File Copy
Note: These samples
do only work on Windows NT !
Sample 1
This single-threaded version shows how
to multiplex I/O to a number of files with a single thread.
This is the most efficient mechanism if you do
not need the asynchronous completion model that the dual-threaded version offers.
Only one thread and one I/O completion port is used. The file handles for the source and
destination file are both associated with the same port. The thread starts off by posting
a number of overlapped reads from the source file. It then waits on the I/O completion
port.
Whenever a read completes, it immediately turns it around into a write to the destination
file. Whenever a write completes, it immediately posts the next read from the source file.
Sample 2
Usage of Completion Ports
Intended to demonstrate how to complete I/O in a different thread
asynchronously than the I/O was started from. This is useful for people who want a
more powerful mechanism of asynchronous completion callbacks than Win32 provides (i.e. VMS
developers who are used to ASTs).
Two threads are used. The first thread posts overlapped reads from the source file. These
reads complete to an I/O completion port the second thread is waiting on. The second
thread sees the I/O completion and posts an overlapped write to the destination file. The
write completes to another I/O completion port that the first thread is waiting on. The
first thread sees the I/O completion and posts another overlapped read.
Sample 3
Usage of Fibers
This example implements a fiber based file copy operation. Note
that a number of different techiques exists for copying files programmatically; this
sample simply illustrates the fiber APIs.
This example makes use of a fiber data structure which is used to determine the behavior
and state of the fiber. One data structure exists for each fiber; the pointer to the data
structure is passed to the fiber at fiber creation time via the lpParameter fiber
parameter.
The executing thread in the process makes a call to ConvertThreadToFiber, which allows
fibers to be scheduled by the caller. This also allows the resultant fiber to be scheduled
by another fiber.
Next, two additional fibers are created, one fiber which performs read operations against
a specified file, and another fiber which performs the write operations against a
specified file.
The primary fiber then schedules the read fiber. After a succesful read, the read fiber
schedules the write fiber. After a succesful write
in the write fiber, the write fiber schedules the read fiber. When the read/write cycle
has completed, the primary fiber is scheduled, which results in the display of the
read/write status. If an error occurs during the read or write fibers, the primary fiber
is scheduled and status of the read/write is displayed.
The fibers, fiber data structures, and file handles are then freed prior to process
termination.
If you experience problems while compiling sample 3 try adding _WIN32_WINNT=0x0400 to the "defines" of your project settings. If you are developing for windows 2000 add _WIN32_WINNT=0x0500
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