Does the library support converting VMDK to raw disk image

[leslie-qiwa]

Thanks for the great library. We want a simple library to convert VMDK image to raw disk image. qemu-img can support it, but we do want a library like libvmdk to achieve. So if yes, can you please provide some sample codes? Is libvmdk_handle_read_buffer the one I should use and continuously read until EOF?

[joachimmetz]

Is libvmdk_handle_read_buffer the one I should use and continuously read until EOF?

yes, the API is very straightforward open (descriptor file), (open data files), read_buffer, close For an example have a look at vmdkmount (mount_file_entry.c).

[leslie-qiwa]

Perfect and thanks for the quick reply. Would you mind me submitting one PR to add one vmdkconvert utility tool into vmdktools folder. I thought other people may benefit from it, and I can also get your help to review it.

[joachimmetz]

The reason why I never added such a tool (which I would have named vmdkexport) is that with vmdkmount you technically have a raw image without the additional storage overhead. With dd or equiv you can easily create such a copy.

What is your use case for having such tool?

BTW I can help review such a tool also in another repo, as long as the code is under an Open Source license I can work with.

[leslie-qiwa]

The use case is to download vmdk file and convert to raw disk image file on the fly, while Golang is the main language. So I probably need write one Golang binding for this library. With the vmdkexport tool, I can get some understanding on the APIs and verify the result, then can work on binding part.

Anyway, let me create such a tool on my repo, and invite you for review. Thanks a lot

[joachimmetz]

I see, the outline of the C API usage would look something like:

1. libvmdk_error_t *error = NULL;
2. libvmdk_handle_t *handle = NULL;
3. libvmdk_handle_initialize(&handle, &error);
4. libvmdk_handle_open(handle, descriptor_file, LIBVMDK_OPEN_READ, &error);
5. libvmdk_handle_open_extent_data_files(handle, &error)
6. libvmdk_handle_read_buffer(handle, buffer, read_size, &error)
7. libvmdk_handle_close(handle, &error);
8. libvmdk_handle_free(&handle, &error);

Make sure to check the return values of the functions, they indicate success/error status and error contains some diagnostic information about the error. Also free error if it has been set.

More detail is about the C API are in man 3 libvmdk or the main include file include/libvmdk.h

[leslie-qiwa]

thanks a lot!