80 lines
3.0 KiB
NASM
80 lines
3.0 KiB
NASM
[SECTION .text]
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[BITS 32]
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DEFAULT_COLOR equ 0f00h
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global kprintf
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;===============================================
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; void kprintf(u16 disp_pos, const char *format, ...)
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; 参数说明：
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; disp_pos: 开始打印的位置，0为0行0列，1为0行1列，80位1行0列
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; format: 需要格式化输出的字符串，默认输出的字符颜色为黑底白字
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; %c: 输出下一个参数的字符信息（保证参数范围在0~127），输出完打印的位置往下移动一位
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; %b: 更改之后输出的字符的背景色（保证参数范围在0~15）
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; %f: 更改之后输出的字符的前景色（保证参数范围在0~15）
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; %s(提高内容): 参考inc/terminal.h，传进来的是一个结构体，结构体参数足够明确不复赘述，
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; 输出是独立的，输出完打印的位置不会往下移动一位，不会影响接下来%c的输出的颜色
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; 其余字符：按照字符输出（保证字符里不会有%，\n等奇奇怪怪的字符，都是常见字符，%后面必会跟上述三个参数之一），输出完打印的位置往下移动一位
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kprintf:
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; jmp $
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push ebp
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mov ebp, esp
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push edi
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push esi
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push ebx ; %ebp, %ebx, %edi, %esi, %esp are callee saved regs
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mov esi, 0 ; string offset
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mov edi, [ebp + 8] ; disp_pos, stack always word aligned
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mov ebx, [ebp + 12] ; format base
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mov edx, 4 ; offset from ebp of the first va_list
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mov ecx, DEFAULT_COLOR ; color
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xor eax, eax ; clear eax
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.loop:
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movzx eax, byte [ebx + esi] ; fetch a char into eax
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inc esi ;
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cmp al, 0
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je .exit ; if reaches \0, then break
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cmp al, '%'
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jne .normal_print
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movzx eax, byte [ebx + esi]
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inc esi ; handle special format
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cmp al, 'c'
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je .fmt_c
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cmp al, 'b'
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je .fmt_b
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cmp al, 'f'
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je .fmt_f
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dec esi ; fall back to normal print
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movzx eax, byte [ebx + esi]
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jmp .normal_print
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.fmt_c:
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mov eax, [ebp + edx * 4] ; fetch va into eax, here its a byte of character
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inc edx ; align to 4bytes, maybe
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jmp .normal_print
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.fmt_b:
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mov eax, [ebp + edx * 4]
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inc edx
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and cx, 00F00H ; clear background color(and keep foreground)
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shl ax, 12
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or cx, ax
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jmp .loop ; not a printable option
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.fmt_f:
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mov eax, [ebp + edx * 4]
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inc edx
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and cx, 0F000H ; clear foreground color(and keep backgroung)
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shl ax, 8
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or cx, ax
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jmp .loop ; not a printable option
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.normal_print:
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or ax, cx ; combine character and color
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mov word[gs:edi * 2], ax; load to dest video mem, edi as the cursor
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inc edi ; cursor ++
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jmp .loop ; it is a while loop
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.exit:
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pop ebx
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pop edi
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pop esi
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leave
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ret
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jmp $ |