1 files changed, 77 insertions, 0 deletions
diff --git a/third_party/webrtc/src/webrtc/common_audio/signal_processing/spl_sqrt_floor.c b/third_party/webrtc/src/webrtc/common_audio/signal_processing/spl_sqrt_floor.c
new file mode 100644
index 00000000..370307a0
--- /dev/null
+++ b/third_party/webrtc/src/webrtc/common_audio/signal_processing/spl_sqrt_floor.c
@@ -0,0 +1,77 @@
+/*
+ * Written by Wilco Dijkstra, 1996. The following email exchange establishes the
+ * license.
+ *
+ * From: Wilco Dijkstra <Wilco.Dijkstra@ntlworld.com>
+ * Date: Fri, Jun 24, 2011 at 3:20 AM
+ * Subject: Re: sqrt routine
+ * To: Kevin Ma <kma@google.com>
+ * Hi Kevin,
+ * Thanks for asking. Those routines are public domain (originally posted to
+ * comp.sys.arm a long time ago), so you can use them freely for any purpose.
+ * Cheers,
+ * Wilco
+ *
+ * ----- Original Message -----
+ * From: "Kevin Ma" <kma@google.com>
+ * To: <Wilco.Dijkstra@ntlworld.com>
+ * Sent: Thursday, June 23, 2011 11:44 PM
+ * Subject: Fwd: sqrt routine
+ * Hi Wilco,
+ * I saw your sqrt routine from several web sites, including
+ * http://www.finesse.demon.co.uk/steven/sqrt.html.
+ * Just wonder if there's any copyright information with your Successive
+ * approximation routines, or if I can freely use it for any purpose.
+ * Thanks.
+ * Kevin
+ */
+
+// Minor modifications in code style for WebRTC, 2012.
+
+#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
+
+/*
+ * Algorithm:
+ * Successive approximation of the equation (root + delta) ^ 2 = N
+ * until delta < 1. If delta < 1 we have the integer part of SQRT (N).
+ * Use delta = 2^i for i = 15 .. 0.
+ *
+ * Output precision is 16 bits. Note for large input values (close to
+ * 0x7FFFFFFF), bit 15 (the highest bit of the low 16-bit half word)
+ * contains the MSB information (a non-sign value). Do with caution
+ * if you need to cast the output to int16_t type.
+ *
+ * If the input value is negative, it returns 0.
+ */
+
+#define WEBRTC_SPL_SQRT_ITER(N)                 \
+  try1 = root + (1 << (N));                     \
+  if (value >= try1 << (N))                     \
+  {                                             \
+    value -= try1 << (N);                       \
+    root |= 2 << (N);                           \
+  }
+
+int32_t WebRtcSpl_SqrtFloor(int32_t value)
+{
+  int32_t root = 0, try1;
+
+  WEBRTC_SPL_SQRT_ITER (15);
+  WEBRTC_SPL_SQRT_ITER (14);
+  WEBRTC_SPL_SQRT_ITER (13);
+  WEBRTC_SPL_SQRT_ITER (12);
+  WEBRTC_SPL_SQRT_ITER (11);
+  WEBRTC_SPL_SQRT_ITER (10);
+  WEBRTC_SPL_SQRT_ITER ( 9);
+  WEBRTC_SPL_SQRT_ITER ( 8);
+  WEBRTC_SPL_SQRT_ITER ( 7);
+  WEBRTC_SPL_SQRT_ITER ( 6);
+  WEBRTC_SPL_SQRT_ITER ( 5);
+  WEBRTC_SPL_SQRT_ITER ( 4);
+  WEBRTC_SPL_SQRT_ITER ( 3);
+  WEBRTC_SPL_SQRT_ITER ( 2);
+  WEBRTC_SPL_SQRT_ITER ( 1);
+  WEBRTC_SPL_SQRT_ITER ( 0);
+
+  return root >> 1;
+}