X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/237adbd91e2dc0d15f79390f7e38f70d55372877..127e916894bcd16f6978aa6488c81e79a9ca2812:/sdk/go/keepclient/block_cache.go

diff --git a/sdk/go/keepclient/block_cache.go b/sdk/go/keepclient/block_cache.go
index 5d8daad60d..539975e161 100644
--- a/sdk/go/keepclient/block_cache.go
+++ b/sdk/go/keepclient/block_cache.go
@@ -18,9 +18,8 @@ type BlockCache struct {
 	// default size (currently 4) is used instead.
 	MaxBlocks int
 
-	cache     map[string]*cacheBlock
-	mtx       sync.Mutex
-	setupOnce sync.Once
+	cache map[string]*cacheBlock
+	mtx   sync.Mutex
 }
 
 const defaultMaxBlocks = 4
@@ -50,12 +49,27 @@ func (c *BlockCache) Sweep() {
 	}
 }
 
+// ReadAt returns data from the cache, first retrieving it from Keep if
+// necessary.
+func (c *BlockCache) ReadAt(kc *KeepClient, locator string, p []byte, off int) (int, error) {
+	buf, err := c.Get(kc, locator)
+	if err != nil {
+		return 0, err
+	}
+	if off > len(buf) {
+		return 0, io.ErrUnexpectedEOF
+	}
+	return copy(p, buf[off:]), nil
+}
+
 // Get returns data from the cache, first retrieving it from Keep if
 // necessary.
 func (c *BlockCache) Get(kc *KeepClient, locator string) ([]byte, error) {
-	c.setupOnce.Do(c.setup)
 	cacheKey := locator[:32]
 	c.mtx.Lock()
+	if c.cache == nil {
+		c.cache = make(map[string]*cacheBlock)
+	}
 	b, ok := c.cache[cacheKey]
 	if !ok || b.err != nil {
 		b = &cacheBlock{
@@ -93,16 +107,12 @@ func (c *BlockCache) Get(kc *KeepClient, locator string) ([]byte, error) {
 	return b.data, b.err
 }
 
-func (c *BlockCache) setup() {
+func (c *BlockCache) Clear() {
 	c.mtx.Lock()
-	c.cache = make(map[string]*cacheBlock)
+	c.cache = nil
 	c.mtx.Unlock()
 }
 
-func (c *BlockCache) Clear() {
-	c.setup()
-}
-
 type timeSlice []time.Time
 
 func (ts timeSlice) Len() int { return len(ts) }