linux下的圖像傳輸（利用共享內存實現圖像傳輸）

        共享內存是進程之間通信最快的方式。client將圖像數據讀入共享內存，server從共享內存中讀取數據。採用共享內存中的一個字符作爲標誌位實現共享內存的同步。

server.c
// server:讀取共享內存圖像數據
#include "comm.h"

static int SHMID = 0;
static unsigned char *ADDR = NULL;

void main()
{
	int iLoop = 5;
	int date = 0;
	FILE *img = NULL;

	// 初始化共享內存
	SHMID = CreateShm(4096+1);
	if(SHMID==-1)
	{
		printf("create share memory failed!\n");
		exit(1);
	}
	
	ADDR = shmat(SHMID, NULL, 0);
	
	printf("init server share memory succeed, shmid = %d\n", SHMID);
	
	while((img = fopen("/home/fxhui/IPC/ipc_pv_img/new.jpg", "wb")) == NULL && iLoop)
	{
		printf("open file failed!, [%d]\n", iLoop);
		iLoop--;
		sleep(1);
	}
	
	// 信號同步
	int semid;
	int b = 0;
	
	if((semid = initsem(0x200)) < 0)
	{
		printf("server init sem error!\n");
		exit(1);
	}
	int fwriteSize = 0;
	while(1)
	{
		if(ADDR[4096] == 'b')
		{
			fwriteSize = fwrite(ADDR, 1, 4096, img);
			ADDR[4096] = 'a';
			printf("fwriteSize = %d\n", fwriteSize);
		}
		if(ADDR[4096] == 'c')
		{
			fwriteSize = fwrite(ADDR, 1, 731, img);
			printf("fwriteSize = %d\n", fwriteSize);
			break;
		}
	}
	
/* 方式二
	while(1)
	{
		if(ADDR[4096] == 'b')
		{
			b = atoi(ADDR);
			printf("recv data = [%d]\n", b);
			fputc(b, img);
			ADDR[4095] = 'a';
		}
		if(ADDR[4096] == 'c')
			break;
	}
*/	
	fclose(img);	
	
	shmdt(ADDR);
	DestroyShm(SHMID);	  // 銷燬IPC
}

client.c

// client:寫入共享內存圖像數據
#include "comm.h"

static int SHMID = 0;
static unsigned char *ADDR = NULL;

int main()
{
	// 獲取共享內存
	int iLoop = 5;
	SHMID = GetShm(4096+1); // 獲取IPC鍵值：申請4096+1個字節的內存
	ADDR = shmat(SHMID, NULL, 0);	// 共享內存映射到進程頁表
	printf("client init share memory succeed, SHMID = %d\n", SHMID);
	
	// 準備傳送的數據
	FILE *img;
	char path[100] = { 0 };
	snprintf(path, 100, "%s", "/home/fxhui/IPC/ipc_pv_img/LF.jpg");
	while((img = fopen(path, "rb")) == NULL && iLoop)
	{
		printf("open file failed!, [%d]\n", iLoop);
		iLoop--;
		sleep(1);
	}
	
	fseek(img, 0, SEEK_END);
	int len = ftell(img);
	int m = len / 4096;
	int n = len % 4096;	
	fseek(img, 0, SEEK_SET);
	
	printf("%d %d \n", m ,n);

	// 信號同步
	int semid;
	if((semid=initsem(0x200)) < 0)
	{
		printf("server init sem error!\n");
		exit(1);
	}
	unsigned char *buffer;
	int freadSize = 0;
	buffer = (unsigned char *)malloc(sizeof(unsigned char)*4096);
	ADDR[4096] = 'a';
	while(1)
	{
		if(ADDR[4096] == 'a' && m--)
		{
			freadSize = fread(ADDR, 1, 4096, img);
			ADDR[4096] = 'b';
			printf("m = %d, freadSize = %d\n", m, freadSize);
		}
		if(m == 0)
		{
			sleep(1);
			ADDR[4096] = 'c';
			freadSize = fread(ADDR, 1, n, img);
			printf("m = %d, freadSize = %d\n", m, freadSize);
			printf("圖像讀取完畢!\n");
			break;
		}
	}
/*	int c = 0;
	ADDR[4095] = 'a';
	while(1)
	{
		if(ADDR[4095] == 'a')
		{
			if((c=fgetc(img))!= EOF)
			{
				printf("read date : [%d]\n",c);
				sprintf(ADDR,"%d",c);
				ADDR[4095] = 'b';
			}
			else
			{	
				ADDR[4095] = 'c';
				printf("圖像讀取完畢!\n");
				break;
			}
		}
	}
*/	
	free(buffer);
	sleep(1);
	fclose(img);
	shmdt(ADDR);
	
	return 0;
}

使用兩種方式實現數據的操作：fgetc讀取一個字節的數據和fread讀取一塊數據，兩種方式。

值得注意的是，使用了ADDR[4096]實現server和client的同步。

全部代碼：https://download.csdn.net/download/fengxianghui01/12302586