[PATCH v3 2/6] decimal: fix encoding numbers with positive exponent.
Serge Petrenko
sergepetrenko at tarantool.org
Tue Aug 20 20:10:00 MSK 2019
When a number having a positive exponent is encoded, the internal
decPackedFromNumber function returns a negative scale, which differs
from the scale, returned by decimal_scale(). This leads to errors in
decoding. Account for negative scale in decimal_pack() and
decimal_unpack().
Follow-up #692
---
src/lib/core/decimal.c | 42 ++++++++++++++++++++++++++++++++--------
test/unit/decimal.c | 15 ++++++++++++--
test/unit/decimal.result | 11 ++++++++---
3 files changed, 55 insertions(+), 13 deletions(-)
diff --git a/src/lib/core/decimal.c b/src/lib/core/decimal.c
index e141a91f8..356acf6f2 100644
--- a/src/lib/core/decimal.c
+++ b/src/lib/core/decimal.c
@@ -33,6 +33,7 @@
#include "third_party/decNumber/decContext.h"
#include "third_party/decNumber/decPacked.h"
#include "lib/core/tt_static.h"
+#include "lib/msgpuck/msgpuck.h"
#include <stddef.h>
#include <stdlib.h>
#include <float.h> /* DBL_DIG */
@@ -339,20 +340,27 @@ decimal_sqrt(decimal_t *res, const decimal_t *lhs)
uint32_t
decimal_len(const decimal_t *dec)
{
- /* 1 + ceil((digits + 1) / 2) */
- return 2 + dec->digits / 2;
+ uint32_t sizeof_scale = dec->exponent > 0 ? mp_sizeof_int(-dec->exponent) :
+ mp_sizeof_uint(-dec->exponent);
+ /* sizeof_scale + ceil((digits + 1) / 2) */
+ return sizeof_scale + 1 + dec->digits / 2;
}
char *
decimal_pack(char *data, const decimal_t *dec)
{
uint32_t len = decimal_len(dec);
- *data++ = decimal_scale(dec);
- len--;
+ char *svp = data;
+ /* encode scale */
+ if (dec->exponent > 0) {
+ data = mp_encode_int(data, -dec->exponent);
+ } else {
+ data = mp_encode_uint(data, -dec->exponent);
+ }
+ len -= data - svp;
int32_t scale;
char *tmp = (char *)decPackedFromNumber((uint8_t *)data, len, &scale, dec);
assert(tmp == data);
- assert(scale == (int32_t)decimal_scale(dec));
(void)tmp;
data += len;
return data;
@@ -361,12 +369,30 @@ decimal_pack(char *data, const decimal_t *dec)
decimal_t *
decimal_unpack(const char **data, uint32_t len, decimal_t *dec)
{
- int32_t scale = *((*data)++);
- len--;
+ int32_t scale;
+ const char *svp = *data;
+ if (mp_typeof(**data) == MP_UINT) {
+ scale = mp_decode_uint(data);
+ } else if (mp_typeof(**data) == MP_INT) {
+ scale = mp_decode_int(data);
+ } else {
+ return NULL;
+ }
+ /*
+ * scale = -exponent. The exponent should be in range
+ * [-DECIMAL_MAX_DIGITS; DECIMAL_MAX_DIGITS)
+ */
+ if (scale > DECIMAL_MAX_DIGITS ||
+ scale <= -DECIMAL_MAX_DIGITS) {
+ *data = svp;
+ return NULL;
+ }
+
+ len -= *data - svp;
decimal_t *res = decPackedToNumber((uint8_t *)*data, len, &scale, dec);
if (res)
*data += len;
else
- (*data)--;
+ *data = svp;
return res;
}
diff --git a/test/unit/decimal.c b/test/unit/decimal.c
index b587e1f14..b55333ed7 100644
--- a/test/unit/decimal.c
+++ b/test/unit/decimal.c
@@ -91,7 +91,7 @@ char buf[32];
static int
test_pack_unpack(void)
{
- plan(146);
+ plan(151);
test_decpack("0");
test_decpack("-0");
@@ -112,13 +112,24 @@ test_pack_unpack(void)
test_decpack("99999999999999999999999999999999999999");
test_decpack("-99999999999999999999999999999999999999");
+ /* Check correct encoding of positive exponent numbers. */
+ decimal_t dec, d1;
+ decimal_from_string(&dec, "1e10");
+ uint32_t l1 = decimal_len(&dec);
+ ok(l1 == 2, "decimal_len() is small for positive exponent decimal");
+ char *b1 = decimal_pack(buf, &dec);
+ is(b1, buf + l1, "positive exponent decimal length");
+ const char *b2 = buf;
+ is(decimal_unpack(&b2, l1, &d1), &d1, "decimal_unpack() of a positive exponent decimal");
+ is(b1, b2, "decimal_unpack uses every byte packed by decimal_pack");
+ is(decimal_compare(&dec, &d1), 0, "positive exponent number is packed/unpacked correctly");
+
/* Pack an invalid decimal. */
char *b = buf;
*b++ = 1;
*b++ = '\xab';
*b++ = '\xcd';
const char *bb = buf;
- decimal_t dec;
is(decimal_unpack(&bb, 3, &dec), NULL, "unpack malformed decimal fails");
is(bb, buf, "decode malformed decimal preserves buffer position");
diff --git a/test/unit/decimal.result b/test/unit/decimal.result
index 1c72cdfab..2dd91af49 100644
--- a/test/unit/decimal.result
+++ b/test/unit/decimal.result
@@ -277,7 +277,7 @@ ok 275 - decimal_from_string(-1)
ok 276 - decimal_log10(-1) - error on wrong operands.
ok 277 - decimal_from_string(-10)
ok 278 - decimal_sqrt(-10) - error on wrong operands.
- 1..146
+ 1..151
ok 1 - decimal_len(0)
ok 2 - decimal_len(0) == len(decimal_pack(0)
ok 3 - decimal_unpack(decimal_pack(0))
@@ -422,6 +422,11 @@ ok 278 - decimal_sqrt(-10) - error on wrong operands.
ok 142 - decimal_unpack(decimal_pack(-99999999999999999999999999999999999999)) scale
ok 143 - decimal_unpack(decimal_pack(-99999999999999999999999999999999999999)) precision
ok 144 - str(decimal_unpack(decimal_pack(-99999999999999999999999999999999999999)) == -99999999999999999999999999999999999999
- ok 145 - unpack malformed decimal fails
- ok 146 - decode malformed decimal preserves buffer position
+ ok 145 - decimal_len() is small for positive exponent decimal
+ ok 146 - positive exponent decimal length
+ ok 147 - decimal_unpack() of a positive exponent decimal
+ ok 148 - decimal_unpack uses every byte packed by decimal_pack
+ ok 149 - positive exponent number is packed/unpacked correctly
+ ok 150 - unpack malformed decimal fails
+ ok 151 - decode malformed decimal preserves buffer position
ok 279 - subtests
--
2.20.1 (Apple Git-117)
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