/
nodetable.go
173 lines (141 loc) · 3.02 KB
/
nodetable.go
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package happy
import (
"bufio"
"encoding/binary"
"hash/fnv"
"io"
"os"
"time"
//"github.com/petar/GoLLRB/llrb"
)
const (
nodetableVersion = uint16(1)
nodetablePersistentThreshold = 1e6
nodetableBloomSize = 5e8
nodetableBloomIterations = 3
nodetableBloomArraysize = nodetableBloomSize / 8
)
// TODO:
// - Add commit log and log removal on nodetable write-to-disk
type nodetableIdx int
type nodetable struct {
filename string
created uint64 // timestamp in ns
bitmap []byte
idx nodetableIdx
}
func loadNodetable(filename string) *nodetable {
// TODO
return nil
}
type bufferedWriteCounter struct {
bw *bufio.Writer
size int
}
func newBufferedWriteCounter(w io.Writer) *bufferedWriteCounter {
return &bufferedWriteCounter{
bw: bufio.NewWriter(w),
}
}
func (wc *bufferedWriteCounter) Size() int {
return wc.size
}
func (wc *bufferedWriteCounter) Write(p []byte) (nn int, err error) {
wc.size += len(p)
return wc.bw.Write(p)
}
func (wc *bufferedWriteCounter) Flush() error {
return wc.bw.Flush()
}
func createNodetable(memtable map[uint64]*node, filename string) (*nodetable, error) {
nt := &nodetable{
filename: filename,
created: uint64(time.Now().Nanosecond()),
bitmap: make([]byte, nodetableBloomArraysize),
}
fd, err := os.Create(filename)
if err != nil {
return nil, err
}
defer func() {
err := fd.Close()
if err != nil {
panic(err)
}
}()
wd := newBufferedWriteCounter(fd)
defer func() {
err := wd.Flush()
if err != nil {
panic(err)
}
}()
// Version nodetable_version
err = binary.Write(wd, binary.BigEndian, nodetableVersion)
if err != nil {
return nil, err
}
// Timestamp
err = binary.Write(wd, binary.BigEndian, nt.created)
if err != nil {
return nil, err
}
// Build the bitmap
for k := range memtable {
markBitmap(k, nt)
}
// Write bitmap
_, err = wd.Write(nt.bitmap)
if err != nil {
return nil, err
}
todoList := make(map[uint64]struct{})
empty := struct{}{}
index := make(map[uint64]int)
var start *node
for k, v := range memtable {
if start == nil {
start = v
}
todoList[k] = empty
}
for {
// Remove from todo list
delete(todoList, start.id)
// Write start node
index[start.id] = wd.Size()
err := start.write(wd)
if err != nil {
return nil, err
}
// Write all connected nodes recursively
err = start.writeNeighbours(wd, memtable, index, todoList)
if err != nil {
return nil, err
}
// TODO: Optimize this bookkeeping and checking
if len(index) == len(memtable) {
break
}
// We still have a node left which is not recorded yet
for k := range todoList {
start = memtable[k]
break
}
}
// Write index
return nt, nil
}
func markBitmap(x uint64, n *nodetable) {
for i := 0; i < nodetableBloomIterations; i++ {
h := fnv.New64a()
err := binary.Write(h, binary.BigEndian, x)
if err != nil {
panic(err)
}
x = h.Sum64()
bitpos := x % nodetableBloomSize
arraypos := bitpos / 8
n.bitmap[arraypos] = n.bitmap[arraypos] | (1 << (bitpos % 8))
}
}