There is a common mangling scheme specified by JNI for C. The Bck2Brwsr projects mimics the specification as closely as possible and extends it only when the JVM compatibility differs from Java source compatibility and requires different treatment. The mangling is based on underscore encoding substitution.
Fully Qualified Names
Fully qualified name uses '_' to separate package names and class name. The global virtual machine object vm has methods to obtain all (once referenced) classes. One can get reference to String as:
var clazz = vm.java_lang_String(false);
- There is "__" after name of a method and before its arguments
- return type is encoded first, parameters follow
- If there is an '_' in the name or argument segment, it gets replaced by "_1"
- array signatures start with '[' - such character is replaced by "_3"
- object signatures end with ';' - that character is replaced by "_2"
As a result to call method String.substring(int, int) - e.g. a method that return string and takes two integers as arguments -it be written as:
var s = "..."; var r = s.substring__Ljava_lang_String_2II(0, 5);
When calling a static method, one first needs to obtain the name of a class. The class is made available in a global object called "vm". As such calling String.valueOf(10) is translated to:
var clazz = vm.java_lang_String(false); var r = clazz.valueOf__Ljava_lang_String_2I(10);
Accessing an Instance Field
To support subclasses defining the same field (like in case of InheritanceA and InheritanceB classes) the Bck2Brwsr needed to create accessor method to access each field in its declaring class. The accessor which prefixes the name of the field with "_" (forming a name that can't clash with mangled method names). The proper way to access field value defined in String class would then be:
var getValue = vm.java_lang_String(true)._value.call(this); var newValue = "..."; vm.java_lang_String(true)._value.call(this, newValue);
This can often be simplified to:
var getValue = this._value(); var newValue = "..."; this._value(newValue);
which does the same in most cases. Only when there is a subclass defining its own field value, the result would not be correct. Thus this kind of usage is appropriate when one knows the class is final and can't be subclassed (another reason to follow the ClientAPI advice).
Accessing a Static Field
Static fields are wrapped by accessors as well. However accessing them is simpler as they don't need proper this argument. One can use:
var getValue = vm.java_lang_String(true)._CASE_INSENSITIVE_ORDER(); var newValue = "..."; vm.java_lang_String(true)._CASE_INSENSITIVE_ORDER(newValue);
Possible Future Work
There is an experimental branch which replaces well known object types with a single letter:
- "Ljava_lang_String_2" would become 's'
- "Ljava_lang_Object_2" would become 'o'