Buffer

Namespace: buffer Language: Lua Type: Defold Lua File: script_buffer.cpp Source: engine/gamesys/src/gamesys/scripts/script_buffer.cpp

Functions for manipulating buffers and streams

API

buffer.copy_buffer

Type: FUNCTION Copy all data streams from one buffer to another, element wise. Each of the source streams must have a matching stream in the destination buffer. The streams must match in both type and size. The source and destination buffer can be the same.

Parameters

• dst (buffer) - the destination buffer
• dstoffset (number) - the offset to start copying data to
• src (buffer) - the source data buffer
• srcoffset (number) - the offset to start copying data from
• count (number) - the number of elements to copy

Examples

How to copy elements (e.g. vertices) from one buffer to another

-- copy entire buffer
buffer.copy_buffer(dstbuffer, 0, srcbuffer, 0, #srcbuffer)

-- copy last 10 elements to the front of another buffer
buffer.copy_buffer(dstbuffer, 0, srcbuffer, #srcbuffer - 10, 10)

buffer.copy_stream

Type: FUNCTION Copy a specified amount of data from one stream to another. The value type and size must match between source and destination streams. The source and destination streams can be the same.

Parameters

• dst (bufferstream) - the destination stream
• dstoffset (number) - the offset to start copying data to (measured in value type)
• src (bufferstream) - the source data stream
• srcoffset (number) - the offset to start copying data from (measured in value type)
• count (number) - the number of values to copy (measured in value type)

Examples

How to update a texture of a sprite:

-- copy entire stream
local srcstream = buffer.get_stream(srcbuffer, hash("xyz"))
local dststream = buffer.get_stream(dstbuffer, hash("xyz"))
buffer.copy_stream(dststream, 0, srcstream, 0, #srcstream)

buffer.create

Type: FUNCTION Create a new data buffer containing a specified set of streams. A data buffer can contain one or more streams with typed data. This is useful for managing compound data, for instance a vertex buffer could contain separate streams for vertex position, color, normal etc.

Parameters

• element_count (number) - The number of elements the buffer should hold
• declaration (table) - A table where each entry (table) describes a stream

• hash | string name: The name of the stream
• constant type: The data type of the stream
• number count: The number of values each element should hold

Returns

• buffer (buffer) - the new buffer

Examples

How to create and initialize a buffer

function init(self)
  local size = 128
  self.image = buffer.create( size * size, { {name=hash("rgb"), type=buffer.VALUE_TYPE_UINT8, count=3 } })
  self.imagestream = buffer.get_stream(self.image, hash("rgb"))

  for y=0,self.height-1 do
     for x=0,self.width-1 do
         local index = y * self.width * 3 + x * 3 + 1
         self.imagestream[index + 0] = self.r
         self.imagestream[index + 1] = self.g
         self.imagestream[index + 2] = self.b
     end
  end

buffer.get_bytes

Type: FUNCTION Get a copy of all the bytes from a specified stream as a Lua string.

Parameters

• buffer (buffer) - the source buffer
• stream_name (hash) - the name of the stream

Returns

• data (string) - the buffer data as a Lua string

buffer.get_metadata

Type: FUNCTION Get a named metadata entry from a buffer along with its type.

Parameters

• buf (buffer) - the buffer to get the metadata from

• metadata_name (hash

  string) - name of the metadata entry

Returns

• values (table

  nil) - table of metadata values or nil if the entry does not exist

• value_type (constant

  nil) - numeric type of values or nil

Examples

How to get a metadata entry from a buffer

-- retrieve a metadata entry named "somefloats" and its nomeric type
local values, type = buffer.get_metadata(buf, hash("somefloats"))
if metadata then print(#metadata.." values in 'somefloats'") end

buffer.get_stream

Type: FUNCTION Get a specified stream from a buffer.

Parameters

• buffer (buffer) - the buffer to get the stream from

• stream_name (hash

  string) - the stream name

Returns

• stream (bufferstream) - the data stream

buffer.set_metadata

Type: FUNCTION Creates or updates a metadata array entry on a buffer. The value type and count given when updating the entry should match those used when first creating it.

Parameters

• buf (buffer) - the buffer to set the metadata on

• metadata_name (hash

  string) - name of the metadata entry

• values (table) - actual metadata, an array of numeric values
• value_type (constant) - type of values when stored

Examples

How to set a metadata entry on a buffer

-- create a new metadata entry with three floats
buffer.set_metadata(buf, hash("somefloats"), {1.5, 3.2, 7.9}, buffer.VALUE_TYPE_FLOAT32)
-- ...
-- update to a new set of values
buffer.set_metadata(buf, hash("somefloats"), {-2.5, 10.0, 32.2}, buffer.VALUE_TYPE_FLOAT32)

buffer.VALUE_TYPE_FLOAT32

Type: CONSTANT Float, single precision, 4 bytes

buffer.VALUE_TYPE_INT16

Type: CONSTANT Signed integer, 2 bytes

buffer.VALUE_TYPE_INT32

Type: CONSTANT Signed integer, 4 bytes

buffer.VALUE_TYPE_INT64

Type: CONSTANT Signed integer, 8 bytes

buffer.VALUE_TYPE_INT8

Type: CONSTANT Signed integer, 1 byte

buffer.VALUE_TYPE_UINT16

Type: CONSTANT Unsigned integer, 2 bytes

buffer.VALUE_TYPE_UINT32

Type: CONSTANT Unsigned integer, 4 bytes

buffer.VALUE_TYPE_UINT64

Type: CONSTANT Unsigned integer, 8 bytes

buffer.VALUE_TYPE_UINT8

Type: CONSTANT Unsigned integer, 1 byte