From f2517f394022698514ecd7e42f31ee8fed72a6a3 Mon Sep 17 00:00:00 2001
From: Nigel Tao <nigeltao@golang.org>
Date: Thu, 12 Jul 2012 20:49:12 +1000
Subject: [PATCH] freetype/truetype: odd/even opcodes.

Also re-arrange some of the switch cases to be in opcode order.

R=bsiegert
CC=golang-dev
http://codereview.appspot.com/6352097
---
 freetype/truetype/hint.go      | 24 ++++++++++++++----------
 freetype/truetype/hint_test.go | 20 ++++++++++++++++++++
 freetype/truetype/opcodes.go   |  6 +++---
 3 files changed, 37 insertions(+), 13 deletions(-)

diff --git a/freetype/truetype/hint.go b/freetype/truetype/hint.go
index 4098ee0..921c1fa 100644
--- a/freetype/truetype/hint.go
+++ b/freetype/truetype/hint.go
@@ -251,16 +251,9 @@ func (h *hinter) run(program []byte) error {
 			top--
 			h.stack[top-1] = bool2int32(h.stack[top-1] != h.stack[top])
 
-		case opAND:
-			top--
-			h.stack[top-1] = bool2int32(h.stack[top-1] != 0 && h.stack[top] != 0)
-
-		case opOR:
-			top--
-			h.stack[top-1] = bool2int32(h.stack[top-1]|h.stack[top] != 0)
-
-		case opNOT:
-			h.stack[top-1] = bool2int32(h.stack[top-1] == 0)
+		case opODD, opEVEN:
+			i := h.round(f26dot6(h.stack[top-1])) >> 6
+			h.stack[top-1] = int32(i&1) ^ int32(opcode-opODD)
 
 		case opIF:
 			top--
@@ -272,6 +265,17 @@ func (h *hinter) run(program []byte) error {
 		case opEIF:
 			// No-op.
 
+		case opAND:
+			top--
+			h.stack[top-1] = bool2int32(h.stack[top-1] != 0 && h.stack[top] != 0)
+
+		case opOR:
+			top--
+			h.stack[top-1] = bool2int32(h.stack[top-1]|h.stack[top] != 0)
+
+		case opNOT:
+			h.stack[top-1] = bool2int32(h.stack[top-1] == 0)
+
 		case opADD:
 			top--
 			h.stack[top-1] += h.stack[top]
diff --git a/freetype/truetype/hint_test.go b/freetype/truetype/hint_test.go
index b8c9d14..5039a6c 100644
--- a/freetype/truetype/hint_test.go
+++ b/freetype/truetype/hint_test.go
@@ -187,6 +187,26 @@ func TestBytecode(t *testing.T) {
 			[]int32{1, 0},
 			"",
 		},
+		{
+			"odd/even",
+			// Calculate odd(2+31/64), odd(2+32/64), even(2), even(1).
+			[]byte{
+				opPUSHB000, // [159]
+				159,
+				opODD,      // [0]
+				opPUSHB000, // [0, 160]
+				160,
+				opODD,      // [0, 1]
+				opPUSHB000, // [0, 1, 128]
+				128,
+				opEVEN,     // [0, 1, 1]
+				opPUSHB000, // [0, 1, 1, 64]
+				64,
+				opEVEN, // [0, 1, 1, 0]
+			},
+			[]int32{0, 1, 1, 0},
+			"",
+		},
 		{
 			"if true",
 			[]byte{
diff --git a/freetype/truetype/opcodes.go b/freetype/truetype/opcodes.go
index c20cc70..8a3b38f 100644
--- a/freetype/truetype/opcodes.go
+++ b/freetype/truetype/opcodes.go
@@ -96,8 +96,8 @@ const (
 	opGTEQ      = 0x53 // Greater Than or EQual
 	opEQ        = 0x54 // EQual
 	opNEQ       = 0x55 // Not EQual
-	opODD       = 0x56
-	opEVEN      = 0x57
+	opODD       = 0x56 // ODD
+	opEVEN      = 0x57 // EVEN
 	opIF        = 0x58 // IF test
 	opEIF       = 0x59 // End IF
 	opAND       = 0x5a // logical AND
@@ -276,7 +276,7 @@ var popCount = [256]uint8{
 	1, 1, 0, 2, 0, 1, 1, q, q, q, q, q, q, q, q, q, // 0x20 - 0x2f
 	q, q, q, q, q, q, q, q, q, q, q, q, q, 0, q, q, // 0x30 - 0x3f
 	0, 0, 2, 1, q, q, q, q, q, q, q, q, q, q, q, 0, // 0x40 - 0x4f
-	2, 2, 2, 2, 2, 2, q, q, 1, 0, 2, 2, 1, q, q, q, // 0x50 - 0x5f
+	2, 2, 2, 2, 2, 2, 1, 1, 1, 0, 2, 2, 1, q, q, q, // 0x50 - 0x5f
 	2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x60 - 0x6f
 	q, q, q, q, q, q, 1, 1, 2, 2, 0, q, 0, 0, 1, 1, // 0x70 - 0x7f
 	q, q, q, q, q, q, q, q, q, 1, 3, 2, 2, q, q, q, // 0x80 - 0x8f