1 /*
2  * Copyright 2010 The Android Open Source Project
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 
8 
9 #include "SkMath.h"
10 #include "SkScalar.h"
11 
12 SkScalar SkScalarInterpFunc(SkScalar searchKey, const SkScalar keys[],
13                             const SkScalar values[], int length) {
14     SkASSERT(length > 0);
15     SkASSERT(keys != nullptr);
16     SkASSERT(values != nullptr);
17 #ifdef SK_DEBUG
18     for (int i = 1; i < length; i++)
19         SkASSERT(keys[i] >= keys[i-1]);
20 #endif
21     int right = 0;
22     while (right < length && searchKey > keys[right])
23         right++;
24     // Could use sentinel values to eliminate conditionals, but since the
25     // tables are taken as input, a simpler format is better.
26     if (length == right)
27         return values[length-1];
28     if (0 == right)
29         return values[0];
30     // Otherwise, interpolate between right - 1 and right.
31     SkScalar rightKey = keys[right];
32     SkScalar leftKey = keys[right-1];
33     SkScalar fract = (searchKey - leftKey) / (rightKey - leftKey);
34     return SkScalarInterp(values[right-1], values[right], fract);
35 }
36