cpython/Objects/stringlib/split.h at 3.5 · python/cpython · GitHub

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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_SIZE(list) = count

Py_LOCAL_INLINE(PyObject *)

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++;

#ifndef 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 *)

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;

}

#ifndef 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 *)

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)

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) {

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;

}

#ifndef 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 *)

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--;

#ifndef 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 *)

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;

}

#ifndef 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 *)

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)

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) {

pos = FASTSEARCH(str, j, sep, sep_len, -1, FAST_RSEARCH);

if (pos < 0)

break;

SPLIT_ADD(str, pos + sep_len, j);

j = pos;

}

#ifndef 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 *)

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;

}

#ifndef 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;

}

cpython/Objects/stringlib/split.h at 3.5 · python/cpython · GitHub

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