golifehk/utils/cache.go

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package utils
import (
"bytes"
"io"
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"log"
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"os"
"path/filepath"
"time"
)
type CacheStreams struct {
Local *bytes.Buffer
Remote *bytes.Buffer
Path string
Query func() ( io.ReadCloser, error )
}
func ( cs *CacheStreams ) Commit() error {
f, err := os.OpenFile( cs.Path, os.O_CREATE | os.O_WRONLY | os.O_TRUNC, 0644 )
if err != nil {
return err
}
defer f.Close()
_, err = io.Copy( f, bytes.NewReader( cs.Remote.Bytes() ) )
log.Printf( "Commit: %s", cs.Path )
return err
}
func ( cs *CacheStreams ) Reload() error {
s, err := cs.Query()
if err != nil {
return err
}
defer s.Close()
cs.Remote = bytes.NewBuffer( []byte{} )
_, err = io.Copy( cs.Remote, s )
return err
}
func ( cs *CacheStreams ) NotExpired( expires time.Duration ) bool {
cache, err := os.Stat( cs.Path )
if err == nil {
expired := cache.ModTime().Add( expires * 1e9 )
return time.Now().Before( expired )
}
return false
}
func CacheStreamEx( path string, readStream func() ( io.ReadCloser, error ) ) ( *CacheStreams, error ) {
cs := CacheStreams{}
cs.Path = path
cs.Query = readStream
f, err := os.Open( path )
if err == nil {
defer f.Close()
cs.Local = bytes.NewBuffer( []byte{} )
_, err = io.Copy( cs.Local, f )
if err != nil {
return nil, err
}
}
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return &cs, nil
}
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func CacheStream( path string, readStream func() ( io.ReadCloser, error ), expires time.Duration ) ( *bytes.Buffer, error ) {
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cache, err := os.Stat( path )
// Check if cache exists and not expired
if err == nil {
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expired := cache.ModTime().Add( expires * 1e9 )
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if time.Now().Before( expired ) {
f, err := os.Open( path )
if err == nil {
defer f.Close()
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log.Printf( "Using cache: %s", path )
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writeBuff := bytes.NewBuffer( []byte{} )
_, err = io.Copy( writeBuff, f )
if err == nil {
return writeBuff, nil
}
}
}
}
err = os.MkdirAll( filepath.Dir( path ), 0750 )
if err != nil {
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return nil, err }
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writeBuff := bytes.NewBuffer( []byte{} )
// Get the reader that return new data
s, err := readStream()
if err != nil {
return nil, err
}
defer s.Close()
_, err = io.Copy( writeBuff, s )
if err != nil {
return nil, err
}
f, err := os.OpenFile( path, os.O_CREATE | os.O_WRONLY | os.O_TRUNC, 0644 )
if err != nil {
return nil, err
}
defer f.Close()
data := writeBuff.Bytes()
_, err = io.Copy( f, bytes.NewReader( data ) )
if err != nil {
return nil, err
}
return writeBuff, nil
}
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func ChangedStream( path string, readStream func() ( io.Reader, error ), dataModTime time.Time ) ( *bytes.Buffer, error ) {
cache, err := os.Stat( path )
// Check if cache exists and not expired
if err == nil {
if dataModTime.Before( cache.ModTime() ) {
f, err := os.Open( path )
if err == nil {
defer f.Close()
log.Printf( "Reading from file: %s", path )
writeBuff := bytes.NewBuffer( []byte{} )
_, err = io.Copy( writeBuff, f )
if err == nil {
return writeBuff, nil
}
}
}
}
err = os.MkdirAll( filepath.Dir( path ), 0750 )
if err != nil {
return nil, err
}
writeBuff := bytes.NewBuffer( []byte{} )
// Get the reader that return new data
s, err := readStream()
if err != nil {
return nil, err
}
_, err = io.Copy( writeBuff, s )
if err != nil {
return nil, err
}
f, err := os.OpenFile( path, os.O_CREATE | os.O_WRONLY | os.O_TRUNC, 0644 )
if err != nil {
return nil, err
}
defer f.Close()
data := writeBuff.Bytes()
_, err = io.Copy( f, bytes.NewReader( data ) )
if err != nil {
return nil, err
}
return writeBuff, nil
}