add freelist interface unit tests

Signed-off-by: Thomas Jungblut <[email protected]>

internal/freelist/array_test.go

@@ -1,6 +1,7 @@
 package freelist
 
 import (
+ "github.com/stretchr/testify/require"
  "reflect"
  "testing"
 
@@ -50,3 +51,12 @@ func TestFreelistArray_allocate(t *testing.T) {
  t.Fatalf("exp=%v; got=%v", exp, f.freePageIds())
  }
 }
+
+func TestInvalidArrayAllocation(t *testing.T) {
+ f := NewArrayFreelist()
+ ids := []common.Pgid{1}
+ f.Init(ids)
+ require.Panics(t, func() {
+ f.Allocate(common.Txid(1), 1)
+ })
+}

internal/freelist/freelist.go

@@ -11,7 +11,7 @@ type ReadWriter interface {
  // Write writes the freelist into the given page.
  Write(page *common.Page)
 
- // EstimatedWritePageSize returns the size of the freelist after serialization in Write.
+ // EstimatedWritePageSize returns the size in bytes of the freelist after serialization in Write.
  // This should never underestimate the size.
  EstimatedWritePageSize() int
 }
@@ -46,13 +46,14 @@ type Interface interface {
  ReleasePendingPages()
 
  // Free releases a page and its overflow for a given transaction id.
- // If the page is already free then a panic will occur.
+ // If the page is already free or is one of the meta pages, then a panic will occur.
  Free(txId common.Txid, p *common.Page)
 
  // Freed returns whether a given page is in the free list.
  Freed(pgId common.Pgid) bool
 
  // Rollback removes the pages from a given pending tx.
+ // Should always be followed by Reload or NoSyncReload from last freelist state.
  Rollback(txId common.Txid)
 
  // Copyall copies a list of all free ids and all pending ids in one sorted list.
@@ -65,7 +66,7 @@ type Interface interface {
  // NoSyncReload reads the freelist from Pgids and filters out pending items.
  NoSyncReload(pgIds common.Pgids)
 
- // freePageIds returns the IDs of all free pages.
+ // freePageIds returns the IDs of all free pages. No free pages returns an empty slice.
  freePageIds() common.Pgids
 
  // pendingPageIds returns all pending pages by transaction id.