Great Paulex, +1. I agree that mmap family methods should be encapsulated in portlib.
Thanks! On 7/26/06, Paulex Yang <[EMAIL PROTECTED]> wrote:
Hi, all I raise HARMONY-982 (https://issues.apache.org/jira/browse/HARMONY-982) about the portlib extension on mmap. And here goes my proposal about the extension, comments are welcome. Currently portlib has some mmap support, but the support is limited in several ways: 1. it only mmap in private(copy_on_write) mode 2. it always mmap whole file 3. it only accepts filename, but nio needs to map a already opened file descriptor so that the Harmony's mmap is implemented in platform dependent codes so far, I think these are good candidates as the portlib extension. To support the nio's requirement, three current mmap functions need to be enhanced - hymmap_map_file, hymmap_unmap_file and hymmap_capabilities, one new method is added: hymmap_msync. Please see details below: 1. hymmap_map_file /** * Map a part of file into memory. * * @param [in] portLibrary The port library * @param [in] file The file descriptor/handle of the already open file to be mapped * @param [in] offset The file offset of the part to be mapped * @param [in] size The number of bytes to be mapped, if zero, the whole file is mapped * @param [in] mappingName The name of the file mapping object to be created/opened. * If a named object is not required, this parameter can be specified as NULL * @param [in] flags Flags relating to the mapping: * @args HYPORT_MMAP_FLAG_READ read only map * @args HYPORT_MMAP_FLAG_WRITE read/write map * @args HYPORT_MMAP_FLAG_COPYONWRITE copy on write map * @args HYPORT_MMAP_FLAG_SHARED share memory mapping with other processes * @args HYPORT_MMAP_FLAG_PRIVATE private memory mapping, do not share with other processes (implied by HYPORT_MMAP_FLAG_COPYONWRITE) * * @return A pointer to the start of the mapped file or NULL is an error has occurred */ void *hymmap_map_file(HYPortLibrary portLibrary, IDATA file, U_64 offset, UDATA size, const char *mappingName, U_32 flags) This will use CreateFileMapping() and MapViewOfFile() on Windows and mmap() on Unix to map the file into the process' address space. In both cases, it will return the address to which the file has been mapped. The memory mapping API's on all platforms require an open handle/file descriptor to the file to be mapped. The mapAddress parameter has been removed from the original signature. This was an output parameter from the API containing the address at which the file has been mapped. However, this is the return value of the function and was therefore duplication. 2. hymmap_msync /** * Synchronise updates to memory mapped file region with file on disk. The call may wait for the file write * to complete or this may be scheduled for a later time and the function return immediately, depending on * the flags setting * * @param [in] portLibrary The port library * @param [in] start Pointer to the start of the memory mapped area to be synchronised * @param [in] length Length of the memory mapped area to be synchronised * @param [in] flags Flags controlling the behaviour of the function: * @args HYPORT_MMAP_SYNC_WAIT Synchronous update required, function will not * return until file updated. Note that to achieve this on Windows requires the * file to be opened with the FILE_FLAG_WRITE_THROUGH flag * @args HYPORT_MMAP_SYNC_ASYNC Asynchronous update required, function returns * immediately, file will be updated later * @args HYPORT_MMAP_SYNC_INVALIDATE Requests that other mappings of the same * file be invalidated, so that they can be updated with the values just written * * @return 0 on success, -1 on failure. Errors will be reported using the usual port library mechanism */ IDATA hymmap_msync(HYPortLibrary portLibrary, void *start, UDATA length, U_32 flags) This function will use msync on Unix and FlushViewOfFile on Windows. 3. hymmap_unmap_file /** * Unmap previously mapped memory * * @param [in] portLibrary The port library * @param [in] start Pointer to the start of the memory mapped area * @param [in] size The length of the mapped area */ void hymmap_unmap_file(HYPortLibrary portLibrary, void *start, UDATA size) This existing API will be changed to take the start address returned from hymmap_map_file and the size of the mapped area instead of the current handle. The handle is not very clear as it is the start address of the mapped area (equivalent to start) on Windows and a pointer to a structure containing this and the size on Unix platforms. Explicitly passing the start address and length will provide a clearer interface. 4. hymmap_capabilities /** * Check the capabilities available for HYMMAP at runtime for the current platform * * @param [in] portLibrary The port library * * @return The capabilities available on this platform * @args HYPORT_MMAP_CAPABILITY_READ * @args HYPORT_MMAP_CAPABILITY_WRITE * @args HYPORT_MMAP_CAPABILITY_COPYONWRITE */ I_32 hymmap_capabilities(HYPortLibrary portLibrary) -- Paulex Yang China Software Development Lab IBM --------------------------------------------------------------------- Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
-- Andrew Zhang China Software Development Lab, IBM
