1 files changed, 40 insertions, 1 deletions
diff --git a/freelist.go b/freelist.go
index a236079..e27f80a 100644
--- a/freelist.go
+++ b/freelist.go
@@ -1,11 +1,18 @@
 package bolt
 
 import (
+	"errors"
 	"fmt"
 	"sort"
 	"unsafe"
 )
 
+var (
+	// ErrFreelistOverflow is returned when the total number of free pages
+	// exceeds 65,536 and the freelist cannot hold any more.
+	ErrFreelistOverflow = errors.New("freelist overflow")
+)
+
 // freelist represents a list of all pages that are available for allocation.
 // It also tracks pages that have been freed but are still in use by open transactions.
 type freelist struct {
@@ -106,6 +113,11 @@ func (f *freelist) release(txid txid) {
 	sort.Sort(pgids(f.ids))
 }
 
+// rollback removes the pages from a given pending tx.
+func (f *freelist) rollback(txid txid) {
+	delete(f.pending, txid)
+}
+
 // isFree returns whether a given page is in the free list.
 func (f *freelist) isFree(pgid pgid) bool {
 	for _, id := range f.ids {
@@ -134,9 +146,36 @@ func (f *freelist) read(p *page) {
 // write writes the page ids onto a freelist page. All free and pending ids are
 // saved to disk since in the event of a program crash, all pending ids will
 // become free.
-func (f *freelist) write(p *page) {
+func (f *freelist) write(p *page) error {
+	// Combine the old free pgids and pgids waiting on an open transaction.
 	ids := f.all()
+
+	// Make sure that the sum of all free pages is less than the max uint16 size.
+	if len(ids) >= 65565 {
+		return ErrFreelistOverflow
+	}
+
+	// Update the header and write the ids to the page.
 	p.flags |= freelistPageFlag
 	p.count = uint16(len(ids))
 	copy(((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[:], ids)
+
+	return nil
+}
+
+// reload reads the freelist from a page and filters out pending items.
+func (f *freelist) reload(p *page) {
+	f.read(p)
+
+	// Filter out pending free pages.
+	ids := f.ids
+	f.ids = nil
+
+	var a []pgid
+	for _, id := range ids {
+		if !f.isFree(id) {
+			a = append(a, id)
+		}
+	}
+	f.ids = a
 }