Provide context to readahead func

diff --git a/reader.go b/reader.go
index c8af14640bb813e98eabeca5305aa02532ffaba1..a8264ed1d637250db21705180757ec3e4e4ffbdc 100644 (file)
--- a/reader.go
+++ b/reader.go
@@ -22,7 +22,7 @@ type Reader interface {
        // If non-nil, the provided function is called when the implementation needs to know the
        // readahead for the current reader. Calls occur during Reads and Seeks, and while the Client is
        // locked.
-       SetReadaheadFunc(func() int64)
+       SetReadaheadFunc(ReadaheadFunc)
        // Don't wait for pieces to complete and be verified. Read calls return as soon as they can when
        // the underlying chunks become available.
        SetResponsive()
@@ -33,13 +33,21 @@ type pieceRange struct {
        begin, end pieceIndex
 }
 
+type ReadaheadContext struct {
+       ContiguousReadStartPos int64
+       CurrentPos             int64
+}
+
+// Returns the desired readahead for a Reader.
+type ReadaheadFunc func(ReadaheadContext) int64
+
 type reader struct {
        t *Torrent
        // Adjust the read/seek window to handle Readers locked to File extents and the like.
        offset, length int64
 
        // Function to dynamically calculate readahead. If nil, readahead is static.
-       readaheadFunc func() int64
+       readaheadFunc ReadaheadFunc
 
        // Required when modifying pos and readahead.
        mu sync.Locker
@@ -79,7 +87,7 @@ func (r *reader) SetReadahead(readahead int64) {
        r.mu.Unlock()
 }
 
-func (r *reader) SetReadaheadFunc(f func() int64) {
+func (r *reader) SetReadaheadFunc(f ReadaheadFunc) {
        r.mu.Lock()
        r.readaheadFunc = f
        r.posChanged()
@@ -116,7 +124,10 @@ func (r *reader) available(off, max int64) (ret int64) {
 func (r *reader) piecesUncached() (ret pieceRange) {
        ra := r.readahead
        if r.readaheadFunc != nil {
-               ra = r.readaheadFunc()
+               ra = r.readaheadFunc(ReadaheadContext{
+                       ContiguousReadStartPos: r.contiguousReadStartPos,
+                       CurrentPos:             r.pos,
+               })
        }
        if ra < 1 {
                // Needs to be at least 1, because [x, x) means we don't want
@@ -303,6 +314,6 @@ func (r *reader) log(m log.Msg) {
 }
 
 // Implementation inspired by https://news.ycombinator.com/item?id=27019613.
-func (r *reader) defaultReadaheadFunc() int64 {
-       return r.pos - r.contiguousReadStartPos
+func defaultReadaheadFunc(r ReadaheadContext) int64 {
+       return r.CurrentPos - r.ContiguousReadStartPos
 }

diff --git a/t.go b/t.go
index 580a3bc91c9cf789156431c9a24f405e8d77da90..d861e14e979cf85eb65faafc2ba7eca4e7878da8 100644 (file)
--- a/t.go
+++ b/t.go
@@ -42,7 +42,7 @@ func (t *Torrent) newReader(offset, length int64) Reader {
                offset: offset,
                length: length,
        }
-       r.readaheadFunc = r.defaultReadaheadFunc
+       r.readaheadFunc = defaultReadaheadFunc
        t.addReader(&r)
        return &r
 }