From c83a3d6e2e5fef389bb5fa64610dc348db7fdd61 Mon Sep 17 00:00:00 2001
From: "bjornv@google.com"
 <bjornv@google.com@4adac7df-926f-26a2-2b94-8c16560cd09d>
Date: Thu, 7 Jul 2011 12:34:44 +0000
Subject: [PATCH] Added the new sqrt routine as a separate function. Review
 URL: http://webrtc-codereview.appspot.com/55004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@175 4adac7df-926f-26a2-2b94-8c16560cd09d
---
 .../interface/signal_processing_library.h     | 18 +++++++
 .../main/source/spl.gyp                       |  1 +
 .../main/source/spl_sqrt_floor.c              | 53 +++++++++++++++++++
 .../main/test/unit_test/unit_test.cc          |  1 +
 4 files changed, 73 insertions(+)
 create mode 100644 src/common_audio/signal_processing_library/main/source/spl_sqrt_floor.c

diff --git a/src/common_audio/signal_processing_library/main/interface/signal_processing_library.h b/src/common_audio/signal_processing_library/main/interface/signal_processing_library.h
index b59a236b4..414e0450c 100644
--- a/src/common_audio/signal_processing_library/main/interface/signal_processing_library.h
+++ b/src/common_audio/signal_processing_library/main/interface/signal_processing_library.h
@@ -379,6 +379,7 @@ WebRtc_Word16 WebRtcSpl_RandUArray(WebRtc_Word16* vector,
 
 // Math functions
 WebRtc_Word32 WebRtcSpl_Sqrt(WebRtc_Word32 value);
+WebRtc_Word32 WebRtcSpl_SqrtFloor(WebRtc_Word32 value);
 
 // Divisions. Implementations collected in division_operations.c and
 // descriptions at bottom of this file.
@@ -1319,6 +1320,23 @@ void WebRtcSpl_SynthesisQMF(const WebRtc_Word16* low_band,
 // Return value     : Result of the sqrt calculation
 //
 
+//
+// WebRtcSpl_SqrtFloor(...)
+//
+// Returns the square root of the input value |value|. The precision of this
+// function is rounding down integer precision, i.e., sqrt(8) gives 2 as answer.
+// If |value| is a negative number then 0 is returned.
+//
+// Algorithm:
+//
+// An iterative 4 cylce/bit routine
+//
+// Input:
+//      - value     : Value to calculate sqrt of
+//
+// Return value     : Result of the sqrt calculation
+//
+
 //
 // WebRtcSpl_DivU32U16(...)
 //
diff --git a/src/common_audio/signal_processing_library/main/source/spl.gyp b/src/common_audio/signal_processing_library/main/source/spl.gyp
index 2dfa0fc9b..9c052fc60 100644
--- a/src/common_audio/signal_processing_library/main/source/spl.gyp
+++ b/src/common_audio/signal_processing_library/main/source/spl.gyp
@@ -65,6 +65,7 @@
         'sin_table.c',
         'sin_table_1024.c',
         'spl_sqrt.c',
+        'spl_sqrt_floor.c',
         'spl_version.c',
         'splitting_filter.c',
         'sqrt_of_one_minus_x_squared.c',
diff --git a/src/common_audio/signal_processing_library/main/source/spl_sqrt_floor.c b/src/common_audio/signal_processing_library/main/source/spl_sqrt_floor.c
new file mode 100644
index 000000000..aa36459ec
--- /dev/null
+++ b/src/common_audio/signal_processing_library/main/source/spl_sqrt_floor.c
@@ -0,0 +1,53 @@
+/*
+ *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+/*
+ * This file contains the function WebRtcSpl_SqrtFloor().
+ * The description header can be found in signal_processing_library.h
+ *
+ */
+
+#include "signal_processing_library.h"
+
+#define WEBRTC_SPL_SQRT_ITER(N)                 \
+  try1 = root + (1 << (N));                     \
+  if (value >= try1 << (N))                     \
+  {                                             \
+    value -= try1 << (N);                       \
+    root |= 2 << (N);                           \
+  }
+
+// (out) Square root of input parameter
+WebRtc_Word32 WebRtcSpl_SqrtFloor(WebRtc_Word32 value)
+{
+    // new routine for performance, 4 cycles/bit in ARM
+    // output precision is 16 bits
+
+    WebRtc_Word32 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;
+}
diff --git a/src/common_audio/signal_processing_library/main/test/unit_test/unit_test.cc b/src/common_audio/signal_processing_library/main/test/unit_test/unit_test.cc
index 19cc553f6..5adc33913 100644
--- a/src/common_audio/signal_processing_library/main/test/unit_test/unit_test.cc
+++ b/src/common_audio/signal_processing_library/main/test/unit_test/unit_test.cc
@@ -147,6 +147,7 @@ TEST_F(SplTest, MathOperationsTest) {
     WebRtc_Word32 den = -5;
     WebRtc_UWord16 denU = 5;
     EXPECT_EQ(10, WebRtcSpl_Sqrt(A));
+    EXPECT_EQ(10, WebRtcSpl_SqrtFloor(A));
 
 
     EXPECT_EQ(-91772805, WebRtcSpl_DivResultInQ31(den, num));