From 8d36eb43da27bef1e7bc3d626f46cb4c92ca2a41 Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@tuebingen.mpg.de>
Date: Thu, 30 Aug 2018 22:09:54 +0200
Subject: [PATCH] mood: Make "duration" a new keyword for the mood grammar.

The new keyword makes it possible to define moods which impose a
constraint on the duration of the admissible files. For example,
the expression

	duration < 120 * 1000

selects only files which are shorter than two minutes.

The implementation is pretty simple.
---
 mp.c          | 21 +++++++++++++++++++++
 mp.h          |  1 +
 web/manual.md |  1 +
 yy/mp.lex     |  1 +
 yy/mp.y       |  5 +++++
 5 files changed, 29 insertions(+)

diff --git a/mp.c b/mp.c
index 416b4f92..b5fa9cac 100644
--- a/mp.c
+++ b/mp.c
@@ -389,6 +389,27 @@ MP_AFHI(frequency)
 MP_AFHI(channels)
 /** \endcond */
 
+/**
+ * Return the duration of the audio file from the afh info structure.
+ *
+ * \param ctx See \ref mp_path().
+ *
+ * The duration is computed by multiplying the number of chunks and the
+ * duration of one chunk.
+ *
+ * \return The approximate number of milliseconds.
+ */
+int64_t mp_duration(struct mp_context *ctx)
+{
+	struct timeval tmp;
+	int ret = get_afhi(ctx);
+
+	if (ret < 0)
+		return 0;
+	tv_scale(ctx->afhi.chunks_total, &ctx->afhi.chunk_tv, &tmp);
+	return tv2ms(&tmp);
+}
+
 /**
  * Define a function which extracts and returns the value of a meta tag.
  *
diff --git a/mp.h b/mp.h
index febbe324..891bfb05 100644
--- a/mp.h
+++ b/mp.h
@@ -139,6 +139,7 @@ bool mp_is_set(const char *attr, struct mp_context *ctx);
 char *mp_path(struct mp_context *ctx);
 int64_t mp_year(struct mp_context *ctx);
 int64_t mp_num_attributes_set(struct mp_context *ctx);
+int64_t mp_duration(struct mp_context *ctx);
 
 /* Generated with MP_AFSI() */
 /** \cond MP_AFSI */
diff --git a/web/manual.md b/web/manual.md
index db28a699..d73263b3 100644
--- a/web/manual.md
+++ b/web/manual.md
@@ -1023,6 +1023,7 @@ Keyword              |    Type | Semantic value
 `bitrate`            | integer | The average bitrate
 `frequency`          | integer | The output sample rate
 `channels`           | integer | The number of channels
+`duration`           | integer | The number of milliseconds
 `is_set("foo")`      | boolean | True if attribute "foo" is set.
 
 [\*] For most audio formats, the year tag is stored as a string. It
diff --git a/yy/mp.lex b/yy/mp.lex
index 2dbe21b7..4a53db27 100644
--- a/yy/mp.lex
+++ b/yy/mp.lex
@@ -74,6 +74,7 @@ lyrics_id {return LYRICS_ID;}
 bitrate {return BITRATE;}
 frequency {return FREQUENCY;}
 channels {return CHANNELS;}
+duration {return DURATION;}
 true {return TRUE;}
 false {return FALSE;}
 
diff --git a/yy/mp.y b/yy/mp.y
index 0f2c9cb8..06d76101 100644
--- a/yy/mp.y
+++ b/yy/mp.y
@@ -210,6 +210,9 @@ static int eval_node(struct mp_ast_node *node, struct mp_context *ctx,
 	case CHANNELS:
 		result->intval= mp_channels(ctx);
 		return ST_INTVAL;
+	case DURATION:
+		result->intval= mp_duration(ctx);
+		return ST_INTVAL;
 	/* bools */
 	case IS_SET:
 		arg = node->children[0]->sv.strval;
@@ -327,6 +330,7 @@ bool mp_eval_ast(struct mp_ast_node *root, struct mp_context *ctx)
 %token <node> BITRATE
 %token <node> FREQUENCY
 %token <node> CHANNELS
+%token <node> DURATION
 %token <node> FALSE TRUE
 
 /* keywords without semantic value */
@@ -377,6 +381,7 @@ exp: NUM {$$ = $1;}
 	| BITRATE {$$ = mp_new_ast_leaf_node(BITRATE);}
 	| FREQUENCY {$$ = mp_new_ast_leaf_node(FREQUENCY);}
 	| CHANNELS {$$ = mp_new_ast_leaf_node(CHANNELS);}
+	| DURATION {$$ = mp_new_ast_leaf_node(DURATION);}
 ;
 
 boolexp: IS_SET '(' STRING_LITERAL ')' {$$ = ast_node_new_unary(IS_SET, $3);}
-- 
2.30.2