[time] Define an API for getting the current time

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/null_time.h

@@ -0,0 +1,23 @@
+#ifndef _IPXE_NULL_TIME_H
+#define _IPXE_NULL_TIME_H
+
+/** @file
+ *
+ * Nonexistent time source
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#ifdef TIME_NULL
+#define TIME_PREFIX_null
+#else
+#define TIME_PREFIX_null __null_
+#endif
+
+static inline __always_inline time_t
+TIME_INLINE ( null, time_now ) ( void ) {
+	return 0;
+}
+
+#endif /* _IPXE_NULL_TIME_H */

src/include/ipxe/time.h

@@ -0,0 +1,58 @@
+#ifndef _IPXE_TIME_H
+#define _IPXE_TIME_H
+
+/** @file
+ *
+ * Time source
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <sys/time.h>
+#include <ipxe/api.h>
+#include <config/time.h>
+
+/**
+ * Calculate static inline time API function name
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @ret _subsys_func	Subsystem API function
+ */
+#define TIME_INLINE( _subsys, _api_func ) \
+	SINGLE_API_INLINE ( TIME_PREFIX_ ## _subsys, _api_func )
+
+/**
+ * Provide a time API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @v _func		Implementing function
+ */
+#define PROVIDE_TIME( _subsys, _api_func, _func ) \
+	PROVIDE_SINGLE_API ( TIME_PREFIX_ ## _subsys, _api_func, _func )
+
+/**
+ * Provide a static inline time API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ */
+#define PROVIDE_TIME_INLINE( _subsys, _api_func ) \
+	PROVIDE_SINGLE_API_INLINE ( TIME_PREFIX_ ## _subsys, _api_func )
+
+/* Include all architecture-independent time API headers */
+#include <ipxe/null_time.h>
+
+/* Include all architecture-dependent time API headers */
+#include <bits/time.h>
+
+/**
+ * Get current time in seconds
+ *
+ * @ret time		Time, in seconds
+ */
+time_t time_now ( void );
+
+#endif /* _IPXE_TIME_H */

src/include/time.h

@@ -7,6 +7,7 @@
  */
 
 #include <sys/time.h>
+#include <ipxe/time.h>
 
 /** Broken-down time */
 struct tm {
@@ -30,6 +31,21 @@ struct tm {
 	int tm_isdst;
 };
 
+/**
+ * Get current time in seconds since the Epoch
+ *
+ * @v t			Time to fill in, or NULL
+ * @ret time		Current time
+ */
+static inline time_t time ( time_t *t ) {
+	time_t now;
+
+	now = time_now();
+	if ( t )
+		*t = now;
+	return now;
+}
+
 extern time_t mktime ( struct tm *tm );
 
 #endif /* _TIME_H */