다양한 포인터 활용 예제들

#include <stdio.h>
#include <string.h>

struct data {
	int a;
	char *b;
};

int main()
{
	struct data aData;

	aData.a = 100;
	aData.b = (char *)malloc(10);
	strcpy(aData.b, "mwyun");

	printf("aData.a=%d\n", aData.a);
	printf("aData.b=%s\n", aData.b);

	free(aData.b);

	return 0;
}

#include <stdio.h>
#include <string.h>

struct data {
	int a;
	char *b;
};

void SetData(struct data *pData)
{
	pData->a = 100;
	pData->b = (char *)malloc(10);
	strcpy(pData->b, "mwyun");
}

int main()
{
	struct data aData;

	SetData(&aData);

	printf("aData.a=%d\n", aData.a);
	printf("aData.b=%s\n", aData.b);

	free(aData.b);

	return 0;
}

#include <stdio.h>
#include <string.h>

struct data {
	int a;
	char *b;
};

const char *str = "Hello, Joinc!";

void SetData(struct data *pData)
{
	pData->a = 100;
	pData->b = str; // <- 주목!
}

int main()
{
	struct data aData;

	SetData(&aData);

	printf("aData.a=%d\n", aData.a);
	printf("aData.b=%s\n", aData.b);

	return 0;
}

#include <stdio.h>
#include <string.h>

struct data {
	int a;
	char *b;
};

int main()
{
	struct data *pData;

	pData = (struct data *)malloc(sizeof(struct data));

	pData->a = 100;
	pData->b = (char *)malloc(10);
	strcpy(pData->b, "mwyun");

	printf("pData->a=%d\n", pData->a);
	printf("pData->b=%s\n", pData->b);

	free(pData->b);
	free(pData);

	return 0;
}

#include <stdio.h>
#include <string.h>

struct data {
	int a;
	char *b;
};

void SetData(struct data *pData)
{
	pData->a = 100;
	pData->b = (char *)malloc(10);
	strcpy(pData->b, "mwyun");
}

int main()
{
	struct data *pData;

	pData = (struct data *)malloc(sizeof(struct data));

	SetData(pData);

	printf("pData->a=%d\n", pData->a);
	printf("pData->b=%s\n", pData->b);

	free(pData->b);
	free(pData);

	return 0;
}

#include <stdio.h>
#include <string.h>

struct data {
	int Id;
	char *Name;
	void (*SetName)(struct data *pData, char *NewName);
	char *(*GetName)(struct data *pData);
	void (*Clear)(struct data *pData);
};

void SetName(struct data *pData, char *NewName)
{
	if (pData->Name)
	{
		if (strlen(pData->Name) < strlen(NewName))
		{
			free(pData->Name);
			pData->Name = (char *)malloc(strlen(NewName)+1);	
		}
	}
	else
	{
		pData->Name = (char *)malloc(strlen(NewName)+1);
	}
	
	strcpy(pData->Name, NewName);
}

char *GetName(struct data *pData)
{
	if (pData->Name)
		return pData->Name;
	else
		return NULL;
}

void Clear(struct data *pData)
{
	pData->Id = 0;
	if (pData->Name)
	{
		free(pData->Name);
		pData->Name = NULL;
	}
	pData->GetName = NULL;
	pData->SetName = NULL;
	pData->Clear = NULL;
}

int main()
{
	struct data aData;

        memset((void *)&aData, 0x00, sizeof(struct data));
	aData.Id = 100;
	aData.GetName = GetName;
	aData.SetName = SetName;
	aData.Clear = Clear;

	printf("aData.Id=%d\n", aData.Id);
	aData.SetName(&aData, "mwyun");
	printf("aData.Name=%s\n", aData.GetName(&aData));
	aData.Clear(&aData);

	return 0;
}

#include <stdio.h>
#include <string.h>

struct data {
	int Id;
	char *Name;
	void (*SetName)(struct data *pData, char *NewName);
	char *(*GetName)(struct data *pData);
	void (*Clear)(struct data *pData);
};

void SetName(struct data *pData, char *NewName)
{
	if (pData->Name)
	{
		if (strlen(pData->Name) < strlen(NewName))
		{
			free(pData->Name);
			pData->Name = (char *)malloc(strlen(NewName)+1);	
		}
	}
	else
	{
		pData->Name = (char *)malloc(strlen(NewName)+1);
	}
	
	strcpy(pData->Name, NewName);
}

char *GetName(struct data *pData)
{
	if (pData->Name)
		return pData->Name;
	else
		return NULL;
}

void Clear(struct data *pData)
{
	pData->Id = 0;
	if (pData->Name)
	{
		free(pData->Name);
		pData->Name = NULL;
	}
	pData->GetName = NULL;
	pData->SetName = NULL;
	pData->Clear = NULL;
}

int main()
{
	struct data *pData;

	pData = (struct data *)malloc(sizeof(struct data));

	pData->Id = 100;
	pData->GetName = GetName;
	pData->SetName = SetName;
	pData->Clear = Clear;

	printf("pData->Id=%d\n", pData->Id);
	pData->SetName(pData, "mwyun");
	printf("pData->Name=%s\n", pData->GetName(pData));
	pData->Clear(pData);

	free(pData);

	return 0;
}

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

struct data {
	int Id;
	char *Name;
	void (*SetName)(struct data *pData, char *NewName);
	char *(*GetName)(struct data *pData);
	void (*Print)(struct data *pData);
	void (*Clear)(struct data *pData);
};

void SetName(struct data *pData, char *NewName)
{
	if (!pData)
		return;

	if (pData->Name)
	{
		if (strlen(pData->Name) < strlen(NewName))
		{
			free(pData->Name);
			pData->Name = (char *)malloc(strlen(NewName)+1);	
		}
	}

	else
	{
		pData->Name = (char *)malloc(strlen(NewName)+1);
	}

	strcpy(pData->Name, NewName);
}

char *GetName(struct data *pData)
{
	if (!pData)
		return NULL;

	if (pData->Name)
		return pData->Name;
	else
		return NULL;

}

void Clear(struct data *pData)
{
	if (!pData)
		return;

	pData->Id = 0;
	if (pData->Name)
	{

		free(pData->Name);
		pData->Name = NULL;
	}

	pData->GetName = NULL;
	pData->SetName = NULL;
	pData->Clear = NULL;
}

void Print(struct data *pData)
{
	if (!pData)
		return;

	printf("pData->Id=%d\n", pData->Id);
	printf("pData->Name=%s\n", pData->GetName(pData));
}

struct data *Create(int Id, char *Name)
{
	struct data *pData;

	pData = (struct data *)malloc(sizeof(struct data));

	if (!pData)
		return NULL;

         // 함수의 시작 주소를 저장
	pData->GetName = GetName; 
	pData->SetName = SetName;
	pData->Print = Print;
	pData->Clear = Clear;

	pData->Id = Id;
	pData->SetName(pData, Name);

	return pData;
}

void Destroy(struct data *pData)
{
	if (!pData)
		return;

	pData->Clear(pData);
	free(pData);

	pData = NULL;
}

int main(int argc, char **argv)
{
	struct data *pData;

	if (argc != 3)
		return -1;

	pData = Create(atoi(argv[1]), argv[2]);
	pData->Print(pData);
	Destroy(pData);

	return 0;
}