perf: avoid creating array in native

Author: ronag

binding.cc

@@ -985,7 +985,7 @@ NAPI_METHOD(db_get_many) {
 
   struct State {
     std::vector<uint8_t> data;
-    std::vector<std::optional<size_t>> sizes;
+    std::vector<int32_t> sizes;
   };
 
   runAsync<State>(
@@ -1018,14 +1018,14 @@ NAPI_METHOD(db_get_many) {
 
         auto push = [&](rocksdb::Slice* slice){
           if (slice) {
-            state.sizes.push_back(slice->size());
+            state.sizes.push_back(static_cast<int32_t>(slice->size()));
             std::copy_n(slice->data(), slice->size(), std::back_inserter(state.data));
 
             if (state.data.size() & 0x7) {
               state.data.resize((state.data.size() | 0x7) + 1);
             }
           } else {
-            state.sizes.push_back(std::nullopt);
+            state.sizes.push_back(-1);
           }
         };
 
@@ -1038,20 +1038,12 @@ NAPI_METHOD(db_get_many) {
       [=](auto& state, auto env, auto& argv) {
         argv.resize(3);
 
-        const auto count = state.sizes.size();
-
-        NAPI_STATUS_RETURN(napi_create_array_with_length(env, count, &argv[1]));
-
-        for (uint32_t idx = 0; idx < count; idx++) {
-          const auto& maybeSize = state.sizes[idx];
-
-          napi_value element;
-          if (maybeSize) {
-            NAPI_STATUS_RETURN(napi_create_uint32(env, *maybeSize, &element));
-          } else {
-            NAPI_STATUS_RETURN(napi_get_undefined(env, &element));
-          }
-          NAPI_STATUS_RETURN(napi_set_element(env, argv[1], idx, element));
+        if (state.sizes.size() > 0) {
+          auto sizes = std::make_unique<std::vector<int32_t>>(std::move(state.sizes));
+          NAPI_STATUS_RETURN(napi_create_external_buffer(env, sizes->size() * 4, sizes->data(), Finalize<std::vector<int32_t>>, sizes.get(), &argv[1]));
+          sizes.release();
+        } else {
+          NAPI_STATUS_RETURN(napi_get_undefined(env, &argv[1]));
         }
 
         if (state.data.size() > 0) {
@@ -1304,7 +1296,7 @@ NAPI_METHOD(iterator_nextv) {
 
   struct State {
     std::vector<uint8_t> data;
-    std::vector<std::optional<size_t>> sizes;
+    std::vector<int32_t> sizes;
     bool finished = false;
   };
 
@@ -1322,7 +1314,7 @@ NAPI_METHOD(iterator_nextv) {
 
         auto push = [&](const std::optional<rocksdb::Slice>& slice){
           if (slice) {
-            state.sizes.push_back(slice->size());
+            state.sizes.push_back(static_cast<int32_t>(slice->size()));
             std::copy_n(slice->data(), slice->size(), std::back_inserter(state.data));
 
             if (state.data.size() & 0x7) {
@@ -1331,7 +1323,7 @@ NAPI_METHOD(iterator_nextv) {
 
             bytesRead += slice->size();
           } else {
-            state.sizes.push_back(std::nullopt);
+            state.sizes.push_back(-1);
           }
         };
 
@@ -1372,20 +1364,12 @@ NAPI_METHOD(iterator_nextv) {
       [=](auto& state, auto env, auto& argv) {
         argv.resize(4);
 
-        const auto count = state.sizes.size();
-
-        NAPI_STATUS_RETURN(napi_create_array_with_length(env, count, &argv[1]));
-
-        for (uint32_t idx = 0; idx < count; idx++) {
-          const auto& maybeSize = state.sizes[idx];
-
-          napi_value element;
-          if (maybeSize) {
-            NAPI_STATUS_RETURN(napi_create_uint32(env, *maybeSize, &element));
-          } else {
-            NAPI_STATUS_RETURN(napi_get_undefined(env, &element));
-          }
-          NAPI_STATUS_RETURN(napi_set_element(env, argv[1], idx, element));
+        if (state.sizes.size() > 0) {
+          auto sizes = std::make_unique<std::vector<int32_t>>(std::move(state.sizes));
+          NAPI_STATUS_RETURN(napi_create_external_buffer(env, sizes->size() * 4, sizes->data(), Finalize<std::vector<int32_t>>, sizes.get(), &argv[1]));
+          sizes.release();
+        } else {
+          NAPI_STATUS_RETURN(napi_get_undefined(env, &argv[1]));
         }
 
         if (state.data.size() > 0) {

index.js

@@ -152,23 +152,25 @@ class RocksLevel extends AbstractLevel {
     const { valueEncoding } = options ?? EMPTY
     try {
       this[kRef]()
-      binding.db_get_many(this[kContext], keys, options ?? EMPTY, (err, sizes, buffer) => {
+      binding.db_get_many(this[kContext], keys, options ?? EMPTY, (err, sizes, data) => {
         if (err) {
           callback(err)
         } else {
-          buffer ??= Buffer.alloc(0)
+          data ??= Buffer.alloc(0)
+          sizes ??= Buffer.alloc(0)
           const val = []
           let offset = 0
-          for (const size of sizes) {
-            if (size == null) {
+          const sizes32 = new Int32Array(sizes.buffer, sizes.byteOffset, sizes.byteLength / 4)
+          for (const size of sizes32) {
+            if (size < 0) {
               val.push(undefined)
             } else {
               if (!valueEncoding || valueEncoding === 'buffer') {
-                val.push(buffer.subarray(offset, offset + size))
+                val.push(data.subarray(offset, offset + size))
               } else if (valueEncoding === 'slice') {
-                val.push({ buffer, byteOffset: offset, byteLength: size })
+                val.push({ buffer: data, byteOffset: offset, byteLength: size })
               } else {
-                val.push(buffer.toString(valueEncoding, offset, offset + size))
+                val.push(data.toString(valueEncoding, offset, offset + size))
               }
               offset += size
               if (offset & 0x7) {

util.js

@@ -5,15 +5,17 @@ function handleNextv (err, sizes, buffer, finished, options, callback) {
     callback(err)
   } else {
     buffer ??= Buffer.alloc(0)
+    sizes ??= Buffer.alloc(0)
 
     const { keyEncoding, valueEncoding } = options ?? {}
 
     const rows = []
     let offset = 0
-    for (let n = 0; n < sizes.length; n++) {
-      const size = sizes[n]
+    const sizes32 = new Int32Array(sizes.buffer, sizes.byteOffset, sizes.byteLength / 4)
+    for (let n = 0; n < sizes32.length; n++) {
+      const size = sizes32[n]
       const encoding = n & 1 ? valueEncoding : keyEncoding
-      if (size == null) {
+      if (size < 0) {
         rows.push(undefined)
       } else {
         if (!encoding || encoding === 'buffer') {