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cpython/Objects/stringlib/find_max_char.h at 3.9 · python-emscripten/cpython · GitHub
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find_max_char.h
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cpython
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stringlib
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find_max_char.h
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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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