nescc-mig man page

nescc-mig — message interface generator for nesC

Synopsis

nescc-mig [any nescc option] [tool-specific options]
[-o output-file] [-nescc=driver]
tool msg-format-file message-type

Description

nescc-mig is a tool to generate code to process nesC messages (which are specified by C types). The tool argument specifies what tool should be generated, the message-type specifies the C type of the message you wish to process and msg-format-file specifies a nesC file which uses that type. The message type must be defined with struct message-type, nx_struct message-type, union message-type, nx_union message-type.

When used with types whose layout is platform-dependent (i.e., not defined with nx_struct or nx_union), it is important to specify the correct nescc target architecture option (-fnesc-target=...). If you are invoking nescc-mig indirectly via mig, you can use the ncc -target=... option instead.

If an enum constant named AM_message_type (with message_type capitalized) is found, then the value of that constant is assumed to be the active message type for message-type. If you need access to other constants from your nesC application, please consult the nescc-ncg man page.

The current tools are java, csharp, python and C, which generate java, C#, python and C code to encode and decode messages.

Options

You can pass any nescc option, as well as

-o output-file
Specify the file in which to output the generated code.
-nescc=driver
Use driver instead of nescc to extract type layout information. For example, if you specify -nescc=ncc, you can use nescc-mig to extract type information from TinyOS applications (which are normally compiled with ncc).
tool-specific options
See below.

Java Tool

This tool generates a java class to encode or decode a nesC message, basing itself on the net.tinyos.message infrastructure. It accepts the following options:

-java-classname=full-class-name
This option is required and specifies the package and name of the generated class. If the full-class-name has no '.', then no package directive is included in the output.
-java-extends=class-name
Specify the class the generated class will extend. The default is net.tinyos.message.Message.

For each field fname of structure message-type, there are the following methods (the bit offset and size methods are useful for structures containing bitfields):

*
get_fname: get field's value
*
set_fname: set field's value
*
offsetBits_fname: return bit offset of field in message-type
*
offset_fname: return byte offset of field in message-type
*
sizeBits_fname: return size in bits of field (not for arrays)
*
size_fname: return size in bytes of field (not for arrays) (absent if fname is a bitfield)
*
isSigned_fname: return true if fname is of a signed type
*
isArray_fname: return true if fname is an array

Embedded structures in message-type are expanded, using _ to separate the structure name and its fields.

A number of extra methods are present for fields that are arrays:

*
getElement_fname: get an element of the array
*
setElement_fname: set an element of the array
*
elementSize_fname: return size in bytes of array elements
*
elementSizeBits_fname: return size in bits of array elements
*
numDimensions_fname: return number of dimensions of the array
*
numElements_fname: return number of elements of the array for a given dimension (left-most dimension is numbered 0) - the dimension is optional for 1-dimensional arrays
*
totalSize_fname: return size in bytes of the array (absent if the array is variable-size)
*
totalSizeBits_fname: return size in bits of the array (absent if the array is variable-size)

If the array is 1-dimensional and the elements are one byte, then the following methods exist:

*
getString_fname: build a Java string from the array assuming it contains a C-style null-terminated string
*
setString_fname: set the array to a C-style null-terminated string given a java string

The getElement_..., setElement_..., offset_... and offsetBits_... methods take one argument per array dimension. These methods report errors if the array index is out of bounds. If an array has a maximum size of 0, mig assumes it represents a variable-size array and does not check the corresponding array index.

The data for a message is stored in an array, with explicit base and length information. The constructors can either allocate this array, receive it as an explicit argument or extract if from another message. The base and length can also be optionally passed to these constructors.

The optional length argument overrides the default size of sizeof(message-type); this is useful for variable-size messages. The use of an explicit base is helpful for messages embedded in other messages.

The generated class also has an amType() method which returns the message's active message type, or -1 if no AM_message_type constant was found.

C# Tool

This tool generates a C# class to encode or decode a nesC message. It accepts the following options:

-csharp-classname=full-class-name
This option is required and specifies the namespace and name of the generated class. If the full-class-name has no '.', then no namespace directive is included in the output.
-csharp-extends=class-name

Specify the class the generated class will extend. The default is tinyos.message.Message.

The methods in the generated class are the same as for the Java tool.

Python Tool

This tool generates a Python class to encode or decode a nesC message. It accepts the following options:

-python-classname=full-class-name
This option is required and specifies the name of the generated class.
-python-extends=class-name

Specify the class the generated class will extend. The default is tinyos.message.Message.Message.

The methods in the generated class are the same as for the Java tool.

C Tool

This tool generates a C header file (.h) with constants describing the type's layout, and a C module (.c) with functions to get and set each field. You must pass the .h file's name to nescc-mig using -o.

The C tool accepts the following option:

-c-prefix=prefix
This option specifies the prefix to attach to the generated constants and functions. If omitted, message-type is used.

For each non-array field fname of structure message-type, the following functions and constants are generated:

*
prefix_fname_get(): get field's value
*
prefix_fname_set(): get field's value
*
prefix_fname_OFFSETBITS: bit offset of field
*
prefix_fname_OFFSET: byte offset of field
*
prefix_fname_SIZEBITS: size in bits of field
*
prefix_fname_SIZE: size in bytes of field

For each array field fname of structure message-type, the following functions and constants are generated:

*
prefix_fname_get(): get field's value
*
prefix_fname_set(): get field's value
*
prefix_fname_offsetbits(): bit offset of array element
*
prefix_fname_offset(): byte offset of array element
*
prefix_fname_ELEMENTSIZEBITS: size in bits of array element
*
prefix_fname_ELEMENTSIZE: size in bytes of array element
*
prefix_fname_NUMELEMENTS: number of elements in array (absent for variable-sized arrays)
*
prefix_fname_NUMELEMENTS_i: size of ith array dimension

Embedded structures in message-type are expanded, using _ to separate the structure name and its fields. A field of an array of embedded structures is considered to be an array.

Errors

nescc-mig reports an error if nescc cannot compile msg-format-file, if message-type isn't found or if it contains pointers.

See Also

The generated code for the various tools refer to libraries that are distributed with the TinyOS operating system. Please refer to that project's documentation for more information.

mig(1), nescc(1), nescc-ncg(1)

Referenced By

nescc-ncg(1).

April 27, 2004