Buffers

Buffers — Common buffer functions, including data upload APIs

Stability Level

Unstable, unless otherwise indicated

Functions

Types and Values

Description

The CoglBuffer API provides a common interface to manipulate buffers that have been allocated either via cogl_pixel_buffer_new() or cogl_attribute_buffer_new(). The API allows you to upload data to these buffers and define usage hints that help Cogl manage your buffer optimally.

Data can either be uploaded by supplying a pointer and size so Cogl can copy your data, or you can mmap() a CoglBuffer and then you can copy data to the buffer directly.

One of the most common uses for CoglBuffers is to upload texture data asynchronously since the ability to mmap the buffers into the CPU makes it possible for another thread to handle the IO of loading an image file and unpacking it into the mapped buffer without blocking other Cogl operations.

Functions

cogl_is_buffer ()

CoglBool
cogl_is_buffer (void *object);

Checks whether buffer is a buffer object.

Parameters

object

a buffer object

 

Returns

TRUE if the handle is a CoglBuffer, and FALSE otherwise

Since: 1.2

Stability Level: Unstable


cogl_buffer_get_size ()

unsigned int
cogl_buffer_get_size (CoglBuffer *buffer);

Retrieves the size of buffer

Parameters

buffer

a buffer object

 

Returns

the size of the buffer in bytes

Since: 1.2

Stability Level: Unstable


cogl_buffer_set_update_hint ()

void
cogl_buffer_set_update_hint (CoglBuffer *buffer,
                             CoglBufferUpdateHint hint);

Sets the update hint on a buffer. See CoglBufferUpdateHint for a description of the available hints.

Parameters

buffer

a buffer object

 

hint

the new hint

 

Since: 1.2

Stability Level: Unstable


cogl_buffer_get_update_hint ()

CoglBufferUpdateHint
cogl_buffer_get_update_hint (CoglBuffer *buffer);

Retrieves the update hints set using cogl_buffer_set_update_hint()

Parameters

buffer

a buffer object

 

Returns

the CoglBufferUpdateHint currently used by the buffer

Since: 1.2

Stability Level: Unstable


cogl_buffer_map ()

void *
cogl_buffer_map (CoglBuffer *buffer,
                 CoglBufferAccess access,
                 CoglBufferMapHint hints);

Maps the buffer into the application address space for direct access. This is equivalent to calling cogl_buffer_map_range() with zero as the offset and the size of the entire buffer as the size.

It is strongly recommended that you pass COGL_BUFFER_MAP_HINT_DISCARD as a hint if you are going to replace all the buffer's data. This way if the buffer is currently being used by the GPU then the driver won't have to stall the CPU and wait for the hardware to finish because it can instead allocate a new buffer to map.

The behaviour is undefined if you access the buffer in a way conflicting with the access mask you pass. It is also an error to release your last reference while the buffer is mapped.

Parameters

buffer

a buffer object

 

access

how the mapped buffer will be used by the application

 

hints

A mask of CoglBufferMapHints that tell Cogl how the data will be modified once mapped.

 

Returns

A pointer to the mapped memory or NULL is the call fails.

[transfer none]

Since: 1.2

Stability Level: Unstable


cogl_buffer_unmap ()

void
cogl_buffer_unmap (CoglBuffer *buffer);

Unmaps a buffer previously mapped by cogl_buffer_map().

Parameters

buffer

a buffer object

 

Since: 1.2

Stability Level: Unstable


cogl_buffer_set_data ()

CoglBool
cogl_buffer_set_data (CoglBuffer *buffer,
                      size_t offset,
                      const void *data,
                      size_t size);

Updates part of the buffer with new data from data . Where to put this new data is controlled by offset and offset + data should be less than the buffer size.

Parameters

buffer

a buffer object

 

offset

destination offset (in bytes) in the buffer

 

data

a pointer to the data to be copied into the buffer

 

size

number of bytes to copy

 

Returns

TRUE is the operation succeeded, FALSE otherwise

Since: 1.2

Stability Level: Unstable


cogl_pixel_buffer_new ()

CoglPixelBuffer *
cogl_pixel_buffer_new (CoglContext *context,
                       size_t size,
                       const void *data);

Declares a new CoglPixelBuffer of size bytes to contain arrays of pixels. Once declared, data can be set using cogl_buffer_set_data() or by mapping it into the application's address space using cogl_buffer_map().

If data isn't NULL then size bytes will be read from data and immediately copied into the new buffer.

Parameters

context

A CoglContext

 

size

The number of bytes to allocate for the pixel data.

 

data

An optional pointer to vertex data to upload immediately

 

Returns

a newly allocated CoglPixelBuffer.

[transfer full]

Since: 1.10

Stability Level: Unstable


cogl_is_pixel_buffer ()

CoglBool
cogl_is_pixel_buffer (void *object);

Checks whether object is a pixel buffer.

Parameters

object

a CoglObject to test

 

Returns

TRUE if the object is a pixel buffer, and FALSE otherwise

Since: 1.2

Stability Level: Unstable

Types and Values

enum CoglBufferUpdateHint

The update hint on a buffer allows the user to give some detail on how often the buffer data is going to be updated.

Members

COGL_BUFFER_UPDATE_HINT_STATIC

the buffer will not change over time

 

COGL_BUFFER_UPDATE_HINT_DYNAMIC

the buffer will change from time to time

 

COGL_BUFFER_UPDATE_HINT_STREAM

the buffer will be used once or a couple of times

 

Since: 1.2

Stability Level: Unstable


enum CoglBufferAccess

The access hints for cogl_buffer_set_update_hint()

Members

COGL_BUFFER_ACCESS_READ

the buffer will be read

 

COGL_BUFFER_ACCESS_WRITE

the buffer will written to

 

COGL_BUFFER_ACCESS_READ_WRITE

the buffer will be used for both reading and writing

 

Since: 1.2

Stability Level: Unstable