67 lines
1.8 KiB
Go
67 lines
1.8 KiB
Go
package levigo
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// #cgo LDFLAGS: -lleveldb
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// #include "leveldb/c.h"
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import "C"
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import (
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"unsafe"
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)
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// WriteBatch is a batching of Puts, and Deletes to be written atomically to a
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// database. A WriteBatch is written when passed to DB.Write.
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//
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// To prevent memory leaks, call Close when the program no longer needs the
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// WriteBatch object.
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type WriteBatch struct {
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wbatch *C.leveldb_writebatch_t
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}
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// NewWriteBatch creates a fully allocated WriteBatch.
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func NewWriteBatch() *WriteBatch {
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wb := C.leveldb_writebatch_create()
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return &WriteBatch{wb}
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}
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// Close releases the underlying memory of a WriteBatch.
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func (w *WriteBatch) Close() {
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C.leveldb_writebatch_destroy(w.wbatch)
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}
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// Put places a key-value pair into the WriteBatch for writing later.
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//
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// Both the key and value byte slices may be reused as WriteBatch takes a copy
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// of them before returning.
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//
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func (w *WriteBatch) Put(key, value []byte) {
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// leveldb_writebatch_put, and _delete call memcpy() (by way of
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// Memtable::Add) when called, so we do not need to worry about these
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// []byte being reclaimed by GC.
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var k, v *C.char
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if len(key) != 0 {
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k = (*C.char)(unsafe.Pointer(&key[0]))
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}
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if len(value) != 0 {
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v = (*C.char)(unsafe.Pointer(&value[0]))
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}
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lenk := len(key)
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lenv := len(value)
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C.leveldb_writebatch_put(w.wbatch, k, C.size_t(lenk), v, C.size_t(lenv))
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}
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// Delete queues a deletion of the data at key to be deleted later.
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//
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// The key byte slice may be reused safely. Delete takes a copy of
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// them before returning.
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func (w *WriteBatch) Delete(key []byte) {
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C.leveldb_writebatch_delete(w.wbatch,
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(*C.char)(unsafe.Pointer(&key[0])), C.size_t(len(key)))
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}
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// Clear removes all the enqueued Put and Deletes in the WriteBatch.
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func (w *WriteBatch) Clear() {
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C.leveldb_writebatch_clear(w.wbatch)
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}
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