如何编写输出信号大小可变的 S-Function？

Question

我想写一个块，它从选定的目录发送所有图像文件。

图像大小不同，因此输出信号大小应该不同。

很遗憾，我无法找到在每一步更改信号大小的方法。这里有许多未记录的功能，例如

block.OutputPort(1).DimensionsMode = 'Variable';

和

block.OutputPort(1).CurrentDimensions = [1 block.InputPort(1).Data];

等等。我还无法推断出正确的方法来操作所有这些东西......

更新

比如这个 S-function

function Test_SF_01(block)
% Level-2 MATLAB file S-Function.

    setup(block);

function setup(block)

    % Register number of ports and parameters
    block.NumInputPorts  = 0;
    block.NumOutputPorts = 1;
    block.NumDialogPrms  = 0;

    % Setup functional port properties to dynamically inherited
    block.SetPreCompOutPortInfoToDynamic;

    % Register the properties of the output port
    block.OutputPort(1).DimensionsMode = 'Variable';
    block.OutputPort(1).SamplingMode   = 'Sample';

    % Register sample times
    %  [-1, 0] : Inherited sample time
    block.SampleTimes = [-1 0];

    % Register methods called at run-time
    block.RegBlockMethod('Outputs', @Outputs);

function Outputs(block)
    block.OutputPort(1).CurrentDimensions =  floor(rand(1,2)*10)+1;

导致错误

输出端口 1 的变量尺寸分配无效 'Test_01/Level-2 MATLAB S-Function'。可变维数 是 1。但是，MATLAB 数组的长度是 2

为什么？

Answer 1

以下 S-Function 生成可变维度信号。他们的关键问题是Dimensions 属性的初始集定义了维度的最大值，这在文档中绝对不清楚，而错误消息大多无关紧要。

function Test_SF_01(block)
% Level-2 MATLAB file S-Function.

    setup(block);

function setup(block)

    % Register number of ports and parameters
    block.NumInputPorts  = 0;
    block.NumOutputPorts = 1;
    block.NumDialogPrms  = 0;

    % Setup functional port properties to dynamically inherited
    block.SetPreCompOutPortInfoToDynamic;

    % Register the properties of the output port
    block.OutputPort(1).DimensionsMode = 'Variable';
    block.OutputPort(1).Dimensions = [10000 10000];

    block.OutputPort(1).SamplingMode   = 'Sample';

    % Register sample times
    %  [-1, 0] : Inherited sample time
    block.SampleTimes = [-1 0];

    % Register methods called at run-time
    block.RegBlockMethod('Outputs', @Outputs);

function Outputs(block)

     dims = floor(rand(1,2)*10)+1;
     block.OutputPort(1).CurrentDimensions = dims;

     data = rand(dims);
    block.OutputPort(1).Data = data;

Answer 2

您是否还查看过文档中的以下代码示例？见Operations for Variable-Size Signals。那里的内容比代码中的内容要多。可能最好从基本模板 msfuntmpl_basic.m 开始，就像他们在文档中所做的那样。

function setup(block)
% Register the properties of the output port
block.OutputPort(1).DimensionsMode = 'Variable';
block.RegBlockMethod('SetInputPortDimensionsMode',  @SetInputDimsMode);

function DoPostPropSetup(block)
%Register dependency rules to update current output size of output port a depending on
%input ports b and c
block.AddOutputDimsDependencyRules(a, [b c], @setOutputVarDims);

%Configure output port b to have the same dimensions as input port a
block.InputPortSameDimsAsOutputPort(a,b);

%Configure DWork a to have its size reset when input size changes.
block.DWorkRequireResetForSignalSize(a,true);

function SetInputDimsMode(block, port, dm)
% Set dimension mode
block.InputPort(port).DimensionsMode = dm;
block.OutputPort(port).DimensionsMode = dm;

function setOutputVarDims(block, opIdx, inputIdx)
% Set current (run-time) dimensions of the output
outDimsAfterReset = block.InputPort(inputIdx(1)).CurrentDimensions;
block.OutputPort(opIdx).CurrentDimensions = outDimsAfterReset;