readhexstring has multiple problems about xpost

[luser-dr00g]

Thanks for digging into this. It seems to me that the whole code could probably be simpler overall since it doesn't need to worry about partial digits like the <hex> syntax does.

for( n=0; !eof && n < S.comp_.sz; n++ ){
    do (c[0] = xpost_file_getc(f)) == EOF && ++eof; while( ! (eof || strchr(hex, c[0])) );
    if( !eof ){
        do (c[1] = xpost_file_getc(f)) == EOF && ++eof; while( ! (eof || strchr(hex, c[1])) );
        if( !eof ) s[n] = ((strchr(hex, toupper(c[0])) - hex) << 4)
                            |  (strchr(hex, toupper(c[1])) - hex);
    }
}
S.comp_.sz = n;

This version seems more correct given your analysis but I'll put it through some tests before committing. And probably the style I have here is too compact per our style rules. The do...while loops could probably be factored into a helper function with a descriptive name.

[luser-dr00g]

Oops. This still has the n++ problem you already diagnosed.

[luser-dr00g]

Take 2.

int readhexdigit( Xpost_File *f, int *p ){
    int eof = 0;
    do (*p = xpost_file_getc(f)) == EOF && ++eof;
    while( ! (eof || strchr(hex, *p)) );
    return eof;
}

for( n = 0; !eof && n < S.comp_.sz; n++ ){
    eof += readhexdigit(f, &c[0]);
    if( !eof ) eof += readhexdigit(f, &c[1]);
    if( eof ) break;
    s[n] = ((strchr(hex, toupper(c[0])) - hex) << 4) | (strchr(hex, toupper(c[1])) - hex);
}
S.comp_.sz = n;

[luser-dr00g]

Written, tested, committed, pushed.