[Tinyos-help] C struct questions in TinyOS

[Supasate Choochaisri]

Hi all,

I'm not quite familiar with C language, so I doubt about the following codes
in Mate (TinyOS-VM) :

1: typedef struct {
2:   int16_t var;
3: } MateValueVariable;
4:
5: typedef struct {
6:   uint8_t type;
7:   uint8_t size;
8:   int16_t entries[MATE_BUF_LEN];
9: } MateDataBuffer;
10:
11: typedef struct {
12:   MateDataBuffer* var;
13: } MateBufferVariable;
14:
15: typedef struct {
16:   uint8_t type;
17:   union {
18:     MateValueVariable value;
19:     MateBufferVariable buffer;
20:   };
21: } MateStackVariable;


Line 1-3, compare to "typedef int16_t MateValueVariable", how difference is
it?

Line 11-13, why do we have to use this struct? why not just change line 9 to
MateBufferVariable and delete line 11-13?

Thanks in advance,

Supasate
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