m_config: support auto-allocated sub-structs

Given your option struct has a field that is a pointer to another
struct, this commit allows you to declare options that write into that
other struct. The code in m_config will dereference the pointer field
on its own if such an option is accessed. If the field is NULL on
initialization of the containing m_config, the struct is automatically
allocated.

OPT_SUBSTRUCT() can be used to declare such a field.
struct m_sub_options is used to describe the pointed-to struct, and
includes size and defaults if the struct has to be allocated by
m_config.

1 files changed, 17 insertions, 0 deletions

diff --git a/m_option.h b/m_option.h
index e0321d1de1..ab83027a85 100644
--- a/m_option.h
+++ b/m_option.h
@@ -52,6 +52,7 @@ extern const m_option_type_t m_option_type_print;
 extern const m_option_type_t m_option_type_print_func;
 extern const m_option_type_t m_option_type_print_func_param;
 extern const m_option_type_t m_option_type_subconfig;
+extern const m_option_type_t m_option_type_subconfig_struct;
 extern const m_option_type_t m_option_type_imgfmt;
 extern const m_option_type_t m_option_type_afmt;
 
@@ -148,6 +149,12 @@ struct m_opt_choice_alternatives {
     int value;
 };
 
+// m_option.priv points to this if M_OPT_TYPE_USE_SUBSTRUCT is used
+struct m_sub_options {
+    const struct m_option *opts;
+    size_t size;
+    const void *defaults;
+};
 
 // FIXME: backward compatibility
 #define CONF_TYPE_FLAG          (&m_option_type_flag)
@@ -338,6 +345,10 @@ struct m_option {
 // takes no parameter.
 #define M_OPT_TYPE_OLD_SYNTAX_NO_PARAM  (1 << 3)
 
+// modify M_OPT_TYPE_HAS_CHILD so that m_option::p points to
+// struct m_sub_options, instead of a direct m_option array.
+#define M_OPT_TYPE_USE_SUBSTRUCT        (1 << 4)
+
 ///////////////////////////// Parser flags /////////////////////////////////
 
 // On success parsers return the number of arguments consumed: 0 or 1.
@@ -461,6 +472,12 @@ static inline void m_option_free(const m_option_t *opt, void *dst)
 #define OPT_CHOICE_(optname, varname, flags, choices, ...) OPT_GENERAL(optname, varname, flags, .priv = (void *)&(const struct m_opt_choice_alternatives[]){OPT_HELPER_REMOVEPAREN choices, {NULL}}, __VA_ARGS__)
 #define OPT_TIME(...) OPT_GENERAL(__VA_ARGS__, .type = &m_option_type_time)
 
+// subconf must have the type struct m_sub_options.
+// flagv should be M_OPT_MERGE or M_OPT_FLATTEN.
+// varname refers to the field, that must be a pointer to a field described by
+// the subconf struct.
+#define OPT_SUBSTRUCT(varname, subconf, flagv) OPT_GENERAL("-", varname, flagv, .type = &m_option_type_subconfig_struct, .priv = (void*)&subconf)
+
 #define OPT_BASE_STRUCT struct MPOpts
 
 #endif /* MPLAYER_M_OPTION_H */