From f0ad07c7d4a23e9a4a27fc9138cde5856cb04ee9 Mon Sep 17 00:00:00 2001
From: Xingyu Chen <wizard_cxy@hotmail.com>
Date: Mon, 21 Jan 2019 15:42:17 +0800
Subject: [PATCH] add getFreePageIDs (#140)

---
 db.go            |  2 +-
 freelist.go      | 12 ++++++++----
 freelist_test.go | 28 ++++++++++++++--------------
 3 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/db.go b/db.go
index d91dcf8..a72fad5 100644
--- a/db.go
+++ b/db.go
@@ -291,7 +291,7 @@ func (db *DB) loadFreelist() {
 			// Read free list from freelist page.
 			db.freelist.read(db.page(db.meta().freelist))
 		}
-		db.stats.FreePageN = len(db.freelist.ids)
+		db.stats.FreePageN = len(db.freelist.getFreePageIDs())
 	})
 }
 
diff --git a/freelist.go b/freelist.go
index c3c25e7..0d080c6 100644
--- a/freelist.go
+++ b/freelist.go
@@ -69,7 +69,7 @@ func (f *freelist) copyall(dst []pgid) {
 		m = append(m, txp.ids...)
 	}
 	sort.Sort(m)
-	mergepgids(dst, f.ids, m)
+	mergepgids(dst, f.getFreePageIDs(), m)
 }
 
 // allocate returns the starting page id of a contiguous list of pages of a given size.
@@ -266,6 +266,10 @@ func (f *freelist) readIDs(ids []pgid) {
 	f.reindex()
 }
 
+func (f *freelist) getFreePageIDs() []pgid {
+	return f.ids
+}
+
 // 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.
@@ -307,7 +311,7 @@ func (f *freelist) reload(p *page) {
 	// Check each page in the freelist and build a new available freelist
 	// with any pages not in the pending lists.
 	var a []pgid
-	for _, id := range f.ids {
+	for _, id := range f.getFreePageIDs() {
 		if !pcache[id] {
 			a = append(a, id)
 		}
@@ -318,8 +322,8 @@ func (f *freelist) reload(p *page) {
 
 // reindex rebuilds the free cache based on available and pending free lists.
 func (f *freelist) reindex() {
-	f.cache = make(map[pgid]bool, len(f.ids))
-	for _, id := range f.ids {
+	f.cache = make(map[pgid]bool, len(f.getFreePageIDs()))
+	for _, id := range f.getFreePageIDs() {
 		f.cache[id] = true
 	}
 	for _, txp := range f.pending {
diff --git a/freelist_test.go b/freelist_test.go
index 8478777..04fea96 100644
--- a/freelist_test.go
+++ b/freelist_test.go
@@ -34,13 +34,13 @@ func TestFreelist_release(t *testing.T) {
 	f.free(102, &page{id: 39})
 	f.release(100)
 	f.release(101)
-	if exp := []pgid{9, 12, 13}; !reflect.DeepEqual(exp, f.ids) {
-		t.Fatalf("exp=%v; got=%v", exp, f.ids)
+	if exp := []pgid{9, 12, 13}; !reflect.DeepEqual(exp, f.getFreePageIDs()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.getFreePageIDs())
 	}
 
 	f.release(102)
-	if exp := []pgid{9, 12, 13, 39}; !reflect.DeepEqual(exp, f.ids) {
-		t.Fatalf("exp=%v; got=%v", exp, f.ids)
+	if exp := []pgid{9, 12, 13, 39}; !reflect.DeepEqual(exp, f.getFreePageIDs()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.getFreePageIDs())
 	}
 }
 
@@ -167,8 +167,8 @@ func TestFreelist_releaseRange(t *testing.T) {
 			f.releaseRange(r.begin, r.end)
 		}
 
-		if exp := c.wantFree; !reflect.DeepEqual(exp, f.ids) {
-			t.Errorf("exp=%v; got=%v for %s", exp, f.ids, c.title)
+		if exp := c.wantFree; !reflect.DeepEqual(exp, f.getFreePageIDs()) {
+			t.Errorf("exp=%v; got=%v for %s", exp, f.getFreePageIDs(), c.title)
 		}
 	}
 }
@@ -199,8 +199,8 @@ func TestFreelist_allocate(t *testing.T) {
 	if id := int(f.allocate(1, 0)); id != 0 {
 		t.Fatalf("exp=0; got=%v", id)
 	}
-	if exp := []pgid{9, 18}; !reflect.DeepEqual(exp, f.ids) {
-		t.Fatalf("exp=%v; got=%v", exp, f.ids)
+	if exp := []pgid{9, 18}; !reflect.DeepEqual(exp, f.getFreePageIDs()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.getFreePageIDs())
 	}
 
 	if id := int(f.allocate(1, 1)); id != 9 {
@@ -212,8 +212,8 @@ func TestFreelist_allocate(t *testing.T) {
 	if id := int(f.allocate(1, 1)); id != 0 {
 		t.Fatalf("exp=0; got=%v", id)
 	}
-	if exp := []pgid{}; !reflect.DeepEqual(exp, f.ids) {
-		t.Fatalf("exp=%v; got=%v", exp, f.ids)
+	if exp := []pgid{}; !reflect.DeepEqual(exp, f.getFreePageIDs()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.getFreePageIDs())
 	}
 }
 
@@ -235,8 +235,8 @@ func TestFreelist_read(t *testing.T) {
 	f.read(page)
 
 	// Ensure that there are two page ids in the freelist.
-	if exp := []pgid{23, 50}; !reflect.DeepEqual(exp, f.ids) {
-		t.Fatalf("exp=%v; got=%v", exp, f.ids)
+	if exp := []pgid{23, 50}; !reflect.DeepEqual(exp, f.getFreePageIDs()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.getFreePageIDs())
 	}
 }
 
@@ -258,8 +258,8 @@ func TestFreelist_write(t *testing.T) {
 
 	// Ensure that the freelist is correct.
 	// All pages should be present and in reverse order.
-	if exp := []pgid{3, 11, 12, 28, 39}; !reflect.DeepEqual(exp, f2.ids) {
-		t.Fatalf("exp=%v; got=%v", exp, f2.ids)
+	if exp := []pgid{3, 11, 12, 28, 39}; !reflect.DeepEqual(exp, f2.getFreePageIDs()) {
+		t.Fatalf("exp=%v; got=%v", exp, f2.getFreePageIDs())
 	}
 }