Use an aligned slice for file reads

kittens/pager/file_input.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"strings"
 	"time"
+	"unsafe"
 
 	"golang.org/x/sys/unix"
 )
@@ -31,9 +32,19 @@ func wait_for_file_to_grow(file_name string, limit int64) (err error) {
 	return
 }
 
+func aligned_slice(b []byte, alignment uintptr) []byte {
+	addr := uintptr(unsafe.Pointer(&b))
+	extra := addr & (alignment - 1)
+	if extra > 0 {
+		return b[alignment-extra:]
+	}
+	return b
+}
+
 func read_input(input_file *os.File, input_file_name string, input_channel chan<- input_line_struct, follow bool, count_carriage_returns bool) {
 	const buf_capacity = 8192
-	var buf_array [buf_capacity]byte
+	var buf_storage [buf_capacity + 128]byte // ensure we have an 64 byte aligned slice with at least 64 bytes after it
+	buf := aligned_slice(buf_storage[:], 64)[:buf_capacity]
 	output_buf := strings.Builder{}
 	output_buf.Grow(buf_capacity)
 	var err error
@@ -92,10 +103,10 @@ func read_input(input_file *os.File, input_file_name string, input_channel chan<
 
 	for {
 		for err != nil {
-			n, err = input_file.Read(buf_array[:])
+			n, err = input_file.Read(buf)
 			if n > 0 {
 				total_read += int64(n)
-				process_chunk(buf_array[:n])
+				process_chunk(buf)
 			}
 			if err == unix.EAGAIN || err == unix.EINTR {
 				err = nil