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maxsize.go
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maxsize.go
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package blobstore
// Copyright 2019 Vivino. All rights reserved
//
// See LICENSE file for license details
import (
"context"
"encoding/binary"
"errors"
"fmt"
"math"
"strconv"
"sync"
"github.com/Vivino/rankdb/log"
)
// MaxSizeStore will make sure that no blobs are above the specified size.
// The upper storage limit is 65535 * maximum size.
type MaxSizeStore struct {
store Store
maxsize int
// Cache parts size.
// No entry means one or unknown number of segments.
parts map[string]int
running map[string]*sync.Mutex
mu sync.Mutex
}
// NewMaxSizeStore will split blobs into the specified size.
// Specify the upper byte limit.
// The upper storage limit is 65535 * maximum size.
func NewMaxSizeStore(store Store, maxSize int) (*MaxSizeStore, error) {
if maxSize < 1024 {
return nil, fmt.Errorf("max size should be more than 1KB")
}
r := MaxSizeStore{
store: store,
maxsize: maxSize,
parts: make(map[string]int),
running: make(map[string]*sync.Mutex),
}
return &r, nil
}
func mapKey(set, key string) string {
return set + `/\` + key
}
func extKey(key string, n int) string {
return key + "+" + strconv.Itoa(n)
}
func (r *MaxSizeStore) runningOp(set, key string) func() {
r.mu.Lock()
mu := r.running[mapKey(set, key)]
if mu == nil {
mu = &sync.Mutex{}
r.running[mapKey(set, key)] = mu
}
r.mu.Unlock()
mu.Lock()
return mu.Unlock
}
// Get a blob.
func (r *MaxSizeStore) Get(ctx context.Context, set, key string) ([]byte, error) {
defer r.runningOp(set, key)()
b, err := r.store.Get(ctx, set, key)
if err != nil {
return nil, err
}
n, size := binary.Uvarint(b)
if size < 1 {
return nil, errors.New("corrupt blob")
}
b = b[size:]
if n == 0 {
r.mu.Lock()
delete(r.parts, mapKey(set, key))
r.mu.Unlock()
return b, nil
}
r.mu.Lock()
r.parts[mapKey(set, key)] = int(n + 1)
r.mu.Unlock()
for i := 0; i < int(n); i++ {
b2, err := r.store.Get(ctx, set, extKey(key, i))
if err != nil {
return nil, err
}
b = append(b, b2...)
}
return b, nil
}
// Set a blob.
func (r *MaxSizeStore) Set(ctx context.Context, set, key string, b []byte) error {
defer r.runningOp(set, key)()
total := (len(b) + binary.MaxVarintLen16 + r.maxsize - 1) / r.maxsize
if total == 0 {
panic("incomprehensible")
}
if total >= math.MaxUint16 {
return ErrBlobTooBig
}
var buf [binary.MaxVarintLen16]byte
var bbuf = buf[:]
s := binary.PutUvarint(bbuf[:], uint64(total-1))
// delete extra parts if more.
// Since we are saving it is extremely likely a load has previously been done.
r.mu.Lock()
prev := r.parts[mapKey(set, key)]
r.mu.Unlock()
for i := total; i < prev; i++ {
kkey := extKey(key, i-1)
err := r.store.Delete(ctx, set, kkey)
if err != nil {
log.Error(ctx, "Error deleting extra segments", "error", err, "key", kkey, "set", set)
}
}
// Prepend total
b2 := make([]byte, len(b)+s)
copy(b2, buf[:s])
copy(b2[s:], b)
for i := 0; i < total; i++ {
kkey := key
if i > 0 {
kkey = extKey(key, i-1)
}
l := r.maxsize
if l > len(b2) {
l = len(b2)
}
b = b2[:l]
err := r.store.Set(ctx, set, kkey, b)
if err != nil {
return err
}
b2 = b2[l:]
}
r.mu.Lock()
if total == 1 {
delete(r.parts, mapKey(set, key))
} else {
r.parts[mapKey(set, key)] = total
}
r.mu.Unlock()
return nil
}
// Delete a blob.
func (r *MaxSizeStore) Delete(ctx context.Context, set, key string) error {
defer r.runningOp(set, key)()
r.mu.Lock()
n := uint64(r.parts[mapKey(set, key)])
r.mu.Unlock()
if n == 0 {
b, err := r.store.Get(ctx, set, key)
if err != nil {
return nil
}
var size int
n, size = binary.Uvarint(b)
if size < 1 {
n = 0
}
n++
}
for i := 0; i < int(n); i++ {
kkey := key
if i > 0 {
kkey = extKey(key, i-1)
}
err := r.store.Delete(ctx, set, kkey)
if err != nil {
return err
}
}
r.mu.Lock()
delete(r.parts, mapKey(set, key))
r.mu.Unlock()
return nil
}