source: xtideuniversalbios/trunk/Assembly_Library/Src/File/Drive.asm@ 177

Last change on this file since 177 was 133, checked in by krille_n_@…, 14 years ago

Size optimizations in various files in the Assembly Library. Also a very small change to a string in XTIDE_Universal_BIOS_Configurator_v2/Src/Strings.asm
File size: 4.6 KB
Line 
1; Project name : Assembly Library
2; Description : Functions for accessing drives.
3
4
5; Section containing code
6SECTION .text
7
8;--------------------------------------------------------------------
9; Drive_GetNumberOfAvailableDrivesToAX
10; Parameters:
11; Nothing
12; Returns:
13; AX: Number of available drives
14; Corrupts registers:
15; Nothing
16;--------------------------------------------------------------------
17ALIGN JUMP_ALIGN
18Drive_GetNumberOfAvailableDrivesToAX:
19 push dx
20 push cx
21
22 call Drive_GetFlagsForAvailableDrivesToDXAX
23 call Bit_GetSetCountToCXfromDXAX
24 xchg ax, cx
25
26 pop cx
27 pop dx
28 ret
29
30
31;--------------------------------------------------------------------
32; Drive_GetFlagsForAvailableDrivesToDXAX
33; Parameters:
34; Nothing
35; Returns:
36; DX:AX: Flags containing valid drives (bit 0 = drive A, bit 1 = drive B ...)
37; Corrupts registers:
38; Nothing
39;--------------------------------------------------------------------
40ALIGN JUMP_ALIGN
41Drive_GetFlagsForAvailableDrivesToDXAX:
42 push cx
43 push bx
44 mov dx, DosCritical_HandlerToIgnoreAllErrors
45 call DosCritical_InstallNewHandlerFromCSDX
46
47 call .GetNumberOfPotentiallyValidDriveLettersToCX
48 xor bx, bx
49 xor ax, ax ; Temporary use BX:AX for flags
50 cwd ; Start from drive 0
51 call .CheckDriveValidityUntilCXisZero
52 mov dx, bx ; Flags now in DX:AX
53
54 call DosCritical_RestoreDosHandler
55 pop bx
56 pop cx
57 ret
58
59;--------------------------------------------------------------------
60; .GetNumberOfPotentiallyValidDriveLettersToCX
61; Parameters:
62; Nothing
63; Returns:
64; CX: Number of potentially valid drive letters available
65; Corrupts registers:
66; AX, DX
67;--------------------------------------------------------------------
68ALIGN JUMP_ALIGN
69.GetNumberOfPotentiallyValidDriveLettersToCX:
70 call Drive_GetDefaultToAL
71 xchg dx, ax ; Default drive to DL
72 call Drive_SetDefaultFromDL
73 eMOVZX cx, al ; Number of potentially valid drive letters available
74 MIN_U cx, 32
75 ret
76
77;--------------------------------------------------------------------
78; .CheckDriveValidityUntilCXisZero
79; Parameters:
80; CX: Number of potentially valid drive letters left
81; DL: Drive number (00h=A:, 01h=B: ...)
82; BX:AX: Flags for drive numbers
83; Returns:
84; BX:AX: Flags for valid drive numbers
85; Corrupts registers:
86; CX, DX
87;--------------------------------------------------------------------
88ALIGN JUMP_ALIGN
89.CheckDriveValidityUntilCXisZero:
90 call .IsValidDriveNumberInDL
91 jnz SHORT .PrepareToCheckNextDrive
92 call .SetFlagToBXAXfromDriveInDL
93ALIGN JUMP_ALIGN
94.PrepareToCheckNextDrive:
95 inc dx
96 loop .CheckDriveValidityUntilCXisZero
97 ret
98
99;--------------------------------------------------------------------
100; .IsValidDriveNumberInDL
101; Parameters:
102; DL: Drive number (00h=A:, 01h=B: ...)
103; Returns:
104; ZF: Set if drive number is valid
105; Cleared if drive number is invalid
106; Corrupts registers:
107; Nothing
108;--------------------------------------------------------------------
109ALIGN JUMP_ALIGN
110.IsValidDriveNumberInDL:
111 push ds
112 push bx
113 push ax
114
115 inc dx ; Default drive is 00h and first drive is 01h
116 mov ah, GET_DOS_DRIVE_PARAMETER_BLOCK_FOR_SPECIFIC_DRIVE
117 int DOS_INTERRUPT_21h
118 dec dx
119 test al, al
120
121 pop ax
122 pop bx
123 pop ds
124 ret
125
126;--------------------------------------------------------------------
127; .SetFlagToBXAXfromDriveInDL
128; Parameters:
129; DL: Drive number (0...31)
130; BX:AX: Flags containing drive numbers
131; Returns:
132; BX:AX: Flags with wanted drive bit set
133; Corrupts registers:
134; Nothing
135;--------------------------------------------------------------------
136ALIGN JUMP_ALIGN
137.SetFlagToBXAXfromDriveInDL:
138 push cx
139
140 mov cl, dl
141 xchg dx, bx
142 call Bit_SetToDXAXfromIndexInCL
143 xchg bx, dx
144
145 pop cx
146 ret
147
148
149;--------------------------------------------------------------------
150; Drive_GetDefaultToAL
151; Parameters:
152; Nothing
153; Returns:
154; AL: Current default drive (00h=A:, 01h=B: ...)
155; Corrupts registers:
156; AH
157;--------------------------------------------------------------------
158ALIGN JUMP_ALIGN
159Drive_GetDefaultToAL:
160 mov ah, GET_CURRENT_DEFAULT_DRIVE
161 SKIP2B f ; cmp ax, <next instruction>
162 ; Fall to Drive_SetDefaultFromDL
163
164
165;--------------------------------------------------------------------
166; Drive_SetDefaultFromDL
167; Parameters:
168; DL: New default drive (00h=A:, 01h=B: ...)
169; Returns:
170; AL: Number of potentially valid drive letters available
171; Corrupts registers:
172; AH
173;--------------------------------------------------------------------
174Drive_SetDefaultFromDL:
175 mov ah, SELECT_DEFAULT_DRIVE
176 int DOS_INTERRUPT_21h
177 ret
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