rados: add support for retrieving the alignment (stripe size) for EC pools

Add support for getting the alignment (stripe size) in bytes for pools that require/support it.
Fixes #739

This commit adds two new API calls to IOContext, one to know if the pool requires alignment and
the second one to get the stripe size in bytes:

 RequiresAlignment() (bool, error)
 Alignment() (uint64, error)

Signed-off-by: Daniel M. Lambea <dmlambea@tenerife.es>

rados/ioctx_pool_alignment.go

@@ -0,0 +1,27 @@
+//go:build ceph_preview
+// +build ceph_preview
+
+package rados
+
+// #cgo LDFLAGS: -lrados
+// #include <rados/librados.h>
+// #include <stdlib.h>
+//
+import "C"
+
+// Alignment returns the required stripe size in bytes for pools supporting/requiring it, or an error if unsuccessful.
+// For an EC pool, a buffer size multiple of its stripe size is required to call Append. To know if the pool requires
+// alignment or not, use RequiresAlignment.
+//
+// Implements:
+//  int rados_ioctx_pool_required_alignment2(rados_ioctx_t io, uint64_t *alignment)
+func (ioctx *IOContext) Alignment() (uint64, error) {
+	var alignSizeBytes C.uint64_t
+	ret := C.rados_ioctx_pool_required_alignment2(
+		ioctx.ioctx,
+		&alignSizeBytes)
+	if ret != 0 {
+		return 0, getError(ret)
+	}
+	return uint64(alignSizeBytes), nil
+}

rados/ioctx_pool_alignment_test.go

@@ -0,0 +1,15 @@
+//go:build ceph_preview
+// +build ceph_preview
+
+package rados
+
+import (
+	"github.com/stretchr/testify/assert"
+)
+
+func (suite *RadosTestSuite) TestAlignment() {
+	suite.SetupConnection()
+
+	_, err := suite.ioctx.Alignment()
+	assert.NoError(suite.T(), err)
+}

rados/ioctx_pool_requires_alignment.go

@@ -0,0 +1,27 @@
+//go:build ceph_preview
+// +build ceph_preview
+
+package rados
+
+// #cgo LDFLAGS: -lrados
+// #include <rados/librados.h>
+// #include <stdlib.h>
+//
+import "C"
+
+// RequiresAlignment returns true if the pool supports/requires alignment or an error if not successful.
+// For an EC pool, a buffer size multiple of its stripe size is required to call Append. See
+// Alignment to know how to get the stripe size for pools requiring it.
+//
+// Implements:
+//  int rados_ioctx_pool_requires_alignment2(rados_ioctx_t io, int *req)
+func (ioctx *IOContext) RequiresAlignment() (bool, error) {
+	var alignRequired C.int
+	ret := C.rados_ioctx_pool_requires_alignment2(
+		ioctx.ioctx,
+		&alignRequired)
+	if ret != 0 {
+		return false, getError(ret)
+	}
+	return (alignRequired != 0), nil
+}

rados/ioctx_pool_requires_alignment_test.go

@@ -0,0 +1,15 @@
+//go:build ceph_preview
+// +build ceph_preview
+
+package rados
+
+import (
+	"github.com/stretchr/testify/assert"
+)
+
+func (suite *RadosTestSuite) TestRequiresAlignment() {
+	suite.SetupConnection()
+
+	_, err := suite.ioctx.RequiresAlignment()
+	assert.NoError(suite.T(), err)
+}