rados: create a new WriteOp type around rados_write_op_t

The WriteOp type will manage librados write operations and the
corresponding functions that ceph names like rados_write_op_*.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

rados/write_op.go

@@ -0,0 +1,91 @@
+package rados
+
+// #cgo LDFLAGS: -lrados
+// #include <errno.h>
+// #include <stdlib.h>
+// #include <rados/librados.h>
+//
+import "C"
+
+import (
+	"unsafe"
+
+	ts "github.com/ceph/go-ceph/internal/timespec"
+)
+
+// Timespec is a public type for the internal C 'struct timespec'
+type Timespec ts.Timespec
+
+// WriteOp manages a set of discrete actions that will be performed together
+// atomically.
+type WriteOp struct {
+	operation
+	op C.rados_write_op_t
+}
+
+// CreateWriteOp returns a newly constructed write operation.
+func CreateWriteOp() *WriteOp {
+	return &WriteOp{
+		op: C.rados_create_write_op(),
+	}
+}
+
+// Release the resources associated with this write operation.
+func (w *WriteOp) Release() {
+	C.rados_release_write_op(w.op)
+	w.op = nil
+	w.free()
+}
+
+func (w WriteOp) operate2(
+	ioctx *IOContext, oid string, mtime *Timespec, flags OperationFlags) error {
+
+	if err := ioctx.validate(); err != nil {
+		return err
+	}
+
+	cOid := C.CString(oid)
+	defer C.free(unsafe.Pointer(cOid))
+	var cMtime *C.struct_timespec
+	if mtime != nil {
+		cMtime = &C.struct_timespec{}
+		ts.CopyToCStruct(
+			ts.Timespec(*mtime),
+			ts.CTimespecPtr(cMtime))
+	}
+
+	ret := C.rados_write_op_operate2(
+		w.op, ioctx.ioctx, cOid, cMtime, C.int(flags))
+	return w.update(writeOp, ret)
+}
+
+// Operate will perform the operation(s).
+func (w *WriteOp) Operate(ioctx *IOContext, oid string, flags OperationFlags) error {
+	return w.operate2(ioctx, oid, nil, flags)
+}
+
+// OperateWithMtime will perform the operation while setting the modification
+// time stamp to the supplied value.
+func (w *WriteOp) OperateWithMtime(
+	ioctx *IOContext, oid string, mtime Timespec, flags OperationFlags) error {
+
+	return w.operate2(ioctx, oid, &mtime, flags)
+}
+
+func (w *WriteOp) operateCompat(ioctx *IOContext, oid string) error {
+	switch err := w.Operate(ioctx, oid, OperationNoFlag).(type) {
+	case nil:
+		return nil
+	case OperationError:
+		return err.OpError
+	default:
+		return err
+	}
+}
+
+// Create a rados object.
+func (w *WriteOp) Create(exclusive CreateOption) {
+	// category, the 3rd param, is deprecated and has no effect so we do not
+	// implement it in go-ceph
+	C.rados_write_op_create(w.op, C.int(exclusive), nil)
+}