mmap实现进程通讯

#include <stdio.h>#include <string.h>#include <sys/mman.h>#include <sys/types.h>#include <fcntl.h>#include <unistd.h>#include <string.h>typedef struct{    unsigned int size;    char*  content;}myshmem;typedef struct{    char name[128];    unsigned int size;    unsigned int avaliable;    char start[0];}mem_head;typedef enum{    READ = PROT_READ,    WRITE = PROT_WRITE}MODE;int mem_size;char mem_name[128];void* createHandle(const char* name, unsigned int size, MODE mode) // map a normal file as shared mem:{    int fd,exist;    if(size < sizeof(mem_head)){        //printf("size must large than %d\n",sizeof(mem_head));        return NULL;    }    if(strlen(name) > 128){        printf("size of name must small than 128\n");        return NULL;    }    mem_size = size;    strcpy(mem_name,name);    fd = open(name, O_CREAT|O_RDWR, 00777);    if(fd < 0 ){        printf("open %s failed\n",name);        return NULL;    }    unsigned int len = size + sizeof(mem_head);    lseek(fd, len - 1, SEEK_SET);    write(fd,"",1);    char* handle = (char*)mmap( NULL, len, mode, MAP_SHARED, fd, 0 );    close( fd );    if(handle == NULL){        printf("mmap error\n");        return NULL;    }    printf("initialize over\n");    return (void*)(handle);}void destoryHandle(void* handle){    mem_head* head = (mem_head*)handle;    unsigned int len = head->size + sizeof(mem_head);    munmap(handle, len);    printf( "umap ok \n" );}int writeHandle(void* handle, const char* content, unsigned int len){    //printf("writeHandle :%s  %d\n",content, len);    mem_head* head = (mem_head*)handle;    if(head != NULL ){        if(strcmp(head->name,mem_name)){            strcpy(head->name,mem_name);            head->avaliable = 0;        }         if(head->size != mem_size){            head->size = mem_size;            head->avaliable = 0;        }    } else{        printf("get mem_head failed\n");        return -1;    }    //printf("size:%d avaliable:%d name:%s\n",head->size,head->avaliable,head->name);    if(head->size < (head->avaliable + len)){        printf("share memory is full ,can not write\n");        return -1;    }    if(head->start == NULL){        printf("head->start is null\n");        return -1;    }    memcpy(head->start + head->avaliable , content, len);    //printf("write successed:%s\n",head->start);    head->avaliable += len;    return len;} int readHandle(void *handle, char* content, unsigned int offset, unsigned int len){    printf("readHandle\n");    mem_head* head = (mem_head*)handle;    if(head == NULL){        printf("head is null\n");        return -1;    }    if(strcmp(head->name,mem_name) || head->size != mem_size         || head->avaliable <= offset){        printf("there is no content to read\n");        return 0;    }    //printf("name:%s size:%d avaliable:%d \n",head->name,head->size,head->avaliable);    if(head->start == NULL){        printf("start is NULL\n");        return -1;    }    unsigned int length = head->avaliable > (offset + len) ? len : (head->avaliable - offset);    printf("%d\n",length);    memcpy(content, head->start + offset, length);    printf("read over\n");    return length;}int main(int argc, char** argv){    int i = 0;    if(strstr(argv[0],"write")){        printf("start write\n");        char* handle = (char*)createHandle(argv[1],1024*3,WRITE);        if(handle == NULL){            printf("createHandle failed\n");            return -1;        }        while(writeHandle(handle, "hello",sizeof("hello") -1)){            sleep(1);        }        printf("write hello\n");        sleep(10);        destoryHandle(handle);        return 0;    }else{        printf("start read\n");        char* handle = (char*)createHandle(argv[1],1024*3,READ);        if(handle == NULL){            printf("getHandle failed\n");            return -1;        }        char buffer[10] = {0};        int len = 0;        while((len = readHandle(handle,buffer,len,sizeof(buffer))) > 0){            printf("read :%s\n",buffer);            sleep(1);        }        printf("readHandle:%d %s\n ",len,buffer);        destoryHandle(handle);    }    return 0;}