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 /* * Copyright (C) 2011 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifndef _LIBS_UTILS_LINEAR_TRANSFORM_H #define _LIBS_UTILS_LINEAR_TRANSFORM_H #include namespace android { // LinearTransform defines a structure which hold the definition of a // transformation from single dimensional coordinate system A into coordinate // system B (and back again). Values in A and in B are 64 bit, the linear // scale factor is expressed as a rational number using two 32 bit values. // // Specifically, let // f(a) = b // F(b) = f^-1(b) = a // then // // f(a) = (((a - a_zero) * a_to_b_numer) / a_to_b_denom) + b_zero; // // and // // F(b) = (((b - b_zero) * a_to_b_denom) / a_to_b_numer) + a_zero; // struct LinearTransform { int64_t a_zero; int64_t b_zero; int32_t a_to_b_numer; uint32_t a_to_b_denom; // Transform from A->B // Returns true on success, or false in the case of a singularity or an // overflow. bool doForwardTransform(int64_t a_in, int64_t* b_out) const; // Transform from B->A // Returns true on success, or false in the case of a singularity or an // overflow. bool doReverseTransform(int64_t b_in, int64_t* a_out) const; // Helpers which will reduce the fraction N/D using Euclid's method. template static void reduce(T* N, T* D); static void reduce(int32_t* N, uint32_t* D); }; } #endif // _LIBS_UTILS_LINEAR_TRANSFORM_H