Memory

class Memory(*args, **kwargs)

GstMemory is a lightweight refcounted object that wraps a region of memory. They are typically used to manage the data of a Buffer.

A GstMemory object has an allocated region of memory of maxsize. The maximum size does not change during the lifetime of the memory object. The memory also has an offset and size property that specifies the valid range of memory in the allocated region.

Memory is usually created by allocators with a alloc() method call. When None is used as the allocator, the default allocator will be used.

New allocators can be registered with register(). Allocators are identified by name and can be retrieved with find(). set_default() can be used to change the default allocator.

New memory can be created with new_wrapped() that wraps the memory allocated elsewhere.

Refcounting of the memory block is performed with gst_memory_ref() and gst_memory_unref().

The size of the memory can be retrieved and changed with get_sizes() and resize() respectively.

Getting access to the data of the memory is performed with map(). The call will return a pointer to offset bytes into the region of memory. After the memory access is completed, unmap() should be called.

Memory can be copied with copy(), which will return a writable copy. share() will create a new memory block that shares the memory with an existing memory block at a custom offset and with a custom size.

Memory can be efficiently merged when is_span() returns True.

Constructors

class Memory
classmethod new_wrapped(flags: MemoryFlags, data: Sequence[int], maxsize: int, offset: int, user_data: None, notify: Callable[[...], None] | None = None) → Memory | None

Allocate a new memory block that wraps the given data.

The prefix/padding must be filled with 0 if flags contains GST_MEMORY_FLAG_ZERO_PREFIXED and GST_MEMORY_FLAG_ZERO_PADDED respectively.

Parameters:

  • flags – MemoryFlags

  • data – data to wrap

  • maxsize – allocated size of data

  • offset – offset in data

  • user_data – user_data

  • notify – called with user_data when the memory is freed

Methods

class Memory
get_sizes() → tuple[int, int, int]

Get the current size, offset and maxsize of mem.

is_span(mem2: Memory) → tuple[bool, int]

Check if mem1 and mem2 share the memory with a common parent memory object and that the memory is contiguous.

If this is the case, the memory of mem1 and mem2 can be merged efficiently by performing share() on the parent object from the returned offset.

Parameters:

mem2 – a Memory

is_type(mem_type: str) → bool

Check if mem if allocated with an allocator for mem_type.

Added in version 1.2.

Parameters:

mem_type – a memory type

make_mapped(flags: MapFlags) → tuple[Memory | None, MapInfo]

Create a Memory object that is mapped with flags. If mem is mappable with flags, this function returns the mapped mem directly. Otherwise a mapped copy of mem is returned.

This function takes ownership of old mem and returns a reference to a new Memory.

Parameters:

flags – mapping flags

map(flags: MapFlags) → tuple[bool, MapInfo]

Fill info with the pointer and sizes of the memory in mem that can be accessed according to flags.

This function can return False for various reasons:

  • the memory backed by mem is not accessible with the given flags.

  • the memory was already mapped with a different mapping.

info and its contents remain valid for as long as mem is valid and until unmap() is called.

For each map() call, a corresponding unmap() call should be done.

Parameters:

flags – mapping flags

resize(offset: int, size: int) → None

Resize the memory region. mem should be writable and offset + size should be less than the maxsize of mem.

GST_MEMORY_FLAG_ZERO_PREFIXED and GST_MEMORY_FLAG_ZERO_PADDED will be cleared when offset or padding is increased respectively.

Parameters:

  • offset – a new offset

  • size – a new size

share(offset: int, size: int) → Memory

Return a shared copy of size bytes from mem starting from offset. No memory copy is performed and the memory region is simply shared. The result is guaranteed to be non-writable. size can be set to -1 to return a shared copy from offset to the end of the memory region.

Parameters:

  • offset – offset to share from

  • size – size to share, or -1 to share to the end of the memory region

unmap(info: MapInfo) → None

Release the memory obtained with map()

Parameters:

info – a MapInfo

Fields

class Memory
align

The alignment of the memory

allocator

Pointer to the Allocator

maxsize

The maximum size allocated

mini_object

Parent structure

offset

The offset where valid data starts

parent

Parent memory block

size

The size of valid data