Merge pull request #641 from josharian/cleanup

Minor cleanup and bug fixes

db.go

@@ -552,7 +552,10 @@ func (db *DB) removeTx(tx *Tx) {
 	// Remove the transaction.
 	for i, t := range db.txs {
 		if t == tx {
-			db.txs = append(db.txs[:i], db.txs[i+1:]...)
+			last := len(db.txs) - 1
+			db.txs[i] = db.txs[last]
+			db.txs[last] = nil
+			db.txs = db.txs[:last]
 			break
 		}
 	}

freelist.go

@@ -24,7 +24,12 @@ func newFreelist() *freelist {
 
 // size returns the size of the page after serialization.
 func (f *freelist) size() int {
-	return pageHeaderSize + (int(unsafe.Sizeof(pgid(0))) * f.count())
+	n := f.count()
+	if n >= 0xFFFF {
+		// The first element will be used to store the count. See freelist.write.
+		n++
+	}
+	return pageHeaderSize + (int(unsafe.Sizeof(pgid(0))) * n)
 }
 
 // count returns count of pages on the freelist
@@ -46,19 +51,10 @@ func (f *freelist) pending_count() int {
 	return count
 }
 
-// lenall returns the combined number of all free ids and all pending ids.
-func (f *freelist) lenall() int {
-	n := len(f.ids)
-	for _, list := range f.pending {
-		n += len(list)
-	}
-	return n
-}
-
-// all copies into dst a list of all free ids and all pending ids in one sorted list.
-// f.lenall returns the minimum length required for dst.
+// copyall copies into dst a list of all free ids and all pending ids in one sorted list.
+// f.count returns the minimum length required for dst.
 func (f *freelist) copyall(dst []pgid) {
-	m := make(pgids, 0, len(f.pending)) // len(f.pending) undercounts, but it is a start
+	m := make(pgids, 0, f.pending_count())
 	for _, list := range f.pending {
 		m = append(m, list...)
 	}
@@ -200,7 +196,7 @@ func (f *freelist) write(p *page) error {
 
 	// The page.count can only hold up to 64k elements so if we overflow that
 	// number then we handle it by putting the size in the first element.
-	lenids := f.lenall()
+	lenids := f.count()
 	if lenids == 0 {
 		p.count = uint16(lenids)
 	} else if lenids < 0xFFFF {

page.go

@@ -154,7 +154,7 @@ func (a pgids) merge(b pgids) pgids {
 	return merged
 }
 
-// merge copies the sorted union of a and b into dst.
+// mergepgids copies the sorted union of a and b into dst.
 // If dst is too small, it panics.
 func mergepgids(dst, a, b pgids) {
 	if len(dst) < len(a)+len(b) {

tx.go

@@ -381,7 +381,7 @@ func (tx *Tx) Check() <-chan error {
 func (tx *Tx) check(ch chan error) {
 	// Check if any pages are double freed.
 	freed := make(map[pgid]bool)
-	all := make([]pgid, tx.db.freelist.lenall())
+	all := make([]pgid, tx.db.freelist.count())
 	tx.db.freelist.copyall(all)
 	for _, id := range all {
 		if freed[id] {