diff options
| -rw-r--r-- | Objects/listobject.c | 82 |
1 files changed, 32 insertions, 50 deletions
diff --git a/Objects/listobject.c b/Objects/listobject.c index ce78fff..f2132b4 100644 --- a/Objects/listobject.c +++ b/Objects/listobject.c @@ -758,39 +758,28 @@ reverse_slice(PyObject **lo, PyObject **hi) /* New quicksort implementation for arrays of object pointers. Thanks to discussions with Tim Peters. */ -/* CMPERROR is returned by our comparison function when an error - occurred. This is the largest negative integer (0x80000000 on a - 32-bit system). */ -#define CMPERROR ( (int) ((unsigned int)1 << (8*sizeof(int) - 1)) ) - /* Comparison function. Takes care of calling a user-supplied comparison function (any callable Python object). Calls the - standard comparison function, PyObject_Compare(), if the user- - supplied function is NULL. */ + standard comparison function, PyObject_RichCompareBool(), if the user- + supplied function is NULL. + Returns <0 on error, >0 if x < y, 0 if x >= y. */ static int -docompare(PyObject *x, PyObject *y, PyObject *compare) +islt(PyObject *x, PyObject *y, PyObject *compare) { PyObject *res; PyObject *args; int i; - if (compare == NULL) { - /* NOTE: we rely on the fact here that the sorting algorithm - only ever checks whether k<0, i.e., whether x<y. So we - invoke the rich comparison function with Py_LT ('<'), and - return -1 when it returns true and 0 when it returns - false. */ - i = PyObject_RichCompareBool(x, y, Py_LT); - if (i < 0) - return CMPERROR; - else - return -i; - } + if (compare == NULL) + return PyObject_RichCompareBool(x, y, Py_LT); + /* 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 CMPERROR; + return -1; Py_INCREF(x); Py_INCREF(y); PyTuple_SET_ITEM(args, 0, x); @@ -798,20 +787,16 @@ docompare(PyObject *x, PyObject *y, PyObject *compare) res = PyObject_Call(compare, args, NULL); Py_DECREF(args); if (res == NULL) - return CMPERROR; + return -1; if (!PyInt_Check(res)) { Py_DECREF(res); PyErr_SetString(PyExc_TypeError, "comparison function must return int"); - return CMPERROR; + return -1; } i = PyInt_AsLong(res); Py_DECREF(res); - if (i < 0) - return -1; - if (i > 0) - return 1; - return 0; + return i < 0; } /* MINSIZE is the smallest array that will get a full-blown samplesort @@ -850,17 +835,21 @@ docompare(PyObject *x, PyObject *y, PyObject *compare) exactly in two. */ #define STACKSIZE 60 - -#define SETK(X,Y) if ((k = docompare(X,Y,compare))==CMPERROR) goto fail +/* Compare X to Y via islt(). 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. + 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 docompare complains (returns CMPERROR) return -1, else 0. + 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). */ @@ -869,12 +858,12 @@ static int binarysort(PyObject **lo, PyObject **hi, PyObject **start, PyObject *compare) /* compare -- comparison function object, or NULL for default */ { - /* assert lo <= start <= hi - assert [lo, start) is sorted */ 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) { @@ -884,8 +873,7 @@ binarysort(PyObject **lo, PyObject **hi, PyObject **start, PyObject *compare) pivot = *r; do { p = l + ((r - l) >> 1); - SETK(pivot, *p); - if (k < 0) + IFLT(pivot, *p) r = p; else l = p + 1; @@ -906,7 +894,7 @@ binarysort(PyObject **lo, PyObject **hi, PyObject **start, PyObject *compare) /* samplesortslice is the sorting workhorse. [lo, hi) is a contiguous slice of a list, to be sorted in place. On entry, must have lo <= hi, - If docompare complains (returns CMPERROR) return -1, else 0. + 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). @@ -1023,8 +1011,7 @@ samplesortslice(PyObject **lo, PyObject **hi, PyObject *compare) */ /* assert lo < hi */ for (r = lo+1; r < hi; ++r) { - SETK(*r, *(r-1)); - if (k < 0) + IFLT(*r, *(r-1)) break; } /* [lo,r) is sorted, [r,hi) unknown. Get out cheap if there are @@ -1036,8 +1023,7 @@ samplesortslice(PyObject **lo, PyObject **hi, PyObject *compare) benchmark-driven silliness <wink>. */ /* assert lo < hi */ for (r = lo+1; r < hi; ++r) { - SETK(*(r-1), *r); - if (k < 0) + IFLT(*(r-1), *r) break; } if (hi - r <= MAXMERGE) { @@ -1192,8 +1178,7 @@ samplesortslice(PyObject **lo, PyObject **hi, PyObject *compare) do { /* slide l right, looking for key >= pivot */ do { - SETK(*l, pivot); - if (k < 0) + IFLT(*l, pivot) ++l; else break; @@ -1202,8 +1187,7 @@ samplesortslice(PyObject **lo, PyObject **hi, PyObject *compare) /* slide r left, looking for key < pivot */ while (l < r) { register PyObject *rval = *r--; - SETK(rval, pivot); - if (k < 0) { + IFLT(rval, pivot) { /* swap and advance */ r[1] = *l; *l++ = rval; @@ -1219,8 +1203,7 @@ samplesortslice(PyObject **lo, PyObject **hi, PyObject *compare) everything to the right of r is >= pivot */ if (l == r) { - SETK(*r, pivot); - if (k < 0) + IFLT(*r, pivot) ++l; else --r; @@ -1249,8 +1232,7 @@ samplesortslice(PyObject **lo, PyObject **hi, PyObject *compare) */ while (l < hi) { /* pivot <= *l known */ - SETK(pivot, *l); - if (k < 0) + IFLT(pivot, *l) break; else /* <= and not < implies == */ @@ -1290,7 +1272,7 @@ samplesortslice(PyObject **lo, PyObject **hi, PyObject *compare) return -1; } -#undef SETK +#undef IFLT static PyTypeObject immutable_list_type; |