rust facing cpp ffi defined, safely linked

cpp/vector_engine_ffi.cpp

@@ -1,6 +1,16 @@
 #include "vector_engine_ffi.h"
+#include "vector_engine.h"
 
-struct NativeVectorEngine {};
+#include <string>
+#include <vector>
+
+struct NativeVectorEngine {
+    VectorEngine engine;
+};
+
+struct NativeSearchResults {
+    std::vector<SearchResult> results;
+};
 
 extern "C" NativeVectorEngine* native_vector_engine_new() {
     return new NativeVectorEngine();
@@ -9,3 +19,33 @@ extern "C" NativeVectorEngine* native_vector_engine_new() {
 extern "C" void native_vector_engine_free(NativeVectorEngine* engine) {
     delete engine;
 }
+
+extern "C" size_t native_search_results_len(const NativeSearchResults* results) {
+    return results->results.size();
+}
+
+extern "C" const char* native_search_results_id_at(const NativeSearchResults* results, size_t index) {
+    return results->results[index].id.c_str();
+}
+
+extern "C" float native_search_results_score_at(const NativeSearchResults* results, size_t index) {
+    return results->results[index].score;
+}
+
+extern "C" void native_search_results_free(NativeSearchResults* results) {
+    delete results;
+}
+
+extern "C" void native_vector_engine_insert(NativeVectorEngine* engine, const char* id, const float* vector, size_t len) {
+    engine->engine.insert(std::string(id), vector, len);
+}
+
+extern "C" bool native_vector_engine_delete(NativeVectorEngine* engine, const char* id) {
+    return engine->engine.erase(std::string(id));
+}
+
+extern "C" NativeSearchResults* native_vector_engine_search(const NativeVectorEngine* engine, const float* query, size_t len, size_t k) {
+    auto* results = new NativeSearchResults();
+    results->results = engine->engine.search(query, len, k);
+    return results;
+}

cpp/vector_engine_ffi.h

@@ -8,29 +8,13 @@ struct NativeSearchResults;
 
 extern "C" {
 
-    // subject to change
     NativeVectorEngine* native_vector_engine_new();
     void native_vector_engine_free(NativeVectorEngine* engine);
 
     // insert / delete / search
-    void native_vector_engine_insert(
-        NativeVectorEngine* engine,
-        const char* id,
-        const float* vector,
-        size_t len
-    );
-
-    bool native_vector_engine_delete(
-        NativeVectorEngine* engine,
-        const char* id
-    );
-
-    NativeSearchResults* native_vector_engine_search(
-        const NativeVectorEngine* engine,
-        const float* query,
-        size_t len,
-        size_t k
-    );
+    void native_vector_engine_insert(NativeVectorEngine* engine, const char* id, const float* vector, size_t len);
+    bool native_vector_engine_delete(NativeVectorEngine* engine, const char* id);
+    NativeSearchResults* native_vector_engine_search(NativeVectorEngine* engine, const float* query, size_t len, size_t k);
 
     // working with pointers to send info back to rust
     size_t native_search_results_len(const NativeSearchResults* results);

crates/vdb-ffi/Cargo.toml

@@ -8,3 +8,4 @@ path = "src/lib.rs"
 
 [build-dependencies]
 bindgen = "0.72"
+cc = "1"

crates/vdb-ffi/build.rs

@@ -1,8 +1,19 @@
-use std::{env, path::PathBuf};
+use std::path::PathBuf;
 
 fn main() {
-    println!("cargo:rerun-if-changed=../../cpp/vector_engine_ffi.h");
+    // linking the compiled cpp files
+    let cpp_dir = PathBuf::from("../../cpp");
+    let mut native_build = cc::Build::new();
+    native_build
+        .cpp(true)
+        .std("c++17")
+        .include(&cpp_dir)
+        .file(cpp_dir.join("vector_engine.cpp"))
+        .file(cpp_dir.join("vector_engine_ffi.cpp"));
 
+    native_build.compile("vector_engine_native");
+
+    // generates rust declarations based of cpp ffi
     let bindings = bindgen::Builder::default()
         .header("../../cpp/vector_engine_ffi.h")
         .clang_arg("-xc++")

crates/vdb-ffi/src/engine.rs

@@ -21,8 +21,7 @@ pub struct FfiSearchResults {
     handle: *mut NativeSearchResults,
 }
 
-// The wrapper owns the native handle and is always accessed behind higher-level
-// synchronization in the API layer.
+// Send is built into Rust as a trait, allows FfiVectorEngine to be moved between threads safely.
 unsafe impl Send for FfiVectorEngine {}
 
 impl FfiVectorEngine {