#define _POSIX_C_SOURCE 200809L

/* Podprogram ‹count_distinct› spočítá počet různých bajtů
 * na vstupu (zadaném popisovačem ‹fd›). Tento počet v případě
 * úspěchu vrátí, jinak vrátí hodnotu -1. */

int count_distinct( int fd );

/* ┄┄┄┄┄┄┄ %< ┄┄┄┄┄┄┄┄┄┄ následují testy ┄┄┄┄┄┄┄┄┄┄ %< ┄┄┄┄┄┄┄ */

#include <assert.h>     /* assert */
#include <err.h>        /* NONPOSIX: err */
#include <errno.h>      /* errno */
#include <fcntl.h>      /* open */
#include <unistd.h>     /* write, read, close, unlink */

static void close_or_warn( int fd, const char *name )
{
    if ( close( fd ) == -1 )
        warn( "closing %s", name );
}

static void unlink_if_exists( const char *name )
{
    if ( unlink( name ) == -1 && errno != ENOENT )
        err( 2, "unlinking '%s'", name );
}

static void mk_tmp( const char *name, const char *str, int len )
{
    unlink_if_exists( name );

    int fd = open( name, O_CREAT | O_TRUNC | O_WRONLY, 0666 );

    if ( fd == -1 )
        err( 2, "creating %s", name );

    if ( write( fd, str, len ) == -1 )
        err( 2, "writing %s", name );

    close_or_warn( fd, name );
}

static int open_or_die( const char *name )
{
    int fd = open( name, O_RDONLY );

    if ( fd == -1 )
        err( 2, "opening %s", name );

    return fd;
}

int mk_tmp_and_open_or_die( const char *str, int len )
{
    const char *name = "./zt.r2_test_in";

    mk_tmp( name, str, len );
    return open_or_die( name );
}

int main( void )
{
    int fd;
    const char *tmp_file = "./zt.r2_test_in";

    fd = mk_tmp_and_open_or_die( "ahoj", 4 );
    assert( count_distinct( fd ) == 4 );
    close_or_warn( fd, tmp_file );

    fd = mk_tmp_and_open_or_die( "hello world", 11 );
    assert( count_distinct( fd ) == 8 );
    close_or_warn( fd, tmp_file );

    fd = mk_tmp_and_open_or_die( "\xff\x1\x2\x3\xfe\x4\x1\xff\xfe", 9 );
    assert( count_distinct( fd ) == 6 );
    close_or_warn( fd, tmp_file );

    unsigned char data[] =
    {
        0xbf, 0xfb, 0x10, 0x01, 0xab, 0xba, 0xcd, 0xdc,
        0xbf, 0xfb, 0x10, 0x01, 0xab, 0xba, 0xcd, 0xdc,
        0xbf, 0xfb, 0x10, 0x01, 0xab, 0xba, 0xcd, 0xdc,
        0xbf, 0xfb, 0x10, 0x01, 0xab, 0xba, 0xcd, 0xdc,
        0xbf, 0xfb, 0x10, 0x01, 0xab, 0xba, 0xcd, 0xdc,
        0xbf, 0xfb, 0x10, 0x01, 0xab, 0xba, 0xcd, 0xdc,
        0xbf, 0xfb, 0x10, 0x01, 0xab, 0xba, 0xcd, 0xdc,
        0xbf, 0xfb, 0x10, 0x01, 0xab, 0xba, 0xcd, 0xdc,
        0xee
    };

    fd = mk_tmp_and_open_or_die( ( char * ) data, sizeof( data ) );
    assert( count_distinct( fd ) == 9 );
    close_or_warn( fd, tmp_file );

    unlink_if_exists( tmp_file );
    return 0;
}