utilities.c: Add utility function iio_read_counter_us()

This function can be used to get the value of a counter with a precision
of a microsecond. The value returned is not properly defined, and as
such does not allow to represent a specific point in time, but allows to
compute periods and delays.

Signed-off-by: Paul Cercueil <[email protected]>

iio-private.h

@@ -264,6 +264,7 @@ char *iio_strndup(const char *str, size_t n);
 char *iio_strtok_r(char *str, const char *delim, char **saveptr);
 size_t iio_strlcpy(char * __restrict dst, const char * __restrict src, size_t dsize);
 char * iio_getenv (char * envvar);
+uint64_t iio_read_counter_us(void);
 
 int iio_context_add_device(struct iio_context *ctx, struct iio_device *dev);
 

utilities.c

@@ -20,6 +20,12 @@
 #include <stdlib.h>
 #include <string.h>
 
+#ifdef _WIN32
+#include <Windows.h>
+#else
+#include <time.h>
+#endif
+
 #if defined(_WIN32) || \
 		(defined(__APPLE__) && defined(__MACH__)) || \
 		(defined(__USE_XOPEN2K8) && \
@@ -359,3 +365,25 @@ ssize_t __iio_printf iio_snprintf(char *buf, size_t len, const char *fmt, ...)
 
 	return (ssize_t)ret;
 }
+
+uint64_t iio_read_counter_us(void)
+{
+	uint64_t value;
+
+#ifdef _WIN32
+	LARGE_INTEGER freq, cnt;
+
+	QueryPerformanceFrequency(&freq);
+	QueryPerformanceCounter(&cnt);
+
+	value = (1000000 * cnt.QuadPart) / freq.QuadPart;
+#else
+	struct timespec ts;
+
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+
+	value = ts.tv_sec * 1000000ull + (uint64_t)ts.tv_nsec / 1000ull;
+#endif
+
+	return value;
+}