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TDS: Improve handling of scale for TDS numeric and decimal fields. 

For numeric and decimal fields, we can use doubles to display many
decimal and numeric fields exactly. It only starts to fall down when
we get more than 15 decimal digits.

Bug: 16041
Change-Id: Idae1790ade7106d7557739220756ef9e9281378c
Reviewed-on: https://code.wireshark.org/review/34471
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>
This commit is contained in:
Craig Jackson 2019-08-13 20:45:01 -04:00 committed by Anders Broman
parent 39bbb90e78
commit 3af946e886
1 changed files with 52 additions and 12 deletions
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64
epan/dissectors/packet-tds.c
View File

@ -142,6 +142,9 @@
#include <epan/prefs.h>
#include <epan/expert.h>
#include <epan/proto_data.h>
#include <math.h>
#include "packet-tcp.h"
#define TDS_QUERY_PKT 1 /* SQLBatch in MS-TDS revision 18.0 */
@ -2574,16 +2577,29 @@ dissect_tds_type_varbyte(tvbuff_t *tvb, guint *offset, packet_info *pinfo, proto
guint8 data_array[8];
guint j;
gint64 int64_value = 0;
/*
* XXX - this actually falls down if we have more than
* 53 bits of significance. (Assuming IEEE 754 floating-piont.)
* This isn't likely to happen in practice.
* Decimal/numeric fields are intended to be used
* for precise integers/scaled integers. They would not
* be typically be used for high dynamic range quantities.
*/
(void) tvb_memcpy(tvb, data_array, *offset, length);
for (j = 0; j < length; j++) {
int64_value = (int64_value << 8) | data_array[j];
}
proto_item_append_text(numericitem,
" (%" G_GINT64_MODIFIER "d)",
(sign ? -int64_value : int64_value));
if(scale != 0) {
proto_item_append_text(numericitem, " x 10^-%u", scale);
if(scale == 0) {
proto_item_append_text(numericitem,
" (%" G_GINT64_MODIFIER "d)",
(sign ? -int64_value : int64_value));
}
else {
proto_item_append_text(numericitem,
" (%.*f)", scale,
(double)(sign ? -int64_value
: int64_value)/pow(10.0, (double)(scale)));
}
}
*offset += length;
@ -2615,16 +2631,35 @@ dissect_tds_type_varbyte(tvbuff_t *tvb, guint *offset, packet_info *pinfo, proto
guint8 data_array[8];
gint j;
gint64 int64_value = 0;
/*
* XXX - this actually falls down if we have more than
* 53 bits of significance. (Assuming IEEE 754 floating-piont.)
* This isn't likely to happen in practice.
* Decimal/numeric fields are intended to be used
* for precise integers/scaled integers. They would not
* be typically be used for high dynamic range quantities.
*
* We could change the "length <= 8" criterion above,
* but Microsoft appears to only use length values which
* are multiples of 4. Any numeric/decimal with a
* precision between 9 and 19 will be stored as an
* 8-byte integer.
*/
(void) tvb_memcpy(tvb, data_array, *offset, length);
for (j = length - 1; j >= 0; j--) {
int64_value = (int64_value << 8) | data_array[j];
}
proto_item_append_text(numericitem,
" (%" G_GINT64_MODIFIER "d)",
(sign ? int64_value : -int64_value));
if(scale != 0) {
proto_item_append_text(numericitem, " x 10^-%u", scale);
if(scale == 0) {
proto_item_append_text(numericitem,
" (%" G_GINT64_MODIFIER "d)",
(sign ? -int64_value : int64_value));
}
else {
proto_item_append_text(numericitem,
" (%.*f)", scale,
(double)(sign ? int64_value
: -int64_value)/pow(10.0, (double)(scale)));
}
}
*offset += length;
@ -4829,8 +4864,13 @@ dissect_tds_rowfmt_token(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo,
}
if (is_numeric_type_tds(nl_data->columns[col]->ctype)) {
proto_tree_add_item(col_tree, hf_tds_rowfmt_precision, tvb, cur, 1, ENC_NA);
proto_tree_add_item(col_tree, hf_tds_rowfmt_scale, tvb, cur + 1, 1, ENC_NA);
guint col_precision, col_scale;
proto_tree_add_item_ret_uint(col_tree, hf_tds_rowfmt_precision,
tvb, cur, 1, ENC_NA, &col_precision);
proto_tree_add_item_ret_uint(col_tree, hf_tds_rowfmt_scale,
tvb, cur + 1, 1, ENC_NA, &col_scale);
nl_data->columns[col]->precision = col_precision;
nl_data->columns[col]->scale = col_scale;
cur += 2;
}