| 1 | ; Project name : Assembly Library
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| 2 | ; Description : Functions for file access.
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| 3 |
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| 4 | ; Section containing code
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| 5 | SECTION .text
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| 6 |
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| 7 | ;--------------------------------------------------------------------
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| 8 | ; FileIO_OpenWithPathInDSSIandFileAccessInAL
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| 9 | ; Parameters:
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| 10 | ; AL: FILE_ACCESS.(mode)
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| 11 | ; DS:SI: Ptr to NULL terminated path or file name
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| 12 | ; Returns:
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| 13 | ; AX: DOS error code if CF set
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| 14 | ; BX: File handle if CF cleared
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| 15 | ; CF: Clear if file opened successfully
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| 16 | ; Set if error
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| 17 | ; Corrupts registers:
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| 18 | ; AX, BX
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| 19 | ;--------------------------------------------------------------------
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| 20 | ALIGN JUMP_ALIGN
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| 21 | FileIO_OpenWithPathInDSSIandFileAccessInAL:
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| 22 | xchg dx, si ; Path now in DS:DX
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| 23 | mov ah, OPEN_EXISTING_FILE
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| 24 | int DOS_INTERRUPT_21h
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| 25 | xchg si, dx
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| 26 | mov bx, ax ; Copy file handle to BX
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| 27 | ret
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| 28 |
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| 29 |
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| 30 | ;--------------------------------------------------------------------
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| 31 | ; FileIO_ReadDXCXbytesToDSSIusingHandleFromBX
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| 32 | ; Parameters:
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| 33 | ; BX: File handle
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| 34 | ; DX:CX: Number of bytes to read
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| 35 | ; DS:SI: Ptr to destination buffer
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| 36 | ; Returns:
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| 37 | ; AX: DOS error code if CF set
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| 38 | ; CF: Clear if successful
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| 39 | ; Set if error
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| 40 | ; Corrupts registers:
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| 41 | ; AX
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| 42 | ;--------------------------------------------------------------------
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| 43 | ALIGN JUMP_ALIGN
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| 44 | FileIO_ReadDXCXbytesToDSSIusingHandleFromBX:
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| 45 | push bp
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| 46 | mov bp, FileIO_ReadCXbytesToDSSIusingHandleFromBX
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| 47 | call SplitLargeReadOrWritesToSmallerBlocks
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| 48 | pop bp
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| 49 | ret
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| 50 |
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| 51 | ;--------------------------------------------------------------------
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| 52 | ; File position is updated so next read will start where
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| 53 | ; previous read stopped.
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| 54 | ;
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| 55 | ; FileIO_ReadCXbytesToDSSIusingHandleFromBX
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| 56 | ; Parameters:
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| 57 | ; BX: File handle
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| 58 | ; CX: Number of bytes to read
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| 59 | ; DS:SI: Ptr to destination buffer
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| 60 | ; Returns:
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| 61 | ; AX: Number of bytes actually read if successful (0 if at EOF before call)
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| 62 | ; DOS error code if CF set
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| 63 | ; CF: Clear if successful
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| 64 | ; Set if error
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| 65 | ; Corrupts registers:
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| 66 | ; Nothing
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| 67 | ;--------------------------------------------------------------------
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| 68 | ALIGN JUMP_ALIGN
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| 69 | FileIO_ReadCXbytesToDSSIusingHandleFromBX:
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| 70 | xchg dx, si ; DS:DX now points to destination buffer
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| 71 | mov ah, READ_FROM_FILE_OR_DEVICE
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| 72 | int DOS_INTERRUPT_21h
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| 73 | xchg si, dx
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| 74 | ret
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| 75 |
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| 76 |
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| 77 | ;--------------------------------------------------------------------
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| 78 | ; FileIO_WriteDXCXbytesFromDSSIusingHandleFromBX
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| 79 | ; Parameters:
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| 80 | ; BX: File handle
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| 81 | ; DX:CX: Number of bytes to write
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| 82 | ; DS:SI: Ptr to source buffer
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| 83 | ; Returns:
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| 84 | ; AX: DOS error code if CF set
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| 85 | ; CF: Clear if successful
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| 86 | ; Set if error
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| 87 | ; Corrupts registers:
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| 88 | ; AX
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| 89 | ;--------------------------------------------------------------------
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| 90 | ALIGN JUMP_ALIGN
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| 91 | FileIO_WriteDXCXbytesFromDSSIusingHandleFromBX:
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| 92 | push bp
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| 93 | mov bp, FileIO_WriteCXbytesFromDSSIusingHandleFromBX
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| 94 | call SplitLargeReadOrWritesToSmallerBlocks
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| 95 | pop bp
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| 96 | ret
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| 97 |
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| 98 | ;--------------------------------------------------------------------
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| 99 | ; File position is updated so next write will start where
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| 100 | ; previous write stopped.
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| 101 | ;
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| 102 | ; FileIO_WriteCXbytesFromDSSIusingHandleFromBX:
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| 103 | ; Parameters:
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| 104 | ; BX: File handle
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| 105 | ; CX: Number of bytes to write
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| 106 | ; DS:SI: Ptr to source buffer
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| 107 | ; Returns:
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| 108 | ; AX: Number of bytes actually written if successful (EOF check)
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| 109 | ; DOS error code if CF set
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| 110 | ; CF: Clear if successful
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| 111 | ; Set if error
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| 112 | ; Corrupts registers:
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| 113 | ; Nothing
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| 114 | ;--------------------------------------------------------------------
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| 115 | ALIGN JUMP_ALIGN
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| 116 | FileIO_WriteCXbytesFromDSSIusingHandleFromBX:
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| 117 | xchg dx, si ; DS:DX now points to source buffer
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| 118 | mov ah, WRITE_TO_FILE_OR_DEVICE
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| 119 | int DOS_INTERRUPT_21h
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| 120 | xchg si, dx
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| 121 | ret
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| 122 |
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| 123 |
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| 124 | ;--------------------------------------------------------------------
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| 125 | ; SplitLargeReadOrWritesToSmallerBlocks
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| 126 | ; Parameters:
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| 127 | ; BX: File handle
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| 128 | ; BP: Ptr to transfer function
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| 129 | ; DX:CX: Number of bytes to transfer
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| 130 | ; DS:SI: Ptr to transfer buffer
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| 131 | ; Returns:
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| 132 | ; AX: DOS error code if CF set
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| 133 | ; CF: Clear if successful
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| 134 | ; Set if error
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| 135 | ; Corrupts registers:
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| 136 | ; AX
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| 137 | ;--------------------------------------------------------------------
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| 138 | ALIGN JUMP_ALIGN
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| 139 | SplitLargeReadOrWritesToSmallerBlocks:
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| 140 | push ds
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| 141 | push si
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| 142 | push dx
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| 143 | push cx
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| 144 |
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| 145 | xchg ax, cx ; DX:AX now holds bytes to transfer
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| 146 | mov cx, SPLIT_SIZE_FOR_LARGE_TRANSFERS
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| 147 | div cx ; AX = Number of full transfers
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| 148 | push dx ; Bytes for last transfer
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| 149 | test ax, ax
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| 150 | jz SHORT .TransferRemainingBytes
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| 151 | xchg dx, ax ; DX = Number of full transfers
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| 152 |
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| 153 | ALIGN JUMP_ALIGN
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| 154 | .TransferNextBytes:
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| 155 | call NormalizeDSSI
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| 156 | call bp ; Transfer function
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| 157 | jc SHORT .ErrorOccurredDuringTransfer
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| 158 | add si, SPLIT_SIZE_FOR_LARGE_TRANSFERS
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| 159 | dec dx
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| 160 | jnz SHORT .TransferNextBytes
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| 161 | .TransferRemainingBytes:
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| 162 | pop cx ; CX = Bytes for last transfer
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| 163 | jcxz .ReturnErrorCodeInAX ; No remaining bytes
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| 164 | call NormalizeDSSI
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| 165 | call bp
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| 166 | .ReturnErrorCodeInAX:
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| 167 | pop cx
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| 168 | pop dx
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| 169 | pop si
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| 170 | pop ds
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| 171 | ret
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| 172 | .ErrorOccurredDuringTransfer:
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| 173 | pop cx ; Remove bytes for last transfer
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| 174 | jmp SHORT .ReturnErrorCodeInAX
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| 175 |
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| 176 | ;--------------------------------------------------------------------
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| 177 | ; NormalizeDSSI
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| 178 | ; Parameters
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| 179 | ; DS:SI: Ptr to normalize
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| 180 | ; Returns:
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| 181 | ; DS:SI: Normalized pointer
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| 182 | ; Corrupts registers:
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| 183 | ; Nothing
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| 184 | ;--------------------------------------------------------------------
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| 185 | ALIGN JUMP_ALIGN
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| 186 | NormalizeDSSI:
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| 187 | push dx
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| 188 | push ax
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| 189 | NORMALIZE_FAR_POINTER ds, si, ax, dx
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| 190 | pop ax
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| 191 | pop dx
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| 192 | ret
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| 193 |
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| 194 |
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| 195 | ;--------------------------------------------------------------------
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| 196 | ; FileIO_GetFileSizeToDXAXusingHandleFromBXandResetFilePosition:
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| 197 | ; Parameters:
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| 198 | ; BX: File handle
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| 199 | ; Returns:
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| 200 | ; DX:AX: Signed file size (if CF cleared)
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| 201 | ; AX: DOS error code (if CF set)
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| 202 | ; CF: Clear if successful
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| 203 | ; Set if error
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| 204 | ; Corrupts registers:
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| 205 | ; Nothing
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| 206 | ;--------------------------------------------------------------------
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| 207 | ALIGN JUMP_ALIGN
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| 208 | FileIO_GetFileSizeToDXAXusingHandleFromBXandResetFilePosition:
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| 209 | push cx
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| 210 |
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| 211 | ; Get file size to DX:AX
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| 212 | xor cx, cx
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| 213 | xor dx, dx
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| 214 | mov al, SEEK_FROM.endOfFile
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| 215 | call FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX
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| 216 | jc SHORT .ReturnFileError
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| 217 | push dx
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| 218 | push ax
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| 219 |
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| 220 | ; Reset file position
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| 221 | xor dx, dx
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| 222 | mov al, SEEK_FROM.startOfFile
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| 223 | call FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX
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| 224 | pop ax
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| 225 | pop dx
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| 226 |
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| 227 | .ReturnFileError:
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| 228 | pop cx
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| 229 | ret
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| 230 |
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| 231 |
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| 232 | ;--------------------------------------------------------------------
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| 233 | ; FileIO_CloseUsingHandleFromBX
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| 234 | ; Parameters:
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| 235 | ; BX: File handle
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| 236 | ; Returns:
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| 237 | ; AX: DOS error code if CF set
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| 238 | ; CF: Clear if file closed successfully
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| 239 | ; Set if error
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| 240 | ; Corrupts registers:
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| 241 | ; AX
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| 242 | ;--------------------------------------------------------------------
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| 243 | ALIGN JUMP_ALIGN
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| 244 | FileIO_CloseUsingHandleFromBX:
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| 245 | mov ah, CLOSE_FILE
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| 246 | SKIP2B f ; cmp ax, <next instruction>
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| 247 | ; Fall to FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX
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| 248 |
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| 249 |
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| 250 | ;--------------------------------------------------------------------
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| 251 | ; FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX:
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| 252 | ; Parameters:
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| 253 | ; AL: SEEK_FROM.(origin)
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| 254 | ; BX: File handle
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| 255 | ; CX:DX: Signed offset to seek starting from AL
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| 256 | ; Returns:
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| 257 | ; DX:AX: New file position in bytes from start of file (if CF cleared)
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| 258 | ; AX: DOS error code (if CF set)
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| 259 | ; CF: Clear if successful
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| 260 | ; Set if error
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| 261 | ; Corrupts registers:
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| 262 | ; Nothing
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| 263 | ;--------------------------------------------------------------------
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| 264 | FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX:
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| 265 | mov ah, SET_CURRENT_FILE_POSITION
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| 266 | int DOS_INTERRUPT_21h
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| 267 | ret
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