222 lines
5.7 KiB
Go
222 lines
5.7 KiB
Go
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// Code generated by github.com/vektah/dataloaden, DO NOT EDIT.
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package dataloader
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import (
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"sync"
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"time"
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"github.com/barasher/go-exiftool"
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)
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// ExiftoolLoaderConfig captures the config to create a new ExiftoolLoader
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type ExiftoolLoaderConfig struct {
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// Fetch is a method that provides the data for the loader
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Fetch func(keys []string) ([]exiftool.FileMetadata, []error)
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// Wait is how long wait before sending a batch
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Wait time.Duration
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// MaxBatch will limit the maximum number of keys to send in one batch, 0 = not limit
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MaxBatch int
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}
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// NewExiftoolLoader creates a new ExiftoolLoader given a fetch, wait, and maxBatch
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// func NewExiftoolLoader(config ExiftoolLoaderConfig) *ExiftoolLoader {
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// return &ExiftoolLoader{
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// fetch: config.Fetch,
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// wait: config.Wait,
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// maxBatch: config.MaxBatch,
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// }
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// }
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// ExiftoolLoader batches and caches requests
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type ExiftoolLoader struct {
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// this method provides the data for the loader
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fetch func(keys []string) ([]exiftool.FileMetadata, []error)
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// how long to done before sending a batch
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wait time.Duration
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// this will limit the maximum number of keys to send in one batch, 0 = no limit
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maxBatch int
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// INTERNAL
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// lazily created cache
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cache map[string]exiftool.FileMetadata
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// the current batch. keys will continue to be collected until timeout is hit,
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// then everything will be sent to the fetch method and out to the listeners
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batch *exiftoolLoaderBatch
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// mutex to prevent races
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mu sync.Mutex
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}
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type exiftoolLoaderBatch struct {
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keys []string
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data []exiftool.FileMetadata
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error []error
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closing bool
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done chan struct{}
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}
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// Load a exiftool.FileMetadata by key, batching and caching will be applied automatically
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func (l *ExiftoolLoader) Load(key string) (exiftool.FileMetadata, error) {
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return l.LoadThunk(key)()
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}
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// LoadThunk returns a function that when called will block waiting for a exiftool.FileMetadata.
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// This method should be used if you want one goroutine to make requests to many
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// different data loaders without blocking until the thunk is called.
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func (l *ExiftoolLoader) LoadThunk(key string) func() (exiftool.FileMetadata, error) {
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l.mu.Lock()
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if it, ok := l.cache[key]; ok {
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l.mu.Unlock()
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return func() (exiftool.FileMetadata, error) {
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return it, nil
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}
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}
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if l.batch == nil {
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l.batch = &exiftoolLoaderBatch{done: make(chan struct{})}
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}
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batch := l.batch
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pos := batch.keyIndex(l, key)
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l.mu.Unlock()
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return func() (exiftool.FileMetadata, error) {
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<-batch.done
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var data exiftool.FileMetadata
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if pos < len(batch.data) {
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data = batch.data[pos]
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}
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var err error
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// its convenient to be able to return a single error for everything
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if len(batch.error) == 1 {
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err = batch.error[0]
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} else if batch.error != nil {
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err = batch.error[pos]
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}
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if err == nil {
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l.mu.Lock()
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l.unsafeSet(key, data)
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l.mu.Unlock()
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}
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return data, err
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}
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}
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// LoadAll fetches many keys at once. It will be broken into appropriate sized
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// sub batches depending on how the loader is configured
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func (l *ExiftoolLoader) LoadAll(keys []string) ([]exiftool.FileMetadata, []error) {
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results := make([]func() (exiftool.FileMetadata, error), len(keys))
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for i, key := range keys {
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results[i] = l.LoadThunk(key)
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}
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FileMetadatas := make([]exiftool.FileMetadata, len(keys))
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errors := make([]error, len(keys))
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for i, thunk := range results {
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FileMetadatas[i], errors[i] = thunk()
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}
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return FileMetadatas, errors
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}
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// LoadAllThunk returns a function that when called will block waiting for a FileMetadatas.
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// This method should be used if you want one goroutine to make requests to many
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// different data loaders without blocking until the thunk is called.
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func (l *ExiftoolLoader) LoadAllThunk(keys []string) func() ([]exiftool.FileMetadata, []error) {
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results := make([]func() (exiftool.FileMetadata, error), len(keys))
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for i, key := range keys {
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results[i] = l.LoadThunk(key)
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}
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return func() ([]exiftool.FileMetadata, []error) {
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FileMetadatas := make([]exiftool.FileMetadata, len(keys))
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errors := make([]error, len(keys))
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for i, thunk := range results {
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FileMetadatas[i], errors[i] = thunk()
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}
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return FileMetadatas, errors
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}
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}
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// Prime the cache with the provided key and value. If the key already exists, no change is made
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// and false is returned.
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// (To forcefully prime the cache, clear the key first with loader.clear(key).prime(key, value).)
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func (l *ExiftoolLoader) Prime(key string, value exiftool.FileMetadata) bool {
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l.mu.Lock()
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var found bool
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if _, found = l.cache[key]; !found {
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l.unsafeSet(key, value)
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}
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l.mu.Unlock()
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return !found
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}
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// Clear the value at key from the cache, if it exists
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func (l *ExiftoolLoader) Clear(key string) {
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l.mu.Lock()
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delete(l.cache, key)
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l.mu.Unlock()
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}
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func (l *ExiftoolLoader) unsafeSet(key string, value exiftool.FileMetadata) {
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if l.cache == nil {
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l.cache = map[string]exiftool.FileMetadata{}
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}
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l.cache[key] = value
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}
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// keyIndex will return the location of the key in the batch, if its not found
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// it will add the key to the batch
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func (b *exiftoolLoaderBatch) keyIndex(l *ExiftoolLoader, key string) int {
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for i, existingKey := range b.keys {
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if key == existingKey {
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return i
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}
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}
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pos := len(b.keys)
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b.keys = append(b.keys, key)
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if pos == 0 {
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go b.startTimer(l)
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}
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if l.maxBatch != 0 && pos >= l.maxBatch-1 {
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if !b.closing {
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b.closing = true
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l.batch = nil
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go b.end(l)
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}
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}
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return pos
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}
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func (b *exiftoolLoaderBatch) startTimer(l *ExiftoolLoader) {
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time.Sleep(l.wait)
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l.mu.Lock()
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// we must have hit a batch limit and are already finalizing this batch
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if b.closing {
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l.mu.Unlock()
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return
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}
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l.batch = nil
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l.mu.Unlock()
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b.end(l)
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}
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func (b *exiftoolLoaderBatch) end(l *ExiftoolLoader) {
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b.data, b.error = l.fetch(b.keys)
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close(b.done)
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}
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