diff options
| -rw-r--r-- | include/linux/min_heap.h | 134 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 10 | ||||
| -rw-r--r-- | lib/Makefile | 1 | ||||
| -rw-r--r-- | lib/test_min_heap.c | 194 |
4 files changed, 339 insertions, 0 deletions
diff --git a/include/linux/min_heap.h b/include/linux/min_heap.h new file mode 100644 index 000000000000..44077837385f --- /dev/null +++ b/include/linux/min_heap.h @@ -0,0 +1,134 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_MIN_HEAP_H +#define _LINUX_MIN_HEAP_H + +#include <linux/bug.h> +#include <linux/string.h> +#include <linux/types.h> + +/** + * struct min_heap - Data structure to hold a min-heap. + * @data: Start of array holding the heap elements. + * @nr: Number of elements currently in the heap. + * @size: Maximum number of elements that can be held in current storage. + */ +struct min_heap { + void *data; + int nr; + int size; +}; + +/** + * struct min_heap_callbacks - Data/functions to customise the min_heap. + * @elem_size: The nr of each element in bytes. + * @less: Partial order function for this heap. + * @swp: Swap elements function. + */ +struct min_heap_callbacks { + int elem_size; + bool (*less)(const void *lhs, const void *rhs); + void (*swp)(void *lhs, void *rhs); +}; + +/* Sift the element at pos down the heap. */ +static __always_inline +void min_heapify(struct min_heap *heap, int pos, + const struct min_heap_callbacks *func) +{ + void *left, *right, *parent, *smallest; + void *data = heap->data; + + for (;;) { + if (pos * 2 + 1 >= heap->nr) + break; + + left = data + ((pos * 2 + 1) * func->elem_size); + parent = data + (pos * func->elem_size); + smallest = parent; + if (func->less(left, smallest)) + smallest = left; + + if (pos * 2 + 2 < heap->nr) { + right = data + ((pos * 2 + 2) * func->elem_size); + if (func->less(right, smallest)) + smallest = right; + } + if (smallest == parent) + break; + func->swp(smallest, parent); + if (smallest == left) + pos = (pos * 2) + 1; + else + pos = (pos * 2) + 2; + } +} + +/* Floyd's approach to heapification that is O(nr). */ +static __always_inline +void min_heapify_all(struct min_heap *heap, + const struct min_heap_callbacks *func) +{ + int i; + + for (i = heap->nr / 2; i >= 0; i--) + min_heapify(heap, i, func); +} + +/* Remove minimum element from the heap, O(log2(nr)). */ +static __always_inline +void min_heap_pop(struct min_heap *heap, + const struct min_heap_callbacks *func) +{ + void *data = heap->data; + + if (WARN_ONCE(heap->nr <= 0, "Popping an empty heap")) + return; + + /* Place last element at the root (position 0) and then sift down. */ + heap->nr--; + memcpy(data, data + (heap->nr * func->elem_size), func->elem_size); + min_heapify(heap, 0, func); +} + +/* + * Remove the minimum element and then push the given element. The + * implementation performs 1 sift (O(log2(nr))) and is therefore more + * efficient than a pop followed by a push that does 2. + */ +static __always_inline +void min_heap_pop_push(struct min_heap *heap, + const void *element, + const struct min_heap_callbacks *func) +{ + memcpy(heap->data, element, func->elem_size); + min_heapify(heap, 0, func); +} + +/* Push an element on to the heap, O(log2(nr)). */ +static __always_inline +void min_heap_push(struct min_heap *heap, const void *element, + const struct min_heap_callbacks *func) +{ + void *data = heap->data; + void *child, *parent; + int pos; + + if (WARN_ONCE(heap->nr >= heap->size, "Pushing on a full heap")) + return; + + /* Place at the end of data. */ + pos = heap->nr; + memcpy(data + (pos * func->elem_size), element, func->elem_size); + heap->nr++; + + /* Sift child at pos up. */ + for (; pos > 0; pos = (pos - 1) / 2) { + child = data + (pos * func->elem_size); + parent = data + ((pos - 1) / 2) * func->elem_size; + if (func->less(parent, child)) + break; + func->swp(parent, child); + } +} + +#endif /* _LINUX_MIN_HEAP_H */ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 69def4a9df00..f04b61c1a1cc 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1769,6 +1769,16 @@ config TEST_LIST_SORT If unsure, say N. +config TEST_MIN_HEAP + tristate "Min heap test" + depends on DEBUG_KERNEL || m + help + Enable this to turn on min heap function tests. This test is + executed only once during system boot (so affects only boot time), + or at module load time. + + If unsure, say N. + config TEST_SORT tristate "Array-based sort test" depends on DEBUG_KERNEL || m diff --git a/lib/Makefile b/lib/Makefile index 611872c06926..09a8acb0cf92 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -67,6 +67,7 @@ CFLAGS_test_ubsan.o += $(call cc-disable-warning, vla) UBSAN_SANITIZE_test_ubsan.o := y obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o obj-$(CONFIG_TEST_LIST_SORT) += test_list_sort.o +obj-$(CONFIG_TEST_MIN_HEAP) += test_min_heap.o obj-$(CONFIG_TEST_LKM) += test_module.o obj-$(CONFIG_TEST_VMALLOC) += test_vmalloc.o obj-$(CONFIG_TEST_OVERFLOW) += test_overflow.o diff --git a/lib/test_min_heap.c b/lib/test_min_heap.c new file mode 100644 index 000000000000..d19c8080fd4d --- /dev/null +++ b/lib/test_min_heap.c @@ -0,0 +1,194 @@ +// SPDX-License-Identifier: GPL-2.0-only +#define pr_fmt(fmt) "min_heap_test: " fmt + +/* + * Test cases for the min max heap. + */ + +#include <linux/log2.h> +#include <linux/min_heap.h> +#include <linux/module.h> +#include <linux/printk.h> +#include <linux/random.h> + +static __init bool less_than(const void *lhs, const void *rhs) +{ + return *(int *)lhs < *(int *)rhs; +} + +static __init bool greater_than(const void *lhs, const void *rhs) +{ + return *(int *)lhs > *(int *)rhs; +} + +static __init void swap_ints(void *lhs, void *rhs) +{ + int temp = *(int *)lhs; + + *(int *)lhs = *(int *)rhs; + *(int *)rhs = temp; +} + +static __init int pop_verify_heap(bool min_heap, + struct min_heap *heap, + const struct min_heap_callbacks *funcs) +{ + int *values = heap->data; + int err = 0; + int last; + + last = values[0]; + min_heap_pop(heap, funcs); + while (heap->nr > 0) { + if (min_heap) { + if (last > values[0]) { + pr_err("error: expected %d <= %d\n", last, + values[0]); + err++; + } + } else { + if (last < values[0]) { + pr_err("error: expected %d >= %d\n", last, + values[0]); + err++; + } + } + last = values[0]; + min_heap_pop(heap, funcs); + } + return err; +} + +static __init int test_heapify_all(bool min_heap) +{ + int values[] = { 3, 1, 2, 4, 0x8000000, 0x7FFFFFF, 0, + -3, -1, -2, -4, 0x8000000, 0x7FFFFFF }; + struct min_heap heap = { + .data = values, + .nr = ARRAY_SIZE(values), + .size = ARRAY_SIZE(values), + }; + struct min_heap_callbacks funcs = { + .elem_size = sizeof(int), + .less = min_heap ? less_than : greater_than, + .swp = swap_ints, + }; + int i, err; + + /* Test with known set of values. */ + min_heapify_all(&heap, &funcs); + err = pop_verify_heap(min_heap, &heap, &funcs); + + + /* Test with randomly generated values. */ + heap.nr = ARRAY_SIZE(values); + for (i = 0; i < heap.nr; i++) + values[i] = get_random_int(); + + min_heapify_all(&heap, &funcs); + err += pop_verify_heap(min_heap, &heap, &funcs); + + return err; +} + +static __init int test_heap_push(bool min_heap) +{ + const int data[] = { 3, 1, 2, 4, 0x80000000, 0x7FFFFFFF, 0, + -3, -1, -2, -4, 0x80000000, 0x7FFFFFFF }; + int values[ARRAY_SIZE(data)]; + struct min_heap heap = { + .data = values, + .nr = 0, + .size = ARRAY_SIZE(values), + }; + struct min_heap_callbacks funcs = { + .elem_size = sizeof(int), + .less = min_heap ? less_than : greater_than, + .swp = swap_ints, + }; + int i, temp, err; + + /* Test with known set of values copied from data. */ + for (i = 0; i < ARRAY_SIZE(data); i++) + min_heap_push(&heap, &data[i], &funcs); + + err = pop_verify_heap(min_heap, &heap, &funcs); + + /* Test with randomly generated values. */ + while (heap.nr < heap.size) { + temp = get_random_int(); + min_heap_push(&heap, &temp, &funcs); + } + err += pop_verify_heap(min_heap, &heap, &funcs); + + return err; +} + +static __init int test_heap_pop_push(bool min_heap) +{ + const int data[] = { 3, 1, 2, 4, 0x80000000, 0x7FFFFFFF, 0, + -3, -1, -2, -4, 0x80000000, 0x7FFFFFFF }; + int values[ARRAY_SIZE(data)]; + struct min_heap heap = { + .data = values, + .nr = 0, + .size = ARRAY_SIZE(values), + }; + struct min_heap_callbacks funcs = { + .elem_size = sizeof(int), + .less = min_heap ? less_than : greater_than, + .swp = swap_ints, + }; + int i, temp, err; + + /* Fill values with data to pop and replace. */ + temp = min_heap ? 0x80000000 : 0x7FFFFFFF; + for (i = 0; i < ARRAY_SIZE(data); i++) + min_heap_push(&heap, &temp, &funcs); + + /* Test with known set of values copied from data. */ + for (i = 0; i < ARRAY_SIZE(data); i++) + min_heap_pop_push(&heap, &data[i], &funcs); + + err = pop_verify_heap(min_heap, &heap, &funcs); + + heap.nr = 0; + for (i = 0; i < ARRAY_SIZE(data); i++) + min_heap_push(&heap, &temp, &funcs); + + /* Test with randomly generated values. */ + for (i = 0; i < ARRAY_SIZE(data); i++) { + temp = get_random_int(); + min_heap_pop_push(&heap, &temp, &funcs); + } + err += pop_verify_heap(min_heap, &heap, &funcs); + + return err; +} + +static int __init test_min_heap_init(void) +{ + int err = 0; + + err += test_heapify_all(true); + err += test_heapify_all(false); + err += test_heap_push(true); + err += test_heap_push(false); + err += test_heap_pop_push(true); + err += test_heap_pop_push(false); + if (err) { + pr_err("test failed with %d errors\n", err); + return -EINVAL; + } + pr_info("test passed\n"); + return 0; +} +module_init(test_min_heap_init); + +static void __exit test_min_heap_exit(void) +{ + /* do nothing */ +} +module_exit(test_min_heap_exit); + +MODULE_LICENSE("GPL"); |