Add routines for CRC-16 with a polynomial of 0x3D65.

There are routines that take a buffer and a length and that take a
tvbuff, offset, and length; use those routines in the DNP dissector
(which no longer needs its own table and loop), and use the tvbuff
routine instead of calling tvb_get_ptr().

Change-Id: Ic67b0f3b65b94ea47c0fdc2f3d3b6f88df77f9c6
Reviewed-on: https://code.wireshark.org/review/3505
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 10 insertions, 0 deletions

diff --git a/epan/crc16-tvb.c b/epan/crc16-tvb.c
index 2b0479c060..10854c4401 100644
--- a/epan/crc16-tvb.c
+++ b/epan/crc16-tvb.c
@@ -122,3 +122,13 @@ guint16 crc16_0x9949_tvb_offset_seed(tvbuff_t *tvb, guint offset, guint len, gui
 
     return crc16_0x9949_seed(buf, len, seed);
 }
+
+guint16 crc16_0x3D65_tvb_offset_seed(tvbuff_t *tvb, guint offset, guint len, guint16 seed)
+{
+    const guint8 *buf;
+
+    tvb_ensure_bytes_exist(tvb, offset, len);  /* len == -1 not allowed */
+    buf = tvb_get_ptr(tvb, offset, len);
+
+    return crc16_0x3D65_seed(buf, len, seed);
+}