【代码检视】未使用已经写好的结构体

代码文件：archive_read_support_format_mtree.rs
问题代码函数：parse_digest
未使用已经写好的结构体
重构前

	switch (type) {
	case ARCHIVE_ENTRY_DIGEST_MD5:
		len = sizeof(entry->digest.md5);
		break;
	case ARCHIVE_ENTRY_DIGEST_RMD160:
		len = sizeof(entry->digest.rmd160);
		break;
	case ARCHIVE_ENTRY_DIGEST_SHA1:
		len = sizeof(entry->digest.sha1);
		break;
	case ARCHIVE_ENTRY_DIGEST_SHA256:
		len = sizeof(entry->digest.sha256);
		break;
	case ARCHIVE_ENTRY_DIGEST_SHA384:
		len = sizeof(entry->digest.sha384);
		break;
	case ARCHIVE_ENTRY_DIGEST_SHA512:
		len = sizeof(entry->digest.sha512);
		break;

重构后

    match type_0 {
        1 => len = size_of::<[u8; 16]>() as u64,
        2 => len = size_of::<[u8; 20]>() as u64,
        3 => len = size_of::<[u8; 20]>() as u64,
        4 => len = size_of::<[u8; 32]>() as u64,
        5 => len = size_of::<[u8; 48]>() as u64,
        6 => len = size_of::<[u8; 64]>() as u64,
        _ => {
            archive_set_error_safe!(
                &mut a_safe.archive as *mut archive,
                ARCHIVE_MTREE_DEFINED_PARAM.archive_errno_programmer,
                b"Internal error: Unknown digest type\x00" as *const u8
            );
            return ARCHIVE_MTREE_DEFINED_PARAM.archive_fatal;
        }
    }

重构后的len中没有使用entry->digest.sha256类似方式取值，而是重新定义了一遍，结构体archive_entry、ae_digest均已重构，建议使用重构前的方式实现；原代码中的定义的宏均未体现，难以理解123456所代表的含义

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类似这种情况很多，建议C代码中涉及到struct的都仔细排查下。。
例如archive_read_support_format_lha.rs中的archive_read_format_lha_read_header函数
重构前

	struct archive_wstring linkname;
	struct archive_wstring pathname;
	struct lha *lha;
	const unsigned char *p;
	const char *signature;
	int err;
	struct archive_mstring conv_buffer;
	const wchar_t *conv_buffer_p;

重构后

    let mut linkname: archive_wstring = archive_wstring {
        s: 0 as *mut wchar_t,
        length: 0,
        buffer_length: 0,
    };
    let mut pathname: archive_wstring = archive_wstring {
        s: 0 as *mut wchar_t,
        length: 0,
        buffer_length: 0,
    };
    let safe_a = unsafe { &mut *a };
    let mut p: *const u8 = 0 as *const u8;
    let mut signature: *const u8 = 0 as *const u8;
    let mut err: i32 = 0;
    let mut conv_buffer: archive_mstring = archive_mstring {
        aes_mbs: archive_string {
            s: 0 as *mut u8,
            length: 0,
            buffer_length: 0,
        },
        aes_utf8: archive_string {
            s: 0 as *mut u8,
            length: 0,
            buffer_length: 0,
        },
        aes_wcs: archive_wstring {
            s: 0 as *mut wchar_t,
            length: 0,
            buffer_length: 0,
        },
        aes_mbs_in_locale: archive_string {
            s: 0 as *mut u8,
            length: 0,
            buffer_length: 0,
        },
        aes_set: 0,
    };