bordermode-inl.h

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 * ---------------------------------------------------------------------------
 * \file dnn/src/common/cv/bordermode-inl.h
 *
 * MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
 *
 * Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
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static inline int border_interpolate(int p, int len, BorderMode bmode) {
    if ((unsigned)p < (unsigned)len)
        ;
    else if (bmode == BorderMode::BORDER_REPLICATE)
        p = p < 0 ? 0 : len - 1;
    else if (bmode == BorderMode::BORDER_REFLECT ||
             bmode == BorderMode::BORDER_REFLECT_101) {
        int delta = (bmode == BorderMode::BORDER_REFLECT_101);
        if (len == 1)
            return 0;
        do {
            if (p < 0)
                p = -p - 1 + delta;
            else
                p = len - 1 - (p - len) - delta;
        } while ((unsigned)p >= (unsigned)len);
    } else if (bmode == BorderMode::BORDER_WRAP) {
        megdnn_assert(len > 0);
        if (p < 0)
            p -= ((p - len + 1) / len) * len;
        while (p >= len) {
            p -= len;
        }
    } else if (bmode == BorderMode::BORDER_CONSTANT ||
               bmode == BorderMode::BORDER_TRANSPARENT)
        p = -1;
    else
        MegCVException("Unknown/unsupported border type");
    return p;
}

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