diff options
Diffstat (limited to 'deps/jemalloc/include/jemalloc/internal/qr.h')
| -rw-r--r-- | deps/jemalloc/include/jemalloc/internal/qr.h | 130 |
1 files changed, 99 insertions, 31 deletions
diff --git a/deps/jemalloc/include/jemalloc/internal/qr.h b/deps/jemalloc/include/jemalloc/internal/qr.h index 1e1056b38..ece4f5568 100644 --- a/deps/jemalloc/include/jemalloc/internal/qr.h +++ b/deps/jemalloc/include/jemalloc/internal/qr.h @@ -1,6 +1,21 @@ #ifndef JEMALLOC_INTERNAL_QR_H #define JEMALLOC_INTERNAL_QR_H +/* + * A ring implementation based on an embedded circular doubly-linked list. + * + * You define your struct like so: + * + * typedef struct my_s my_t; + * struct my_s { + * int data; + * qr(my_t) my_link; + * }; + * + * And then pass a my_t * into macros for a_qr arguments, and the token + * "my_link" into a_field fields. + */ + /* Ring definitions. */ #define qr(a_type) \ struct { \ @@ -8,61 +23,114 @@ struct { \ a_type *qre_prev; \ } -/* Ring functions. */ +/* + * Initialize a qr link. Every link must be initialized before being used, even + * if that initialization is going to be immediately overwritten (say, by being + * passed into an insertion macro). + */ #define qr_new(a_qr, a_field) do { \ (a_qr)->a_field.qre_next = (a_qr); \ (a_qr)->a_field.qre_prev = (a_qr); \ } while (0) +/* + * Go forwards or backwards in the ring. Note that (the ring being circular), this + * always succeeds -- you just keep looping around and around the ring if you + * chase pointers without end. + */ #define qr_next(a_qr, a_field) ((a_qr)->a_field.qre_next) - #define qr_prev(a_qr, a_field) ((a_qr)->a_field.qre_prev) -#define qr_before_insert(a_qrelm, a_qr, a_field) do { \ - (a_qr)->a_field.qre_prev = (a_qrelm)->a_field.qre_prev; \ - (a_qr)->a_field.qre_next = (a_qrelm); \ - (a_qr)->a_field.qre_prev->a_field.qre_next = (a_qr); \ - (a_qrelm)->a_field.qre_prev = (a_qr); \ +/* + * Given two rings: + * a -> a_1 -> ... -> a_n -- + * ^ | + * |------------------------ + * + * b -> b_1 -> ... -> b_n -- + * ^ | + * |------------------------ + * + * Results in the ring: + * a -> a_1 -> ... -> a_n -> b -> b_1 -> ... -> b_n -- + * ^ | + * |-------------------------------------------------| + * + * a_qr_a can directly be a qr_next() macro, but a_qr_b cannot. + */ +#define qr_meld(a_qr_a, a_qr_b, a_field) do { \ + (a_qr_b)->a_field.qre_prev->a_field.qre_next = \ + (a_qr_a)->a_field.qre_prev; \ + (a_qr_a)->a_field.qre_prev = (a_qr_b)->a_field.qre_prev; \ + (a_qr_b)->a_field.qre_prev = \ + (a_qr_b)->a_field.qre_prev->a_field.qre_next; \ + (a_qr_a)->a_field.qre_prev->a_field.qre_next = (a_qr_a); \ + (a_qr_b)->a_field.qre_prev->a_field.qre_next = (a_qr_b); \ } while (0) -#define qr_after_insert(a_qrelm, a_qr, a_field) do { \ - (a_qr)->a_field.qre_next = (a_qrelm)->a_field.qre_next; \ - (a_qr)->a_field.qre_prev = (a_qrelm); \ - (a_qr)->a_field.qre_next->a_field.qre_prev = (a_qr); \ - (a_qrelm)->a_field.qre_next = (a_qr); \ -} while (0) +/* + * Logically, this is just a meld. The intent, though, is that a_qrelm is a + * single-element ring, so that "before" has a more obvious interpretation than + * meld. + */ +#define qr_before_insert(a_qrelm, a_qr, a_field) \ + qr_meld((a_qrelm), (a_qr), a_field) -#define qr_meld(a_qr_a, a_qr_b, a_type, a_field) do { \ - a_type *t; \ - (a_qr_a)->a_field.qre_prev->a_field.qre_next = (a_qr_b); \ - (a_qr_b)->a_field.qre_prev->a_field.qre_next = (a_qr_a); \ - t = (a_qr_a)->a_field.qre_prev; \ - (a_qr_a)->a_field.qre_prev = (a_qr_b)->a_field.qre_prev; \ - (a_qr_b)->a_field.qre_prev = t; \ -} while (0) +/* Ditto, but inserting after rather than before. */ +#define qr_after_insert(a_qrelm, a_qr, a_field) \ + qr_before_insert(qr_next(a_qrelm, a_field), (a_qr), a_field) /* + * Inverts meld; given the ring: + * a -> a_1 -> ... -> a_n -> b -> b_1 -> ... -> b_n -- + * ^ | + * |-------------------------------------------------| + * + * Results in two rings: + * a -> a_1 -> ... -> a_n -- + * ^ | + * |------------------------ + * + * b -> b_1 -> ... -> b_n -- + * ^ | + * |------------------------ + * * qr_meld() and qr_split() are functionally equivalent, so there's no need to * have two copies of the code. */ -#define qr_split(a_qr_a, a_qr_b, a_type, a_field) \ - qr_meld((a_qr_a), (a_qr_b), a_type, a_field) +#define qr_split(a_qr_a, a_qr_b, a_field) \ + qr_meld((a_qr_a), (a_qr_b), a_field) -#define qr_remove(a_qr, a_field) do { \ - (a_qr)->a_field.qre_prev->a_field.qre_next \ - = (a_qr)->a_field.qre_next; \ - (a_qr)->a_field.qre_next->a_field.qre_prev \ - = (a_qr)->a_field.qre_prev; \ - (a_qr)->a_field.qre_next = (a_qr); \ - (a_qr)->a_field.qre_prev = (a_qr); \ -} while (0) +/* + * Splits off a_qr from the rest of its ring, so that it becomes a + * single-element ring. + */ +#define qr_remove(a_qr, a_field) \ + qr_split(qr_next(a_qr, a_field), (a_qr), a_field) +/* + * Helper macro to iterate over each element in a ring exactly once, starting + * with a_qr. The usage is (assuming my_t defined as above): + * + * int sum(my_t *item) { + * int sum = 0; + * my_t *iter; + * qr_foreach(iter, item, link) { + * sum += iter->data; + * } + * return sum; + * } + */ #define qr_foreach(var, a_qr, a_field) \ for ((var) = (a_qr); \ (var) != NULL; \ (var) = (((var)->a_field.qre_next != (a_qr)) \ ? (var)->a_field.qre_next : NULL)) +/* + * The same (and with the same usage) as qr_foreach, but in the opposite order, + * ending with a_qr. + */ #define qr_reverse_foreach(var, a_qr, a_field) \ for ((var) = ((a_qr) != NULL) ? qr_prev(a_qr, a_field) : NULL; \ (var) != NULL; \ |