Fix 2.4.2 upgrade notes formatting refs #19330

[arvados.git] / sdk / go / keepclient / block_cache.go

diff --git a/sdk/go/keepclient/block_cache.go b/sdk/go/keepclient/block_cache.go
index 18f7de99e5f90855c13526c92eebc6c52743fa34..bac4a24fd5a037d9cdcafb663612677304184c97 100644 (file)
--- 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()
 }