diff options
Diffstat (limited to 'Modules')
| -rw-r--r-- | Modules/collectionsmodule.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/Modules/collectionsmodule.c b/Modules/collectionsmodule.c index 5856b11..03e09c9 100644 --- a/Modules/collectionsmodule.c +++ b/Modules/collectionsmodule.c @@ -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; |