| 1 | ; File name : FileIO.asm
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| 2 | ; Project name : Assembly Library
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| 3 | ; Created date : 1.9.2010
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| 4 | ; Last update : 3.9.2010
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| 5 | ; Author : Tomi Tilli
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| 6 | ; Description : Functions for file access.
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| 7 |
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| 8 |
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| 9 | ; File access and sharing modes
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| 10 | struc FILE_ACCESS
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| 11 | .ReadOnly resb 1
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| 12 | .WriteOnly resb 1
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| 13 | .ReadAndWrite resb 1
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| 14 | endstruc
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| 15 |
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| 16 | ; Origin of file seek
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| 17 | struc SEEK_FROM
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| 18 | .startOfFile resb 1
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| 19 | .currentFilePosition resb 1
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| 20 | .endOfFile resb 1
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| 21 | endstruc
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| 22 |
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| 23 |
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| 24 | ; Section containing code
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| 25 | SECTION .text
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| 26 |
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| 27 | ;--------------------------------------------------------------------
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| 28 | ; FileIO_OpenWithPathInDSSIandFileAccessInAL
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| 29 | ; Parameters:
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| 30 | ; AL: FILE_ACCESS.(mode)
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| 31 | ; DS:SI: Ptr to NULL terminated path or file name
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| 32 | ; Returns:
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| 33 | ; AX: DOS error code if CF set
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| 34 | ; BX: File handle if CF cleared
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| 35 | ; CF: Clear if file opened successfully
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| 36 | ; Set if error
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| 37 | ; Corrupts registers:
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| 38 | ; AX, BX
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| 39 | ;--------------------------------------------------------------------
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| 40 | ALIGN JUMP_ALIGN
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| 41 | FileIO_OpenWithPathInDSSIandFileAccessInAL:
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| 42 | xchg dx, si ; Path now in DS:DX
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| 43 | mov ah, OPEN_EXISTING_FILE
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| 44 | int DOS_INTERRUPT_21h
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| 45 | xchg si, dx
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| 46 | ret
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| 47 |
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| 48 |
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| 49 | ;--------------------------------------------------------------------
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| 50 | ; FileIO_CloseUsingHandleFromBX
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| 51 | ; Parameters:
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| 52 | ; BX: File handle
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| 53 | ; Returns:
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| 54 | ; AX: DOS error code if CF set
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| 55 | ; CF: Clear if file closed successfully
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| 56 | ; Set if error
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| 57 | ; Corrupts registers:
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| 58 | ; AX
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| 59 | ;--------------------------------------------------------------------
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| 60 | ALIGN JUMP_ALIGN
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| 61 | FileIO_CloseUsingHandleFromBX:
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| 62 | mov ah, CLOSE_FILE
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| 63 | int DOS_INTERRUPT_21h
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| 64 | ret
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| 65 |
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| 66 |
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| 67 | ;--------------------------------------------------------------------
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| 68 | ; File position is updated so next read will start where
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| 69 | ; previous read stopped.
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| 70 | ;
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| 71 | ; FileIO_ReadCXbytesToDSSIusingHandleFromBX
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| 72 | ; Parameters:
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| 73 | ; BX: File handle
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| 74 | ; CX: Number of bytes to read
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| 75 | ; DS:SI: Ptr to destination buffer
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| 76 | ; Returns:
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| 77 | ; AX: Number of bytes actually read if successfull (0 if at EOF before call)
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| 78 | ; DOS error code if CF set
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| 79 | ; CF: Clear if successfull
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| 80 | ; Set if error
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| 81 | ; Corrupts registers:
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| 82 | ; Nothing
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| 83 | ;--------------------------------------------------------------------
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| 84 | ALIGN JUMP_ALIGN
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| 85 | FileIO_ReadCXbytesToDSSIusingHandleFromBX:
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| 86 | xchg dx, si ; DS:DX now points to source buffer
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| 87 | mov ah, READ_FROM_FILE_OR_DEVICE
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| 88 | int DOS_INTERRUPT_21h
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| 89 | xchg si, dx
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| 90 | ret
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| 91 |
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| 92 |
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| 93 | ;--------------------------------------------------------------------
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| 94 | ; File position is updated so next write will start where
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| 95 | ; previous write stopped.
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| 96 | ;
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| 97 | ; FileIO_WriteCXbytesFromDSSIusingHandleFromBX:
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| 98 | ; Parameters:
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| 99 | ; BX: File handle
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| 100 | ; CX: Number of bytes to write
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| 101 | ; DS:SI: Ptr to source buffer
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| 102 | ; Returns:
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| 103 | ; AX: Number of bytes actually written if successfull (EOF check)
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| 104 | ; DOS error code if CF set
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| 105 | ; CF: Clear if successfull
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| 106 | ; Set if error
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| 107 | ; Corrupts registers:
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| 108 | ; Nothing
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| 109 | ;--------------------------------------------------------------------
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| 110 | ALIGN JUMP_ALIGN
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| 111 | FileIO_WriteCXbytesFromDSSIusingHandleFromBX:
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| 112 | xchg dx, si ; DS:DX now points to source buffer
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| 113 | mov ah, WRITE_TO_FILE_OR_DEVICE
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| 114 | int DOS_INTERRUPT_21h
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| 115 | xchg si, dx
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| 116 | ret
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| 117 |
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| 118 |
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| 119 | ;--------------------------------------------------------------------
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| 120 | ; FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX:
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| 121 | ; Parameters:
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| 122 | ; AL: SEEK_FROM.(origin)
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| 123 | ; BX: File handle
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| 124 | ; DX:AX: Seek offset (signed)
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| 125 | ; Returns:
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| 126 | ; AX: DOS error code if CF set
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| 127 | ; CF: Clear if successfull
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| 128 | ; Set if error
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| 129 | ; Corrupts registers:
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| 130 | ; Nothing
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| 131 | ;--------------------------------------------------------------------
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| 132 | ALIGN JUMP_ALIGN
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| 133 | FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX:
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| 134 | push dx
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| 135 | push cx
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| 136 |
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| 137 | mov cx, dx ; DOS wants high word in CX
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| 138 | xchg dx, ax ; DOS wants low word in DX
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| 139 | mov ah, SET_CURRENT_FILE_POSITION
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| 140 | int DOS_INTERRUPT_21h
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| 141 |
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| 142 | pop cx
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| 143 | pop dx
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| 144 | ret
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