C语言函数指针：获得任意类型数组的最大

#include <stdio.h>
 
//{3,5,8,7,6}
/*
int max(int *nums,int len)
{
    int i;
    int max=nums[0];//假定第0个元素为最大值
    for(i=1;i<len;i++)
    {
        int value = *nums;
        if(value>max)
        {
            max = value;//如果找到比max还大的，则max让位
        }
        nums++;
    }
    return max;
}
*/
 
typedef struct _Dog
{
    char* name;
    int age;
} Dog;
typedef int (*compareFunc)(void * data1,void * data2);
//data 待比较数据数组的首地址,uniteSize单元字节个数
//size：数据的长度。{1,3,5,6}：size=4
//比较data1和data2指向的数据做比较，
//如果data1>data2，则返回正数
void* max(void* data,int unitSize,int size,
    compareFunc func)
{
    int i;
    char *ptr = (char *)data;
    char *max = ptr;//假定最开始的元素为最大值
    for(i=1;i<size;i++)
    {      
        char* item = ptr+i*unitSize;//计算第i个元素的首地址   
        if(func(item,max)>0)//如果item大于max
        //到底取几个字节进行比较是func内部的事情
        {
            max = item;
        }
    }
    return max;//最大值的首地址
}
 
//data1是第一个被比较数字的首地址
int intCompare(void* data1,void *data2)
{
    int* ptr1 = (int*)data1;
    int* ptr2 = (int*)data2;
    int i1=*ptr1;
    int i2=*ptr2;
    return i1-i2;
}
 
int dogCompare(void* data1,void* data2)
{
    Dog* dog1 = (Dog*)data1;
    Dog* dog2 = (Dog*)data2;
    return (dog1->age)-(dog2->age);
    //return (dog2->age)-(dog1->age);
}
 
int main(int argc, char *argv[])
{
    /*
    int nums[] = {3,5,8,7,6};
    int *pMax = (int *)max(nums,sizeof(int),sizeof(nums)/sizeof(int),
        intCompare);
    int max = *pMax;
    printf("%d
",max);
    */
    /*Dog dogs[] ={{"沙皮",3},{"腊肠",10},{"哈士奇",5},{"京巴",8},{"大狗",2}};*/
    /*Dog *pDog = (Dog *)max(dogs,sizeof(Dog),
        sizeof(dogs)/sizeof(Dog),dogCompare);
    printf("%s=%d",pDog->name,pDog->age);*/
    /*qsort(dogs,sizeof(dogs)/sizeof(Dog),sizeof(Dog),dogCompare);
    int i;
    for(i=0;i<sizeof(dogs)/sizeof(Dog);i++)
    {
        Dog dog = dogs[i];
        printf("%s=%d|",dog.name,dog.age);
    }*/
    int nums[] = {3,5,8,7,6};
    qsort(nums,sizeof(nums)/sizeof(int),sizeof(int),
        intCompare);
    int i;
    for(i=0;i<sizeof(nums)/sizeof(int);i++)
    {
        int n = nums[i];
        printf("%d|",n);
    }
 
    return 0;
}