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Document some reverse-engineered invariants and pragmatic hints.

This commit is contained in:
Tim Peters 2004-10-01 01:32:53 +00:00
parent e644a1b921
commit d8768d3294
1 changed files with 17 additions and 2 deletions
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19
Modules/collectionsmodule.c
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@ -9,6 +9,21 @@
#define BLOCKLEN 46
/* A `dequeobject` is composed of a doubly-linked list of `block` nodes.
* This list is not circular (the leftmost block has leftlink==NULL,
* and the rightmost block has rightlink==NULL). A deque d's first
* element is at d.leftblock[leftindex] and its last element is at
* d.rightblock[rightindex]; note that, unlike as for Python slice
* indices, this indices are inclusive on both ends.
* The list of blocks is never empty. An empty deque d has
* d.leftblock == d.rightblock != NULL; d.len == 0; and
* d.leftindex > d.rightindex; checking for d.len == 0 is the intended
* way to see whether d is empty.
* Note that since d.leftindex and d.rightindex may be indices into
* distinct blocks (and certainly are, for and d with len(d) > BLOCKLEN),
* it's not generally true that d.leftindex <= d.rightindex.
*/
typedef struct BLOCK {
struct BLOCK *leftlink;
struct BLOCK *rightlink;
@ -31,8 +46,8 @@ typedef struct {
PyObject_HEAD
block *leftblock;
block *rightblock;
int leftindex;
int rightindex;
int leftindex; /* in range(BLOCKLEN) */
int rightindex; /* in range(BLOCKLEN) */
int len;
PyObject *weakreflist; /* List of weak references */
} dequeobject;