From: rkinyon <rkinyon@50811bd7-b8ce-0310-adc1-d9db26280581>
Date: Tue, 30 Jan 2007 04:36:02 +0000 (+0000)
Subject: Transactional staleness counters are down from 4 bytes to 2
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=ac6daed3ba8f98fec100f622f993e146bdad6995;p=dbsrgits%2FDBM-Deep.git

Transactional staleness counters are down from 4 bytes to 2
---

diff --git a/lib/DBM/Deep/Engine.pm b/lib/DBM/Deep/Engine.pm
index 13f29fa..4f4e286 100644
--- a/lib/DBM/Deep/Engine.pm
+++ b/lib/DBM/Deep/Engine.pm
@@ -26,7 +26,8 @@ sub SIG_INDEX    () { 'I'    }
 sub SIG_BLIST    () { 'B'    }
 sub SIG_FREE     () { 'F'    }
 sub SIG_SIZE     () {  1     }
-sub STALE_SIZE   () {  1     }
+
+my $STALE_SIZE = 2;
 
 # Please refer to the pack() documentation for further information
 my %StP = (
@@ -390,7 +391,7 @@ sub rollback {
           + $self->hash_size
           + $self->byte_size
           + $self->byte_size
-          + ($self->trans_id - 1) * ( $self->byte_size + 4 );
+          + ($self->trans_id - 1) * ( $self->byte_size + $STALE_SIZE );
 
         my $data_loc = $self->storage->read_at( $read_loc, $self->byte_size );
         $data_loc = unpack( $StP{$self->byte_size}, $data_loc );
@@ -429,7 +430,7 @@ sub commit {
         my $head_loc = $self->storage->read_at( $base, $self->byte_size );
         $head_loc = unpack( $StP{$self->byte_size}, $head_loc );
 
-        my $spot = $base + $self->byte_size + ($self->trans_id - 1) * ( $self->byte_size + 4 );
+        my $spot = $base + $self->byte_size + ($self->trans_id - 1) * ( $self->byte_size + $STALE_SIZE );
         my $trans_loc = $self->storage->read_at(
             $spot, $self->byte_size,
         );
@@ -437,7 +438,7 @@ sub commit {
         $self->storage->print_at( $base, $trans_loc );
         $self->storage->print_at(
             $spot,
-            pack( $StP{$self->byte_size} . ' N', (0) x 2 ),
+            pack( $StP{$self->byte_size} . ' ' . $StP{$STALE_SIZE}, (0) x 2 ),
         );
 
         if ( $head_loc > 1 ) {
@@ -485,9 +486,9 @@ sub get_txn_staleness_counter {
     # Hardcode staleness of 0 for the HEAD
     return 0 unless $trans_id;
 
-    return unpack( 'N',
+    return unpack( $StP{$STALE_SIZE},
         $self->storage->read_at(
-            $self->trans_loc + 4 + 4 * ($trans_id - 1),
+            $self->trans_loc + 4 + $STALE_SIZE * ($trans_id - 1),
             4,
         )
     );
@@ -501,8 +502,8 @@ sub inc_txn_staleness_counter {
     return unless $trans_id;
 
     $self->storage->print_at(
-        $self->trans_loc + 4 + 4 * ($trans_id - 1),
-        pack( 'N', $self->get_txn_staleness_counter( $trans_id ) + 1 ),
+        $self->trans_loc + 4 + $STALE_SIZE * ($trans_id - 1),
+        pack( $StP{$STALE_SIZE}, $self->get_txn_staleness_counter( $trans_id ) + 1 ),
     );
 }
 
@@ -553,7 +554,7 @@ sub clear_entries {
 
         my $nt = $self->num_txns;
 
-        my $header_var = 1 + 1 + 1 + 1 + 4 + 4 * ($nt - 1) + 3 * $self->byte_size;
+        my $header_var = 1 + 1 + 1 + 1 + 4 + $STALE_SIZE * ($nt - 1) + 3 * $self->byte_size;
 
         my $loc = $self->storage->request_space( $header_fixed + $header_var );
 
@@ -572,7 +573,7 @@ sub clear_entries {
             pack('C', $nt),
 #XXX This is a problem - it limits everything to 32 transactions
             pack('N', 0 ),                   # Transaction activeness bitfield
-            pack('N' . ($nt-1), 0 x ($nt-1) ),       # Transaction staleness counters
+            pack($StP{$STALE_SIZE}.($nt-1), 0 x ($nt-1) ), # Transaction staleness counters
             pack($StP{$self->byte_size}, 0), # Start of free chain (blist size)
             pack($StP{$self->byte_size}, 0), # Start of free chain (data size)
             pack($StP{$self->byte_size}, 0), # Start of free chain (index size)
@@ -580,7 +581,7 @@ sub clear_entries {
 
         #XXX Set these less fragilely
         $self->set_trans_loc( $header_fixed + 4 );
-        $self->set_chains_loc( $header_fixed + 4 + 4 + 4 * ($nt-1) );
+        $self->set_chains_loc( $header_fixed + 4 + 4 + $STALE_SIZE * ($nt-1) );
 
         return;
     }
@@ -628,14 +629,14 @@ sub clear_entries {
         $self->{max_buckets} += 1;
         $self->{data_sector_size} += 1;
 
-        my $header_var = scalar(@values) + 4 + 4 * ($self->num_txns - 1) + 3 * $self->byte_size;
+        my $header_var = scalar(@values) + 4 + $STALE_SIZE * ($self->num_txns - 1) + 3 * $self->byte_size;
         unless ( $size == $header_var ) {
             $self->storage->close;
             DBM::Deep->_throw_error( "Unexpected size found ($size <-> $header_var)." );
         }
 
         $self->set_trans_loc( $header_fixed + scalar(@values) );
-        $self->set_chains_loc( $header_fixed + scalar(@values) + 4 + 4 * ($self->num_txns - 1) );
+        $self->set_chains_loc( $header_fixed + scalar(@values) + 4 + $STALE_SIZE * ($self->num_txns - 1) );
 
         return length($buffer) + length($buffer2);
     }
@@ -714,9 +715,9 @@ sub _add_free_sector {
 
     # Increment staleness.
     # XXX Can this increment+modulo be done by "&= 0x1" ?
-    my $staleness = unpack( $StP{STALE_SIZE()}, $storage->read_at( $offset + SIG_SIZE, STALE_SIZE ) );
-    $staleness = ($staleness + 1 ) % ( 2 ** ( 8 * STALE_SIZE ) );
-    $storage->print_at( $offset + SIG_SIZE, pack( $StP{STALE_SIZE()}, $staleness ) );
+    my $staleness = unpack( $StP{$STALE_SIZE}, $storage->read_at( $offset + SIG_SIZE, $STALE_SIZE ) );
+    $staleness = ($staleness + 1 ) % ( 2 ** ( 8 * $STALE_SIZE ) );
+    $storage->print_at( $offset + SIG_SIZE, pack( $StP{$STALE_SIZE}, $staleness ) );
 
     my $old_head = $storage->read_at( $self->chains_loc + $chains_offset, $self->byte_size );
 
@@ -725,7 +726,7 @@ sub _add_free_sector {
     );
 
     # Record the old head in the new sector after the signature and staleness counter
-    $storage->print_at( $offset + SIG_SIZE + STALE_SIZE, $old_head );
+    $storage->print_at( $offset + SIG_SIZE + $STALE_SIZE, $old_head );
 }
 
 sub _request_blist_sector { shift->_request_sector( 0, @_ ) }
@@ -753,10 +754,10 @@ sub _request_sector {
     }
 
     # Read the new head after the signature and the staleness counter
-    my $new_head = $self->storage->read_at( $loc + SIG_SIZE + STALE_SIZE, $self->byte_size );
+    my $new_head = $self->storage->read_at( $loc + SIG_SIZE + $STALE_SIZE, $self->byte_size );
     $self->storage->print_at( $self->chains_loc + $chains_offset, $new_head );
     $self->storage->print_at(
-        $loc + SIG_SIZE + STALE_SIZE,
+        $loc + SIG_SIZE + $STALE_SIZE,
         pack( $StP{$self->byte_size}, 0 ),
     );
 
@@ -966,7 +967,7 @@ sub type   { $_[0]{type} }
 
 sub base_size {
    my $self = shift;
-   return $self->engine->SIG_SIZE + $self->engine->STALE_SIZE;
+   return $self->engine->SIG_SIZE + $STALE_SIZE;
 }
 
 sub free {
@@ -1179,8 +1180,8 @@ sub _init {
     }
 
     $self->{staleness} = unpack(
-        $StP{$e->STALE_SIZE},
-        $e->storage->read_at( $self->offset + $e->SIG_SIZE, $e->STALE_SIZE ),
+        $StP{$STALE_SIZE},
+        $e->storage->read_at( $self->offset + $e->SIG_SIZE, $STALE_SIZE ),
     );
 
     return;
@@ -1561,9 +1562,8 @@ sub bucket_size {
     my $self = shift;
     unless ( $self->{bucket_size} ) {
         my $e = $self->engine;
-        #XXX Convert the 4 to STALE_SIZE()
         # Key + head (location) + transactions (location + staleness-counter)
-        my $location_size = $e->byte_size + $e->byte_size + ($e->num_txns - 1) * ($e->byte_size + 4);
+        my $location_size = $e->byte_size + $e->byte_size + ($e->num_txns - 1) * ($e->byte_size + $STALE_SIZE);
         $self->{bucket_size} = $e->hash_size + $location_size;
     }
     return $self->{bucket_size};
@@ -1678,13 +1678,12 @@ sub write_md5 {
       + $engine->hash_size
       + $engine->byte_size;
 
-    #XXX Convert the 4 to STALE_SIZE()
     if ( $args->{trans_id} ) {
-        $loc += $engine->byte_size + ($args->{trans_id} - 1) * ( $engine->byte_size + 4 );
+        $loc += $engine->byte_size + ($args->{trans_id} - 1) * ( $engine->byte_size + $STALE_SIZE );
 
         $engine->storage->print_at( $loc,
             pack( $StP{$engine->byte_size}, $args->{value}->offset ),
-            pack( 'N', $engine->get_txn_staleness_counter( $args->{trans_id} ) ),
+            pack( $StP{$STALE_SIZE}, $engine->get_txn_staleness_counter( $args->{trans_id} ) ),
         );
     }
     else {
@@ -1710,13 +1709,12 @@ sub mark_deleted {
       + $engine->hash_size
       + $engine->byte_size;
 
-    #XXX Convert the 4 to STALE_SIZE()
     if ( $args->{trans_id} ) {
-        $loc += $engine->byte_size + ($args->{trans_id} - 1) * ( $engine->byte_size + 4 );
+        $loc += $engine->byte_size + ($args->{trans_id} - 1) * ( $engine->byte_size + $STALE_SIZE );
 
         $engine->storage->print_at( $loc,
             pack( $StP{$engine->byte_size}, 1 ), # 1 is the marker for deleted
-            pack( 'N', $engine->get_txn_staleness_counter( $args->{trans_id} ) ),
+            pack( $StP{$STALE_SIZE}, $engine->get_txn_staleness_counter( $args->{trans_id} ) ),
         );
     }
     else {
@@ -1774,24 +1772,22 @@ sub get_data_location_for {
       + $e->hash_size
       + $e->byte_size;
 
-    #XXX Convert the 4 to STALE_SIZE()
     if ( $args->{trans_id} ) {
-        $spot += $e->byte_size + ($args->{trans_id} - 1) * ( $e->byte_size + 4 );
+        $spot += $e->byte_size + ($args->{trans_id} - 1) * ( $e->byte_size + $STALE_SIZE );
     }
 
-    #XXX Convert the 4 to STALE_SIZE()
     my $buffer = $e->storage->read_at(
         $spot,
-        $e->byte_size + 4,
+        $e->byte_size + $STALE_SIZE,
     );
-    my ($loc, $staleness) = unpack( $StP{$e->byte_size} . ' N', $buffer );
+    my ($loc, $staleness) = unpack( $StP{$e->byte_size} . ' ' . $StP{$STALE_SIZE}, $buffer );
 
     if ( $args->{trans_id} ) {
         # We have found an entry that is old, so get rid of it
         if ( $staleness != (my $s = $e->get_txn_staleness_counter( $args->{trans_id} ) ) ) {
             $e->storage->print_at(
                 $spot,
-                pack( $StP{$e->byte_size} . ' N', (0) x 2 ), 
+                pack( $StP{$e->byte_size} . ' ' . $StP{$STALE_SIZE}, (0) x 2 ), 
             );
             $loc = 0;
         }