[41] | 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 | ; Section containing code |
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| 6 | SECTION .text |
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| 7 | |
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| 8 | ;-------------------------------------------------------------------- |
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| 9 | ; Drive_GetNumberOfAvailableDrivesToAX |
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| 10 | ; Parameters: |
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| 11 | ; Nothing |
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| 12 | ; Returns: |
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| 13 | ; AX: Number of available drives |
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| 14 | ; Corrupts registers: |
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| 15 | ; Nothing |
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| 16 | ;-------------------------------------------------------------------- |
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| 17 | ALIGN JUMP_ALIGN |
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| 18 | Drive_GetNumberOfAvailableDrivesToAX: |
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| 19 | push dx |
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| 20 | push cx |
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| 21 | |
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| 22 | call Drive_GetFlagsForAvailableDrivesToDXAX |
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| 23 | call Bit_GetSetCountToCXfromDXAX |
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| 24 | xchg ax, cx |
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| 25 | |
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| 26 | pop cx |
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| 27 | pop dx |
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| 28 | ret |
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| 29 | |
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| 30 | |
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| 31 | ;-------------------------------------------------------------------- |
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| 32 | ; Drive_GetFlagsForAvailableDrivesToDXAX |
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| 33 | ; Parameters: |
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| 34 | ; Nothing |
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| 35 | ; Returns: |
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| 36 | ; DX:AX: Flags containing valid drives (bit 0 = drive A, bit 1 = drive B ...) |
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| 37 | ; Corrupts registers: |
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| 38 | ; Nothing |
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| 39 | ;-------------------------------------------------------------------- |
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| 40 | ALIGN JUMP_ALIGN |
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| 41 | Drive_GetFlagsForAvailableDrivesToDXAX: |
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| 42 | push cx |
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| 43 | push bx |
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| 44 | mov dx, DosCritical_HandlerToIgnoreAllErrors |
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| 45 | call DosCritical_InstallNewHandlerFromCSDX |
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| 46 | |
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| 47 | call .GetNumberOfPotentiallyValidDriveLettersToCX |
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| 48 | xor bx, bx |
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| 49 | xor ax, ax ; Temporary use BX:AX for flags |
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[133] | 50 | cwd ; Start from drive 0 |
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[41] | 51 | call .CheckDriveValidityUntilCXisZero |
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| 52 | mov dx, bx ; Flags now in DX:AX |
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| 53 | |
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| 54 | call DosCritical_RestoreDosHandler |
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| 55 | pop bx |
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| 56 | pop cx |
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| 57 | ret |
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| 58 | |
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| 59 | ;-------------------------------------------------------------------- |
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| 60 | ; .GetNumberOfPotentiallyValidDriveLettersToCX |
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| 61 | ; Parameters: |
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| 62 | ; Nothing |
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| 63 | ; Returns: |
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| 64 | ; CX: Number of potentially valid drive letters available |
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| 65 | ; Corrupts registers: |
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| 66 | ; AX, DX |
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| 67 | ;-------------------------------------------------------------------- |
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| 68 | ALIGN JUMP_ALIGN |
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| 69 | .GetNumberOfPotentiallyValidDriveLettersToCX: |
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| 70 | call Drive_GetDefaultToAL |
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| 71 | xchg dx, ax ; Default drive to DL |
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| 72 | call Drive_SetDefaultFromDL |
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| 73 | eMOVZX cx, al ; Number of potentially valid drive letters available |
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| 74 | MIN_U cx, 32 |
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| 75 | ret |
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| 76 | |
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| 77 | ;-------------------------------------------------------------------- |
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| 78 | ; .CheckDriveValidityUntilCXisZero |
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| 79 | ; Parameters: |
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| 80 | ; CX: Number of potentially valid drive letters left |
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| 81 | ; DL: Drive number (00h=A:, 01h=B: ...) |
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| 82 | ; BX:AX: Flags for drive numbers |
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| 83 | ; Returns: |
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| 84 | ; BX:AX: Flags for valid drive numbers |
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| 85 | ; Corrupts registers: |
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| 86 | ; CX, DX |
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| 87 | ;-------------------------------------------------------------------- |
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| 88 | ALIGN JUMP_ALIGN |
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| 89 | .CheckDriveValidityUntilCXisZero: |
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| 90 | call .IsValidDriveNumberInDL |
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| 91 | jnz SHORT .PrepareToCheckNextDrive |
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| 92 | call .SetFlagToBXAXfromDriveInDL |
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| 93 | ALIGN JUMP_ALIGN |
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| 94 | .PrepareToCheckNextDrive: |
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| 95 | inc dx |
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| 96 | loop .CheckDriveValidityUntilCXisZero |
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| 97 | ret |
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| 98 | |
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| 99 | ;-------------------------------------------------------------------- |
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| 100 | ; .IsValidDriveNumberInDL |
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| 101 | ; Parameters: |
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| 102 | ; DL: Drive number (00h=A:, 01h=B: ...) |
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| 103 | ; Returns: |
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| 104 | ; ZF: Set if drive number is valid |
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| 105 | ; Cleared if drive number is invalid |
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| 106 | ; Corrupts registers: |
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| 107 | ; Nothing |
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| 108 | ;-------------------------------------------------------------------- |
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| 109 | ALIGN JUMP_ALIGN |
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| 110 | .IsValidDriveNumberInDL: |
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| 111 | push ds |
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| 112 | push bx |
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| 113 | push ax |
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| 114 | |
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| 115 | inc dx ; Default drive is 00h and first drive is 01h |
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| 116 | mov ah, GET_DOS_DRIVE_PARAMETER_BLOCK_FOR_SPECIFIC_DRIVE |
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| 117 | int DOS_INTERRUPT_21h |
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| 118 | dec dx |
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| 119 | test al, al |
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| 120 | |
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| 121 | pop ax |
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| 122 | pop bx |
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| 123 | pop ds |
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| 124 | ret |
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| 125 | |
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| 126 | ;-------------------------------------------------------------------- |
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| 127 | ; .SetFlagToBXAXfromDriveInDL |
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| 128 | ; Parameters: |
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| 129 | ; DL: Drive number (0...31) |
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| 130 | ; BX:AX: Flags containing drive numbers |
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| 131 | ; Returns: |
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| 132 | ; BX:AX: Flags with wanted drive bit set |
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| 133 | ; Corrupts registers: |
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| 134 | ; Nothing |
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| 135 | ;-------------------------------------------------------------------- |
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| 136 | ALIGN JUMP_ALIGN |
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| 137 | .SetFlagToBXAXfromDriveInDL: |
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| 138 | push cx |
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| 139 | |
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| 140 | mov cl, dl |
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| 141 | xchg dx, bx |
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| 142 | call Bit_SetToDXAXfromIndexInCL |
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| 143 | xchg bx, dx |
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| 144 | |
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| 145 | pop cx |
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| 146 | ret |
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| 147 | |
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| 148 | |
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| 149 | ;-------------------------------------------------------------------- |
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| 150 | ; Drive_GetDefaultToAL |
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| 151 | ; Parameters: |
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| 152 | ; Nothing |
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| 153 | ; Returns: |
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| 154 | ; AL: Current default drive (00h=A:, 01h=B: ...) |
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| 155 | ; Corrupts registers: |
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| 156 | ; AH |
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| 157 | ;-------------------------------------------------------------------- |
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| 158 | ALIGN JUMP_ALIGN |
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| 159 | Drive_GetDefaultToAL: |
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| 160 | mov ah, GET_CURRENT_DEFAULT_DRIVE |
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[133] | 161 | SKIP2B f ; cmp ax, <next instruction> |
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| 162 | ; Fall to Drive_SetDefaultFromDL |
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[41] | 163 | |
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| 164 | |
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| 165 | ;-------------------------------------------------------------------- |
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| 166 | ; Drive_SetDefaultFromDL |
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| 167 | ; Parameters: |
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| 168 | ; DL: New default drive (00h=A:, 01h=B: ...) |
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| 169 | ; Returns: |
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| 170 | ; AL: Number of potentially valid drive letters available |
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| 171 | ; Corrupts registers: |
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| 172 | ; AH |
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| 173 | ;-------------------------------------------------------------------- |
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| 174 | Drive_SetDefaultFromDL: |
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| 175 | mov ah, SELECT_DEFAULT_DRIVE |
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| 176 | int DOS_INTERRUPT_21h |
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| 177 | ret |
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