guint32
crc32_ccitt_tvb_seed(tvbuff_t *tvb, guint len, guint32 seed)
{
const guint8* buf;
tvb_ensure_bytes_exist(tvb, 0, len); /* len == -1 not allowed */
buf = tvb_get_ptr(tvb, 0, len);
return ( crc32_ccitt_seed(buf, len, seed) );
}
/* Calculates a CRC32 checksum from the tvb zeroing out four bytes at the offset and checks it with the given crc32 and adds the result to the tree
* Returns true if the calculated CRC32 matches the passed CRC32.
* */
static gboolean ts2_add_checked_crc32(proto_tree *tree, int hf_item, tvbuff_t *tvb, guint16 offset, guint32 icrc32 )
{
guint8 *zero;
guint32 ocrc32;
zero = ep_alloc0(4);
ocrc32 = crc32_ccitt_tvb(tvb, offset);
ocrc32 = crc32_ccitt_seed(zero, 4, 0xffffffff-ocrc32);
ocrc32 = crc32_ccitt_tvb_offset_seed(tvb, offset+4, tvb_reported_length_remaining(tvb, offset+4), 0xffffffff-ocrc32);
if(icrc32==ocrc32)
{
proto_tree_add_uint_format(tree, hf_item, tvb, offset, 4, tvb_get_letohl(tvb, 16), "crc32: 0x%04x [correct]", tvb_get_letohl(tvb, offset));
return TRUE;
}
else
{
proto_tree_add_uint_format(tree, hf_item, tvb, offset, 4, tvb_get_letohl(tvb,16), "crc32: 0x%04x [incorrect, should be 0x%04x]", tvb_get_letohl(tvb, offset),ocrc32);
return FALSE;
}
}
