forked from perkeep/perkeep
/
memfiler.go
344 lines (296 loc) · 7.99 KB
/
memfiler.go
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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// A memory-only implementation of Filer.
/*
pgBits: 8
BenchmarkMemFilerWrSeq 100000 19430 ns/op 1646.93 MB/s
BenchmarkMemFilerRdSeq 100000 17390 ns/op 1840.13 MB/s
BenchmarkMemFilerWrRand 1000000 1903 ns/op 133.94 MB/s
BenchmarkMemFilerRdRand 1000000 1153 ns/op 221.16 MB/s
pgBits: 9
BenchmarkMemFilerWrSeq 100000 16195 ns/op 1975.80 MB/s
BenchmarkMemFilerRdSeq 200000 13011 ns/op 2459.39 MB/s
BenchmarkMemFilerWrRand 1000000 2248 ns/op 227.28 MB/s
BenchmarkMemFilerRdRand 1000000 1177 ns/op 433.94 MB/s
pgBits: 10
BenchmarkMemFilerWrSeq 100000 16169 ns/op 1979.04 MB/s
BenchmarkMemFilerRdSeq 200000 12673 ns/op 2524.91 MB/s
BenchmarkMemFilerWrRand 1000000 5550 ns/op 184.30 MB/s
BenchmarkMemFilerRdRand 1000000 1699 ns/op 601.79 MB/s
pgBits: 11
BenchmarkMemFilerWrSeq 100000 13449 ns/op 2379.31 MB/s
BenchmarkMemFilerRdSeq 200000 12058 ns/op 2653.80 MB/s
BenchmarkMemFilerWrRand 500000 4335 ns/op 471.47 MB/s
BenchmarkMemFilerRdRand 1000000 2843 ns/op 719.47 MB/s
pgBits: 12
BenchmarkMemFilerWrSeq 200000 11976 ns/op 2672.00 MB/s
BenchmarkMemFilerRdSeq 200000 12255 ns/op 2611.06 MB/s
BenchmarkMemFilerWrRand 200000 8058 ns/op 507.14 MB/s
BenchmarkMemFilerRdRand 500000 4365 ns/op 936.15 MB/s
pgBits: 13
BenchmarkMemFilerWrSeq 200000 10852 ns/op 2948.69 MB/s
BenchmarkMemFilerRdSeq 200000 11561 ns/op 2767.77 MB/s
BenchmarkMemFilerWrRand 200000 9748 ns/op 840.15 MB/s
BenchmarkMemFilerRdRand 500000 7236 ns/op 1131.59 MB/s
pgBits: 14
BenchmarkMemFilerWrSeq 200000 10328 ns/op 3098.12 MB/s
BenchmarkMemFilerRdSeq 200000 11292 ns/op 2833.66 MB/s
BenchmarkMemFilerWrRand 100000 16768 ns/op 978.75 MB/s
BenchmarkMemFilerRdRand 200000 13033 ns/op 1258.43 MB/s
pgBits: 15
BenchmarkMemFilerWrSeq 200000 10309 ns/op 3103.93 MB/s
BenchmarkMemFilerRdSeq 200000 11126 ns/op 2876.12 MB/s
BenchmarkMemFilerWrRand 50000 31985 ns/op 1021.74 MB/s
BenchmarkMemFilerRdRand 100000 25217 ns/op 1297.65 MB/s
pgBits: 16
BenchmarkMemFilerWrSeq 200000 10324 ns/op 3099.45 MB/s
BenchmarkMemFilerRdSeq 200000 11201 ns/op 2856.80 MB/s
BenchmarkMemFilerWrRand 20000 55226 ns/op 1184.76 MB/s
BenchmarkMemFilerRdRand 50000 48316 ns/op 1355.16 MB/s
pgBits: 17
BenchmarkMemFilerWrSeq 200000 10377 ns/op 3083.53 MB/s
BenchmarkMemFilerRdSeq 200000 11018 ns/op 2904.18 MB/s
BenchmarkMemFilerWrRand 10000 143425 ns/op 913.12 MB/s
BenchmarkMemFilerRdRand 20000 95267 ns/op 1376.99 MB/s
pgBits: 18
BenchmarkMemFilerWrSeq 200000 10312 ns/op 3102.96 MB/s
BenchmarkMemFilerRdSeq 200000 11069 ns/op 2890.84 MB/s
BenchmarkMemFilerWrRand 5000 280910 ns/op 934.14 MB/s
BenchmarkMemFilerRdRand 10000 188500 ns/op 1388.17 MB/s
*/
package lldb
import (
"bytes"
"fmt"
"io"
"camlistore.org/third_party/github.com/cznic/fileutil"
"camlistore.org/third_party/github.com/cznic/mathutil"
)
const (
pgBits = 16
pgSize = 1 << pgBits
pgMask = pgSize - 1
)
var _ Filer = &MemFiler{} // Ensure MemFiler is a Filer.
type memFilerMap map[int64]*[pgSize]byte
// MemFiler is a memory backed Filer. It implements BeginUpdate, EndUpdate and
// Rollback as no-ops. MemFiler is not automatically persistent, but it has
// ReadFrom and WriteTo methods.
type MemFiler struct {
m memFilerMap
nest int
size int64
}
// NewMemFiler returns a new MemFiler.
func NewMemFiler() *MemFiler {
return &MemFiler{m: memFilerMap{}}
}
// BeginUpdate implements Filer.
func (f *MemFiler) BeginUpdate() error {
f.nest++
return nil
}
// Close implements Filer.
func (f *MemFiler) Close() (err error) {
if f.nest != 0 {
return &ErrPERM{(f.Name() + ":Close")}
}
return
}
// EndUpdate implements Filer.
func (f *MemFiler) EndUpdate() (err error) {
if f.nest == 0 {
return &ErrPERM{(f.Name() + ": EndUpdate")}
}
f.nest--
return
}
// Name implements Filer.
func (f *MemFiler) Name() string {
return fmt.Sprintf("%p.memfiler", f)
}
// PunchHole implements Filer.
func (f *MemFiler) PunchHole(off, size int64) (err error) {
if off < 0 {
return &ErrINVAL{f.Name() + ": PunchHole off", off}
}
if size < 0 || off+size > f.size {
return &ErrINVAL{f.Name() + ": PunchHole size", size}
}
first := off >> pgBits
if off&pgMask != 0 {
first++
}
off += size - 1
last := off >> pgBits
if off&pgMask != 0 {
last--
}
if limit := f.size >> pgBits; last > limit {
last = limit
}
for pg := first; pg <= last; pg++ {
delete(f.m, pg)
}
return
}
var zeroPage [pgSize]byte
// ReadAt implements Filer.
func (f *MemFiler) ReadAt(b []byte, off int64) (n int, err error) {
avail := f.size - off
pgI := off >> pgBits
pgO := int(off & pgMask)
rem := len(b)
if int64(rem) >= avail {
rem = int(avail)
err = io.EOF
}
for rem != 0 && avail > 0 {
pg := f.m[pgI]
if pg == nil {
pg = &zeroPage
}
nc := copy(b[:mathutil.Min(rem, pgSize)], pg[pgO:])
pgI++
pgO = 0
rem -= nc
n += nc
b = b[nc:]
}
return
}
// ReadFrom is a helper to populate MemFiler's content from r. 'n' reports the
// number of bytes read from 'r'.
func (f *MemFiler) ReadFrom(r io.Reader) (n int64, err error) {
if err = f.Truncate(0); err != nil {
return
}
var (
b [pgSize]byte
rn int
off int64
)
var rerr error
for rerr == nil {
if rn, rerr = r.Read(b[:]); rn != 0 {
f.WriteAt(b[:rn], off)
off += int64(rn)
n += int64(rn)
}
}
if !fileutil.IsEOF(rerr) {
err = rerr
}
return
}
// Rollback implements Filer.
func (f *MemFiler) Rollback() (err error) { return }
// Size implements Filer.
func (f *MemFiler) Size() (int64, error) {
return f.size, nil
}
// Sync implements Filer.
func (f *MemFiler) Sync() error {
return nil
}
// Truncate implements Filer.
func (f *MemFiler) Truncate(size int64) (err error) {
switch {
case size < 0:
return &ErrINVAL{"Truncate size", size}
case size == 0:
f.m = memFilerMap{}
f.size = 0
return
}
first := size >> pgBits
if size&pgMask != 0 {
first++
}
last := f.size >> pgBits
if f.size&pgMask != 0 {
last++
}
for ; first < last; first++ {
delete(f.m, first)
}
f.size = size
return
}
// WriteAt implements Filer.
func (f *MemFiler) WriteAt(b []byte, off int64) (n int, err error) {
pgI := off >> pgBits
pgO := int(off & pgMask)
n = len(b)
rem := n
var nc int
for rem != 0 {
if pgO == 0 && rem >= pgSize && bytes.Equal(b[:pgSize], zeroPage[:]) {
delete(f.m, pgI)
nc = pgSize
} else {
pg := f.m[pgI]
if pg == nil {
pg = new([pgSize]byte)
f.m[pgI] = pg
}
nc = copy((*pg)[pgO:], b)
}
pgI++
pgO = 0
rem -= nc
b = b[nc:]
}
f.size = mathutil.MaxInt64(f.size, off+int64(n))
return
}
// WriteTo is a helper to copy/persist MemFiler's content to w. If w is also
// an io.WriterAt then WriteTo may attempt to _not_ write any big, for some
// value of big, runs of zeros, i.e. it will attempt to punch holes, where
// possible, in `w` if that happens to be a freshly created or to zero length
// truncated OS file. 'n' reports the number of bytes written to 'w'.
func (f *MemFiler) WriteTo(w io.Writer) (n int64, err error) {
var (
b [pgSize]byte
wn, rn int
off int64
rerr error
)
if wa, ok := w.(io.WriterAt); ok {
lastPgI := f.size >> pgBits
for pgI := int64(0); pgI <= lastPgI; pgI++ {
sz := pgSize
if pgI == lastPgI {
sz = int(f.size & pgMask)
}
pg := f.m[pgI]
if pg != nil {
wn, err = wa.WriteAt(pg[:sz], off)
if err != nil {
return
}
n += int64(wn)
off += int64(sz)
if wn != sz {
return n, io.ErrShortWrite
}
}
}
return
}
var werr error
for rerr == nil {
if rn, rerr = f.ReadAt(b[:], off); rn != 0 {
off += int64(rn)
if wn, werr = w.Write(b[:rn]); werr != nil {
return n, werr
}
n += int64(wn)
}
}
if !fileutil.IsEOF(rerr) {
err = rerr
}
return
}