source: trunk/minix/commands/ibm/screendump.c@ 15

/*      screendump 1.2 - dump the contents of the console
 *                                                      Author: Kees J. Bot
 *                                                              16 Dec 1994
 */
#define nil 0
#include <sys/types.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <termios.h>
#include <sys/ioctl.h>

#define BIOS_CRTBASE    0x00463L        /* BIOS parameters: CRT base. */
#define CRTBASE_MONO    0x03B4          /* Value of CRT base for mono mode. */

#define MONO_BASE       0xB0000L        /* Screen memory in monochrome mode. */
#define COLOR_BASE      0xB8000L        /* ... colour mode. */

#define DEF_COLS        80              /* Default screen geometry. */
#define DEF_ROWS        25

#define MAX_COLS        132             /* Maximum screen geometry. */
#define MAX_ROWS        60

char MEMORY[] =         "/dev/mem";     /* Memory device to read screen. */
int mfd;                                /* Open memory device. */

void tell(const char *message)
{
        write(2, message, strlen(message));
}

void fatal(const char *label)
{
        const char *err= strerror(errno);

        tell("screendump: ");
        tell(label);
        tell(": ");
        tell(err);
        tell("\n");
        exit(1);
}

long video_base(void)
/* Is it monochrome or colour? */
{
        static unsigned short bios_crtbase;

        if (lseek(mfd, (off_t) BIOS_CRTBASE, SEEK_SET) == -1) fatal(MEMORY);
        switch (read(mfd, &bios_crtbase, sizeof(bios_crtbase))) {
        case -1:
                fatal(MEMORY);
        default:
                tell("screendump: can't obtain BIOS parameter: short read\n");
                exit(1);
        case sizeof(bios_crtbase):
                /* Fine */;
        }

        return bios_crtbase == CRTBASE_MONO ? MONO_BASE : COLOR_BASE;
}

void main(void)
{
        static unsigned char screen[MAX_COLS * MAX_ROWS * 2];
        unsigned char *ps;
        long base;
        int lfd;
        int row;
        int nrows, ncols;
        struct winsize winsize;

        /* Open the memory device. */
        if ((mfd= open(MEMORY, O_RDONLY)) < 0) fatal(MEMORY);

        base= video_base();

        /* Read screen memory. */
        if (lseek(mfd, base, SEEK_SET) == -1) fatal(MEMORY);

        switch (read(mfd, screen, sizeof(screen))) {
        case -1:
                fatal(MEMORY);
        default:
                tell("screendump: can't obtain screen dump: short read\n");
                exit(1);
        case sizeof(screen):
                /* Fine */;
        }

        /* Try to obtain the screen geometry from /dev/log. */
        ncols= DEF_COLS;
        nrows= DEF_ROWS;
        if ((lfd= open("/dev/log", O_WRONLY)) != -1
                && ioctl(lfd, TIOCGWINSZ, &winsize) == 0
        ) {
                if (40 <= winsize.ws_col && winsize.ws_col <= MAX_COLS) {
                        ncols= winsize.ws_col;
                }
                if (25 <= winsize.ws_row && winsize.ws_row <= MAX_COLS) {
                        nrows= winsize.ws_row;
                }
        }
        if (lfd != -1) close(lfd);

        /* Print the contents of the screen line by line.  Omit trailing
         * blanks.  Note that screen memory consists of pairs of characters
         * and attribute bytes.
         */
        ps= screen;
        for (row= 0; row < nrows; row++) {
                char line[MAX_COLS + 1];
                char *pl= line;
                int column;
                int blanks= 0;

                for (column= 0; column < ncols; column++) {
                        if (*ps <= ' ') {
                                /* Skip trailing junk. */
                                blanks++;
                        } else {
                                /* Reinsert blanks and add a character. */
                                while (blanks > 0) { *pl++= ' '; blanks--; }
                                *pl++= *ps;
                        }
                        /* Skip character and attribute byte. */
                        ps+= 2;
                }
                *pl++= '\n';
                if (write(1, line, pl - line) < 0) fatal("stdout");
        }
        exit(0);
}