cpython/Objects/stringlib/split.h

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/* stringlib: split implementation */
#ifndef STRINGLIB_FASTSEARCH_H
#error must include "stringlib/fastsearch.h" before including this module
#endif
/* Overallocate the initial list to reduce the number of reallocs for small
split sizes. Eg, "A A A A A A A A A A".split() (10 elements) has three
resizes, to sizes 4, 8, then 16. Most observed string splits are for human
text (roughly 11 words per line) and field delimited data (usually 1-10
fields). For large strings the split algorithms are bandwidth limited
so increasing the preallocation likely will not improve things.*/
#define MAX_PREALLOC 12
/* 5 splits gives 6 elements */
#define PREALLOC_SIZE(maxsplit) \
(maxsplit >= MAX_PREALLOC ? MAX_PREALLOC : maxsplit+1)
#define SPLIT_APPEND(data, left, right) \
sub = STRINGLIB_NEW((data) + (left), \
(right) - (left)); \
if (sub == NULL) \
goto onError; \
if (PyList_Append(list, sub)) { \
Py_DECREF(sub); \
goto onError; \
} \
else \
Py_DECREF(sub);
#define SPLIT_ADD(data, left, right) { \
sub = STRINGLIB_NEW((data) + (left), \
(right) - (left)); \
if (sub == NULL) \
goto onError; \
if (count < MAX_PREALLOC) { \
PyList_SET_ITEM(list, count, sub); \
} else { \
if (PyList_Append(list, sub)) { \
Py_DECREF(sub); \
goto onError; \
} \
else \
Py_DECREF(sub); \
} \
count++; }
/* Always force the list to the expected size. */
#define FIX_PREALLOC_SIZE(list) Py_SET_SIZE(list, count)
Py_LOCAL_INLINE(PyObject *)
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STRINGLIB(split_whitespace)(PyObject* str_obj,
const STRINGLIB_CHAR* str, Py_ssize_t str_len,
Py_ssize_t maxcount)
{
Py_ssize_t i, j, count=0;
PyObject *list = PyList_New(PREALLOC_SIZE(maxcount));
PyObject *sub;
if (list == NULL)
return NULL;
i = j = 0;
while (maxcount-- > 0) {
while (i < str_len && STRINGLIB_ISSPACE(str[i]))
i++;
if (i == str_len) break;
j = i; i++;
while (i < str_len && !STRINGLIB_ISSPACE(str[i]))
i++;
#if !STRINGLIB_MUTABLE
if (j == 0 && i == str_len && STRINGLIB_CHECK_EXACT(str_obj)) {
/* No whitespace in str_obj, so just use it as list[0] */
Py_INCREF(str_obj);
PyList_SET_ITEM(list, 0, (PyObject *)str_obj);
count++;
break;
}
#endif
SPLIT_ADD(str, j, i);
}
if (i < str_len) {
/* Only occurs when maxcount was reached */
/* Skip any remaining whitespace and copy to end of string */
while (i < str_len && STRINGLIB_ISSPACE(str[i]))
i++;
if (i != str_len)
SPLIT_ADD(str, i, str_len);
}
FIX_PREALLOC_SIZE(list);
return list;
onError:
Py_DECREF(list);
return NULL;
}
Py_LOCAL_INLINE(PyObject *)
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STRINGLIB(split_char)(PyObject* str_obj,
const STRINGLIB_CHAR* str, Py_ssize_t str_len,
const STRINGLIB_CHAR ch,
Py_ssize_t maxcount)
{
Py_ssize_t i, j, count=0;
PyObject *list = PyList_New(PREALLOC_SIZE(maxcount));
PyObject *sub;
if (list == NULL)
return NULL;
i = j = 0;
while ((j < str_len) && (maxcount-- > 0)) {
for(; j < str_len; j++) {
/* I found that using memchr makes no difference */
if (str[j] == ch) {
SPLIT_ADD(str, i, j);
i = j = j + 1;
break;
}
}
}
#if !STRINGLIB_MUTABLE
if (count == 0 && STRINGLIB_CHECK_EXACT(str_obj)) {
/* ch not in str_obj, so just use str_obj as list[0] */
Py_INCREF(str_obj);
PyList_SET_ITEM(list, 0, (PyObject *)str_obj);
count++;
} else
#endif
if (i <= str_len) {
SPLIT_ADD(str, i, str_len);
}
FIX_PREALLOC_SIZE(list);
return list;
onError:
Py_DECREF(list);
return NULL;
}
Py_LOCAL_INLINE(PyObject *)
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STRINGLIB(split)(PyObject* str_obj,
const STRINGLIB_CHAR* str, Py_ssize_t str_len,
const STRINGLIB_CHAR* sep, Py_ssize_t sep_len,
Py_ssize_t maxcount)
{
Py_ssize_t i, j, pos, count=0;
PyObject *list, *sub;
if (sep_len == 0) {
PyErr_SetString(PyExc_ValueError, "empty separator");
return NULL;
}
else if (sep_len == 1)
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return STRINGLIB(split_char)(str_obj, str, str_len, sep[0], maxcount);
list = PyList_New(PREALLOC_SIZE(maxcount));
if (list == NULL)
return NULL;
i = j = 0;
while (maxcount-- > 0) {
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pos = FASTSEARCH(str+i, str_len-i, sep, sep_len, -1, FAST_SEARCH);
if (pos < 0)
break;
j = i + pos;
SPLIT_ADD(str, i, j);
i = j + sep_len;
}
#if !STRINGLIB_MUTABLE
if (count == 0 && STRINGLIB_CHECK_EXACT(str_obj)) {
/* No match in str_obj, so just use it as list[0] */
Py_INCREF(str_obj);
PyList_SET_ITEM(list, 0, (PyObject *)str_obj);
count++;
} else
#endif
{
SPLIT_ADD(str, i, str_len);
}
FIX_PREALLOC_SIZE(list);
return list;
onError:
Py_DECREF(list);
return NULL;
}
Py_LOCAL_INLINE(PyObject *)
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STRINGLIB(rsplit_whitespace)(PyObject* str_obj,
const STRINGLIB_CHAR* str, Py_ssize_t str_len,
Py_ssize_t maxcount)
{
Py_ssize_t i, j, count=0;
PyObject *list = PyList_New(PREALLOC_SIZE(maxcount));
PyObject *sub;
if (list == NULL)
return NULL;
i = j = str_len - 1;
while (maxcount-- > 0) {
while (i >= 0 && STRINGLIB_ISSPACE(str[i]))
i--;
if (i < 0) break;
j = i; i--;
while (i >= 0 && !STRINGLIB_ISSPACE(str[i]))
i--;
#if !STRINGLIB_MUTABLE
if (j == str_len - 1 && i < 0 && STRINGLIB_CHECK_EXACT(str_obj)) {
/* No whitespace in str_obj, so just use it as list[0] */
Py_INCREF(str_obj);
PyList_SET_ITEM(list, 0, (PyObject *)str_obj);
count++;
break;
}
#endif
SPLIT_ADD(str, i + 1, j + 1);
}
if (i >= 0) {
/* Only occurs when maxcount was reached */
/* Skip any remaining whitespace and copy to beginning of string */
while (i >= 0 && STRINGLIB_ISSPACE(str[i]))
i--;
if (i >= 0)
SPLIT_ADD(str, 0, i + 1);
}
FIX_PREALLOC_SIZE(list);
if (PyList_Reverse(list) < 0)
goto onError;
return list;
onError:
Py_DECREF(list);
return NULL;
}
Py_LOCAL_INLINE(PyObject *)
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STRINGLIB(rsplit_char)(PyObject* str_obj,
const STRINGLIB_CHAR* str, Py_ssize_t str_len,
const STRINGLIB_CHAR ch,
Py_ssize_t maxcount)
{
Py_ssize_t i, j, count=0;
PyObject *list = PyList_New(PREALLOC_SIZE(maxcount));
PyObject *sub;
if (list == NULL)
return NULL;
i = j = str_len - 1;
while ((i >= 0) && (maxcount-- > 0)) {
for(; i >= 0; i--) {
if (str[i] == ch) {
SPLIT_ADD(str, i + 1, j + 1);
j = i = i - 1;
break;
}
}
}
#if !STRINGLIB_MUTABLE
if (count == 0 && STRINGLIB_CHECK_EXACT(str_obj)) {
/* ch not in str_obj, so just use str_obj as list[0] */
Py_INCREF(str_obj);
PyList_SET_ITEM(list, 0, (PyObject *)str_obj);
count++;
} else
#endif
if (j >= -1) {
SPLIT_ADD(str, 0, j + 1);
}
FIX_PREALLOC_SIZE(list);
if (PyList_Reverse(list) < 0)
goto onError;
return list;
onError:
Py_DECREF(list);
return NULL;
}
Py_LOCAL_INLINE(PyObject *)
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STRINGLIB(rsplit)(PyObject* str_obj,
const STRINGLIB_CHAR* str, Py_ssize_t str_len,
const STRINGLIB_CHAR* sep, Py_ssize_t sep_len,
Py_ssize_t maxcount)
{
Py_ssize_t j, pos, count=0;
PyObject *list, *sub;
if (sep_len == 0) {
PyErr_SetString(PyExc_ValueError, "empty separator");
return NULL;
}
else if (sep_len == 1)
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return STRINGLIB(rsplit_char)(str_obj, str, str_len, sep[0], maxcount);
list = PyList_New(PREALLOC_SIZE(maxcount));
if (list == NULL)
return NULL;
j = str_len;
while (maxcount-- > 0) {
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pos = FASTSEARCH(str, j, sep, sep_len, -1, FAST_RSEARCH);
if (pos < 0)
break;
SPLIT_ADD(str, pos + sep_len, j);
j = pos;
}
#if !STRINGLIB_MUTABLE
if (count == 0 && STRINGLIB_CHECK_EXACT(str_obj)) {
/* No match in str_obj, so just use it as list[0] */
Py_INCREF(str_obj);
PyList_SET_ITEM(list, 0, (PyObject *)str_obj);
count++;
} else
#endif
{
SPLIT_ADD(str, 0, j);
}
FIX_PREALLOC_SIZE(list);
if (PyList_Reverse(list) < 0)
goto onError;
return list;
onError:
Py_DECREF(list);
return NULL;
}
Py_LOCAL_INLINE(PyObject *)
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STRINGLIB(splitlines)(PyObject* str_obj,
const STRINGLIB_CHAR* str, Py_ssize_t str_len,
int keepends)
{
/* This does not use the preallocated list because splitlines is
usually run with hundreds of newlines. The overhead of
switching between PyList_SET_ITEM and append causes about a
2-3% slowdown for that common case. A smarter implementation
could move the if check out, so the SET_ITEMs are done first
and the appends only done when the prealloc buffer is full.
That's too much work for little gain.*/
Py_ssize_t i;
Py_ssize_t j;
PyObject *list = PyList_New(0);
PyObject *sub;
if (list == NULL)
return NULL;
for (i = j = 0; i < str_len; ) {
Py_ssize_t eol;
/* Find a line and append it */
while (i < str_len && !STRINGLIB_ISLINEBREAK(str[i]))
i++;
/* Skip the line break reading CRLF as one line break */
eol = i;
if (i < str_len) {
if (str[i] == '\r' && i + 1 < str_len && str[i+1] == '\n')
i += 2;
else
i++;
if (keepends)
eol = i;
}
#if !STRINGLIB_MUTABLE
if (j == 0 && eol == str_len && STRINGLIB_CHECK_EXACT(str_obj)) {
/* No linebreak in str_obj, so just use it as list[0] */
if (PyList_Append(list, str_obj))
goto onError;
break;
}
#endif
SPLIT_APPEND(str, j, eol);
j = i;
}
return list;
onError:
Py_DECREF(list);
return NULL;
}