Thread: Text insertion not working as expected

I narrowed down some string problems I was having to these 2 functions, the text at b4 to B->count is supposed to be moved across to the new end of the string but it's not doing as intended, I can see no reason for this either:

Code:

SHARED_EXP dint cramTextc( void *ud, STRING *B, uint b4, uint not0 )
{
	uint i = (b4 < B->count) ? b4 : B->count - !!(B->count);
	dint err = growTextc( ud, B, not0 );
	if ( err )
	{
		SHARED_ECHO_ERRNO( stdout, err );
		return err;
	}
	if ( not0 )
	{
		uint c = B->count;
		uint j = c - not0;
		uchar *txt = B->array;
		uchar *pos = txt + (B->Vsize * i);
		uchar *mov = txt + (B->Vsize - j);
		uchar *end = txt + (B->Vsize * c);

		while ( mov > pos )
			*(--end) = *(--mov);

		while ( end > pos )
			*(--end) = 032; /* Substitute character */
	}
	return 0;
}
SHARED_EXP dint	cramTextn( void *ud, STRING *B, uint b4, ptr str, uint not0 )
{
	uint i = (b4 < B->count) ? b4 : B->count - !!(B->count);
	dint err = growTextc( ud, B, not0 );
	if ( err )
	{
		SHARED_ECHO_ERRNO( stdout, err );
		return err;
	}
	if ( not0 )
	{
		uint c = B->count;
		uint j = c - not0;
		uchar *txt = B->array;
		uchar *pos = txt + (B->Vsize * i);
		uchar *mov = txt + (B->Vsize - j);
		uchar *end = txt + (B->Vsize * c);

		while ( mov > pos )
			*(--end) = *(--mov);
		memcpy( pos, str, B->Vsize * not0 );
	}
	return 0;
}

These are core functions that other functions call for growth, insertion & overwriting (count is reset to 0 prior to the call for the last one) instead of re-inventing the wheel for every type of character (char, wchar_t, char8_t, char16_t, char32_t, TCHAR) so I need them to work, anyone have any ideas why it's not doing as intended?

Welp, dunno what I did wrong but fixed it with a call to memmove instead

Code:

SHARED_EXP dint cramTextc( void *ud, STRING *B, uint b4, uint not0 )
{
	uint p = B->count;
	uint i = (b4 < p) ? b4 : p - !!p;
	dint err = growTextc( ud, B, not0 );
	if ( err )
	{
		SHARED_ECHO_ERRNO( stdout, err );
		return err;
	}
	if ( not0 )
	{
		uint k = i + not0;
		uint n = p - i;
		dint f = 0;
		uchar *txt = B->array;
		uchar *dst = txt + (B->Vsize * i);
		uchar *end = txt + (B->Vsize * k);

		for ( p = 0; p < sizeof(dint); ++p )
			f = (f << CHAR_BIT) | 032;

		memmove( end, dst, B->Vsize * n );
		memset( dst, f, B->Vsize * not0 );
	}
	return 0;
}
SHARED_EXP dint	cramTextn( void *ud, STRING *B, uint b4, ptr str, uint not0 )
{
	uint p = B->count;
	uint i = (b4 < p) ? b4 : p - !!p;
	dint err = growTextc( ud, B, not0 );
	if ( err )
	{
		SHARED_ECHO_ERRNO( stdout, err );
		return err;
	}
	if ( not0 )
	{
		uint k = i + not0;
		uint n = p - i;
		uchar *txt = B->array;
		uchar *dst = txt + (B->Vsize * i);
		uchar *end = txt + (B->Vsize * k);


		memmove( end, dst, B->Vsize * n );
		memcpy( dst, str, B->Vsize * not0 );
	}
	return 0;
}

> Welp, dunno what I did wrong but fixed it with a call to memmove instead
Because memmove has guaranteed behaviour if the two areas overlap.

memcpy does not, so can screw up on overlapped copies.

Yeah but I had performed a manual copy prior to that, if you try looking at the previous snippets then you'll find memcpy was never the problem, NEVER

Well I guess your luck ran out then.

If there is any chance your memory areas overlap, then memcpy is the WRONG tool for the job, regardless of how many days/months/years you claim "it wasn't a problem before".

Originally Posted by Salem

Well I guess your luck ran out then.

If there is any chance your memory areas overlap, then memcpy is the WRONG tool for the job, regardless of how many days/months/years you claim "it wasn't a problem before".

As I said before, I move the target bytes out of the way 1st before copying to them, that's the whole point of the loop that was prior to the memcpy call, after that loop the bytes that would've been lost should've been where the null terminator would've been copied and onwards, in other words when inserting X in STR at point 0 STR would first become STR before the characters where  is would be overwritten with X