[Libguestfs] Proposed new libguestfs file APIS

As part of a new virt-v2v feature, I've been thinking about how to write data to an arbitrary block device in the appliance. I need to be able to write arbitrary chunks of data to specific places on the device. This will need a new API, as guestfs_pread can't open a block device. While I'm at it, I'd like to create a new family of APIs which operate on a file handle: int guestfs_open_device(g, path); Open a block device. Return a handle. int guestfs_open_file(g, path); Open a file from the guest's filesystem. Return a handle. int guestfs_close_handle(g, handle); Close a file handle. ssize_t guestfs_hpread(g, handle, buf, size, offset); ssize_t guestfs_hread(g, handle, buf, size); ssize_t guestfs_hpwrite(g, handle, buf, size, offset); ssize_t guestfs_hwrite(g, handle, buf, size); Wrappers round pread(), read(), pwrite() and write() which operate on a handle. ssize_t guestfs_hseek(g, handle, offset, whence); Wrapper round lseek(). int guestfs_htruncate(g, handle, length); Wrapper round ftruncate(). In terms of the API, the handle would be an opaque int. In practise it would be a file descriptor owned by guestfsd. I believe these APIs could result in a performance improvement over opening a file repeated. However, I have no data to back this up at present. Aside from any potential performance improvement I believe these APIs are a better interface for the developer when doing low level file operations in the guest. Comments before I code this up? Thanks, Matt -- Matthew Booth, RHCA, RHCSS Red Hat Engineering, Virtualisation Team GPG ID: D33C3490 GPG FPR: 3733 612D 2D05 5458 8A8A 1600 3441 EA19 D33C 3490