文件分割工具C++代码

实现如下功能：
1.读取参数
-s source.dat：指定待分割的文件名称；
-d dest：指定分割后的文件模板名称，其文件将以dest0001.dat,dest0002.dat.....的方式进行命名
-n size:指定分割后的文件大小
2.用法
./split_file -s source.dat -d dest -n 10485760
以10M为单位进行文件分割
3.缺省参数
默认的源文件为source.dat
默认的分割文件模板名称为dest
默认的文件分割大小为1M(1048576Bytes)
./split_file -n 10485760
与.2中的命令执行的结果一直
以下为C++源码：

#include
#include
#include
#include

#define MAX_PATH 260

/**
 * -s:source file
 *  -d:destination file template
 *  -n:size of destination file
 */
int main(int argc,char**argv)
{
    int opt = 0;
    char* optstr = NULL;

    char* program_name = argv[0];
    char* p = strchr(program_name,'.');
    if(p == NULL)
    {
    }
    else
    {
        *p = 0;
    }
   
    char source_file[MAX_PATH] = {0};
    char dest_file[MAX_PATH] = {0};

    unsigned long file_size = 1024*1024;//1M
    unsigned long FILE_SIZE = file_size;

    //the default source file name is the same as program name but ext
    //the destination file name is the same as program name but ext.
    snprintf(source_file,MAX_PATH,"%s.src",program_name);
    snprintf(dest_file,MAX_PATH,"%s.dst",program_name);

    while((opt = getopt(argc,argv,"s:d:n:")) != -1)
    {
        switch(opt)
        {
            case 's':
                snprintf(source_file,MAX_PATH,"%s",optarg);
                break;
            case 'd':
                snprintf(dest_file,MAX_PATH,"%s.part",optarg);
                break;
            case 'n':
                file_size = atol(optarg);
                FILE_SIZE = file_size;
                break;
            default:
                printf("invalid options!\n");
        }

    }
   
    FILE* src_file = fopen(source_file,"rb");
    if(src_file == NULL)
    {
        printf("open %s file error!\n",source_file);
        return -1;
    }
   
    char* data_block = new char[file_size];
    FILE* dst_file = NULL;
    char split_file[MAX_PATH];
    unsigned int count = 0;

    //write the same size file
    while((file_size = fread(data_block,1,FILE_SIZE,src_file)) == FILE_SIZE)
    {
        snprintf(split_file,MAX_PATH,"%s%04d",dest_file,count++);
        dst_file = fopen(split_file,"wb");
        if(dst_file == NULL)
        {
            printf("open %s error!\n");
            return -1;
        }
        fwrite(data_block,1,file_size,dst_file);
        fclose(dst_file);
    }

    //write the last block data
    snprintf(split_file,MAX_PATH,"%s%04d",dest_file,count);
    dst_file = fopen(split_file,"wb");
    if(dst_file == NULL)
    {
        printf("open %s error!\n");
        return -1;
    }
    fwrite(data_block,1,file_size,dst_file);
    fclose(dst_file);

    delete[] data_block;
    //close the source file
    fclose(src_file);


    return 0;
}