Fix Issue #21: automatic calculation of alignment padding after lists

1 files changed, 29 insertions, 23 deletions

diff --git a/nexgb/xf86vidmode/xf86vidmode.go b/nexgb/xf86vidmode/xf86vidmode.go
index 8abb44e..5b0f1f8 100644
--- a/nexgb/xf86vidmode/xf86vidmode.go
+++ b/nexgb/xf86vidmode/xf86vidmode.go
@@ -408,7 +408,7 @@ func (v ModeInfo) Bytes() []byte {
 	xgb.Put32(buf[b:], v.Privsize)
 	b += 4
 
-	return buf
+	return buf[:b]
 }
 
 // ModeInfoListBytes writes a list of ModeInfo values to a byte slice.
@@ -676,7 +676,7 @@ func addModeLineRequest(c *xgb.Conn, Screen uint32, Dotclock Dotclock, Hdisplay
 	b += 12 // padding
 
 	copy(buf[b:], Private[:Privsize])
-	b += xgb.Pad(int(Privsize))
+	b += int(Privsize)
 
 	return buf
 }
@@ -774,7 +774,7 @@ func deleteModeLineRequest(c *xgb.Conn, Screen uint32, Dotclock Dotclock, Hdispl
 	b += 4
 
 	copy(buf[b:], Private[:Privsize])
-	b += xgb.Pad(int(Privsize))
+	b += int(Privsize)
 
 	return buf
 }
@@ -956,7 +956,6 @@ func getDotClocksReply(buf []byte) *GetDotClocksReply {
 		v.Clock[i] = xgb.Get32(buf[b:])
 		b += 4
 	}
-	b = xgb.Pad(b)
 
 	return v
 }
@@ -1120,9 +1119,11 @@ type GetGammaRampReply struct {
 	// padding: 1 bytes
 	Size uint16
 	// padding: 22 bytes
-	Red   []uint16 // size: xgb.Pad((((int(Size) + 1) & -2) * 2))
+	Red []uint16 // size: xgb.Pad((((int(Size) + 1) & -2) * 2))
+	// alignment gap to multiple of 2
 	Green []uint16 // size: xgb.Pad((((int(Size) + 1) & -2) * 2))
-	Blue  []uint16 // size: xgb.Pad((((int(Size) + 1) & -2) * 2))
+	// alignment gap to multiple of 2
+	Blue []uint16 // size: xgb.Pad((((int(Size) + 1) & -2) * 2))
 }
 
 // Reply blocks and returns the reply data for a GetGammaRamp request.
@@ -1160,21 +1161,22 @@ func getGammaRampReply(buf []byte) *GetGammaRampReply {
 		v.Red[i] = xgb.Get16(buf[b:])
 		b += 2
 	}
-	b = xgb.Pad(b)
+
+	b = (b + 1) & ^1 // alignment gap
 
 	v.Green = make([]uint16, ((int(v.Size) + 1) & -2))
 	for i := 0; i < int(((int(v.Size) + 1) & -2)); i++ {
 		v.Green[i] = xgb.Get16(buf[b:])
 		b += 2
 	}
-	b = xgb.Pad(b)
+
+	b = (b + 1) & ^1 // alignment gap
 
 	v.Blue = make([]uint16, ((int(v.Size) + 1) & -2))
 	for i := 0; i < int(((int(v.Size) + 1) & -2)); i++ {
 		v.Blue[i] = xgb.Get16(buf[b:])
 		b += 2
 	}
-	b = xgb.Pad(b)
 
 	return v
 }
@@ -1413,7 +1415,7 @@ func getModeLineReply(buf []byte) *GetModeLineReply {
 
 	v.Private = make([]byte, v.Privsize)
 	copy(v.Private[:v.Privsize], buf[b:])
-	b += xgb.Pad(int(v.Privsize))
+	b += int(v.Privsize)
 
 	return v
 }
@@ -1479,7 +1481,8 @@ type GetMonitorReply struct {
 	NumHsync     byte
 	NumVsync     byte
 	// padding: 20 bytes
-	Hsync        []Syncrange // size: xgb.Pad((int(NumHsync) * 4))
+	Hsync []Syncrange // size: xgb.Pad((int(NumHsync) * 4))
+	// alignment gap to multiple of 4
 	Vsync        []Syncrange // size: xgb.Pad((int(NumVsync) * 4))
 	Vendor       string      // size: xgb.Pad((int(VendorLength) * 1))
 	AlignmentPad []byte      // size: xgb.Pad(((((int(VendorLength) + 3) & -4) - int(VendorLength)) * 1))
@@ -1530,14 +1533,14 @@ func getMonitorReply(buf []byte) *GetMonitorReply {
 		v.Hsync[i] = Syncrange(xgb.Get32(buf[b:]))
 		b += 4
 	}
-	b = xgb.Pad(b)
+
+	b = (b + 3) & ^3 // alignment gap
 
 	v.Vsync = make([]Syncrange, v.NumVsync)
 	for i := 0; i < int(v.NumVsync); i++ {
 		v.Vsync[i] = Syncrange(xgb.Get32(buf[b:]))
 		b += 4
 	}
-	b = xgb.Pad(b)
 
 	{
 		byteString := make([]byte, v.VendorLength)
@@ -1548,7 +1551,7 @@ func getMonitorReply(buf []byte) *GetMonitorReply {
 
 	v.AlignmentPad = make([]byte, (((int(v.VendorLength) + 3) & -4) - int(v.VendorLength)))
 	copy(v.AlignmentPad[:(((int(v.VendorLength)+3)&-4)-int(v.VendorLength))], buf[b:])
-	b += xgb.Pad(int((((int(v.VendorLength) + 3) & -4) - int(v.VendorLength))))
+	b += int((((int(v.VendorLength) + 3) & -4) - int(v.VendorLength)))
 
 	{
 		byteString := make([]byte, v.ModelLength)
@@ -1922,7 +1925,7 @@ func modModeLineRequest(c *xgb.Conn, Screen uint32, Hdisplay uint16, Hsyncstart
 	b += 4
 
 	copy(buf[b:], Private[:Privsize])
-	b += xgb.Pad(int(Privsize))
+	b += int(Privsize)
 
 	return buf
 }
@@ -2178,7 +2181,7 @@ func (cook SetGammaRampCookie) Check() error {
 // Write request to wire for SetGammaRamp
 // setGammaRampRequest writes a SetGammaRamp request to a byte slice.
 func setGammaRampRequest(c *xgb.Conn, Screen uint16, Size uint16, Red []uint16, Green []uint16, Blue []uint16) []byte {
-	size := xgb.Pad((((8 + xgb.Pad((((int(Size) + 1) & -2) * 2))) + xgb.Pad((((int(Size) + 1) & -2) * 2))) + xgb.Pad((((int(Size) + 1) & -2) * 2))))
+	size := xgb.Pad((((((8 + xgb.Pad((((int(Size) + 1) & -2) * 2))) + 2) + xgb.Pad((((int(Size) + 1) & -2) * 2))) + 2) + xgb.Pad((((int(Size) + 1) & -2) * 2))))
 	b := 0
 	buf := make([]byte, size)
 
@@ -2188,7 +2191,7 @@ func setGammaRampRequest(c *xgb.Conn, Screen uint16, Size uint16, Red []uint16,
 	buf[b] = 18 // request opcode
 	b += 1
 
-	xgb.Put16(buf[b:], uint16(size/4)) // write request size in 4-byte units
+	blen := b
 	b += 2
 
 	xgb.Put16(buf[b:], Screen)
@@ -2201,21 +2204,24 @@ func setGammaRampRequest(c *xgb.Conn, Screen uint16, Size uint16, Red []uint16,
 		xgb.Put16(buf[b:], Red[i])
 		b += 2
 	}
-	b = xgb.Pad(b)
+
+	b = (b + 1) & ^1 // alignment gap
 
 	for i := 0; i < int(((int(Size) + 1) & -2)); i++ {
 		xgb.Put16(buf[b:], Green[i])
 		b += 2
 	}
-	b = xgb.Pad(b)
+
+	b = (b + 1) & ^1 // alignment gap
 
 	for i := 0; i < int(((int(Size) + 1) & -2)); i++ {
 		xgb.Put16(buf[b:], Blue[i])
 		b += 2
 	}
-	b = xgb.Pad(b)
 
-	return buf
+	b = xgb.Pad(b)
+	xgb.Put16(buf[blen:], uint16(b/4)) // write request size in 4-byte units
+	return buf[:b]
 }
 
 // SetViewPortCookie is a cookie used only for SetViewPort requests.
@@ -2432,7 +2438,7 @@ func switchToModeRequest(c *xgb.Conn, Screen uint32, Dotclock Dotclock, Hdisplay
 	b += 4
 
 	copy(buf[b:], Private[:Privsize])
-	b += xgb.Pad(int(Privsize))
+	b += int(Privsize)
 
 	return buf
 }
@@ -2566,7 +2572,7 @@ func validateModeLineRequest(c *xgb.Conn, Screen uint32, Dotclock Dotclock, Hdis
 	b += 4
 
 	copy(buf[b:], Private[:Privsize])
-	b += xgb.Pad(int(Privsize))
+	b += int(Privsize)
 
 	return buf
 }