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/* stringlib: bytes joining implementation */
#if STRINGLIB_IS_UNICODE
#error join.h only compatible with byte-wise strings
#endif
Py_LOCAL_INLINE(PyObject *)
STRINGLIB(bytes_join_lock_held)(PyObject *sep, PyObject *seq)
{
const char *sepstr = STRINGLIB_STR(sep);
Py_ssize_t seplen = STRINGLIB_LEN(sep);
PyObject *res = NULL;
char *p;
Py_ssize_t seqlen = 0;
Py_ssize_t sz = 0;
Py_ssize_t i, nbufs;
PyObject *item;
Py_buffer *buffers = NULL;
#define NB_STATIC_BUFFERS 10
Py_buffer static_buffers[NB_STATIC_BUFFERS];
#define GIL_THRESHOLD 1048576
int drop_gil = 1;
PyThreadState *save = NULL;
seqlen = PySequence_Fast_GET_SIZE(seq);
if (seqlen == 0) {
return STRINGLIB_NEW(NULL, 0);
}
#if !STRINGLIB_MUTABLE
if (seqlen == 1) {
item = PySequence_Fast_GET_ITEM(seq, 0);
if (STRINGLIB_CHECK_EXACT(item)) {
return Py_NewRef(item);
}
}
#endif
if (seqlen > NB_STATIC_BUFFERS) {
buffers = PyMem_NEW(Py_buffer, seqlen);
if (buffers == NULL) {
PyErr_NoMemory();
return NULL;
}
}
else {
buffers = static_buffers;
}
/* Here is the general case. Do a pre-pass to figure out the total
* amount of space we'll need (sz), and see whether all arguments are
* bytes-like.
*/
for (i = 0, nbufs = 0; i < seqlen; i++) {
Py_ssize_t itemlen;
item = PySequence_Fast_GET_ITEM(seq, i);
if (PyBytes_CheckExact(item)) {
/* Fast path. */
buffers[i].obj = Py_NewRef(item);
buffers[i].buf = PyBytes_AS_STRING(item);
buffers[i].len = PyBytes_GET_SIZE(item);
}
else {
/* item is only borrowed; its __buffer__() may run Python that
drops the sequence's last reference to it. */
Py_INCREF(item);
if (PyObject_GetBuffer(item, &buffers[i], PyBUF_SIMPLE) != 0) {
PyErr_Format(PyExc_TypeError,
"sequence item %zd: expected a bytes-like object, "
"%.80s found",
i, Py_TYPE(item)->tp_name);
Py_DECREF(item);
goto error;
}
Py_DECREF(item);
/* If the backing objects are mutable, then dropping the GIL
* opens up race conditions where another thread tries to modify
* the object which we hold a buffer on it. Such code has data
* races anyway, but this is a conservative approach that avoids
* changing the behaviour of that data race.
*/
drop_gil = 0;
}
nbufs = i + 1; /* for error cleanup */
itemlen = buffers[i].len;
if (itemlen > PY_SSIZE_T_MAX - sz) {
PyErr_SetString(PyExc_OverflowError,
"join() result is too long");
goto error;
}
sz += itemlen;
if (i != 0) {
if (seplen > PY_SSIZE_T_MAX - sz) {
PyErr_SetString(PyExc_OverflowError,
"join() result is too long");
goto error;
}
sz += seplen;
}
if (seqlen != PySequence_Fast_GET_SIZE(seq)) {
PyErr_SetString(PyExc_RuntimeError,
"sequence changed size during iteration");
goto error;
}
}
/* Allocate result space. */
res = STRINGLIB_NEW(NULL, sz);
if (res == NULL)
goto error;
/* Catenate everything. */
p = STRINGLIB_STR(res);
if (sz < GIL_THRESHOLD) {
drop_gil = 0; /* Benefits are likely outweighed by the overheads */
}
if (drop_gil) {
save = PyEval_SaveThread();
}
if (!seplen) {
/* fast path */
for (i = 0; i < nbufs; i++) {
Py_ssize_t n = buffers[i].len;
char *q = buffers[i].buf;
memcpy(p, q, n);
p += n;
}
}
else {
Py_ssize_t n = buffers[0].len;
char *q = buffers[0].buf;
memcpy(p, q, n);
p += n;
for (i = 1; i < nbufs; i++) {
memcpy(p, sepstr, seplen);
p += seplen;
n = buffers[i].len;
q = buffers[i].buf;
memcpy(p, q, n);
p += n;
}
}
if (drop_gil) {
PyEval_RestoreThread(save);
}
goto done;
error:
res = NULL;
done:
for (i = 0; i < nbufs; i++)
PyBuffer_Release(&buffers[i]);
if (buffers != static_buffers)
PyMem_Free(buffers);
return res;
}
Py_LOCAL_INLINE(PyObject *)
STRINGLIB(bytes_join)(PyObject *sep, PyObject *iterable)
{
PyObject *seq, *res;
seq = PySequence_Fast(iterable, "can only join an iterable");
if (seq == NULL) {
return NULL;
}
Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST(iterable);
res = STRINGLIB(bytes_join_lock_held)(sep, seq);
Py_END_CRITICAL_SECTION_SEQUENCE_FAST();
Py_DECREF(seq);
return res;
}
#undef NB_STATIC_BUFFERS
#undef GIL_THRESHOLD
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