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0N/Ajava_crw_demo Library
0N/AThe library java_crw_demo is a small C library that is used by HPROF
0N/Aand other agent libraries to do some very basic bytecode
0N/Ainsertion (BCI) of class files. This is not an agent
0N/Alibrary but a general purpose library that can be used to do some
0N/Avery limited bytecode insertion.
0N/Athe C function java_crw_demo(). The java_crw_demo library is provided
0N/AThe basic BCI that this library does includes:
0N/A * On any newarray type opcode, immediately following it, the array
0N/A object is duplicated on the stack and an invokestatic call to
0N/A * On entry to all methods, a invokestatic call to
0N/A two integers (cnum,mnum) to a method in a class, the cnum is the
0N/A number provided to the java_crw_demo library when the classfile was
0N/A * On return from any method (any return opcode), a invokestatic call to
0N/ASome methods are not modified at all, init methods and finalize methods
0N/Awhose length is 1 will not be modified. Classes that are designated
0N/A"system" will not have their clinit methods modified. In addition, the
0N/ANo methods or fields will be added to any class, however new constant
0N/Apool entries will be added at the end of the original constant pool table.
0N/AThe exception, line, and local variable tables for each method is adjusted
0N/Afor the modification. The bytecodes are compressed to use smaller offsets
0N/Aand the fewest 'wide' opcodes.
0N/AAll attempts are made to minimize the number of bytecodes at each insertion
0N/Asite, however, classes with N return opcodes or N newarray opcodes will get
0N/AN insertions. And only the necessary modification dictated by the input
0N/Aarguments to java_crw_demo are actually made.