Initial filter chain and filter configuration for outputs.

src/conf.h

@@ -42,6 +42,7 @@
 #define CONF_PASSWORD                   "password"
 #define CONF_DEFAULT_PERMS              "default_permissions"
 #define CONF_AUDIO_OUTPUT               "audio_output"
+#define CONF_AUDIO_FILTER               "filter"
 #define CONF_AUDIO_OUTPUT_FORMAT        "audio_output_format"
 #define CONF_MIXER_TYPE                 "mixer_type"
 #define CONF_REPLAYGAIN                 "replaygain"
@@ -73,6 +74,8 @@
 #define DEFAULT_PLAYLIST_MAX_LENGTH (1024*16)
 #define DEFAULT_PLAYLIST_SAVE_ABSOLUTE_PATHS false
 
+#define MAX_FILTER_CHAIN_LENGTH 255
+
 struct block_param {
 	char *name;
 	char *value;

src/filter/chain_filter_plugin.c

@@ -18,12 +18,14 @@
  */
 
 #include "config.h"
+#include "conf.h"
 #include "filter/chain_filter_plugin.h"
 #include "filter_plugin.h"
 #include "filter_internal.h"
 #include "filter_registry.h"
 
 #include <assert.h>
+#include <string.h>
 
 struct filter_chain {
 	/** the base class */
@@ -176,3 +178,100 @@ filter_chain_append(struct filter *_chain, struct filter *filter)
 
 	chain->children = g_slist_append(chain->children, filter);
 }
+
+/**
+ * Find the "filter" configuration block for the specified name.
+ *
+ * @param filter_template_name the name of the filter template
+ * @return the configuration block, or NULL if none was configured
+ */
+static const struct config_param *
+filter_plugin_config(const char *filter_template_name)
+{
+	const struct config_param *param = NULL;
+
+	while ((param = config_get_next_param(CONF_AUDIO_FILTER, param)) != NULL) {
+		const char *name =
+			config_get_block_string(param, "name", NULL);
+		if (name == NULL)
+			g_error("filter configuration without 'name' name in line %d",
+				param->line);
+
+		if (strcmp(name, filter_template_name) == 0)
+			return param;
+	}
+
+	return NULL;
+}
+
+/**
+ * Builds a filter chain from a configuration string on the form
+ * "name1, name2, name3, ..." by looking up each name among the
+ * configured filter sections.
+ * @param chain the chain to append filters on
+ * @param spec the filter chain specification
+ * @return the number of filters which were successfully added
+ */
+unsigned int
+filter_chain_parse(struct filter *chain, const char *spec) {
+
+	// Split on comma
+	gchar** tokens = g_strsplit_set(spec, ",", 255);
+
+	int added_filters = 0;
+
+	// Add each name to the filter chain by instantiating an actual filter
+	char **template_names = tokens;
+	while (*template_names != NULL) {
+		const char *plugin_name;
+		const struct filter_plugin *fp;
+		struct filter *f;
+		const struct config_param *cfg;
+
+		// Squeeze whitespace
+		g_strstrip(*template_names);
+
+		cfg = filter_plugin_config(*template_names);
+		if (cfg == NULL) {
+			g_error("Unable to locate filter template %s",
+				*template_names);
+			++template_names;
+			continue;
+		}
+
+		// Figure out what kind of a plugin that is
+		plugin_name = config_get_block_string(cfg, "plugin", NULL);
+		if (plugin_name == NULL) {
+			g_error("filter configuration without 'plugin' at line %d",
+				cfg->line);
+			++template_names;
+			continue;
+		}
+
+		// Instantiate one of those filter plugins with the template name as a hint
+		fp = filter_plugin_by_name(plugin_name);
+		if (fp == NULL) {
+			g_error("filter plugin not found: %s",
+				plugin_name);
+			++template_names;
+			continue;
+		}
+
+		f = filter_new(fp, cfg, NULL);
+		if (f == NULL) {
+			g_error("filter plugin initialization failed: %s",
+				plugin_name);
+			++template_names;
+			continue;
+		}
+
+		filter_chain_append(chain, f);
+		++added_filters;
+
+		++template_names;
+	}
+
+	g_strfreev(tokens);
+
+	return added_filters;
+}

src/filter/chain_filter_plugin.h

@@ -45,4 +45,16 @@ filter_chain_new(void);
 void
 filter_chain_append(struct filter *chain, struct filter *filter);
 
+/**
+ * Builds a filter chain from a configuration string on the form
+ * "name1, name2, name3, ..." by looking up each name among the
+ * configured filter sections. If no filters are specified, a
+ * null filter is automatically appended.
+ * @param chain the chain to append filters on
+ * @param spec the filter chain specification
+ * @return the number of filters which were successfully added
+ */
+unsigned int
+filter_chain_parse(struct filter *chain, const char *spec);
+
 #endif

src/output_init.c

@@ -41,6 +41,7 @@
 #define AUDIO_OUTPUT_TYPE	"type"
 #define AUDIO_OUTPUT_NAME	"name"
 #define AUDIO_OUTPUT_FORMAT	"format"
+#define AUDIO_FILTERS		"filters"
 
 static const struct audio_output_plugin *
 audio_output_detect(GError **error)
@@ -190,6 +191,9 @@ audio_output_init(struct audio_output *ao, const struct config_param *param,
 
 	ao->filter = filter_chain_new();
 	assert(ao->filter != NULL);
+	filter_chain_parse(ao->filter,
+	                   config_get_block_string(param, AUDIO_FILTERS, "")
+	);
 
 	ao->thread = NULL;
 	ao->command = AO_COMMAND_NONE;