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-rw-r--r--common/cosinetables.cpp36
-rw-r--r--common/cosinetables.h22
-rw-r--r--common/sinetables.cpp40
-rw-r--r--common/sinetables.h16
4 files changed, 87 insertions, 27 deletions
diff --git a/common/cosinetables.cpp b/common/cosinetables.cpp
index 4bee1f24ea..42c6e4e05a 100644
--- a/common/cosinetables.cpp
+++ b/common/cosinetables.cpp
@@ -32,17 +32,35 @@ CosineTable::CosineTable(int bitPrecision) {
_bitPrecision = bitPrecision;
- int m = 1 << _bitPrecision;
- double freq = 2 * M_PI / m;
- _table = new float[m / 2];
+ _nPoints = 1 << _bitPrecision;
+ _radResolution = 2.0 * M_PI / _nPoints;
+ _refSize = _nPoints / 4;
+ _table = new float[_nPoints / 2];
- // Table contains cos(2*pi*i/m) for 0<=i<m/4,
- // followed by 3m/4<=i<m
- for (int i = 0; i <= m / 4; i++)
- _table[i] = cos(i * freq);
+ // Table contains cos(2*pi*i/_nPoints) for 0<=i<=_nPoints/4,
+ // followed by 3_nPoints/4<=i<_nPoints
+ for (int i = 0; i <= _nPoints / 4; i++)
+ _table[i] = cos(i * _radResolution);
- for (int i = 1; i < m / 4; i++)
- _table[m / 2 - i] = _table[i];
+ for (int i = 1; i < _nPoints / 4; i++)
+ _table[_nPoints / 2 - i] = _table[i];
+}
+
+float CosineTable::at(int index) const {
+ assert((index >= 0) && (index < _nPoints));
+ if (index < _refSize)
+ // [0,pi/2)
+ return _table[index];
+ if ((index > _refSize) && (index < 2 * _refSize))
+ // (pi/2,pi)
+ return -_table[2 * _refSize - index];
+ if ((index >= 2 * _refSize) && (index < 3 * _refSize))
+ // [pi,3/2pi)
+ return -_table[index - 2 * _refSize];
+ if ((index > 3 * _refSize) && (index < _nPoints))
+ // (3/2pi,2pi)
+ return _table[_nPoints - index];
+ return 0.0f; // cos(pi/2) and cos(3pi/2) = 0
}
CosineTable::~CosineTable() {
diff --git a/common/cosinetables.h b/common/cosinetables.h
index 0ff01e40d6..c08bb4cddd 100644
--- a/common/cosinetables.h
+++ b/common/cosinetables.h
@@ -39,22 +39,32 @@ public:
* Get pointer to table.
*
* This table contains 2^bitPrecision/2 entries.
+ * Prefer to use at()
* The layout of this table is as follows:
- * - Entries 0 up to (excluding) 2^bitPrecision/4:
- * cos(0) till (excluding) cos(1/2*pi)
- * - Entries 2^bitPrecision/4 up to (excluding) 2^bitPrecision/2:
- * cos(3/2*pi) till (excluding) cos(2*pi)
+ * - Entries 0 up to (including) 2^bitPrecision/4:
+ * cos(0) till (including) cos(1/2*pi)
+ * - Entries (excluding) 2^bitPrecision/4 up to 2^bitPrecision/2:
+ * (excluding) cos(3/2*pi) till (excluding) cos(2*pi)
*/
const float *getTable() { return _table; }
/**
- * Get pointer to table
+ * Returns cos(2*pi * index / 2^bitPrecision )
+ * Index must be in range [0,2^bitPrecision-1]
*/
- int getPrecision() { return _bitPrecision; }
+ float at(int index) const;
+
+ /**
+ * Get bit precision
+ */
+ int getBitPrecision() { return _bitPrecision; }
private:
float *_table;
int _bitPrecision;
+ double _radResolution; // Smallest radian increment
+ int _refSize; // _nPoints / 4
+ int _nPoints; // range of operator[]
};
} // End of namespace Common
diff --git a/common/sinetables.cpp b/common/sinetables.cpp
index c01705e3dc..c85a7bf7cf 100644
--- a/common/sinetables.cpp
+++ b/common/sinetables.cpp
@@ -32,17 +32,39 @@ SineTable::SineTable(int bitPrecision) {
_bitPrecision = bitPrecision;
- int m = 1 << _bitPrecision;
- double freq = 2 * M_PI / m;
- _table = new float[m / 2];
+ _nPoints = 1 << _bitPrecision;
+ _radResolution = 2.0 * M_PI / _nPoints;
+ _refSize = _nPoints / 4;
+ _table = new float[_nPoints / 2];
- // Table contains sin(2*pi*i/m) for 0<=i<m/4,
- // followed by m/2<=i<3m/4
- for (int i = 0; i < m / 4; i++)
- _table[i] = sin(i * freq);
+ // Table contains sin(2*pi*i/_nPoints) for 0<=i<_nPoints/4,
+ // followed by _nPoints/2<=i<3_nPoints/4
+ for (int i = 0; i < _nPoints / 4; i++)
+ _table[i] = sin(i * _radResolution);
- for (int i = 0; i < m / 4; i++)
- _table[m / 4 + i] = -_table[i];
+ for (int i = 0; i < _nPoints / 4; i++)
+ _table[_nPoints / 4 + i] = -_table[i];
+
+}
+
+float SineTable::at(int index) const {
+ assert((index >= 0) && (index < _nPoints));
+ if (index < _refSize)
+ // [0,pi/2)
+ return _table[index];
+ if (index == _refSize)
+ // pi/2
+ return 1.0f; // sin(pi/2) = 1.0
+ if ((index > _refSize) && (index < 2 * _refSize))
+ // (pi/2,pi)
+ return _table[2 * _refSize - index];
+ if ((index >= 2 * _refSize) && (index < 3 * _refSize))
+ // [pi,3/2pi)
+ return -_table[index - 2 * _refSize];
+ if ((index > 3 * _refSize) && (index < _nPoints))
+ // (3/2pi,2pi)
+ return -_table[_nPoints - index];
+ return -1.0f; // sin(3pi/2) = -1.0
}
SineTable::~SineTable() {
diff --git a/common/sinetables.h b/common/sinetables.h
index 67225c0bcb..f91592cf38 100644
--- a/common/sinetables.h
+++ b/common/sinetables.h
@@ -39,22 +39,32 @@ public:
* Get pointer to table
*
* This table contains 2^bitPrecision/2 entries.
+ * Prefer to use at()
* The layout of this table is as follows:
* - Entries 0 up to (excluding) 2^bitPrecision/4:
* sin(0) till (excluding) sin(1/2*pi)
- * - Entries 2^bitPrecision/4 up to (excluding) 2^bitPrecision/2:
+ * - Entries 2^bitPrecision/4 up to 2^bitPrecision/2:
* sin(pi) till (excluding) sin(3/2*pi)
*/
const float *getTable() { return _table; }
/**
- * Get pointer to table
+ * Returns sin(2*pi * index / 2^bitPrecision )
+ * Index must be in range [0,2^bitPrecision-1]
+ */
+ float at(int index) const;
+
+ /**
+ * Get bit precision
*/
- int getPrecision() { return _bitPrecision; }
+ int getBitPrecision() { return _bitPrecision; }
private:
float *_table;
int _bitPrecision;
+ double _radResolution; // Smallest radian increment
+ int _refSize; // _nPoints / 4
+ int _nPoints; // range of operator[]
};
} // End of namespace Common
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