Reorder fields to reduce padding in reader (#597)

Reorder some of the fields to reduce the size of `reader`. Not much of a change -- original size was 104 bytes, with changes (moving bool's to the end) the size is 96 bytes. There's also the whole cache-friendly bit -- I tried reordering fields to help here, but I doubt it makes much of a difference.

Some other notes: `sync.Locker` is a 16 byte field. I suggest changing this to something like `*sync.RWMutex` or `*lockWithDeferreds`. This would not only reduce size but would allow access to `RLock`/`RUnlock`.
`pieceRange` could also be shrunk to 8 bytes, but I feel like I'm probably asking for too much lol.

diff --git a/reader.go b/reader.go
index a5a865710f7256703fb3099652aca500e0b78d67..31ac7b07937f2c389af59f06bb895b61d4bef911 100644 (file)
--- a/reader.go
+++ b/reader.go
@@ -30,26 +30,29 @@ type pieceRange struct {
 }
 
 type reader struct {
-       t          *Torrent
-       responsive bool
+       t   *Torrent
        // Adjust the read/seek window to handle Readers locked to File extents and the like.
        offset, length int64
-
-       // Required when modifying pos and readahead, or reading them without opMu.
-       mu  sync.Locker
-       pos int64
-       // Reads have been initiated since the last seek. This is used to prevent readahead occuring
-       // after a seek or with a new reader at the starting position.
-       reading   bool
-       readahead int64
+       
        // Function to dynamically calculate readahead. If nil, readahead is static.
        readaheadFunc func() int64
+       
+       // Required when modifying pos and readahead.
+       mu  sync.Locker
+
+       readahead, pos int64
        // Position that reads have continued contiguously from.
        contiguousReadStartPos int64
        // The cached piece range this reader wants downloaded. The zero value corresponds to nothing.
        // We cache this so that changes can be detected, and bubbled up to the Torrent only as
        // required.
        pieces pieceRange
+
+       // Reads have been initiated since the last seek. This is used to prevent readaheads occurring
+       // after a seek or with a new reader at the starting position.
+       reading    bool
+       responsive bool
+
 }
 
 var _ io.ReadSeekCloser = (*reader)(nil)