We are change the the rpc call for WriteStream to not require the size
argument, opting to drive the process with io.Reader. The main issue was that
io.Reader may return io.EOF before reaching size, making the error handling
around this condition for callers more complex. To complement this, WriteStream
now returns the number of successfully written bytes.
The method no longer requires an io.ReadCloser, opting to require just an
io.Reader. This keeps the reader under the control of the caller, which
provides more flexibility.
This also begins to address some of the problems described in #791.
To support single-flight Size and ModTime queries against backend storage file,
we are replacing the CurrentSize call with a Stat call. A FileInfo interface is
provided for backends to provide a type, with a default implementation called
FileInfoInternal, for use by driver implementations.
More work needs to follow this change to update all the driver implementations.
This change brings the storagedriver API in line with the Go standard library's
use of int64 for offsets. The main benefit is simplicity in interfacing with
the io library reducing the number of type conversions in simple code.
The registry currently only accepts storage driver versions with the
same major version and an equal or lower minor version as its own
current storage driver api version, but this may be changed in the
future if we decide to implement specific version cross-compatibility.
Custom storage drivers can register a factory to create the driver by
name, similar to the database/sql package's Register and Open
factory.Create returns an in-process driver if registered or an IPC
driver if one can be found, erroring otherwise
This standardizes parameter passing for creation of storage drivers
Also adds documentation for storagedriver package and children
