1 files changed, 94 insertions, 1 deletions
diff --git a/src/javascript/jsc/bindings/JSBuffer.cpp b/src/javascript/jsc/bindings/JSBuffer.cpp
index ab5e0341d..8f56703ce 100644
--- a/src/javascript/jsc/bindings/JSBuffer.cpp
+++ b/src/javascript/jsc/bindings/JSBuffer.cpp
@@ -798,7 +798,100 @@ static inline JSC::EncodedJSValue jsBufferPrototypeFunction_fillBody(JSC::JSGlob
 {
     auto& vm = JSC::getVM(lexicalGlobalObject);
 
-    return JSC::JSValue::encode(jsUndefined());
+    if (callFrame->argumentCount() < 1) {
+        return JSValue::encode(castedThis);
+    }
+
+    auto value = callFrame->uncheckedArgument(0);
+
+    if (!value.isString()) {
+        auto value_ = value.toInt32() & 0xFF;
+
+        auto value_uint8 = static_cast<uint8_t>(value_);
+        auto length = castedThis->byteLength();
+        auto start = 0;
+        auto end = length;
+        if (callFrame->argumentCount() > 1) {
+            if (auto start_ = callFrame->uncheckedArgument(1).tryGetAsUint32Index()) {
+                start = start_.value();
+            } else {
+                return throwVMError(lexicalGlobalObject, JSC::throwScope, createRangeError(lexicalGlobalObject, "start out of range"_s));
+            }
+            if (callFrame->argumentCount() > 2) {
+                if (auto end_ = callFrame->uncheckedArgument(2).tryGetAsUint32Index()) {
+                    end = end_.value();
+                } else {
+                    return throwVMError(lexicalGlobalObject, JSC::throwScope, createRangeError(lexicalGlobalObject, "end out of range"_s));
+                }
+            }
+        }
+        if (start > end) {
+            return throwVMError(lexicalGlobalObject, JSC::throwScope, createRangeError(lexicalGlobalObject, "start out of range"_s));
+        }
+        if (end > length) {
+            return throwVMError(lexicalGlobalObject, JSC::throwScope, createRangeError(lexicalGlobalObject, "end out of range"_s));
+        }
+        auto startPtr = castedThis->typedVector() + start;
+        auto endPtr = castedThis->typedVector() + end;
+        memset(startPtr, value_uint8, endPtr - startPtr);
+        return JSValue::encode(castedThis);
+    }
+
+    {
+        EnsureStillAliveScope value_ = callFrame->argument(0);
+
+        unsigned int length = castedThis->byteLength();
+        unsigned int start = 0;
+        unsigned int end = length;
+        WebCore::BufferEncodingType encoding = WebCore::BufferEncodingType::utf8;
+        if (callFrame->argumentCount() > 1) {
+            if (auto start_ = callFrame->uncheckedArgument(1).tryGetAsUint32Index()) {
+                start = start_.value();
+            } else {
+                throwVMError(lexicalGlobalObject, JSC::throwScope, createRangeError(lexicalGlobalObject, "start out of range"_s));
+                return JSC::JSValue::encode(jsUndefined());
+            }
+            if (callFrame->argumentCount() > 2) {
+                if (auto end_ = callFrame->uncheckedArgument(2).tryGetAsUint32Index()) {
+                    end = end_.value();
+                } else {
+                    throwVMError(lexicalGlobalObject, JSC::throwScope, createRangeError(lexicalGlobalObject, "end out of range"_s));
+                    return JSC::JSValue::encode(jsUndefined());
+                }
+            }
+
+            if (callFrame->argumentCount() > 3) {
+                auto encoding_ = callFrame->uncheckedArgument(3).toString(lexicalGlobalObject);
+
+                std::optional<BufferEncodingType> encoded = parseEnumeration<BufferEncodingType>(*lexicalGlobalObject, arg1.value());
+                if (!encoded) {
+                    throwTypeError(lexicalGlobalObject, scope, "Invalid encoding");
+                    return JSC::JSValue::encode(jsUndefined());
+                }
+
+                encoding = encoded.value();
+            }
+        }
+        if (start > end) {
+            throwVMError(lexicalGlobalObject, JSC::throwScope, createRangeError(lexicalGlobalObject, "start out of range"_s));
+            return JSC::JSValue::encode(jsUndefined());
+        }
+        if (end > length) {
+            throwVMError(lexicalGlobalObject, JSC::throwScope, createRangeError(lexicalGlobalObject, "end out of range"_s));
+            return JSC::JSValue::encode(jsUndefined());
+        }
+
+        auto startPtr = castedThis->typedVector() + start;
+
+        ZigString str = Zig::toString(value.toString(lexicalGlobalObject));
+
+        Bun__ArrayBuffer buf;
+        JSC__JSValue__asArrayBuffer_(JSC::JSValue::encode(castedThis), lexicalGlobalObject,
+            &buf);
+        Bun__Buffer_fill(lexicalGlobalObject, &buf, &str, start, end, encoding);
+
+        return JSValue::encode(castedThis);
+    }
 }
 static inline JSC::EncodedJSValue jsBufferPrototypeFunction_includesBody(JSC::JSGlobalObject* lexicalGlobalObject, JSC::CallFrame* callFrame, typename IDLOperation<JSBuffer>::ClassParameter castedThis)
 {