uhd: math: Replace wrap-frequency math with a single function

In multiple places in the UHD code, we were doing the same calculation
for a wrapped frequency (wrap it into the first Nyquist zone). This math
was using boost::math, too. Instead of editing every instance, we create
a new function, uhd::math::wrap_frequency(), and replace all of its
separate implementations with this function. The new function also no
longer relies on boost::math::sign.

1 files changed, 18 insertions, 0 deletions

diff --git a/host/include/uhd/utils/math.hpp b/host/include/uhd/utils/math.hpp
index 4918ddf2e..6c8fceae9 100644
--- a/host/include/uhd/utils/math.hpp
+++ b/host/include/uhd/utils/math.hpp
@@ -278,6 +278,24 @@ inline constexpr int sign(T x)
     return (T(0) < x) - (x < T(0));
 }
 
+//! Return a wrapped frequency that is the equivalent frequency in the first
+// Nyquist zone.
+//
+// Examples:
+// - Just above the sampling rate:
+//   wrap_frequency(250e6, 200e6) == 50e6
+// - Just outside the Nyquist zone:
+//   wrap_frequency(120e6, 200e6) == -80e6
+// - Also works for negative frequencies:
+//   wrap_frequency(-250e6, 200e6) == -50e6
+inline double wrap_frequency(const double requested_freq, const double rate)
+{
+    double freq = std::fmod(requested_freq, rate);
+    if (std::abs(freq) > rate / 2.0)
+        freq -= uhd::math::sign(freq) * rate;
+    return freq;
+}
+
 } // namespace math
 } // namespace uhd