mirror of https://github.com/perkeep/perkeep.git
85 lines
2.1 KiB
Go
85 lines
2.1 KiB
Go
/*
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Copyright 2011 Google Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package server
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import (
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"errors"
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"fmt"
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"camlistore.org/pkg/blob"
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"camlistore.org/pkg/lru"
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"camlistore.org/pkg/sorted"
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)
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const memLRUSize = 1024 // arbitrary
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var errCacheMiss = errors.New("not in cache")
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// ThumbMeta is a mapping from an image's scaling parameters (encoding
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// as an opaque "key" string) and the blobref of the thumbnail
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// (currently its file schema blob).
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// ThumbMeta is safe for concurrent use by multiple goroutines.
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//
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// The key will be some string containing the original full-sized image's
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// blobref, its target dimensions, and any possible transformations on
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// it (e.g. cropping it to square).
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type ThumbMeta struct {
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mem *lru.Cache // key -> blob.Ref
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kv sorted.KeyValue // optional
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}
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// NewThumbMeta returns a new in-memory ThumbMeta, backed with the
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// optional kv.
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// If kv is nil, key/value pairs are stored in memory only.
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func NewThumbMeta(kv sorted.KeyValue) *ThumbMeta {
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return &ThumbMeta{
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mem: lru.New(memLRUSize),
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kv: kv,
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}
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}
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func (m *ThumbMeta) Get(key string) (blob.Ref, error) {
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var br blob.Ref
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if v, ok := m.mem.Get(key); ok {
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return v.(blob.Ref), nil
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}
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if m.kv != nil {
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v, err := m.kv.Get(key)
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if err == sorted.ErrNotFound {
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return br, errCacheMiss
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}
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if err != nil {
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return br, err
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}
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br, ok := blob.Parse(v)
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if !ok {
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return br, fmt.Errorf("Invalid blobref %q found for key %q in thumbnail mea", v, key)
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}
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m.mem.Add(key, br)
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return br, nil
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}
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return br, errCacheMiss
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}
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func (m *ThumbMeta) Put(key string, br blob.Ref) error {
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m.mem.Add(key, br)
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if m.kv != nil {
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return m.kv.Set(key, br.String())
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}
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return nil
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}
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