dynamic-c-array

Header-only generic dynamic array library for C.

This library provides dynamic arrays using malloc, realloc, and macros while keeping a clean array-like interface.

Internally, metadata is stored directly before the array in memory, allowing automatic resizing and efficient access to size and capacity information.

The library works with any data type.

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Features

• Generic dynamic arrays for any data type
• Header-only implementation
• Automatic resizing using realloc
• Automatic shrinking when usage drops below 25%
• Metadata stored internally
• Simple macro-based API
• Pre-allocation support
• Contiguous memory layout

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Installation

Simply include the header file in your project:

#include "dynamic_arrays.h"

Compile normally:

gcc main.c -o app

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Example

#include "dynamic_arrays.h"

int main(void) {
    int *arr = vector_create(int);

    vector_push_back(arr, 10);
    vector_push_back(arr, 20);
    vector_push_back(arr, 30);

    vector_print(arr, "%d");

    vector_delete_element(arr, 1);

    vector_print(arr, "%d");

    vector_reuse(arr);

    vector_print(arr, "%d");

    vector_free(arr);

    return 0;
}

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API

vector_create()

Creates a dynamic array.

Default capacity

int *arr = vector_create(int);

Custom initial capacity

int *arr = vector_create(int, 100);

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vector_push_back()

Appends an element to the vector.

vector_push_back(arr, value);

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vector_delete_element()

Deletes an element by index and shifts remaining elements left.

vector_delete_element(arr, index);

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vector_print()

Prints the vector using the supplied format specifier.

vector_print(arr, "%d");

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vector_reuse()

Resets the vector size to 0 without freeing allocated memory.

vector_reuse(arr);

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vector_free()

Frees all memory associated with the vector.

vector_free(arr);

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vector_size()

Returns the current number of elements stored in the vector.

vector_size(arr);

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vector_capacity()

Returns the current allocated capacity of the vector.

vector_capacity(arr);

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Time Complexity

Operation	Complexity
vector_push_back()	Amortized O(1)
vector_delete_element()	O(n)
vector_size()	O(1)
vector_capacity()	O(1)

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Internal Design

The vector internally stores metadata before the actual array memory.

+-----------+----------------------+
| metadata  | actual array memory  |
+-----------+----------------------+
              ^
              returned pointer

The metadata stores:

• Current size
• Current capacity
• Element size

This allows the library to expose a clean array-like interface while still supporting dynamic resizing internally.

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Notes

• The vector pointer may change after vector_push_back() because of realloc
• Always use the same vector variable after operations
• Memory must be released using vector_free()
• The library is not thread-safe

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License

MIT License