Add reference counting so we can delete unused chunks

1 files changed, 44 insertions, 14 deletions

diff --git a/FuseArchive/Storage/FileSystem.py b/FuseArchive/Storage/FileSystem.py
index a6687b5..04c6bb9 100644
--- a/FuseArchive/Storage/FileSystem.py
+++ b/FuseArchive/Storage/FileSystem.py
@@ -4,6 +4,47 @@ from FuseArchive.Chunk import Chunk
 
 magic_depth = 5
 
+def inc_chunk( key, count ):
+    # Increment this chunk header reference
+    path = _key_to_path( key )
+    logging.debug( "Updating header on %s, ref count + %d" % ( path, count ) )
+    f = open( path, "r+" )
+    data = f.read( Chunk.header_length() )
+    newcount, data = Chunk.inc_header_ref( data, count )
+    f.seek( 0 )
+    f.write( data )
+    f.close()
+    logging.debug( "Count is now: %d" % newcount )
+
+    assert newcount >= 0, "Count is negative?!!"
+
+    if newcount == 0:
+        logging.debug( "Freeing chunk" )
+        os.unlink( path )
+
+def lock_chunk( key ):
+    inc_chunk( key, 1 )
+
+def unlock_chunk( key ):
+    inc_chunk( key, -1 )
+
+def _key_to_path( key ):
+    logging.debug( "Converting key to path" )
+    ( thash, seq ) = key
+    chars = list( thash )
+    logging.debug( chars )
+
+    # Todo: make a digest -> path function to share with deflate
+    hexdigest = ''.join( [ "%02x" % ord( x ) for x in chars ] )
+    logging.debug( "Hash is: %s sub %d" % ( hexdigest, seq ) )
+    subparts = [ "%02x" % ord( x ) for x in chars[ :magic_depth ] ]
+    subpath = '/'.join( subparts )
+    logging.debug( "Subpath: " + subpath )
+
+    subpath += "/%s_%d" % ( hexdigest, seq )
+    return( "./storage/" + subpath )
+
+
 # This will write out a data block, it will return a key that can get this
 # data back later
 def save_chunk( chunk ):
@@ -77,26 +118,15 @@ def load_chunk( key ):
     if FuseArchive.magic_profiling:
         return ''
 
-    ( thash, seq ) = key
     logging.debug( "Begin load_chunk" )
 
-    chars = list( thash )
-    logging.debug( chars )
-
-    # Todo: make a digest -> path function to share with deflate
-    hexdigest = ''.join( [ "%02x" % ord( x ) for x in chars ] )
-    logging.debug( "Hash is: %s sub %d" % ( hexdigest, seq ) )
-    subparts = [ "%02x" % ord( x ) for x in chars[ :magic_depth ] ]
-    subpath = '/'.join( subparts )
-    logging.debug( "Subpath: " + subpath )
-
-    subpath += "/%s_%d" % ( hexdigest, seq )
+    subpath = _key_to_path( key )
 
     logging.debug( "Chunk path: " + subpath )
 
-    if os.path.exists( "./storage/" + subpath ):
+    if os.path.exists( subpath ):
         logging.debug( "Exporting chunk" )
-        readchunk = open( "./storage/" + subpath )
+        readchunk = open( subpath )
         chunk = Chunk.deserialize( readchunk.read() ).chunk
         readchunk.close()
     else: