Enrico Fraccaroli
72 lines
2.6 KiB
C
72 lines
2.6 KiB
C
/// MentOS, The Mentoring Operating system project
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/// @file stdlib.h
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/// @brief Useful generic functions and macros.
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/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
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/// See LICENSE.md for details.
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#pragma once
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#include "stddef.h"
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/// @brief Returns the number of usable bytes in the block pointed to by ptr.
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/// @param ptr The pointer for which we want to retrieve the usable size.
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/// @return The number of usable bytes in the block of allocated memory
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/// pointed to by ptr. If ptr is not a valid pointer, 0 is returned.
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size_t malloc_usable_size(void *ptr);
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/// @brief Provides dynamically allocated memory.
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/// @param size The amount of memory to allocate.
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/// @return A pointer to the allocated memory.
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void *malloc(unsigned int size);
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/// @brief Allocates a block of memory for an array of num elements.
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/// @param num The number of elements.
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/// @param size The size of an element.
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/// @return A pointer to the allocated memory.
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void *calloc(size_t num, size_t size);
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/// @brief Reallocates the given area of memory.
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/// @param ptr The pointer to the memory to reallocate.
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/// @param size The new size for the memory.
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/// @return A pointer to the new portion of memory.
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/// @details
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/// It must be previously allocated by malloc(), calloc() or realloc() and
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/// not yet freed with a call to free or realloc. Otherwise, the results
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/// are undefined.
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void *realloc(void *ptr, size_t size);
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/// @brief Frees dynamically allocated memory.
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/// @param ptr The pointer to the allocated memory.
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void free(void *ptr);
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/// The maximum value returned by the rand function.
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#define RAND_MAX ((1U << 31U) - 1U)
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/// @brief Allows to set the seed of the random value generator.
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/// @param x The new seed.
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void srand(int x);
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/// @brief Generates a random value.
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/// @return The random value.
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int rand();
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/// @brief Cause an abnormal program termination with core-dump.
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void abort();
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/// @brief Tries to adds the variable to the environment.
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/// @param name Name of the variable.
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/// @param value Value of the variable.
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/// @param overwrite Override existing variable value or not.
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/// @return Zero on success, or -1 on error with errno indicating the cause.
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int setenv(const char *name, const char *value, int overwrite);
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/// @brief Tries to remove the variable from the environment.
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/// @param name Name of the variable.
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/// @return Zero on success, or -1 on error with errno indicating the cause.
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int unsetenv(const char *name);
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/// @brief Returns the value of the given variable.
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/// @param name Name of the variable.
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/// @return A pointer to the value, or NULL if there is no match.
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char *getenv(const char *name);
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