busybox分析--5.getopt32

一.busybox中的getopt32
1. 说明
 a. 当命令行中调用./_install/busybox arping -I eth2  -s 192.168.4.68 192.168.4.1
参数: -I eth2  -s 192.168.4.68 192.168.4.1
参数字符串:  "DUAqfbc:w:I:s:"
 b. opt = getopt32(argv, "DUAqfbc:w:I:s:", &count, &str_timeout, &device, &source);
        dbmsg("count=%d,str_timeout=%s,device=%s,source=%s",count,str_timeout, device,source);
关于getopt32,假设命令如下:
sudo  ./_install/busybox arping -I eth2  -s 192.168.4.68 192.168.4.1 -w 10 -f
count=-1,str_timeout=10,device=eth2,source=192.168.4.68
调用了getopt32之后，为什么count, str_timeout, device, source就会各自保存正确的参数呢？
2.代码

uint32_t FAST_FUNC
getopt32(char **argv, const char *applet_opts, ...)
{
    int argc;
    unsigned flags = 0;
    unsigned requires = 0;
    t_complementary complementary[33]; /* last stays zero-filled */
    char first_char;
    int c;
    const unsigned char *s;
    t_complementary *on_off;
    va_list p;
    const struct option *l_o;
    struct option *long_options = (struct option *) &bb_null_long_options;
    unsigned trigger;
    char **pargv;
    int min_arg = 0;
    int max_arg = -1;

#define SHOW_USAGE_IF_ERROR     1
#define ALL_ARGV_IS_OPTS        2
#define FIRST_ARGV_IS_OPT       4

    int spec_flgs = 0;

    //a.统计命令行中参数的个数
    argc = 1;
    while (argv[argc])
        argc++;

    va_start(p, applet_opts);

    c = 0;
    on_off = complementary;
    memset(on_off, 0, sizeof(complementary));

    /* skip bbox extension */
    first_char = applet_opts[0];
    if (first_char == '!')
        applet_opts++;

    //s指向参数字符串"DUAqfbc:w:I:s:"中的首地址D
    s = (const unsigned char *)applet_opts;  //跳过首地址是+或-的字符
    if (*s == '+' || *s == '-')
        s++;
    //b.解析参数字符串"DUAqfbc:w:I:s:"
    //将参数存在opt_char中,switch_on的每一位代表一个参数
    while (*s) {
        if (c >= 32)
            break;
        on_off->opt_char = *s;
        on_off->switch_on = (1 << c);
        if (*++s == ':') {                         //遇到:说明后面需要带一个参数
            on_off->optarg = va_arg(p, void **);   //用on_off指向参数字符串
            while (*++s == ':')
                continue;
        }
        on_off++;
        c++;
    }
    //因为没有在arping.c中设定applet_long_options,所以applet_long_options=NULL
    if (applet_long_options) {
        ... //此处跳过
    }

    for (s = (const unsigned char *)opt_complementary; s && *s; s++) {
        //解析可选参数，看了半天没看明白，放弃了
    }
    opt_complementary = NULL;
    va_end(p);

    optind = 0;
    while ((c = getopt(argc, argv, applet_opts)) != -1) {
        c &= 0xff; /* fight libc's sign extension */
        for (on_off = complementary; on_off->opt_char != c; on_off++) {
            if (on_off->opt_char == '\0' ) {
                goto error;
            }
        }
        if (flags & on_off->incongruously)
            goto error;
        trigger = on_off->switch_on & on_off->switch_off;
        flags &= ~(on_off->switch_off ^ trigger);
        flags |= on_off->switch_on ^ trigger;
        flags ^= trigger;
        if (on_off->counter)
            (*(on_off->counter))++;
        if (optarg) {
            if (on_off->param_type == PARAM_LIST) {
                llist_add_to_end((llist_t **)(on_off->optarg), optarg);
            } else if (on_off->param_type == PARAM_INT) {
                *(unsigned*)(on_off->optarg) = xatoi_positive(optarg);
            } else if (on_off->optarg) {                //都是string类型，就把optarg赋给on_off->optarg就是了
                *(char **)(on_off->optarg) = optarg;
            }
        }
    }

    /* check depending requires for given options */
    for (on_off = complementary; on_off->opt_char; on_off++) {
        if (on_off->requires
         && (flags & on_off->switch_on)
         && (flags & on_off->requires) == 0
        ) {
            goto error;
        }
    }
    if (requires && (flags & requires) == 0)
        goto error;
    argc -= optind;
    if (argc < min_arg || (max_arg >= 0 && argc > max_arg))
        goto error;

    option_mask32 = flags;
    return flags;

 error:
    if (first_char != '!')
        bb_show_usage();
    return (int32_t)-1;
}

3.

typedef struct {
    unsigned char opt_char;
    smallint param_type;
    unsigned switch_on;
    unsigned switch_off;
    unsigned incongruously;
    unsigned requires;
    void **optarg;
    int *counter;
} t_complementary;

全局结构体complementary数组complementary[33];
其中每个opt_char指向参数字符串中的一个参数:即每一个指向 D  U A q f b c w I s中的一个
其中每个switch_on: D(1<<0)   U(1<<1)  A(1<<2)

"DUAqfbc:w:I:s:"
opt_complementary = "=1:Df:AU:c+";
解析opt_complementary
a. 跳过其中的:
b. 检查参数中的 ? - = 这三个符号后面必须跟个数字
c.
opt = getopt32(argv, "DUAqfbc:w:I:s:", &count, &str_timeout, &device, &source);
这儿知道意思了，不看了，就这样了！写点代码验证一下得了，不看了！

---

二. 简短点
2.1 自己写个demo

#include <unistd.h>
#include <stdarg.h>
int getopt32(int argc, char** argv, char* opts, ...)
{
    int i=0, ret;
    va_list p;
    char *s;
    void **my_arg[1024];

    va_start(p, opts);

    s=opts; //s
    while(*s++)
    {
        if(*s != ':')
            continue;
        //找到两个参数cc与buf的地址，保存到my_arg数组中
        my_arg[i++] = va_arg(p, void**);
    }

    i=0;
    while((ret=getopt(argc, argv, opts)) != -1)
    {
        if(optarg == NULL)
            continue;
        dbmsg("optarg=%s, strlen(optarg)=%d", optarg, strlen(optarg));
        //*(char **)(my_arg)[i] = optarg;
        memcpy((char **)(my_arg)[i], optarg, strlen(optarg));   //将从命令行传来的参数解析，并写到c与buf中
        dbmsg("addr=0x%x", (char **)(my_arg)[i]);
        dbmsg("%s", (char **)(my_arg)[i]);
        i++;
    }
}

int main ( int argc, char *argv[] )
{
    char c[1024];
    char buf[1024];
    dbmsg("addr c=0x%x,buf=0x%x", c, buf);   //打印一下c与buf的地址
    getopt32(argc, argv, "hc:s:", c, buf);
    dbmsg("c=%s,buf=%s", c, buf);            //打印c与buf的结果
    return EXIT_SUCCESS;
}

现在这个原理就很明显了:
    a. 找到可变参数的地址
    b. 解析DUAqfbc:w:I:s:字符串,遇到:

2.2 运行结果:

cong@msi:/work/test/busytest/1varg$ ./varg -s 1 -c 2
varg.c:main[40]: addr c=0x5439390,s=0x5439790
varg.c:getopt32[27]: optarg=1, strlen(optarg)=1
varg.c:getopt32[30]: addr=0x5439390
varg.c:getopt32[31]: 1
varg.c:getopt32[27]: optarg=2, strlen(optarg)=1
varg.c:getopt32[30]: addr=0x5439790
varg.c:getopt32[31]: 2
varg.c:main[42]: c=1,s=2  //正确

cong@msi:/work/test/busytest/1varg$ ./varg -s 1
varg.c:main[40]: addr c=0x39c4ec70,s=0x39c4f070
varg.c:getopt32[27]: optarg=1, strlen(optarg)=1
varg.c:getopt32[30]: addr=0x39c4ec70
varg.c:getopt32[31]: 1
varg.c:main[42]: c=1,s=       //不正确//这儿有个bug

cong@msi:/work/test/busytest/1varg$ ./varg -c 2
varg.c:main[40]: addr c=0x8fcdb0e0,s=0x8fcdb4e0
varg.c:getopt32[27]: optarg=2, strlen(optarg)=1
varg.c:getopt32[30]: addr=0x8fcdb0e0
varg.c:getopt32[31]: 2
varg.c:main[42]: c=2,s=     //正确

这儿有个bug:不能区分参数，总是把第1个参数放在c中
所以对于 hc:s:，不提供c参数只提供s参数时,会有问题:将s的参数赋给了c,这样是不对的

2.3 代码
1varg.rar (下载后改名为1varg.tar.gz)

---

三. 改进
3.1改进后的代码

#include "utils.h"
#include <unistd.h>
#include <stdarg.h>
int getopt32(int argc, char** argv, char* opts, ...)
{
    int i=0, ret,len=0;    //len-->带:的参数的个数
    va_list p;
    char *s;
    void **my_arg[1024];
    char opt_char[1024];

    va_start(p, opts);

    s=opts; //s
    while(*s++)
    {
        if(*s != ':')
            continue;
        //get args addr
        my_arg[len] = va_arg(p, void**);      //获取c与s的地址,即传给getopt32的可变参数的地址
        opt_char[len] = *(s-1);               //保存"hc:s:"中的c与s
        len++;
    }

    while((ret=getopt(argc, argv, opts)) != -1)
    {
        if(optarg == NULL)
            continue;
        dbmsg("ret=%c,optarg=%s, strlen(optarg)=%d",ret, optarg, strlen(optarg));
        for(i=0; i<len; i++)
        {
            if(opt_char[i] == ret)     //比较<"hc:s:"中的c与s>与ret是否相同
            {
                //*(char **)(my_arg)[i] = optarg;
                memcpy((char **)(my_arg)[i], optarg, strlen(optarg));
                dbmsg("addr=0x%x", (char **)(my_arg)[i]);
                dbmsg("%s", (char **)(my_arg)[i]);
            }
        }
    }
}

int main ( int argc, char *argv[] )
{
    char c[1024];
    char s[1024];
    dbmsg("addr c=0x%x,s=0x%x", c, s);
    getopt32(argc, argv, "hc:s:", c, s);
    dbmsg("c=%s,s=%s", c, s);
    return EXIT_SUCCESS;
}

这个地方太不好说明了,都叫参数，没法区分，直接看代码吧！
3.2结果

cong@msi:/work/test/busytest/2varg$ ./varg -s 1 -c 2
varg.c:main[48]: addr c=0x59df07a0,s=0x59df0ba0
varg.c:getopt32[29]: ret=s,optarg=1, strlen(optarg)=1
varg.c:getopt32[37]: addr=0x59df0ba0
varg.c:getopt32[38]: 1
varg.c:getopt32[29]: ret=c,optarg=2, strlen(optarg)=1
varg.c:getopt32[37]: addr=0x59df07a0
varg.c:getopt32[38]: 2
varg.c:main[50]: c=2,s=1      //正确

cong@msi:/work/test/busytest/2varg$ ./varg -s 1
varg.c:main[48]: addr c=0x34bba3a0,s=0x34bba7a0
varg.c:getopt32[29]: ret=s,optarg=1, strlen(optarg)=1
varg.c:getopt32[37]: addr=0x34bba7a0
varg.c:getopt32[38]: 1
varg.c:main[50]: c=,s=1        //正确

cong@msi:/work/test/busytest/2varg$ ./varg -c 2
varg.c:main[48]: addr c=0xa3100400,s=0xa3100800
varg.c:getopt32[29]: ret=c,optarg=2, strlen(optarg)=1
varg.c:getopt32[37]: addr=0xa3100400
varg.c:getopt32[38]: 2
varg.c:main[50]: c=2,s=        //正确

3.3 代码
2varg.rar (下载后改名为2varg.tar.gz)