Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

46 files changed, 2604 insertions, 0 deletions

diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/callback_interface.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/callback_interface.rs
new file mode 100644
index 0000000000..c0c7ab29b9
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/callback_interface.rs
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct CallbackInterfaceCodeType {
+    id: String,
+}
+
+impl CallbackInterfaceCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for CallbackInterfaceCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+
+    fn initialization_fn(&self, oracle: &dyn CodeOracle) -> Option<String> {
+        Some(format!("{}.register", self.ffi_converter_name(oracle)))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/compounds.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/compounds.rs
new file mode 100644
index 0000000000..7d5f77141f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/compounds.rs
@@ -0,0 +1,94 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal, TypeIdentifier};
+use paste::paste;
+
+fn render_literal(oracle: &dyn CodeOracle, literal: &Literal, inner: &TypeIdentifier) -> String {
+    match literal {
+        Literal::Null => "null".into(),
+        Literal::EmptySequence => "listOf()".into(),
+        Literal::EmptyMap => "mapOf()".into(),
+
+        // For optionals
+        _ => oracle.find(inner).literal(oracle, literal),
+    }
+}
+
+macro_rules! impl_code_type_for_compound {
+     ($T:ty, $type_label_pattern:literal, $canonical_name_pattern: literal) => {
+        paste! {
+            pub struct $T {
+                inner: TypeIdentifier,
+            }
+
+            impl $T {
+                pub fn new(inner: TypeIdentifier) -> Self {
+                    Self { inner }
+                }
+                fn inner(&self) -> &TypeIdentifier {
+                    &self.inner
+                }
+            }
+
+            impl CodeType for $T  {
+                fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+                    format!($type_label_pattern, oracle.find(self.inner()).type_label(oracle))
+                }
+
+                fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+                    format!($canonical_name_pattern, oracle.find(self.inner()).canonical_name(oracle))
+                }
+
+                fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+                    render_literal(oracle, literal, self.inner())
+                }
+            }
+        }
+    }
+ }
+
+impl_code_type_for_compound!(OptionalCodeType, "{}?", "Optional{}");
+impl_code_type_for_compound!(SequenceCodeType, "List<{}>", "Sequence{}");
+
+pub struct MapCodeType {
+    key: TypeIdentifier,
+    value: TypeIdentifier,
+}
+
+impl MapCodeType {
+    pub fn new(key: TypeIdentifier, value: TypeIdentifier) -> Self {
+        Self { key, value }
+    }
+
+    fn key(&self) -> &TypeIdentifier {
+        &self.key
+    }
+
+    fn value(&self) -> &TypeIdentifier {
+        &self.value
+    }
+}
+
+impl CodeType for MapCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Map<{}, {}>",
+            self.key().type_label(oracle),
+            self.value().type_label(oracle),
+        )
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Map{}{}",
+            self.key().type_label(oracle),
+            self.value().type_label(oracle),
+        )
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        render_literal(oracle, literal, &self.value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/custom.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/custom.rs
new file mode 100644
index 0000000000..4a5636a228
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/custom.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct CustomCodeType {
+    name: String,
+}
+
+impl CustomCodeType {
+    pub fn new(name: String) -> Self {
+        CustomCodeType { name }
+    }
+}
+
+impl CodeType for CustomCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        self.name.clone()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.name)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!("Can't have a literal of a custom type");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/enum_.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/enum_.rs
new file mode 100644
index 0000000000..941008e370
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/enum_.rs
@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct EnumCodeType {
+    id: String,
+}
+
+impl EnumCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for EnumCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        if let Literal::Enum(v, _) = literal {
+            format!(
+                "{}.{}",
+                self.type_label(oracle),
+                oracle.enum_variant_name(v)
+            )
+        } else {
+            unreachable!();
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/error.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/error.rs
new file mode 100644
index 0000000000..3ab5f0ac9f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/error.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct ErrorCodeType {
+    id: String,
+}
+
+impl ErrorCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for ErrorCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.error_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/external.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/external.rs
new file mode 100644
index 0000000000..32d47cb3f1
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/external.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct ExternalCodeType {
+    name: String,
+}
+
+impl ExternalCodeType {
+    pub fn new(name: String) -> Self {
+        Self { name }
+    }
+}
+
+impl CodeType for ExternalCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        self.name.clone()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.name)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!("Can't have a literal of an external type");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/miscellany.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/miscellany.rs
new file mode 100644
index 0000000000..57b9a145e7
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/miscellany.rs
@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+use paste::paste;
+
+macro_rules! impl_code_type_for_miscellany {
+    ($T:ty, $class_name:literal, $canonical_name:literal) => {
+        paste! {
+            pub struct $T;
+
+            impl CodeType for $T  {
+                fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+                    $class_name.into()
+                }
+
+                fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+                   $canonical_name.into()
+               }
+
+                fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+                    unreachable!()
+                }
+            }
+        }
+    };
+}
+
+impl_code_type_for_miscellany!(TimestampCodeType, "java.time.Instant", "Timestamp");
+
+impl_code_type_for_miscellany!(DurationCodeType, "java.time.Duration", "Duration");
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/mod.rs
new file mode 100644
index 0000000000..b5907898d4
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/mod.rs
@@ -0,0 +1,380 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::borrow::Borrow;
+use std::cell::RefCell;
+use std::collections::{BTreeSet, HashMap, HashSet};
+
+use anyhow::{Context, Result};
+use askama::Template;
+use heck::{ToLowerCamelCase, ToShoutySnakeCase, ToUpperCamelCase};
+use serde::{Deserialize, Serialize};
+
+use crate::backend::{CodeOracle, CodeType, TemplateExpression, TypeIdentifier};
+use crate::interface::*;
+use crate::MergeWith;
+
+mod callback_interface;
+mod compounds;
+mod custom;
+mod enum_;
+mod error;
+mod external;
+mod miscellany;
+mod object;
+mod primitives;
+mod record;
+
+// config options to customize the generated Kotlin.
+#[derive(Debug, Default, Clone, Serialize, Deserialize)]
+pub struct Config {
+    package_name: Option<String>,
+    cdylib_name: Option<String>,
+    #[serde(default)]
+    custom_types: HashMap<String, CustomTypeConfig>,
+    #[serde(default)]
+    external_packages: HashMap<String, String>,
+}
+
+#[derive(Debug, Default, Clone, Serialize, Deserialize)]
+pub struct CustomTypeConfig {
+    imports: Option<Vec<String>>,
+    type_name: Option<String>,
+    into_custom: TemplateExpression,
+    from_custom: TemplateExpression,
+}
+
+impl Config {
+    pub fn package_name(&self) -> String {
+        if let Some(package_name) = &self.package_name {
+            package_name.clone()
+        } else {
+            "uniffi".into()
+        }
+    }
+
+    pub fn cdylib_name(&self) -> String {
+        if let Some(cdylib_name) = &self.cdylib_name {
+            cdylib_name.clone()
+        } else {
+            "uniffi".into()
+        }
+    }
+}
+
+impl From<&ComponentInterface> for Config {
+    fn from(ci: &ComponentInterface) -> Self {
+        Config {
+            package_name: Some(format!("uniffi.{}", ci.namespace())),
+            cdylib_name: Some(format!("uniffi_{}", ci.namespace())),
+            custom_types: HashMap::new(),
+            external_packages: HashMap::new(),
+        }
+    }
+}
+
+impl MergeWith for Config {
+    fn merge_with(&self, other: &Self) -> Self {
+        Config {
+            package_name: self.package_name.merge_with(&other.package_name),
+            cdylib_name: self.cdylib_name.merge_with(&other.cdylib_name),
+            custom_types: self.custom_types.merge_with(&other.custom_types),
+            external_packages: self.external_packages.merge_with(&other.external_packages),
+        }
+    }
+}
+
+// Generate kotlin bindings for the given ComponentInterface, as a string.
+pub fn generate_bindings(config: &Config, ci: &ComponentInterface) -> Result<String> {
+    KotlinWrapper::new(config.clone(), ci)
+        .render()
+        .context("failed to render kotlin bindings")
+}
+
+/// Renders Kotlin helper code for all types
+///
+/// This template is a bit different than others in that it stores internal state from the render
+/// process.  Make sure to only call `render()` once.
+#[derive(Template)]
+#[template(syntax = "kt", escape = "none", path = "Types.kt")]
+pub struct TypeRenderer<'a> {
+    kotlin_config: &'a Config,
+    ci: &'a ComponentInterface,
+    // Track included modules for the `include_once()` macro
+    include_once_names: RefCell<HashSet<String>>,
+    // Track imports added with the `add_import()` macro
+    imports: RefCell<BTreeSet<String>>,
+}
+
+impl<'a> TypeRenderer<'a> {
+    fn new(kotlin_config: &'a Config, ci: &'a ComponentInterface) -> Self {
+        Self {
+            kotlin_config,
+            ci,
+            include_once_names: RefCell::new(HashSet::new()),
+            imports: RefCell::new(BTreeSet::new()),
+        }
+    }
+
+    // Get the package name for an external type
+    fn external_type_package_name(&self, crate_name: &str) -> String {
+        match self.kotlin_config.external_packages.get(crate_name) {
+            Some(name) => name.clone(),
+            None => crate_name.to_string(),
+        }
+    }
+
+    // The following methods are used by the `Types.kt` macros.
+
+    // Helper for the including a template, but only once.
+    //
+    // The first time this is called with a name it will return true, indicating that we should
+    // include the template.  Subsequent calls will return false.
+    fn include_once_check(&self, name: &str) -> bool {
+        self.include_once_names
+            .borrow_mut()
+            .insert(name.to_string())
+    }
+
+    // Helper to add an import statement
+    //
+    // Call this inside your template to cause an import statement to be added at the top of the
+    // file.  Imports will be sorted and de-deuped.
+    //
+    // Returns an empty string so that it can be used inside an askama `{{ }}` block.
+    fn add_import(&self, name: &str) -> &str {
+        self.imports.borrow_mut().insert(name.to_owned());
+        ""
+    }
+}
+
+#[derive(Template)]
+#[template(syntax = "kt", escape = "none", path = "wrapper.kt")]
+pub struct KotlinWrapper<'a> {
+    config: Config,
+    ci: &'a ComponentInterface,
+    type_helper_code: String,
+    type_imports: BTreeSet<String>,
+}
+
+impl<'a> KotlinWrapper<'a> {
+    pub fn new(config: Config, ci: &'a ComponentInterface) -> Self {
+        let type_renderer = TypeRenderer::new(&config, ci);
+        let type_helper_code = type_renderer.render().unwrap();
+        let type_imports = type_renderer.imports.into_inner();
+        Self {
+            config,
+            ci,
+            type_helper_code,
+            type_imports,
+        }
+    }
+
+    pub fn initialization_fns(&self) -> Vec<String> {
+        self.ci
+            .iter_types()
+            .filter_map(|t| t.initialization_fn(&KotlinCodeOracle))
+            .collect()
+    }
+
+    pub fn imports(&self) -> Vec<String> {
+        self.type_imports.iter().cloned().collect()
+    }
+}
+
+#[derive(Clone)]
+pub struct KotlinCodeOracle;
+
+impl KotlinCodeOracle {
+    // Map `Type` instances to a `Box<dyn CodeType>` for that type.
+    //
+    // There is a companion match in `templates/Types.kt` which performs a similar function for the
+    // template code.
+    //
+    //   - When adding additional types here, make sure to also add a match arm to the `Types.kt` template.
+    //   - To keep things managable, let's try to limit ourselves to these 2 mega-matches
+    fn create_code_type(&self, type_: TypeIdentifier) -> Box<dyn CodeType> {
+        match type_ {
+            Type::UInt8 => Box::new(primitives::UInt8CodeType),
+            Type::Int8 => Box::new(primitives::Int8CodeType),
+            Type::UInt16 => Box::new(primitives::UInt16CodeType),
+            Type::Int16 => Box::new(primitives::Int16CodeType),
+            Type::UInt32 => Box::new(primitives::UInt32CodeType),
+            Type::Int32 => Box::new(primitives::Int32CodeType),
+            Type::UInt64 => Box::new(primitives::UInt64CodeType),
+            Type::Int64 => Box::new(primitives::Int64CodeType),
+            Type::Float32 => Box::new(primitives::Float32CodeType),
+            Type::Float64 => Box::new(primitives::Float64CodeType),
+            Type::Boolean => Box::new(primitives::BooleanCodeType),
+            Type::String => Box::new(primitives::StringCodeType),
+
+            Type::Timestamp => Box::new(miscellany::TimestampCodeType),
+            Type::Duration => Box::new(miscellany::DurationCodeType),
+
+            Type::Enum(id) => Box::new(enum_::EnumCodeType::new(id)),
+            Type::Object(id) => Box::new(object::ObjectCodeType::new(id)),
+            Type::Record(id) => Box::new(record::RecordCodeType::new(id)),
+            Type::Error(id) => Box::new(error::ErrorCodeType::new(id)),
+            Type::CallbackInterface(id) => {
+                Box::new(callback_interface::CallbackInterfaceCodeType::new(id))
+            }
+            Type::Optional(inner) => Box::new(compounds::OptionalCodeType::new(*inner)),
+            Type::Sequence(inner) => Box::new(compounds::SequenceCodeType::new(*inner)),
+            Type::Map(key, value) => Box::new(compounds::MapCodeType::new(*key, *value)),
+            Type::External { name, .. } => Box::new(external::ExternalCodeType::new(name)),
+            Type::Custom { name, .. } => Box::new(custom::CustomCodeType::new(name)),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before calling create_code_type")
+            }
+        }
+    }
+}
+
+impl CodeOracle for KotlinCodeOracle {
+    fn find(&self, type_: &TypeIdentifier) -> Box<dyn CodeType> {
+        self.create_code_type(type_.clone())
+    }
+
+    /// Get the idiomatic Kotlin rendering of a class name (for enums, records, errors, etc).
+    fn class_name(&self, nm: &str) -> String {
+        nm.to_string().to_upper_camel_case()
+    }
+
+    /// Get the idiomatic Kotlin rendering of a function name.
+    fn fn_name(&self, nm: &str) -> String {
+        format!("`{}`", nm.to_string().to_lower_camel_case())
+    }
+
+    /// Get the idiomatic Kotlin rendering of a variable name.
+    fn var_name(&self, nm: &str) -> String {
+        format!("`{}`", nm.to_string().to_lower_camel_case())
+    }
+
+    /// Get the idiomatic Kotlin rendering of an individual enum variant.
+    fn enum_variant_name(&self, nm: &str) -> String {
+        nm.to_string().to_shouty_snake_case()
+    }
+
+    /// Get the idiomatic Kotlin rendering of an exception name
+    ///
+    /// This replaces "Error" at the end of the name with "Exception".  Rust code typically uses
+    /// "Error" for any type of error but in the Java world, "Error" means a non-recoverable error
+    /// and is distinguished from an "Exception".
+    fn error_name(&self, nm: &str) -> String {
+        // errors are a class in kotlin.
+        let name = self.class_name(nm);
+        match name.strip_suffix("Error") {
+            None => name,
+            Some(stripped) => format!("{}Exception", stripped),
+        }
+    }
+
+    fn ffi_type_label(&self, ffi_type: &FFIType) -> String {
+        match ffi_type {
+            // Note that unsigned integers in Kotlin are currently experimental, but java.nio.ByteBuffer does not
+            // support them yet. Thus, we use the signed variants to represent both signed and unsigned
+            // types from the component API.
+            FFIType::Int8 | FFIType::UInt8 => "Byte".to_string(),
+            FFIType::Int16 | FFIType::UInt16 => "Short".to_string(),
+            FFIType::Int32 | FFIType::UInt32 => "Int".to_string(),
+            FFIType::Int64 | FFIType::UInt64 => "Long".to_string(),
+            FFIType::Float32 => "Float".to_string(),
+            FFIType::Float64 => "Double".to_string(),
+            FFIType::RustArcPtr(_) => "Pointer".to_string(),
+            FFIType::RustBuffer => "RustBuffer.ByValue".to_string(),
+            FFIType::ForeignBytes => "ForeignBytes.ByValue".to_string(),
+            FFIType::ForeignCallback => "ForeignCallback".to_string(),
+        }
+    }
+}
+
+pub mod filters {
+    use super::*;
+
+    fn oracle() -> &'static KotlinCodeOracle {
+        &KotlinCodeOracle
+    }
+
+    pub fn type_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(codetype.type_label(oracle()))
+    }
+
+    pub fn canonical_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(codetype.canonical_name(oracle()))
+    }
+
+    pub fn ffi_converter_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(codetype.ffi_converter_name(oracle()))
+    }
+
+    pub fn lower_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.lower", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn allocation_size_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!(
+            "{}.allocationSize",
+            codetype.ffi_converter_name(oracle())
+        ))
+    }
+
+    pub fn write_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.write", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn lift_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.lift", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn read_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.read", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn render_literal(
+        literal: &Literal,
+        codetype: &impl CodeType,
+    ) -> Result<String, askama::Error> {
+        Ok(codetype.literal(oracle(), literal))
+    }
+
+    /// Get the Kotlin syntax for representing a given low-level `FFIType`.
+    pub fn ffi_type_name(type_: &FFIType) -> Result<String, askama::Error> {
+        Ok(oracle().ffi_type_label(type_))
+    }
+
+    /// Get the idiomatic Kotlin rendering of a class name (for enums, records, errors, etc).
+    pub fn class_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().class_name(nm))
+    }
+
+    /// Get the idiomatic Kotlin rendering of a function name.
+    pub fn fn_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().fn_name(nm))
+    }
+
+    /// Get the idiomatic Kotlin rendering of a variable name.
+    pub fn var_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().var_name(nm))
+    }
+
+    /// Get the idiomatic Kotlin rendering of an individual enum variant.
+    pub fn enum_variant(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().enum_variant_name(nm))
+    }
+
+    /// Get the idiomatic Kotlin rendering of an exception name, replacing
+    /// `Error` with `Exception`.
+    pub fn exception_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().error_name(nm))
+    }
+
+    /// Remove the "`" chars we put around function/variable names
+    ///
+    /// These are used to avoid name clashes with kotlin identifiers, but sometimes you want to
+    /// render the name unquoted.  One example is the message property for errors where we want to
+    /// display the name for the user.
+    pub fn unquote(nm: &str) -> Result<String, askama::Error> {
+        Ok(nm.trim_matches('`').to_string())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/object.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/object.rs
new file mode 100644
index 0000000000..7a1cddbafd
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/object.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct ObjectCodeType {
+    id: String,
+}
+
+impl ObjectCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for ObjectCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/primitives.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/primitives.rs
new file mode 100644
index 0000000000..b41f7cb49d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/primitives.rs
@@ -0,0 +1,79 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+use crate::interface::{types::Type, Radix};
+use paste::paste;
+
+fn render_literal(_oracle: &dyn CodeOracle, literal: &Literal) -> String {
+    fn typed_number(type_: &Type, num_str: String) -> String {
+        match type_ {
+            // Bytes, Shorts and Ints can all be inferred from the type.
+            Type::Int8 | Type::Int16 | Type::Int32 => num_str,
+            Type::Int64 => format!("{}L", num_str),
+
+            Type::UInt8 | Type::UInt16 | Type::UInt32 => format!("{}u", num_str),
+            Type::UInt64 => format!("{}uL", num_str),
+
+            Type::Float32 => format!("{}f", num_str),
+            Type::Float64 => num_str,
+            _ => panic!("Unexpected literal: {} is not a number", num_str),
+        }
+    }
+
+    match literal {
+        Literal::Boolean(v) => format!("{}", v),
+        Literal::String(s) => format!("\"{}\"", s),
+        Literal::Int(i, radix, type_) => typed_number(
+            type_,
+            match radix {
+                Radix::Octal => format!("{:#x}", i),
+                Radix::Decimal => format!("{}", i),
+                Radix::Hexadecimal => format!("{:#x}", i),
+            },
+        ),
+        Literal::UInt(i, radix, type_) => typed_number(
+            type_,
+            match radix {
+                Radix::Octal => format!("{:#x}", i),
+                Radix::Decimal => format!("{}", i),
+                Radix::Hexadecimal => format!("{:#x}", i),
+            },
+        ),
+        Literal::Float(string, type_) => typed_number(type_, string.clone()),
+
+        _ => unreachable!("Literal"),
+    }
+}
+
+macro_rules! impl_code_type_for_primitive {
+    ($T:ty, $class_name:literal) => {
+        paste! {
+            pub struct $T;
+
+            impl CodeType for $T  {
+                fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+                    $class_name.into()
+                }
+
+                fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+                    render_literal(oracle, &literal)
+                }
+            }
+        }
+    };
+}
+
+impl_code_type_for_primitive!(BooleanCodeType, "Boolean");
+impl_code_type_for_primitive!(StringCodeType, "String");
+impl_code_type_for_primitive!(Int8CodeType, "Byte");
+impl_code_type_for_primitive!(Int16CodeType, "Short");
+impl_code_type_for_primitive!(Int32CodeType, "Int");
+impl_code_type_for_primitive!(Int64CodeType, "Long");
+impl_code_type_for_primitive!(UInt8CodeType, "UByte");
+impl_code_type_for_primitive!(UInt16CodeType, "UShort");
+impl_code_type_for_primitive!(UInt32CodeType, "UInt");
+impl_code_type_for_primitive!(UInt64CodeType, "ULong");
+impl_code_type_for_primitive!(Float32CodeType, "Float");
+impl_code_type_for_primitive!(Float64CodeType, "Double");
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/record.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/record.rs
new file mode 100644
index 0000000000..f923f102c4
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/record.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct RecordCodeType {
+    id: String,
+}
+
+impl RecordCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for RecordCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/mod.rs
new file mode 100644
index 0000000000..c80b4be93a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/mod.rs
@@ -0,0 +1,117 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use anyhow::{bail, Context, Result};
+use camino::{Utf8Path, Utf8PathBuf};
+use fs_err::{self as fs, File};
+use std::{env, ffi::OsString, io::Write, process::Command};
+
+pub mod gen_kotlin;
+pub use gen_kotlin::{generate_bindings, Config};
+
+use super::super::interface::ComponentInterface;
+
+pub fn write_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+    try_format_code: bool,
+) -> Result<()> {
+    let mut kt_file = full_bindings_path(config, out_dir);
+    fs::create_dir_all(&kt_file)?;
+    kt_file.push(format!("{}.kt", ci.namespace()));
+    let mut f = File::create(&kt_file)?;
+    write!(f, "{}", generate_bindings(config, ci)?)?;
+    if try_format_code {
+        if let Err(e) = Command::new("ktlint").arg("-F").arg(&kt_file).output() {
+            println!(
+                "Warning: Unable to auto-format {} using ktlint: {:?}",
+                kt_file.file_name().unwrap(),
+                e
+            )
+        }
+    }
+    Ok(())
+}
+
+fn full_bindings_path(config: &Config, out_dir: &Utf8Path) -> Utf8PathBuf {
+    let package_path: Utf8PathBuf = config.package_name().split('.').collect();
+    Utf8PathBuf::from(out_dir).join(package_path)
+}
+
+/// Generate kotlin bindings for the given namespace, then use the kotlin
+/// command-line tools to compile them into a .jar file.
+pub fn compile_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+) -> Result<()> {
+    let mut kt_file = full_bindings_path(config, out_dir);
+    kt_file.push(format!("{}.kt", ci.namespace()));
+    let jar_file = out_dir.join(format!("{}.jar", ci.namespace()));
+    let status = Command::new("kotlinc")
+        // Our generated bindings should not produce any warnings; fail tests if they do.
+        .arg("-Werror")
+        .arg("-classpath")
+        .arg(classpath_for_testing(out_dir)?)
+        .arg(&kt_file)
+        .arg("-d")
+        .arg(jar_file)
+        .spawn()
+        .context("Failed to spawn `kotlinc` to compile the bindings")?
+        .wait()
+        .context("Failed to wait for `kotlinc` when compiling the bindings")?;
+    if !status.success() {
+        bail!("running `kotlinc` failed")
+    }
+    Ok(())
+}
+
+/// Execute the specifed kotlin script, with classpath based on the generated
+// artifacts in the given output directory.
+pub fn run_script(out_dir: &Utf8Path, script_file: &Utf8Path) -> Result<()> {
+    let mut cmd = Command::new("kotlinc");
+    // Make sure it can load the .jar and its dependencies.
+    cmd.arg("-classpath").arg(classpath_for_testing(out_dir)?);
+    // Enable runtime assertions, for easy testing etc.
+    cmd.arg("-J-ea");
+    // Our test scripts should not produce any warnings.
+    cmd.arg("-Werror");
+    cmd.arg("-script").arg(script_file);
+    let status = cmd
+        .spawn()
+        .context("Failed to spawn `kotlinc` to run Kotlin script")?
+        .wait()
+        .context("Failed to wait for `kotlinc` when running Kotlin script")?;
+    if !status.success() {
+        bail!("running `kotlinc` failed")
+    }
+    Ok(())
+}
+
+// Calculate the classpath string to use for testing
+pub fn classpath_for_testing(out_dir: &Utf8Path) -> Result<OsString> {
+    let mut classpath = env::var_os("CLASSPATH").unwrap_or_default();
+    // This lets java find the compiled library for the rust component.
+    classpath.push(":");
+    classpath.push(out_dir);
+    // This lets java use any generated .jar files from the output directory.
+    //
+    // Including all .jar files is needed for tests like ext-types that use multiple UDL files.
+    // TODO: Instead of including all .jar files, we should only include jar files that we
+    // previously built for this test.
+    for entry in out_dir
+        .read_dir()
+        .context("Failed to list target directory when running Kotlin script")?
+    {
+        let entry = entry.context("Directory listing failed while running Kotlin script")?;
+        if let Some(ext) = entry.path().extension() {
+            if ext == "jar" {
+                classpath.push(":");
+                classpath.push(entry.path());
+            }
+        }
+    }
+    Ok(classpath)
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/BooleanHelper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/BooleanHelper.kt
new file mode 100644
index 0000000000..8cfa2ce000
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/BooleanHelper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterBoolean: FfiConverter<Boolean, Byte> {
+    override fun lift(value: Byte): Boolean {
+        return value.toInt() != 0
+    }
+
+    override fun read(buf: ByteBuffer): Boolean {
+        return lift(buf.get())
+    }
+
+    override fun lower(value: Boolean): Byte {
+        return if (value) 1.toByte() else 0.toByte()
+    }
+
+    override fun allocationSize(value: Boolean) = 1
+
+    override fun write(value: Boolean, buf: ByteBuffer) {
+        buf.put(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceRuntime.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceRuntime.kt
new file mode 100644
index 0000000000..3f5d72a608
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceRuntime.kt
@@ -0,0 +1,74 @@
+internal typealias Handle = Long
+internal class ConcurrentHandleMap<T>(
+    private val leftMap: MutableMap<Handle, T> = mutableMapOf(),
+    private val rightMap: MutableMap<T, Handle> = mutableMapOf()
+) {
+    private val lock = java.util.concurrent.locks.ReentrantLock()
+    private val currentHandle = AtomicLong(0L)
+    private val stride = 1L
+
+    fun insert(obj: T): Handle =
+        lock.withLock {
+            rightMap[obj] ?:
+                currentHandle.getAndAdd(stride)
+                    .also { handle ->
+                        leftMap[handle] = obj
+                        rightMap[obj] = handle
+                    }
+            }
+
+    fun get(handle: Handle) = lock.withLock {
+        leftMap[handle]
+    }
+
+    fun delete(handle: Handle) {
+        this.remove(handle)
+    }
+
+    fun remove(handle: Handle): T? =
+        lock.withLock {
+            leftMap.remove(handle)?.let { obj ->
+                rightMap.remove(obj)
+                obj
+            }
+        }
+}
+
+interface ForeignCallback : com.sun.jna.Callback {
+    public fun invoke(handle: Handle, method: Int, args: RustBuffer.ByValue, outBuf: RustBufferByReference): Int
+}
+
+// Magic number for the Rust proxy to call using the same mechanism as every other method,
+// to free the callback once it's dropped by Rust.
+internal const val IDX_CALLBACK_FREE = 0
+
+public abstract class FfiConverterCallbackInterface<CallbackInterface>(
+    protected val foreignCallback: ForeignCallback
+): FfiConverter<CallbackInterface, Handle> {
+    private val handleMap = ConcurrentHandleMap<CallbackInterface>()
+
+    // Registers the foreign callback with the Rust side.
+    // This method is generated for each callback interface.
+    internal abstract fun register(lib: _UniFFILib)
+
+    fun drop(handle: Handle): RustBuffer.ByValue {
+        return handleMap.remove(handle).let { RustBuffer.ByValue() }
+    }
+
+    override fun lift(value: Handle): CallbackInterface {
+        return handleMap.get(value) ?: throw InternalException("No callback in handlemap; this is a Uniffi bug")
+    }
+
+    override fun read(buf: ByteBuffer) = lift(buf.getLong())
+
+    override fun lower(value: CallbackInterface) =
+        handleMap.insert(value).also {
+            assert(handleMap.get(it) === value) { "Handle map is not returning the object we just placed there. This is a bug in the HandleMap." }
+        }
+
+    override fun allocationSize(value: CallbackInterface) = 8
+
+    override fun write(value: CallbackInterface, buf: ByteBuffer) {
+        buf.putLong(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceTemplate.kt
new file mode 100644
index 0000000000..5e18797345
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceTemplate.kt
@@ -0,0 +1,130 @@
+{%- let cbi = ci.get_callback_interface_definition(name).unwrap() %}
+{%- let type_name = cbi|type_name %}
+{%- let foreign_callback = format!("ForeignCallback{}", canonical_type_name) %}
+
+{% if self.include_once_check("CallbackInterfaceRuntime.kt") %}{% include "CallbackInterfaceRuntime.kt" %}{% endif %}
+{{- self.add_import("java.util.concurrent.atomic.AtomicLong") }}
+{{- self.add_import("java.util.concurrent.locks.ReentrantLock") }}
+{{- self.add_import("kotlin.concurrent.withLock") }}
+
+// Declaration and FfiConverters for {{ type_name }} Callback Interface
+
+public interface {{ type_name }} {
+    {% for meth in cbi.methods() -%}
+    fun {{ meth.name()|fn_name }}({% call kt::arg_list_decl(meth) %})
+    {%- match meth.return_type() -%}
+    {%- when Some with (return_type) %}: {{ return_type|type_name -}}
+    {%- else -%}
+    {%- endmatch %}
+    {% endfor %}
+}
+
+// The ForeignCallback that is passed to Rust.
+internal class {{ foreign_callback }} : ForeignCallback {
+    @Suppress("TooGenericExceptionCaught")
+    override fun invoke(handle: Handle, method: Int, args: RustBuffer.ByValue, outBuf: RustBufferByReference): Int {
+        val cb = {{ ffi_converter_name }}.lift(handle)
+        return when (method) {
+            IDX_CALLBACK_FREE -> {
+                {{ ffi_converter_name }}.drop(handle)
+                // No return value.
+                // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+                0
+            }
+            {% for meth in cbi.methods() -%}
+            {% let method_name = format!("invoke_{}", meth.name())|fn_name -%}
+            {{ loop.index }} -> {
+                // Call the method, write to outBuf and return a status code
+                // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs` for info
+                try {
+                    {%- match meth.throws_type() %}
+                    {%- when Some(error_type) %}
+                    try {
+                        val buffer = this.{{ method_name }}(cb, args)
+                        // Success
+                        outBuf.setValue(buffer)
+                        1
+                    } catch (e: {{ error_type|type_name }}) {
+                        // Expected error
+                        val buffer = {{ error_type|ffi_converter_name }}.lowerIntoRustBuffer(e)
+                        outBuf.setValue(buffer)
+                        -2
+                    }
+                    {%- else %} 
+                    val buffer = this.{{ method_name }}(cb, args)
+                    // Success
+                    outBuf.setValue(buffer)
+                    1
+                    {%- endmatch %}
+                } catch (e: Throwable) {
+                    // Unexpected error
+                    try {
+                        // Try to serialize the error into a string
+                        outBuf.setValue({{ Type::String.borrow()|ffi_converter_name }}.lower(e.toString()))
+                    } catch (e: Throwable) {
+                        // If that fails, then it's time to give up and just return
+                    }
+                    -1
+                }
+            }
+            {% endfor %}
+            else -> {
+                // An unexpected error happened.
+                // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+                try {
+                    // Try to serialize the error into a string
+                    outBuf.setValue({{ Type::String.borrow()|ffi_converter_name }}.lower("Invalid Callaback index"))
+                } catch (e: Throwable) {
+                    // If that fails, then it's time to give up and just return
+                }
+                -1
+            }
+        }
+    }
+
+    {% for meth in cbi.methods() -%}
+    {% let method_name = format!("invoke_{}", meth.name())|fn_name %}
+    private fun {{ method_name }}(kotlinCallbackInterface: {{ type_name }}, args: RustBuffer.ByValue): RustBuffer.ByValue =
+        try {
+        {#- Unpacking args from the RustBuffer #}
+            {%- if meth.arguments().len() != 0 -%}
+            {#- Calling the concrete callback object #}
+            val buf = args.asByteBuffer() ?: throw InternalException("No ByteBuffer in RustBuffer; this is a Uniffi bug")
+            kotlinCallbackInterface.{{ meth.name()|fn_name }}(
+                    {% for arg in meth.arguments() -%}
+                    {{ arg|read_fn }}(buf)
+                    {%- if !loop.last %}, {% endif %}
+                    {% endfor -%}
+                )
+            {% else %}
+            kotlinCallbackInterface.{{ meth.name()|fn_name }}()
+            {% endif -%}
+
+        {#- Packing up the return value into a RustBuffer #}
+                {%- match meth.return_type() -%}
+                {%- when Some with (return_type) -%}
+                .let {
+                    {{ return_type|ffi_converter_name }}.lowerIntoRustBuffer(it)
+                }
+                {%- else -%}
+                .let { RustBuffer.ByValue() }
+                {% endmatch -%}
+                // TODO catch errors and report them back to Rust.
+                // https://github.com/mozilla/uniffi-rs/issues/351
+        } finally {
+            RustBuffer.free(args)
+        }
+
+    {% endfor %}
+}
+
+// The ffiConverter which transforms the Callbacks in to Handles to pass to Rust.
+public object {{ ffi_converter_name }}: FfiConverterCallbackInterface<{{ type_name }}>(
+    foreignCallback = {{ foreign_callback }}()
+) {
+    override fun register(lib: _UniFFILib) {
+        rustCall() { status ->
+            lib.{{ cbi.ffi_init_callback().name() }}(this.foreignCallback, status)
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CustomTypeTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CustomTypeTemplate.kt
new file mode 100644
index 0000000000..c7807f2f33
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CustomTypeTemplate.kt
@@ -0,0 +1,62 @@
+{%- match kotlin_config.custom_types.get(name.as_str())  %}
+{%- when None %}
+{#- Define the type using typealiases to the builtin #}
+/**
+ * Typealias from the type name used in the UDL file to the builtin type.  This
+ * is needed because the UDL type name is used in function/method signatures.
+ * It's also what we have an external type that references a custom type.
+ */
+public typealias {{ name }} = {{ builtin|type_name }}
+public typealias {{ ffi_converter_name }} = {{ builtin|ffi_converter_name }}
+
+{%- when Some with (config) %}
+
+{%- let ffi_type_name=builtin.ffi_type().borrow()|ffi_type_name %}
+
+{# When the config specifies a different type name, create a typealias for it #}
+{%- match config.type_name %}
+{%- when Some(concrete_type_name) %}
+/**
+ * Typealias from the type name used in the UDL file to the custom type.  This
+ * is needed because the UDL type name is used in function/method signatures.
+ * It's also what we have an external type that references a custom type.
+ */
+public typealias {{ name }} = {{ concrete_type_name }}
+{%- else %}
+{%- endmatch %}
+
+{%- match config.imports %}
+{%- when Some(imports) %}
+{%- for import_name in imports %}
+{{ self.add_import(import_name) }}
+{%- endfor %}
+{%- else %}
+{%- endmatch %}
+
+public object {{ ffi_converter_name }}: FfiConverter<{{ name }}, {{ ffi_type_name }}> {
+    override fun lift(value: {{ ffi_type_name }}): {{ name }} {
+        val builtinValue = {{ builtin|lift_fn }}(value)
+        return {{ config.into_custom.render("builtinValue") }}
+    }
+
+    override fun lower(value: {{ name }}): {{ ffi_type_name }} {
+        val builtinValue = {{ config.from_custom.render("value") }}
+        return {{ builtin|lower_fn }}(builtinValue)
+    }
+
+    override fun read(buf: ByteBuffer): {{ name }} {
+        val builtinValue = {{ builtin|read_fn }}(buf)
+        return {{ config.into_custom.render("builtinValue") }}
+    }
+
+    override fun allocationSize(value: {{ name }}): Int {
+        val builtinValue = {{ config.from_custom.render("value") }}
+        return {{ builtin|allocation_size_fn }}(builtinValue)
+    }
+
+    override fun write(value: {{ name }}, buf: ByteBuffer) {
+        val builtinValue = {{ config.from_custom.render("value") }}
+        {{ builtin|write_fn }}(builtinValue, buf)
+    }
+}
+{%- endmatch %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/DurationHelper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/DurationHelper.kt
new file mode 100644
index 0000000000..4237c6f9a8
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/DurationHelper.kt
@@ -0,0 +1,36 @@
+public object FfiConverterDuration: FfiConverterRustBuffer<java.time.Duration> {
+    override fun read(buf: ByteBuffer): java.time.Duration {
+        // Type mismatch (should be u64) but we check for overflow/underflow below
+        val seconds = buf.getLong()
+        // Type mismatch (should be u32) but we check for overflow/underflow below
+        val nanoseconds = buf.getInt().toLong()
+        if (seconds < 0) {
+            throw java.time.DateTimeException("Duration exceeds minimum or maximum value supported by uniffi")
+        }
+        if (nanoseconds < 0) {
+            throw java.time.DateTimeException("Duration nanoseconds exceed minimum or maximum supported by uniffi")
+        }
+        return java.time.Duration.ofSeconds(seconds, nanoseconds)
+    }
+
+    // 8 bytes for seconds, 4 bytes for nanoseconds
+    override fun allocationSize(value: java.time.Duration) = 12
+
+    override fun write(value: java.time.Duration, buf: ByteBuffer) {
+        if (value.seconds < 0) {
+            // Rust does not support negative Durations
+            throw IllegalArgumentException("Invalid duration, must be non-negative")
+        }
+
+        if (value.nano < 0) {
+            // Java docs provide guarantee that nano will always be positive, so this should be impossible
+            // See: https://docs.oracle.com/javase/8/docs/api/java/time/Duration.html
+            throw IllegalArgumentException("Invalid duration, nano value must be non-negative")
+        }
+
+        // Type mismatch (should be u64) but since Rust doesn't support negative durations we should be OK
+        buf.putLong(value.seconds)
+        // Type mismatch (should be u32) but since values will always be between 0 and 999,999,999 it should be OK
+        buf.putInt(value.nano)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/EnumTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/EnumTemplate.kt
new file mode 100644
index 0000000000..2422046e37
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/EnumTemplate.kt
@@ -0,0 +1,107 @@
+{#
+// Kotlin's `enum class` constuct doesn't support variants with associated data,
+// but is a little nicer for consumers than its `sealed class` enum pattern.
+// So, we switch here, using `enum class` for enums with no associated data
+// and `sealed class` for the general case.
+#}
+{%- let e = ci.get_enum_definition(name).unwrap() %}
+
+{%- if e.is_flat() %}
+
+enum class {{ type_name }} {
+    {% for variant in e.variants() -%}
+    {{ variant.name()|enum_variant }}{% if loop.last %};{% else %},{% endif %}
+    {%- endfor %}
+}
+
+public object {{ e|ffi_converter_name }}: FfiConverterRustBuffer<{{ type_name }}> {
+    override fun read(buf: ByteBuffer) = try {
+        {{ type_name }}.values()[buf.getInt() - 1]
+    } catch (e: IndexOutOfBoundsException) {
+        throw RuntimeException("invalid enum value, something is very wrong!!", e)
+    }
+
+    override fun allocationSize(value: {{ type_name }}) = 4
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        buf.putInt(value.ordinal + 1)
+    }
+}
+
+{% else %}
+
+sealed class {{ type_name }}{% if contains_object_references %}: Disposable {% endif %} {
+    {% for variant in e.variants() -%}
+    {% if !variant.has_fields() -%}
+    object {{ variant.name()|class_name }} : {{ type_name }}()
+    {% else -%}
+    data class {{ variant.name()|class_name }}(
+        {% for field in variant.fields() -%}
+        val {{ field.name()|var_name }}: {{ field|type_name}}{% if loop.last %}{% else %}, {% endif %}
+        {% endfor -%}
+    ) : {{ type_name }}()
+    {%- endif %}
+    {% endfor %}
+
+    {% if contains_object_references %}
+    @Suppress("UNNECESSARY_SAFE_CALL") // codegen is much simpler if we unconditionally emit safe calls here
+    override fun destroy() {
+        when(this) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|class_name }} -> {
+                {%- if variant.has_fields() %}
+                {% call kt::destroy_fields(variant) %}
+                {% else -%}
+                // Nothing to destroy
+                {%- endif %}
+            }
+            {%- endfor %}
+        }.let { /* this makes the `when` an expression, which ensures it is exhaustive */ }
+    }
+    {% endif %}
+}
+
+public object {{ e|ffi_converter_name }} : FfiConverterRustBuffer<{{ type_name }}>{
+    override fun read(buf: ByteBuffer): {{ type_name }} {
+        return when(buf.getInt()) {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} -> {{ type_name }}.{{ variant.name()|class_name }}{% if variant.has_fields() %}(
+                {% for field in variant.fields() -%}
+                {{ field|read_fn }}(buf),
+                {% endfor -%}
+            ){%- endif -%}
+            {%- endfor %}
+            else -> throw RuntimeException("invalid enum value, something is very wrong!!")
+        }
+    }
+
+    override fun allocationSize(value: {{ type_name }}) = when(value) {
+        {%- for variant in e.variants() %}
+        is {{ type_name }}.{{ variant.name()|class_name }} -> {
+            // Add the size for the Int that specifies the variant plus the size needed for all fields
+            (
+                4
+                {%- for field in variant.fields() %}
+                + {{ field|allocation_size_fn }}(value.{{ field.name()|var_name }})
+                {%- endfor %}
+            )
+        }
+        {%- endfor %}
+    }
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        when(value) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|class_name }} -> {
+                buf.putInt({{ loop.index }})
+                {%- for field in variant.fields() %}
+                {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+                {%- endfor %}
+                Unit
+            }
+            {%- endfor %}
+        }.let { /* this makes the `when` an expression, which ensures it is exhaustive */ }
+    }
+}
+
+{% endif %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ErrorTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ErrorTemplate.kt
new file mode 100644
index 0000000000..9ddef9bb73
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ErrorTemplate.kt
@@ -0,0 +1,109 @@
+{%- let e = ci.get_error_definition(name).unwrap() %}
+
+{% if e.is_flat() %}
+sealed class {{ type_name }}(message: String): Exception(message){% if contains_object_references %}, Disposable {% endif %} {
+        // Each variant is a nested class
+        // Flat enums carries a string error message, so no special implementation is necessary.
+        {% for variant in e.variants() -%}
+        class {{ variant.name()|exception_name }}(message: String) : {{ type_name }}(message)
+        {% endfor %}
+
+    companion object ErrorHandler : CallStatusErrorHandler<{{ type_name }}> {
+        override fun lift(error_buf: RustBuffer.ByValue): {{ type_name }} = {{ e|lift_fn }}(error_buf)
+    }
+}
+{%- else %}
+sealed class {{ type_name }}: Exception(){% if contains_object_references %}, Disposable {% endif %} {
+    // Each variant is a nested class
+    {% for variant in e.variants() -%}
+    {%- let variant_name = variant.name()|exception_name %}
+    class {{ variant_name }}(
+        {% for field in variant.fields() -%}
+        val {{ field.name()|var_name }}: {{ field|type_name}}{% if loop.last %}{% else %}, {% endif %}
+        {% endfor -%}
+    ) : {{ type_name }}() {
+        override val message
+            get() = "{%- for field in variant.fields() %}{{ field.name()|var_name|unquote }}=${ {{field.name()|var_name }} }{% if !loop.last %}, {% endif %}{% endfor %}"
+    }
+    {% endfor %}
+
+    companion object ErrorHandler : CallStatusErrorHandler<{{ type_name }}> {
+        override fun lift(error_buf: RustBuffer.ByValue): {{ type_name }} = {{ e|lift_fn }}(error_buf)
+    }
+
+    {% if contains_object_references %}
+    @Suppress("UNNECESSARY_SAFE_CALL") // codegen is much simpler if we unconditionally emit safe calls here
+    override fun destroy() {
+        when(this) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|exception_name }} -> {
+                {%- if variant.has_fields() %}
+                {% call kt::destroy_fields(variant) %}
+                {% else -%}
+                // Nothing to destroy
+                {%- endif %}
+            }
+            {%- endfor %}
+        }.let { /* this makes the `when` an expression, which ensures it is exhaustive */ }
+    }
+    {% endif %}
+}
+{%- endif %}
+
+public object {{ e|ffi_converter_name }} : FfiConverterRustBuffer<{{ type_name }}> {
+    override fun read(buf: ByteBuffer): {{ type_name }} {
+        {% if e.is_flat() %}
+            return when(buf.getInt()) {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} -> {{ type_name }}.{{ variant.name()|exception_name }}({{ TypeIdentifier::String.borrow()|read_fn }}(buf))
+            {%- endfor %}
+            else -> throw RuntimeException("invalid error enum value, something is very wrong!!")
+        }
+        {% else %}
+
+        return when(buf.getInt()) {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} -> {{ type_name }}.{{ variant.name()|exception_name }}({% if variant.has_fields() %}
+                {% for field in variant.fields() -%}
+                {{ field|read_fn }}(buf),
+                {% endfor -%}
+            {%- endif -%})
+            {%- endfor %}
+            else -> throw RuntimeException("invalid error enum value, something is very wrong!!")
+        }
+        {%- endif %}
+    }
+
+    override fun allocationSize(value: {{ type_name }}): Int {
+        {%- if e.is_flat() %}
+        return 4
+        {%- else %}
+        return when(value) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|exception_name }} -> (
+                // Add the size for the Int that specifies the variant plus the size needed for all fields
+                4
+                {%- for field in variant.fields() %}
+                + {{ field|allocation_size_fn }}(value.{{ field.name()|var_name }})
+                {%- endfor %}
+            )
+            {%- endfor %}
+        }
+        {%- endif %}
+    }
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        when(value) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|exception_name }} -> {
+                buf.putInt({{ loop.index }})
+                {%- for field in variant.fields() %}
+                {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+                {%- endfor %}
+                Unit
+            }
+            {%- endfor %}
+        }.let { /* this makes the `when` an expression, which ensures it is exhaustive */ }
+    }
+
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ExternalTypeTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ExternalTypeTemplate.kt
new file mode 100644
index 0000000000..6d10c37e31
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ExternalTypeTemplate.kt
@@ -0,0 +1,6 @@
+{%- let package_name=self.external_type_package_name(crate_name) %}
+{%- let fully_qualified_type_name = "{}.{}"|format(package_name, name) %}
+{%- let fully_qualified_ffi_converter_name = "{}.FfiConverterType{}"|format(package_name, name) %}
+
+{{- self.add_import(fully_qualified_type_name) }}
+{{ self.add_import(fully_qualified_ffi_converter_name) }}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/FfiConverterTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/FfiConverterTemplate.kt
new file mode 100644
index 0000000000..3b2c9d225a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/FfiConverterTemplate.kt
@@ -0,0 +1,71 @@
+// The FfiConverter interface handles converter types to and from the FFI
+//
+// All implementing objects should be public to support external types.  When a
+// type is external we need to import it's FfiConverter.
+public interface FfiConverter<KotlinType, FfiType> {
+    // Convert an FFI type to a Kotlin type
+    fun lift(value: FfiType): KotlinType
+
+    // Convert an Kotlin type to an FFI type
+    fun lower(value: KotlinType): FfiType
+
+    // Read a Kotlin type from a `ByteBuffer`
+    fun read(buf: ByteBuffer): KotlinType
+
+    // Calculate bytes to allocate when creating a `RustBuffer`
+    //
+    // This must return at least as many bytes as the write() function will
+    // write. It can return more bytes than needed, for example when writing
+    // Strings we can't know the exact bytes needed until we the UTF-8
+    // encoding, so we pessimistically allocate the largest size possible (3
+    // bytes per codepoint).  Allocating extra bytes is not really a big deal
+    // because the `RustBuffer` is short-lived.
+    fun allocationSize(value: KotlinType): Int
+
+    // Write a Kotlin type to a `ByteBuffer`
+    fun write(value: KotlinType, buf: ByteBuffer)
+
+    // Lower a value into a `RustBuffer`
+    //
+    // This method lowers a value into a `RustBuffer` rather than the normal
+    // FfiType.  It's used by the callback interface code.  Callback interface
+    // returns are always serialized into a `RustBuffer` regardless of their
+    // normal FFI type.
+    fun lowerIntoRustBuffer(value: KotlinType): RustBuffer.ByValue {
+        val rbuf = RustBuffer.alloc(allocationSize(value))
+        try {
+            val bbuf = rbuf.data!!.getByteBuffer(0, rbuf.capacity.toLong()).also {
+                it.order(ByteOrder.BIG_ENDIAN)
+            }
+            write(value, bbuf)
+            rbuf.writeField("len", bbuf.position())
+            return rbuf
+        } catch (e: Throwable) {
+            RustBuffer.free(rbuf)
+            throw e
+        }
+    }
+
+    // Lift a value from a `RustBuffer`.
+    //
+    // This here mostly because of the symmetry with `lowerIntoRustBuffer()`.
+    // It's currently only used by the `FfiConverterRustBuffer` class below.
+    fun liftFromRustBuffer(rbuf: RustBuffer.ByValue): KotlinType {
+        val byteBuf = rbuf.asByteBuffer()!!
+        try {
+           val item = read(byteBuf)
+           if (byteBuf.hasRemaining()) {
+               throw RuntimeException("junk remaining in buffer after lifting, something is very wrong!!")
+           }
+           return item
+        } finally {
+            RustBuffer.free(rbuf)
+        }
+    }
+}
+
+// FfiConverter that uses `RustBuffer` as the FfiType
+public interface FfiConverterRustBuffer<KotlinType>: FfiConverter<KotlinType, RustBuffer.ByValue> {
+    override fun lift(value: RustBuffer.ByValue) = liftFromRustBuffer(value)
+    override fun lower(value: KotlinType) = lowerIntoRustBuffer(value)
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float32Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float32Helper.kt
new file mode 100644
index 0000000000..eafec5d122
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float32Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterFloat: FfiConverter<Float, Float> {
+    override fun lift(value: Float): Float {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Float {
+        return buf.getFloat()
+    }
+
+    override fun lower(value: Float): Float {
+        return value
+    }
+
+    override fun allocationSize(value: Float) = 4
+
+    override fun write(value: Float, buf: ByteBuffer) {
+        buf.putFloat(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float64Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float64Helper.kt
new file mode 100644
index 0000000000..9fc2892c95
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float64Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterDouble: FfiConverter<Double, Double> {
+    override fun lift(value: Double): Double {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Double {
+        return buf.getDouble()
+    }
+
+    override fun lower(value: Double): Double {
+        return value
+    }
+
+    override fun allocationSize(value: Double) = 8
+
+    override fun write(value: Double, buf: ByteBuffer) {
+        buf.putDouble(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Helpers.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Helpers.kt
new file mode 100644
index 0000000000..d7e61ef4c7
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Helpers.kt
@@ -0,0 +1,66 @@
+// A handful of classes and functions to support the generated data structures.
+// This would be a good candidate for isolating in its own ffi-support lib.
+// Error runtime.
+@Structure.FieldOrder("code", "error_buf")
+internal open class RustCallStatus : Structure() {
+    @JvmField var code: Int = 0
+    @JvmField var error_buf: RustBuffer.ByValue = RustBuffer.ByValue()
+
+    fun isSuccess(): Boolean {
+        return code == 0
+    }
+
+    fun isError(): Boolean {
+        return code == 1
+    }
+
+    fun isPanic(): Boolean {
+        return code == 2
+    }
+}
+
+class InternalException(message: String) : Exception(message)
+
+// Each top-level error class has a companion object that can lift the error from the call status's rust buffer
+interface CallStatusErrorHandler<E> {
+    fun lift(error_buf: RustBuffer.ByValue): E;
+}
+
+// Helpers for calling Rust
+// In practice we usually need to be synchronized to call this safely, so it doesn't
+// synchronize itself
+
+// Call a rust function that returns a Result<>.  Pass in the Error class companion that corresponds to the Err
+private inline fun <U, E: Exception> rustCallWithError(errorHandler: CallStatusErrorHandler<E>, callback: (RustCallStatus) -> U): U {
+    var status = RustCallStatus();
+    val return_value = callback(status)
+    if (status.isSuccess()) {
+        return return_value
+    } else if (status.isError()) {
+        throw errorHandler.lift(status.error_buf)
+    } else if (status.isPanic()) {
+        // when the rust code sees a panic, it tries to construct a rustbuffer
+        // with the message.  but if that code panics, then it just sends back
+        // an empty buffer.
+        if (status.error_buf.len > 0) {
+            throw InternalException({{ TypeIdentifier::String.borrow()|lift_fn }}(status.error_buf))
+        } else {
+            throw InternalException("Rust panic")
+        }
+    } else {
+        throw InternalException("Unknown rust call status: $status.code")
+    }
+}
+
+// CallStatusErrorHandler implementation for times when we don't expect a CALL_ERROR
+object NullCallStatusErrorHandler: CallStatusErrorHandler<InternalException> {
+    override fun lift(error_buf: RustBuffer.ByValue): InternalException {
+        RustBuffer.free(error_buf)
+        return InternalException("Unexpected CALL_ERROR")
+    }
+}
+
+// Call a rust function that returns a plain value
+private inline fun <U> rustCall(callback: (RustCallStatus) -> U): U {
+    return rustCallWithError(NullCallStatusErrorHandler, callback);
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int16Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int16Helper.kt
new file mode 100644
index 0000000000..75564276be
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int16Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterShort: FfiConverter<Short, Short> {
+    override fun lift(value: Short): Short {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Short {
+        return buf.getShort()
+    }
+
+    override fun lower(value: Short): Short {
+        return value
+    }
+
+    override fun allocationSize(value: Short) = 2
+
+    override fun write(value: Short, buf: ByteBuffer) {
+        buf.putShort(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int32Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int32Helper.kt
new file mode 100644
index 0000000000..b7a8131c8b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int32Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterInt: FfiConverter<Int, Int> {
+    override fun lift(value: Int): Int {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Int {
+        return buf.getInt()
+    }
+
+    override fun lower(value: Int): Int {
+        return value
+    }
+
+    override fun allocationSize(value: Int) = 4
+
+    override fun write(value: Int, buf: ByteBuffer) {
+        buf.putInt(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int64Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int64Helper.kt
new file mode 100644
index 0000000000..601cfc7c2c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int64Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterLong: FfiConverter<Long, Long> {
+    override fun lift(value: Long): Long {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Long {
+        return buf.getLong()
+    }
+
+    override fun lower(value: Long): Long {
+        return value
+    }
+
+    override fun allocationSize(value: Long) = 8
+
+    override fun write(value: Long, buf: ByteBuffer) {
+        buf.putLong(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int8Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int8Helper.kt
new file mode 100644
index 0000000000..9237768dbf
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int8Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterByte: FfiConverter<Byte, Byte> {
+    override fun lift(value: Byte): Byte {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Byte {
+        return buf.get()
+    }
+
+    override fun lower(value: Byte): Byte {
+        return value
+    }
+
+    override fun allocationSize(value: Byte) = 1
+
+    override fun write(value: Byte, buf: ByteBuffer) {
+        buf.put(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/MapTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/MapTemplate.kt
new file mode 100644
index 0000000000..c8cbecb68b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/MapTemplate.kt
@@ -0,0 +1,35 @@
+{%- let key_type_name = key_type|type_name %}
+{%- let value_type_name = value_type|type_name %}
+public object {{ ffi_converter_name }}: FfiConverterRustBuffer<Map<{{ key_type_name }}, {{ value_type_name }}>> {
+    override fun read(buf: ByteBuffer): Map<{{ key_type_name }}, {{ value_type_name }}> {
+        // TODO: Once Kotlin's `buildMap` API is stabilized we should use it here.
+        val items : MutableMap<{{ key_type_name }}, {{ value_type_name }}> = mutableMapOf()
+        val len = buf.getInt()
+        repeat(len) {
+            val k = {{ key_type|read_fn }}(buf)
+            val v = {{ value_type|read_fn }}(buf)
+            items[k] = v
+        }
+        return items
+    }
+
+    override fun allocationSize(value: Map<{{ key_type_name }}, {{ value_type_name }}>): Int {
+        val spaceForMapSize = 4
+        val spaceForChildren = value.map { (k, v) ->
+            {{ key_type|allocation_size_fn }}(k) +
+            {{ value_type|allocation_size_fn }}(v)
+        }.sum()
+        return spaceForMapSize + spaceForChildren
+    }
+
+    override fun write(value: Map<{{ key_type_name }}, {{ value_type_name }}>, buf: ByteBuffer) {
+        buf.putInt(value.size)
+        // The parens on `(k, v)` here ensure we're calling the right method,
+        // which is important for compatibility with older android devices.
+        // Ref https://blog.danlew.net/2017/03/16/kotlin-puzzler-whose-line-is-it-anyways/
+        value.forEach { (k, v) ->
+            {{ key_type|write_fn }}(k, buf)
+            {{ value_type|write_fn }}(v, buf)
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/NamespaceLibraryTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/NamespaceLibraryTemplate.kt
new file mode 100644
index 0000000000..df96ee5cbb
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/NamespaceLibraryTemplate.kt
@@ -0,0 +1,40 @@
+@Synchronized
+private fun findLibraryName(componentName: String): String {
+    val libOverride = System.getProperty("uniffi.component.$componentName.libraryOverride")
+    if (libOverride != null) {
+        return libOverride
+    }
+    return "{{ config.cdylib_name() }}"
+}
+
+private inline fun <reified Lib : Library> loadIndirect(
+    componentName: String
+): Lib {
+    return Native.load<Lib>(findLibraryName(componentName), Lib::class.java)
+}
+
+// A JNA Library to expose the extern-C FFI definitions.
+// This is an implementation detail which will be called internally by the public API.
+
+internal interface _UniFFILib : Library {
+    companion object {
+        internal val INSTANCE: _UniFFILib by lazy {
+            loadIndirect<_UniFFILib>(componentName = "{{ ci.namespace() }}")
+            {% let initialization_fns = self.initialization_fns() %}
+            {%- if !initialization_fns.is_empty() -%}
+            .also { lib: _UniFFILib ->
+                {% for fn in initialization_fns -%}
+                {{ fn }}(lib)
+                {% endfor -%}
+            }
+            {% endif %}
+        }
+    }
+
+    {% for func in ci.iter_ffi_function_definitions() -%}
+    fun {{ func.name() }}(
+        {%- call kt::arg_list_ffi_decl(func) %}
+    ){%- match func.return_type() -%}{%- when Some with (type_) %}: {{ type_.borrow()|ffi_type_name }}{% when None %}: Unit{% endmatch %}
+
+    {% endfor %}
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectRuntime.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectRuntime.kt
new file mode 100644
index 0000000000..5265c09441
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectRuntime.kt
@@ -0,0 +1,161 @@
+// Interface implemented by anything that can contain an object reference.
+//
+// Such types expose a `destroy()` method that must be called to cleanly
+// dispose of the contained objects. Failure to call this method may result
+// in memory leaks.
+//
+// The easiest way to ensure this method is called is to use the `.use`
+// helper method to execute a block and destroy the object at the end.
+interface Disposable {
+    fun destroy()
+    companion object {
+        fun destroy(vararg args: Any?) {
+            args.filterIsInstance<Disposable>()
+                .forEach(Disposable::destroy)
+        }
+    }
+}
+
+inline fun <T : Disposable?, R> T.use(block: (T) -> R) =
+    try {
+        block(this)
+    } finally {
+        try {
+            // N.B. our implementation is on the nullable type `Disposable?`.
+            this?.destroy()
+        } catch (e: Throwable) {
+            // swallow
+        }
+    }
+
+// The base class for all UniFFI Object types.
+//
+// This class provides core operations for working with the Rust `Arc<T>` pointer to
+// the live Rust struct on the other side of the FFI.
+//
+// There's some subtlety here, because we have to be careful not to operate on a Rust
+// struct after it has been dropped, and because we must expose a public API for freeing
+// the Kotlin wrapper object in lieu of reliable finalizers. The core requirements are:
+//
+//   * Each `FFIObject` instance holds an opaque pointer to the underlying Rust struct.
+//     Method calls need to read this pointer from the object's state and pass it in to
+//     the Rust FFI.
+//
+//   * When an `FFIObject` is no longer needed, its pointer should be passed to a
+//     special destructor function provided by the Rust FFI, which will drop the
+//     underlying Rust struct.
+//
+//   * Given an `FFIObject` instance, calling code is expected to call the special
+//     `destroy` method in order to free it after use, either by calling it explicitly
+//     or by using a higher-level helper like the `use` method. Failing to do so will
+//     leak the underlying Rust struct.
+//
+//   * We can't assume that calling code will do the right thing, and must be prepared
+//     to handle Kotlin method calls executing concurrently with or even after a call to
+//     `destroy`, and to handle multiple (possibly concurrent!) calls to `destroy`.
+//
+//   * We must never allow Rust code to operate on the underlying Rust struct after
+//     the destructor has been called, and must never call the destructor more than once.
+//     Doing so may trigger memory unsafety.
+//
+// If we try to implement this with mutual exclusion on access to the pointer, there is the
+// possibility of a race between a method call and a concurrent call to `destroy`:
+//
+//    * Thread A starts a method call, reads the value of the pointer, but is interrupted
+//      before it can pass the pointer over the FFI to Rust.
+//    * Thread B calls `destroy` and frees the underlying Rust struct.
+//    * Thread A resumes, passing the already-read pointer value to Rust and triggering
+//      a use-after-free.
+//
+// One possible solution would be to use a `ReadWriteLock`, with each method call taking
+// a read lock (and thus allowed to run concurrently) and the special `destroy` method
+// taking a write lock (and thus blocking on live method calls). However, we aim not to
+// generate methods with any hidden blocking semantics, and a `destroy` method that might
+// block if called incorrectly seems to meet that bar.
+//
+// So, we achieve our goals by giving each `FFIObject` an associated `AtomicLong` counter to track
+// the number of in-flight method calls, and an `AtomicBoolean` flag to indicate whether `destroy`
+// has been called. These are updated according to the following rules:
+//
+//    * The initial value of the counter is 1, indicating a live object with no in-flight calls.
+//      The initial value for the flag is false.
+//
+//    * At the start of each method call, we atomically check the counter.
+//      If it is 0 then the underlying Rust struct has already been destroyed and the call is aborted.
+//      If it is nonzero them we atomically increment it by 1 and proceed with the method call.
+//
+//    * At the end of each method call, we atomically decrement and check the counter.
+//      If it has reached zero then we destroy the underlying Rust struct.
+//
+//    * When `destroy` is called, we atomically flip the flag from false to true.
+//      If the flag was already true we silently fail.
+//      Otherwise we atomically decrement and check the counter.
+//      If it has reached zero then we destroy the underlying Rust struct.
+//
+// Astute readers may observe that this all sounds very similar to the way that Rust's `Arc<T>` works,
+// and indeed it is, with the addition of a flag to guard against multiple calls to `destroy`.
+//
+// The overall effect is that the underlying Rust struct is destroyed only when `destroy` has been
+// called *and* all in-flight method calls have completed, avoiding violating any of the expectations
+// of the underlying Rust code.
+//
+// In the future we may be able to replace some of this with automatic finalization logic, such as using
+// the new "Cleaner" functionaility in Java 9. The above scheme has been designed to work even if `destroy` is
+// invoked by garbage-collection machinery rather than by calling code (which by the way, it's apparently also
+// possible for the JVM to finalize an object while there is an in-flight call to one of its methods [1],
+// so there would still be some complexity here).
+//
+// Sigh...all of this for want of a robust finalization mechanism.
+//
+// [1] https://stackoverflow.com/questions/24376768/can-java-finalize-an-object-when-it-is-still-in-scope/24380219
+//
+abstract class FFIObject(
+    protected val pointer: Pointer
+): Disposable, AutoCloseable {
+
+    private val wasDestroyed = AtomicBoolean(false)
+    private val callCounter = AtomicLong(1)
+
+    open protected fun freeRustArcPtr() {
+        // To be overridden in subclasses.
+    }
+
+    override fun destroy() {
+        // Only allow a single call to this method.
+        // TODO: maybe we should log a warning if called more than once?
+        if (this.wasDestroyed.compareAndSet(false, true)) {
+            // This decrement always matches the initial count of 1 given at creation time.
+            if (this.callCounter.decrementAndGet() == 0L) {
+                this.freeRustArcPtr()
+            }
+        }
+    }
+
+    @Synchronized
+    override fun close() {
+        this.destroy()
+    }
+
+    internal inline fun <R> callWithPointer(block: (ptr: Pointer) -> R): R {
+        // Check and increment the call counter, to keep the object alive.
+        // This needs a compare-and-set retry loop in case of concurrent updates.
+        do {
+            val c = this.callCounter.get()
+            if (c == 0L) {
+                throw IllegalStateException("${this.javaClass.simpleName} object has already been destroyed")
+            }
+            if (c == Long.MAX_VALUE) {
+                throw IllegalStateException("${this.javaClass.simpleName} call counter would overflow")
+            }
+        } while (! this.callCounter.compareAndSet(c, c + 1L))
+        // Now we can safely do the method call without the pointer being freed concurrently.
+        try {
+            return block(this.pointer)
+        } finally {
+            // This decrement aways matches the increment we performed above.
+            if (this.callCounter.decrementAndGet() == 0L) {
+                this.freeRustArcPtr()
+            }
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectTemplate.kt
new file mode 100644
index 0000000000..5d654d9fae
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectTemplate.kt
@@ -0,0 +1,100 @@
+{%- let obj = ci.get_object_definition(name).unwrap() %}
+{%- if self.include_once_check("ObjectRuntime.kt") %}{% include "ObjectRuntime.kt" %}{% endif %}
+{{- self.add_import("java.util.concurrent.atomic.AtomicLong") }}
+{{- self.add_import("java.util.concurrent.atomic.AtomicBoolean") }}
+
+public interface {{ type_name }}Interface {
+    {% for meth in obj.methods() -%}
+    {%- match meth.throws_type() -%}
+    {%- when Some with (throwable) %}
+    @Throws({{ throwable|type_name }}::class)
+    {%- else -%}
+    {%- endmatch %}
+    fun {{ meth.name()|fn_name }}({% call kt::arg_list_decl(meth) %})
+    {%- match meth.return_type() -%}
+    {%- when Some with (return_type) %}: {{ return_type|type_name -}}
+    {%- else -%}
+    {%- endmatch %}
+    {% endfor %}
+}
+
+class {{ type_name }}(
+    pointer: Pointer
+) : FFIObject(pointer), {{ type_name }}Interface {
+
+    {%- match obj.primary_constructor() %}
+    {%- when Some with (cons) %}
+    constructor({% call kt::arg_list_decl(cons) -%}) :
+        this({% call kt::to_ffi_call(cons) %})
+    {%- when None %}
+    {%- endmatch %}
+
+    /**
+     * Disconnect the object from the underlying Rust object.
+     *
+     * It can be called more than once, but once called, interacting with the object
+     * causes an `IllegalStateException`.
+     *
+     * Clients **must** call this method once done with the object, or cause a memory leak.
+     */
+    override protected fun freeRustArcPtr() {
+        rustCall() { status ->
+            _UniFFILib.INSTANCE.{{ obj.ffi_object_free().name() }}(this.pointer, status)
+        }
+    }
+
+    {% for meth in obj.methods() -%}
+    {%- match meth.throws_type() -%}
+    {%- when Some with (throwable) %}
+    @Throws({{ throwable|type_name }}::class)
+    {%- else -%}
+    {%- endmatch %}
+    {%- match meth.return_type() -%}
+
+    {%- when Some with (return_type) -%}
+    override fun {{ meth.name()|fn_name }}({% call kt::arg_list_protocol(meth) %}): {{ return_type|type_name }} =
+        callWithPointer {
+            {%- call kt::to_ffi_call_with_prefix("it", meth) %}
+        }.let {
+            {{ return_type|lift_fn }}(it)
+        }
+
+    {%- when None -%}
+    override fun {{ meth.name()|fn_name }}({% call kt::arg_list_protocol(meth) %}) =
+        callWithPointer {
+            {%- call kt::to_ffi_call_with_prefix("it", meth) %}
+        }
+    {% endmatch %}
+    {% endfor %}
+
+    {% if !obj.alternate_constructors().is_empty() -%}
+    companion object {
+        {% for cons in obj.alternate_constructors() -%}
+        fun {{ cons.name()|fn_name }}({% call kt::arg_list_decl(cons) %}): {{ type_name }} =
+            {{ type_name }}({% call kt::to_ffi_call(cons) %})
+        {% endfor %}
+    }
+    {% endif %}
+}
+
+public object {{ obj|ffi_converter_name }}: FfiConverter<{{ type_name }}, Pointer> {
+    override fun lower(value: {{ type_name }}): Pointer = value.callWithPointer { it }
+
+    override fun lift(value: Pointer): {{ type_name }} {
+        return {{ type_name }}(value)
+    }
+
+    override fun read(buf: ByteBuffer): {{ type_name }} {
+        // The Rust code always writes pointers as 8 bytes, and will
+        // fail to compile if they don't fit.
+        return lift(Pointer(buf.getLong()))
+    }
+
+    override fun allocationSize(value: {{ type_name }}) = 8
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        // The Rust code always expects pointers written as 8 bytes,
+        // and will fail to compile if they don't fit.
+        buf.putLong(Pointer.nativeValue(lower(value)))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/OptionalTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/OptionalTemplate.kt
new file mode 100644
index 0000000000..6830b51863
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/OptionalTemplate.kt
@@ -0,0 +1,27 @@
+{%- let inner_type_name = inner_type|type_name %}
+
+public object {{ ffi_converter_name }}: FfiConverterRustBuffer<{{ inner_type_name }}?> {
+    override fun read(buf: ByteBuffer): {{ inner_type_name }}? {
+        if (buf.get().toInt() == 0) {
+            return null
+        }
+        return {{ inner_type|read_fn }}(buf)
+    }
+
+    override fun allocationSize(value: {{ inner_type_name }}?): Int {
+        if (value == null) {
+            return 1
+        } else {
+            return 1 + {{ inner_type|allocation_size_fn }}(value)
+        }
+    }
+
+    override fun write(value: {{ inner_type_name }}?, buf: ByteBuffer) {
+        if (value == null) {
+            buf.put(0)
+        } else {
+            buf.put(1)
+            {{ inner_type|write_fn }}(value, buf)
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RecordTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RecordTemplate.kt
new file mode 100644
index 0000000000..a17f4d42eb
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RecordTemplate.kt
@@ -0,0 +1,41 @@
+{%- let rec = ci.get_record_definition(name).unwrap() %}
+
+data class {{ type_name }} (
+    {%- for field in rec.fields() %}
+    var {{ field.name()|var_name }}: {{ field|type_name -}}
+    {%- match field.default_value() %}
+        {%- when Some with(literal) %} = {{ literal|render_literal(field) }}
+        {%- else %}
+    {%- endmatch -%}
+    {% if !loop.last %}, {% endif %}
+    {%- endfor %}
+) {% if contains_object_references %}: Disposable {% endif %}{
+    {% if contains_object_references %}
+    @Suppress("UNNECESSARY_SAFE_CALL") // codegen is much simpler if we unconditionally emit safe calls here
+    override fun destroy() {
+        {% call kt::destroy_fields(rec) %}
+    }
+    {% endif %}
+}
+
+public object {{ rec|ffi_converter_name }}: FfiConverterRustBuffer<{{ type_name }}> {
+    override fun read(buf: ByteBuffer): {{ type_name }} {
+        return {{ type_name }}(
+        {%- for field in rec.fields() %}
+            {{ field|read_fn }}(buf),
+        {%- endfor %}
+        )
+    }
+
+    override fun allocationSize(value: {{ type_name }}) = (
+        {%- for field in rec.fields() %}
+            {{ field|allocation_size_fn }}(value.{{ field.name()|var_name }}){% if !loop.last %} +{% endif%}
+        {%- endfor %}
+    )
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        {%- for field in rec.fields() %}
+            {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+        {%- endfor %}
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RustBufferTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RustBufferTemplate.kt
new file mode 100644
index 0000000000..6cc218e940
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RustBufferTemplate.kt
@@ -0,0 +1,66 @@
+// This is a helper for safely working with byte buffers returned from the Rust code.
+// A rust-owned buffer is represented by its capacity, its current length, and a
+// pointer to the underlying data.
+
+@Structure.FieldOrder("capacity", "len", "data")
+open class RustBuffer : Structure() {
+    @JvmField var capacity: Int = 0
+    @JvmField var len: Int = 0
+    @JvmField var data: Pointer? = null
+
+    class ByValue : RustBuffer(), Structure.ByValue
+    class ByReference : RustBuffer(), Structure.ByReference
+
+    companion object {
+        internal fun alloc(size: Int = 0) = rustCall() { status ->
+            _UniFFILib.INSTANCE.{{ ci.ffi_rustbuffer_alloc().name() }}(size, status).also {
+                if(it.data == null) {
+                   throw RuntimeException("RustBuffer.alloc() returned null data pointer (size=${size})")
+               }
+            }
+        }
+
+        internal fun free(buf: RustBuffer.ByValue) = rustCall() { status ->
+            _UniFFILib.INSTANCE.{{ ci.ffi_rustbuffer_free().name() }}(buf, status)
+        }
+    }
+
+    @Suppress("TooGenericExceptionThrown")
+    fun asByteBuffer() =
+        this.data?.getByteBuffer(0, this.len.toLong())?.also {
+            it.order(ByteOrder.BIG_ENDIAN)
+        }
+}
+
+/**
+ * The equivalent of the `*mut RustBuffer` type.
+ * Required for callbacks taking in an out pointer.
+ *
+ * Size is the sum of all values in the struct.
+ */
+class RustBufferByReference : ByReference(16) {
+    /**
+     * Set the pointed-to `RustBuffer` to the given value.
+     */
+    fun setValue(value: RustBuffer.ByValue) {
+        // NOTE: The offsets are as they are in the C-like struct.
+        val pointer = getPointer()
+        pointer.setInt(0, value.capacity)
+        pointer.setInt(4, value.len)
+        pointer.setPointer(8, value.data)
+    }
+}
+
+// This is a helper for safely passing byte references into the rust code.
+// It's not actually used at the moment, because there aren't many things that you
+// can take a direct pointer to in the JVM, and if we're going to copy something
+// then we might as well copy it into a `RustBuffer`. But it's here for API
+// completeness.
+
+@Structure.FieldOrder("len", "data")
+open class ForeignBytes : Structure() {
+    @JvmField var len: Int = 0
+    @JvmField var data: Pointer? = null
+
+    class ByValue : ForeignBytes(), Structure.ByValue
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/SequenceTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/SequenceTemplate.kt
new file mode 100644
index 0000000000..b5c699ba3b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/SequenceTemplate.kt
@@ -0,0 +1,23 @@
+{%- let inner_type_name = inner_type|type_name %}
+
+public object {{ ffi_converter_name }}: FfiConverterRustBuffer<List<{{ inner_type_name }}>> {
+    override fun read(buf: ByteBuffer): List<{{ inner_type_name }}> {
+        val len = buf.getInt()
+        return List<{{ inner_type_name }}>(len) {
+            {{ inner_type|read_fn }}(buf)
+        }
+    }
+
+    override fun allocationSize(value: List<{{ inner_type_name }}>): Int {
+        val sizeForLength = 4
+        val sizeForItems = value.map { {{ inner_type|allocation_size_fn }}(it) }.sum()
+        return sizeForLength + sizeForItems
+    }
+
+    override fun write(value: List<{{ inner_type_name }}>, buf: ByteBuffer) {
+        buf.putInt(value.size)
+        value.forEach {
+            {{ inner_type|write_fn }}(it, buf)
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/StringHelper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/StringHelper.kt
new file mode 100644
index 0000000000..d3443215c1
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/StringHelper.kt
@@ -0,0 +1,45 @@
+public object FfiConverterString: FfiConverter<String, RustBuffer.ByValue> {
+    // Note: we don't inherit from FfiConverterRustBuffer, because we use a
+    // special encoding when lowering/lifting.  We can use `RustBuffer.len` to
+    // store our length and avoid writing it out to the buffer.
+    override fun lift(value: RustBuffer.ByValue): String {
+        try {
+            val byteArr = ByteArray(value.len)
+            value.asByteBuffer()!!.get(byteArr)
+            return byteArr.toString(Charsets.UTF_8)
+        } finally {
+            RustBuffer.free(value)
+        }
+    }
+
+    override fun read(buf: ByteBuffer): String {
+        val len = buf.getInt()
+        val byteArr = ByteArray(len)
+        buf.get(byteArr)
+        return byteArr.toString(Charsets.UTF_8)
+    }
+
+    override fun lower(value: String): RustBuffer.ByValue {
+        val byteArr = value.toByteArray(Charsets.UTF_8)
+        // Ideally we'd pass these bytes to `ffi_bytebuffer_from_bytes`, but doing so would require us
+        // to copy them into a JNA `Memory`. So we might as well directly copy them into a `RustBuffer`.
+        val rbuf = RustBuffer.alloc(byteArr.size)
+        rbuf.asByteBuffer()!!.put(byteArr)
+        return rbuf
+    }
+
+    // We aren't sure exactly how many bytes our string will be once it's UTF-8
+    // encoded.  Allocate 3 bytes per unicode codepoint which will always be
+    // enough.
+    override fun allocationSize(value: String): Int {
+        val sizeForLength = 4
+        val sizeForString = value.length * 3
+        return sizeForLength + sizeForString
+    }
+
+    override fun write(value: String, buf: ByteBuffer) {
+        val byteArr = value.toByteArray(Charsets.UTF_8)
+        buf.putInt(byteArr.size)
+        buf.put(byteArr)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TimestampHelper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TimestampHelper.kt
new file mode 100644
index 0000000000..21069d7ce8
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TimestampHelper.kt
@@ -0,0 +1,38 @@
+public object FfiConverterTimestamp: FfiConverterRustBuffer<java.time.Instant> {
+    override fun read(buf: ByteBuffer): java.time.Instant {
+        val seconds = buf.getLong()
+        // Type mismatch (should be u32) but we check for overflow/underflow below
+        val nanoseconds = buf.getInt().toLong()
+        if (nanoseconds < 0) {
+            throw java.time.DateTimeException("Instant nanoseconds exceed minimum or maximum supported by uniffi")
+        }
+        if (seconds >= 0) {
+            return java.time.Instant.EPOCH.plus(java.time.Duration.ofSeconds(seconds, nanoseconds))
+        } else {
+            return java.time.Instant.EPOCH.minus(java.time.Duration.ofSeconds(-seconds, nanoseconds))
+        }
+    }
+
+    // 8 bytes for seconds, 4 bytes for nanoseconds
+    override fun allocationSize(value: java.time.Instant) = 12
+
+    override fun write(value: java.time.Instant, buf: ByteBuffer) {
+        var epochOffset = java.time.Duration.between(java.time.Instant.EPOCH, value)
+
+        var sign = 1
+        if (epochOffset.isNegative()) {
+            sign = -1
+            epochOffset = epochOffset.negated()
+        }
+
+        if (epochOffset.nano < 0) {
+            // Java docs provide guarantee that nano will always be positive, so this should be impossible
+            // See: https://docs.oracle.com/javase/8/docs/api/java/time/Instant.html
+            throw IllegalArgumentException("Invalid timestamp, nano value must be non-negative")
+        }
+
+        buf.putLong(sign * epochOffset.seconds)
+        // Type mismatch (should be u32) but since values will always be between 0 and 999,999,999 it should be OK
+        buf.putInt(epochOffset.nano)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TopLevelFunctionTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TopLevelFunctionTemplate.kt
new file mode 100644
index 0000000000..180a64066a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TopLevelFunctionTemplate.kt
@@ -0,0 +1,17 @@
+{%- match func.throws_type() -%}
+{%- when Some with (throwable) %}
+@Throws({{ throwable|type_name }}::class)
+{%- else -%}
+{%- endmatch %}
+{%- match func.return_type() -%}
+{%- when Some with (return_type) %}
+
+fun {{ func.name()|fn_name }}({%- call kt::arg_list_decl(func) -%}): {{ return_type|type_name }} {
+    return {{ return_type|lift_fn }}({% call kt::to_ffi_call(func) %})
+}
+
+{% when None %}
+
+fun {{ func.name()|fn_name }}({% call kt::arg_list_decl(func) %}) =
+    {% call kt::to_ffi_call(func) %}
+{% endmatch %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Types.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Types.kt
new file mode 100644
index 0000000000..6379971b76
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Types.kt
@@ -0,0 +1,94 @@
+{%- import "macros.kt" as kt %}
+
+{%- for type_ in ci.iter_types() %}
+{%- let type_name = type_|type_name %}
+{%- let ffi_converter_name = type_|ffi_converter_name %}
+{%- let canonical_type_name = type_|canonical_name %}
+{%- let contains_object_references = ci.item_contains_object_references(type_) %}
+
+{#
+ # Map `Type` instances to an include statement for that type.
+ #
+ # There is a companion match in `KotlinCodeOracle::create_code_type()` which performs a similar function for the
+ # Rust code.
+ #
+ #   - When adding additional types here, make sure to also add a match arm to that function.
+ #   - To keep things managable, let's try to limit ourselves to these 2 mega-matches
+ #}
+{%- match type_ %}
+
+{%- when Type::Boolean %}
+{%- include "BooleanHelper.kt" %}
+
+{%- when Type::Int8 %}
+{%- include "Int8Helper.kt" %}
+
+{%- when Type::Int16 %}
+{%- include "Int16Helper.kt" %}
+
+{%- when Type::Int32 %}
+{%- include "Int32Helper.kt" %}
+
+{%- when Type::Int64 %}
+{%- include "Int64Helper.kt" %}
+
+{%- when Type::UInt8 %}
+{%- include "UInt8Helper.kt" %}
+
+{%- when Type::UInt16 %}
+{%- include "UInt16Helper.kt" %}
+
+{%- when Type::UInt32 %}
+{%- include "UInt32Helper.kt" %}
+
+{%- when Type::UInt64 %}
+{%- include "UInt64Helper.kt" %}
+
+{%- when Type::Float32 %}
+{%- include "Float32Helper.kt" %}
+
+{%- when Type::Float64 %}
+{%- include "Float64Helper.kt" %}
+
+{%- when Type::String %}
+{%- include "StringHelper.kt" %}
+
+{%- when Type::Enum(name) %}
+{% include "EnumTemplate.kt" %}
+
+{%- when Type::Error(name) %}
+{% include "ErrorTemplate.kt" %}
+
+{%- when Type::Object(name) %}
+{% include "ObjectTemplate.kt" %}
+
+{%- when Type::Record(name) %}
+{% include "RecordTemplate.kt" %}
+
+{%- when Type::Optional(inner_type) %}
+{% include "OptionalTemplate.kt" %}
+
+{%- when Type::Sequence(inner_type) %}
+{% include "SequenceTemplate.kt" %}
+
+{%- when Type::Map(key_type, value_type) %}
+{% include "MapTemplate.kt" %}
+
+{%- when Type::CallbackInterface(name) %}
+{% include "CallbackInterfaceTemplate.kt" %}
+
+{%- when Type::Timestamp %}
+{% include "TimestampHelper.kt" %}
+
+{%- when Type::Duration %}
+{% include "DurationHelper.kt" %}
+
+{%- when Type::Custom { name, builtin } %}
+{% include "CustomTypeTemplate.kt" %}
+
+{%- when Type::External { crate_name, name } %}
+{% include "ExternalTypeTemplate.kt" %}
+
+{%- else %}
+{%- endmatch %}
+{%- endfor %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt16Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt16Helper.kt
new file mode 100644
index 0000000000..279a8fa91b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt16Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterUShort: FfiConverter<UShort, Short> {
+    override fun lift(value: Short): UShort {
+        return value.toUShort()
+    }
+
+    override fun read(buf: ByteBuffer): UShort {
+        return lift(buf.getShort())
+    }
+
+    override fun lower(value: UShort): Short {
+        return value.toShort()
+    }
+
+    override fun allocationSize(value: UShort) = 2
+
+    override fun write(value: UShort, buf: ByteBuffer) {
+        buf.putShort(value.toShort())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt32Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt32Helper.kt
new file mode 100644
index 0000000000..da7b5b28d6
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt32Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterUInt: FfiConverter<UInt, Int> {
+    override fun lift(value: Int): UInt {
+        return value.toUInt()
+    }
+
+    override fun read(buf: ByteBuffer): UInt {
+        return lift(buf.getInt())
+    }
+
+    override fun lower(value: UInt): Int {
+        return value.toInt()
+    }
+
+    override fun allocationSize(value: UInt) = 4
+
+    override fun write(value: UInt, buf: ByteBuffer) {
+        buf.putInt(value.toInt())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt64Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt64Helper.kt
new file mode 100644
index 0000000000..44d27ad36b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt64Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterULong: FfiConverter<ULong, Long> {
+    override fun lift(value: Long): ULong {
+        return value.toULong()
+    }
+
+    override fun read(buf: ByteBuffer): ULong {
+        return lift(buf.getLong())
+    }
+
+    override fun lower(value: ULong): Long {
+        return value.toLong()
+    }
+
+    override fun allocationSize(value: ULong) = 8
+
+    override fun write(value: ULong, buf: ByteBuffer) {
+        buf.putLong(value.toLong())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt8Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt8Helper.kt
new file mode 100644
index 0000000000..b6d176603e
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt8Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterUByte: FfiConverter<UByte, Byte> {
+    override fun lift(value: Byte): UByte {
+        return value.toUByte()
+    }
+
+    override fun read(buf: ByteBuffer): UByte {
+        return lift(buf.get())
+    }
+
+    override fun lower(value: UByte): Byte {
+        return value.toByte()
+    }
+
+    override fun allocationSize(value: UByte) = 1
+
+    override fun write(value: UByte, buf: ByteBuffer) {
+        buf.put(value.toByte())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/macros.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/macros.kt
new file mode 100644
index 0000000000..2888b23873
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/macros.kt
@@ -0,0 +1,82 @@
+{#
+// Template to call into rust. Used in several places.
+// Variable names in `arg_list_decl` should match up with arg lists
+// passed to rust via `_arg_list_ffi_call`
+#}
+
+{%- macro to_ffi_call(func) -%}
+    {%- match func.throws_type() %}
+    {%- when Some with (e) %}
+    rustCallWithError({{ e|type_name}})
+    {%- else %}
+    rustCall()
+    {%- endmatch %} { _status ->
+    _UniFFILib.INSTANCE.{{ func.ffi_func().name() }}({% call _arg_list_ffi_call(func) -%}{% if func.arguments().len() > 0 %},{% endif %} _status)
+}
+{%- endmacro -%}
+
+{%- macro to_ffi_call_with_prefix(prefix, func) %}
+    {%- match func.throws_type() %}
+    {%- when Some with (e) %}
+    rustCallWithError({{ e|type_name}})
+    {%- else %}
+    rustCall()
+    {%- endmatch %} { _status ->
+    _UniFFILib.INSTANCE.{{ func.ffi_func().name() }}(
+        {{- prefix }}, {% call _arg_list_ffi_call(func) %}{% if func.arguments().len() > 0 %}, {% endif %} _status)
+}
+{%- endmacro %}
+
+{%- macro _arg_list_ffi_call(func) %}
+    {%- for arg in func.arguments() %}
+        {{- arg|lower_fn }}({{ arg.name()|var_name }})
+        {%- if !loop.last %}, {% endif %}
+    {%- endfor %}
+{%- endmacro -%}
+
+{#-
+// Arglist as used in kotlin declarations of methods, functions and constructors.
+// Note the var_name and type_name filters.
+-#}
+
+{% macro arg_list_decl(func) %}
+    {%- for arg in func.arguments() -%}
+        {{ arg.name()|var_name }}: {{ arg|type_name -}}
+        {%- match arg.default_value() %}
+        {%- when Some with(literal) %} = {{ literal|render_literal(arg) }}
+        {%- else %}
+        {%- endmatch %}
+        {%- if !loop.last %}, {% endif -%}
+    {%- endfor %}
+{%- endmacro %}
+
+{% macro arg_list_protocol(func) %}
+    {%- for arg in func.arguments() -%}
+        {{ arg.name()|var_name }}: {{ arg|type_name -}}
+        {%- if !loop.last %}, {% endif -%}
+    {%- endfor %}
+{%- endmacro %}
+{#-
+// Arglist as used in the _UniFFILib function declations.
+// Note unfiltered name but ffi_type_name filters.
+-#}
+{%- macro arg_list_ffi_decl(func) %}
+    {%- for arg in func.arguments() %}
+        {{- arg.name()|var_name }}: {{ arg.type_().borrow()|ffi_type_name -}},
+    {%- endfor %}
+    _uniffi_out_err: RustCallStatus
+{%- endmacro -%}
+
+// Macro for destroying fields
+{%- macro destroy_fields(member) %}
+    Disposable.destroy(
+    {%- for field in member.fields() %}
+        this.{{ field.name()|var_name }}{%- if !loop.last %}, {% endif -%}
+    {% endfor -%})
+{%- endmacro -%}
+
+{%- macro ffi_function_definition(func) %}
+fun {{ func.name()|fn_name }}(
+    {%- call arg_list_ffi_decl(func) %}
+){%- match func.return_type() -%}{%- when Some with (type_) %}: {{ type_|ffi_type_name }}{% when None %}: Unit{% endmatch %}
+{% endmacro %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/wrapper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/wrapper.kt
new file mode 100644
index 0000000000..9cb104292c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/wrapper.kt
@@ -0,0 +1,48 @@
+// This file was autogenerated by some hot garbage in the `uniffi` crate.
+// Trust me, you don't want to mess with it!
+
+@file:Suppress("NAME_SHADOWING")
+
+package {{ config.package_name() }};
+
+// Common helper code.
+//
+// Ideally this would live in a separate .kt file where it can be unittested etc
+// in isolation, and perhaps even published as a re-useable package.
+//
+// However, it's important that the detils of how this helper code works (e.g. the
+// way that different builtin types are passed across the FFI) exactly match what's
+// expected by the Rust code on the other side of the interface. In practice right
+// now that means coming from the exact some version of `uniffi` that was used to
+// compile the Rust component. The easiest way to ensure this is to bundle the Kotlin
+// helpers directly inline like we're doing here.
+
+import com.sun.jna.Library
+import com.sun.jna.Native
+import com.sun.jna.Pointer
+import com.sun.jna.Structure
+import com.sun.jna.ptr.ByReference
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
+
+{%- for imported_class in self.imports() %}
+import {{ imported_class }}
+{%- endfor %}
+
+{% include "RustBufferTemplate.kt" %}
+{% include "FfiConverterTemplate.kt" %}
+{% include "Helpers.kt" %}
+
+// Contains loading, initialization code,
+// and the FFI Function declarations in a com.sun.jna.Library.
+{% include "NamespaceLibraryTemplate.kt" %}
+
+// Public interface members begin here.
+{{ type_helper_code }}
+
+{%- for func in ci.function_definitions() %}
+{%- include "TopLevelFunctionTemplate.kt" %}
+{%- endfor %}
+
+
+{% import "macros.kt" as kt %}