Use better caching mechanism for mtr schedules

utils/cache.go

@@ -9,6 +9,73 @@ import (
     "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
+        }
+    }
+
+    return &cs, err
+}
+
 
 func CacheStream( path string, readStream func() ( io.ReadCloser, error ), expires time.Duration ) ( *bytes.Buffer, error ) {