编程范式 episode 6 实现stack 栈功能_ to do

//既然在这里开始，那就在这里结束。

 实现stack 功能

____coding

_using subfunction to focus on the main aim of current function

_void* is not allowed to do arithmetic operation

_makde sure parameters are valid before using them,especially related to pointer.

_____assert测试

assert带有一个断言作为int 类型参数，断言是指正常情况下为真的表达式。assert是一个宏，但是用函数实现的。

当参数为0，编译停止，提供参数信息输出显示。调试结束后，取消assert测试，只需加上一句

#define NDEBUG 在#include "assert.h"之前。

____void * realloc(void * p, int size);

return the same pointer in the parameter.

if current space is not enough, than go to a new place ,a pointer will be returned correspondly. The orighinal dates will be coped into the new space,2 cases: 1,integars will be copied directly. 2,if char,will consider the dates as address pointing at the char,so  in the new space ,also address is copied and stored....

____when dealing with pointers, make sure the pointer is valid one.use assert to perform the check.

____stark 的char 型实现。

typedef struct {
    uchar length;
    uchar allocSize;
    uchar* elem;
}stack;

void stackNew(stack *s);
void stackDispose(stack *s);
void stackPush(stack *s, uchar* date);
void stackPop(stack *s, uchar* date);

void stackNew(stack *s)
{
    assert(s!=NULL);
    s->length = 0;
    s->allocSize = 4;
    s->elem = malloc(4*sizeof(uchar));
    assert(s->elem != NULL);
}
void stackDispose(stack *s)
{
    assert(s != NULL && s->elem != NULL);
    free(s->elem);
}

void stackPush(stack *s, uchar* date)
{
    assert(s!=NULL && date != NULL);
    if(s->length == s->allocSize)
    {
        s->allocSize *= 2;

        s->elem = realloc(s->elem,s->allocSize);  //reallocate designate size
        assert(s->elem != NULL);    
    }
    *(s->elem+s->length) = *date;    //s->elem[s->length-1] = *date;
    s->length += 1;
}

void stackPop(stack *s, uchar* date)
{
    assert(s!=NULL && date!=NULL);

    assert(s->length >= 1);

    --s->length;
    *date = s->elem[s->length];
}

stack generic function

typedef struct {
    void* elem;
    uchar elemSize;
    uchar logicalLen;
    uchar allocSize;
}stack;

void stackNew(stack *s,uchar elemSize);
void stackDispose(stack *s);
void stackPush(stack *s,void* elemAdder);
void stackPop(stack *s,void* elemAdder);

void stackNew(stack *s,uchar elemSize)
{
    assert(s!=NULL);
    assert(elemSize >= 0);        //parameter check

    s->elemSize = elemSize;
    s->logicalLen = 0;
    s->allocSize = 4;
    s->elem = malloc(4*elemSize);
    assert(s->elem != NULL);
}

void stackDispose(stack *s)
{
    assert(s != NULL && s->elem != NULL);
    free(s->elem);
}

static void stackGrow(stack*s)  // use static to prenvent the calling from other files.
{
    s->allocSize *= 2;
    s->elem = realloc(s->elem,s->allocSize);  //reallocate designate size
    assert(s->elem != NULL);
}

void stackPush(stack *s,void* elemAdder)
{
//    assert(s!=NULL && elemAdder != NULL);
    if(s->logicalLen == s->allocSize)
    {
        ////Using subfunction to focuse one the key point.
        stackGrow(s);
    }
    ////   void* is not allowed to perform arithmetic operation
    void* target = (uchar*)s->elem + s->logicalLen * s->elemSize;
    memcpy(target,elemAdder,s->elemSize);
    s->logicalLen += 1;
}

void stackPop(stack *s, void* elemAddre)
{
    //    assert(s!=NULL && elemAdder != NULL);
    assert(s->logicalLen >= 1);

    s->logicalLen -= 1;;
    void* position = (uchar*)s->elem + s->logicalLen * s->elemSize;
    memcpy(elemAddre,position,s->elemSize);
}

int main()
{
    const char* friends[3] = {"a1","b2","c3"};
    stack stringStack;
    uchar i;
    uchar* copy;
    stackNew(&stringStack,sizeof(uchar**));

    for(i = 0;i < 3;i++)
    {
        copy =strdup(friends[i]);
        stackPush(&stringStack,&copy);
    }
    char *name;
    for(i = 0; i < 3; i++)
    {
        stackPop(&stringStack,&name);
        printf("%s
",name);
        free(name);
    }
    stackDispose(&stringStack);
    return 0;
}

//在之前的程序上修改新的功能时，多了出现bug的机会

一行一行检查，避免疏忽造成的错误

就算出错了也不要紧，一行一行找，总是可以找到问题。

这世界上再也没有比程序的运行更确定的事情，这也是我喜欢这一行的原因