optimize cgo leveldb

reduce memory copy, reduce cgo call number

leveldb/db.go

@@ -4,6 +4,7 @@ package leveldb
 /*
 #cgo LDFLAGS: -lleveldb
 #include <leveldb/c.h>
+#include "leveldb_ext.h"
 */
 import "C"
 
@@ -210,7 +211,7 @@ func (db *DB) Clear() error {
 
 	num := 0
 	for ; it.Valid(); it.Next() {
-		bc.Delete(it.Key())
+		bc.Delete(it.RawKey())
 		num++
 		if num == 1000 {
 			num = 0
@@ -234,7 +235,11 @@ func (db *DB) SyncPut(key, value []byte) error {
 }
 
 func (db *DB) Get(key []byte) ([]byte, error) {
-	return db.get(db.readOpts, key)
+	return db.get(nil, db.readOpts, key)
+}
+
+func (db *DB) BufGet(r []byte, key []byte) ([]byte, error) {
+	return db.get(r, db.readOpts, key)
 }
 
 func (db *DB) Delete(key []byte) error {
@@ -317,7 +322,7 @@ func (db *DB) put(wo *WriteOptions, key, value []byte) error {
 	return nil
 }
 
-func (db *DB) get(ro *ReadOptions, key []byte) ([]byte, error) {
+func (db *DB) get(r []byte, ro *ReadOptions, key []byte) ([]byte, error) {
 	var errStr *C.char
 	var vallen C.size_t
 	var k *C.char
@@ -325,8 +330,10 @@ func (db *DB) get(ro *ReadOptions, key []byte) ([]byte, error) {
 		k = (*C.char)(unsafe.Pointer(&key[0]))
 	}
 
-	value := C.leveldb_get(
-		db.db, ro.Opt, k, C.size_t(len(key)), &vallen, &errStr)
+	var value *C.char
+
+	c := C.leveldb_get_ext(
+		db.db, ro.Opt, k, C.size_t(len(key)), &value, &vallen, &errStr)
 
 	if errStr != nil {
 		return nil, saveError(errStr)
@@ -336,8 +343,15 @@ func (db *DB) get(ro *ReadOptions, key []byte) ([]byte, error) {
 		return nil, nil
 	}
 
-	defer C.leveldb_free(unsafe.Pointer(value))
-	return C.GoBytes(unsafe.Pointer(value), C.int(vallen)), nil
+	defer C.leveldb_get_free_ext(unsafe.Pointer(c))
+
+	if int(C.int(vallen)) > len(r) {
+		return C.GoBytes(unsafe.Pointer(value), C.int(vallen)), nil
+	} else {
+		b := slice(unsafe.Pointer(value), int(C.int(vallen)))
+		n := copy(r, b)
+		return r[0:n], nil
+	}
 }
 
 func (db *DB) delete(wo *WriteOptions, key []byte) error {

leveldb/iterator.go

@@ -3,6 +3,7 @@ package leveldb
 // #cgo LDFLAGS: -lleveldb
 // #include <stdlib.h>
 // #include "leveldb/c.h"
+// #include "leveldb_ext.h"
 import "C"
 
 import (
@@ -41,9 +42,11 @@ type Limit struct {
 }
 
 type Iterator struct {
-	it *C.leveldb_iterator_t
+	it      *C.leveldb_iterator_t
+	isValid C.uchar
 }
 
+//Returns a copy of key.
 func (it *Iterator) Key() []byte {
 	var klen C.size_t
 	kdata := C.leveldb_iter_key(it.it, &klen)
@@ -54,6 +57,7 @@ func (it *Iterator) Key() []byte {
 	return C.GoBytes(unsafe.Pointer(kdata), C.int(klen))
 }
 
+//Returns a copy of value.
 func (it *Iterator) Value() []byte {
 	var vlen C.size_t
 	vdata := C.leveldb_iter_value(it.it, &vlen)
@@ -64,43 +68,95 @@ func (it *Iterator) Value() []byte {
 	return C.GoBytes(unsafe.Pointer(vdata), C.int(vlen))
 }
 
+//Returns a reference of key.
+//you must be careful that it will be changed after next iterate.
+func (it *Iterator) RawKey() []byte {
+	var klen C.size_t
+	kdata := C.leveldb_iter_key(it.it, &klen)
+	if kdata == nil {
+		return nil
+	}
+
+	return slice(unsafe.Pointer(kdata), int(C.int(klen)))
+}
+
+//Returns a reference of value.
+//you must be careful that it will be changed after next iterate.
+func (it *Iterator) RawValue() []byte {
+	var vlen C.size_t
+	vdata := C.leveldb_iter_value(it.it, &vlen)
+	if vdata == nil {
+		return nil
+	}
+
+	return slice(unsafe.Pointer(vdata), int(C.int(vlen)))
+}
+
+//Copy key to b, if b len is small or nil, returns a new one
+func (it *Iterator) BufKey(b []byte) []byte {
+	k := it.RawKey()
+	if k == nil {
+		return nil
+	}
+	if len(k) > len(b) {
+		b = make([]byte, len(k))
+	}
+
+	n := copy(b, k)
+	return b[0:n]
+}
+
+//Copy value to b, if b len is small or nil, returns a new one
+func (it *Iterator) BufValue(b []byte) []byte {
+	v := it.RawValue()
+	if v == nil {
+		return nil
+	}
+	if len(v) > len(b) {
+		b = make([]byte, len(v))
+	}
+
+	n := copy(b, v)
+	return b[0:n]
+}
+
 func (it *Iterator) Close() {
 	C.leveldb_iter_destroy(it.it)
 	it.it = nil
 }
 
 func (it *Iterator) Valid() bool {
-	return ucharToBool(C.leveldb_iter_valid(it.it))
+	return ucharToBool(it.isValid)
 }
 
 func (it *Iterator) Next() {
-	C.leveldb_iter_next(it.it)
+	it.isValid = C.leveldb_iter_next_ext(it.it)
 }
 
 func (it *Iterator) Prev() {
-	C.leveldb_iter_prev(it.it)
+	it.isValid = C.leveldb_iter_prev_ext(it.it)
 }
 
 func (it *Iterator) SeekToFirst() {
-	C.leveldb_iter_seek_to_first(it.it)
+	it.isValid = C.leveldb_iter_seek_to_first_ext(it.it)
 }
 
 func (it *Iterator) SeekToLast() {
-	C.leveldb_iter_seek_to_last(it.it)
+	it.isValid = C.leveldb_iter_seek_to_last_ext(it.it)
 }
 
 func (it *Iterator) Seek(key []byte) {
-	C.leveldb_iter_seek(it.it, (*C.char)(unsafe.Pointer(&key[0])), C.size_t(len(key)))
+	it.isValid = C.leveldb_iter_seek_ext(it.it, (*C.char)(unsafe.Pointer(&key[0])), C.size_t(len(key)))
 }
 
+//Finds by key, if not found, nil returns
 func (it *Iterator) Find(key []byte) []byte {
 	it.Seek(key)
 	if it.Valid() {
-		var klen C.size_t
-		kdata := C.leveldb_iter_key(it.it, &klen)
-		if kdata == nil {
+		k := it.RawKey()
+		if k == nil {
 			return nil
-		} else if bytes.Equal(slice(unsafe.Pointer(kdata), int(C.int(klen))), key) {
+		} else if bytes.Equal(k, key) {
 			return it.Value()
 		}
 	}
@@ -108,6 +164,22 @@ func (it *Iterator) Find(key []byte) []byte {
 	return nil
 }
 
+//Finds by key, if not found, nil returns, else a reference of value returns
+//you must be careful that it will be changed after next iterate.
+func (it *Iterator) RawFind(key []byte) []byte {
+	it.Seek(key)
+	if it.Valid() {
+		k := it.RawKey()
+		if k == nil {
+			return nil
+		} else if bytes.Equal(k, key) {
+			return it.RawValue()
+		}
+	}
+
+	return nil
+}
+
 type RangeLimitIterator struct {
 	it *Iterator
 
@@ -128,6 +200,14 @@ func (it *RangeLimitIterator) Value() []byte {
 	return it.it.Value()
 }
 
+func (it *RangeLimitIterator) RawKey() []byte {
+	return it.it.RawKey()
+}
+
+func (it *RangeLimitIterator) RawValue() []byte {
+	return it.it.RawValue()
+}
+
 func (it *RangeLimitIterator) Valid() bool {
 	if it.l.Offset < 0 {
 		return false
@@ -139,7 +219,7 @@ func (it *RangeLimitIterator) Valid() bool {
 
 	if it.direction == IteratorForward {
 		if it.r.Max != nil {
-			r := bytes.Compare(it.it.Key(), it.r.Max)
+			r := bytes.Compare(it.it.RawKey(), it.r.Max)
 			if it.r.Type&RangeROpen > 0 {
 				return !(r >= 0)
 			} else {
@@ -148,7 +228,7 @@ func (it *RangeLimitIterator) Valid() bool {
 		}
 	} else {
 		if it.r.Min != nil {
-			r := bytes.Compare(it.it.Key(), it.r.Min)
+			r := bytes.Compare(it.it.RawKey(), it.r.Min)
 			if it.r.Type&RangeLOpen > 0 {
 				return !(r <= 0)
 			} else {
@@ -204,7 +284,7 @@ func rangeLimitIterator(i *Iterator, r *Range, l *Limit, direction uint8) *Range
 			it.it.Seek(r.Min)
 
 			if r.Type&RangeLOpen > 0 {
-				if it.it.Valid() && bytes.Equal(it.it.Key(), r.Min) {
+				if it.it.Valid() && bytes.Equal(it.it.RawKey(), r.Min) {
 					it.it.Next()
 				}
 			}
@@ -218,13 +298,13 @@ func rangeLimitIterator(i *Iterator, r *Range, l *Limit, direction uint8) *Range
 			if !it.it.Valid() {
 				it.it.SeekToLast()
 			} else {
-				if !bytes.Equal(it.it.Key(), r.Max) {
+				if !bytes.Equal(it.it.RawKey(), r.Max) {
 					it.it.Prev()
 				}
 			}
 
 			if r.Type&RangeROpen > 0 {
-				if it.it.Valid() && bytes.Equal(it.it.Key(), r.Max) {
+				if it.it.Valid() && bytes.Equal(it.it.RawKey(), r.Max) {
 					it.it.Prev()
 				}
 			}

leveldb/leveldb_ext.cc

@@ -0,0 +1,86 @@
+#include "leveldb_ext.h"
+
+#include <stdlib.h>
+#include <string>
+
+#include "leveldb/db.h"
+
+using namespace leveldb;
+
+extern "C" {
+
+static bool SaveError(char** errptr, const Status& s) {
+  assert(errptr != NULL);
+  if (s.ok()) {
+    return false;
+  } else if (*errptr == NULL) {
+    *errptr = strdup(s.ToString().c_str());
+  } else {
+    free(*errptr);
+    *errptr = strdup(s.ToString().c_str());
+  }
+  return true;
+}
+
+void* leveldb_get_ext(
+    leveldb_t* db,
+    const leveldb_readoptions_t* options,
+    const char* key, size_t keylen,
+    char** valptr,
+    size_t* vallen,
+    char** errptr) {
+
+    std::string *tmp = new(std::string);
+
+    //very tricky, maybe changed with c++ leveldb upgrade
+    Status s = (*(DB**)db)->Get(*(ReadOptions*)options, Slice(key, keylen), tmp);
+
+    if (s.ok()) {
+        *valptr = (char*)tmp->data();
+        *vallen = tmp->size();
+    } else {
+        delete(tmp);
+        tmp = NULL;
+        *valptr = NULL;
+        *vallen = 0;
+        if (!s.IsNotFound()) {
+            SaveError(errptr, s);
+        }
+    }
+    return tmp;
+}
+
+void leveldb_get_free_ext(void* context) {
+    std::string* s = (std::string*)context;
+
+    delete(s);
+}
+
+
+unsigned char leveldb_iter_seek_to_first_ext(leveldb_iterator_t* iter) {
+    leveldb_iter_seek_to_first(iter);
+    return leveldb_iter_valid(iter);
+}
+
+unsigned char leveldb_iter_seek_to_last_ext(leveldb_iterator_t* iter) {
+    leveldb_iter_seek_to_last(iter);
+    return leveldb_iter_valid(iter);
+}
+
+unsigned char leveldb_iter_seek_ext(leveldb_iterator_t* iter, const char* k, size_t klen) {
+    leveldb_iter_seek(iter, k, klen);
+    return leveldb_iter_valid(iter);
+}
+
+unsigned char leveldb_iter_next_ext(leveldb_iterator_t* iter) {
+    leveldb_iter_next(iter);
+    return leveldb_iter_valid(iter);
+}
+
+unsigned char leveldb_iter_prev_ext(leveldb_iterator_t* iter) {
+    leveldb_iter_prev(iter);
+    return leveldb_iter_valid(iter);
+}
+
+
+}

leveldb/leveldb_ext.h

@@ -0,0 +1,38 @@
+#ifndef LEVELDB_EXT_H
+#define LEVELDB_EXT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "leveldb/c.h"
+
+
+/* Returns NULL if not found. Otherwise stores the value in **valptr.
+   Stores the length of the value in *vallen. 
+   Returns a context must be later to free*/
+extern void* leveldb_get_ext(
+    leveldb_t* db,
+    const leveldb_readoptions_t* options,
+    const char* key, size_t keylen,
+    char** valptr,
+    size_t* vallen,
+    char** errptr);
+
+// Free context returns by leveldb_get_ext
+extern void leveldb_get_free_ext(void* context);
+
+
+// Below iterator functions like leveldb iterator but returns valid status for iterator
+extern unsigned char leveldb_iter_seek_to_first_ext(leveldb_iterator_t*);
+extern unsigned char leveldb_iter_seek_to_last_ext(leveldb_iterator_t*);
+extern unsigned char leveldb_iter_seek_ext(leveldb_iterator_t*, const char* k, size_t klen);
+extern unsigned char leveldb_iter_next_ext(leveldb_iterator_t*);
+extern unsigned char leveldb_iter_prev_ext(leveldb_iterator_t*);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

leveldb/snapshot.go

@@ -22,7 +22,11 @@ func (s *Snapshot) Close() {
 }
 
 func (s *Snapshot) Get(key []byte) ([]byte, error) {
-	return s.db.get(s.readOpts, key)
+	return s.db.get(nil, s.readOpts, key)
+}
+
+func (s *Snapshot) BufGet(r []byte, key []byte) ([]byte, error) {
+	return s.db.get(r, s.readOpts, key)
 }
 
 func (s *Snapshot) NewIterator() *Iterator {