Hi Andrew, Thanks for your comments and interesting feedback. The ideas in this spec are certainly open to debate and input from everyone. As we well know, modularity is a great goal which has many merits...testability, ease of development, plug and play etc. However it is less easy to achieve in a pure form...some degree of pollution creeps into an implementation when one tries to optimize on other goals like performance, footprint etc. I was hoping that we could see this submission as a strawman for how one could potentially modularize VM development. With input from knowledgeable people in the community, maybe a standard for modular VM development can evolve out of this...
For context, this proposal sees the accessor( platform and VM ) mechanism as a tool to facilitate Classlibrary development in Java( as you obeserved below ). They are a set of singleton classes that class libraries instantiate securely through a factory mechanism. Their implementation is provided by the VM. Their default fully portable implementation could be via JNI, however there is potential for performance optimization...eg., once instantiated, the per invocation security could be relaxed, the JIT could recognize and aggressively inline them, etc. I have tried to answer some more of your questions inline....
I wonder who has the responsibility to provide such native-related and platform-independent interfaces to java classlib programmer? ...Then shall classlib programmer write native code to implement high-level
functions such as
"findFirstDiff" and invoke them via JNI mode? or shall VM provide such high-level functions and classlib programmer only need call mem.findFirst?
These are VM components. The idea is that the VM provides them and the Classlib programmer writes less native code.
As my understanding of the document, classlib programmer will avoid writing native code directly, and invoke corresponding interfaces defined in VM.
That is correct
If I'm right, I think it's very hard for VM to provide so many
native-related
APIs for classlib programmer. For example, java.net.Socket implementation.
Classlib >programmer still has to write native code to implement Socket function. And I also think it's
classlib programmer's responsibility
The idea is that the VM provides some standardized functionality through VM and Platform accessors. How much that is, is part of the standard definition that we need. I am not completely sure what you mean by the "classlib programmer's responsibility". It is true that the classlib programmer will need to implement whatever is not provided by the standardised accessor components. Thanks, Rana On 5/12/06, Andrew Zhang <[EMAIL PROTECTED]> wrote:
Hello, Rana I took a quick view on the document, and I have some questions on Chapter 6. Let's take 6.9.1 "A.NM ACCESS TO NATIVE MEMORY" as example: <cite>The MemoryAccessor interface includes the following function groups: 1.Memory allocation and de-allocation: malloc, realloc, free 2.Operations over primitive types: getByte, getDouble,setBoolean 3.Operations over arrays of primitive types: getChar(char[] buf,..) 4.Search operations: findFirstDiff, findFirstDiffReorder</cite> For full description, please refer to " http://issues.apache.org/jira/browse/HARMONY-459"; or [1]. I wonder who has the responsibility to provide such native-related and platform-independent interfaces to java classlib programmer? No doubt "OS Portability Layer" provides platform-independent interfaces, e.g, portable_malloc or portable_free. Then shall classlib programmer write native code to implement high-level functions such as "findFirstDiff" and invoke them via JNI mode? or shall VM provide such high-level functions and classlib programmer only need call mem.findFirst? I think Harmony classlib follows the former way currently. As my understanding of the document, classlib programmer will avoid writing native code directly, and invoke corresponding interfaces defined in VM. If I'm right, I think it's very hard for VM to provide so many native-related APIs for classlib programmer. For example, java.net.Socket implementation. Classlib programmer still has to write native code to implement Socket function. And I also think it's classlib programmer's responsibility. I don't know whether OPEN spec would plan to provide such interfaces? IMO, ByteBuffer example and Socket example is on the same level programming, and the real implemenation native code should exist on the same level code repository, e.g, both in VM or classlib native-src. Am I missing something? Would anyone clarify my confusion? Thanks a lot! [1] The java.nio package defines the buffer classes, which are used throughout the native input and output (NIO) APIs. Buffers can be *direct* or * non-direct*. Given a direct buffer, the system performs native I/O operations directly without copying the buffer content from the native to the Java* <file:///F:/clear/opendoc/HLD.html#* > layer, Java*<file:///F:/clear/opendoc/HLD.html#*>arrays. A direct byte buffer is created by using the allocateDirect() factory method, which is often mapped directly to the system or the C library allocation methods, such as malloc() and VirtualAlloc(). Direct access is provided by using native methods, which increases the overall cost of accessing such data from the Java*< file:///F:/clear/opendoc/HLD.html#*>layer. The memory accessor mechanism encapsulates all required operations on the native heap, and provides room for future optimizations by using in-lining or other JIT techniques. The MemoryAccessor interface includes the following function groups: - Memory allocation and de-allocation: malloc, realloc, free - Operations over primitive types: getByte, getDouble,setBoolean - Operations over arrays of primitive types: getChar(char[] buf,..) - Search operations: findFirstDiff, findFirstDiffReorder On 5/13/06, Rana Dasgupta <[EMAIL PROTECTED]> wrote: > > Hi, > Alongside the DRLVM codebase, here is a contribution from Intel of an OPEN > ( Open Pluggable Extensible Interface ) specification for JVM and > Classlibrary-VM Interface development. > > URL: http://issues.apache.org/jira/browse/HARMONY-459 > > > We hope that this spec will promote modular component oriented development > of core pieces eg., the garbage collector, core VM, Just In Time compiler, > ClassLibrary-VM Interface etc. That it will provide a framework for > developing and interconnecting alternate component implementations through > standardized interfaces. > The DRLVM codebase does not quite confirm to the OPEN spec at this point, > though that is the final intent. The OPEN specification is also an idea, > and > by no means complete. We need the community's help in giving the final > form > to this specification, defining the header files that map to the > specification, and then in taking the Harmony implementation forward to be > OPEN compatible. > > Thanks, > Rana Dasgupta > Intel Middleware Development > > -- Andrew Zhang China Software Development Lab, IBM
