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androidunixshared-memoryashmem

SHM replacement based on ASHMEM

I'm working on a library port from *nix to Android, and the library uses shared memory or shm. Android does not have System V shm. Instead it uses ashmem.

Is anyone aware of a shim library to map shm calls into ashmem? Google has not been very helpful.

Solution

  • This is how it worked for me while working with a similar problem of porting:

    Instead of using shmfd = open(SHM_PATH, O_RDWR) for creating and getting file descriptor I replaced it with

    int fd = ashmem_create_region("SharedRegionName", size);

    and used the file descriptor to get base address:

    int base_address = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

    You can pass the base_address to your java code from the native code using a native function that returns the descriptor.

    Android has a wrapper class for Ashmem named MemoryFile. You can also have a look in that.

    The following links helped me to create my own wrapper: