Fix freelist allocate().

db_test.go

@@ -319,10 +319,10 @@ func TestDB_Consistency(t *testing.T) {
 				assert.Equal(t, "free", p.Type)
 			}
 			if p, _ := tx.Page(4); assert.NotNil(t, p) {
-				assert.Equal(t, "freelist", p.Type)
+				assert.Equal(t, "leaf", p.Type) // root leaf
 			}
 			if p, _ := tx.Page(5); assert.NotNil(t, p) {
-				assert.Equal(t, "leaf", p.Type) // root leaf
+				assert.Equal(t, "freelist", p.Type)
 			}
 			p, _ := tx.Page(6)
 			assert.Nil(t, p)

freelist.go

@@ -55,7 +55,7 @@ func (f *freelist) allocate(n int) pgid {
 			if (i + 1) == n {
 				f.ids = f.ids[i+1:]
 			} else {
-				copy(f.ids[i-1:], f.ids[i+n-1:])
+				copy(f.ids[i-n+1:], f.ids[i+1:])
 				f.ids = f.ids[:len(f.ids)-n]
 			}
 			return initial
@@ -111,7 +111,7 @@ func (f *freelist) read(p *page) {
 	ids := ((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[0:p.count]
 	f.ids = make([]pgid, len(ids))
 	copy(f.ids, ids)
-	sort.Sort(pgids(ids))
+	sort.Sort(pgids(f.ids))
 }
 
 // write writes the page ids onto a freelist page. All free and pending ids are

freelist_test.go

@@ -29,9 +29,9 @@ func TestFreelist_release(t *testing.T) {
 	f.free(102, &page{id: 39})
 	f.release(100)
 	f.release(101)
-	assert.Equal(t, f.ids, []pgid{13, 12, 9})
+	assert.Equal(t, []pgid{9, 12, 13}, f.ids)
 	f.release(102)
-	assert.Equal(t, f.ids, []pgid{39, 13, 12, 9})
+	assert.Equal(t, []pgid{9, 12, 13, 39}, f.ids)
 }
 
 // Ensure that a freelist can find contiguous blocks of pages.
@@ -44,6 +44,10 @@ func TestFreelist_allocate(t *testing.T) {
 	assert.Equal(t, 7, int(f.allocate(1)))
 	assert.Equal(t, 0, int(f.allocate(0)))
 	assert.Equal(t, []pgid{9, 18}, f.ids)
+	assert.Equal(t, 9, int(f.allocate(1)))
+	assert.Equal(t, 18, int(f.allocate(1)))
+	assert.Equal(t, 0, int(f.allocate(1)))
+	assert.Equal(t, []pgid{}, f.ids)
 }
 
 // Ensure that a freelist can deserialize from a freelist page.
@@ -86,9 +90,9 @@ func TestFreelist_write(t *testing.T) {
 	// Ensure that the freelist is correct.
 	// All pages should be present and in reverse order.
 	assert.Equal(t, len(f2.ids), 5)
-	assert.Equal(t, f2.ids[0], pgid(39))
-	assert.Equal(t, f2.ids[1], pgid(28))
+	assert.Equal(t, f2.ids[0], pgid(3))
+	assert.Equal(t, f2.ids[1], pgid(11))
 	assert.Equal(t, f2.ids[2], pgid(12))
-	assert.Equal(t, f2.ids[3], pgid(11))
-	assert.Equal(t, f2.ids[4], pgid(3))
+	assert.Equal(t, f2.ids[3], pgid(28))
+	assert.Equal(t, f2.ids[4], pgid(39))
 }

page.go

@@ -133,4 +133,4 @@ type pgids []pgid
 
 func (s pgids) Len() int           { return len(s) }
 func (s pgids) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
-func (s pgids) Less(i, j int) bool { return s[i] > s[j] }
+func (s pgids) Less(i, j int) bool { return s[i] < s[j] }

tx_test.go

@@ -219,7 +219,7 @@ func TestTx_DeleteBucket(t *testing.T) {
 
 		db.Update(func(tx *Tx) error {
 			// Verify that the bucket's page is free.
-			assert.Equal(t, []pgid{5, 4}, db.freelist.all())
+			assert.Equal(t, []pgid{4, 5}, db.freelist.all())
 
 			// Create the bucket again and make sure there's not a phantom value.
 			b, err := tx.CreateBucket([]byte("widgets"))