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can someone fix my function? (small one)

sporty · 2001-12-12T18:03:32

im trying to write a function that will return just the filename from a file path (folders notated by FOWARD SLASHES ''/''), in other words, "c:/windows/desktop/blah/hello.bmp" would return "hello.bmp" my function worked, only it created a memory leak, so im trying to pass a variable to the function now and have it modify it, but i am stumped..this is my code //file being the filepath, i.e "c:/folder/filename.xxx" //returnfile being the string that returns the filename void getfile(char *file, char *&returnFile) { int ofs=0, i, len; int l; char *sztmp; l = strlen(file); for (i=0; i<l; i++) { if (file[i] == ''/'') ofs=i+1; } len=l-ofs; sztmp = new char[len]; for (i=0; i<len; i++) { strcpy(&sztmp[i], &file[ofs+i]); } strcpy(&returnFile, &sztmp); delete [] sztmp; } void main() { char filename[56]; getfile("c:/windows/desktop/hello.bmp", filename); cout << filename << endl; } unfortunately and obviously this isn''t working, heh, so can you guys show me what i _should_ be doing?

General and Gameplay Programming Programming

Started by sporty December 11, 2001 08:00 PM

14 comments, last by sporty 22 years, 4 months ago

JonStelly

127

December 12, 2001 12:10 AM

  bool getfile(char* lpFullFileName, char** plpFileName){	//FIND LAST DIRECTORY DELIM	(*plpFileName) = strrchr(lpFullFileName, ''/'');		//''/'' CHARACTER FOUND	if(*plpFileName != NULL){		//MOVED TO NEXT CHARACTER		(*plpFileName)++;		return true;	}	//''/'' CHARACTER NOT FOUND	return false;}int main(int argc, char* argv[]){	char *lpFile;	getfile("c:/testdir/test.txt", &lpFile);	cout << lpFile << endl;	return 0;}

scaught

122

December 12, 2001 12:14 AM

This is the part that gets me:

  ...for (i=0; i<len; i++) {    strcpy(&sztmp[i], &file[ofs+i]);	}...

Holy extraneous copies, batman...

Edited by - scaught on December 12, 2001 1:15:59 AM

Anonymous

December 12, 2001 12:19 AM

>for (i=0; i<len; i++) {
> strcpy(&sztmp, &file[ofs+i]);
>}

Why are you iterating through file and doing an strcpy on each character? You''re dereferencing each character in the string and trying to use strcpy on it but &sztmp isn''t a proper cstring–it isn''t terminated by ''\0''. You could just change the body of this loop to: sztmp = file[ofs+i]; and then after the loop put: sztmp[len] = ''\0''; You''re also doing something similar in the following: >strcpy(&returnFile, &sztmp); Here you''re passing a pointer to a pointer a char for each parameter. You shouldn''t be dereferencing returnFile or sztemp. Checkout the documentation on strcpy. The easiest way to do this is: <pre> void getfile(char *file, char *returnFile) { int length, base, i; base = i = length-1; for (;i >= 0 && file != ''/''; i–; base–<img src="wink.gif" width=15 height=15 align=middle>; strcpy(returnFile, &file[base]); } </pre>

amemorex

122

December 12, 2001 04:02 PM

quote:Original post by JonStelly

    bool getfile(char* lpFullFileName, char** plpFileName)

whoa there, what does "char**" do? and whats it mean when all of you are talking about "derefrencing your variables"..how do you DEreference something?

Beer Hunter

712

December 12, 2001 05:38 PM

int PositionOfLastSlash = strrchr("c:/fun/blah/etc/nifty.bmp", ''/'');

You can use that to simplify things a bit. I''m surprised that no-one has mentioned that yet.

Oluseyi

2,123

December 12, 2001 06:03 PM

I was going to mention strtok(); I''m not terribly up on Standard C Library string functions. Nice one, Beer Hunter.

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Thanks to Kylotan for the idea!

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