Add libusb_has_capability() API function

Since it is currently not planned to change the filename of the libusb
library between libusb-1.0 versions at least on Windows systems it's
important to have a capability API.

Currently there exists only one capability; LIBUSB_CAP_HAS_CAPABILITY,
which tests support for the libusb_has_capability() API.

3 files changed, 29 insertions, 0 deletions

diff --git a/libusb/core.c b/libusb/core.c
index 5834bea..0d05333 100644
--- a/libusb/core.c
+++ b/libusb/core.c
@@ -1664,6 +1664,22 @@ void API_EXPORTED libusb_exit(struct libusb_context *ctx)
 	free(ctx);
 }
 
+/** \ingroup misc
+ * Check at runtime if the loaded library has a given capability.
+ *
+ * \param capability the \ref libusb_capability to check for
+ * \returns 1 if the running library has the capability, 0 otherwise
+ */
+int API_EXPORTED libusb_has_capability(uint32_t capability)
+{
+	enum libusb_capability cap = capability;
+	switch (cap) {
+	case LIBUSB_CAP_HAS_CAPABILITY:
+		return 1;
+	}
+	return 0;
+}
+
 void usbi_log_v(struct libusb_context *ctx, enum usbi_log_level level,
 	const char *function, const char *format, va_list args)
 {
diff --git a/libusb/libusb-1.0.def b/libusb/libusb-1.0.def
index 4eef912..54b0622 100644
--- a/libusb/libusb-1.0.def
+++ b/libusb/libusb-1.0.def
@@ -70,6 +70,8 @@ EXPORTS
   libusb_handle_events_timeout@8 = libusb_handle_events_timeout
   libusb_handle_events_timeout_completed
   libusb_handle_events_timeout_completed@12 = libusb_handle_events_timeout_completed
+  libusb_has_capability
+  libusb_has_capability@4 = libusb_has_capability
   libusb_init
   libusb_init@4 = libusb_init
   libusb_interrupt_transfer
diff --git a/libusb/libusb.h b/libusb/libusb.h
index 3b7f92a..ae09907 100644
--- a/libusb/libusb.h
+++ b/libusb/libusb.h
@@ -885,9 +885,20 @@ struct libusb_transfer {
 	;
 };
 
+/** \ingroup misc
+ * Capabilities supported by this instance of libusb. Test if the loaded
+ * library supports a given capability by calling
+ * \ref libusb_has_capability().
+ */
+enum libusb_capability {
+	/** The libusb_has_capability() API is available. */
+	LIBUSB_CAP_HAS_CAPABILITY = 0,
+};
+
 int LIBUSB_CALL libusb_init(libusb_context **ctx);
 void LIBUSB_CALL libusb_exit(libusb_context *ctx);
 void LIBUSB_CALL libusb_set_debug(libusb_context *ctx, int level);
+int LIBUSB_CALL libusb_has_capability(uint32_t capability);
 
 ssize_t LIBUSB_CALL libusb_get_device_list(libusb_context *ctx,
 	libusb_device ***list);