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2508 lines (2270 loc) · 57 KB
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Copy pathlistobject.c
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2508 lines (2270 loc) · 57 KB
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/* List object implementation */
#include "Python.h"
#ifdef STDC_HEADERS
#include <stddef.h>
#else
#include <sys/types.h> /* For size_t */
#endif
static int
roundupsize(int n)
{
unsigned int nbits = 0;
unsigned int n2 = (unsigned int)n >> 5;
/* Round up:
* If n < 256, to a multiple of 8.
* If n < 2048, to a multiple of 64.
* If n < 16384, to a multiple of 512.
* If n < 131072, to a multiple of 4096.
* If n < 1048576, to a multiple of 32768.
* If n < 8388608, to a multiple of 262144.
* If n < 67108864, to a multiple of 2097152.
* If n < 536870912, to a multiple of 16777216.
* ...
* If n < 2**(5+3*i), to a multiple of 2**(3*i).
*
* This over-allocates proportional to the list size, making room
* for additional growth. The over-allocation is mild, but is
* enough to give linear-time amortized behavior over a long
* sequence of appends() in the presence of a poorly-performing
* system realloc() (which is a reality, e.g., across all flavors
* of Windows, with Win9x behavior being particularly bad -- and
* we've still got address space fragmentation problems on Win9x
* even with this scheme, although it requires much longer lists to
* provoke them than it used to).
*/
do {
n2 >>= 3;
nbits += 3;
} while (n2);
return ((n >> nbits) + 1) << nbits;
}
#define NRESIZE(var, type, nitems) \
do { \
size_t _new_size = roundupsize(nitems); \
if (_new_size <= ((~(size_t)0) / sizeof(type))) \
PyMem_RESIZE(var, type, _new_size); \
else \
var = NULL; \
} while (0)
PyObject *
PyList_New(int size)
{
PyListObject *op;
size_t nbytes;
if (size < 0) {
PyErr_BadInternalCall();
return NULL;
}
nbytes = size * sizeof(PyObject *);
/* Check for overflow without an actual overflow,
* which can cause compiler to optimise out */
if (size > PY_SIZE_MAX / sizeof(PyObject *)) {
return PyErr_NoMemory();
}
op = PyObject_GC_New(PyListObject, &PyList_Type);
if (op == NULL) {
return NULL;
}
if (size <= 0) {
op->ob_item = NULL;
}
else {
op->ob_item = (PyObject **) PyMem_MALLOC(nbytes);
if (op->ob_item == NULL) {
return PyErr_NoMemory();
}
memset(op->ob_item, 0, sizeof(*op->ob_item) * size);
}
op->ob_size = size;
_PyObject_GC_TRACK(op);
return (PyObject *) op;
}
int
PyList_Size(PyObject *op)
{
if (!PyList_Check(op)) {
PyErr_BadInternalCall();
return -1;
}
else
return ((PyListObject *)op) -> ob_size;
}
static PyObject *indexerr;
PyObject *
PyList_GetItem(PyObject *op, int i)
{
if (!PyList_Check(op)) {
PyErr_BadInternalCall();
return NULL;
}
if (i < 0 || i >= ((PyListObject *)op) -> ob_size) {
if (indexerr == NULL)
indexerr = PyString_FromString(
"list index out of range");
PyErr_SetObject(PyExc_IndexError, indexerr);
return NULL;
}
return ((PyListObject *)op) -> ob_item[i];
}
int
PyList_SetItem(register PyObject *op, register int i,
register PyObject *newitem)
{
register PyObject *olditem;
register PyObject **p;
if (!PyList_Check(op)) {
Py_XDECREF(newitem);
PyErr_BadInternalCall();
return -1;
}
if (i < 0 || i >= ((PyListObject *)op) -> ob_size) {
Py_XDECREF(newitem);
PyErr_SetString(PyExc_IndexError,
"list assignment index out of range");
return -1;
}
p = ((PyListObject *)op) -> ob_item + i;
olditem = *p;
*p = newitem;
Py_XDECREF(olditem);
return 0;
}
static int
ins1(PyListObject *self, int where, PyObject *v)
{
int i;
PyObject **items;
if (v == NULL) {
PyErr_BadInternalCall();
return -1;
}
if (self->ob_size == INT_MAX) {
PyErr_SetString(PyExc_OverflowError,
"cannot add more objects to list");
return -1;
}
items = self->ob_item;
NRESIZE(items, PyObject *, self->ob_size+1);
if (items == NULL) {
PyErr_NoMemory();
return -1;
}
if (where < 0) {
where += self->ob_size;
if (where < 0)
where = 0;
}
if (where > self->ob_size)
where = self->ob_size;
for (i = self->ob_size; --i >= where; )
items[i+1] = items[i];
Py_INCREF(v);
items[where] = v;
self->ob_item = items;
self->ob_size++;
return 0;
}
int
PyList_Insert(PyObject *op, int where, PyObject *newitem)
{
if (!PyList_Check(op)) {
PyErr_BadInternalCall();
return -1;
}
return ins1((PyListObject *)op, where, newitem);
}
int
PyList_Append(PyObject *op, PyObject *newitem)
{
if (!PyList_Check(op)) {
PyErr_BadInternalCall();
return -1;
}
return ins1((PyListObject *)op,
(int) ((PyListObject *)op)->ob_size, newitem);
}
/* Methods */
static void
list_dealloc(PyListObject *op)
{
int i;
PyObject_GC_UnTrack(op);
Py_TRASHCAN_SAFE_BEGIN(op)
if (op->ob_item != NULL) {
/* Do it backwards, for Christian Tismer.
There's a simple test case where somehow this reduces
thrashing when a *very* large list is created and
immediately deleted. */
i = op->ob_size;
while (--i >= 0) {
Py_XDECREF(op->ob_item[i]);
}
PyMem_FREE(op->ob_item);
}
op->ob_type->tp_free((PyObject *)op);
Py_TRASHCAN_SAFE_END(op)
}
static int
list_print(PyListObject *op, FILE *fp, int flags)
{
int i;
i = Py_ReprEnter((PyObject*)op);
if (i != 0) {
if (i < 0)
return i;
fprintf(fp, "[...]");
return 0;
}
fprintf(fp, "[");
for (i = 0; i < op->ob_size; i++) {
if (i > 0)
fprintf(fp, ", ");
if (PyObject_Print(op->ob_item[i], fp, 0) != 0) {
Py_ReprLeave((PyObject *)op);
return -1;
}
}
fprintf(fp, "]");
Py_ReprLeave((PyObject *)op);
return 0;
}
static PyObject *
list_repr(PyListObject *v)
{
int i;
PyObject *s, *temp;
PyObject *pieces = NULL, *result = NULL;
i = Py_ReprEnter((PyObject*)v);
if (i != 0) {
return i > 0 ? PyString_FromString("[...]") : NULL;
}
if (v->ob_size == 0) {
result = PyString_FromString("[]");
goto Done;
}
pieces = PyList_New(0);
if (pieces == NULL)
goto Done;
/* Do repr() on each element. Note that this may mutate the list,
so must refetch the list size on each iteration. */
for (i = 0; i < v->ob_size; ++i) {
int status;
s = PyObject_Repr(v->ob_item[i]);
if (s == NULL)
goto Done;
status = PyList_Append(pieces, s);
Py_DECREF(s); /* append created a new ref */
if (status < 0)
goto Done;
}
/* Add "[]" decorations to the first and last items. */
assert(PyList_GET_SIZE(pieces) > 0);
s = PyString_FromString("[");
if (s == NULL)
goto Done;
temp = PyList_GET_ITEM(pieces, 0);
PyString_ConcatAndDel(&s, temp);
PyList_SET_ITEM(pieces, 0, s);
if (s == NULL)
goto Done;
s = PyString_FromString("]");
if (s == NULL)
goto Done;
temp = PyList_GET_ITEM(pieces, PyList_GET_SIZE(pieces) - 1);
PyString_ConcatAndDel(&temp, s);
PyList_SET_ITEM(pieces, PyList_GET_SIZE(pieces) - 1, temp);
if (temp == NULL)
goto Done;
/* Paste them all together with ", " between. */
s = PyString_FromString(", ");
if (s == NULL)
goto Done;
result = _PyString_Join(s, pieces);
Py_DECREF(s);
Done:
Py_XDECREF(pieces);
Py_ReprLeave((PyObject *)v);
return result;
}
static int
list_length(PyListObject *a)
{
return a->ob_size;
}
static int
list_contains(PyListObject *a, PyObject *el)
{
int i, cmp;
for (i = 0, cmp = 0 ; cmp == 0 && i < a->ob_size; ++i)
cmp = PyObject_RichCompareBool(el, PyList_GET_ITEM(a, i),
Py_EQ);
return cmp;
}
static PyObject *
list_item(PyListObject *a, int i)
{
if (i < 0 || i >= a->ob_size) {
if (indexerr == NULL)
indexerr = PyString_FromString(
"list index out of range");
PyErr_SetObject(PyExc_IndexError, indexerr);
return NULL;
}
Py_INCREF(a->ob_item[i]);
return a->ob_item[i];
}
static PyObject *
list_slice(PyListObject *a, int ilow, int ihigh)
{
PyListObject *np;
int i;
if (ilow < 0)
ilow = 0;
else if (ilow > a->ob_size)
ilow = a->ob_size;
if (ihigh < ilow)
ihigh = ilow;
else if (ihigh > a->ob_size)
ihigh = a->ob_size;
np = (PyListObject *) PyList_New(ihigh - ilow);
if (np == NULL)
return NULL;
for (i = ilow; i < ihigh; i++) {
PyObject *v = a->ob_item[i];
Py_INCREF(v);
np->ob_item[i - ilow] = v;
}
return (PyObject *)np;
}
PyObject *
PyList_GetSlice(PyObject *a, int ilow, int ihigh)
{
if (!PyList_Check(a)) {
PyErr_BadInternalCall();
return NULL;
}
return list_slice((PyListObject *)a, ilow, ihigh);
}
static PyObject *
list_concat(PyListObject *a, PyObject *bb)
{
int size;
int i;
PyListObject *np;
if (!PyList_Check(bb)) {
PyErr_Format(PyExc_TypeError,
"can only concatenate list (not \"%.200s\") to list",
bb->ob_type->tp_name);
return NULL;
}
#define b ((PyListObject *)bb)
size = a->ob_size + b->ob_size;
if (size < 0)
return PyErr_NoMemory();
np = (PyListObject *) PyList_New(size);
if (np == NULL) {
return NULL;
}
for (i = 0; i < a->ob_size; i++) {
PyObject *v = a->ob_item[i];
Py_INCREF(v);
np->ob_item[i] = v;
}
for (i = 0; i < b->ob_size; i++) {
PyObject *v = b->ob_item[i];
Py_INCREF(v);
np->ob_item[i + a->ob_size] = v;
}
return (PyObject *)np;
#undef b
}
static PyObject *
list_repeat(PyListObject *a, int n)
{
int i, j;
int size;
PyListObject *np;
PyObject **p;
PyObject *elem;
if (n < 0)
n = 0;
size = a->ob_size * n;
if (size == 0)
return PyList_New(0);
if (n && size/n != a->ob_size)
return PyErr_NoMemory();
np = (PyListObject *) PyList_New(size);
if (np == NULL)
return NULL;
if (a->ob_size == 1) {
elem = a->ob_item[0];
for (i = 0; i < n; i++) {
np->ob_item[i] = elem;
Py_INCREF(elem);
}
return (PyObject *) np;
}
p = np->ob_item;
for (i = 0; i < n; i++) {
for (j = 0; j < a->ob_size; j++) {
*p = a->ob_item[j];
Py_INCREF(*p);
p++;
}
}
return (PyObject *) np;
}
static int
list_ass_slice(PyListObject *a, int ilow, int ihigh, PyObject *v)
{
/* Because [X]DECREF can recursively invoke list operations on
this list, we must postpone all [X]DECREF activity until
after the list is back in its canonical shape. Therefore
we must allocate an additional array, 'recycle', into which
we temporarily copy the items that are deleted from the
list. :-( */
PyObject **recycle, **p;
PyObject **item;
PyObject *v_as_SF = NULL; /* PySequence_Fast(v) */
int n; /* Size of replacement list */
int d; /* Change in size */
int k; /* Loop index */
#define b ((PyListObject *)v)
if (v == NULL)
n = 0;
else {
char msg[256];
if (a == b) {
/* Special case "a[i:j] = a" -- copy b first */
int ret;
v = list_slice(b, 0, b->ob_size);
if (v == NULL)
return -1;
ret = list_ass_slice(a, ilow, ihigh, v);
Py_DECREF(v);
return ret;
}
PyOS_snprintf(msg, sizeof(msg),
"must assign sequence"
" (not \"%.200s\") to slice",
v->ob_type->tp_name);
v_as_SF = PySequence_Fast(v, msg);
if(v_as_SF == NULL)
return -1;
n = PySequence_Fast_GET_SIZE(v_as_SF);
}
if (ilow < 0)
ilow = 0;
else if (ilow > a->ob_size)
ilow = a->ob_size;
if (ihigh < ilow)
ihigh = ilow;
else if (ihigh > a->ob_size)
ihigh = a->ob_size;
item = a->ob_item;
d = n - (ihigh-ilow);
if (ihigh > ilow) {
p = recycle = PyMem_NEW(PyObject *, (ihigh-ilow));
if (recycle == NULL) {
PyErr_NoMemory();
return -1;
}
}
else
p = recycle = NULL;
if (d <= 0) { /* Delete -d items; recycle ihigh-ilow items */
for (k = ilow; k < ihigh; k++)
*p++ = item[k];
if (d < 0) {
for (/*k = ihigh*/; k < a->ob_size; k++)
item[k+d] = item[k];
a->ob_size += d;
NRESIZE(item, PyObject *, a->ob_size); /* Can't fail */
a->ob_item = item;
}
}
else { /* Insert d items; recycle ihigh-ilow items */
NRESIZE(item, PyObject *, a->ob_size + d);
if (item == NULL) {
if (recycle != NULL)
PyMem_DEL(recycle);
PyErr_NoMemory();
return -1;
}
for (k = a->ob_size; --k >= ihigh; )
item[k+d] = item[k];
for (/*k = ihigh-1*/; k >= ilow; --k)
*p++ = item[k];
a->ob_item = item;
a->ob_size += d;
}
for (k = 0; k < n; k++, ilow++) {
PyObject *w = PySequence_Fast_GET_ITEM(v_as_SF, k);
Py_XINCREF(w);
item[ilow] = w;
}
if (recycle) {
while (--p >= recycle)
Py_XDECREF(*p);
PyMem_DEL(recycle);
}
if (a->ob_size == 0 && a->ob_item != NULL) {
PyMem_FREE(a->ob_item);
a->ob_item = NULL;
}
Py_XDECREF(v_as_SF);
return 0;
#undef b
}
int
PyList_SetSlice(PyObject *a, int ilow, int ihigh, PyObject *v)
{
if (!PyList_Check(a)) {
PyErr_BadInternalCall();
return -1;
}
return list_ass_slice((PyListObject *)a, ilow, ihigh, v);
}
static PyObject *
list_inplace_repeat(PyListObject *self, int n)
{
PyObject **items;
int size, i, j;
size = PyList_GET_SIZE(self);
if (size == 0) {
Py_INCREF(self);
return (PyObject *)self;
}
items = self->ob_item;
if (n < 1) {
self->ob_item = NULL;
self->ob_size = 0;
for (i = 0; i < size; i++)
Py_XDECREF(items[i]);
PyMem_DEL(items);
Py_INCREF(self);
return (PyObject *)self;
}
NRESIZE(items, PyObject*, size*n);
if (items == NULL) {
PyErr_NoMemory();
goto finally;
}
self->ob_item = items;
for (i = 1; i < n; i++) { /* Start counting at 1, not 0 */
for (j = 0; j < size; j++) {
PyObject *o = PyList_GET_ITEM(self, j);
Py_INCREF(o);
PyList_SET_ITEM(self, self->ob_size++, o);
}
}
Py_INCREF(self);
return (PyObject *)self;
finally:
return NULL;
}
static int
list_ass_item(PyListObject *a, int i, PyObject *v)
{
PyObject *old_value;
if (i < 0 || i >= a->ob_size) {
PyErr_SetString(PyExc_IndexError,
"list assignment index out of range");
return -1;
}
if (v == NULL)
return list_ass_slice(a, i, i+1, v);
Py_INCREF(v);
old_value = a->ob_item[i];
a->ob_item[i] = v;
Py_DECREF(old_value);
return 0;
}
static PyObject *
ins(PyListObject *self, int where, PyObject *v)
{
if (ins1(self, where, v) != 0)
return NULL;
Py_INCREF(Py_None);
return Py_None;
}
static PyObject *
listinsert(PyListObject *self, PyObject *args)
{
int i;
PyObject *v;
if (!PyArg_ParseTuple(args, "iO:insert", &i, &v))
return NULL;
return ins(self, i, v);
}
static PyObject *
listappend(PyListObject *self, PyObject *v)
{
return ins(self, (int) self->ob_size, v);
}
static int
listextend_internal(PyListObject *self, PyObject *b)
{
PyObject **items;
int selflen = PyList_GET_SIZE(self);
int blen;
register int i;
if (PyObject_Size(b) == 0) {
/* short circuit when b is empty */
Py_DECREF(b);
return 0;
}
if (self == (PyListObject*)b) {
/* as in list_ass_slice() we must special case the
* situation: a.extend(a)
*
* XXX: I think this way ought to be faster than using
* list_slice() the way list_ass_slice() does.
*/
Py_DECREF(b);
b = PyList_New(selflen);
if (!b)
return -1;
for (i = 0; i < selflen; i++) {
PyObject *o = PyList_GET_ITEM(self, i);
Py_INCREF(o);
PyList_SET_ITEM(b, i, o);
}
}
blen = PyObject_Size(b);
/* resize a using idiom */
items = self->ob_item;
NRESIZE(items, PyObject*, selflen + blen);
if (items == NULL) {
PyErr_NoMemory();
Py_DECREF(b);
return -1;
}
self->ob_item = items;
/* populate the end of self with b's items */
for (i = 0; i < blen; i++) {
PyObject *o = PySequence_Fast_GET_ITEM(b, i);
Py_INCREF(o);
PyList_SET_ITEM(self, self->ob_size++, o);
}
Py_DECREF(b);
return 0;
}
static PyObject *
list_inplace_concat(PyListObject *self, PyObject *other)
{
other = PySequence_Fast(other, "argument to += must be iterable");
if (!other)
return NULL;
if (listextend_internal(self, other) < 0)
return NULL;
Py_INCREF(self);
return (PyObject *)self;
}
static PyObject *
listextend(PyListObject *self, PyObject *b)
{
b = PySequence_Fast(b, "list.extend() argument must be iterable");
if (!b)
return NULL;
if (listextend_internal(self, b) < 0)
return NULL;
Py_INCREF(Py_None);
return Py_None;
}
static PyObject *
listpop(PyListObject *self, PyObject *args)
{
int i = -1;
PyObject *v;
if (!PyArg_ParseTuple(args, "|i:pop", &i))
return NULL;
if (self->ob_size == 0) {
/* Special-case most common failure cause */
PyErr_SetString(PyExc_IndexError, "pop from empty list");
return NULL;
}
if (i < 0)
i += self->ob_size;
if (i < 0 || i >= self->ob_size) {
PyErr_SetString(PyExc_IndexError, "pop index out of range");
return NULL;
}
v = self->ob_item[i];
Py_INCREF(v);
if (list_ass_slice(self, i, i+1, (PyObject *)NULL) != 0) {
Py_DECREF(v);
return NULL;
}
return v;
}
/* Reverse a slice of a list in place, from lo up to (exclusive) hi. */
static void
reverse_slice(PyObject **lo, PyObject **hi)
{
assert(lo && hi);
--hi;
while (lo < hi) {
PyObject *t = *lo;
*lo = *hi;
*hi = t;
++lo;
--hi;
}
}
/* Lots of code for an adaptive, stable, natural mergesort. There are many
* pieces to this algorithm; read listsort.txt for overviews and details.
*/
/* Comparison function. Takes care of calling a user-supplied
* comparison function (any callable Python object), which must not be
* NULL (use the ISLT macro if you don't know, or call PyObject_RichCompareBool
* with Py_LT if you know it's NULL).
* Returns -1 on error, 1 if x < y, 0 if x >= y.
*/
static int
islt(PyObject *x, PyObject *y, PyObject *compare)
{
PyObject *res;
PyObject *args;
int i;
assert(compare != NULL);
/* Call the user's comparison function and translate the 3-way
* result into true or false (or error).
*/
args = PyTuple_New(2);
if (args == NULL)
return -1;
Py_INCREF(x);
Py_INCREF(y);
PyTuple_SET_ITEM(args, 0, x);
PyTuple_SET_ITEM(args, 1, y);
res = PyObject_Call(compare, args, NULL);
Py_DECREF(args);
if (res == NULL)
return -1;
if (!PyInt_Check(res)) {
Py_DECREF(res);
PyErr_SetString(PyExc_TypeError,
"comparison function must return int");
return -1;
}
i = PyInt_AsLong(res);
Py_DECREF(res);
return i < 0;
}
/* If COMPARE is NULL, calls PyObject_RichCompareBool with Py_LT, else calls
* islt. This avoids a layer of function call in the usual case, and
* sorting does many comparisons.
* Returns -1 on error, 1 if x < y, 0 if x >= y.
*/
#define ISLT(X, Y, COMPARE) ((COMPARE) == NULL ? \
PyObject_RichCompareBool(X, Y, Py_LT) : \
islt(X, Y, COMPARE))
/* Compare X to Y via "<". Goto "fail" if the comparison raises an
error. Else "k" is set to true iff X<Y, and an "if (k)" block is
started. It makes more sense in context <wink>. X and Y are PyObject*s.
*/
#define IFLT(X, Y) if ((k = ISLT(X, Y, compare)) < 0) goto fail; \
if (k)
/* binarysort is the best method for sorting small arrays: it does
few compares, but can do data movement quadratic in the number of
elements.
[lo, hi) is a contiguous slice of a list, and is sorted via
binary insertion. This sort is stable.
On entry, must have lo <= start <= hi, and that [lo, start) is already
sorted (pass start == lo if you don't know!).
If islt() complains return -1, else 0.
Even in case of error, the output slice will be some permutation of
the input (nothing is lost or duplicated).
*/
static int
binarysort(PyObject **lo, PyObject **hi, PyObject **start, PyObject *compare)
/* compare -- comparison function object, or NULL for default */
{
register int k;
register PyObject **l, **p, **r;
register PyObject *pivot;
assert(lo <= start && start <= hi);
/* assert [lo, start) is sorted */
if (lo == start)
++start;
for (; start < hi; ++start) {
/* set l to where *start belongs */
l = lo;
r = start;
pivot = *r;
/* Invariants:
* pivot >= all in [lo, l).
* pivot < all in [r, start).
* The second is vacuously true at the start.
*/
assert(l < r);
do {
p = l + ((r - l) >> 1);
IFLT(pivot, *p)
r = p;
else
l = p+1;
} while (l < r);
assert(l == r);
/* The invariants still hold, so pivot >= all in [lo, l) and
pivot < all in [l, start), so pivot belongs at l. Note
that if there are elements equal to pivot, l points to the
first slot after them -- that's why this sort is stable.
Slide over to make room.
Caution: using memmove is much slower under MSVC 5;
we're not usually moving many slots. */
for (p = start; p > l; --p)
*p = *(p-1);
*l = pivot;
}
return 0;
fail:
return -1;
}
/*
Return the length of the run beginning at lo, in the slice [lo, hi). lo < hi
is required on entry. "A run" is the longest ascending sequence, with
lo[0] <= lo[1] <= lo[2] <= ...
or the longest descending sequence, with
lo[0] > lo[1] > lo[2] > ...
Boolean *descending is set to 0 in the former case, or to 1 in the latter.
For its intended use in a stable mergesort, the strictness of the defn of
"descending" is needed so that the caller can safely reverse a descending
sequence without violating stability (strict > ensures there are no equal
elements to get out of order).
Returns -1 in case of error.
*/
static int
count_run(PyObject **lo, PyObject **hi, PyObject *compare, int *descending)
{
int k;
int n;
assert(lo < hi);
*descending = 0;
++lo;
if (lo == hi)
return 1;
n = 2;
IFLT(*lo, *(lo-1)) {
*descending = 1;
for (lo = lo+1; lo < hi; ++lo, ++n) {
IFLT(*lo, *(lo-1))
;
else
break;
}
}
else {
for (lo = lo+1; lo < hi; ++lo, ++n) {
IFLT(*lo, *(lo-1))
break;
}
}
return n;
fail:
return -1;
}
/*
Locate the proper position of key in a sorted vector; if the vector contains
an element equal to key, return the position immediately to the left of
the leftmost equal element. [gallop_right() does the same except returns
the position to the right of the rightmost equal element (if any).]
"a" is a sorted vector with n elements, starting at a[0]. n must be > 0.
"hint" is an index at which to begin the search, 0 <= hint < n. The closer
hint is to the final result, the faster this runs.
The return value is the int k in 0..n such that
a[k-1] < key <= a[k]
pretending that *(a-1) is minus infinity and a[n] is plus infinity. IOW,
key belongs at index k; or, IOW, the first k elements of a should precede
key, and the last n-k should follow key.
Returns -1 on error. See listsort.txt for info on the method.
*/
static int
gallop_left(PyObject *key, PyObject **a, int n, int hint, PyObject *compare)
{
int ofs;
int lastofs;
int k;
assert(key && a && n > 0 && hint >= 0 && hint < n);
a += hint;
lastofs = 0;
ofs = 1;
IFLT(*a, key) {
/* a[hint] < key -- gallop right, until
* a[hint + lastofs] < key <= a[hint + ofs]
*/
const int maxofs = n - hint; /* &a[n-1] is highest */
while (ofs < maxofs) {
IFLT(a[ofs], key) {
lastofs = ofs;
ofs = (ofs << 1) + 1;
if (ofs <= 0) /* int overflow */
ofs = maxofs;
}
else /* key <= a[hint + ofs] */