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/*
* VBMouse - utility functions for DOS TSRs
* Copyright (C) 2022 Javier S. Pedro
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef DOSTSR_H
#define DOSTSR_H
#include <stdint.h>
#include "int21dos.h"
/** Deallocates the environment block from the passed PSP segment. */
static void deallocate_environment(segment_t psp)
{
// TODO : Too lazy to make PSP struct;
// 0x2C is offsetof the environment block field on the PSP
uint16_t __far *envblockP = (uint16_t __far *) MK_FP(psp, 0x2C);
dos_free(*envblockP);
*envblockP = 0;
}
/** Copies a program to another location.
* @param new_seg PSP segment for the new location
* @param old_seg PSP segment for the old location
* @param size size of the program to copy including PSP size. */
static void copy_program(segment_t new_seg, segment_t old_seg, unsigned size)
{
// The MCB is always 1 segment before.
uint8_t __far *new_mcb = MK_FP(new_seg - 1, 0);
uint8_t __far *old_mcb = MK_FP(old_seg - 1, 0);
uint16_t __far *new_mcb_owner = (uint16_t __far *) &new_mcb[1];
char __far *new_mcb_owner_name = &new_mcb[8];
char __far *old_mcb_owner_name = &old_mcb[8];
// Copy entire resident segment including PSP
_fmemcpy(MK_FP(new_seg, 0), MK_FP(old_seg, 0), size);
// Make the new MCB point to itself as owner
*new_mcb_owner = new_seg;
// Copy the program name, too.
_fmemcpy(new_mcb_owner_name, old_mcb_owner_name, 8);
}
/** Allocates a UMB of the given size.
* If no UMBs are available, this may still return a block in conventional memory. */
static __segment allocate_umb(unsigned size)
{
bool old_umb_link = dos_query_umb_link_state();
unsigned int old_strategy = dos_query_allocation_strategy();
segment_t new_segment;
dos_set_umb_link_state(true);
dos_set_allocation_strategy(DOS_FIT_BEST | DOS_FIT_HIGHONLY);
new_segment = dos_alloc(get_paragraphs(size));
dos_set_umb_link_state(old_umb_link);
dos_set_allocation_strategy(old_strategy);
return new_segment;
}
static __segment reallocate_to_umb(segment_t cur_seg, unsigned segment_size)
{
segment_t old_segment_psp = cur_seg - (DOS_PSP_SIZE/16);
segment_t new_segment_psp;
deallocate_environment(_psp);
// If we are already in UMA, don't bother
if (old_segment_psp >= 0xA000) {
return 0;
}
new_segment_psp = allocate_umb(segment_size);
if (new_segment_psp && new_segment_psp >= 0xA000) {
segment_t new_segment = new_segment_psp + (DOS_PSP_SIZE/16);
// Create a new program instance including PSP at the new_segment
copy_program(new_segment_psp, old_segment_psp, segment_size);
// Return the new segment
return new_segment;
} else {
if (new_segment_psp) {
// In case we got another low-memory segment...
dos_free(new_segment_psp);
}
return 0;
}
}
/** Called in case there is an error and we should free our HMA segment. */
static void cancel_reallocation(segment_t new_seg)
{
segment_t new_segment_psp = new_seg - (DOS_PSP_SIZE/16);
dos_free(new_segment_psp);
}
/** Called right before doing the TSR call.
* Frees the old code segment. */
static void finish_reallocation(segment_t old_segment_psp, segment_t new_seg)
{
segment_t new_segment_psp = new_seg - (DOS_PSP_SIZE/16);
// Tell DOS that we are "switching" to the new program in the HMA
dos_set_psp(new_segment_psp);
// We are about to free() the old code segment,
// which is likely where the currently running function code resides.
dos_free(old_segment_psp);
// Nothing should try to allocate memory between this and the actual TSR call,
// since it could overwrite the currently running code... !
}
#endif // DOSTSR_H
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