From 7328b6f8111f2fdc7c676cb90c25eb5e421f0a79 Mon Sep 17 00:00:00 2001
From: Robert Nagy <ronagy@icloud.com>
Date: Mon, 29 Jul 2024 07:30:54 +0200
Subject: [PATCH] fixup: fast call

---
 lib/buffer.js      | 14 ++++----------
 src/node_buffer.cc | 41 ++++++++++++++++++++++++++++++++++++++---
 2 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/lib/buffer.js b/lib/buffer.js
index 54fa97202057c4..23149e09d64a0c 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -58,7 +58,7 @@ const {
   byteLengthUtf8,
   compare: _compare,
   compareOffset,
-  copyArrayBuffer,
+  copy: _copy,
   createFromString,
   fill: bindingFill,
   isAscii: bindingIsAscii,
@@ -204,7 +204,7 @@ function toInteger(n, defaultVal) {
   return defaultVal;
 }
 
-function _copy(source, target, targetStart, sourceStart, sourceEnd) {
+function copyImpl(source, target, targetStart, sourceStart, sourceEnd) {
   if (!isUint8Array(source))
     throw new ERR_INVALID_ARG_TYPE('source', ['Buffer', 'Uint8Array'], source);
   if (!isUint8Array(target))
@@ -253,13 +253,7 @@ function _copyActual(source, target, targetStart, sourceStart, sourceEnd) {
     return 0;
 
   if (sourceStart !== 0 || sourceEnd < source.length) {
-    copyArrayBuffer(
-      target.buffer,
-      target.byteOffset + targetStart,
-      source.buffer,
-      source.byteOffset + sourceStart,
-      nb,
-    );
+    _copy(source, target, targetStart, sourceStart, sourceEnd);
   } else {
     TypedArrayPrototypeSet(target, source, targetStart);
   }
@@ -816,7 +810,7 @@ ObjectDefineProperty(Buffer.prototype, 'offset', {
 
 Buffer.prototype.copy =
   function copy(target, targetStart, sourceStart, sourceEnd) {
-    return _copy(this, target, targetStart, sourceStart, sourceEnd);
+    return copyImpl(this, target, targetStart, sourceStart, sourceEnd);
   };
 
 // No need to verify that "buf.length <= MAX_UINT32" since it's a read-only
diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index 300060f9d24290..def87d226fce70 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -569,7 +569,7 @@ void StringSlice(const FunctionCallbackInfo<Value>& args) {
 }
 
 // bytesCopied = copy(buffer, target[, targetStart][, sourceStart][, sourceEnd])
-void Copy(const FunctionCallbackInfo<Value> &args) {
+void SlowCopy(const FunctionCallbackInfo<Value> &args) {
   Environment* env = Environment::GetCurrent(args);
 
   THROW_AND_RETURN_UNLESS_BUFFER(env, args[0]);
@@ -606,6 +606,39 @@ void Copy(const FunctionCallbackInfo<Value> &args) {
   args.GetReturnValue().Set(to_copy);
 }
 
+size_t FastCopy(Local<Value> receiver,
+                  Local<Value> source_obj,
+                  Local<Value> target_obj,
+                  size_t target_start,
+                  size_t source_start,
+                  size_t source_end) {
+  ArrayBufferViewContents<char> source(source_obj);
+  SPREAD_BUFFER_ARG(target_obj, target);
+
+  // Copy 0 bytes; we're done
+  if (target_start >= target_length || source_start >= source_end)
+    return 0;
+
+  if (source_start > source.length()) {
+    // TODO (fix): V8 12.8 allows throwing in fast call.
+    assert(false);
+    return 0;
+  }
+
+  if (source_end - source_start > target_length - target_start)
+    source_end = source_start + target_length - target_start;
+
+  uint32_t to_copy = std::min<size_t>(
+      std::min<size_t>(source_end - source_start, target_length - target_start),
+      source.length() - source_start);
+
+  memmove(target_data + target_start, source.data() + source_start, to_copy);
+
+  return to_copy;
+}
+
+static v8::CFunction fast_copy(
+    v8::CFunction::Make(FastCopy));
 
 void Fill(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
@@ -1275,7 +1308,7 @@ void Initialize(Local<Object> target,
                             "byteLengthUtf8",
                             SlowByteLengthUtf8,
                             &fast_byte_length_utf8);
-  SetMethod(context, target, "copy", Copy);
+  SetFastMethod(context, target, "copy", SlowCopy, &fast_copy);
   SetMethodNoSideEffect(context, target, "compare", Compare);
   SetMethodNoSideEffect(context, target, "compareOffset", CompareOffset);
   SetMethod(context, target, "fill", Fill);
@@ -1334,7 +1367,9 @@ void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
   registry->Register(SlowByteLengthUtf8);
   registry->Register(fast_byte_length_utf8.GetTypeInfo());
   registry->Register(FastByteLengthUtf8);
-  registry->Register(Copy);
+  registry->Register(SlowCopy);
+  registry->Register(fast_copy.GetTypeInfo());
+  registry->Register(FastCopy);
   registry->Register(Compare);
   registry->Register(CompareOffset);
   registry->Register(Fill);