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|
package compressor
import (
"encoding/binary"
"fmt"
"sort"
)
type OriginalTable struct {
entries []int
rowCount int
colCount int
}
func NewOriginalTable(entries []int, colCount int) (*OriginalTable, error) {
if len(entries) == 0 {
return nil, fmt.Errorf("enries is empty")
}
if colCount <= 0 {
return nil, fmt.Errorf("colCount must be >=1")
}
if len(entries)%colCount != 0 {
return nil, fmt.Errorf("entries length or column count are incorrect; entries length: %v, column count: %v", len(entries), colCount)
}
return &OriginalTable{
entries: entries,
rowCount: len(entries) / colCount,
colCount: colCount,
}, nil
}
type Compressor interface {
Compress(orig *OriginalTable) error
Lookup(row, col int) (int, error)
OriginalTableSize() (int, int)
}
var (
_ Compressor = &UniqueEntriesTable{}
_ Compressor = &RowDisplacementTable{}
)
type UniqueEntriesTable struct {
UniqueEntries []int
RowNums []int
OriginalRowCount int
OriginalColCount int
}
func NewUniqueEntriesTable() *UniqueEntriesTable {
return &UniqueEntriesTable{}
}
func (tab *UniqueEntriesTable) Lookup(row, col int) (int, error) {
if row < 0 || row >= tab.OriginalRowCount || col < 0 || col >= tab.OriginalColCount {
return 0, fmt.Errorf("indexes are out of range: [%v, %v]", row, col)
}
return tab.UniqueEntries[tab.RowNums[row]*tab.OriginalColCount+col], nil
}
func (tab *UniqueEntriesTable) OriginalTableSize() (int, int) {
return tab.OriginalRowCount, tab.OriginalColCount
}
func (tab *UniqueEntriesTable) Compress(orig *OriginalTable) error {
var uniqueEntries []int
rowNums := make([]int, orig.rowCount)
hash2RowNum := map[string]int{}
nextRowNum := 0
for row := 0; row < orig.rowCount; row++ {
var rowHash string
{
buf := make([]byte, 0, orig.colCount*8)
for col := 0; col < orig.colCount; col++ {
b := make([]byte, 8)
binary.PutUvarint(b, uint64(orig.entries[row*orig.colCount+col]))
buf = append(buf, b...)
}
rowHash = string(buf)
}
rowNum, ok := hash2RowNum[rowHash]
if !ok {
rowNum = nextRowNum
nextRowNum++
hash2RowNum[rowHash] = rowNum
start := row * orig.colCount
entry := append([]int{}, orig.entries[start:start+orig.colCount]...)
uniqueEntries = append(uniqueEntries, entry...)
}
rowNums[row] = rowNum
}
tab.UniqueEntries = uniqueEntries
tab.RowNums = rowNums
tab.OriginalRowCount = orig.rowCount
tab.OriginalColCount = orig.colCount
return nil
}
const ForbiddenValue = -1
type RowDisplacementTable struct {
OriginalRowCount int
OriginalColCount int
EmptyValue int
Entries []int
Bounds []int
RowDisplacement []int
}
func NewRowDisplacementTable(emptyValue int) *RowDisplacementTable {
return &RowDisplacementTable{
EmptyValue: emptyValue,
}
}
func (tab *RowDisplacementTable) Lookup(row int, col int) (int, error) {
if row < 0 || row >= tab.OriginalRowCount || col < 0 || col >= tab.OriginalColCount {
return tab.EmptyValue, fmt.Errorf("indexes are out of range: [%v, %v]", row, col)
}
d := tab.RowDisplacement[row]
if tab.Bounds[d+col] != row {
return tab.EmptyValue, nil
}
return tab.Entries[d+col], nil
}
func (tab *RowDisplacementTable) OriginalTableSize() (int, int) {
return tab.OriginalRowCount, tab.OriginalColCount
}
type rowInfo struct {
rowNum int
nonEmptyCount int
nonEmptyCol []int
}
func (tab *RowDisplacementTable) Compress(orig *OriginalTable) error {
rowInfo := make([]rowInfo, orig.rowCount)
{
row := 0
col := 0
rowInfo[0].rowNum = 0
for _, v := range orig.entries {
if col == orig.colCount {
row++
col = 0
rowInfo[row].rowNum = row
}
if v != tab.EmptyValue {
rowInfo[row].nonEmptyCount++
rowInfo[row].nonEmptyCol = append(rowInfo[row].nonEmptyCol, col)
}
col++
}
sort.SliceStable(rowInfo, func(i int, j int) bool {
return rowInfo[i].nonEmptyCount > rowInfo[j].nonEmptyCount
})
}
origEntriesLen := len(orig.entries)
entries := make([]int, origEntriesLen)
bounds := make([]int, origEntriesLen)
resultBottom := orig.colCount
rowDisplacement := make([]int, orig.rowCount)
{
for i := 0; i < origEntriesLen; i++ {
entries[i] = tab.EmptyValue
bounds[i] = ForbiddenValue
}
nextRowDisplacement := 0
for _, rInfo := range rowInfo {
if rInfo.nonEmptyCount <= 0 {
continue
}
for {
isOverlapped := false
for _, col := range rInfo.nonEmptyCol {
if entries[nextRowDisplacement+col] == tab.EmptyValue {
continue
}
nextRowDisplacement++
isOverlapped = true
break
}
if isOverlapped {
continue
}
rowDisplacement[rInfo.rowNum] = nextRowDisplacement
for _, col := range rInfo.nonEmptyCol {
entries[nextRowDisplacement+col] = orig.entries[(rInfo.rowNum*orig.colCount)+col]
bounds[nextRowDisplacement+col] = rInfo.rowNum
}
resultBottom = nextRowDisplacement + orig.colCount
nextRowDisplacement++
break
}
}
}
tab.OriginalRowCount = orig.rowCount
tab.OriginalColCount = orig.colCount
tab.Entries = entries[:resultBottom]
tab.Bounds = bounds[:resultBottom]
tab.RowDisplacement = rowDisplacement
return nil
}
|
