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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.
//! Definitions for describing the format protobuf messages. These can be used
//! to generate `.proto` files that are binary compatible with the associated
//! Rust types.
mod writer;
pub use writer::DescriptorWriter;
use crate::DefaultEncoding;
use std::fmt::Display;
/// A trait for a self-describing protobuf message field.
pub trait DescribeField<T> {
/// The type of the field.
const FIELD_TYPE: FieldType<'static>;
/// The type name of the field in a packed context.
const PACKED_TYPE: Option<&'static str> = None;
}
/// A trait for a self-describing protobuf message.
///
/// This can be derived for `T` by deriving [`Protobuf`](crate::Protobuf) and
/// adding the attribute `#[mesh(package = "my.package.name")]`.
pub trait DescribeMessage<T> {
/// The message description.
const DESCRIPTION: MessageDescription<'static>;
}
/// A description of a message type.
#[derive(Copy, Clone)]
pub enum MessageDescription<'a> {
/// An internally-defined type, described by the descriptor.
Internal(&'a TopLevelDescriptor<'a>),
/// An externally-defined type.
External {
/// The fully-qualified name of the message type.
name: &'a str,
/// The import path of the `.proto` file.
import_path: &'a str,
},
}
/// A type URL, used in [`ProtobufAny`](super::message::ProtobufAny) (which
/// shares an encoding with `google.protobuf.Any`).
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub struct TypeUrl<'a> {
package: &'a str,
name: &'a str,
}
impl TypeUrl<'_> {
fn eq(&self, type_url: &str) -> bool {
let type_url = type_url.strip_prefix("https://").unwrap_or(type_url);
if let Some((package, name)) = type_url
.strip_prefix("type.googleapis.com/")
.and_then(|ty| ty.rsplit_once('.'))
{
self.package == package && self.name == name
} else {
false
}
}
}
impl Display for TypeUrl<'_> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "type.googleapis.com/{}.{}", self.package, self.name)
}
}
impl PartialEq<str> for TypeUrl<'_> {
fn eq(&self, other: &str) -> bool {
self.eq(other)
}
}
impl PartialEq<TypeUrl<'_>> for str {
fn eq(&self, other: &TypeUrl<'_>) -> bool {
other.eq(self)
}
}
impl MessageDescription<'_> {
/// Returns the type URL to use with `google.protobuf.Any`.
pub const fn type_url(&self) -> TypeUrl<'_> {
match *self {
MessageDescription::Internal(tld) => TypeUrl {
package: tld.package,
name: tld.message.name,
},
MessageDescription::External { name, .. } => TypeUrl { package: "", name },
}
}
}
/// Returns the top-level message descriptor for a type with a default encoding.
pub const fn message_description<T: DefaultEncoding>() -> MessageDescription<'static>
where
T::Encoding: DescribeMessage<T>,
{
<T::Encoding as DescribeMessage<T>>::DESCRIPTION
}
/// The description of a field type.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct FieldType<'a> {
kind: FieldKind<'a>,
sequence_type: Option<SequenceType<'a>>,
annotation: &'a str,
}
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
enum SequenceType<'a> {
Optional,
Repeated,
Map(&'a str),
}
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
enum FieldKind<'a> {
Builtin(&'a str),
Local(&'a str),
External {
name: &'a str,
import_path: &'static str,
},
Message(fn() -> MessageDescription<'a>),
Tuple(&'a [FieldType<'a>]),
KeyValue(&'a [FieldType<'a>; 2]),
}
impl<'a> FieldType<'a> {
/// Returns a repeated version of this field type.
///
/// Panics if the field type is already a sequence type.
pub const fn repeated(mut self) -> Self {
assert!(self.sequence_type.is_none());
self.sequence_type = Some(SequenceType::Repeated);
self
}
/// Returns a optional version of this field type.
///
/// Panics if the field type is already a sequence type.
pub const fn optional(mut self) -> Self {
assert!(self.sequence_type.is_none());
self.sequence_type = Some(SequenceType::Optional);
self
}
/// Sets an annotation to show up in the .proto file.
pub const fn annotate(mut self, annotation: &'a str) -> Self {
self.annotation = annotation;
self
}
/// Returns a map type.
///
/// If `key` is not a builtin numeric scalar or string type, or if `value`
/// is an optional or repeated type, then this will result in a repeated
/// tuple instead of a protobuf `map` type. The encodings for these are the
/// same, but `.proto` `map` types are constrained to mappings from scalars
/// to non-optional/repeated scalars and messages.
pub const fn map(kv: &'a [FieldType<'a>; 2]) -> Self {
let [key, value] = kv;
if !key.is_sequence() && !value.is_sequence() {
if let FieldKind::Builtin(ty) = key.kind {
if let b"uint32" | b"int32" | b"sint32" | b"uint64" | b"sint64" | b"int64"
| b"fixed32" | b"fixed64" | b"sfixed32" | b"sfixed64" | b"bool" | b"string" =
ty.as_bytes()
{
return Self {
kind: value.kind,
sequence_type: Some(SequenceType::Map(ty)),
annotation: "",
};
}
}
}
Self {
kind: FieldKind::KeyValue(kv),
sequence_type: Some(SequenceType::Repeated),
annotation: "",
}
}
/// Returns a field type for a message whose top-level descriptor is
/// returned by `f`.
///
/// This is abstracted through a function to allow for recursive types.
/// Currently Rust does not allow a `const` to refer to a `static`, but it
/// does allow a `const` to refer to a function that returns a `&'static`.
pub const fn message(f: fn() -> MessageDescription<'a>) -> Self {
Self {
kind: FieldKind::Message(f),
sequence_type: None,
annotation: "",
}
}
/// Returns a field type for a local message type with `name`.
pub const fn local(name: &'a str) -> Self {
Self {
kind: FieldKind::Local(name),
sequence_type: None,
annotation: "",
}
}
/// Returns a field type for a builtin type, such as `uint32`.
pub const fn builtin(name: &'a str) -> Self {
Self {
kind: FieldKind::Builtin(name),
sequence_type: None,
annotation: "",
}
}
/// Returns a field type for an anonymous tuple.
#[allow(clippy::redundant_guards)] // https://github.com/rust-lang/rust-clippy/issues/12243
pub const fn tuple(field_types: &'a [Self]) -> Self {
// Use well-known types instead of new anonymous ones when possible.
match field_types {
[] => {
return Self::external("google.protobuf.Empty", "google/protobuf/empty.proto");
}
&[Self {
kind: FieldKind::Builtin(ty),
sequence_type: None,
annotation,
}] if annotation.is_empty() => {
let wrapper = match ty.as_bytes() {
b"double" => Some("google.protobuf.DoubleValue"),
b"float" => Some("google.protobuf.FloatValue"),
b"int64" => Some("google.protobuf.Int64Value"),
b"uint64" => Some("google.protobuf.UInt64Value"),
b"int32" => Some("google.protobuf.Int32Value"),
b"uint32" => Some("google.protobuf.UInt32Value"),
b"bool" => Some("google.protobuf.BoolValue"),
b"string" => Some("google.protobuf.StringValue"),
b"bytes" => Some("google.protobuf.BytesValue"),
_ => None,
};
if let Some(wrapper) = wrapper {
return Self::external(wrapper, "google/protobuf/wrappers.proto");
}
}
_ => {}
}
Self {
kind: FieldKind::Tuple(field_types),
sequence_type: None,
annotation: "",
}
}
/// Returns a field type for an external type with the given fully-qualified
/// name and protoc import path.
pub const fn external(name: &'a str, import_path: &'static str) -> Self {
Self {
kind: FieldKind::External { name, import_path },
sequence_type: None,
annotation: "",
}
}
/// Returns true if this is a sequence type (optional or repeated).
pub const fn is_sequence(&self) -> bool {
self.sequence_type.is_some()
}
/// Returns true if this type can use a packed encoding in a repeated
/// context.
pub const fn can_pack(&self) -> bool {
if self.sequence_type.is_some() {
return false;
}
match self.kind {
FieldKind::Builtin(v) => matches!(
v.as_bytes(),
b"double" | b"float" | b"int64" | b"uint64" | b"int32" | b"uint32" | b"bool"
),
_ => false,
}
}
}
/// A descriptor for a message field.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct FieldDescriptor<'a> {
field_type: FieldType<'a>,
field_number: u32,
comment: &'a str,
name: &'a str,
}
impl<'a> FieldDescriptor<'a> {
/// Returns a new descriptor.
pub const fn new(
comment: &'a str,
field_type: FieldType<'a>,
name: &'a str,
field_number: u32,
) -> Self {
Self {
field_type,
field_number,
comment,
name,
}
}
}
/// A description of a protobuf `oneof`.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct OneofDescriptor<'a> {
name: &'a str,
variants: &'a [FieldDescriptor<'a>],
}
impl<'a> OneofDescriptor<'a> {
/// Returns a new descriptor.
pub const fn new(name: &'a str, variants: &'a [FieldDescriptor<'a>]) -> Self {
Self { name, variants }
}
}
/// A message descriptor.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct MessageDescriptor<'a> {
comment: &'a str,
name: &'a str,
fields: &'a [FieldDescriptor<'a>],
oneofs: &'a [OneofDescriptor<'a>],
messages: &'a [MessageDescriptor<'a>],
}
impl<'a> MessageDescriptor<'a> {
/// Creates a new message descriptor.
pub const fn new(
name: &'a str,
comment: &'a str,
fields: &'a [FieldDescriptor<'a>],
oneofs: &'a [OneofDescriptor<'a>],
messages: &'a [MessageDescriptor<'a>],
) -> Self {
Self {
comment,
name,
fields,
oneofs,
messages,
}
}
}
/// A message descriptor for a message rooted directly in a package (and not
/// nested in another message type).
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct TopLevelDescriptor<'a> {
package: &'a str,
message: &'a MessageDescriptor<'a>,
}
impl<'a> TopLevelDescriptor<'a> {
/// Returns a new descriptor.
pub const fn message(package: &'a str, message: &'a MessageDescriptor<'a>) -> Self {
Self { package, message }
}
}