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utils: Simplify fractions before doing calculations that could cause overflows

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... to prevent some unnecessary overflows from happenening.
This commit is contained in:
Sebastian Dröge 2010-05-13 08:21:37 +02:00
parent ee21479eab
commit beb24d05af
1 changed files with 25 additions and 12 deletions
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37
gst/gstutils.c
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@ -4026,17 +4026,21 @@ gst_util_fraction_multiply (gint a_n, gint a_d, gint b_n, gint b_d,
g_return_val_if_fail (a_d != 0, FALSE);
g_return_val_if_fail (b_d != 0, FALSE);
gcd = gst_util_greatest_common_divisor (a_n, a_d);
a_n /= gcd;
a_d /= gcd;
gcd = gst_util_greatest_common_divisor (b_n, b_d);
b_n /= gcd;
b_d /= gcd;
gcd = gst_util_greatest_common_divisor (a_n, b_d);
if (gcd) {
a_n /= gcd;
b_d /= gcd;
}
a_n /= gcd;
b_d /= gcd;
gcd = gst_util_greatest_common_divisor (a_d, b_n);
if (gcd) {
a_d /= gcd;
b_n /= gcd;
}
a_d /= gcd;
b_n /= gcd;
/* This would result in overflow */
if (a_n != 0 && G_MAXINT / ABS (a_n) < ABS (b_n))
@ -4048,10 +4052,8 @@ gst_util_fraction_multiply (gint a_n, gint a_d, gint b_n, gint b_d,
*res_d = a_d * b_d;
gcd = gst_util_greatest_common_divisor (*res_n, *res_d);
if (gcd) {
*res_n /= gcd;
*res_d /= gcd;
}
*res_n /= gcd;
*res_d /= gcd;
return TRUE;
}
@ -4083,6 +4085,14 @@ gst_util_fraction_add (gint a_n, gint a_d, gint b_n, gint b_d, gint * res_n,
g_return_val_if_fail (a_d != 0, FALSE);
g_return_val_if_fail (b_d != 0, FALSE);
gcd = gst_util_greatest_common_divisor (a_n, a_d);
a_n /= gcd;
a_d /= gcd;
gcd = gst_util_greatest_common_divisor (b_n, b_d);
b_n /= gcd;
b_d /= gcd;
if (a_n == 0) {
*res_n = b_n;
*res_d = b_d;
@ -4109,6 +4119,9 @@ gst_util_fraction_add (gint a_n, gint a_d, gint b_n, gint b_d, gint * res_n,
if (gcd) {
*res_n /= gcd;
*res_d /= gcd;
} else {
/* res_n == 0 */
*res_d = 1;
}
return TRUE;