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/* Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
* SPDX-License-Identifier: GPL-3.0-or-later
*/
/**
*
* @file array.h
* @brief A set of simple macros to make working with dynamic arrays easier.
*
* @note The C has no generics, so it is implemented mostly using macros.
* Be aware of that, as direct usage of the macros in the evaluating macros
* may lead to different expectations:
*
* @code{.c}
* MIN(array_push(arr, val), other)
* @endcode
*
* May evaluate the code twice, leading to unexpected behaviour.
* This is a price to pay for the absence of proper generics.
*
* # Example usage:
*
* @code{.c}
* array_t(const char*) arr;
* array_init(arr);
*
* // Reserve memory in advance
* if (array_reserve(arr, 2) < 0) {
* return ENOMEM;
* }
*
* // Already reserved, cannot fail
* array_push(arr, "princess");
* array_push(arr, "leia");
*
* // Not reserved, may fail
* if (array_push(arr, "han") < 0) {
* return ENOMEM;
* }
*
* // It does not hide what it really is
* for (size_t i = 0; i < arr.len; ++i) {
* printf("%s\n", arr.at[i]);
* }
*
* // Random delete
* array_del(arr, 0);
* @endcode
* \addtogroup generics
* @{
*/
#pragma once
#include <stdlib.h>
/** Choose array length when it overflows. */
static inline size_t array_next_count(size_t elm_size, size_t want, size_t have)
{
if (want >= have * 2) // We amortized enough and maybe more won't be needed.
return want;
const size_t want_b = want * elm_size;
if (want_b < 64) // Short arrays are cheap to copy; get just one extra.
return want + 1;
if (want_b < 1024) // 50% growth amortizes to roughly 3 copies per element.
return want + want / 2;
return want * 2; // Doubling growth amortizes to roughly 2 copies per element.
}
/** @internal Incremental memory reservation */
static inline int array_std_reserve(void *baton, void **mem, size_t elm_size, size_t want, size_t *have)
{
if (*have >= want) {
return 0;
}
/* Simplified Qt containers growth strategy */
size_t next_size = array_next_count(elm_size, want, *have);
void *mem_new = realloc(*mem, next_size * elm_size);
if (mem_new != NULL) {
*mem = mem_new;
*have = next_size;
return 0;
}
return -1;
}
/** @internal Wrapper for stdlib free. */
static inline void array_std_free(void *baton, void *p)
{
free(p);
}
/** Declare an array structure. */
#define array_t(type) struct {type * at; size_t len; size_t cap; }
/** Zero-initialize the array. */
#define array_init(array) ((array).at = NULL, (array).len = (array).cap = 0)
/** Free and zero-initialize the array (plain malloc/free). */
#define array_clear(array) \
array_clear_mm(array, array_std_free, NULL)
/** Make the array empty and free pointed-to memory.
* Mempool usage: pass mm_free and a knot_mm_t* . */
#define array_clear_mm(array, free, baton) \
(free)((baton), (array).at), array_init(array)
/** Reserve capacity for at least n elements.
* @return 0 if success, <0 on failure */
#define array_reserve(array, n) \
array_reserve_mm(array, n, array_std_reserve, NULL)
/** Reserve capacity for at least n elements.
* Mempool usage: pass kr_memreserve and a knot_mm_t* .
* @return 0 if success, <0 on failure */
#define array_reserve_mm(array, n, reserve, baton) \
(reserve)((baton), (void **) &(array).at, array_member_size((array)), (n), &(array).cap)
/**
* Push value at the end of the array, resize it if necessary.
* Mempool usage: pass kr_memreserve and a knot_mm_t* .
* @note May fail if the capacity is not reserved.
* @return element index on success, <0 on failure
*/
#define array_push_mm(array, val, reserve, baton) \
(int)((array).len < (array).cap ? ((array).at[(array).len] = (val), (array).len++) \
: (array_reserve_mm(array, ((array).cap + 1), reserve, baton) < 0 ? -1 \
: ((array).at[(array).len] = (val), (array).len++)))
/**
* Push value at the end of the array, resize it if necessary (plain malloc/free).
* @note May fail if the capacity is not reserved.
* @return element index on success, <0 on failure
*/
#define array_push(array, val) \
array_push_mm(array, val, array_std_reserve, NULL)
/**
* Pop value from the end of the array.
*/
#define array_pop(array) \
(array).len -= 1
/**
* Remove value at given index.
* @return 0 on success, <0 on failure
*/
#define array_del(array, i) \
(int)((i) < (array).len ? ((array).len -= 1,(array).at[i] = (array).at[(array).len], 0) : -1)
/**
* Return last element of the array.
* @warning Undefined if the array is empty.
*/
#define array_tail(array) \
(array).at[(array).len - 1]
/**
* Return the size of a singular member in the array.
*/
#define array_member_size(array) \
(sizeof((array).at[0])) // NOLINT(bugprone-sizeof-expression): usually a false-positive
/** @} */
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