnotherScope
	SyncDeclNames
	SyncDeclName

	SyncStmts
	SyncBlockStmt
	SyncIfStmt
	SyncForStmt
	SyncSwitchStmt
	SyncRangeStmt
	SyncCaseClause
	SyncCommClause
	SyncSelectStmt
	SyncDecls
	SyncLabeledStmt
	SyncUseObjLocal
	SyncAddLocal
	SyncLinkname
	SyncStmt1
	SyncStmtsEnd
	SyncLabel
	SyncOptLabel

	SyncMultiExpr
	SyncRType
	SyncConvRTTI
)

func (SyncMarker) String

func (i SyncMarker) String() string

type Version

type Version uint32

Version indicates a version of a unified IR bitstream. Each Version indicates the addition, removal, or change of new data in the bitstream.

These are serialized to disk and the interpretation remains fixed.

const (
	// V0: initial prototype.
	//
	// All data that is not assigned a Field is in version V0
	// and has not been deprecated.
	V0 Version = iota

	// V1: adds the Flags uint32 word
	V1

	// V2: removes unused legacy fields and supports type parameters for aliases.
	// - remove the legacy "has init" bool from the public root
	// - remove obj's "derived func instance" bool
	// - add a TypeParamNames field to ObjAlias
	// - remove derived info "needed" bool
	V2
)

func (Version) Has

func (v Version) Has(f Field) bool

Has reports whether field f is present in a bitstream at version v.