Vec.h | A single header-only dynamic vector C library.

Vec.h is a small, header-only C library for creating dynamic arrays (vectors) with minimal boilerplate.

It allows you to create vectors for any type, including signed or unsigned integers, floating point numbers, strings or even complete structs!

Maps/Dictionaries

Vec.h also provides a simple map implementation built on top of vectors. It keeps keys and values in sync.

Map value deletion is O(1) but does not preserve insertion order.

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Features

• Type-safe vectors for any C type
• Dynamic growing and manual shrinking
• Append, insert, delete, and access elements safely
• Lightweight and header only

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Installation

Just download vec.h into your project and include it:

#include "vec.h"

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Vector Usage

1. Define a vector type

NEW_VEC_TYPE(int, IntVec, 16); // Defines a vector of ints named IntVec
NEW_VEC_TYPE(float, FloatVec, 16); // Defines a vector of floats
NEW_VEC_TYPE(char*, StringVec, 8); // Defines a vector of strings (char*) (needs to individually free each element before freeing the entire vector)
NEW_VEC_TYPE(TYPE, NAME, MIN_CAP); // Defines a vector of TYPE named NAME with minimum capacity MIN_CAP

The first parameter is the element type, the second is the vector name.

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2. Initialize a vector

IntVec ivec;
vec_init_IntVec(&ivec); // Initializes the vector

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3. Push elements

vec_append_IntVec(&ivec, 42);
vec_append_IntVec(&ivec, 100);

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4. Insert elements

vec_insert_IntVec(&ivec, 1, 55); // Inserts 55 at index 1

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5. Access elements

int value = vec_at_IntVec(&ivec, 0);    // Returns the element at index 0
int first = vec_front_IntVec(&ivec);    // Returns the first element
int last = vec_back_IntVec(&ivec);      // Returns the last element

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6. Delete elements

vec_delete_IntVec(&ivec, 0); // Deletes the element at index 0 (preserves order)
vec_udelete_IntVec(&ivec, 1); // Deletes the element at index 1 (O(1), unordered)

Note: vec_udelete swaps the last element into the deleted element's position (unordered).

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7. Search elements

ssize_t index = vec_find_IntVec(&ivec, 100);   // Returns index of first occurrence or -1 if not found
unsigned int exists = vec_contains_IntVec(&ivec, 42); // Returns 1 if element exists, 0 otherwise

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8. Query size and capacity

size_t sz = vec_size_IntVec(&ivec);       // Number of elements
size_t cap = vec_capacity_IntVec(&ivec);  // Current allocated capacity
size_t min_cap = vec_minimum_capacity_IntVec(&ivec);  // Minimum allowed allocated capacity

Note: these just return &ivec->size, &ivec->capacity and &ivec->min_cap respectively.

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9. Shrink the vector

vec_shrink_IntVec(&ivec); // Shrinks capacity if much larger than count

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10. Free the vector

vec_free_IntVec(&ivec);

Note: For pointer types (like char*), free individual elements first before freeing the vector.

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Map Usage

1. Define a map type

NEW_MAP_TYPE(int, int, IntIntMap, 16); // Defines a map of int:int named IntIntMap (example map)
NEW_MAP_TYPE(KTYPE, VTYPE, NAME, MIN_CAP); // Defines a map of KTYPE:VTYPE named NAME

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2. Initialize a map

IntIntMap iimap;
map_init_IntIntMap(&iimap);

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3. Set a key to a value

map_set_IntIntMap(&iimap, 1, 100);
map_set_IntIntMap(&iimap, 2, 200);

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4. Get a value from a key

map_get_IntIntMap(&iimap, 1); // 100

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5. Delete an entry with a key

map_del_IntIntMap(&iimap, 2); // Removes key 2, and value 200

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6. Free the map

map_free_IntIntMap(&iimap);

Note: if either the key or/and the value is a pointer type (like char*), you'll need to free those elements individually first.

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License

MIT License, free to use, modify, and re-distribute with or without modification.