Atlas - SDL_dos.h
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1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2026 Sam Lantinga <[email protected]>
4
5  This software is provided 'as-is', without any express or implied
6  warranty.  In no event will the authors be held liable for any damages
7  arising from the use of this software.
8
9  Permission is granted to anyone to use this software for any purpose,
10  including commercial applications, and to alter it and redistribute it
11  freely, subject to the following restrictions:
12
13  1. The origin of this software must not be misrepresented; you must not
14     claim that you wrote the original software. If you use this software
15     in a product, an acknowledgment in the product documentation would be
16     appreciated but is not required.
17  2. Altered source versions must be plainly marked as such, and must not be
18     misrepresented as being the original software.
19  3. This notice may not be removed or altered from any source distribution.
20*/
21
22#include "SDL_internal.h"
23
24#ifndef SDL_dos_h_
25#define SDL_dos_h_
26
27#include <sys/farptr.h>
28
29// our MS-DOS port depends on the "fat DS" trick. djgpp docs try to warn you
30// away from this, but if it was good enough for Quake 1, it's good enough
31// for us!
32#include <sys/nearptr.h>
33
34// We are obviously a 32-bit protected mode (DPMI) program.
35#include <dpmi.h>
36
37// this is djgpp-specific.
38#include <go32.h>
39
40// this is DOS PC stuff, like interrupts and Intel i/o ports.
41#include <pc.h>
42
43// 8259 PIC (Programmable Interrupt Controller) ports and commands
44#define PIC1_COMMAND 0x20 // master PIC command port
45#define PIC1_DATA    0x21 // master PIC data (mask) port
46#define PIC2_COMMAND 0xA0 // slave PIC command port
47#define PIC2_DATA    0xA1 // slave PIC data (mask) port
48#define PIC_EOI      0x20 // end-of-interrupt command
49
50// Lock a range of code so it won't be paged out during interrupts.
51// Usage: DOS_LockCode(function_name, function_end_label)
52// The function_end_label must be defined immediately after the function.
53#define DOS_LockCode(start, end) \
54    _go32_dpmi_lock_code((void *)(start), (char *)(end) - (char *)(start))
55
56// Lock a range of data so it won't be paged out during interrupts.
57#define DOS_LockData(var, size) \
58    _go32_dpmi_lock_data((void *)&(var), (size))
59
60// Lock a single variable.
61#define DOS_LockVariable(var) \
62    DOS_LockData(var, sizeof(var))
63
64// Set up for C function definitions, even when using C++
65#ifdef __cplusplus
66extern "C" {
67#endif
68
69// This uses the "fat DS" trick to convert a physical address to a valid
70//  C pointer usable from protected mode.
71SDL_FORCE_INLINE void *DOS_PhysicalToLinear(const Uint32 physical)
72{
73    __djgpp_nearptr_enable(); // We need to re-enable this for large applications to work.
74    return (void *)(physical + __djgpp_conventional_base);
75}
76
77SDL_FORCE_INLINE Uint32 DOS_LinearToPhysical(void *linear)
78{
79    return ((Uint32)linear) - __djgpp_conventional_base;
80}
81
82SDL_FORCE_INLINE int DOS_IRQToVector(int irq)
83{
84    return irq + ((irq > 7) ? 104 : 8);
85}
86
87SDL_FORCE_INLINE void DOS_DisableInterrupts(void)
88{
89    __asm__ __volatile__("cli\n");
90}
91
92SDL_FORCE_INLINE void DOS_EnableInterrupts(void)
93{
94    __asm__ __volatile__("sti\n");
95}
96
97// Grab a single byte from a segment:offset.
98SDL_FORCE_INLINE Uint8 DOS_PeekUint8(const Uint32 segoffset)
99{
100    return (Uint8)_farpeekb(_dos_ds, ((segoffset & 0xFFFF0000) >> 12) + (segoffset & 0xFFFF));
101}
102
103// Grab a single 16-bit word from a segment:offset.
104SDL_FORCE_INLINE Uint16 DOS_PeekUint16(const Uint32 segoffset)
105{
106    return (Uint16)_farpeekw(_dos_ds, ((segoffset & 0xFFFF0000) >> 12) + (segoffset & 0xFFFF));
107}
108
109// Grab a single 32-bit dword from a segment:offset.
110SDL_FORCE_INLINE Uint32 DOS_PeekUint32(const Uint32 segoffset)
111{
112    return (Uint32)_farpeekl(_dos_ds, ((segoffset & 0xFFFF0000) >> 12) + (segoffset & 0xFFFF));
113}
114
115SDL_FORCE_INLINE void DOS_EndOfInterrupt(int irq)
116{
117    if (irq > 7) {
118        outportb(PIC2_COMMAND, PIC_EOI);
119    }
120    outportb(PIC1_COMMAND, PIC_EOI);
121}
122
123// Allocate memory under the 640k line; various real mode services and DMA transfers need this.
124//  malloc() returns data above 640k because we're a protected mode, 32-bit process, so this is
125//  only for specific needs.
126extern void *DOS_AllocateConventionalMemory(const int len, _go32_dpmi_seginfo *seginfo);
127
128// Allocate conventional memory suitable for DMA transfers.
129extern void *DOS_AllocateDMAMemory(const int len, _go32_dpmi_seginfo *seginfo);
130
131// Free conventional (or DMA, which _is_ conventional) memory.
132extern void DOS_FreeConventionalMemory(_go32_dpmi_seginfo *seginfo);
133
134// Get a SDL_malloc'd copy of a null-terminated string located at a real-mode segment:offset. This makes no promises about character encoding.
135char *DOS_GetFarPtrCString(const Uint32 segoffset);
136
137typedef void (*DOS_InterruptHookFn)(void);
138typedef struct DOS_InterruptHook
139{
140    DOS_InterruptHookFn fn;
141    int irq;
142    int interrupt_vector; // this is the _vector_ number, not the IRQ number!
143    _go32_dpmi_seginfo irq_handler_seginfo;
144    _go32_dpmi_seginfo original_irq_handler_seginfo;
145
146} DOS_InterruptHook;
147
148void DOS_HookInterrupt(int irq, DOS_InterruptHookFn fn, DOS_InterruptHook *hook); // `irq` is the IRQ number, not the interrupt vector number!
149void DOS_UnhookInterrupt(DOS_InterruptHook *hook, bool disable_interrupt);
150
151// Ends C function definitions when using C++
152#ifdef __cplusplus
153}
154#endif
155
156#endif // SDL_dos_h_
157
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