argz_extract()函数，argz_stringify()函数

摘要: argz_extract()函数是把一个argz vector转成标准的main第二个参数argv；
argz_stringify()函数是把一个argz vector转成正常的字符串。

函数分别位于glibc源码中的../glibc-version/string/argz-extract.c和../glibc-version/string/argz-stringify.c中。
函数声明如下：

// argz.h

/* Puts pointers to each string in ARGZ into ARGV, which must be large enough
to hold them all.  */
extern void __argz_extract (__const char *__restrict __argz, size_t __len,
char **__restrict __argv) __THROW;
extern void argz_extract (__const char *__restrict __argz, size_t __len,
char **__restrict __argv) __THROW;

/* Make '\0' separated arg vector ARGZ printable by converting all the '\0's
except the last into the character SEP.  */
extern void __argz_stringify (char *__argz, size_t __len, int __sep) __THROW;
extern void argz_stringify (char *__argz, size_t __len, int __sep) __THROW;

argz_extract()函数是将argz vector中的元素转存到argv中，以此实现一维到二维的转换。注意，argv最后要有一个元素为NULL，以"this is a test"为例，转换结果如下图：



argz_stringify()函数是将argz vecotr变成一个正常的字符串，以给定的delim字符去替换argz vector中的\0，在上例中假如再给定字符','那么得到的结果如下图：



函数的实现如下：

/* Puts pointers to each string in ARGZ, plus a terminating 0 element, into
ARGV, which must be large enough to hold them all.  */
void
__argz_extract (const char *argz, size_t len, char **argv)
{
while (len > 0)
{
size_t part_len = strlen (argz);
*argv++ = (char *) argz;
argz += part_len + 1;
len -= part_len + 1;
}
*argv = 0;
}
weak_alias (__argz_extract, argz_extract)

/* Make '\0' separated arg vector ARGZ printable by converting all the '\0's
except the last into the character SEP.  */
void
__argz_stringify (char *argz, size_t len, int sep)
{
if (len > 0)
while (1)
{
size_t part_len = __strnlen (argz, len);
argz += part_len;
len -= part_len;
if (len-- <= 1)  /* includes final '\0' we want to stop at */
break;
*argz++ = sep;
}
}
libc_hidden_def (__argz_stringify)
weak_alias (__argz_stringify, argz_stringify)