#ifndef DLT_SHM_H
#define DLT_SHM_H
+/* shared memory key */
+/* must be the same for server and cleint */
#define DLT_SHM_KEY 11771
+
+/* default size of shared memory */
+/* size is extended during creation to fit segment size */
+/* client retreives real size from shm buffer */
#define DLT_SHM_SIZE 100000
+
+/* Id of the used semaphore */
+/* used for synchronisation of write and read access of multiple clients and server */
+/* must be the same for server and client */
#define DLT_SHM_SEM 22771
typedef struct
{
- int shmid; // Id of shared memory
- int semid; // Id of semaphore
- char* shm; // pointer to beginning of shared memory
- int size; // size of data areay in shared memory
- char* mem; // pointer to data area in shared memory
+ int shmid; /* Id of shared memory */
+ int semid; /* Id of semaphore */
+ char* shm; /* pointer to beginning of shared memory */
+ int size; /* size of data area in shared memory */
+ char* mem; /* pointer to data area in shared memory */
} DltShm;
#define DLT_SHM_SEM_GET(id) dlt_shm_pv(id,-1)
#define DLT_SHM_SEM_FREE(id) dlt_shm_pv(id,1)
+/**
+ * Initialise the shared memory on the client side.
+ * This function must be called before using further shm functions.
+ * @param buf pointer to shm structure
+ * @param key the identifier of the shm, must be the same for server and client
+ * @return negative value if there was an error
+ */
extern int dlt_shm_init_client(DltShm *buf,int key);
+
+/**
+ * Initialise the shared memory on the server side.
+ * This function must be called before using further shm functions.
+ * @param buf pointer to shm structure
+ * @param key the identifier of the shm, must be the same for server and client
+ * @param size the requested size of the shm
+ * @return negative value if there was an error
+ */
extern int dlt_shm_init_server(DltShm *buf,int key,int size);
+/**
+ * Push data from client onto the shm.
+ * @param buf pointer to shm structure
+ * @param data1 pointer to first data block to be written, null if not used
+ * @param size1 size in bytes of first data block to be written, 0 if not used
+ * @param data2 pointer to second data block to be written, null if not used
+ * @param size2 size in bytes of second data block to be written, 0 if not used
+ * @param data3 pointer to third data block to be written, null if not used
+ * @param size3 size in bytes of third data block to be written, 0 if not used
+ * @return negative value if there was an error
+ */
extern int dlt_shm_push(DltShm *buf,const unsigned char *data1,unsigned int size1,const unsigned char *data2,unsigned int size2,const unsigned char *data3,unsigned int size3);
+
+/**
+ * Pull data from shm.
+ * This function should be called from client.
+ * Data is deleted from shm after this call.
+ * @param buf pointer to shm structure
+ * @param data pointer to buffer where data is to be written
+ * @param size maximum size to be written into buffer
+ * @return negative value if there was an error
+ */
extern int dlt_shm_pull(DltShm *buf,unsigned char *data, int size);
+
+/**
+ * Copy message from shm.
+ * This function should be called from server.
+ * Data is not deleted from shm after this call.
+ * @param buf pointer to shm structure
+ * @param data pointer to buffer where data is to be written
+ * @param size maximum size to be written into buffer
+ * @return negative value if there was an error
+ */
extern int dlt_shm_copy(DltShm *buf,unsigned char *data, int size);
+
+/**
+ * Delete message from shm.
+ * This function should be called from server.
+ * This function should be called after each succesful copy.
+ * @param buf pointer to shm structure
+ * @return negative value if there was an error
+ */
extern int dlt_shm_remove(DltShm *buf);
+/**
+ * Print information about shm.
+ * @param buf pointer to shm structure
+ */
extern void dlt_shm_info(DltShm *buf);
+
+/**
+ * Print status about shm.
+ * @param buf pointer to shm structure
+ */
extern void dlt_shm_status(DltShm *buf);
+/**
+ * Deinitialise the shared memory on the client side.
+ * @param buf pointer to shm structure
+ * @return negative value if there was an error
+ */
extern int dlt_shm_free_client(DltShm *buf);
+
+/**
+ * Deinitialise the shared memory on the server side.
+ * @param buf pointer to shm structure
+ * @return negative value if there was an error
+ */
extern int dlt_shm_free_server(DltShm *buf);
#endif /* DLT_SHM_H */
}
int dlt_shm_init_server(DltShm *buf,int key,int size) {
+ struct shmid_ds shm_buf;
// Init parameters
buf->shm = NULL;
return -1; /* ERROR */
}
+ // get the size of shm
+ if (shmctl(buf->shmid, IPC_STAT, &shm_buf))
+ {
+ perror("shmctl");
+ return -1; /* ERROR */
+ }
+
// Now we attach the segment to our data space.
if ((buf->shm = shmat(buf->shmid, NULL, 0)) == (char *) -1) {
perror("shmat");
((int*)(buf->shm))[1] = 0; // pointer to read memory
((int*)(buf->shm))[2] = 0; // number of packets
buf->mem = (char*)(&(((int*)(buf->shm))[3]));
- buf->size = size - (buf->mem - buf->shm);
+ buf->size = shm_buf.shm_segsz - (buf->mem - buf->shm);
// clear memory
memset(buf->mem,0,buf->size);
+ //dlt_shm_status(buf);
+ //dlt_shm_info(buf);
+ printf("SHM: Size %d\n",buf->size);
+
return 0; /* OK */
}
buf->mem = (char*)(&(((int*)(buf->shm))[3]));
buf->size = shm_buf.shm_segsz - (buf->mem - buf->shm);
+ //dlt_shm_status(buf);
+ //dlt_shm_info(buf);
+
return 0; /* OK */
}
}
else // read <= write
{
- if((write + size1+size2+size3 + sizeof(unsigned char)+sizeof(int)) > buf->size) {
+ if((write+size1+size2+size3+sizeof(unsigned char)+sizeof(int)) > buf->size) {
// data does not fit at end of buffer
// try write at beginning
if((size1+size2+size3+sizeof(unsigned char)+sizeof(int)) > read) {
//printf("SHM is full at start\n");
return -1; // ERROR
}
- // write zero and start buffer at beginning
+ // write zero status and size at end if possible
if((write+sizeof(unsigned char)+sizeof(int)) <= buf->size) {
*((unsigned char*)(buf->mem+write)) = 0; // init write status to unused
*((int*)(buf->mem+write+sizeof(unsigned char))) = 0; // init write size to unused
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