Winapi read from file

This function is designed for both synchronous and asynchronous operations. For a similar function designed solely for asynchronous operation, see ReadFileEx. A handle to the device for example, a file, file stream, physical disk, volume, console buffer, tape drive, socket, communications resource, mailslot, or pipe.

The hFile parameter must have been created with read access. This buffer must remain valid for the duration of the read operation. The caller must not use this buffer until the read operation is completed.

A pointer to the variable that receives the number of bytes read when using a synchronous hFile parameter. ReadFile sets this value to zero before doing any work or error checking. Use NULL for this parameter if this is an asynchronous operation to avoid potentially erroneous results. For an hFile that supports byte offsets, if you use this parameter you must specify a byte offset at which to start reading from the file or device.

For an hFile that does not support byte offsets, Offset and OffsetHigh are ignored. We also declare a char array to store the data read from the file temporarily. The call to the GetWindowText function returns the text key-in in the text boxes. Once we open the file content which we will copy, we store the handle in the hcopysource.

In the previous section, we stored a file handle for copy source. The same way we can store the destination file handle. Here it is expected that the file does not exist in the destination folder and we always try to create the file as a new file in the location specified.

Therefore, the tag always creates the file and gives back the handle. Once the call succeeded, we will get the read content in the buffer variable. When the file content is over bytes, we will read its content in batches by making use of the loop. This means in each batch, we will read or less That will be last read. Say, for example, the file has bytes of data, and the first read batch will read all bytes and next batch will read the remaining 5 bytes in the next iteration.

Then we display a message stating the content of the file copied to the target location. Below given video shows how the sample perform the file copy operation using the Win32 API Functions:.

Unpredictable results can occur if you fail to set the time-out values. For details see File Buffering. The remainder of the message can be read by a subsequent call to the ReadFile or PeekNamedPipe function. For more information about pipes, see Pipes.

For a code example that shows you how to test for end-of-file, see Testing for the End of a File. File Management Functions. Skip to main content. This browser is no longer supported.

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