1 | ; Project name : Assembly Library
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2 | ; Description : Functions for accessing drives.
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3 |
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4 | ;
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5 | ; XTIDE Universal BIOS and Associated Tools
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6 | ; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team.
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7 | ;
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8 | ; This program is free software; you can redistribute it and/or modify
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9 | ; it under the terms of the GNU General Public License as published by
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10 | ; the Free Software Foundation; either version 2 of the License, or
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11 | ; (at your option) any later version.
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12 | ;
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13 | ; This program is distributed in the hope that it will be useful,
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14 | ; but WITHOUT ANY WARRANTY; without even the implied warranty of
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15 | ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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16 | ; GNU General Public License for more details.
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17 | ; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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18 | ;
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19 |
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20 | ; Section containing code
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21 | SECTION .text
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22 |
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23 | ;--------------------------------------------------------------------
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24 | ; Drive_GetNumberOfAvailableDrivesToAX
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25 | ; Parameters:
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26 | ; Nothing
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27 | ; Returns:
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28 | ; AX: Number of available drives
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29 | ; Corrupts registers:
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30 | ; Nothing
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31 | ;--------------------------------------------------------------------
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32 | ALIGN JUMP_ALIGN
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33 | Drive_GetNumberOfAvailableDrivesToAX:
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34 | push dx
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35 | push cx
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36 |
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37 | call Drive_GetFlagsForAvailableDrivesToDXAX
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38 | call Bit_GetSetCountToCXfromDXAX
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39 | xchg ax, cx
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40 |
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41 | pop cx
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42 | pop dx
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43 | ret
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44 |
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45 |
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46 | ;--------------------------------------------------------------------
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47 | ; Drive_GetFlagsForAvailableDrivesToDXAX
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48 | ; Parameters:
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49 | ; Nothing
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50 | ; Returns:
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51 | ; DX:AX: Flags containing valid drives (bit 0 = drive A, bit 1 = drive B ...)
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52 | ; Corrupts registers:
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53 | ; Nothing
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54 | ;--------------------------------------------------------------------
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55 | ALIGN JUMP_ALIGN
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56 | Drive_GetFlagsForAvailableDrivesToDXAX:
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57 | push cx
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58 | push bx
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59 | mov dx, DosCritical_HandlerToIgnoreAllErrors
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60 | call DosCritical_InstallNewHandlerFromCSDX
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61 |
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62 | call .GetNumberOfPotentiallyValidDriveLettersToCX
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63 | xor bx, bx
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64 | xor ax, ax ; Temporary use BX:AX for flags
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65 | cwd ; Start from drive 0
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66 | call .CheckDriveValidityUntilCXisZero
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67 | mov dx, bx ; Flags now in DX:AX
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68 |
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69 | call DosCritical_RestoreDosHandler
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70 | pop bx
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71 | pop cx
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72 | ret
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73 |
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74 | ;--------------------------------------------------------------------
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75 | ; .GetNumberOfPotentiallyValidDriveLettersToCX
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76 | ; Parameters:
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77 | ; Nothing
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78 | ; Returns:
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79 | ; CX: Number of potentially valid drive letters available
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80 | ; Corrupts registers:
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81 | ; AX, DX
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82 | ;--------------------------------------------------------------------
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83 | ALIGN JUMP_ALIGN
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84 | .GetNumberOfPotentiallyValidDriveLettersToCX:
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85 | call Drive_GetDefaultToAL
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86 | xchg dx, ax ; Default drive to DL
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87 | call Drive_SetDefaultFromDL
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88 | cmp al, 32 ; Number of potentially valid drive letters available
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89 | jb SHORT .Below32
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90 | mov al, 32
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91 | .Below32:
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92 | cbw
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93 | xchg cx, ax
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94 | ret
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95 |
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96 | ;--------------------------------------------------------------------
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97 | ; .CheckDriveValidityUntilCXisZero
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98 | ; Parameters:
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99 | ; CX: Number of potentially valid drive letters left
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100 | ; DL: Drive number (00h=A:, 01h=B: ...)
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101 | ; BX:AX: Flags for drive numbers
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102 | ; Returns:
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103 | ; BX:AX: Flags for valid drive numbers
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104 | ; Corrupts registers:
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105 | ; CX, DX
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106 | ;--------------------------------------------------------------------
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107 | ALIGN JUMP_ALIGN
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108 | .CheckDriveValidityUntilCXisZero:
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109 | call .IsValidDriveNumberInDL
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110 | jnz SHORT .PrepareToCheckNextDrive
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111 | call .SetFlagToBXAXfromDriveInDL
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112 | ALIGN JUMP_ALIGN
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113 | .PrepareToCheckNextDrive:
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114 | inc dx
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115 | loop .CheckDriveValidityUntilCXisZero
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116 | ret
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117 |
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118 | ;--------------------------------------------------------------------
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119 | ; .IsValidDriveNumberInDL
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120 | ; Parameters:
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121 | ; DL: Drive number (00h=A:, 01h=B: ...)
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122 | ; Returns:
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123 | ; ZF: Set if drive number is valid
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124 | ; Cleared if drive number is invalid
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125 | ; Corrupts registers:
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126 | ; Nothing
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127 | ;--------------------------------------------------------------------
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128 | ALIGN JUMP_ALIGN
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129 | .IsValidDriveNumberInDL:
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130 | push ds
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131 | push bx
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132 | push ax
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133 |
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134 | inc dx ; Default drive is 00h and first drive is 01h
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135 | mov ax, CHECK_IF_BLOCK_DEVICE_REMOTE ; Needs DOS 3.1+
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136 | mov bx, dx
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137 | push dx
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138 | int DOS_INTERRUPT_21h
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139 | pop dx
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140 | jnc SHORT .DriveIsValid
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141 | cmp ax, ERR_DOS_INVALID_DRIVE
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142 | je SHORT .DriveIsNotValid
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143 | ; Fall back to old method if ERR_DOS_FUNCTION_NUMBER_INVALID
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144 |
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145 | mov ah, GET_DOS_DRIVE_PARAMETER_BLOCK_FOR_SPECIFIC_DRIVE
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146 | int DOS_INTERRUPT_21h
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147 | .DriveIsValid:
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148 | .DriveIsNotValid:
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149 | dec dx
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150 | test al, al
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151 |
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152 | pop ax
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153 | pop bx
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154 | pop ds
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155 | ret
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156 |
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157 | ;--------------------------------------------------------------------
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158 | ; .SetFlagToBXAXfromDriveInDL
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159 | ; Parameters:
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160 | ; DL: Drive number (0...31)
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161 | ; BX:AX: Flags containing drive numbers
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162 | ; Returns:
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163 | ; BX:AX: Flags with wanted drive bit set
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164 | ; Corrupts registers:
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165 | ; Nothing
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166 | ;--------------------------------------------------------------------
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167 | ALIGN JUMP_ALIGN
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168 | .SetFlagToBXAXfromDriveInDL:
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169 | push cx
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170 |
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171 | mov cl, dl
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172 | xchg dx, bx
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173 | call Bit_SetToDXAXfromIndexInCL
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174 | xchg bx, dx
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175 |
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176 | pop cx
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177 | ret
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178 |
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179 |
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180 | ;--------------------------------------------------------------------
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181 | ; Drive_GetDefaultToAL
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182 | ; Parameters:
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183 | ; Nothing
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184 | ; Returns:
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185 | ; AL: Current default drive (00h=A:, 01h=B: ...)
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186 | ; Corrupts registers:
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187 | ; AH
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188 | ;--------------------------------------------------------------------
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189 | ALIGN JUMP_ALIGN
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190 | Drive_GetDefaultToAL:
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191 | mov ah, GET_CURRENT_DEFAULT_DRIVE
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192 | SKIP2B f ; cmp ax, <next instruction>
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193 | ; Fall to Drive_SetDefaultFromDL
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194 |
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195 |
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196 | ;--------------------------------------------------------------------
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197 | ; Drive_SetDefaultFromDL
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198 | ; Parameters:
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199 | ; DL: New default drive (00h=A:, 01h=B: ...)
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200 | ; Returns:
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201 | ; AL: Number of potentially valid drive letters available
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202 | ; Corrupts registers:
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203 | ; AH
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204 | ;--------------------------------------------------------------------
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205 | Drive_SetDefaultFromDL:
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206 | mov ah, SELECT_DEFAULT_DRIVE
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207 | int DOS_INTERRUPT_21h
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208 | ret
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