[cp-patches] RFC : Instrumentation in the vm integration guide

[Nicolas Geoffray]

Hi,

Here's a small documentation on how to use the instrumentation
functionnality in gnu classpath generics for vm implementers.
I added at the end that default implementation might break the
ClassLoader/VMClassLoader interface.

2005-12-04  Nicolas Geoffray  <address@hidden>
              
               * doc/vmintegration.texinfo: Added subsection in the 
classpath
               hooks for the VMInstrumentationImpl class.

Index: doc/vmintegration.texinfo
===================================================================
RCS file: /cvsroot/classpath/classpath/doc/vmintegration.texinfo,v
retrieving revision 1.19
diff -u -r1.19 vmintegration.texinfo
--- doc/vmintegration.texinfo   15 Jul 2005 09:04:46 -0000      1.19
+++ doc/vmintegration.texinfo   4 Dec 2005 15:15:52 -0000
@@ -226,6 +226,7 @@
 * java.lang.VMRuntime::
 * java.lang.VMString::
 * java.lang.VMThread::
+* java.lang.VMInstrumentationImpl::
 @end menu
 
 @node java.lang.VMClass, java.lang.VMObject ,java.lang,java.lang
@@ -607,7 +608,7 @@
 A VM may implement this differently by implementing this method,
 which is @code{static} and the only one in @code{VMString}.
 
address@hidden java.lang.VMThread,, java.lang.VMString, java.lang
address@hidden java.lang.VMThread,java.lang.VMInstrumentationImpl, 
java.lang.VMString, java.lang
 @subsection @code{java.lang.VMThread}
 
 @code{VMThread} provides the link between Java's threads and the platform
@@ -681,7 +682,43 @@
 frames in the thread.  This depends on the deprecated method @code{suspend()}
 having returned true, and is thus deprecated as a result.
 @end itemize
address@hidden itemize
+
address@hidden java.lang.VMInstrumentationImpl,, java.lang.VMThread, java.lang
address@hidden @code{java.lang.VMInstrumentationImpl}
+
+The @code{java.lang.VMInstrumentationImpl} and
address@hidden provides an implementation of the
address@hidden interface. This interface is for java
+1.5 and is only in the generics branch.
+A @code{InstrumentationImpl} object should be given to any agent
+given in the command line (see the @code{java.lang.instrument} package
+documentation). A VM has to implement the static native methods of the
address@hidden class.
+
address@hidden @bullet
address@hidden @code{isRedefineClassesSupported()} -- Returns if the JVM 
supports
+class redefinition.
address@hidden @code{redefineClasses()} -- Gives a set of classes with new 
bytecodes.
+The VM must redefine the classes by reading the new bytecodes.
address@hidden @code{getAllLoadedClass()} -- Returns an array of all loaded 
classes.
address@hidden @code{getInitiatedClass()} -- Returns an array of all classes 
loaded
+by a specific class loader.
address@hidden @code{getObjectSize()} -- Gives the size of an object.
address@hidden itemize
+
+When agents are defined, the VM has to call transformers of the
address@hidden object each time a class is loaded, eg a call to
address@hidden The @code{InstrumentationImpl} class defines
+a method that has to be called before reading a class file in the VM.
+
address@hidden @bullet
address@hidden @code{callTransformers} -- Calls each transformer registered to
+the @code{InstrumentationImpl} object and returns a new bytecode file.
address@hidden itemize
+
+No default implementation is provided in gnu classpath for the
address@hidden method. A default implementation will perhaps
+be written, but it might break the @code{ClassLoader/VMClassLoader} interface.
 
 @node gnu.classpath, java.util, java.lang, Classpath Hooks
 @section @code{gnu.classpath}