memory.inc

一个用纯汇编 写的操作系统 源代码 是用 TASM 编译器写的

; Assembly Editor core
; Copyright (c) 2001-2006, Tomasz Grysztar.
; All rights reserved.

init_editor_memory:
	mov	ecx,BLOCK_LENGTH
	call	get_memory
	or	eax,eax
	jz	memory_error
	mov	[editor_memory],eax
	mov	dword [eax],0
	mov	dword [eax+4],0
	lea	ebx,[eax+SEGMENT_LENGTH]
	mov	[unallocated_segments],ebx
	mov	[memory_search_segment],ebx
	add	eax,BLOCK_LENGTH
	mov	[unallocated_segments_end],eax
	mov	[memory_search_block],eax
	mov	[released_segments],0
	call	allocate_segment
	mov	[first_line],eax
	mov	[lines_count],1
	mov	[peak_line_length],0
	mov	[caret_line],eax
	mov	[caret_line_number],1
	mov	[window_line],eax
	mov	[window_line_number],1
	mov	edi,eax
	xor	eax,eax
	mov	ecx,SEGMENT_HEADER_LENGTH shr 2
	rep	stosd
	mov	eax,20202020h
	mov	ecx,SEGMENT_DATA_LENGTH shr 2
	rep	stosd
	call	allocate_segment
	jc	memory_shortage
	mov	[lengths_table],eax
	mov	edi,eax
	xor	eax,eax
	mov	ecx,SEGMENT_LENGTH shr 2
	rep	stosd
	mov	[caret_position],0
	mov	[window_position],0
	mov	[selection_line],0
	mov	[undo_data],0
	mov	[search_data],0
	mov	[editor_mode],0
	clc
	retn
    memory_error:
	stc
	retn

reset_editor_memory:
	mov	esi,[editor_memory]
	lea	eax,[esi+SEGMENT_LENGTH]
	mov	[unallocated_segments],eax
	mov	[memory_search_segment],eax
	lea	eax,[esi+BLOCK_LENGTH]
	mov	[unallocated_segments_end],eax
	mov	[memory_search_block],eax
	mov	[released_segments],0
    release_blocks:
	mov	ebx,[esi]
	or	ebx,ebx
	jz	release_done
	mov	eax,ebx
	call	release_memory
	mov	esi,ebx
	jmp	release_blocks
    release_done:
	mov	ebx,[editor_memory]
	xor	eax,eax
	mov	[ebx],eax
	mov	[undo_data],eax
	mov	[search_data],eax
	call	allocate_segment
	jc	memory_shortage
	mov	[first_line],eax
	mov	[window_line],eax
	mov	[caret_line],eax
	mov	edi,eax
	xor	eax,eax
	mov	ecx,SEGMENT_HEADER_LENGTH shr 2
	rep	stosd
	mov	eax,20202020h
	mov	ecx,SEGMENT_DATA_LENGTH shr 2
	rep	stosd
	xor	eax,eax
	mov	[selection_line],eax
	mov	[peak_line_length],eax
	mov	[window_position],eax
	inc	eax
	mov	[window_line_number],eax
	mov	[caret_line_number],eax
	mov	[lines_count],eax
	call	allocate_segment
	jc	memory_shortage
	mov	[lengths_table],eax
	mov	edi,eax
	xor	eax,eax
	mov	ecx,SEGMENT_LENGTH shr 2
	rep	stosd
	retn

release_editor_memory:
	mov	esi,[editor_memory]
    release:
	mov	ebx,[esi]
	mov	eax,esi
	call	release_memory
	mov	esi,ebx
	or	esi,esi
	jnz	release
	mov	[editor_memory],0
	retn

allocate_segment:
	mov	eax,[unallocated_segments]
	cmp	eax,[unallocated_segments_end]
	je	simple_allocation_failed
	add	[unallocated_segments],SEGMENT_LENGTH
	clc
	retn
    simple_allocation_failed:
	push	ebx esi
	mov	ebx,[memory_search_block]
	mov	esi,[memory_search_segment]
	cmp	[released_segments],16
	jb	add_new_block
    find_free_segment:
	cmp	esi,ebx
	je	find_in_next_block
	cmp	dword [esi],-1
	je	reuse_segment
	add	esi,SEGMENT_LENGTH
	cmp	esi,[memory_search_segment]
	jne	find_free_segment
    add_new_block:
	sub	ebx,BLOCK_LENGTH
    find_last_memory_block:
	cmp	dword [ebx],0
	je	allocate_more_memory
	mov	ebx,[ebx]
	jmp	find_last_memory_block
    allocate_more_memory:
	mov	ecx,BLOCK_LENGTH
	call	get_memory
	or	eax,eax
	jz	allocation_failed
	mov	[ebx],eax
	mov	[eax],dword 0
	mov	[eax+4],ebx
	lea	ebx,[eax+BLOCK_LENGTH]
	mov	[unallocated_segments_end],ebx
	add	eax,SEGMENT_LENGTH
	lea	ebx,[eax+SEGMENT_LENGTH]
	mov	[unallocated_segments],ebx
	mov	[released_segments],0
	pop	esi ebx
	clc
	retn
    allocation_failed:
	pop	esi ebx
	stc
	retn
    reuse_segment:
	mov	eax,esi
	mov	[memory_search_block],ebx
	add	esi,SEGMENT_LENGTH
	mov	[memory_search_segment],esi
	dec	[released_segments]
	pop	esi ebx
	clc
	retn
    find_in_next_block:
	sub	ebx,BLOCK_LENGTH
	mov	esi,[ebx]
	lea	ebx,[esi+BLOCK_LENGTH]
	or	esi,esi
	jnz	find_free_segment
	mov	ebx,[editor_memory]
	mov	esi,ebx
	add	ebx,BLOCK_LENGTH
	jmp	find_free_segment

memory_shortage:
	call	undo_changes
	jmp	not_enough_memory