#include <stdlib.h>
#define _PyUnicode_CONVERT_BYTES(from_type, to_type, begin, end, to) \
    do {                                                \
        const from_type *iter_; to_type *to_;           \
        for (iter_ = (begin), to_ = (to_type *)(to);    \
             iter_ < (end);                             \
             ++iter_, ++to_) {                          \
            *to_ = (to_type)*iter_;                     \
        }                                               \
    } while (0)

void func1(unsigned char *a, unsigned char *b, unsigned short *c)
{
_PyUnicode_CONVERT_BYTES(unsigned char, unsigned short, a, b, c);
}

#undef _PyUnicode_CONVERT_BYTES
#define _PyUnicode_CONVERT_BYTES(from_type, to_type, begin, end, to) \
    do {                                                \
        to_type *_to = (to_type *) to;                  \
        const from_type *_iter = (begin);               \
        const from_type *_end = (end);                  \
        size_t n = (_end) - (_iter);                \
        const from_type *_unrolled_end =                \
            _iter + (n & ~ (size_t) 3);             \
        while (_iter < (_unrolled_end)) {               \
            _to[0] = (to_type) _iter[0];                \
            _to[1] = (to_type) _iter[1];                \
            _to[2] = (to_type) _iter[2];                \
            _to[3] = (to_type) _iter[3];                \
            _iter += 4; _to += 4;                       \
        }                                               \
        while (_iter < (_end))                          \
            *_to++ = (to_type) *_iter++;                \
    } while (0)

void func2(void *a, void *b, void *c)
{
_PyUnicode_CONVERT_BYTES(unsigned char, unsigned short, a, b, c);
}