First steps of C++ codegen

crates/re_types/build.rs

@@ -18,6 +18,7 @@ const SOURCE_HASH_PATH: &str = "./source_hash.txt";
 const DEFINITIONS_DIR_PATH: &str = "./definitions";
 const ENTRYPOINT_PATH: &str = "./definitions/rerun/archetypes.fbs";
 const DOC_EXAMPLES_DIR_PATH: &str = "../../docs/code-examples";
+const CPP_OUTPUT_DIR_PATH: &str = "../../rerun_cpp/src";
 const RUST_OUTPUT_DIR_PATH: &str = ".";
 const PYTHON_OUTPUT_DIR_PATH: &str = "../../rerun_py/rerun_sdk/rerun/_rerun2";
 
@@ -106,6 +107,8 @@ fn main() {
     let (objects, arrow_registry) =
         re_types_builder::generate_lang_agnostic(DEFINITIONS_DIR_PATH, ENTRYPOINT_PATH);
 
+    re_types_builder::generate_cpp_code(CPP_OUTPUT_DIR_PATH, &objects, &arrow_registry);
+
     re_types_builder::generate_rust_code(RUST_OUTPUT_DIR_PATH, &objects, &arrow_registry);
 
     // We need to run `cago fmt` several times because it is not idempotent!

crates/re_types/source_hash.txt

@@ -1,4 +1,4 @@
 # This is a sha256 hash for all direct and indirect dependencies of this crate's build script.
 # It can be safely removed at anytime to force the build script to run again.
 # Check out build.rs to see how it's computed.
-79a77e7e24972298df0817e449fb2fda1a8a8de96ef269b4e58dabf1262062fd
+61313d55df25b523cddc1555e2f92d7c75f18d55e43706cdf8ac0da898fdb22f

crates/re_types_builder/Cargo.toml

@@ -23,6 +23,7 @@ all-features = true
 anyhow.workspace = true
 arrow2.workspace = true
 camino.workspace = true
+clang-format = "0.1"
 convert_case = "0.6"
 flatbuffers = "23.0"
 indent = "0.1"

crates/re_types_builder/src/codegen/cpp.rs

@@ -0,0 +1,144 @@
+use std::collections::BTreeSet;
+
+use anyhow::Context as _;
+use camino::Utf8PathBuf;
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+
+use crate::{codegen::AUTOGEN_WARNING, ArrowRegistry, Object, ObjectKind, Objects};
+
+const NEWLINE_TOKEN: &str = "RE_TOKEN_NEWLINE";
+
+pub struct CppCodeGenerator {
+    output_path: Utf8PathBuf,
+}
+
+impl CppCodeGenerator {
+    pub fn new(output_path: impl Into<Utf8PathBuf>) -> Self {
+        Self {
+            output_path: output_path.into(),
+        }
+    }
+
+    fn generate_folder(
+        &mut self,
+        objects: &Objects,
+        arrow_registry: &ArrowRegistry,
+        object_kind: ObjectKind,
+        folder_name: &str,
+    ) -> BTreeSet<Utf8PathBuf> {
+        let mut filepaths = BTreeSet::default();
+
+        let folder_path = self.output_path.join(folder_name);
+        std::fs::create_dir_all(&folder_path)
+            .with_context(|| format!("{folder_path:?}"))
+            .unwrap();
+        for obj in objects.ordered_objects(object_kind.into()) {
+            let filename = obj.snake_case_name();
+            let (hpp, cpp) = generate_hpp_cpp(objects, arrow_registry, obj);
+            for (extension, tokens) in [("hpp", hpp), ("cpp", cpp)] {
+                let string = string_from_token_stream(obj, &tokens);
+                let filepath = folder_path.join(format!("{filename}.{extension}"));
+                write_file(&filepath, string);
+                filepaths.insert(filepath);
+            }
+        }
+
+        // Clean up old files:
+        for entry in std::fs::read_dir(folder_path).unwrap().flatten() {
+            let filepath = Utf8PathBuf::try_from(entry.path()).unwrap();
+            if !filepaths.contains(&filepath) {
+                std::fs::remove_file(filepath).ok();
+            }
+        }
+
+        filepaths
+    }
+}
+
+impl crate::CodeGenerator for CppCodeGenerator {
+    fn generate(
+        &mut self,
+        objects: &Objects,
+        arrow_registry: &ArrowRegistry,
+    ) -> BTreeSet<Utf8PathBuf> {
+        let mut filepaths = BTreeSet::new();
+
+        for object_kind in ObjectKind::ALL {
+            let folder_name = object_kind.plural_snake_case();
+            filepaths.extend(self.generate_folder(
+                objects,
+                arrow_registry,
+                object_kind,
+                folder_name,
+            ));
+        }
+
+        filepaths
+    }
+}
+
+fn string_from_token_stream(obj: &Object, token_stream: &TokenStream) -> String {
+    let mut code = String::new();
+    code.push_str(&format!("// {AUTOGEN_WARNING}\n"));
+    if let Some(relative_path) = obj.relative_filepath() {
+        code.push_str(&format!("// Based on {relative_path:?}"));
+    }
+
+    code.push('\n');
+    code.push_str(
+        &token_stream
+            .to_string()
+            .replace(&format!("{NEWLINE_TOKEN:?}"), "\n"),
+    );
+    code.push('\n');
+
+    // clang_format has a bit of an ugly API: https://github.com/KDAB/clang-format-rs/issues/3
+    clang_format::CLANG_FORMAT_STYLE
+        .set(clang_format::ClangFormatStyle::File)
+        .ok();
+    code = clang_format::clang_format(&code).expect("Failed to run clang-format");
+
+    code
+}
+
+fn write_file(filepath: &Utf8PathBuf, code: String) {
+    if let Ok(existing) = std::fs::read_to_string(filepath) {
+        if existing == code {
+            // Don't touch the timestamp unnecessarily
+            return;
+        }
+    }
+
+    std::fs::write(filepath, code)
+        .with_context(|| format!("{filepath}"))
+        .unwrap();
+}
+
+fn generate_hpp_cpp(
+    _objects: &Objects,
+    _arrow_registry: &ArrowRegistry,
+    obj: &crate::Object,
+) -> (TokenStream, TokenStream) {
+    let obj_kind_ident = format_ident!("{}", obj.kind.plural_snake_case());
+
+    let pascal_case_name = &obj.name;
+    let pascal_case_ident = format_ident!("{pascal_case_name}");
+    let snake_case_name = obj.snake_case_name();
+
+    let hash = quote! { # };
+    let header_file_name = format!("{snake_case_name}.hpp");
+
+    let hpp = quote! {
+        #hash pragma once #NEWLINE_TOKEN #NEWLINE_TOKEN
+
+        namespace rr {
+            namespace #obj_kind_ident {
+                struct #pascal_case_ident { };
+            }
+        }
+    };
+    let cpp = quote! { #hash include #header_file_name };
+
+    (hpp, cpp)
+}

crates/re_types_builder/src/codegen/mod.rs

@@ -20,8 +20,10 @@ pub const AUTOGEN_WARNING: &str =
 mod common;
 use self::common::{get_documentation, StringExt};
 
+mod cpp;
 mod python;
 mod rust;
 
+pub use self::cpp::CppCodeGenerator;
 pub use self::python::PythonCodeGenerator;
 pub use self::rust::RustCodeGenerator;

crates/re_types_builder/src/codegen/python.rs

@@ -92,7 +92,7 @@ impl CodeGenerator for PythonCodeGenerator {
     ) -> BTreeSet<Utf8PathBuf> {
         let mut filepaths = BTreeSet::new();
 
-        let datatypes_path = self.pkg_path.join("datatypes");
+        let datatypes_path = self.pkg_path.join(ObjectKind::Datatype.plural_snake_case());
         let datatype_overrides = load_overrides(&datatypes_path);
         std::fs::create_dir_all(&datatypes_path)
             .with_context(|| format!("{datatypes_path:?}"))
@@ -109,7 +109,9 @@ impl CodeGenerator for PythonCodeGenerator {
             .0,
         );
 
-        let components_path = self.pkg_path.join("components");
+        let components_path = self
+            .pkg_path
+            .join(ObjectKind::Component.plural_snake_case());
         let component_overrides = load_overrides(&components_path);
         std::fs::create_dir_all(&components_path)
             .with_context(|| format!("{components_path:?}"))
@@ -126,7 +128,9 @@ impl CodeGenerator for PythonCodeGenerator {
             .0,
         );
 
-        let archetypes_path = self.pkg_path.join("archetypes");
+        let archetypes_path = self
+            .pkg_path
+            .join(ObjectKind::Archetype.plural_snake_case());
         let archetype_overrides = load_overrides(&archetypes_path);
         std::fs::create_dir_all(&archetypes_path)
             .with_context(|| format!("{archetypes_path:?}"))

crates/re_types_builder/src/lib.rs

@@ -131,7 +131,7 @@ mod codegen;
 mod objects;
 
 pub use self::arrow_registry::{ArrowRegistry, LazyDatatype, LazyField};
-pub use self::codegen::{CodeGenerator, PythonCodeGenerator, RustCodeGenerator};
+pub use self::codegen::{CodeGenerator, CppCodeGenerator, PythonCodeGenerator, RustCodeGenerator};
 pub use self::objects::{
     Attributes, Docs, ElementType, Object, ObjectField, ObjectKind, Objects, Type,
 };
@@ -252,6 +252,33 @@ pub fn generate_lang_agnostic(
     (objects, arrow_registry)
 }
 
+/// Generates C++ code.
+///
+/// Panics on error.
+///
+/// - `output_path`: path to the root of the output.
+///
+/// E.g.:
+/// ```no_run
+/// let (object, arrow_registry) = re_types_builder::generate_lang_agnostic(
+///     "./definitions",
+///     "./definitions/rerun/archetypes.fbs",
+/// );
+/// re_types_builder::generate_cpp_code(
+///     ".",
+///     &objects,
+///     &arrow_registry,
+/// );
+/// ```
+pub fn generate_cpp_code(
+    output_path: impl AsRef<Utf8Path>,
+    objects: &Objects,
+    arrow_registry: &ArrowRegistry,
+) {
+    let mut gen = CppCodeGenerator::new(output_path.as_ref());
+    let _filepaths = gen.generate(objects, arrow_registry);
+}
+
 /// Generates Rust code.
 ///
 /// Panics on error.

crates/re_types_builder/src/objects.rs

@@ -207,6 +207,8 @@ pub enum ObjectKind {
 }
 
 impl ObjectKind {
+    pub const ALL: [Self; 3] = [Self::Datatype, Self::Component, Self::Archetype];
+
     // TODO(#2364): use an attr instead of the path
     pub fn from_pkg_name(pkg_name: impl AsRef<str>) -> Self {
         let pkg_name = pkg_name.as_ref().replace(".testing", "");
@@ -220,6 +222,14 @@ impl ObjectKind {
             panic!("unknown package {pkg_name:?}");
         }
     }
+
+    pub fn plural_snake_case(&self) -> &'static str {
+        match self {
+            ObjectKind::Datatype => "datatypes",
+            ObjectKind::Component => "components",
+            ObjectKind::Archetype => "archetypes",
+        }
+    }
 }
 
 /// A high-level representation of a flatbuffers object's documentation.
@@ -596,6 +606,21 @@ impl Object {
             .try_get::<String>(&self.fqname, crate::ATTR_TRANSPARENT)
             .is_some()
     }
+
+    /// Try to find the relative file path of the `.fbs` soruce file.
+    pub fn relative_filepath(&self) -> Option<&Utf8Path> {
+        std::env::var("CARGO_MANIFEST_DIR")
+            .ok()
+            .and_then(|manifest_dir| self.filepath.strip_prefix(manifest_dir).ok())
+    }
+
+    /// The snake-case filename of the object, e.g. `point2d`.
+    pub fn snake_case_name(&self) -> String {
+        Utf8PathBuf::from(&self.virtpath)
+            .file_stem()
+            .unwrap()
+            .to_owned()
+    }
 }
 
 /// Properties specific to either structs or unions, but not both.

rerun_cpp/example/main.cpp

@@ -1,7 +1,3 @@
-#include <iostream>
-
-#define RERUN_WITH_ARROW 1
-
 #include <loguru.hpp>
 #include <rerun.hpp>
 

rerun_cpp/src/archetypes/fuzzy.cpp

@@ -0,0 +1,3 @@
+// NOTE: This file was autogenerated by re_types_builder; DO NOT EDIT.
+// Based on "definitions/rerun/testing/archetypes/fuzzy.fbs"
+#include "fuzzy.hpp"

rerun_cpp/src/archetypes/fuzzy.hpp

@@ -0,0 +1,9 @@
+// NOTE: This file was autogenerated by re_types_builder; DO NOT EDIT.
+// Based on "definitions/rerun/testing/archetypes/fuzzy.fbs"
+#pragma once
+
+namespace rr {
+    namespace archetypes {
+        struct AffixFuzzer1 {};
+    } // namespace archetypes
+} // namespace rr

rerun_cpp/src/archetypes/points2d.cpp

@@ -0,0 +1,3 @@
+// NOTE: This file was autogenerated by re_types_builder; DO NOT EDIT.
+// Based on "definitions/rerun/archetypes/points2d.fbs"
+#include "points2d.hpp"

rerun_cpp/src/archetypes/points2d.hpp

@@ -0,0 +1,9 @@
+// NOTE: This file was autogenerated by re_types_builder; DO NOT EDIT.
+// Based on "definitions/rerun/archetypes/points2d.fbs"
+#pragma once
+
+namespace rr {
+    namespace archetypes {
+        struct Points2D {};
+    } // namespace archetypes
+} // namespace rr

rerun_cpp/src/archetypes/transform3d.cpp

@@ -0,0 +1,3 @@
+// NOTE: This file was autogenerated by re_types_builder; DO NOT EDIT.
+// Based on "definitions/rerun/archetypes/transform3d.fbs"
+#include "transform3d.hpp"

rerun_cpp/src/archetypes/transform3d.hpp

@@ -0,0 +1,9 @@
+// NOTE: This file was autogenerated by re_types_builder; DO NOT EDIT.
+// Based on "definitions/rerun/archetypes/transform3d.fbs"
+#pragma once
+
+namespace rr {
+    namespace archetypes {
+        struct Transform3D {};
+    } // namespace archetypes
+} // namespace rr

rerun_cpp/src/components/class_id.cpp

@@ -0,0 +1,3 @@
+// NOTE: This file was autogenerated by re_types_builder; DO NOT EDIT.
+// Based on "definitions/rerun/components/class_id.fbs"
+#include "class_id.hpp"

rerun_cpp/src/components/class_id.hpp

@@ -0,0 +1,9 @@
+// NOTE: This file was autogenerated by re_types_builder; DO NOT EDIT.
+// Based on "definitions/rerun/components/class_id.fbs"
+#pragma once
+
+namespace rr {
+    namespace components {
+        struct ClassId {};
+    } // namespace components
+} // namespace rr