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一个用C/C++分别实现接口与实现相分离的设计原则的例子

lovedday — Sun, 30 Sep 2007 06:15:00 GMT

摘要: 良好的设计应该只暴露接口�l�用��P��所有的实现�l�节对用��h��说应该是隐藏的，也就是说用户只要�l�接口传递相应的参数��p��了，不需要管内部是如何实现的�Q�比如我们��用fopen�Q�fseek�Q�CreateWindow�{�函��C��发现很好用，而不需要管fopen�Q�fseek�Q�CreateWindow函数内部代码是如何实现的�Q�数据结构是如何�l�织的，也就是说�l�对不能暴露��M��的细节给用户�Q�包括数据组�l�在内�?nbsp; 阅读全文

lovedday 2007-09-30 14:15 发表评论

lovedday — Mon, 24 Sep 2007 11:04:00 GMT

今天看代码时�Q�发��C��个有用的东东�Q�offsetof(s,m)�Q�这是一个宏�Q�MSDN文档的说明如�?

Retrieves the offset of a member from the beginning of its parent structure.

size_t offsetof(
structName,
memberName
);

Parameters

structName
Name of the parent data structure.

memberName
Name of the member in the parent data structure for which to determine the offset.

Return Value

offsetof returns the offset in bytes of the specified member from the beginning of its parent data structure. It is undefined for bit fields.
Remarks

The offsetof macro returns the offset in bytes of memberName from the beginning of the structure specified by structName. You can specify types with the struct keyword.

Note

offsetof is not a function and cannot be described using a C prototype.

跟踪代码发现定义如下�Q?br>
#define offsetof(s,m) (size_t)&(((s *)0)->m)

然后到网上查了一下，发现�q�真的是很有用，附带一位大侠的解说�Q?br>
struct AAA
{
int i;
int j;
};

struct AAA *pAAA;
pAAA=new AAA;

�q�时�Q�pAAA实际上是一个Pointer, 指向某一��定的内存地址�Q�比�?x1234;
�?pAAA->i 整体是一个int型变量，其地址�?amp;(pAAA->i) ,'&'为取址�q�算�W�；
那么&(pAAA->i)一定等�?x1234�Q�因为i是结构体AAA的第一个元素�?
�?amp;(pAAA->j)一定是0x1234 + 0x4 = 0x1238; 因�ؓsizeof(int) = 4;

�q�个做法的��y妙之处就是：它把“0”作�ؓ上例中的pAAA,那么 &(pAAA->j)��是j的offset啦�?br>
解析�l�果是：
(s *)0 ,��?0 强制转换为Pointer to "s"
可以�?pS = (s *)0 �Q�pS是指向s的指针，它的值是0;
那么pS->m��是m�q�个元素了，�?amp;(pS->m)��是m的地址�Q�而在本例中就是offset�?

再把�l�果强制转换为size_t型的��OK 了，size_t其实也就是int啦！�Q?

也就是说�Q?/strong>

0 ---> (s *)0

原来�?是数值类型，现在是结构体指针�c�d��Q�尽��类型变了，但其��D��是不变，也就是说�q�是0�Q�但�q�个值的意义变了�Q�现在是地址�Q�而不是数倹{�?br>
&(((s *)0)->m)求出字段m的地址��|��但由于首地址�?�Q�所�?amp;(((s *)0)->m)求出字段m相对于首地址的偏�U�d��{�?br>

lovedday 2007-09-24 19:04 发表评论

C/C++之争

lovedday — Tue, 11 Sep 2007 14:28:00 GMT
     摘要: 目前�늚�很凶�?

都说什么C++快不行了�Q�可是游戏开发这�U�东西，�q�是非C++莫属�Q�图形开发这块C++�q�是强项。我发现C#�Q?JAVA之类的之所以能在企业��应用和快速开发方面占有优势，完全是因为别人已�l�帮你封装好了一套好用的API函数�Q�而不是这些语�a�的语法机制本�w�提供了多少优点�Q�而C++和C却不�q�么做，因�ؓC/C++�怿�使用它的�E�序员完全有能力自己��装�Q�没必要替他们封装�?nbsp; 阅读全文

lovedday 2007-09-11 22:28 发表评论

VS2005无法�q�行DEBUG�Q�Binary was not build with debug information.

lovedday — Sun, 01 Jul 2007 15:16:00 GMT
google到的解决�Ҏ��Q?br>
Its not an installation issue, the problem is, as the error message suggests, that you have not built your project with debug information.

To do this:
1) Goto Project->Properties
2) Make sure "Configuration" at the top is "Debug"
3) On the left, select "C/C++", then "General"
4) On the right, change "Debug information format" to "Program Database for edit and continue (/ZI)"
5) On the left, Select "Optimization"
6) On the right, Change "Optimization" to "Disabled (/Od)"
7) On the left, select "Code Generation"
8) On the right, change "Runtime library" to "Multi-Threaded Debug (/MTd)"
9) On the left, expand "Linker" and select "Debugging"
10) On the right, change "Generate Debug info" to "Yes (/DEBUG)"
11) Rebuild your project.

lovedday 2007-07-01 23:16 发表评论

一个有意思的�c�d��转换

lovedday — Fri, 11 May 2007 07:28:00 GMT

#include <stdio.h>

int main()
{
    float f_value1 = 5.2f;

    unsigned long ul_value1 = *((unsigned long *) &f_value1);

    float f_value2 = *((float *) &ul_value1);

    printf("\nf_value1 = %f, ul_value1 = %d, f_valu2 = %f", f_value1, ul_value1, f_value2);

    unsigned long ul_value2 = (unsigned long) f_value1;
    float f_value3 = (float) ul_value2;

    printf("\n\nul_value2 = %d, f_valu3 = %f", ul_value2, f_value3);

    printf("\n\n");

    return 0;
}

输出�Q?br>
f_value1 = 5.200000, ul_value1 = 1084647014, f_valu2 = 5.200000

ul_value2 = 5, f_valu3 = 5.000000

lovedday 2007-05-11 15:28 发表评论