88 lines
1.7 KiB
Go
88 lines
1.7 KiB
Go
package cache
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import (
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"errors"
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"io"
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"net/http"
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"os"
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"strconv"
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"sync"
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)
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// downloader attempts to download a file from a remote URL.
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type downloader struct {
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doneMutex sync.Mutex
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err error
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entry *Entry
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entryMutex sync.Mutex
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}
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// newDownloader creates a new downloader.
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func newDownloader(rawurl, jsonFilename, dataFilename string) *downloader {
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d := &downloader{}
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d.doneMutex.Lock()
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d.entryMutex.Lock()
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go func() {
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defer func() {
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d.doneMutex.Unlock()
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}()
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once := &sync.Once{}
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trigger := func() {
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once.Do(func() {
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d.entryMutex.Unlock()
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})
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}
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defer trigger()
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resp, err := http.Get(rawurl)
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if err != nil {
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d.err = err
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return
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}
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defer resp.Body.Close()
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if resp.StatusCode != 200 {
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d.err = errors.New(resp.Status)
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return
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}
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f, err := os.Create(dataFilename)
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if err != nil {
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d.err = err
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return
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}
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defer f.Close()
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d.entry = &Entry{
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URL: rawurl,
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ContentLength: strconv.FormatInt(resp.ContentLength, 10),
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ContentType: resp.Header.Get("Content-Type"),
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LastModified: resp.Header.Get("Last-Modified"),
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}
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if err = d.entry.Save(jsonFilename); err != nil {
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d.err = err
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return
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}
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trigger()
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n, err := io.Copy(f, resp.Body)
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if err != nil {
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d.err = err
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return
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}
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d.entry.ContentLength = strconv.FormatInt(n, 10)
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d.entry.Complete = true
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d.entry.Save(jsonFilename)
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}()
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return d
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}
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// GetEntry retrieves the entry associated with the download.
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func (d *downloader) GetEntry() (*Entry, error) {
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d.entryMutex.Lock()
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defer d.entryMutex.Unlock()
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return d.entry, d.err
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}
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// WaitForDone will block until the download completes.
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func (d *downloader) WaitForDone() error {
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d.doneMutex.Lock()
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defer d.doneMutex.Unlock()
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return d.err
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}
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