简单的BSON OID生成实现

简单的OID生成测试实现，只是简单的用用，切勿用于生产环境。

/* 应该使用大端序的，这里没有做转换

 * ObjectId是12-byte BSON类型,其结构为:

 *

 *  4-byte 值为Unix时间戳,

 *  3-byte 主机标识,

 *  2-byte 进程ID

 *  3-byte 计数值

 */

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

#ifdef _WIN32

#include <process.h>

#include <Windows.h>

#else

#include <unistd.h>

#include <sys/utsname.h>

#endif

/* 全局的主机标识(这个值可采用主机名散列得到) */

static unsigned char host[4] = {0,0,0,0};

/* 全局计数器(进程一个，要避免访问冲突,当前没有考虑) */

static int counter = 0;

/* 进程ID值 */

static unsigned short pid = 0;

// 简单的将主机名进行散列

void hashhostname(const char* hostname)

{

	host[0] = 0x41;

	host[1] = 0xC6;

	host[2] = 0x4E;

	while(*hostname){

		unsigned char v = *(hostname++);

		host[0] += v >> 2;

		host[1] += v >> 3;

		host[2] += v >> 4;

	}

}

void create_oid()

{

	time_t t = time(NULL);

	unsigned char oid[12];

	*((int*)oid) = (int)t;

	oid[4] = host[0];

	oid[5] = host[1];

	oid[6] = host[2];

	oid[7] = pid;

	oid[8] = pid >> 8;

	oid[9] = counter;

	oid[10] = counter >> 8;

	oid[11] = counter >> 16;

	// 输出

	++counter;

	counter &= 0xffffff;

	int i=0;

	while(i<12){

		printf("%02X",oid[i++]);

	}

	putchar('\n');

}

int main()

{

	// 1、初始化主机标识和进程ID

#ifdef _WIN32

	char buffer[512];

	DWORD buflen = 512;

	GetComputerNameA((LPSTR)buffer,&buflen);

	buffer[511] = '\0';

	puts(buffer);

	hashhostname(buffer);

	pid = (unsigned short)_getpid();

#else

	struct utsname utn;

	if(uname(&utn) < 0 ){

		perror("uname");

		return 0;

	}else{

		printf(" sysname:%s\n nodename:%s\n release:%s\n version:%s\n machine:%s\n \n",

					utn.sysname,

					utn.nodename,

					utn.release,

					utn.version,

					utn.machine);

		hashhostname(utn.nodename);

	}

	pid = (unsigned short)getpid();

#endif

	puts("-----------------------");

	printf(" host=[%hhx,%hhx,%hhx]\n",host[0],host[1],host[2]);

	printf(" pid = %hx\n",pid);

	puts("-----------------------");

	counter = 0xfffffe;

	create_oid();

	create_oid();

	create_oid();

	create_oid();

	return 0;

}