rados: implement binding for read_op_omap_get_vals_by_keys

This commit implements binding for read_op_omap_get_vals_by_keys
RADOS Read operation.

Includes a unit test.

Signed-off-by: Robert Vasek <robert.vasek@cern.ch>

docs/api-status.json

@@ -976,6 +976,18 @@
         "comment": "Set an xattr.\n PREVIEW\n\nImplements:\n void rados_write_op_setxattr(rados_write_op_t write_op,\n                              const char * name,\n                              const char * value,\n                              size_t value_len)\n",
         "added_in_version": "v0.14.0",
         "expected_stable_version": "v0.16.0"
+      },
+      {
+        "name": "ReadOpOmapGetValsByKeysStep.Next",
+        "comment": "Next gets the next omap key/value pair referenced by\nReadOpOmapGetValsByKeysStep's internal iterator.\nIf there are no more elements to retrieve, (nil, nil) is returned.\nMay be called only after Operate() finished.\n PREVIEW\n",
+        "added_in_version": "v0.14.0",
+        "expected_stable_version": "v0.16.0"
+      },
+      {
+        "name": "ReadOp.GetOmapValuesByKeys",
+        "comment": "GetOmapValuesByKeys starts iterating over specific key/value pairs.\n PREVIEW\n\nImplements:\n void rados_read_op_omap_get_vals_by_keys(rados_read_op_t read_op,\n                                          char const * const * keys,\n                                          size_t keys_len,\n                                          rados_omap_iter_t * iter,\n                                          int * prval)\n",
+        "added_in_version": "v0.14.0",
+        "expected_stable_version": "v0.16.0"
       }
     ]
   },

docs/api-status.md

@@ -25,6 +25,8 @@ WriteOp.Remove | v0.14.0 | v0.16.0 |
 ReadOp.AssertVersion | v0.14.0 | v0.16.0 | 
 WriteOp.AssertVersion | v0.14.0 | v0.16.0 | 
 WriteOp.SetXattr | v0.14.0 | v0.16.0 | 
+ReadOpOmapGetValsByKeysStep.Next | v0.14.0 | v0.16.0 | 
+ReadOp.GetOmapValuesByKeys | v0.14.0 | v0.16.0 | 
 
 ## Package: rbd
 

rados/read_op_omap_get_vals_by_keys.go

@@ -0,0 +1,120 @@
+//go:build ceph_preview
+// +build ceph_preview
+
+package rados
+
+// #cgo LDFLAGS: -lrados
+// #include <rados/librados.h>
+// #include <stdlib.h>
+//
+import "C"
+
+import (
+	"unsafe"
+)
+
+// ReadOpOmapGetValsByKeysStep holds the result of the
+// GetOmapValuesByKeys read operation.
+// Result is valid only after Operate() was called.
+type ReadOpOmapGetValsByKeysStep struct {
+	// C arguments
+
+	iter  C.rados_omap_iter_t
+	prval *C.int
+
+	// Internal state
+
+	// canIterate is only set after the operation is performed and is
+	// intended to prevent premature fetching of data.
+	canIterate bool
+}
+
+func newReadOpOmapGetValsByKeysStep() *ReadOpOmapGetValsByKeysStep {
+	s := &ReadOpOmapGetValsByKeysStep{
+		prval: (*C.int)(C.malloc(C.sizeof_int)),
+	}
+
+	return s
+}
+
+func (s *ReadOpOmapGetValsByKeysStep) free() {
+	s.canIterate = false
+	C.rados_omap_get_end(s.iter)
+
+	C.free(unsafe.Pointer(s.prval))
+	s.prval = nil
+}
+
+func (s *ReadOpOmapGetValsByKeysStep) update() error {
+	err := getError(*s.prval)
+	s.canIterate = (err == nil)
+
+	return err
+}
+
+// Next gets the next omap key/value pair referenced by
+// ReadOpOmapGetValsByKeysStep's internal iterator.
+// If there are no more elements to retrieve, (nil, nil) is returned.
+// May be called only after Operate() finished.
+//  PREVIEW
+func (s *ReadOpOmapGetValsByKeysStep) Next() (*OmapKeyValue, error) {
+	if !s.canIterate {
+		return nil, ErrOperationIncomplete
+	}
+
+	var (
+		cKey    *C.char
+		cVal    *C.char
+		cValLen C.size_t
+	)
+
+	ret := C.rados_omap_get_next(s.iter, &cKey, &cVal, &cValLen)
+	if ret != 0 {
+		return nil, getError(ret)
+	}
+
+	if cKey == nil {
+		// Iterator has reached the end of the list.
+		return nil, nil
+	}
+
+	return &OmapKeyValue{
+		Key:   C.GoString(cKey),
+		Value: C.GoBytes(unsafe.Pointer(cVal), C.int(cValLen)),
+	}, nil
+}
+
+// GetOmapValuesByKeys starts iterating over specific key/value pairs.
+//  PREVIEW
+//
+// Implements:
+//  void rados_read_op_omap_get_vals_by_keys(rados_read_op_t read_op,
+//                                           char const * const * keys,
+//                                           size_t keys_len,
+//                                           rados_omap_iter_t * iter,
+//                                           int * prval)
+func (r *ReadOp) GetOmapValuesByKeys(keys []string) *ReadOpOmapGetValsByKeysStep {
+	s := newReadOpOmapGetValsByKeysStep()
+	r.steps = append(r.steps, s)
+
+	cKeys := make([]*C.char, len(keys))
+	defer func() {
+		for _, cKeyPtr := range cKeys {
+			C.free(unsafe.Pointer(cKeyPtr))
+		}
+	}()
+
+	for i, key := range keys {
+		cKeys[i] = C.CString(key)
+	}
+
+	C.rados_read_op_omap_get_vals_by_keys(
+		r.op,
+		&cKeys[0],
+		C.size_t(len(keys)),
+		&s.iter,
+		s.prval,
+	)
+
+	return s
+}

rados/read_op_omap_get_vals_by_keys_test.go

@@ -0,0 +1,62 @@
+//go:build ceph_preview
+// +build ceph_preview
+
+package rados
+
+import (
+	"github.com/stretchr/testify/assert"
+)
+
+func (suite *RadosTestSuite) TestReadOpOmapGetValsByKeys() {
+	suite.SetupConnection()
+	ta := assert.New(suite.T())
+
+	var (
+		oid = "TestReadOpOmapGetValsByKeys"
+		kvs = map[string][]byte{
+			"k1": []byte("v1"),
+			"k2": []byte("v2"),
+		}
+		err error
+	)
+
+	// Create an object and populate it with data.
+
+	op1 := CreateWriteOp()
+	defer op1.Release()
+	op1.Create(CreateIdempotent)
+	op1.SetOmap(kvs)
+	err = op1.Operate(suite.ioctx, oid, OperationNoFlag)
+	ta.NoError(err)
+
+	// Retrieve objects omap key-value pairs by ks keys, but add
+	// a few non-existingones which are expected to be silently skipped.
+
+	var (
+		actualKVs = make(map[string][]byte)
+		ks        = []string{"k1", "k2", "xx", "yy"}
+	)
+
+	op2 := CreateReadOp()
+	defer op2.Release()
+	kvStep := op2.GetOmapValuesByKeys(ks)
+
+	_, err = kvStep.Next()
+	ta.Equal(ErrOperationIncomplete, err)
+
+	err = op2.Operate(suite.ioctx, oid, OperationNoFlag)
+	ta.NoError(err)
+
+	for {
+		kv, err := kvStep.Next()
+		ta.NoError(err)
+
+		if kv == nil {
+			break
+		}
+
+		actualKVs[kv.Key] = kv.Value
+	}
+
+	ta.Equal(kvs, actualKVs)
+}