How to stop processing static const unsigned char * const tab[][]

[nenpa8lo]

Hi, I have this code:

static const unsigned char *const Msgs[1][16] =
	{
		{
			"Please", "go to the", "user menu", "- tanks -",
			"", 		"",		"",		"",
			"",		"", 		"",		"",
			"",		"",		"",		""
		}
	};
.
.
.
void fun(void)
{
    unsigned char i;

    for (i = 0; Msgs[0][i]; i++)
        {
         printf("%s", (unsigned char *)Msgs[0][i]);
        }
}

I don't know do I aproach this problem correctly, but thing is I want to stop 'for loop' when there is nothing else to display. In fact Msgs[][] is much bigger and sometimes is has one string to display and sometimes 10, 15 etc. How can I detect end of data?

[matsp]

    for (i = 0; Msgs[0][i][0]; i++)
        {
         printf("%s", (unsigned char *)Msgs[0][i]);
        }

would break the loop when the string is "".

Or, if you change your "" to NULL, you could use the code you originally wrote.

Edit: Or just remove all of the "" bits, that will set the value to NULL by default [Pedantery: except for machines where NULL is not the same as a pointer with all bits set to zero - but I think those are extremely rare anyways]

--
Mats

[laserlight]

You can either store the number of elements or append a terminating null pointer.

[nenpa8lo]

And how can I get pointer to Msgs[][] and check that instead of Msgs[][][0] (btw that works fine). I'd like to use point as I have Msgs2 as well so just extra code to do something like Ptr=Msgs2 after I foud Msgs[][][0]==NULL or Ptr==NULL.

[IceDane]

And how can I get pointer to Msgs[][] and check that instead of Msgs[][][0] (btw that works fine). I'd like to use point as I have Msgs2 as well so just extra code to do something like Ptr=Msgs2 after I foud Msgs[][][0]==NULL or Ptr==NULL.

Do what matsp said, remove all the "" bits, and then assign the pointer:

unsigned char * cPtr;

for(i = 0; cPtr = Msgs[0][i]; i++)
     printf("%s", cPtr);

[matsp]

Do what matsp said, remove all the "" bits, and then assign the pointer:

unsigned char * cPtr;

for(i = 0; cPtr = Msgs[0][i]; i++)
     printf("%s", cPtr);

Why do you need a pointer? Yes, I agree that it avoids indexing the array twice, but the compiler probably does that anyways...

--
Mats

[nenpa8lo]

Final looks like this:

static const unsigned char *const Msgs[1][16] =
	{
		{
			"Please", "go to the", "user menu", "- tanks -",
			"", 		"",		"",		"",
			"",		"", 		"",		"",
			"",		"",		"",		""
		},
                {...},  /* More msgs here */
                {...},  /* And even more */
                {...}
	};
.
.
.
void DisplayMsg(unsigned int MsgNum)
{
    unsigned char i;

    for (i = 0; *Msgs[MsgNum][i]; i++)
        {
         printf("%s", (unsigned char *)Msgs[MsgNum][i]);
        }
}

BTW NULL doesn't compile when repleacing "". I use IAR compiler for 16bit embedded microcontroller H8.

[IceDane]

Why do you need a pointer? Yes, I agree that it avoids indexing the array twice, but the compiler probably does that anyways...

--
Mats

Thought that was what he was asking. He says something about a pointer to Msgs.