C/Objective-C memory issue?

hi all,
wonder if can input solve issue.
background.
working on method in obj-c uses straight c functions.


here code:

code:

-(nsstring*) chartobinary: (nsstring *) acharacter  {  	char *charfortest = (char *)[acharacter utf8string];  	char *temp = (dectobin(charfortest));  	nslog(@"%s", temp);  	nsstring *bytesofstring =  [nsstring stringwithcstring:temp  												  encoding:nsutf16stringencoding];  	return bytesofstring;  	  }  

completeness, function dectobin, not correct,( yet, unable point of checking logic).

code:

char *dectobin(char * inputchar)  {  	char binaryarr[eight_byte_array];  	  	int = 0;  	int charvalue = (int) inputchar[0];  	while (charvalue) {  		  		  		binaryarr[i++] =  (charvalue % 2) ? '1': '0';  		charvalue /= 2;  		  	}  	binaryarr[i] = '\0';  	  	  	char *t = reversestring(binaryarr);  	return t;  	  }

here happens. in obj-c code, "temp" contains string, of nature "100110" etc. but, line bytesofstring called, temp reverts \"000
thinking that, , knowledge of memory management in c rudimentary, "temp" being released? not sure. appreciated insight.
and, other function mentioned.

code:

char *reversestring(char  *inputstring)  {  	int i, j;  	char t[strlen(inputstring)+1];  	strcpy(t,inputstring);  	for (i = 0, j = strlen(inputstring) - 1; j >= 0; j--, i++)  	{  		*(inputstring +i) = *(t + j);  	}  	  	inputstring[i] = '\0';  	  	//printf("\"inputstring\":%s\n", inputstring);  	  	return inputstring;  }  

 

your dectobin() returning pointer local variable (the array binaryarr). local variables not survive after function returns. same c or objective-c. strictly speaking, correct term "automatic", "local" refers scope, not lifetime.

http://en.wikipedia.org/wiki/local_variable
http://en.wikipedia.org/wiki/automatic_variable

refer c reference manual if wikipedia articles aren't sufficient. c keyword (hence, objective-c keyword) 'auto', , implicit storage type variables declared inside function bodies, 'static' implicit storage type variables declared outside function bodies.

also, loop in dectobin() never end if charvalue negative, , overflow buffer until kills something. should iterate 8 times, not indefinitely. if want produce string no leading zeros, need better algorithm have.

code wrong:

code:

stringwithcstring:temp encoding:nsutf16stringencoding  

the encoding of temp (if temp survived long enough) not utf16. it's ascii or utf8, or 8-bit encoding compatible ascii in first 128 code-points. know because dectobin() operating on char types, not wchar_t types, , default interpretation of character constants '1' , '0' ascii.

 

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