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/* Finding the optimal width of unicode characters in a buffer */
#if !STRINGLIB_IS_UNICODE
# error "find_max_char.h is specific to Unicode"
#endif
/* Mask to quickly check whether a C 'long' contains a
non-ASCII, UTF8-encoded char. */
#if (SIZEOF_LONG == 8)
# define UCS1_ASCII_CHAR_MASK 0x8080808080808080UL
#elif (SIZEOF_LONG == 4)
# define UCS1_ASCII_CHAR_MASK 0x80808080UL
#else
# error C 'long' size should be either 4 or 8!
#endif
#if STRINGLIB_SIZEOF_CHAR == 1
Py_LOCAL_INLINE(Py_UCS4)
STRINGLIB(find_max_char)(const STRINGLIB_CHAR *begin, const STRINGLIB_CHAR *end)
{
const unsigned char *p = (const unsigned char *) begin;
const unsigned char *aligned_end =
(const unsigned char *) _Py_ALIGN_DOWN(end, SIZEOF_LONG);
while (p < end) {
if (_Py_IS_ALIGNED(p, SIZEOF_LONG)) {
/* Help register allocation */
const unsigned char *_p = p;
while (_p < aligned_end) {
unsigned long value = *(const unsigned long *) _p;
if (value & UCS1_ASCII_CHAR_MASK)
return 255;
_p += SIZEOF_LONG;
}
p = _p;
if (p == end)
break;
}
if (*p++ & 0x80)
return 255;
}
return 127;
}
#undef ASCII_CHAR_MASK
#else /* STRINGLIB_SIZEOF_CHAR == 1 */
#define MASK_ASCII 0xFFFFFF80
#define MASK_UCS1 0xFFFFFF00
#define MASK_UCS2 0xFFFF0000
#define MAX_CHAR_ASCII 0x7f
#define MAX_CHAR_UCS1 0xff
#define MAX_CHAR_UCS2 0xffff
#define MAX_CHAR_UCS4 0x10ffff
Py_LOCAL_INLINE(Py_UCS4)
STRINGLIB(find_max_char)(const STRINGLIB_CHAR *begin, const STRINGLIB_CHAR *end)
{
#if STRINGLIB_SIZEOF_CHAR == 2
const Py_UCS4 mask_limit = MASK_UCS1;
const Py_UCS4 max_char_limit = MAX_CHAR_UCS2;
#elif STRINGLIB_SIZEOF_CHAR == 4
const Py_UCS4 mask_limit = MASK_UCS2;
const Py_UCS4 max_char_limit = MAX_CHAR_UCS4;
#else
#error Invalid STRINGLIB_SIZEOF_CHAR (must be 1, 2 or 4)
#endif
Py_UCS4 mask;
Py_ssize_t n = end - begin;
const STRINGLIB_CHAR *p = begin;
const STRINGLIB_CHAR *unrolled_end = begin + _Py_SIZE_ROUND_DOWN(n, 4);
Py_UCS4 max_char;
max_char = MAX_CHAR_ASCII;
mask = MASK_ASCII;
while (p < unrolled_end) {
STRINGLIB_CHAR bits = p[0] | p[1] | p[2] | p[3];
if (bits & mask) {
if (mask == mask_limit) {
/* Limit reached */
return max_char_limit;
}
if (mask == MASK_ASCII) {
max_char = MAX_CHAR_UCS1;
mask = MASK_UCS1;
}
else {
/* mask can't be MASK_UCS2 because of mask_limit above */
assert(mask == MASK_UCS1);
max_char = MAX_CHAR_UCS2;
mask = MASK_UCS2;
}
/* We check the new mask on the same chars in the next iteration */
continue;
}
p += 4;
}
while (p < end) {
if (p[0] & mask) {
if (mask == mask_limit) {
/* Limit reached */
return max_char_limit;
}
if (mask == MASK_ASCII) {
max_char = MAX_CHAR_UCS1;
mask = MASK_UCS1;
}
else {
/* mask can't be MASK_UCS2 because of mask_limit above */
assert(mask == MASK_UCS1);
max_char = MAX_CHAR_UCS2;
mask = MASK_UCS2;
}
/* We check the new mask on the same chars in the next iteration */
continue;
}
p++;
}
return max_char;
}
#undef MASK_ASCII
#undef MASK_UCS1
#undef MASK_UCS2
#undef MAX_CHAR_ASCII
#undef MAX_CHAR_UCS1
#undef MAX_CHAR_UCS2
#undef MAX_CHAR_UCS4
#endif /* STRINGLIB_SIZEOF_CHAR == 1 */
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