test/nbt_read_write_helpers: fix unit tests for readString()

src/lib/nbt.cpp

@@ -154,6 +154,9 @@ namespace NBT {
             if (stringSize.isError) {
                 return ErrorOr<tiny_utf8::string>(true, stringSize.errorCode);
             }
+            if (currentPosition + (uint64_t) stringSize.value + 2 > dataSize) {
+                return ErrorOr<tiny_utf8::string>(true, ErrorCodes::OVERRUN);
+            }
 
             ErrorOr<tiny_utf8::string> output = JavaCompat::importJavaString(data+currentPosition, stringSize.value);
             if(output.isError){

src/test/javacompat.cpp

@@ -75,7 +75,16 @@ int main(){
 
     tiny_utf8::string normalString = tiny_utf8::string(normalStdString);
 
+    // check for normal operation
     ASSERT(normalString == importedString);
+
+    // check for mismatched size error
+    std::string javaStdStringCopy = javaStdString;
+    javaStdStringCopy[0]='b';
+    ErrorOr<tiny_utf8::string> errorString = JavaCompat::importJavaString(reinterpret_cast<uint8_t*>(javaStdStringCopy.data()), 0x75);
+    ASSERT(errorString.isError);
+    ASSERT(errorString.errorCode == ErrorCodes::MISMATCHEDSIZE);
+
     std::cout << "Passed Import Java string test." << std::endl;
 
     //using normalString from when we read the file earlier
@@ -91,5 +100,5 @@ int main(){
     std::cout << "Passed Export Java string test." << std::endl;
     delete nextChar;
 
-return 0;
+    return 0;
 }

src/test/nbt_read_write_helpers.cpp

@@ -490,9 +490,10 @@ int main(){
 
     tiny_utf8::string normalString = tiny_utf8::string(normalStdString);
 
-    ASSERT(normalString == NBT::helper::readString(reinterpret_cast<uint8_t*>(javaStdString.data()), 0x75, 0).value)
-    ASSERT(NBT::helper::readString(reinterpret_cast<uint8_t*>(javaStdString.data()), 0xFFFFF, 0).errorCode == ErrorCodes::OVERRUN);
-    ASSERT(NBT::helper::readString(reinterpret_cast<uint8_t*>(javaStdString.data()), 0xF, 0).errorCode == ErrorCodes::MISMATCHEDSIZE);
+    ASSERT(normalString == NBT::helper::readString(reinterpret_cast<uint8_t*>(javaStdString.data()), javaStdString.size(), 0).value)
+
+    javaStdString[0] = '1';
+    ASSERT(NBT::helper::readString(reinterpret_cast<uint8_t*>(javaStdString.data()), javaStdString.size(), 0).errorCode == ErrorCodes::OVERRUN);
     std::cout << "Passed readString NBT helper test." << std::endl;
     delete nextChar;