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cpython#129894: just get the log10 #1

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Merged
merged 2 commits into from
Mar 1, 2025
Merged

cpython#129894: just get the log10 #1

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713ece5
Get log10 only, fill buffer backwards
encukou Feb 26, 2025
6edcfef
Remove obsolete comment
encukou Feb 26, 2025
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79 changes: 28 additions & 51 deletions Python/codecs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -730,54 +730,20 @@ codec_handler_write_unicode_hex(Py_UCS1 **p, Py_UCS4 ch)
}


static inline void
codec_handler_unicode_log10_max(Py_UCS4 ch, int *base, int *digits)
{
#define MAKE_BRANCH(D, N) \
do { \
if (ch < 10 * (N)) { \
if (base != NULL) { \
*base = (N); \
} \
if (digits != NULL) { \
*digits = (D); \
} \
return; \
} \
} while (0)
MAKE_BRANCH(1, 1);
MAKE_BRANCH(2, 10);
MAKE_BRANCH(3, 100);
MAKE_BRANCH(4, 1000);
MAKE_BRANCH(5, 10000);
MAKE_BRANCH(6, 100000);
MAKE_BRANCH(7, 1000000);
#undef MAKE_BRANCH
Py_UNREACHABLE();
}


/*
* Write the decimal representation of 'ch' to the buffer pointed by 'p'
* using at most 7 characters prefixed by '&#' and suffixed by ';'.
/* Determine the number of digits for a decimal representation of codepoint ch
*/
static inline void
codec_handler_write_unicode_dec(Py_UCS1 **p, Py_UCS4 ch)
{
int base = 0, digits = 0;
codec_handler_unicode_log10_max(ch, &base, &digits);
assert(base != 0 && digits != 0);
assert(digits <= 7);

*(*p)++ = '&';
*(*p)++ = '#';
while (digits-- > 0) {
assert(base >= 1);
*(*p)++ = '0' + ch / base;
ch %= base;
base /= 10;
}
*(*p)++ = ';';
static inline int
n_decimal_digits_for_codepoint(Py_UCS4 ch)
{
if (ch < 10) return 1;
if (ch < 100) return 2;
if (ch < 1000) return 3;
if (ch < 10000) return 4;
if (ch < 100000) return 5;
if (ch < 1000000) return 6;
if (ch < 10000000) return 7;
// Unicode codepoints are limited to 1114111 (7 decimal digits)
Py_UNREACHABLE();
}

/*
Expand Down Expand Up @@ -949,10 +915,8 @@ PyObject *PyCodec_XMLCharRefReplaceErrors(PyObject *exc)

Py_ssize_t ressize = 0;
for (Py_ssize_t i = start; i < end; ++i) {
/* object is guaranteed to be "ready" */
Py_UCS4 ch = PyUnicode_READ_CHAR(obj, i);
int k = 0;
codec_handler_unicode_log10_max(ch, NULL, &k);
int k = n_decimal_digits_for_codepoint(ch);
assert(k != 0);
assert(k <= 7);
ressize += 2 + k + 1;
Expand All @@ -968,7 +932,20 @@ PyObject *PyCodec_XMLCharRefReplaceErrors(PyObject *exc)
/* generate replacement */
for (Py_ssize_t i = start; i < end; ++i) {
Py_UCS4 ch = PyUnicode_READ_CHAR(obj, i);
codec_handler_write_unicode_dec(&outp, ch);
/*
* Write the decimal representation of 'ch' to the buffer pointed by 'p'
* using at most 7 characters prefixed by '&#' and suffixed by ';'.
*/
*outp++ = '&';
*outp++ = '#';
Py_UCS1 *digit_end = outp + n_decimal_digits_for_codepoint(ch);
for (Py_UCS1 *digitp = digit_end - 1; digitp >= outp; --digitp) {
*digitp = '0' + (ch % 10);
ch /= 10;
}
assert(ch == 0);
outp = digit_end;
*outp++ = ';';
}
assert(_PyUnicode_CheckConsistency(res, 1));
PyObject *restuple = Py_BuildValue("(Nn)", res, end);
Expand Down