From: Mathieu Desnoyers Date: Thu, 16 Jun 2011 19:29:38 +0000 (-0400) Subject: lttng priority heap initial import X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=00fd5ee1c3ce5de45f62036ac555294887f2ef8d;p=ust.git lttng priority heap initial import Signed-off-by: Mathieu Desnoyers --- diff --git a/libprio_heap/lttng_prio_heap.c b/libprio_heap/lttng_prio_heap.c new file mode 100644 index 0000000..5bbd079 --- /dev/null +++ b/libprio_heap/lttng_prio_heap.c @@ -0,0 +1,206 @@ +/* + * lttng_prio_heap.c + * + * Priority heap containing pointers. Based on CLRS, chapter 6. + * + * Copyright 2011 - Mathieu Desnoyers + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + */ + +#include +#include "lttng_prio_heap.h" + +#ifdef DEBUG_HEAP +void lttng_check_heap(const struct lttng_ptr_heap *heap) +{ + size_t i; + + if (!heap->len) + return; + + for (i = 1; i < heap->len; i++) + WARN_ON_ONCE(!heap->gt(heap->ptrs[i], heap->ptrs[0])); +} +#endif + +static +size_t parent(size_t i) +{ + return (i -1) >> 1; +} + +static +size_t left(size_t i) +{ + return (i << 1) + 1; +} + +static +size_t right(size_t i) +{ + return (i << 1) + 2; +} + +/* + * Copy of heap->ptrs pointer is invalid after heap_grow. + */ +static +int heap_grow(struct lttng_ptr_heap *heap, size_t new_len) +{ + void **new_ptrs; + + if (heap->alloc_len >= new_len) + return 0; + + heap->alloc_len = max_t(size_t, new_len, heap->alloc_len << 1); + new_ptrs = kmalloc(heap->alloc_len * sizeof(void *), heap->gfpmask); + if (!new_ptrs) + return -ENOMEM; + if (heap->ptrs) + memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *)); + kfree(heap->ptrs); + heap->ptrs = new_ptrs; + return 0; +} + +static +int heap_set_len(struct lttng_ptr_heap *heap, size_t new_len) +{ + int ret; + + ret = heap_grow(heap, new_len); + if (ret) + return ret; + heap->len = new_len; + return 0; +} + +int lttng_heap_init(struct lttng_ptr_heap *heap, size_t alloc_len, + gfp_t gfpmask, int gt(void *a, void *b)) +{ + heap->ptrs = NULL; + heap->len = 0; + heap->alloc_len = 0; + heap->gt = gt; + /* + * Minimum size allocated is 1 entry to ensure memory allocation + * never fails within heap_replace_max. + */ + return heap_grow(heap, max_t(size_t, 1, alloc_len)); +} + +void lttng_heap_free(struct lttng_ptr_heap *heap) +{ + kfree(heap->ptrs); +} + +static void heapify(struct lttng_ptr_heap *heap, size_t i) +{ + void **ptrs = heap->ptrs; + size_t l, r, largest; + + for (;;) { + void *tmp; + + l = left(i); + r = right(i); + if (l < heap->len && heap->gt(ptrs[l], ptrs[i])) + largest = l; + else + largest = i; + if (r < heap->len && heap->gt(ptrs[r], ptrs[largest])) + largest = r; + if (largest == i) + break; + tmp = ptrs[i]; + ptrs[i] = ptrs[largest]; + ptrs[largest] = tmp; + i = largest; + } + lttng_check_heap(heap); +} + +void *lttng_heap_replace_max(struct lttng_ptr_heap *heap, void *p) +{ + void *res; + + if (!heap->len) { + (void) heap_set_len(heap, 1); + heap->ptrs[0] = p; + lttng_check_heap(heap); + return NULL; + } + + /* Replace the current max and heapify */ + res = heap->ptrs[0]; + heap->ptrs[0] = p; + heapify(heap, 0); + return res; +} + +int lttng_heap_insert(struct lttng_ptr_heap *heap, void *p) +{ + void **ptrs; + size_t pos; + int ret; + + ret = heap_set_len(heap, heap->len + 1); + if (ret) + return ret; + ptrs = heap->ptrs; + pos = heap->len - 1; + while (pos > 0 && heap->gt(p, ptrs[parent(pos)])) { + /* Move parent down until we find the right spot */ + ptrs[pos] = ptrs[parent(pos)]; + pos = parent(pos); + } + ptrs[pos] = p; + lttng_check_heap(heap); + return 0; +} + +void *lttng_heap_remove(struct lttng_ptr_heap *heap) +{ + switch (heap->len) { + case 0: + return NULL; + case 1: + (void) heap_set_len(heap, 0); + return heap->ptrs[0]; + } + /* Shrink, replace the current max by previous last entry and heapify */ + heap_set_len(heap, heap->len - 1); + /* len changed. previous last entry is at heap->len */ + return lttng_heap_replace_max(heap, heap->ptrs[heap->len]); +} + +void *lttng_heap_cherrypick(struct lttng_ptr_heap *heap, void *p) +{ + size_t pos, len = heap->len; + + for (pos = 0; pos < len; pos++) + if (heap->ptrs[pos] == p) + goto found; + return NULL; +found: + if (heap->len == 1) { + (void) heap_set_len(heap, 0); + lttng_check_heap(heap); + return heap->ptrs[0]; + } + /* Replace p with previous last entry and heapify. */ + heap_set_len(heap, heap->len - 1); + /* len changed. previous last entry is at heap->len */ + heap->ptrs[pos] = heap->ptrs[heap->len]; + heapify(heap, pos); + return p; +} diff --git a/libprio_heap/lttng_prio_heap.h b/libprio_heap/lttng_prio_heap.h new file mode 100644 index 0000000..ea8dbb8 --- /dev/null +++ b/libprio_heap/lttng_prio_heap.h @@ -0,0 +1,117 @@ +#ifndef _LTTNG_PRIO_HEAP_H +#define _LTTNG_PRIO_HEAP_H + +/* + * lttng_prio_heap.h + * + * Priority heap containing pointers. Based on CLRS, chapter 6. + * + * Copyright 2011 - Mathieu Desnoyers + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + */ + +#include + +struct lttng_ptr_heap { + size_t len, alloc_len; + void **ptrs; + int (*gt)(void *a, void *b); + gfp_t gfpmask; +}; + +#ifdef DEBUG_HEAP +void lttng_check_heap(const struct lttng_ptr_heap *heap); +#else +static inline +void lttng_check_heap(const struct lttng_ptr_heap *heap) +{ +} +#endif + +/** + * lttng_heap_maximum - return the largest element in the heap + * @heap: the heap to be operated on + * + * Returns the largest element in the heap, without performing any modification + * to the heap structure. Returns NULL if the heap is empty. + */ +static inline void *lttng_heap_maximum(const struct lttng_ptr_heap *heap) +{ + lttng_check_heap(heap); + return heap->len ? heap->ptrs[0] : NULL; +} + +/** + * lttng_heap_init - initialize the heap + * @heap: the heap to initialize + * @alloc_len: number of elements initially allocated + * @gfp: allocation flags + * @gt: function to compare the elements + * + * Returns -ENOMEM if out of memory. + */ +extern int lttng_heap_init(struct lttng_ptr_heap *heap, + size_t alloc_len, gfp_t gfpmask, + int gt(void *a, void *b)); + +/** + * lttng_heap_free - free the heap + * @heap: the heap to free + */ +extern void lttng_heap_free(struct lttng_ptr_heap *heap); + +/** + * lttng_heap_insert - insert an element into the heap + * @heap: the heap to be operated on + * @p: the element to add + * + * Insert an element into the heap. + * + * Returns -ENOMEM if out of memory. + */ +extern int lttng_heap_insert(struct lttng_ptr_heap *heap, void *p); + +/** + * lttng_heap_remove - remove the largest element from the heap + * @heap: the heap to be operated on + * + * Returns the largest element in the heap. It removes this element from the + * heap. Returns NULL if the heap is empty. + */ +extern void *lttng_heap_remove(struct lttng_ptr_heap *heap); + +/** + * lttng_heap_cherrypick - remove a given element from the heap + * @heap: the heap to be operated on + * @p: the element + * + * Remove the given element from the heap. Return the element if present, else + * return NULL. This algorithm has a complexity of O(n), which is higher than + * O(log(n)) provided by the rest of this API. + */ +extern void *lttng_heap_cherrypick(struct lttng_ptr_heap *heap, void *p); + +/** + * lttng_heap_replace_max - replace the the largest element from the heap + * @heap: the heap to be operated on + * @p: the pointer to be inserted as topmost element replacement + * + * Returns the largest element in the heap. It removes this element from the + * heap. The heap is rebalanced only once after the insertion. Returns NULL if + * the heap is empty. + * + * This is the equivalent of calling heap_remove() and then heap_insert(), but + * it only rebalances the heap once. It never allocates memory. + */ +extern void *lttng_heap_replace_max(struct lttng_ptr_heap *heap, void *p); + +#endif /* _LTTNG_PRIO_HEAP_H */