学 Win32 汇编[34] - 宏汇编(1)

从接触 C 语言时, 我就不大喜欢宏; 但为了看懂别人的代码也不得不去了解.

宏可定义在源程序的任意位置, 但一般放在 .data 前面.
有些简单的宏可以用 equ、textequ 或 = 来代替, 但宏有更复杂的功能.

"宏" 的本质是 "替换", 但又像极了 "子过程";
所以即有宏过程(macro procedure)、也有宏函数(macro function).
它既以有参数(可以是: 常数、变量、寄存器、指令、表达式), 有时也需要像子过程一样声明.
宏可以指定哪些参数是必须的, 还可以给参数默认值.

宏可以包含数据(.data)和代码(.code)、还可以嵌套.
宏中的注释使用 ;; 如果只用 ; 将会被一起替换到代码中.

宏的功能很强大, 现在常用的 PrintDec、PrintHex、PrintString、PrintText 等等都是宏.
再强大它也只是 "文本替换".

"宏" 和 "子程序" 相比:
1、宏展开后顺序执行, 不像调用子程序跳来跳去, 这样程序会更 "快";
2、宏展开后会让代码量增大, 导致程序变 "大".

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一个简单的宏:

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; Test34_1.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

;定义一个 mExit 宏
mExit macro
    PrintLine
    ret
endm

.code
sum proc v1, v2, v3
    mov eax, v1
    add eax, v2
    add eax, v3
    ret
sum endp
;
main proc
    invoke sum, , ,
    PrintDec eax ;66
    ;PrintLine
    ;ret
    mExit ;mExit 将被替换为上面两行代码
main endp
end main

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一个代替求和函数的宏:

---

; Test34_2.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

mSum macro v1, v2, v3
    mov eax, v1
    add eax, v2
    add eax, v3
endm

.code
main proc
    mSum , ,
    PrintDec eax ;66
    PrintLine
    mSum , , , ,  ;多余的参数会被忽略
    PrintDec eax ;66
    PrintLine
    ret
main endp
end main

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宏参数的默认值:

---

; Test34_3.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

;参数 v1、v2 通过 REQ 标识说明是必备参数
;参数 v3、v4 给出了默认值
mSum macro v1:req, v2:req, v3:=<>, v4:=<>
    mov eax, v1
    add eax, v2
    add eax, v3
    add eax, v4
endm

.code
main proc
    mSum ,
    PrintDec eax ;110
    PrintLine
    ret
main endp
end main

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EXITM: 退出宏

---

; Test34_4.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

mPrint macro
    PrintText '第一行'
    PrintText '第二行'
    exitm
    PrintText '第三行'
endm

.code
main proc
    mPrint ;只会输出前两行
    ret
main endp
end main

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PURGE: 取消宏

---

; Test34_5.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

mPrint macro
    PrintText '第一行'
    PrintText '第二行'
    PrintText '第三行'
    PrintLine
endm

.code
main proc
    mPrint
    mPrint
    purge mPrint ;可用逗号隔开取消多个宏
    mPrint       ;这个宏不会展开了
    ret
main endp
end main

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宏中 local 的使用:

---

; Test34_6.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

;从三个数中求最大数的宏
mMax macro v1, v2, v3
    LOCAL L1, L2 ;;如没有这句, 宏在多次展开时会让 L1、L2 重名, 这样宏会把标号名称协调好
    mov eax, v1
    cmp eax, v2
    jge L1
    mov eax, v2
L1: cmp eax, v3
    jge L2
    mov eax, v3
L2:
endm

.code
main proc
    mMax , ,
    PrintDec eax  ;33
    ret
main endp
end main

---

灵活的参数, 用到 & 操作符:

---

; Test34_7.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

;求最数中的最大值:
mMax macro v1, v2
    LOCAL L1
    mov eax, v1
    cmp eax, v2
    jge L1
    mov eax, v2
L1:
endm

;求最数中的最小值:
mMin macro v1, v2
    LOCAL L1
    mov eax, v1
    cmp eax, v2
    jle L1
    mov eax, v2
L1:
endm

;能把 JGE 或 JLE 做参数:
mCom1 macro XX, v1, v2
    LOCAL L1
    mov eax, v1
    cmp eax, v2
    XX L1
    mov eax, v2
L1:
endm

;能通过参数让 J*E 变为 JGE 或 JLE:
mCom2 macro X, v1, v2
    LOCAL L1
    mov eax, v1
    cmp eax, v2
    J&X&E L1    ;;这里用到特殊操作符 &
    mov eax, v2
L1:
endm

.code
main proc
    mMax ,
    PrintDec eax ;22
 
    mMin ,
    PrintDec eax ;11
 
    mCom1 JGE, ,
    PrintDec eax ;22
 
    mCom1 JLE, ,
    PrintDec eax ;11
 
    mCom2 G, ,
    PrintDec eax ;22
 
    mCom2 L, ,
    PrintDec eax ;11
    ret
main endp
end main

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特殊操作符: &、<>、%、!

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&  ;替换操作符
<> ;字符串传递操作符
%  ;表达式操作符, 也用于得到一个变量或常量的值
!  ;转义操作符

---

; Test34_8.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

;自定义的宏
mPrint macro Text
    PrintText '* &Text& *'
endm

.code
main proc
    ;该宏会把参数直接替换过去
    mPrint     ;* 1234 *
 
    ;要保证参数的完整应该使用 <>
    mPrint ,   ;* 12 *
    mPrint <,> ;* 12,34 *
 
    ;需要计算结果应该使用 %()
    mPrint +   ;* 34+12 *
    mPrint %(+)   ;* 46 *
 
    ;用到 &、<、>、%、! 应该使用 ! 转义
    mPrint  !%  = %(/)!! ;* 10 % 2 = 5! *
    ret
main endp
end main

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