Avoid trusting the length encoded in the Snapshot if there is an

runtime/vm/snapshot_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_debugger_api.h"
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_api_message.h"
@@ skipping 35 matching lines @@
 }
 
 
 static uint8_t* zone_allocator(
     uint8_t* ptr, intptr_t old_size, intptr_t new_size) {
   Zone* zone = Isolate::Current()->current_zone();
   return zone->Realloc<uint8_t>(ptr, old_size, new_size);
 }
 
 
-static Dart_CObject* DecodeMessage(uint8_t* message,
-                                   intptr_t length,
-                                   ReAlloc allocator) {
-  ApiMessageReader message_reader(message, length, allocator);
-  return message_reader.ReadMessage();
-}
-
-
 // Compare two Dart_CObject object graphs rooted in first and
 // second. The second graph will be destroyed by this operation no matter
 // whether the graphs are equal or not.
 static void CompareDartCObjects(Dart_CObject* first, Dart_CObject* second) {
   // Return immediately if entering a cycle.
   if (second->type == Dart_CObject::kNumberOfTypes) return;
 
   EXPECT_NE(first, second);
   EXPECT_EQ(first->type, second->type);
   switch (first->type) {
@@ skipping 39 matching lines @@
     default:
       EXPECT(false);
   }
 }
 
 
 static void CheckEncodeDecodeMessage(Dart_CObject* root) {
   // Encode and decode the message.
   uint8_t* buffer = NULL;
   ApiMessageWriter writer(&buffer, &malloc_allocator);
-  writer.WriteCMessage(root);
+  intptr_t buffer_len = writer.WriteCMessage(root);
 
-  Dart_CObject* new_root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                         writer.BytesWritten(),
-                                         &zone_allocator);
+  // Create a snapshot object using the buffer.
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
+
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* new_root = api_reader.ReadMessage();
 
   // Check that the two messages are the same.
   CompareDartCObjects(root, new_root);
 }
 
 TEST_CASE(SerializeNull) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Object& null_object = Object::Handle();
   writer.WriteObject(null_object.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   const Object& serialized_object = Object::Handle(reader.ReadObject());
   EXPECT(Equals(null_object, serialized_object));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_NOTNULL(root);
   EXPECT_EQ(Dart_CObject::kNull, root->type);
   CheckEncodeDecodeMessage(root);
 }
 
 
 TEST_CASE(SerializeSmi1) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Smi& smi = Smi::Handle(Smi::New(124));
   writer.WriteObject(smi.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   const Object& serialized_object = Object::Handle(reader.ReadObject());
   EXPECT(Equals(smi, serialized_object));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_NOTNULL(root);
   EXPECT_EQ(Dart_CObject::kInt32, root->type);
   EXPECT_EQ(smi.Value(), root->value.as_int32);
   CheckEncodeDecodeMessage(root);
 }
 
 
 TEST_CASE(SerializeSmi2) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Smi& smi = Smi::Handle(Smi::New(-1));
   writer.WriteObject(smi.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   const Object& serialized_object = Object::Handle(reader.ReadObject());
   EXPECT(Equals(smi, serialized_object));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_NOTNULL(root);
   EXPECT_EQ(Dart_CObject::kInt32, root->type);
   EXPECT_EQ(smi.Value(), root->value.as_int32);
   CheckEncodeDecodeMessage(root);
 }
 
 
 Dart_CObject* SerializeAndDeserializeMint(const Mint& mint) {
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   writer.WriteObject(mint.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   const Object& serialized_object = Object::Handle(reader.ReadObject());
   EXPECT(serialized_object.IsMint());
 
   // Read object back from the snapshot into a C structure.
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_NOTNULL(root);
   CheckEncodeDecodeMessage(root);
   return root;
 }
 
 
 void CheckMint(int64_t value) {
   Zone zone(Isolate::Current());
 
   const Mint& mint = Mint::Handle(Mint::New(value));
@@ skipping 39 matching lines @@
 
 
 TEST_CASE(SerializeDouble) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Double& dbl = Double::Handle(Double::New(101.29));
   writer.WriteObject(dbl.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   const Object& serialized_object = Object::Handle(reader.ReadObject());
   EXPECT(Equals(dbl, serialized_object));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_NOTNULL(root);
   EXPECT_EQ(Dart_CObject::kDouble, root->type);
   EXPECT_EQ(dbl.value(), root->value.as_double);
   CheckEncodeDecodeMessage(root);
 }
 
 
 TEST_CASE(SerializeBool) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Bool& bool1 = Bool::Handle(Bool::True());
   const Bool& bool2 = Bool::Handle(Bool::False());
   writer.WriteObject(bool1.raw());
   writer.WriteObject(bool2.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   EXPECT(Bool::True() == reader.ReadObject());
   EXPECT(Bool::False() == reader.ReadObject());
 }
 
 
 TEST_CASE(SerializeTrue) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with true object.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Bool& bl = Bool::Handle(Bool::True());
   writer.WriteObject(bl.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_NOTNULL(root);
   EXPECT_EQ(Dart_CObject::kBool, root->type);
   EXPECT_EQ(true, root->value.as_bool);
   CheckEncodeDecodeMessage(root);
 }
 
 
 TEST_CASE(SerializeFalse) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with false object.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Bool& bl = Bool::Handle(Bool::False());
   writer.WriteObject(bl.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_NOTNULL(root);
   EXPECT_EQ(Dart_CObject::kBool, root->type);
   EXPECT_EQ(false, root->value.as_bool);
   CheckEncodeDecodeMessage(root);
 }
 
 
 static uword allocator(intptr_t size) {
   return reinterpret_cast<uword>(malloc(size));
 }
 
 
 TEST_CASE(SerializeBigint) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Bigint& bigint = Bigint::Handle(Bigint::New(DART_INT64_C(0xfffffffff)));
   writer.WriteObject(bigint.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   Bigint& obj = Bigint::Handle();
   obj ^= reader.ReadObject();
 
   EXPECT_EQ(BigintOperations::ToMint(bigint), BigintOperations::ToMint(obj));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   // Bigint not supported.
   EXPECT_NOTNULL(root);
   EXPECT_EQ(Dart_CObject::kBigint, root->type);
   EXPECT_STREQ("FFFFFFFFF", root->value.as_bigint);
   CheckEncodeDecodeMessage(root);
 }
 
 
 Dart_CObject* SerializeAndDeserializeBigint(const Bigint& bigint) {
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   writer.WriteObject(bigint.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   Bigint& serialized_bigint = Bigint::Handle();
   serialized_bigint ^= reader.ReadObject();
   const char *str1 = BigintOperations::ToHexCString(bigint, allocator);
   const char *str2 =
       BigintOperations::ToHexCString(serialized_bigint, allocator);
   EXPECT_STREQ(str1, str2);
   free(const_cast<char*>(str1));
   free(const_cast<char*>(str2));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   // Bigint not supported.
   EXPECT_NOTNULL(root);
   CheckEncodeDecodeMessage(root);
   return root;
 }
 
 
 void CheckBigint(const char* bigint_value) {
   Zone zone(Isolate::Current());
 
@@ skipping 36 matching lines @@
   writer.WriteObject(Object::field_class());
   writer.WriteObject(Object::token_stream_class());
   writer.WriteObject(Object::script_class());
   writer.WriteObject(Object::library_class());
   writer.WriteObject(Object::code_class());
   writer.WriteObject(Object::instructions_class());
   writer.WriteObject(Object::pc_descriptors_class());
   writer.WriteObject(Object::exception_handlers_class());
   writer.WriteObject(Object::context_class());
   writer.WriteObject(Object::context_scope_class());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   EXPECT(Object::class_class() == reader.ReadObject());
   EXPECT(Object::null_class() == reader.ReadObject());
   EXPECT(Object::type_class() == reader.ReadObject());
   EXPECT(Object::type_parameter_class() == reader.ReadObject());
   EXPECT(Object::type_arguments_class() == reader.ReadObject());
   EXPECT(Object::instantiated_type_arguments_class() == reader.ReadObject());
   EXPECT(Object::function_class() == reader.ReadObject());
@@ skipping 14 matching lines @@
 
 TEST_CASE(SerializeString) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   static const char* cstr = "This string shall be serialized";
   String& str = String::Handle(String::New(cstr));
   writer.WriteObject(str.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   String& serialized_str = String::Handle();
   serialized_str ^= reader.ReadObject();
   EXPECT(str.Equals(serialized_str));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_EQ(Dart_CObject::kString, root->type);
   EXPECT_STREQ(cstr, root->value.as_string);
   CheckEncodeDecodeMessage(root);
 }
 
 
 TEST_CASE(SerializeArray) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const int kArrayLength = 10;
   Array& array = Array::Handle(Array::New(kArrayLength));
   Smi& smi = Smi::Handle();
   for (int i = 0; i < kArrayLength; i++) {
     smi ^= Smi::New(i);
     array.SetAt(i, smi);
   }
   writer.WriteObject(array.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   Array& serialized_array = Array::Handle();
   serialized_array ^= reader.ReadObject();
   EXPECT(array.Equals(serialized_array));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_EQ(Dart_CObject::kArray, root->type);
   EXPECT_EQ(kArrayLength, root->value.as_array.length);
   for (int i = 0; i < kArrayLength; i++) {
     Dart_CObject* element = root->value.as_array.values[i];
     EXPECT_EQ(Dart_CObject::kInt32, element->type);
     EXPECT_EQ(i, element->value.as_int32);
   }
   CheckEncodeDecodeMessage(root);
 }
 
 
 TEST_CASE(SerializeEmptyArray) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const int kArrayLength = 0;
   Array& array = Array::Handle(Array::New(kArrayLength));
   writer.WriteObject(array.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   Array& serialized_array = Array::Handle();
   serialized_array ^= reader.ReadObject();
   EXPECT(array.Equals(serialized_array));
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_EQ(Dart_CObject::kArray, root->type);
   EXPECT_EQ(kArrayLength, root->value.as_array.length);
   EXPECT(root->value.as_array.values == NULL);
   CheckEncodeDecodeMessage(root);
 }
 
 
 TEST_CASE(SerializeByteArray) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const int kByteArrayLength = 256;
   Uint8Array& byte_array =
       Uint8Array::Handle(Uint8Array::New(kByteArrayLength));
   for (int i = 0; i < kByteArrayLength; i++) {
     byte_array.SetAt(i, i);
   }
   writer.WriteObject(byte_array.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   ByteArray& serialized_byte_array = ByteArray::Handle();
   serialized_byte_array ^= reader.ReadObject();
   EXPECT(serialized_byte_array.IsByteArray());
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_EQ(Dart_CObject::kUint8Array, root->type);
   EXPECT_EQ(kByteArrayLength, root->value.as_byte_array.length);
   for (int i = 0; i < kByteArrayLength; i++) {
     EXPECT(root->value.as_byte_array.values[i] == i);
   }
   CheckEncodeDecodeMessage(root);
 }
 
 
 TEST_CASE(SerializeEmptyByteArray) {
   Zone zone(Isolate::Current());
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const int kByteArrayLength = 0;
   Uint8Array& byte_array =
       Uint8Array::Handle(Uint8Array::New(kByteArrayLength));
   writer.WriteObject(byte_array.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   ByteArray& serialized_byte_array = ByteArray::Handle();
   serialized_byte_array ^= reader.ReadObject();
   EXPECT(serialized_byte_array.IsByteArray());
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_EQ(Dart_CObject::kUint8Array, root->type);
   EXPECT_EQ(kByteArrayLength, root->value.as_byte_array.length);
   EXPECT(root->value.as_byte_array.values == NULL);
   CheckEncodeDecodeMessage(root);
 }
 
 
+TEST_CASE(IllegalSnapshot_LengthMismatch) {
+  Zone zone(Isolate::Current());
+
+  // Write snapshot with object content.
+  uint8_t* buffer;
+  SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
+  const Object& null_object = Object::Handle();
+  writer.WriteObject(null_object.raw());
+  intptr_t buffer_len = writer.FinalizeBuffer();
+
+  // Create a snapshot object using the wrong buffer length.
+  const Snapshot* snapshot =
+      Snapshot::SetupFromBuffer(buffer, buffer_len + sizeof(int32_t));
+  EXPECT(snapshot == NULL);
+
+  snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
+}
+
+
+TEST_CASE(IllegalSnapshot_TooShort) {
+  Zone zone(Isolate::Current());
+
+  // Write snapshot with object content.
+  uint8_t* buffer;
+  SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
+  const Object& null_object = Object::Handle();
+  writer.WriteObject(null_object.raw());
+  writer.FinalizeBuffer();
+
+  // Give the message an illegal size.
+  intptr_t snapshot_address = reinterpret_cast<intptr_t>(buffer);
+  intptr_t length_address = snapshot_address + Snapshot::length_offset();
+  int32_t* len_ptr = reinterpret_cast<int32_t*>(length_address);
+  *len_ptr = sizeof(int32_t);
+
+  // Check that SetupFromBuffer returns NULL because the buffer length
+  // is too short to possibly be valid.
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, sizeof(int32_t));
+  EXPECT(snapshot == NULL);
+}
+
+
 TEST_CASE(SerializeScript) {
   const char* kScriptChars =
       "class A {\n"
       "  static bar() { return 42; }\n"
       "  static fly() { return 5; }\n"
       "  static s1() { return 'this is a string in the source'; }\n"
       "  static s2() { return 'this is a \"string\" in the source'; }\n"
       "  static s3() { return 'this is a \\\'string\\\' in \"the\" source'; }\n"
       "  static s4() { return 'this \"is\" a \"string\" in \"the\" source'; }\n"
       "}\n";
 
   String& url = String::Handle(String::New("dart-test:SerializeScript"));
   String& source = String::Handle(String::New(kScriptChars));
   Script& script = Script::Handle(Script::New(url,
                                               source,
                                               RawScript::kSourceTag));
   const String& lib_url = String::Handle(Symbols::New("TestLib"));
   Library& lib = Library::Handle(Library::New(lib_url));
   lib.Register();
   EXPECT(CompilerTest::TestCompileScript(lib, script));
 
   // Write snapshot with object content.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kScript, &buffer, &malloc_allocator);
   writer.WriteObject(script.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
 
   // Create a snapshot object using the buffer.
-  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   Script& serialized_script = Script::Handle();
   serialized_script ^= reader.ReadObject();
 
   // Check if the serialized script object matches the original script.
   String& expected_literal = String::Handle();
   String& actual_literal = String::Handle();
   String& str = String::Handle();
@@ skipping 296 matching lines @@
 
 
 TEST_CASE(IntArrayMessage) {
   Zone zone(Isolate::Current());
   uint8_t* buffer = NULL;
   ApiMessageWriter writer(&buffer, &zone_allocator);
 
   static const int kArrayLength = 2;
   intptr_t data[kArrayLength] = {1, 2};
   int len = kArrayLength;
-  writer.WriteMessage(len, data);
+  intptr_t buffer_len = writer.WriteMessage(len, data);
+
+  // Create a snapshot object using the buffer.
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot into a C structure.
   ApiNativeScope scope;
-  Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                     writer.BytesWritten(),
-                                     &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  Dart_CObject* root = api_reader.ReadMessage();
   EXPECT_EQ(Dart_CObject::kArray, root->type);
   EXPECT_EQ(kArrayLength, root->value.as_array.length);
   for (int i = 0; i < kArrayLength; i++) {
     Dart_CObject* element = root->value.as_array.values[i];
     EXPECT_EQ(Dart_CObject::kInt32, element->type);
     EXPECT_EQ(i + 1, element->value.as_int32);
   }
   CheckEncodeDecodeMessage(root);
 }
 
 
 // Helper function to call a top level Dart function, serialize the
 // result and deserialize the result into a Dart_CObject structure.
 static Dart_CObject* GetDeserializedDartMessage(Dart_Handle lib,
                                                 const char* dart_function) {
   Dart_Handle result;
   result = Dart_Invoke(lib, Dart_NewString(dart_function), 0, NULL);
   EXPECT_VALID(result);
 
   // Serialize the list into a message.
   uint8_t* buffer;
   SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
   const Object& list = Object::Handle(Api::UnwrapHandle(result));
   writer.WriteObject(list.raw());
-  writer.FinalizeBuffer();
+  intptr_t buffer_len = writer.FinalizeBuffer();
+
+  // Create a snapshot object using the buffer.
+  const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+  EXPECT_NOTNULL(snapshot);
 
   // Read object back from the snapshot into a C structure.
-  return DecodeMessage(buffer + Snapshot::kHeaderSize,
-                       writer.BytesWritten(),
-                       &zone_allocator);
+  ApiMessageReader api_reader(snapshot, &zone_allocator);
+  return api_reader.ReadMessage();
 }
 
 
 UNIT_TEST_CASE(DartGeneratedMessages) {
   static const char* kCustomIsolateScriptChars =
       "getSmi() {\n"
       "  return 42;\n"
       "}\n"
       "getBigint() {\n"
       "  return -0x424242424242424242424242424242424242;\n"
@@ skipping 27 matching lines @@
   {
     DARTSCOPE_NOCHECKS(isolate);
 
     {
       Zone zone(Isolate::Current());
       uint8_t* buffer;
       SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
       Smi& smi = Smi::Handle();
       smi ^= Api::UnwrapHandle(smi_result);
       writer.WriteObject(smi.raw());
-      writer.FinalizeBuffer();
+      intptr_t buffer_len = writer.FinalizeBuffer();
+
+      // Create a snapshot object using the buffer.
+      const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+      EXPECT_NOTNULL(snapshot);
 
       // Read object back from the snapshot into a C structure.
       ApiNativeScope scope;
-      Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                         writer.BytesWritten(),
-                                         &zone_allocator);
+      ApiMessageReader api_reader(snapshot, &zone_allocator);
+      Dart_CObject* root = api_reader.ReadMessage();
       EXPECT_NOTNULL(root);
       EXPECT_EQ(Dart_CObject::kInt32, root->type);
       EXPECT_EQ(42, root->value.as_int32);
       CheckEncodeDecodeMessage(root);
     }
     {
       Zone zone(Isolate::Current());
       uint8_t* buffer;
       SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
       Bigint& bigint = Bigint::Handle();
       bigint ^= Api::UnwrapHandle(bigint_result);
       writer.WriteObject(bigint.raw());
-      writer.FinalizeBuffer();
+      intptr_t buffer_len = writer.FinalizeBuffer();
+
+      // Create a snapshot object using the buffer.
+      const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+      EXPECT_NOTNULL(snapshot);
 
       // Read object back from the snapshot into a C structure.
       ApiNativeScope scope;
-      Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                         writer.BytesWritten(),
-                                         &zone_allocator);
+      ApiMessageReader api_reader(snapshot, &zone_allocator);
+      Dart_CObject* root = api_reader.ReadMessage();
       EXPECT_NOTNULL(root);
       EXPECT_EQ(Dart_CObject::kBigint, root->type);
       EXPECT_STREQ("-424242424242424242424242424242424242",
                    root->value.as_bigint);
       CheckEncodeDecodeMessage(root);
     }
     {
       Zone zone(Isolate::Current());
       uint8_t* buffer;
       SnapshotWriter writer(Snapshot::kMessage, &buffer, &zone_allocator);
       String& str = String::Handle();
       str ^= Api::UnwrapHandle(string_result);
       writer.WriteObject(str.raw());
-      writer.FinalizeBuffer();
+      intptr_t buffer_len = writer.FinalizeBuffer();
+
+      // Create a snapshot object using the buffer.
+      const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer, buffer_len);
+      EXPECT_NOTNULL(snapshot);
 
       // Read object back from the snapshot into a C structure.
       ApiNativeScope scope;
-      Dart_CObject* root = DecodeMessage(buffer + Snapshot::kHeaderSize,
-                                         writer.BytesWritten(),
-                                         &zone_allocator);
+      ApiMessageReader api_reader(snapshot, &zone_allocator);
+      Dart_CObject* root = api_reader.ReadMessage();
       EXPECT_NOTNULL(root);
       EXPECT_EQ(Dart_CObject::kString, root->type);
       EXPECT_STREQ("Hello, world!", root->value.as_string);
       CheckEncodeDecodeMessage(root);
     }
   }
   Dart_ExitScope();
   Dart_ShutdownIsolate();
 }
 
@@ skipping 359 matching lines @@
   EXPECT(Dart_ErrorHasException(result));
   EXPECT_SUBSTRING("Exception: nulltruefalse1234563.14[]100123456789\n",
                    Dart_GetError(result));
 
   Dart_ExitScope();
 }
 
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64).
 
 }  // namespace dart