From 8b05e8f31008070c6ef4ad07e90e07d8c6049e59 Mon Sep 17 00:00:00 2001
From: Stephen Baynham <sdbaynham@gmail.com>
Date: Mon, 10 Apr 2023 15:03:12 -0700
Subject: [PATCH] Fix alignment

---
 alloc_test.go | 20 ++++++++++----------
 allocator.go  | 23 +++++++++++++++--------
 2 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/alloc_test.go b/alloc_test.go
index 907416d..6b735e0 100644
--- a/alloc_test.go
+++ b/alloc_test.go
@@ -11,9 +11,9 @@ func TestBasicFunc(t *testing.T) {
 	require.NotNil(t, alloc.Malloc(1000))
 
 	require.Len(t, alloc.basePages, 1)
-	require.Equal(t, 1101, alloc.basePages[0].nextOffset)
+	require.Equal(t, 1112, alloc.basePages[0].nextOffset)
 	require.Equal(t, 4096, alloc.basePages[0].size)
-	require.Equal(t, 2995, alloc.basePages[0].remainingSize)
+	require.Equal(t, 2984, alloc.basePages[0].remainingSize)
 
 	ReturnAlloc(alloc)
 
@@ -34,13 +34,13 @@ func TestMultiPage(t *testing.T) {
 
 	require.Len(t, alloc.basePages, 2)
 	require.Len(t, alloc.standaloneAllocs, 0)
-	require.Equal(t, 3600, alloc.basePages[0].nextOffset)
+	require.Equal(t, 3616, alloc.basePages[0].nextOffset)
 	require.Equal(t, 4096, alloc.basePages[0].size)
-	require.Equal(t, 496, alloc.basePages[0].remainingSize)
+	require.Equal(t, 480, alloc.basePages[0].remainingSize)
 
-	require.Equal(t, 900, alloc.basePages[1].nextOffset)
+	require.Equal(t, 904, alloc.basePages[1].nextOffset)
 	require.Equal(t, 4096, alloc.basePages[1].size)
-	require.Equal(t, 3196, alloc.basePages[1].remainingSize)
+	require.Equal(t, 3192, alloc.basePages[1].remainingSize)
 
 	ReturnAlloc(alloc)
 
@@ -60,9 +60,9 @@ func TestSlightlyTooBigStandalone(t *testing.T) {
 
 	require.Len(t, alloc.basePages, 1)
 	require.Len(t, alloc.standaloneAllocs, 1)
-	require.Equal(t, 3600, alloc.basePages[0].nextOffset)
+	require.Equal(t, 3616, alloc.basePages[0].nextOffset)
 	require.Equal(t, 4096, alloc.basePages[0].size)
-	require.Equal(t, 496, alloc.basePages[0].remainingSize)
+	require.Equal(t, 480, alloc.basePages[0].remainingSize)
 
 	ReturnAlloc(alloc)
 
@@ -82,9 +82,9 @@ func TestCouldBeStandaloneButFit(t *testing.T) {
 
 	require.Len(t, alloc.basePages, 1)
 	require.Len(t, alloc.standaloneAllocs, 0)
-	require.Equal(t, 3900, alloc.basePages[0].nextOffset)
+	require.Equal(t, 3912, alloc.basePages[0].nextOffset)
 	require.Equal(t, 4096, alloc.basePages[0].size)
-	require.Equal(t, 196, alloc.basePages[0].remainingSize)
+	require.Equal(t, 184, alloc.basePages[0].remainingSize)
 
 	ReturnAlloc(alloc)
 
diff --git a/allocator.go b/allocator.go
index 3f008fd..134d560 100644
--- a/allocator.go
+++ b/allocator.go
@@ -8,8 +8,8 @@ import "unsafe"
 
 type allocatorPage struct {
 	remainingSize int
-	nextOffset int
-	size int
+	nextOffset    int
+	size          int
 
 	buffer unsafe.Pointer
 }
@@ -18,8 +18,8 @@ func createPage(size int) *allocatorPage {
 	ptr := C.malloc(C.size_t(size))
 	return &allocatorPage{
 		remainingSize: size,
-		nextOffset: 0,
-		size: size,
+		nextOffset:    0,
+		size:          size,
 
 		buffer: ptr,
 	}
@@ -40,17 +40,24 @@ func (p *allocatorPage) NextPtr(size int) unsafe.Pointer {
 	}
 
 	ptr := unsafe.Add(p.buffer, p.nextOffset)
+	oldOffset := p.nextOffset
+
 	p.nextOffset += size
-	p.remainingSize -= size
+	alignment := p.nextOffset % 8
+	if alignment != 0 {
+		p.nextOffset = p.nextOffset - (p.nextOffset % 8) + 8
+	}
+
+	p.remainingSize -= p.nextOffset - oldOffset
 
 	return ptr
 }
 
 type Allocator struct {
-	basePageSize int
+	basePageSize           int
 	considerStandaloneSize int
 
-	basePages []*allocatorPage
+	basePages        []*allocatorPage
 	standaloneAllocs []unsafe.Pointer
 }
 
@@ -72,7 +79,7 @@ func (a *Allocator) Malloc(size int) unsafe.Pointer {
 }
 
 func (a *Allocator) CString(str string) unsafe.Pointer {
-	strByteLen := len(str)+1
+	strByteLen := len(str) + 1
 	ptr := a.Malloc(strByteLen)
 	ptrSlice := ([]byte)(unsafe.Slice((*byte)(ptr), strByteLen))
 	copy(ptrSlice, str)