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/* This file is part of the SvarCOM project and is published under the terms
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 * of the MIT license.
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 *
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 * Copyright (C) 2021 Mateusz Viste
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 *
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 * Permission is hereby granted, free of charge, to any person obtaining a
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 * copy of this software and associated documentation files (the "Software"),
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 * to deal in the Software without restriction, including without limitation
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 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
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 * and/or sell copies of the Software, and to permit persons to whom the
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 * Software is furnished to do so, subject to the following conditions:
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 *
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 * The above copyright notice and this permission notice shall be included in
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 * all copies or substantial portions of the Software.
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 *
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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 * DEALINGS IN THE SOFTWARE.
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 */
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/*
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/*
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 * cls
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 * cls
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 */
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 */
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static int cmd_cls(struct cmd_funcparam *p) {
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static int cmd_cls(struct cmd_funcparam *p) {
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  unsigned char screenw, screenh;
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  unsigned char screenw, screenh;
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  const char *ansiesc = "\x1B[2J$";
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  const char *ansiesc = "\x1B[2J$";
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  if (cmd_ishlp(p)) {
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  if (cmd_ishlp(p)) {
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    outputnl("Clears the screen");
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    outputnl("Clears the screen");
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    outputnl("");
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    outputnl("");
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    outputnl("CLS");
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    outputnl("CLS");
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    return(-1);
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    return(-1);
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  }
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  }
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  screenw = screen_getwidth();
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  screenw = screen_getwidth();
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  screenh = screen_getheight();
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  screenh = screen_getheight();
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  _asm {
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  _asm {
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    /* output an ANSI ESC code for "clear screen" in case the console is
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    /* output an ANSI ESC code for "clear screen" in case the console is
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     * some kind of terminal */
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     * some kind of terminal */
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    mov ah, 0x09     /* write $-terminated string to stdout */
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    mov ah, 0x09     /* write $-terminated string to stdout */
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    mov dx, ansiesc
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    mov dx, ansiesc
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    int 0x21
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    int 0x21
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    /* check what stdout is set to */
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    /* check what stdout is set to */
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    mov ax, 0x4400   /* IOCTL query device/flags flags */
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    mov ax, 0x4400   /* IOCTL query device/flags flags */
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    mov bx, 1        /* file handle (1 = stdout) */
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    mov bx, 1        /* file handle (1 = stdout) */
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    int 0x21         /* CF set on error, otherwise DX set with flags */
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    int 0x21         /* CF set on error, otherwise DX set with flags */
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    jc DONE          /* abort on error */
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    jc DONE          /* abort on error */
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    /* DX = 10000010
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    /* DX = 10000010
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            |   |||
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            |   |||
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            |   ||+--- indicates standard output
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            |   ||+--- indicates standard output
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            |   |+---- set if NUL device
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            |   |+---- set if NUL device
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            |   +----- set if CLOCK device
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            |   +----- set if CLOCK device
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            +--------- set if handle is a device (ie. not a file)
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            +--------- set if handle is a device (ie. not a file)
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            in other words, DL & 10001110 (8Eh) should result in 10000010 (82h)
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            in other words, DL & 10001110 (8Eh) should result in 10000010 (82h)
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            */
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            */
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    and dl, 0x8e
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    and dl, 0x8e
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    cmp dl, 0x82
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    cmp dl, 0x82
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    jne DONE         /* abort on error */
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    jne DONE         /* abort on error */
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    /* scroll vram out of screen */
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    /* scroll vram out of screen */
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    mov ax, 0x0600   /* scroll up entire rectangle */
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    mov ax, 0x0600   /* scroll up entire rectangle */
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    mov bh, 0x07     /* fill screen with white-on-black */
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    mov bh, 0x07     /* fill screen with white-on-black */
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    xor cx, cx       /* upper left location in CH,CL (0,0) */
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    xor cx, cx       /* upper left location in CH,CL (0,0) */
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    /* DX is bottom right location of rectangle (DH=row, DL=column) */
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    /* DX is bottom right location of rectangle (DH=row, DL=column) */
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    mov dh, [screenh]
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    mov dh, [screenh]
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    dec dh
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    dec dh
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    mov dl, [screenw]
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    mov dl, [screenw]
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    dec dl
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    dec dl
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    int 0x10
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    int 0x10
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    /* set cursor to top left corner (0,0) of the screen */
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    /* set cursor to top left corner (0,0) of the screen */
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    mov ah, 0x02     /* set cursor position */
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    mov ah, 0x02     /* set cursor position */
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    xor bh, bh       /* page number */
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    xor bh, bh       /* page number */
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    xor dx, dx       /* location in DH,DL */
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    xor dx, dx       /* location in DH,DL */
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    int 0x10
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    int 0x10
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    DONE:
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    DONE:
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  }
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  }
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  return(-1);
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  return(-1);
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}
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}
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