Fixed JSBuffer write issues (#1175)

3 files changed, 44 insertions, 16 deletions

diff --git a/src/bun.js/bindings/JSBuffer.cpp b/src/bun.js/bindings/JSBuffer.cpp
index 396e643d5..4b509f257 100644
--- a/src/bun.js/bindings/JSBuffer.cpp
+++ b/src/bun.js/bindings/JSBuffer.cpp
@@ -1192,12 +1192,12 @@ static inline JSC::EncodedJSValue jsBufferPrototypeFunction_writeBody(JSC::JSGlo
 
     if (callFrame->argumentCount() > 1) {
         if (arg1.value().isAnyInt()) {
-            int32_t ioffset = arg1.value().toInt32(lexicalGlobalObject);
+            int32_t ioffset = arg1.value().toUInt32(lexicalGlobalObject);
             if (ioffset < 0) {
                 throwTypeError(lexicalGlobalObject, scope, "Offset must be a positive integer"_s);
                 return JSC::JSValue::encode(jsUndefined());
             }
-            offset = static_cast<uint32_t>(ioffset);
+            offset = ioffset;
         } else if (arg1.value().isString()) {
             std::optional<BufferEncodingType> encoded = parseEnumeration<BufferEncodingType>(*lexicalGlobalObject, arg1.value());
             if (!encoded) {
@@ -1209,24 +1209,21 @@ static inline JSC::EncodedJSValue jsBufferPrototypeFunction_writeBody(JSC::JSGlo
         }
     }
 
-    if (callFrame->argumentCount() > 2) {
-        length = static_cast<uint32_t>(callFrame->argument(2).toInt32(lexicalGlobalObject));
-    }
-
-    length -= std::min(offset, length);
-
     if (UNLIKELY(length < offset)) {
         RELEASE_AND_RETURN(scope, JSC::JSValue::encode(JSC::jsNumber(0)));
     }
 
     if (callFrame->argumentCount() > 2) {
-        std::optional<BufferEncodingType> encoded = parseEnumeration<BufferEncodingType>(*lexicalGlobalObject, callFrame->argument(3));
-        if (!encoded) {
-            throwTypeError(lexicalGlobalObject, scope, "Invalid encoding"_s);
-            return JSC::JSValue::encode(jsUndefined());
-        }
+        uint32_t arg_len = 0;
+        arg_len = callFrame->argument(2).toUInt32(lexicalGlobalObject);
+        length = std::min(arg_len, length-offset);
+    }
 
-        encoding = encoded.value();
+    if (callFrame->argumentCount() > 2) {
+        std::optional<BufferEncodingType> parsedEncoding = parseEnumeration<BufferEncodingType>(*lexicalGlobalObject, callFrame->argument(3));
+        if (parsedEncoding.has_value()) {
+            encoding = parsedEncoding.value();
+        }
     }
 
     auto view = str->tryGetValue(lexicalGlobalObject);
@@ -1653,4 +1650,4 @@ void toBuffer(JSC::JSGlobalObject* lexicalGlobalObject, JSC::JSUint8Array* uint8
     auto* dataView = JSC::JSDataView::create(lexicalGlobalObject, lexicalGlobalObject->typedArrayStructure(JSC::TypeDataView), uint8Array->possiblySharedBuffer(), uint8Array->byteOffset(), uint8Array->length());
     // putDirectWithTransition doesn't work here
     object->putDirectWithoutTransition(vm, clientData->builtinNames().dataViewPublicName(), dataView, JSC::PropertyAttribute::DontEnum | JSC::PropertyAttribute::DontDelete | JSC::PropertyAttribute::ReadOnly);
-}
\ No newline at end of file
+}
diff --git a/src/string_immutable.zig b/src/string_immutable.zig
index 8503d3418..48d591eff 100644
--- a/src/string_immutable.zig
+++ b/src/string_immutable.zig
@@ -1402,7 +1402,7 @@ pub fn copyLatin1IntoUTF8StopOnNonASCII(buf_: []u8, comptime Type: type, latin1_
             }
 
             {
-                const end = latin1.ptr + latin1.len;
+                const end = latin1.ptr + @minimum(buf.len, latin1.len);
                 assert(@ptrToInt(latin1.ptr + 8) > @ptrToInt(end));
                 const start_ptr = @ptrToInt(buf.ptr);
                 const start_ptr_latin1 = @ptrToInt(latin1.ptr);
diff --git a/test/bun.js/buffer.test.js b/test/bun.js/buffer.test.js
index 0b3abd270..3c25450f7 100644
--- a/test/bun.js/buffer.test.js
+++ b/test/bun.js/buffer.test.js
@@ -387,6 +387,37 @@ it("read", () => {
   reset();
 });
 
+it("write", () => {
+  let buf = Buffer.alloc(16);
+  function reset() {
+    new Uint8Array(buf.buffer).fill(0);
+  }
+
+  expect(buf.write("hello", 8, 8)).toBe(5);
+  reset();
+
+  expect(buf.write("hello!", 3, 8)).toBe(6);
+  reset();
+
+  expect(buf.write("Foo Bar!", 4, 4)).toBe(4);
+  reset();
+
+  expect(buf.write("foo", 0, 1)).toBe(1);
+  reset();
+
+  expect(buf.write("foo", 0, 2)).toBe(2);
+  reset();
+
+  expect(buf.write("foo", 0)).toBe(3);
+  reset();
+
+  expect(buf.write("Foo Bar!", 4, 6)).toBe(6);
+  reset();
+
+  expect(buf.write("Foo Bar!", 4, 7)).toBe(7);
+  reset();
+});
+
 it("includes", () => {
   const buf = Buffer.from('this is a buffer');