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mem.go
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mem.go
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// Package mem is an example REST backend storage that stores everything in memory.
package mem
import (
"bytes"
"encoding/gob"
"sort"
"sync"
"time"
"github.com/cool-rest/rest-layer/resource"
"golang.org/x/net/context"
)
// MemoryHandler is an example handler storing data in memory
type MemoryHandler struct {
sync.RWMutex
// If latency is set, the handler will introduce an artificial latency on
// all operations
Latency time.Duration
items map[interface{}][]byte
ids []interface{}
}
func init() {
gob.Register(map[string]interface{}{})
gob.Register(time.Time{})
}
// NewHandler creates an empty memory handler
func NewHandler() *MemoryHandler {
return &MemoryHandler{
items: map[interface{}][]byte{},
ids: []interface{}{},
}
}
// NewSlowHandler creates an empty memory handler with specified latency
func NewSlowHandler(latency time.Duration) *MemoryHandler {
return &MemoryHandler{
Latency: latency,
items: map[interface{}][]byte{},
ids: []interface{}{},
}
}
// store serialize the item using gob and store it in the handler's items map
func (m *MemoryHandler) store(item *resource.Item) error {
var data bytes.Buffer
enc := gob.NewEncoder(&data)
if err := enc.Encode(*item); err != nil {
return err
}
m.items[item.ID] = data.Bytes()
return nil
}
// fetch unserialize item's data and return a new item
func (m *MemoryHandler) fetch(id interface{}) (*resource.Item, bool, error) {
data, found := m.items[id]
if !found {
return nil, false, nil
}
dec := gob.NewDecoder(bytes.NewBuffer(data))
var item resource.Item
if err := dec.Decode(&item); err != nil {
return nil, true, err
}
return &item, true, nil
}
// delete removes an item by this id with no look
func (m *MemoryHandler) delete(id interface{}) {
delete(m.items, id)
// Remove id from id list
for i, _id := range m.ids {
if _id == id {
if i >= len(m.ids)-1 {
m.ids = m.ids[:i]
} else {
m.ids = append(m.ids[:i], m.ids[i+1:]...)
}
break
}
}
}
// Insert inserts new items in memory
func (m *MemoryHandler) Insert(ctx context.Context, items []*resource.Item) (err error) {
m.Lock()
defer m.Unlock()
err = handleWithLatency(m.Latency, ctx, func() error {
for _, item := range items {
if _, found := m.items[item.ID]; found {
return resource.ErrConflict
}
}
for _, item := range items {
if err := m.store(item); err != nil {
return err
}
// Store ids in ordered slice for sorting
m.ids = append(m.ids, item.ID)
}
return nil
})
return err
}
// Update replace an item by a new one in memory
func (m *MemoryHandler) Update(ctx context.Context, item *resource.Item, original *resource.Item) (err error) {
m.Lock()
defer m.Unlock()
err = handleWithLatency(m.Latency, ctx, func() error {
o, found, err := m.fetch(original.ID)
if !found {
return resource.ErrNotFound
}
if err != nil {
return err
}
if original.ETag != o.ETag {
return resource.ErrConflict
}
if err := m.store(item); err != nil {
return err
}
return nil
})
return err
}
// Delete deletes an item from memory
func (m *MemoryHandler) Delete(ctx context.Context, item *resource.Item) (err error) {
m.Lock()
defer m.Unlock()
err = handleWithLatency(m.Latency, ctx, func() error {
o, found, err := m.fetch(item.ID)
if !found {
return resource.ErrNotFound
}
if err != nil {
return err
}
if item.ETag != o.ETag {
return resource.ErrConflict
}
m.delete(item.ID)
return nil
})
return err
}
// Clear clears all items from the memory store matching the lookup
func (m *MemoryHandler) Clear(ctx context.Context, lookup *resource.Lookup) (total int, err error) {
m.Lock()
defer m.Unlock()
err = handleWithLatency(m.Latency, ctx, func() error {
ids := make([]interface{}, len(m.ids))
copy(ids, m.ids)
for _, id := range ids {
item, _, err := m.fetch(id)
if err != nil {
return err
}
if !lookup.Filter().Match(item.Payload) {
continue
}
m.delete(item.ID)
total++
}
return nil
})
return total, err
}
// Find items from memory matching the provided lookup
func (m *MemoryHandler) Find(ctx context.Context, lookup *resource.Lookup, page, perPage int) (list *resource.ItemList, err error) {
m.RLock()
defer m.RUnlock()
err = handleWithLatency(m.Latency, ctx, func() error {
items := []*resource.Item{}
// Apply filter
for _, id := range m.ids {
item, _, err := m.fetch(id)
if err != nil {
return err
}
if !lookup.Filter().Match(item.Payload) {
continue
}
items = append(items, item)
}
// Apply sort
if len(lookup.Sort()) > 0 {
s := sortableItems{lookup.Sort(), items}
sort.Sort(s)
}
// Apply pagination
total := len(items)
start := (page - 1) * perPage
end := total
if perPage > 0 {
end = start + perPage
if start > total-1 {
start = 0
end = 0
} else if end > total-1 {
end = total
}
}
list = &resource.ItemList{total, page, items[start:end]}
return nil
})
return list, err
}