Reduce padding overhead in compressed blocks.

2 files changed, 18 insertions, 13 deletions

diff --git a/sys/dev/usb/udl.c b/sys/dev/usb/udl.c
index 64f99e1d608..fc9ad59f639 100644
--- a/sys/dev/usb/udl.c
+++ b/sys/dev/usb/udl.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: udl.c,v 1.26 2009/08/26 19:30:46 mglocker Exp $ */
+/*	$OpenBSD: udl.c,v 1.27 2009/08/27 19:43:50 mglocker Exp $ */
 
 /*
  * Copyright (c) 2009 Marcus Glocker <mglocker@openbsd.org>
@@ -26,8 +26,6 @@
  * This driver has been inspired by the cfxga(4) driver because we have
  * to deal with similar challenges, like no direct access to the video
  * memory.
- *
- * TODO: - Reduce padding overhead in compressed blocks.
  */
 
 #include <sys/param.h>
@@ -1055,7 +1053,7 @@ udl_cmd_insert_buf_comp(struct udl_softc *sc, uint8_t *buf, uint32_t len)
 	uint16_t *pixels, prev;
 	int16_t diff;
 	uint32_t bit_count, bit_pattern, bit_cur;
-	int i, j, bytes, eob, padding;
+	int i, j, bytes, eob, padding, next;
 
 	udl_cmd_insert_check(cb, len);
 
@@ -1067,7 +1065,7 @@ udl_cmd_insert_buf_comp(struct udl_softc *sc, uint8_t *buf, uint32_t len)
 	 * skip the header and finish up the main-block.  We return zero
 	 * to signal our caller that the header has been skipped.
 	 */
-	if (cb->compblock >= UDL_CB_RESTART1_SIZE) {
+	if (cb->compblock > UDL_CB_RESTART_SIZE) {
 		cb->off -= UDL_CMD_WRITE_HEAD_SIZE;
 		cb->compblock -= UDL_CMD_WRITE_HEAD_SIZE;
 		eob = 1;
@@ -1090,6 +1088,18 @@ udl_cmd_insert_buf_comp(struct udl_softc *sc, uint8_t *buf, uint32_t len)
 		bit_count = h->bit_count;
 		bit_pattern = betoh32(h->bit_pattern);
 
+
+		/* we are near the end of the main-block, so quit loop */
+		if (bit_count % 8 == 0)
+			next = bit_count / 8;
+		else
+			next = (bit_count / 8) + 1;
+
+		if (cb->compblock + next >= UDL_CB_BODY_SIZE) {
+			eob = 1;
+			break;
+		}
+
 		/* generate one pixel compressed data */
 		for (j = 0; j < bit_count; j++) {
 			if (bit_pos == 0)
@@ -1105,10 +1115,6 @@ udl_cmd_insert_buf_comp(struct udl_softc *sc, uint8_t *buf, uint32_t len)
 			}
 		}
 		bytes += 2;
-
-		/* we are near the end of the main-block, so quit loop */
-		if (cb->compblock >= UDL_CB_RESTART1_SIZE)
-			eob = 1;
 	}
 
 	/*
@@ -1148,7 +1154,7 @@ udl_cmd_insert_head_comp(struct udl_softc *sc, uint32_t len)
 
 	udl_cmd_insert_check(cb, len);
 
-	if (cb->compblock >= UDL_CB_RESTART2_SIZE) {
+	if (cb->compblock > UDL_CB_BODY_SIZE) {
 		cb->off -= UDL_CMD_COPY_HEAD_SIZE;
 		cb->compblock -= UDL_CMD_COPY_HEAD_SIZE;
 
diff --git a/sys/dev/usb/udl.h b/sys/dev/usb/udl.h
index 1ab664283e6..c278dc2e5c1 100644
--- a/sys/dev/usb/udl.h
+++ b/sys/dev/usb/udl.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: udl.h,v 1.5 2009/08/26 12:23:39 mglocker Exp $ */
+/*	$OpenBSD: udl.h,v 1.6 2009/08/27 19:43:50 mglocker Exp $ */
 
 /*
  * Copyright (c) 2009 Marcus Glocker <mglocker@openbsd.org>
@@ -172,8 +172,7 @@ struct udl_huffman {
 #define UDL_CB_TOTAL_SIZE		512
 #define UDL_CB_TAIL_SIZE		4
 #define UDL_CB_BODY_SIZE		(UDL_CB_TOTAL_SIZE - UDL_CB_TAIL_SIZE)
-#define UDL_CB_RESTART1_SIZE		(UDL_CB_BODY_SIZE - 4)
-#define UDL_CB_RESTART2_SIZE		(UDL_CB_BODY_SIZE - 9)
+#define UDL_CB_RESTART_SIZE		(UDL_CB_BODY_SIZE - UDL_CB_TAIL_SIZE)
 
 uint8_t udl_decomp_table[] = {
 	0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,