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// Copyright (c) 2010-2012 OpenStack Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"errors"
"fmt"
"strconv"
)
// getPartitionFromOhash returns the partition, given an object hash and the partition bit count
func getPartitionFromOhash(ohash []byte, partitionBits int) (partition uint64, err error) {
if len(ohash) < 16 {
err = errors.New("ohash must be at least 16 bits long")
return
}
highHash, err := strconv.ParseUint(string(ohash[0:16]), 16, 64)
if err != nil {
return
}
// shift to get the partition
partition = highHash >> uint64(64-partitionBits)
return
}
// getLastPartition returns the last possible partition given the partition bit count
func getLastPartition(partitionBits int) (partition uint64, err error) {
for i := 0; i < partitionBits; i++ {
partition |= 1 << uint64(i)
}
return
}
// Returns the first possible object prefix the KV for the given partition and bit count
// Example: 876, 18 bits -> 00db000000000000
func getObjPrefixFromPartition(partition uint64, partitionBits int) (prefix []byte, err error) {
firstnum := partition << uint64(64-partitionBits)
prefix = []byte(fmt.Sprintf("%016x0000000000000000", firstnum))
return
}
// Returns the first possible object prefix the KV for the given partition and bit count,
// in its encoded form
func getEncodedObjPrefixFromPartition(partition uint64, partitionBits int) (prefix []byte, err error) {
key, err := getObjPrefixFromPartition(partition, partitionBits)
if err != nil {
return
}
prefix, err = EncodeObjectKey(key)
return
}
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