X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/6ee6e654bc873db10037c735a63697d295ec40cb..8a27fe370239ecb8e50d53f46b45ed61203a35ca:/sdk/go/keepclient/block_cache.go

diff --git a/sdk/go/keepclient/block_cache.go b/sdk/go/keepclient/block_cache.go
index 18f7de99e5..bac4a24fd5 100644
--- a/sdk/go/keepclient/block_cache.go
+++ b/sdk/go/keepclient/block_cache.go
@@ -5,9 +5,10 @@
 package keepclient
 
 import (
-	"bytes"
 	"io"
 	"sort"
+	"strconv"
+	"strings"
 	"sync"
 	"time"
 )
@@ -19,9 +20,8 @@ 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
@@ -30,7 +30,7 @@ const defaultMaxBlocks = 4
 // there are no more than MaxBlocks left.
 func (c *BlockCache) Sweep() {
 	max := c.MaxBlocks
-	if max < defaultMaxBlocks {
+	if max == 0 {
 		max = defaultMaxBlocks
 	}
 	c.mtx.Lock()
@@ -51,12 +51,34 @@ 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]
+	bufsize := BLOCKSIZE
+	if parts := strings.SplitN(locator, "+", 3); len(parts) >= 2 {
+		datasize, err := strconv.ParseInt(parts[1], 10, 32)
+		if err == nil && datasize >= 0 {
+			bufsize = int(datasize)
+		}
+	}
 	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{
@@ -65,17 +87,18 @@ func (c *BlockCache) Get(kc *KeepClient, locator string) ([]byte, error) {
 		}
 		c.cache[cacheKey] = b
 		go func() {
-			rdr, _, _, err := kc.Get(locator)
-			data := bytes.NewBuffer(make([]byte, 0, BLOCKSIZE))
+			rdr, size, _, err := kc.Get(locator)
+			var data []byte
 			if err == nil {
-				_, err = io.Copy(data, rdr)
+				data = make([]byte, size, bufsize)
+				_, err = io.ReadFull(rdr, data)
 				err2 := rdr.Close()
 				if err == nil {
 					err = err2
 				}
 			}
 			c.mtx.Lock()
-			b.data, b.err = data.Bytes(), err
+			b.data, b.err = data, err
 			c.mtx.Unlock()
 			close(b.fetched)
 			go c.Sweep()
@@ -93,13 +116,9 @@ func (c *BlockCache) Get(kc *KeepClient, locator string) ([]byte, error) {
 	return b.data, b.err
 }
 
-func (c *BlockCache) setup() {
-	c.cache = make(map[string]*cacheBlock)
-}
-
 func (c *BlockCache) Clear() {
 	c.mtx.Lock()
-	c.setup()
+	c.cache = nil
 	c.mtx.Unlock()
 }