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Add _PyUnicodeWriter_WriteSubstring() function

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Write a function to enable more optimizations:

 * If the substring is the whole string and overallocation is disabled, just
   keep a reference to the string, don't copy characters
 * Avoid a call to the expensive _PyUnicode_FindMaxChar() function when
   possible
This commit is contained in:
Victor Stinner 2013-04-03 01:48:39 +02:00
parent 4489e927a6
commit cfc4c13b04
4 changed files with 57 additions and 21 deletions
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48
Objects/unicodeobject.c
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@ -12790,6 +12790,41 @@ _PyUnicodeWriter_WriteStr(_PyUnicodeWriter *writer, PyObject *str)
return 0;
}
int
_PyUnicodeWriter_WriteSubstring(_PyUnicodeWriter *writer, PyObject *str,
Py_ssize_t start, Py_ssize_t end)
{
Py_UCS4 maxchar;
Py_ssize_t len;
if (PyUnicode_READY(str) == -1)
return -1;
assert(0 <= start);
assert(end <= PyUnicode_GET_LENGTH(str));
assert(start <= end);
if (end == 0)
return 0;
if (start == 0 && end == PyUnicode_GET_LENGTH(str))
return _PyUnicodeWriter_WriteStr(writer, str);
if (PyUnicode_MAX_CHAR_VALUE(str) > writer->maxchar)
maxchar = _PyUnicode_FindMaxChar(str, start, end);
else
maxchar = writer->maxchar;
len = end - start;
if (_PyUnicodeWriter_Prepare(writer, len, maxchar) < 0)
return -1;
_PyUnicode_FastCopyCharacters(writer->buffer, writer->pos,
str, start, len);
writer->pos += len;
return 0;
}
int
_PyUnicodeWriter_WriteCstr(_PyUnicodeWriter *writer, const char *str, Py_ssize_t len)
{
@ -13963,7 +13998,7 @@ PyUnicode_Format(PyObject *format, PyObject *args)
while (--ctx.fmtcnt >= 0) {
if (PyUnicode_READ(ctx.fmtkind, ctx.fmtdata, ctx.fmtpos) != '%') {
Py_ssize_t nonfmtpos, sublen;
Py_ssize_t nonfmtpos;
Py_UCS4 maxchar;
nonfmtpos = ctx.fmtpos++;
@ -13976,15 +14011,10 @@ PyUnicode_Format(PyObject *format, PyObject *args)
ctx.fmtpos--;
ctx.writer.overallocate = 0;
}
sublen = ctx.fmtpos - nonfmtpos;
maxchar = _PyUnicode_FindMaxChar(ctx.fmtstr,
nonfmtpos, nonfmtpos + sublen);
if (_PyUnicodeWriter_Prepare(&ctx.writer, sublen, maxchar) == -1)
goto onError;
_PyUnicode_FastCopyCharacters(ctx.writer.buffer, ctx.writer.pos,
ctx.fmtstr, nonfmtpos, sublen);
ctx.writer.pos += sublen;
if (_PyUnicodeWriter_WriteSubstring(&ctx.writer, ctx.fmtstr,
nonfmtpos, ctx.fmtpos) < 0)
goto onError;
}
else {
ctx.fmtpos++;