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gstutils: API: Add fraction helper functions
gst_util_greatest_common_divisor() gst_util_double_to_fraction() gst_util_fraction_to_double() Using these instead of going over GValue has much lower overhead. Also add float<->fraction transform functions for GValue.
This commit is contained in:
Sebastian Dröge
parent
c84d17bcaf
commit
e4257e8d5f
5 changed files with 191 additions and 93 deletions
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@ -2525,6 +2525,9 @@ gst_util_uint64_scale_ceil
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gst_util_uint64_scale_int
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gst_util_uint64_scale_int_round
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gst_util_uint64_scale_int_ceil
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gst_util_greatest_common_divisor
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gst_util_fraction_to_double
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gst_util_double_to_fraction
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gst_util_seqnum_next
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gst_util_seqnum_compare
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gst_util_set_object_arg
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152
gst/gstutils.c
152
gst/gstutils.c
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@ -39,6 +39,7 @@
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#include "gstparse.h"
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#include "gstvalue.h"
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#include "gst-i18n-lib.h"
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#include <math.h>
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/**
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* gst_util_dump_mem:
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@ -3798,3 +3799,154 @@ gst_util_array_binary_search (gpointer array, guint num_elements,
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}
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}
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}
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/* Finds the greatest common divisor.
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* Returns 1 if none other found.
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* This is Euclid's algorithm. */
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/** gst_util_greatest_common_divisor:
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* @a: First value as #gint
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* @b: Second value as #gint
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*
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* Calculates the greatest common divisor of @a
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* and @b.
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*
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* Returns: Greatest common divisor of @a and @b
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*
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* Since: 0.10.26
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*/
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gint
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gst_util_greatest_common_divisor (gint a, gint b)
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{
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while (b != 0) {
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int temp = a;
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a = b;
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b = temp % b;
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}
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return ABS (a);
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}
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/** gst_util_fraction_to_double:
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* @src_n: Fraction numerator as #gint
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* @src_d: Fraction denominator #gint
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* @dest: pointer to a #gdouble for the result
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*
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* Transforms a #gdouble to a #GstFraction and simplifies
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* the result.
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*
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* Since: 0.10.26
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*/
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void
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gst_util_fraction_to_double (gint src_n, gint src_d, gdouble * dest)
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{
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g_return_if_fail (dest != NULL);
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g_return_if_fail (src_d != 0);
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*dest = ((gdouble) src_n) / ((gdouble) src_d);
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}
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#define MAX_TERMS 30
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#define MIN_DIVISOR 1.0e-10
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#define MAX_ERROR 1.0e-20
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/* use continued fractions to transform a double into a fraction,
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* see http://mathforum.org/dr.math/faq/faq.fractions.html#decfrac.
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* This algorithm takes care of overflows.
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*/
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/** gst_util_double_to_fraction:
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* @src: #gdouble to transform
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* @dest_n: pointer to a #gint to hold the result numerator
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* @dest_d: pointer to a #gint to hold the result denominator
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*
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* Transforms a #gdouble to a #GstFraction and simplifies
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* the result.
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*
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* Since: 0.10.26
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*/
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void
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gst_util_double_to_fraction (gdouble src, gint * dest_n, gint * dest_d)
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{
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gdouble V, F; /* double being converted */
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gint N, D; /* will contain the result */
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gint A; /* current term in continued fraction */
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gint64 N1, D1; /* numerator, denominator of last approx */
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gint64 N2, D2; /* numerator, denominator of previous approx */
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gint i;
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gint gcd;
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gboolean negative = FALSE;
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g_return_if_fail (dest_n != NULL);
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g_return_if_fail (dest_d != NULL);
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/* initialize fraction being converted */
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F = src;
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if (F < 0.0) {
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F = -F;
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negative = TRUE;
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}
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V = F;
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/* initialize fractions with 1/0, 0/1 */
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N1 = 1;
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D1 = 0;
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N2 = 0;
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D2 = 1;
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N = 1;
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D = 1;
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for (i = 0; i < MAX_TERMS; i++) {
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/* get next term */
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A = (gint) F; /* no floor() needed, F is always >= 0 */
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/* get new divisor */
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F = F - A;
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/* calculate new fraction in temp */
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N2 = N1 * A + N2;
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D2 = D1 * A + D2;
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/* guard against overflow */
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if (N2 > G_MAXINT || D2 > G_MAXINT) {
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break;
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}
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N = N2;
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D = D2;
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/* save last two fractions */
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N2 = N1;
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D2 = D1;
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N1 = N;
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D1 = D;
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/* quit if dividing by zero or close enough to target */
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if (F < MIN_DIVISOR || fabs (V - ((gdouble) N) / D) < MAX_ERROR) {
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break;
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}
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/* Take reciprocal */
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F = 1 / F;
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}
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/* fix for overflow */
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if (D == 0) {
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N = G_MAXINT;
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D = 1;
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}
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/* fix for negative */
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if (negative)
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N = -N;
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/* simplify */
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gcd = gst_util_greatest_common_divisor (N, D);
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if (gcd) {
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N /= gcd;
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D /= gcd;
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}
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/* set results */
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*dest_n = N;
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*dest_d = D;
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}
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@ -1166,6 +1166,10 @@ gpointer gst_util_array_binary_search (gpointer array, guint
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GstSearchMode mode, gconstpointer search_data,
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gpointer user_data);
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gint gst_util_greatest_common_divisor (gint a, gint b);
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void gst_util_fraction_to_double (gint src_n, gint src_d, gdouble *dest);
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void gst_util_double_to_fraction (gdouble src, gint *dest_n, gint *dest_d);
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G_END_DECLS
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#endif /* __GST_UTILS_H__ */
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122
gst/gstvalue.c
122
gst/gstvalue.c
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@ -43,6 +43,7 @@
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#include "glib-compat-private.h"
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#include <gst/gst.h>
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#include <gobject/gvaluecollector.h>
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#include "gstutils.h"
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typedef struct _GstValueUnionInfo GstValueUnionInfo;
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struct _GstValueUnionInfo
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@ -81,7 +82,6 @@ static GArray *gst_value_intersect_funcs;
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static GArray *gst_value_subtract_funcs;
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/* Forward declarations */
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static gint gst_greatest_common_divisor (gint a, gint b);
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static gchar *gst_value_serialize_fraction (const GValue * value);
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static GstValueCompareFunc gst_value_get_compare_func (const GValue * value1);
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@ -3476,23 +3476,6 @@ gst_value_is_fixed (const GValue * value)
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************/
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/* helper functions */
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/* Finds the greatest common divisor.
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* Returns 1 if none other found.
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* This is Euclid's algorithm. */
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static gint
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gst_greatest_common_divisor (gint a, gint b)
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{
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while (b != 0) {
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int temp = a;
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a = b;
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b = temp % b;
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}
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return ABS (a);
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}
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static void
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gst_value_init_fraction (GValue * value)
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{
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@ -3564,7 +3547,7 @@ gst_value_set_fraction (GValue * value, gint numerator, gint denominator)
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}
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/* check for reduction */
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gcd = gst_greatest_common_divisor (numerator, denominator);
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gcd = gst_util_greatest_common_divisor (numerator, denominator);
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if (gcd) {
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numerator /= gcd;
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denominator /= gcd;
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@ -3633,10 +3616,10 @@ gst_value_fraction_multiply (GValue * product, const GValue * factor1,
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d1 = factor1->data[1].v_int;
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d2 = factor2->data[1].v_int;
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gcd = gst_greatest_common_divisor (n1, d2);
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gcd = gst_util_greatest_common_divisor (n1, d2);
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n1 /= gcd;
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d2 /= gcd;
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gcd = gst_greatest_common_divisor (n2, d1);
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gcd = gst_util_greatest_common_divisor (n2, d1);
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n2 /= gcd;
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d1 /= gcd;
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@ -3759,85 +3742,26 @@ gst_value_transform_string_fraction (const GValue * src_value,
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gst_value_set_fraction (dest_value, 0, 1);
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}
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#define MAX_TERMS 30
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#define MIN_DIVISOR 1.0e-10
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#define MAX_ERROR 1.0e-20
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/* use continued fractions to transform a double into a fraction,
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* see http://mathforum.org/dr.math/faq/faq.fractions.html#decfrac.
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* This algorithm takes care of overflows.
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*/
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static void
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gst_value_transform_double_fraction (const GValue * src_value,
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GValue * dest_value)
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{
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gdouble V, F; /* double being converted */
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gint N, D; /* will contain the result */
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gint A; /* current term in continued fraction */
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gint64 N1, D1; /* numerator, denominator of last approx */
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gint64 N2, D2; /* numerator, denominator of previous approx */
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gint i;
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gboolean negative = FALSE;
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gdouble src = g_value_get_double (src_value);
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gint n, d;
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/* initialize fraction being converted */
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F = src_value->data[0].v_double;
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if (F < 0.0) {
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F = -F;
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negative = TRUE;
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}
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gst_util_double_to_fraction (src, &n, &d);
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gst_value_set_fraction (dest_value, n, d);
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}
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V = F;
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/* initialize fractions with 1/0, 0/1 */
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N1 = 1;
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D1 = 0;
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N2 = 0;
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D2 = 1;
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N = 1;
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D = 1;
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static void
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gst_value_transform_float_fraction (const GValue * src_value,
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GValue * dest_value)
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{
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gfloat src = g_value_get_float (src_value);
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gint n, d;
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for (i = 0; i < MAX_TERMS; i++) {
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/* get next term */
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A = (gint) F; /* no floor() needed, F is always >= 0 */
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/* get new divisor */
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F = F - A;
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/* calculate new fraction in temp */
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N2 = N1 * A + N2;
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D2 = D1 * A + D2;
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/* guard against overflow */
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if (N2 > G_MAXINT || D2 > G_MAXINT) {
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break;
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}
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N = N2;
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D = D2;
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/* save last two fractions */
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N2 = N1;
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D2 = D1;
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N1 = N;
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D1 = D;
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/* quit if dividing by zero or close enough to target */
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if (F < MIN_DIVISOR || fabs (V - ((gdouble) N) / D) < MAX_ERROR) {
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break;
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}
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/* Take reciprocal */
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F = 1 / F;
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}
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/* fix for overflow */
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if (D == 0) {
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N = G_MAXINT;
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D = 1;
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}
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/* fix for negative */
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if (negative)
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N = -N;
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/* will also simplify */
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gst_value_set_fraction (dest_value, N, D);
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gst_util_double_to_fraction (src, &n, &d);
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gst_value_set_fraction (dest_value, n, d);
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}
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static void
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@ -3848,6 +3772,14 @@ gst_value_transform_fraction_double (const GValue * src_value,
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((double) src_value->data[1].v_int);
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}
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static void
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gst_value_transform_fraction_float (const GValue * src_value,
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GValue * dest_value)
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{
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dest_value->data[0].v_float = ((float) src_value->data[0].v_int) /
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((float) src_value->data[1].v_int);
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}
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static gint
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gst_value_compare_fraction (const GValue * value1, const GValue * value2)
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{
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@ -4354,8 +4286,12 @@ _gst_value_initialize (void)
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gst_value_transform_string_fraction);
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g_value_register_transform_func (GST_TYPE_FRACTION, G_TYPE_DOUBLE,
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gst_value_transform_fraction_double);
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g_value_register_transform_func (GST_TYPE_FRACTION, G_TYPE_FLOAT,
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gst_value_transform_fraction_float);
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g_value_register_transform_func (G_TYPE_DOUBLE, GST_TYPE_FRACTION,
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gst_value_transform_double_fraction);
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g_value_register_transform_func (G_TYPE_FLOAT, GST_TYPE_FRACTION,
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gst_value_transform_float_fraction);
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g_value_register_transform_func (GST_TYPE_DATE, G_TYPE_STRING,
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gst_value_transform_date_string);
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g_value_register_transform_func (G_TYPE_STRING, GST_TYPE_DATE,
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@ -1056,9 +1056,12 @@ EXPORTS
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gst_uri_protocol_is_valid
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gst_uri_type_get_type
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gst_util_array_binary_search
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gst_util_double_to_fraction
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gst_util_dump_mem
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gst_util_fraction_to_double
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gst_util_gdouble_to_guint64
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gst_util_get_timestamp
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gst_util_greatest_common_divisor
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gst_util_guint64_to_gdouble
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gst_util_seqnum_compare
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gst_util_seqnum_next
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