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@@ -12,26 +12,129 @@ |
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#include <string>
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#include <sys/shm.h>
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-
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-extern bool allocSharedMem(
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- std::string fname,
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- size_t len,
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- void ** dst,
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- const char *memName,
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- bool verbose);
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+#include <unistd.h>
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+#include <sys/shm.h>
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+#include <errno.h>
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+#include "str_util.h"
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extern void notifySharedMem(void *mem, size_t len);
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extern void waitSharedMem(void *mem, size_t len);
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-#define ALLOC_SHARED allocSharedMem
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+#define ALLOC_SHARED_U8 allocSharedMem<uint8_t>
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+#define ALLOC_SHARED_U32 allocSharedMem<uint32_t>
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#define FREE_SHARED shmdt
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#define NOTIFY_SHARED notifySharedMem
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#define WAIT_SHARED waitSharedMem
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+#define SHMEM_UNINIT 0xafba4242
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+#define SHMEM_INIT 0xffaa6161
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+
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+/**
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+ * Tries to allocate a shared-memory chunk for a given file of a given size.
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+ */
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+template <typename T>
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+bool allocSharedMem(std::string fname,
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+ size_t len,
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+ T ** dst,
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+ const char *memName,
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+ bool verbose)
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+{
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+ using namespace std;
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+ int shmid = -1;
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+ // Calculate key given string
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+ key_t key = (key_t)hash_string(fname);
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+ shmid_ds ds;
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+ int ret;
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+ // Reserve 4 bytes at the end for silly synchronization
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+ size_t shmemLen = len + 4;
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+ if(verbose) {
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+ cerr << "Reading " << len << "+4 bytes into shared memory for " << memName << endl;
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+ }
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+ T *ptr = NULL;
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+ while(true) {
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+ // Create the shrared-memory block
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+ if((shmid = shmget(key, shmemLen, IPC_CREAT | 0666)) < 0) {
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+ if(errno == ENOMEM) {
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+ cerr << "Out of memory allocating shared area " << memName << endl;
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+ } else if(errno == EACCES) {
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+ cerr << "EACCES" << endl;
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+ } else if(errno == EEXIST) {
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+ cerr << "EEXIST" << endl;
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+ } else if(errno == EINVAL) {
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+ cerr << "Warning: shared-memory chunk's segment size doesn't match expected size (" << (shmemLen) << ")" << endl
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+ << "Deleteing old shared memory block and trying again." << endl;
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+ shmid = shmget(key, 0, 0);
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+ if((ret = shmctl(shmid, IPC_RMID, &ds)) < 0) {
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+ cerr << "shmctl returned " << ret
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+ << " for IPC_RMID, errno is " << errno
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+ << ", shmid is " << shmid << endl;
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+ exit(1);
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+ } else {
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+ cerr << "Deleted shared mem chunk with shmid " << shmid << endl;
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+ }
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+ continue;
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+ } else if(errno == ENOENT) {
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+ cerr << "ENOENT" << endl;
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+ } else if(errno == ENOSPC) {
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+ cerr << "ENOSPC" << endl;
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+ } else {
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+ cerr << "shmget returned " << shmid << " for and errno is " << errno << endl;
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+ }
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+ exit(1);
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+ }
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+ ptr = (T*)shmat(shmid, 0, 0);
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+ if(ptr == (void*)-1) {
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+ cerr << "Failed to attach " << memName << " to shared memory with shmat()." << endl;
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+ exit(1);
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+ }
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+ if(ptr == NULL) {
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+ cerr << memName << " pointer returned by shmat() was NULL." << endl;
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+ exit(1);
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+ }
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+ // Did I create it, or did I just attach to one created by
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+ // another process?
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+ if((ret = shmctl(shmid, IPC_STAT, &ds)) < 0) {
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+ cerr << "shmctl returned " << ret << " for IPC_STAT and errno is " << errno << endl;
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+ exit(1);
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+ }
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+ if(ds.shm_segsz != shmemLen) {
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+ cerr << "Warning: shared-memory chunk's segment size (" << ds.shm_segsz
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+ << ") doesn't match expected size (" << shmemLen << ")" << endl
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+ << "Deleteing old shared memory block and trying again." << endl;
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+ if((ret = shmctl(shmid, IPC_RMID, &ds)) < 0) {
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+ cerr << "shmctl returned " << ret << " for IPC_RMID and errno is " << errno << endl;
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+ exit(1);
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+ }
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+ } else {
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+ break;
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+ }
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+ } // while(true)
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+ *dst = ptr;
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+ bool initid = (((volatile uint32_t*)((char*)ptr + len))[0] == SHMEM_INIT);
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+ if(ds.shm_cpid == getpid() && !initid) {
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+ if(verbose) {
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+ cerr << " I (pid = " << getpid() << ") created the "
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+ << "shared memory for " << memName << endl;
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+ }
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+ // Set this value just off the end of the chunk to
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+ // indicate that the data hasn't been read yet.
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+ ((volatile uint32_t*)((char*)ptr + len))[0] = SHMEM_UNINIT;
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+ return true;
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+ } else {
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+ if(verbose) {
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+ cerr << " I (pid = " << getpid()
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+ << ") did not create the shared memory for "
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+ << memName << ". Pid " << ds.shm_cpid << " did." << endl;
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+ }
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+ return false;
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+ }
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+}
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+
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#else
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-#define ALLOC_SHARED(...)
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+#define ALLOC_SHARED_U8(...)
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+#define ALLOC_SHARED_U32(...)
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#define FREE_SHARED(...)
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#define NOTIFY_SHARED(...)
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#define WAIT_SHARED(...)
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langmead
committed
langmead
committed
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