michael@0: 
michael@0: /*
michael@0:  * Copyright 2010 The Android Open Source Project
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: 
michael@0: #include "SkMath.h"
michael@0: #include "SkScalar.h"
michael@0: 
michael@0: SkScalar SkScalarInterpFunc(SkScalar searchKey, const SkScalar keys[],
michael@0:                             const SkScalar values[], int length) {
michael@0:     SkASSERT(length > 0);
michael@0:     SkASSERT(keys != NULL);
michael@0:     SkASSERT(values != NULL);
michael@0: #ifdef SK_DEBUG
michael@0:     for (int i = 1; i < length; i++)
michael@0:         SkASSERT(keys[i] >= keys[i-1]);
michael@0: #endif
michael@0:     int right = 0;
michael@0:     while (right < length && searchKey > keys[right])
michael@0:         right++;
michael@0:     // Could use sentinel values to eliminate conditionals, but since the
michael@0:     // tables are taken as input, a simpler format is better.
michael@0:     if (length == right)
michael@0:         return values[length-1];
michael@0:     if (0 == right)
michael@0:         return values[0];
michael@0:     // Otherwise, interpolate between right - 1 and right.
michael@0:     SkScalar rightKey = keys[right];
michael@0:     SkScalar leftKey = keys[right-1];
michael@0:     SkScalar fract = SkScalarDiv(searchKey-leftKey,rightKey-leftKey);
michael@0:     return SkScalarInterp(values[right-1], values[right], fract);
michael@0: }