VeraCrypt/src/Boot/Windows/BootConsoleIo.cpp

/*
 Derived from source code of TrueCrypt 7.1a, which is
 Copyright (c) 2008-2012 TrueCrypt Developers Association and which is governed
 by the TrueCrypt License 3.0.

 Modifications and additions to the original source code (contained in this file) 
 and all other portions of this file are Copyright (c) 2013-2016 IDRIX
 and are governed by the Apache License 2.0 the full text of which is
 contained in the file License.txt included in VeraCrypt binary and source
 code distribution packages.
*/

#include "Platform.h"
#include "Bios.h"
#include "BootConsoleIo.h"
#include "BootDebug.h"
#include "BootStrings.h"


static int ScreenOutputDisabled = 0;

void DisableScreenOutput ()
{
	++ScreenOutputDisabled;
}


void EnableScreenOutput ()
{
	--ScreenOutputDisabled;
}


void PrintChar (char c)
{
#ifdef TC_BOOT_TRACING_ENABLED
	WriteDebugPort (c);
#endif

	if (ScreenOutputDisabled)
		return;

	__asm
	{
		mov bx, 7
		mov al, c
		mov ah, 0xe
		int 0x10
	}
}


void PrintCharAtCursor (char c)
{
	if (ScreenOutputDisabled)
		return;

	__asm
	{
		mov bx, 7
		mov al, c
		mov cx, 1
		mov ah, 0xa
		int 0x10
	}
}


void Print (const char *str)
{
	char c;
	while (c = *str++)
		PrintChar (c);
}


void Print (uint32 number)
{
	char str[12];
	int pos = 0;
	while (number >= 10)
	{
		str[pos++] = (char) (number % 10) + '0';
		number /= 10;
	}
	str[pos] = (char) (number % 10) + '0';
	
	while (pos >= 0)
		PrintChar (str[pos--]);
}


void Print (const uint64 &number)
{
	if (number.HighPart == 0)
		Print (number.LowPart);
	else
		PrintHex (number);
}


void PrintHex (byte b)
{
	PrintChar (((b >> 4) >= 0xA ? 'A' - 0xA : '0') + (b >> 4));
	PrintChar (((b & 0xF) >= 0xA ? 'A' - 0xA : '0') + (b & 0xF));
}


void PrintHex (uint16 data)
{
	PrintHex (byte (data >> 8));
	PrintHex (byte (data));
}


void PrintHex (uint32 data)
{
	PrintHex (uint16 (data >> 16));
	PrintHex (uint16 (data));
}


void PrintHex (const uint64 &data)
{
	PrintHex (data.HighPart);
	PrintHex (data.LowPart);
}

void PrintRepeatedChar (char c, int n)
{
	while (n-- > 0)
		PrintChar (c);
}


void PrintEndl ()
{
	Print ("\r\n");
}


void PrintEndl (int cnt)
{
	while (cnt-- > 0)
		PrintEndl ();
}


void Beep ()
{
	PrintChar (7);
}


void InitVideoMode ()
{
	if (ScreenOutputDisabled)
		return;

	__asm
	{
		// Text mode 80x25
		mov ax, 3
		int 0x10

		// Page 0
		mov ax, 0x500
		int 0x10
	}
}


void ClearScreen ()
{
	if (ScreenOutputDisabled)
		return;

	__asm
	{
		// White text on black
		mov bh, 7
		xor cx, cx
		mov dx, 0x184f
		mov ax, 0x600
		int 0x10

		// Cursor at 0,0
		xor bh, bh
		xor dx, dx
		mov ah, 2
		int 0x10
	}
}


void PrintBackspace ()
{
	PrintChar (TC_BIOS_CHAR_BACKSPACE);
	PrintCharAtCursor (' ');
}


void PrintError (const char *message)
{
	Print (TC_BOOT_STR_ERROR);
	Print (message);
	PrintEndl();
	Beep();
}


void PrintErrorNoEndl (const char *message)
{
	Print (TC_BOOT_STR_ERROR);
	Print (message);
	Beep();
}


byte GetShiftFlags ()
{
	byte flags;
	__asm
	{
		mov ah, 2
		int 0x16
		mov flags, al
	}

	return flags;
}


byte GetKeyboardChar ()
{
	return GetKeyboardChar (nullptr);
}


byte GetKeyboardChar (byte *scanCode)
{
	// Work around potential BIOS bugs (Windows boot manager polls the keystroke buffer)
	while (!IsKeyboardCharAvailable());

	byte asciiCode;
	byte scan;
	__asm
	{
		mov ah, 0
		int 0x16
		mov asciiCode, al
		mov scan, ah
	}
	
	if (scanCode)
		*scanCode = scan;

	return asciiCode;
}


bool IsKeyboardCharAvailable ()
{
	bool available = false;
	__asm
	{
		mov ah, 1
		int 0x16
		jz not_avail
		mov available, true
	not_avail:
	}

	return available;
}


bool EscKeyPressed ()
{
	if (IsKeyboardCharAvailable ())
	{
		byte keyScanCode;
		GetKeyboardChar (&keyScanCode);
		return keyScanCode == TC_BIOS_KEY_ESC;
	}

	return false;
}


void ClearBiosKeystrokeBuffer ()
{
	__asm
	{
		push es
		xor ax, ax
		mov es, ax
		mov di, 0x41e
		mov cx, 32
		cld
		rep stosb
		pop es
	}
}


bool IsPrintable (char c)
{
	return c >= ' ' && c <= '~';
}

bool IsDigit (char c)
{
	return c >= '0' && c <= '9';
}


int GetString (char *buffer, size_t bufferSize)
{
	byte c;
	byte scanCode;
	size_t pos = 0;

	while (pos < bufferSize)
	{
		c = GetKeyboardChar (&scanCode);

		if (scanCode == TC_BIOS_KEY_ENTER)
			break;
		
		if (scanCode == TC_BIOS_KEY_ESC)
			return 0;

		buffer[pos++] = c;
		PrintChar (IsPrintable (c) ? c : ' ');
	}

	return pos;
}