libuuid
UUID簡介
UUID含義是通用唯一識别碼(Universally Unique Identifier)，這 是一個軟體建構的标準，也是被開源軟體基金會 (Open Software Foundation, OSF) 的組織應用在分布式計算環境 (Distributed Computing Environment, DCE) 領域的一部分。
UUID是指在一台機器上生成的數字，它保證對在同一時空中的所有機器都是唯一的。通常平台會提供生成的API。按照開放軟體基金會(OSF)制定的标準計算，用到了以太網卡位址、納秒級時間、晶片ID碼和許多可能的數字
在linux下生成UUID可以使用libuuid的
uuid-generate
函數
安裝libuuid庫
libuuid
是一個跨平台的開源的uuid操作庫。一般的機器上預設是沒有，先安裝一下。
sudo apt-get install uuid-dev
安裝之後可以使用man uuid_generate來檢視一下使用方法
這裡先說一下uuid_t這個類型。可以找到uuid.h這個頭檔案，裡面有一行typedef unsigned char uuid_t[16];
#include <uuid.h>
void uuid_generate(uuid_t out);
void uuid_generate_random(uuid_t out);
void uuid_generate_time(uuid_t out);
int uuid_generate_time_safe(uuid_t out);
void uuid_generate_md5(uuid_t out, const uuid_t ns, const char *name, size_t
len);
void uuid_generate_sha1(uuid_t out, const uuid_t ns, const char *name, size_t
len);
在ubuntu上，libuuid的頭檔案在
/usr/include/uuid/uuid.h
，這個頭檔案很短，添加一些注釋如下：
/*
* Public include file for the UUID library
*
* Copyright (C) 1996, 1997, 1998 Theodore Ts'o.
*
* %Begin-Header%
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, and the entire permission notice in its entirety,
* including the disclaimer of warranties.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
* WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
* %End-Header%
*/
#ifndef _UUID_UUID_H
#define _UUID_UUID_H
#include <sys/types.h>
#ifndef _WIN32
#include <sys/time.h>
#endif
#include <time.h>
typedef unsigned char uuid_t[16];
/* UUID Variant definitions */
#define UUID_VARIANT_NCS 0
#define UUID_VARIANT_DCE 1
#define UUID_VARIANT_MICROSOFT 2
#define UUID_VARIANT_OTHER 3
#define UUID_VARIANT_SHIFT 5
#define UUID_VARIANT_MASK 0x7
/* UUID Type definitions */
#define UUID_TYPE_DCE_NIL 0
#define UUID_TYPE_DCE_TIME 1
#define UUID_TYPE_DCE_SECURITY 2
#define UUID_TYPE_DCE_MD5 3
#define UUID_TYPE_DCE_RANDOM 4
#define UUID_TYPE_DCE_SHA1 5
#define UUID_TYPE_SHIFT 4
#define UUID_TYPE_MASK 0xf
#define UUID_STR_LEN 37
/* Allow UUID constants to be defined */
#ifdef __GNUC__
#define UUID_DEFINE(name,u0,u1,u2,u3,u4,u5,u6,u7,u8,u9,u10,u11,u12,u13,u14,u15) \
static const uuid_t name __attribute__ ((unused)) = {u0,u1,u2,u3,u4,u5,u6,u7,u8,u9
9,u10,u11,u12,u13,u14,u15}
#else
#define UUID_DEFINE(name,u0,u1,u2,u3,u4,u5,u6,u7,u8,u9,u10,u11,u12,u13,u14,u15) \
static const uuid_t name = {u0,u1,u2,u3,u4,u5,u6,u7,u8,u9,u10,u11,u12,u13,u14,u15}
#endif
#ifdef __cplusplus
extern "C" {
#endif
/* clear.c */
// 清除uu内容(清零)
extern void uuid_clear(uuid_t uu);
/* compare.c */
// 比較兩個uuid
extern int uuid_compare(const uuid_t uu1, const uuid_t uu2);
/* copy.c */
// 拷貝src到dst
extern void uuid_copy(uuid_t dst, const uuid_t src);
/* gen_uuid.c */
// 生成一個uuid
extern void uuid_generate(uuid_t out);
extern void uuid_generate_random(uuid_t out);
extern void uuid_generate_time(uuid_t out);
extern int uuid_generate_time_safe(uuid_t out);
extern void uuid_generate_md5(uuid_t out, const uuid_t ns, const char *name, size_t len);
extern void uuid_generate_sha1(uuid_t out, const uuid_t ns, const char *name, size_t len);
/* isnull.c */
// 判斷uu是否為null
extern int uuid_is_null(const uuid_t uu);
/* parse.c */
// 解析in指向的字元串形式内容到uu
extern int uuid_parse(const char *in, uuid_t uu);
extern int uuid_parse_range(const char *in_start, const char *in_end, uuid_t uu);
/* unparse.c */
// 将uu内容解析為字元串，儲存到out數組
extern void uuid_unparse(const uuid_t uu, char *out);
extern void uuid_unparse_lower(const uuid_t uu, char *out);
extern void uuid_unparse_upper(const uuid_t uu, char *out);
/* uuid_time.c */
// 将基于時間建立的uu在的時間部分解析出來
extern time_t uuid_time(const uuid_t uu, struct timeval *ret_tv);
extern int uuid_type(const uuid_t uu);
extern int uuid_variant(const uuid_t uu);
/* predefined.c */
extern const uuid_t *uuid_get_template(const char *alias);
#ifdef __cplusplus
}
#endif
#endif /* _UUID_UUID_H */
實驗
代碼
#include <stdio.h>
#include <uuid/uuid.h>
// gcc uuid.c -luuid -o uuid
int main()
{
int i,n;
uuid_t uu[4];
char buf[1024];
struct timeval tv;
//1、
uuid_generate(uu[0]);
//2、
uuid_generate_random(uu[1]);
//3、
uuid_generate_time(uu[2]);
//4、
n = uuid_generate_time_safe(uu[3]);
printf("n = %d\n",n);
for(i=0;i<4;++i){
uuid_unparse(uu[i],buf);
printf("uu[%d]\t\t%s\n",i,buf);
}
uuid_time(uu[2],&tv);
printf("tv s:%lx u:%lx\n",tv.tv_sec,tv.tv_usec);
return 0;
}
實驗結果
gcc uuid.c -luuid -o test-uuid
./test-uuid
n = -1
uu[0] b885a97f-e54f-4b4f-a758-d9b98e405321
uu[1] 61f7ce91-009c-4df2-90c8-afd6e7f54c92
uu[2] d5533e2a-aae3-11ed-9fb4-00155daf56e4
uu[3] d5533e48-aae3-11ed-9fb4-00155daf56e4
tv s:63e8fb6f u:28611
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