Arrays: GLib Reference Manual

## Arrays Arrays — arrays of arbitrary elements which grow automatically as elements are added |

## Functions

GArray * | g_array_new ()
GArray * | g_array_new_take ()
GArray * | g_array_new_take_zero_terminated ()
gpointer | g_array_steal ()
GArray * | g_array_sized_new ()
GArray * | g_array_copy ()
GArray * | g_array_ref ()
void | g_array_unref ()
guint | g_array_get_element_size ()
#define | g_array_append_val()
GArray * | g_array_append_vals ()
#define | g_array_prepend_val()
GArray * | g_array_prepend_vals ()
#define | g_array_insert_val()
GArray * | g_array_insert_vals ()
GArray * | g_array_remove_index ()
GArray * | g_array_remove_index_fast ()
GArray * | g_array_remove_range ()
void | g_array_sort ()
void | g_array_sort_with_data ()
gboolean | g_array_binary_search ()
#define | g_array_index()
GArray * | g_array_set_size ()
void | g_array_set_clear_func ()
gchar * | g_array_free ()

## Types and Values

struct | GArray

## Includes

    #include <gmodule.h>

## Description

Arrays are similar to standard C arrays, except that they grow automatically as elements are added.

Array elements can be of any size (though all elements of one array are the same size), and the array can be automatically cleared to '0's and zero-terminated.

To create a new array use `g_array_new()`.

To add elements to an array with a cost of O(n) at worst, use `g_array_append_val()`, `g_array_append_vals()`, `g_array_prepend_val()`, `g_array_prepend_vals()`, `g_array_insert_val()` and `g_array_insert_vals()`.

To access an element of an array in O(1) (to read it or to write it), use `g_array_index()`.

To set the size of an array, use `g_array_set_size()`.

To free an array, use `g_array_unref()` or `g_array_free()`.

All the sort functions are internally calling a quick-sort (or similar) function with an average cost of O(n log(n)) and a worst case cost of O(n^2).

Here is an example that stores integers in a GArray:

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    GArray *garray;
    gint i;
    // We create a new array to store gint values.
    // We don't want it zero-terminated or cleared to 0's.
    garray = g_array_new (FALSE, FALSE, sizeof (gint));
    for (i = 0; i < 10000; i++)
      g_array_append_val (garray, i);
    for (i = 0; i < 10000; i++)
      if (g_array_index (garray, gint, i) != i)
        g_print ("ERROR: got %d instead of %d\n",
                 g_array_index (garray, gint, i), i);
    g_array_free (garray, TRUE);

## Functions

### g_array_new ()

    GArray *
    g_array_new (gboolean zero_terminated,
                 gboolean clear_,
                 guint element_size);

Creates a new GArray with a reference count of 1.

#### Parameters

zero_terminated | `TRUE` if the array should have an extra element at the end which is set to 0 |
clear_ | `TRUE` if GArray elements should be automatically cleared to 0 when they are allocated |
element_size | the size of each element in bytes |

#### Returns

the new GArray

### g_array_new_take ()

    GArray *
    g_array_new_take (gpointer data,
                      gsize len,
                      gboolean clear,
                      gsize element_size);

Creates a new GArray with `data` as array data, `len` as length and a reference count of 1.

This avoids having to copy the data manually, when it can just be inherited. After this call, `data` belongs to the GArray and may no longer be modified by the caller. The memory of `data` has to be dynamically allocated and will eventually be freed with `g_free()`.

In case the elements need to be cleared when the array is freed, use `g_array_set_clear_func()` to set a GDestroyNotify function to perform such task.

Do not use it if `len` or `element_size` are greater than `G_MAXUINT`. GArray stores the length of its data in guint, which may be shorter than gsize.

[skip]

#### Parameters

data | an array of elements of `element_size` , or `NULL` for an empty array. | [array length=len][transfer full][nullable]
len | the number of elements in `data` |
clear | `TRUE` if GArray elements should be automatically cleared to 0 when they are allocated |
element_size | the size of each element in bytes |

#### Returns

A new GArray.

[transfer full]

Since: 2.76

### g_array_new_take_zero_terminated ()

    GArray *
    g_array_new_take_zero_terminated (gpointer data,
                                      gboolean clear,
                                      gsize element_size);

Creates a new GArray with `data` as array data, computing the length of it and setting the reference count to 1.

This avoids having to copy the data manually, when it can just be inherited. After this call, `data` belongs to the GArray and may no longer be modified by the caller. The memory of `data` has to be dynamically allocated and will eventually be freed with `g_free()`.

The length is calculated by iterating through `data` until the first `NULL` element is found.

In case the elements need to be cleared when the array is freed, use `g_array_set_clear_func()` to set a GDestroyNotify function to perform such task.

Do not use it if `data` length or `element_size` are greater than `G_MAXUINT`. GArray stores the length of its data in guint, which may be shorter than gsize.

[skip]

#### Parameters

data | an array of elements of `element_size` . | [array zero-terminated=1]
clear | `TRUE` if GArray elements should be automatically cleared to 0 when they are allocated |
element_size | the size of each element in bytes |

#### Returns

A new GArray.

[transfer full]

Since: 2.76

### g_array_steal ()

    gpointer
    g_array_steal (GArray *array,
                   gsize *len);

Frees the data in the array and resets the size to zero, while the underlying array is preserved for use elsewhere and returned to the caller.

If the array was created with the `zero_terminate` property set to `TRUE`, the returned data is zero terminated too.

If array elements contain dynamically-allocated memory, the array elements should also be freed by the caller.

A short example of use:

    1
    2
    3
    4
    5
    ...
    gpointer data;
    gsize data_len;
    data = g_array_steal (some_array, &data_len);
    ...

#### Parameters

array | a GArray. |
len | pointer to retrieve the number of elements of the original array. | [optional][out]

#### Returns

the element data, which should be freed using `g_free()`.

[transfer full]

Since: 2.64

### g_array_sized_new ()

    GArray *
    g_array_sized_new (gboolean zero_terminated,
                       gboolean clear_,
                       guint element_size,
                       guint reserved_size);

Creates a new GArray with `reserved_size` elements preallocated and a reference count of 1. This avoids frequent reallocation, if you are going to add many elements to the array. Note however that the size of the array is still 0.

#### Parameters

zero_terminated | `TRUE` if the array should have an extra element at the end with all bits cleared |
clear_ | `TRUE` if all bits in the array should be cleared to 0 on allocation |
element_size | size of each element in the array |
reserved_size | number of elements preallocated |

#### Returns

the new GArray

### g_array_copy ()

    GArray *
    g_array_copy (GArray *array);

Create a shallow copy of a GArray. If the array elements consist of pointers to data, the pointers are copied but the actual data is not.

#### Parameters

array | A GArray. |

#### Returns

A copy of `array` .

[transfer container]

Since: 2.62

### g_array_ref ()

    GArray *
    g_array_ref (GArray *array);

Atomically increments the reference count of `array` by one. This function is thread-safe and may be called from any thread.

#### Parameters

array | A GArray |

#### Returns

The passed in GArray

Since: 2.22

### g_array_unref ()

    void
    g_array_unref (GArray *array);

Atomically decrements the reference count of `array` by one. If the reference count drops to 0, all memory allocated by the array is released. This function is thread-safe and may be called from any thread.

#### Parameters

array | A GArray |

Since: 2.22

### g_array_get_element_size ()

    guint
    g_array_get_element_size (GArray *array);

Gets the size of the elements in `array` .

#### Parameters

array | A GArray |

#### Returns

Size of each element, in bytes

Since: 2.22

### g_array_append_val()

    #define             g_array_append_val(a,v)

Adds the value on to the end of the array. The array will grow in size automatically if necessary.

g_array_append_val() is a macro which uses a reference to the value parameter `v` . This means that you cannot use it with literal values such as "27". You must use variables.

#### Parameters

a | a GArray |
v | the value to append to the GArray |

#### Returns

the GArray

### g_array_append_vals ()

    GArray *
    g_array_append_vals (GArray *array,
                         gconstpointer data,
                         guint len);

Adds `len` elements onto the end of the array.

#### Parameters

array | a GArray |
data | a pointer to the elements to append to the end of the array. | [not nullable]
len | the number of elements to append |

#### Returns

the GArray

### g_array_prepend_val()

    #define             g_array_prepend_val(a,v)

Adds the value on to the start of the array. The array will grow in size automatically if necessary.

This operation is slower than `g_array_append_val()` since the existing elements in the array have to be moved to make space for the new element.

g_array_prepend_val() is a macro which uses a reference to the value parameter `v` . This means that you cannot use it with literal values such as "27". You must use variables.

#### Parameters

a | a GArray |
v | the value to prepend to the GArray |

#### Returns

the GArray

### g_array_prepend_vals ()

    GArray *
    g_array_prepend_vals (GArray *array,
                          gconstpointer data,
                          guint len);

Adds `len` elements onto the start of the array.

`data` may be `NULL` if (and only if) `len` is zero. If `len` is zero, this function is a no-op.

This operation is slower than `g_array_append_vals()` since the existing elements in the array have to be moved to make space for the new elements.

#### Parameters

array | a GArray |
data | a pointer to the elements to prepend to the start of the array. | [nullable]
len | the number of elements to prepend, which may be zero |

#### Returns

the GArray

### g_array_insert_val()

    #define             g_array_insert_val(a,i,v)

Inserts an element into an array at the given index.

g_array_insert_val() is a macro which uses a reference to the value parameter `v` . This means that you cannot use it with literal values such as "27". You must use variables.

#### Parameters

a | a GArray |
i | the index to place the element at |
v | the value to insert into the array |

#### Returns

the GArray

### g_array_insert_vals ()

    GArray *
    g_array_insert_vals (GArray *array,
                         guint index_,
                         gconstpointer data,
                         guint len);

Inserts `len` elements into a GArray at the given index.

If `index_` is greater than the array’s current length, the array is expanded. The elements between the old end of the array and the newly inserted elements will be initialised to zero if the array was configured to clear elements; otherwise their values will be undefined.

If `index_` is less than the array’s current length, new entries will be inserted into the array, and the existing entries above `index_` will be moved upwards.

`data` may be `NULL` if (and only if) `len` is zero. If `len` is zero, this function is a no-op.

#### Parameters

array | a GArray |
index_ | the index to place the elements at |
data | a pointer to the elements to insert. | [nullable]
len | the number of elements to insert |

#### Returns

the GArray

### g_array_remove_index ()

    GArray *
    g_array_remove_index (GArray *array,
                          guint index_);

Removes the element at the given index from a GArray. The following elements are moved down one place.

#### Parameters

array | a GArray |
index_ | the index of the element to remove |

#### Returns

the GArray

### g_array_remove_index_fast ()

    GArray *
    g_array_remove_index_fast (GArray *array,
                               guint index_);

Removes the element at the given index from a GArray. The last element in the array is used to fill in the space, so this function does not preserve the order of the GArray. But it is faster than `g_array_remove_index()`.

#### Parameters

array | a `GArray` |
index_ | the index of the element to remove |

#### Returns

the GArray

### g_array_remove_range ()

    GArray *
    g_array_remove_range (GArray *array,
                          guint index_,
                          guint length);

Removes the given number of elements starting at the given index from a GArray. The following elements are moved to close the gap.

#### Parameters

array | a `GArray` |
index_ | the index of the first element to remove |
length | the number of elements to remove |

#### Returns

the GArray

Since: 2.4

### g_array_sort ()

    void
    g_array_sort (GArray *array,
                  GCompareFunc compare_func);

Sorts a GArray using `compare_func` which should be a `qsort()`-style comparison function (returns less than zero for first arg is less than second arg, zero for equal, greater zero if first arg is greater than second arg).

This is guaranteed to be a stable sort since version 2.32.

#### Parameters

array | a GArray |
compare_func | comparison function |

### g_array_sort_with_data ()

    void
    g_array_sort_with_data (GArray *array,
                            GCompareDataFunc compare_func,
                            gpointer user_data);

Like `g_array_sort()`, but the comparison function receives an extra user data argument.

This is guaranteed to be a stable sort since version 2.32.

There used to be a comment here about making the sort stable by using the addresses of the elements in the comparison function. This did not actually work, so any such code should be removed.

#### Parameters

array | a GArray |
compare_func | comparison function |
user_data | data to pass to `compare_func` |

### g_array_binary_search ()

    gboolean
    g_array_binary_search (GArray *array,
                           gconstpointer target,
                           GCompareFunc compare_func,
                           guint *out_match_index);

Checks whether `target` exists in `array` by performing a binary search based on the given comparison function `compare_func` which get pointers to items as arguments. If the element is found, `TRUE` is returned and the element’s index is returned in `out_match_index` (if non-`NULL`). Otherwise, `FALSE` is returned and `out_match_index` is undefined. If `target` exists multiple times in `array` , the index of the first instance is returned. This search is using a binary search, so the `array` must absolutely be sorted to return a correct result (if not, the function may produce false-negative).

This example defines a comparison function and search an element in a GArray:

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    static gint
    cmpint (gconstpointer a, gconstpointer b)
    {
      const gint *_a = a;
      const gint *_b = b;

      return *_a - *_b;
    }
    ...
    gint i = 424242;
    guint matched_index;
    gboolean result = g_array_binary_search (garray, &i, cmpint, &matched_index);
    ...

#### Parameters

array | a GArray. |
target | a pointer to the item to look up. |
compare_func | A GCompareFunc used to locate `target` . |
out_match_index | return location for the index of the element, if found. | [optional][out]

#### Returns

`TRUE` if `target` is one of the elements of `array` , `FALSE` otherwise.

Since: 2.62

### g_array_index()

    #define             g_array_index(a,t,i)

Returns the element of a GArray at the given index. The return value is cast to the given type. This is the main way to read or write an element in a GArray.

Writing an element is typically done by reference, as in the following example. This example gets a pointer to an element in a GArray, and then writes to a field in it:

    1
    2
    3
    4
    5
    EDayViewEvent *event;
    // This gets a pointer to the 4th element in the array of
    // EDayViewEvent structs.
    event = &g_array_index (events, EDayViewEvent, 3);
    event->start_time = g_get_current_time ();

This example reads from and writes to an array of integers:

    1
    2
    3
    4
    5
    6
    7
    g_autoptr(GArray) int_array = g_array_new (FALSE, FALSE, sizeof (guint));
    for (guint i = 0; i < 10; i++)
      g_array_append_val (int_array, i);

    guint *my_int = &g_array_index (int_array, guint, 1);
    g_print ("Int at index 1 is %u; decrementing it\n", *my_int);
    *my_int = *my_int - 1;

#### Parameters

a | a GArray |
t | the type of the elements |
i | the index of the element to return |

#### Returns

the element of the GArray at the index given by `i`

### g_array_set_size ()

    GArray *
    g_array_set_size (GArray *array,
                      guint length);

Sets the size of the array, expanding it if necessary. If the array was created with `clear_` set to `TRUE`, the new elements are set to 0.

#### Parameters

array | a GArray |
length | the new size of the GArray |

#### Returns

the GArray

### g_array_set_clear_func ()

    void
    g_array_set_clear_func (GArray *array,
                            GDestroyNotify clear_func);

Sets a function to clear an element of `array` .

The `clear_func` will be called when an element in the array data segment is removed and when the array is freed and data segment is deallocated as well. `clear_func` will be passed a pointer to the element to clear, rather than the element itself.

Note that in contrast with other uses of GDestroyNotify functions, `clear_func` is expected to clear the contents of the array element it is given, but not free the element itself.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    typedef struct
    {
      gchar *str;
      GObject *obj;
    } ArrayElement;

    static void
    array_element_clear (ArrayElement *element)
    {
      g_clear_pointer (&element->str, g_free);
      g_clear_object (&element->obj);
    }

    // main code
    GArray *garray = g_array_new (FALSE, FALSE, sizeof (ArrayElement));
    g_array_set_clear_func (garray, (GDestroyNotify) array_element_clear);
    // assign data to the structure
    g_array_free (garray, TRUE);

#### Parameters

array | A GArray |
clear_func | a function to clear an element of `array` |

Since: 2.32

### g_array_free ()

    gchar *
    g_array_free (GArray *array,
                  gboolean free_segment);

Frees the memory allocated for the GArray. If `free_segment` is `TRUE` it frees the memory block holding the elements as well. Pass `FALSE` if you want to free the GArray wrapper but preserve the underlying array for use elsewhere. If the reference count of `array` is greater than one, the GArray wrapper is preserved but the size of `array` will be set to zero.

If array contents point to dynamically-allocated memory, they should be freed separately if `free_seg` is `TRUE` and no `clear_func` function has been set for `array` .

This function is not thread-safe. If using a GArray from multiple threads, use only the atomic `g_array_ref()` and `g_array_unref()` functions.

#### Parameters

array | a GArray |
free_segment | if `TRUE` the actual element data is freed as well |

#### Returns

the element data if `free_segment` is `FALSE`, otherwise `NULL`. The element data should be freed using `g_free()`.

## Types and Values

### struct GArray

    struct GArray {
      gchar *data;
      guint len;
    };

Contains the public fields of a GArray.

#### Members

gchar *`data`; | a pointer to the element data. The data may be moved as elements are added to the GArray. |
guint `len`; | the number of elements in the GArray not including the possible terminating zero element. |