Problem with cinput

[giovannipozzobon]

I’m using the libc65 library with Calypsis. A very simple program that requires input from the user.

#include <stdio.h>
#include "debug_calypis.h"
#include "mega65/conio.h"
 
 unsigned char stringa[13];

void main (){
conioinit();

// Clear screen and go to the first position
clrscr();
gotoxy(0,0);

cinput(stringa, 13, CINPUT_ACCEPT_ALPHA);

}

The program freezes and monitor is starting.

I investigated and solved the problem by adding this control
if (len ==0) return;

I hypothesize that the lcopy function messes up when the string length is zero, at least with the Calypsis compiler. I don't know with others.
If the length is greater than zero there is no problem.

void cputsxy(unsigned char x, unsigned char y, const unsigned char* s)
{
    const unsigned char len = (unsigned char)my_strlen((const char*)s);
    if (len ==0) return;
    const unsigned int offset = (y * (unsigned int)g_curScreenW) + x;
    lcopy((unsigned long)s, SCREEN_RAM_BASE + offset, len);
    lfill(COLOR_RAM_BASE + offset, g_curTextColor, len);
    g_curY = y + ((x + len) / g_curScreenW);
    g_curX = (x + len) % g_curScreenW;
}

The problem is that at MEGA65 hardware level at least, len=0 means 64Kbyte. This explains the problem.

[mlund]

I did a quick test with llvm-mos and the problem seem to exist there as well. lcopy() uses DMA copy via the F018 list structure where count number of bytes is defined. Could you try to test lcopy() separately to verify that it does nothing when length is zero?

If lcopy() is OK there, I see two routes:

1. Submit a PR for cputsxy() with the suggested range check, or
2. Do nothing but add a comment to cputsxy() that the string must be non-zero. On restricted systems like ours, this might be the best option(?)

[mlund]

Pushed ab8d787 that modifies documentation.

[giovannipozzobon]

I vote for the first choice because inside the c_input function there is this code that put '\0' in the buffer.

    for (i = 0; i < buflen; ++i) {
        buffer[i] = '\0';
    } 

[mlund]

OK, how about placing the range check just before calling cputsxy(), i.e. at line 735 of cinput(). It is less invasive and wouldn't impose checks on known non-zero strings.

[giovannipozzobon]

Do you mean like something that?

        if (strlen(buffer) != 0)  
            cputsxy(sx, sy, buffer);

Ok for me.

[mlund]

Do you mean like something that?

        if (strlen(buffer) != 0)  
            cputsxy(sx, sy, buffer);

Ok for me.

Yes, exactly. Would you mind making a pull request?

[giovannipozzobon]

Do you mean like something that?

        if (strlen(buffer) != 0)  
            cputsxy(sx, sy, buffer);

Ok for me.

Yes, exactly. Would you mind making a pull request?

OK. Done.
Thanks.