Documentation

Overview

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

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

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.

Source Files