1 files changed, 53 insertions, 0 deletions
diff --git a/src/pkg/runtime/tiny/io.go b/src/pkg/runtime/tiny/io.go
new file mode 100644
index 000000000..f30e68889
--- /dev/null
+++ b/src/pkg/runtime/tiny/io.go
@@ -0,0 +1,53 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Simple CGA screen output
+
+package runtime
+
+import "unsafe"
+
+var crt *[25 * 80]uint16
+var pos int
+
+func putc(c int) {
+	const (
+		port  = 0x3d4
+		color = 0x0700 // white on black
+	)
+
+	if crt == nil {
+		// init on demand in case printf is called before
+		// initialization runs.
+		var mem uintptr = 0xb8000
+		crt = (*[25 * 80]uint16)(unsafe.Pointer(mem))
+		pos = 0
+		for i := range crt[0:] {
+			crt[i] = 0
+		}
+	}
+
+	switch c {
+	case '\n':
+		pos += 80 - pos%80
+	default:
+		crt[pos] = uint16(c&0xff | color)
+		pos++
+	}
+
+	if pos/80 >= 24 {
+		copy(crt[0:], crt[80:])
+		pos -= 80
+		for i := 0; i < 80; i++ {
+			crt[24*80+i] = 0
+		}
+	}
+	crt[pos] = ' ' | color
+}
+
+func write(fd int32, b []byte) {
+	for _, c := range b {
+		putc(int(c))
+	}
+}