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GLib.Bytes

record (struct)

A simple reference counted data type representing an immutable sequence of zero or more bytes from an unspecified origin.

The purpose of a GBytes is to keep the memory region that it holds alive for as long as anyone holds a reference to the bytes. When the last reference count is dropped, the memory is released. Multiple unrelated callers can use byte data in the GBytes without coordinating their activities, resting assured that the byte data will not change or move while they hold a reference.

A GBytes can come from many different origins that may have different procedures for freeing the memory region. Examples are memory from malloc, from memory slices, from a MappedFile or memory from other allocators.

GBytes work well as keys in HashTable. Use Bytes.equal and Bytes.hash as parameters to HashTable.new or HashTable.new_full. GBytes can also be used as keys in a Tree by passing the Bytes.compare function to Tree.new.

The data pointed to by this bytes must not be modified. For a mutable array of bytes see ByteArray. Use Bytes.unref_to_array to create a mutable array for a GBytes sequence. To create an immutable GBytes from a mutable ByteArray, use the ByteArray.free_to_bytes function.

Constructors

new

@classmethod
def new(cls, data: list[int] | None = ...) -> Bytes

Creates a new Bytes from data.

data is copied. If size is 0, data may be NULL.

As an optimization, Bytes.new may avoid an extra allocation by copying the data within the resulting bytes structure if sufficiently small (since GLib 2.84).

Parameters:

  • data — the data to be used for the bytes

new_from_bytes

@classmethod
def new_from_bytes(cls, bytes: Bytes, offset: int, length: int) -> Bytes

Creates a Bytes which is a subsection of another GBytes.

The offset + length may not be longer than the size of bytes.

A reference to bytes will be held by the newly created GBytes until the byte data is no longer needed.

Since 2.56, if offset is 0 and length matches the size of bytes, then bytes will be returned with the reference count incremented by 1. If bytes is a slice of another GBytes, then the resulting GBytes will reference the same GBytes instead of bytes. This allows consumers to simplify the usage of GBytes when asynchronously writing to streams.

Parameters:

  • bytes — a Bytes
  • offset — offset which subsection starts at
  • length — length of subsection

new_take

@classmethod
def new_take(cls, data: list[int] | None = ...) -> Bytes

Creates a new Bytes from data.

After this call, data belongs to the GBytes and may no longer be modified by the caller. The memory of data has to be dynamically allocated and will eventually be freed with free.

For creating GBytes with memory from other allocators, see Bytes.new_with_free_func.

data may be NULL if size is 0.

Parameters:

  • data — the data to be used for the bytes

Methods

compare

def compare(self, bytes2: Bytes) -> int

Compares the two Bytes values.

This function can be used to sort GBytes instances in lexicographical order.

If bytes1 and bytes2 have different length but the shorter one is a prefix of the longer one then the shorter one is considered to be less than the longer one. Otherwise the first byte where both differ is used for comparison. If bytes1 has a smaller value at that position it is considered less, otherwise greater than bytes2.

Parameters:

  • bytes2 — a pointer to a Bytes to compare with bytes1

equal

def equal(self, bytes2: Bytes) -> bool

Compares the two Bytes values being pointed to and returns TRUE if they are equal.

This function can be passed to HashTable.new as the key_equal_func parameter, when using non-NULL GBytes pointers as keys in a HashTable.

Parameters:

  • bytes2 — a pointer to a Bytes to compare with bytes1

get_data

def get_data(self) -> list[int] | None

Get the byte data in the Bytes.

This data should not be modified.

This function will always return the same pointer for a given GBytes.

NULL may be returned if size is 0. This is not guaranteed, as the GBytes may represent an empty string with data non-NULL and size as 0. NULL will not be returned if size is non-zero.

get_region

def get_region(self, element_size: int, offset: int, n_elements: int) -> int | None

Gets a pointer to a region in bytes.

The region starts at offset many bytes from the start of the data and contains n_elements many elements of element_size size.

n_elements may be zero, but element_size must always be non-zero. Ideally, element_size is a static constant (eg: sizeof a struct).

This function does careful bounds checking (including checking for arithmetic overflows) and returns a non-NULL pointer if the specified region lies entirely within the bytes. If the region is in some way out of range, or if an overflow has occurred, then NULL is returned.

Note: it is possible to have a valid zero-size region. In this case, the returned pointer will be equal to the base pointer of the data of bytes, plus offset. This will be non-NULL except for the case where bytes itself was a zero-sized region. Since it is unlikely that you will be using this function to check for a zero-sized region in a zero-sized bytes, NULL effectively always means ‘error’.

Parameters:

  • element_size — a non-zero element size
  • offset — an offset to the start of the region within the bytes
  • n_elements — the number of elements in the region

get_size

def get_size(self) -> int

Get the size of the byte data in the Bytes.

This function will always return the same value for a given GBytes.

hash

def hash(self) -> int

Creates an integer hash code for the byte data in the Bytes.

This function can be passed to HashTable.new as the key_hash_func parameter, when using non-NULL GBytes pointers as keys in a HashTable.

ref

def ref(self) -> Bytes

Increase the reference count on bytes.

unref

def unref(self) -> None

Releases a reference on bytes.

This may result in the bytes being freed. If bytes is NULL, it will return immediately.

unref_to_array

def unref_to_array(self) -> list[int]

Unreferences the bytes, and returns a new mutable ByteArray containing the same byte data.

As an optimization, the byte data is transferred to the array without copying if this was the last reference to bytes and bytes was created with Bytes.new, Bytes.new_take or ByteArray.free_to_bytes and the buffer was larger than the size Bytes may internalize within its allocation. In all other cases the data is copied.

Do not use it if bytes contains more than G_MAXUINT bytes. ByteArray stores the length of its data in guint, which may be shorter than gsize, that bytes is using.

unref_to_data

def unref_to_data(self) -> list[int]

Unreferences the bytes, and returns a pointer the same byte data contents.

As an optimization, the byte data is returned without copying if this was the last reference to bytes and bytes was created with Bytes.new, Bytes.new_take or ByteArray.free_to_bytes and the buffer was larger than the size Bytes may internalize within its allocation. In all other cases the data is copied.