concatenating single chars to multi char arrays

Hi

I have a problem assigning a single character into a pointer and an array larger than 1 - I think I know why this is but I am unsure about how to overcome it...

Code:

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char TempChar[3]
 char SinChar[1];

// At any time StoreChar could contain 1 to 3 characters
// - I want whatever characters are stored in it to be assigned
//to *data - I think the interger cast causes problems but it is
//necessary - how can I convert TempChar to int without messing
//up the data?

*data= int(TempChar);

//Later on I wish to concatenate SinChar (a single char
// array) to TempChar - this seems to work but always has
// nonsense characters as well - I think this is due to a single
//character being concatenated to a array which could contain
//either 1 or 2 characters - how can I do this without the
//nonsense characters?

strcat(TempChar, SinCheck);

---

Any help much appreciated!

Jimbo

> char SinChar[1];
It needs to be
char SinChar[2]; // a single char as a string (don't forget the \0)

SinChar[0] = theChar;
SinChar[1] = '\0';

Then you can strcat() it to whatever you want, providing there is room to append a char.

Adding to Salem's description, strcat() operates on strings, not single characters. And by definition a string must have a null or 0 byte at the end of it. Therefore, your 'single character' must be two characters, 2nd char is 0.

Code:

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#define strcatchar(__str,__cc) \
{ \
    int  __slen; \
    __str[__slen = strlen(__str)] = __cc; \
    __str[__slen+1] = '\0'; \
}

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Quote:

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Originally posted by qed

Code:

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#define strcatchar(__str,__cc) \
{ \
    int  __slen; \
    __str[__slen = strlen(__str)] = __cc; \
    __str[__slen+1] = '\0'; \
}

---

---

Loose the __'s. They make the code almost unreadable.

Code:

---

#define strcatchar(str,cc) \
{ \
    int  slen; \
    str[slen = strlen(str)] = cc; \
    str[slen+1] = '\0'; \
}

---

will suffice.

and the line str[slen = strlen(str)] = cc; is a nice trick but obfuscates the routine. a simple
slen = strlen(str);
str[slen] = cc;
does the job just as well without the confusion.

The __'s are used to try to keep the variable names out of regular the program usable namespace. For example, try the following with your macro:

Code:

---

char * slen = malloc (16);
*slen = '\0';
strcatchar(slen, 'x');

---

The two equals on a line may be a little unusual, but there is nothing actually obfuscating about it. The order of operations is strongly implied, and the natural expectation is the correct one.

> The __'s are used to try to keep the variable names out of regular the program usable namespace
Except now you've trampled over the system namespace. All identifiers with a leading _ are reserved.

Since you introduce a new scope with the braces, there is no problem with using slen

Quote:

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Except now you've trampled over the system namespace. All identifiers with a leading _ are reserved.

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Yes, I realize this. But there is no way to make an inaccessible dynamic name space inside a C macro, so I just chose the one that the non-system programmer will avoid. Making it work with any particular compiler is just a matter of porting it.

Quote:

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Since you introduce a new scope with the braces, there is no problem with using slen

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Yeah, but look at my example. The results will not be the code that was intended.