1 files changed, 116 insertions, 0 deletions
diff --git a/dostsr.h b/dostsr.h
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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 __far * cur_seg, unsigned segment_size)
+{
+	segment_t old_psp_segment = *cur_seg - (DOS_PSP_SIZE/16);
+	segment_t new_psp_segment;
+
+	deallocate_environment(_psp);
+
+	// If we are already in UMA, don't bother
+	if (old_psp_segment >= 0xA000) {
+		return 0;
+	}
+
+	new_psp_segment = allocate_umb(segment_size);
+
+	if (new_psp_segment && new_psp_segment >= 0xA000) {
+		segment_t new_segment = new_psp_segment + (DOS_PSP_SIZE/16);
+		printf("Moving to upper memory\n");
+
+		// Create a new program instance including PSP at the new_segment
+		copy_program(new_psp_segment, old_psp_segment, segment_size);
+
+		// Tell DOS to "switch" to the new program
+		dos_set_psp(new_psp_segment);
+
+		// Return the new segment
+		return new_segment;
+	} else {
+		printf("No upper memory available\n");
+		if (new_psp_segment) {
+			// In case we got another low-memory segment...
+			dos_free(new_psp_segment);
+		}
+
+		return 0;
+	}
+}
+
+#endif // DOSTSR_H