[FFmpeg-devel] [PATCH 1/3] avutil/eval: separate AVExpr state to a new AVExprState struct
Michael Niedermayer
michael at niedermayer.cc
Mon Dec 30 21:43:33 EET 2019
On Sun, Dec 29, 2019 at 04:46:12PM +0100, Marton Balint wrote:
>
>
> On Sun, 29 Dec 2019, Michael Niedermayer wrote:
>
> >On Sat, Dec 28, 2019 at 03:46:23PM +0100, Marton Balint wrote:
> >>Also add helper functions to allocate and free such a struct, and make it
> >>usable by providing a new av_eval_expr2 function for which you can specify a
> >>custom AVExprState.
> >>
> >>Signed-off-by: Marton Balint <cus at passwd.hu>
> >>---
> >> doc/APIchanges | 3 +++
> >> libavutil/eval.c | 31 +++++++++++++++++++++++++------
> >> libavutil/eval.h | 27 +++++++++++++++++++++++++++
> >> libavutil/version.h | 2 +-
> >> 4 files changed, 56 insertions(+), 7 deletions(-)
> >>
> >>diff --git a/doc/APIchanges b/doc/APIchanges
> >>index 3c24dc6fbc..e4ad364ed9 100644
> >>--- a/doc/APIchanges
> >>+++ b/doc/APIchanges
> >>@@ -15,6 +15,9 @@ libavutil: 2017-10-21
> >>
> >> API changes, most recent first:
> >>
> >>+2020-01-xx - xxxxxxxxxx - lavu 56.39.100 - eval.h
> >>+ Add av_expr_eval2, av_expr_state_alloc, av_expr_state_free
> >>+
> >> 2019-12-27 - xxxxxxxxxx - lavu 56.38.100 - eval.h
> >> Add av_expr_count_func().
> >>
> >>diff --git a/libavutil/eval.c b/libavutil/eval.c
> >>index d527f6a9d0..86fb634fd8 100644
> >>--- a/libavutil/eval.c
> >>+++ b/libavutil/eval.c
> >>@@ -173,7 +173,11 @@ struct AVExpr {
> >> double (*func2)(void *, double, double);
> >> } a;
> >> struct AVExpr *param[3];
> >>- double *var;
> >>+ AVExprState *state;
> >>+};
> >>+
> >>+struct AVExprState {
> >>+ double vars[VARS];
> >> };
> >>
> >> static double etime(double v)
> >>@@ -333,13 +337,23 @@ static double eval_expr(Parser *p, AVExpr *e)
> >>
> >> static int parse_expr(AVExpr **e, Parser *p);
> >>
> >>+AVExprState *av_expr_state_alloc(void)
> >>+{
> >>+ return av_mallocz(sizeof(AVExprState));
> >>+}
> >>+
> >>+void av_expr_state_free(AVExprState **ps)
> >>+{
> >>+ av_freep(ps);
> >>+}
> >>+
> >> void av_expr_free(AVExpr *e)
> >> {
> >> if (!e) return;
> >> av_expr_free(e->param[0]);
> >> av_expr_free(e->param[1]);
> >> av_expr_free(e->param[2]);
> >>- av_freep(&e->var);
> >>+ av_expr_state_free(&e->state);
> >> av_freep(&e);
> >> }
> >>
> >>@@ -724,8 +738,8 @@ int av_expr_parse(AVExpr **expr, const char *s,
> >> ret = AVERROR(EINVAL);
> >> goto end;
> >> }
> >>- e->var= av_mallocz(sizeof(double) *VARS);
> >>- if (!e->var) {
> >>+ e->state = av_expr_state_alloc();
> >>+ if (!e->state) {
> >> ret = AVERROR(ENOMEM);
> >> goto end;
> >> }
> >>@@ -763,16 +777,21 @@ int av_expr_count_func(AVExpr *e, unsigned *counter, int size, int arg)
> >> return expr_count(e, counter, size, ((int[]){e_const, e_func1, e_func2})[arg]);
> >> }
> >>
> >>-double av_expr_eval(AVExpr *e, const double *const_values, void *opaque)
> >>+double av_expr_eval2(AVExpr *e, AVExprState *s, const double *const_values, void *opaque)
> >> {
> >> Parser p = { 0 };
> >>- p.var= e->var;
> >>+ p.var = s ? s->vars : e->state->vars;
> >>
> >> p.const_values = const_values;
> >> p.opaque = opaque;
> >> return eval_expr(&p, e);
> >> }
> >>
> >>+double av_expr_eval(AVExpr *e, const double *const_values, void *opaque)
> >>+{
> >>+ return av_expr_eval2(e, NULL, const_values, opaque);
> >>+}
> >>+
> >> int av_expr_parse_and_eval(double *d, const char *s,
> >> const char * const *const_names, const double *const_values,
> >> const char * const *func1_names, double (* const *funcs1)(void *, double),
> >>diff --git a/libavutil/eval.h b/libavutil/eval.h
> >>index 068c62cdab..8bd1592f6c 100644
> >>--- a/libavutil/eval.h
> >>+++ b/libavutil/eval.h
> >>@@ -29,6 +29,7 @@
> >> #include "avutil.h"
> >>
> >> typedef struct AVExpr AVExpr;
> >>+typedef struct AVExprState AVExprState;
> >>
> >> /**
> >> * Parse and evaluate an expression.
> >>@@ -86,6 +87,22 @@ int av_expr_parse(AVExpr **expr, const char *s,
> >> */
> >> double av_expr_eval(AVExpr *e, const double *const_values, void *opaque);
> >>
> >>+/**
> >>+ * Evaluate a previously parsed expression using a custom state.
> >>+ *
> >>+ * Some expressions can use stateful functions, like random(), st() and ld().
> >>+ * With this function you can provide your own state to the evaluator instead
> >>+ * of using the internal state of the AVExpr. This makes it possible to use the
> >>+ * same AVExpr in multiple threads each with their own AVExprState avoiding
> >>+ * unprotected concurrent access of the internal AVExpr state.
> >>+ *
> >>+ * @param s the state of the expression, if NULL, the internal state of AVExpr will be used
> >>+ * @param const_values a zero terminated array of values for the identifiers from av_expr_parse() const_names
> >>+ * @param opaque a pointer which will be passed to all functions from funcs1 and funcs2
> >>+ * @return the value of the expression
> >>+ */
> >>+double av_expr_eval2(AVExpr *e, AVExprState *s, const double *const_values, void *opaque);
> >>+
> >> /**
> >> * Track the presence of variables and their number of occurrences in a parsed expression
> >> *
> >>@@ -134,4 +151,14 @@ void av_expr_free(AVExpr *e);
> >> */
> >> double av_strtod(const char *numstr, char **tail);
> >>
> >>+/**
> >>+ * Allocate a new AVExprState struct
> >>+ */
> >>+AVExprState *av_expr_state_alloc(void);
> >
> >maybe this should have a double [] argument so the caller can set the
> >initial variables (or pass NULL if not)
>
> Maybe it is better to simply make the AVExprState struct public if
> setting/getting state manually is something we want to support. What do you
> think?
if its still extendible, then it may be a good idea, yes
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
"I am not trying to be anyone's saviour, I'm trying to think about the
future and not be sad" - Elon Musk
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20191230/82c9f252/attachment.sig>
More information about the ffmpeg-devel
mailing list