1 files changed, 13 insertions, 0 deletions

diff --git a/apps/plugins/fft/math.c b/apps/plugins/fft/math.c
new file mode 100644
index 0000000000..c00804fcc8
--- /dev/null
+++ b/apps/plugins/fft/math.c
@@ -0,0 +1,13 @@
+#include "math.h"
+
+int64_t fsqrt64(int64_t a, unsigned int fracbits)
+{
+    int64_t b = a/2 + (1 << fracbits); /* initial approximation */
+    unsigned int n;
+    const unsigned int iterations = 3; /* very rough approximation */
+
+    for (n = 0; n < iterations; ++n)
+        b = (b + (((int64_t)(a) << fracbits)/b))/2;
+
+    return b;
+}