mirror of
https://github.com/seaweedfs/seaweedfs.git
synced 2024-12-25 18:27:54 +08:00
88 lines
2.7 KiB
Go
88 lines
2.7 KiB
Go
package erasure_coding
|
|
|
|
import (
|
|
"github.com/chrislusf/seaweedfs/weed/storage/types"
|
|
)
|
|
|
|
type Interval struct {
|
|
BlockIndex int
|
|
InnerBlockOffset int64
|
|
Size types.Size
|
|
IsLargeBlock bool
|
|
LargeBlockRowsCount int
|
|
}
|
|
|
|
func LocateData(largeBlockLength, smallBlockLength int64, datSize int64, offset int64, size types.Size) (intervals []Interval) {
|
|
blockIndex, isLargeBlock, innerBlockOffset := locateOffset(largeBlockLength, smallBlockLength, datSize, offset)
|
|
|
|
// adding DataShardsCount*smallBlockLength to ensure we can derive the number of large block size from a shard size
|
|
nLargeBlockRows := int((datSize + DataShardsCount*smallBlockLength) / (largeBlockLength * DataShardsCount))
|
|
|
|
for size > 0 {
|
|
interval := Interval{
|
|
BlockIndex: blockIndex,
|
|
InnerBlockOffset: innerBlockOffset,
|
|
IsLargeBlock: isLargeBlock,
|
|
LargeBlockRowsCount: nLargeBlockRows,
|
|
}
|
|
|
|
blockRemaining := largeBlockLength - innerBlockOffset
|
|
if !isLargeBlock {
|
|
blockRemaining = smallBlockLength - innerBlockOffset
|
|
}
|
|
|
|
if int64(size) <= blockRemaining {
|
|
interval.Size = size
|
|
intervals = append(intervals, interval)
|
|
return
|
|
}
|
|
interval.Size = types.Size(blockRemaining)
|
|
intervals = append(intervals, interval)
|
|
|
|
size -= interval.Size
|
|
blockIndex += 1
|
|
if isLargeBlock && blockIndex == nLargeBlockRows*DataShardsCount {
|
|
isLargeBlock = false
|
|
blockIndex = 0
|
|
}
|
|
innerBlockOffset = 0
|
|
|
|
}
|
|
return
|
|
}
|
|
|
|
func locateOffset(largeBlockLength, smallBlockLength int64, datSize int64, offset int64) (blockIndex int, isLargeBlock bool, innerBlockOffset int64) {
|
|
largeRowSize := largeBlockLength * DataShardsCount
|
|
nLargeBlockRows := datSize / (largeBlockLength * DataShardsCount)
|
|
|
|
// if offset is within the large block area
|
|
if offset < nLargeBlockRows*largeRowSize {
|
|
isLargeBlock = true
|
|
blockIndex, innerBlockOffset = locateOffsetWithinBlocks(largeBlockLength, offset)
|
|
return
|
|
}
|
|
|
|
isLargeBlock = false
|
|
offset -= nLargeBlockRows * largeRowSize
|
|
blockIndex, innerBlockOffset = locateOffsetWithinBlocks(smallBlockLength, offset)
|
|
return
|
|
}
|
|
|
|
func locateOffsetWithinBlocks(blockLength int64, offset int64) (blockIndex int, innerBlockOffset int64) {
|
|
blockIndex = int(offset / blockLength)
|
|
innerBlockOffset = offset % blockLength
|
|
return
|
|
}
|
|
|
|
func (interval Interval) ToShardIdAndOffset(largeBlockSize, smallBlockSize int64) (ShardId, int64) {
|
|
ecFileOffset := interval.InnerBlockOffset
|
|
rowIndex := interval.BlockIndex / DataShardsCount
|
|
if interval.IsLargeBlock {
|
|
ecFileOffset += int64(rowIndex) * largeBlockSize
|
|
} else {
|
|
ecFileOffset += int64(interval.LargeBlockRowsCount)*largeBlockSize + int64(rowIndex)*smallBlockSize
|
|
}
|
|
ecFileIndex := interval.BlockIndex % DataShardsCount
|
|
return ShardId(ecFileIndex), ecFileOffset
|
|
}
|