SHM replacement based on ASHMEM

Question

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.

Accepted Answer

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:

- http://notjustburritos.tumblr.com/post/21442138796/an-introduction-to-android-shared-memory

- http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/2.2_r1.1/android/os/MemoryFile.java

- https://github.com/cozybit/aosp-frameworks-base/blob/master/core/jni/android_os_MemoryFile.cpp

SHM replacement based on ASHMEM

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