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Package filetype

v1.25.0
Latest Go to latest
Published: Jun 22, 2020 | License: BSD-3-Clause | Module: google.golang.org/protobuf

Overview

Package filetype provides functionality for wrapping descriptors with Go type information.

Index

Package Files

type Builder

type Builder struct {
	// File is the underlying file descriptor builder.
	File fdesc.Builder

	// GoTypes is a unique set of the Go types for all declarations and
	// dependencies. Each type is represented as a zero value of the Go type.
	//
	// Declarations are Go types generated for enums and messages directly
	// declared (not publicly imported) in the proto source file.
	// Messages for map entries are accounted for, but represented by nil.
	// Enum declarations in "flattened ordering" come first, followed by
	// message declarations in "flattened ordering".
	//
	// Dependencies are Go types for enums or messages referenced by
	// message fields (excluding weak fields), for parent extended messages of
	// extension fields, for enums or messages referenced by extension fields,
	// and for input and output messages referenced by service methods.
	// Dependencies must come after declarations, but the ordering of
	// dependencies themselves is unspecified.
	GoTypes []interface{}

	// DependencyIndexes is an ordered list of indexes into GoTypes for the
	// dependencies of messages, extensions, or services.
	//
	// There are 5 sub-lists in "flattened ordering" concatenated back-to-back:
	//	0. Message field dependencies: list of the enum or message type
	//	referred to by every message field.
	//	1. Extension field targets: list of the extended parent message of
	//	every extension.
	//	2. Extension field dependencies: list of the enum or message type
	//	referred to by every extension field.
	//	3. Service method inputs: list of the input message type
	//	referred to by every service method.
	//	4. Service method outputs: list of the output message type
	//	referred to by every service method.
	//
	// The offset into DependencyIndexes for the start of each sub-list
	// is appended to the end in reverse order.
	DependencyIndexes []int32

	// EnumInfos is a list of enum infos in "flattened ordering".
	EnumInfos []pimpl.EnumInfo

	// MessageInfos is a list of message infos in "flattened ordering".
	// If provided, the GoType and PBType for each element is populated.
	//
	// Requirement: len(MessageInfos) == len(Build.Messages)
	MessageInfos []pimpl.MessageInfo

	// ExtensionInfos is a list of extension infos in "flattened ordering".
	// Each element is initialized and registered with the protoregistry package.
	//
	// Requirement: len(LegacyExtensions) == len(Build.Extensions)
	ExtensionInfos []pimpl.ExtensionInfo

	// TypeRegistry is the registry to register each type descriptor.
	// If nil, it uses protoregistry.GlobalTypes.
	TypeRegistry interface {
		RegisterMessage(pref.MessageType) error
		RegisterEnum(pref.EnumType) error
		RegisterExtension(pref.ExtensionType) error
	}
}

Builder constructs type descriptors from a raw file descriptor and associated Go types for each enum and message declaration.

Flattened Ordering

The protobuf type system represents declarations as a tree. Certain nodes in the tree require us to either associate it with a concrete Go type or to resolve a dependency, which is information that must be provided separately since it cannot be derived from the file descriptor alone.

However, representing a tree as Go literals is difficult to simply do in a space and time efficient way. Thus, we store them as a flattened list of objects where the serialization order from the tree-based form is important.

The "flattened ordering" is defined as a tree traversal of all enum, message, extension, and service declarations using the following algorithm:

def VisitFileDecls(fd):
	for e in fd.Enums:      yield e
	for m in fd.Messages:   yield m
	for x in fd.Extensions: yield x
	for s in fd.Services:   yield s
	for m in fd.Messages:   yield from VisitMessageDecls(m)

def VisitMessageDecls(md):
	for e in md.Enums:      yield e
	for m in md.Messages:   yield m
	for x in md.Extensions: yield x
	for m in md.Messages:   yield from VisitMessageDecls(m)

The traversal starts at the root file descriptor and yields each direct declaration within each node before traversing into sub-declarations that children themselves may have.

func (Builder) Build

func (tb Builder) Build() (out Out)

type Out

type Out struct {
	File pref.FileDescriptor
}

Out is the output of the builder.

Documentation was rendered with GOOS=linux and GOARCH=amd64.

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