freetype/truetype: refactor dispatch for high opcodes.

Also delete "q means that that opcode is not yet implemented", as all
valid opcodes are now implemented.

R=bsiegert
CC=golang-codereviews
https://codereview.appspot.com/53050044

freetype/truetype/hint.go

@@ -195,9 +195,6 @@ func (h *Hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point,
 			return errors.New("truetype: hinting: too many steps")
 		}
 		opcode = program[pc]
-		if popCount[opcode] == q {
-			return errors.New("truetype: hinting: unimplemented instruction")
-		}
 		if top < int(popCount[opcode]) {
 			return errors.New("truetype: hinting: stack underflow")
 		}
@@ -1115,27 +1112,24 @@ func (h *Hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point,
 			// freetype-go does not support rotated or stretched glyphs.
 			top -= 2
 
-		case opPUSHB000, opPUSHB001, opPUSHB010, opPUSHB011,
-			opPUSHB100, opPUSHB101, opPUSHB110, opPUSHB111:
-
-			opcode -= opPUSHB000 - 1
-			goto push
+		default:
+			if opcode < opPUSHB000 {
+				return errors.New("truetype: hinting: unrecognized instruction")
+			}
 
-		case opPUSHW000, opPUSHW001, opPUSHW010, opPUSHW011,
-			opPUSHW100, opPUSHW101, opPUSHW110, opPUSHW111:
+			if opcode < opMDRP00000 {
+				// PUSHxxxx opcode.
 
-			opcode -= opPUSHW000 - 1
-			opcode += 0x80
+				if opcode < opPUSHW000 {
+					opcode -= opPUSHB000 - 1
+				} else {
+					opcode -= opPUSHW000 - 1 - 0x80
+				}
 				goto push
+			}
 
-		case opMDRP00000, opMDRP00001, opMDRP00010, opMDRP00011,
-			opMDRP00100, opMDRP00101, opMDRP00110, opMDRP00111,
-			opMDRP01000, opMDRP01001, opMDRP01010, opMDRP01011,
-			opMDRP01100, opMDRP01101, opMDRP01110, opMDRP01111,
-			opMDRP10000, opMDRP10001, opMDRP10010, opMDRP10011,
-			opMDRP10100, opMDRP10101, opMDRP10110, opMDRP10111,
-			opMDRP11000, opMDRP11001, opMDRP11010, opMDRP11011,
-			opMDRP11100, opMDRP11101, opMDRP11110, opMDRP11111:
+			if opcode < opMIRP00000 {
+				// MDRPxxxxx opcode.
 
 				top--
 				i := h.stack[top]
@@ -1197,14 +1191,8 @@ func (h *Hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point,
 				oldDist = dotProduct(f26dot6(p.X-ref.X), f26dot6(p.Y-ref.Y), h.gs.pv)
 				h.move(p, distance-oldDist, true)
 
-		case opMIRP00000, opMIRP00001, opMIRP00010, opMIRP00011,
-			opMIRP00100, opMIRP00101, opMIRP00110, opMIRP00111,
-			opMIRP01000, opMIRP01001, opMIRP01010, opMIRP01011,
-			opMIRP01100, opMIRP01101, opMIRP01110, opMIRP01111,
-			opMIRP10000, opMIRP10001, opMIRP10010, opMIRP10011,
-			opMIRP10100, opMIRP10101, opMIRP10110, opMIRP10111,
-			opMIRP11000, opMIRP11001, opMIRP11010, opMIRP11011,
-			opMIRP11100, opMIRP11101, opMIRP11110, opMIRP11111:
+			} else {
+				// MIRPxxxxx opcode.
 
 				top -= 2
 				i := h.stack[top]
@@ -1276,9 +1264,7 @@ func (h *Hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point,
 
 				// Move the point.
 				h.move(p, distance-curDist, true)
-
-		default:
-			return errors.New("truetype: hinting: unrecognized instruction")
+			}
 		}
 		pc++
 		continue

freetype/truetype/opcodes.go

@@ -278,15 +278,12 @@ var popCount = [256]uint8{
 	2, 2, 2, 2, 2, 2, 1, 1, 1, 0, 2, 2, 1, 1, 1, 1, // 0x50 - 0x5f
 	2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x60 - 0x6f
 	2, 1, 1, 1, 1, 1, 1, 1, 2, 2, 0, 0, 0, 0, 1, 1, // 0x70 - 0x7f
-	0, 2, 2, 0, 0, 1, 2, 2, 1, 1, 3, 2, 2, 1, 2, q, // 0x80 - 0x8f
-	q, q, q, q, q, q, q, q, q, q, q, q, q, q, q, q, // 0x90 - 0x9f
-	q, q, q, q, q, q, q, q, q, q, q, q, q, q, q, q, // 0xa0 - 0xaf
+	0, 2, 2, 0, 0, 1, 2, 2, 1, 1, 3, 2, 2, 1, 2, 0, // 0x80 - 0x8f
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x90 - 0x9f
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xa0 - 0xaf
 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xb0 - 0xbf
 	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xc0 - 0xcf
 	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xd0 - 0xdf
 	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // 0xe0 - 0xef
 	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // 0xf0 - 0xff
 }
-
-// popCount[opcode] == q means that that opcode is not yet implemented.
-const q = 255