From bb88db68e0c1cb51f1cb8bb6e98ce72fffaa4bf1 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Tue, 28 Jul 2015 16:28:21 +1000
Subject: [PATCH] OutMessage.Append

---
 internal/buffer/out_message.go | 14 ++++++++++++--
 internal/buffer/runtime.go     |  5 +++++
 internal/buffer/runtime.s      |  3 +++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/internal/buffer/out_message.go b/internal/buffer/out_message.go
index f2dad9f..66099bf 100644
--- a/internal/buffer/out_message.go
+++ b/internal/buffer/out_message.go
@@ -15,7 +15,9 @@
 package buffer
 
 import (
+	"fmt"
 	"log"
+	"reflect"
 	"unsafe"
 
 	"github.com/jacobsa/fuse/internal/fusekernel"
@@ -87,8 +89,16 @@ func (b *OutMessage) GrowNoZero(size uintptr) (p unsafe.Pointer) {
 
 // Equivalent to growing by the length of p, then copying p over the new
 // segment. Panics if there is not enough room available.
-func (b *OutMessage) Append(p []byte) {
-	panic("TODO")
+func (b *OutMessage) Append(src []byte) {
+	p := b.GrowNoZero(uintptr(len(src)))
+	if p == nil {
+		panic(fmt.Sprintf("Can't grow %d bytes", len(src)))
+	}
+
+	sh := (*reflect.SliceHeader)(unsafe.Pointer(&src))
+	memmove(p, unsafe.Pointer(sh.Data), uintptr(sh.Len))
+
+	return
 }
 
 // Equivalent to growing by the length of s, then copying s over the new
diff --git a/internal/buffer/runtime.go b/internal/buffer/runtime.go
index 927032d..672c8a1 100644
--- a/internal/buffer/runtime.go
+++ b/internal/buffer/runtime.go
@@ -20,3 +20,8 @@ import "unsafe"
 
 // Zero the n bytes starting at p.
 func memclr(p unsafe.Pointer, n uintptr)
+
+//go:noescape
+
+// Copy from src to dst, allowing overlap.
+func memmove(dst unsafe.Pointer, src unsafe.Pointer, n uintptr)
diff --git a/internal/buffer/runtime.s b/internal/buffer/runtime.s
index 9f65b4e..f39415a 100644
--- a/internal/buffer/runtime.s
+++ b/internal/buffer/runtime.s
@@ -31,3 +31,6 @@
 
 TEXT ·memclr(SB),NOSPLIT,$0-16
 	JMP runtime·memclr(SB)
+
+TEXT ·memmove(SB),NOSPLIT,$0-24
+	JMP runtime·memmove(SB)