问题
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.
回答1:
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
回答2:
Here's a library, which you can LD_PRELOAD to simulate Linux shared memory using Android ashmem (shmget/shmat/shmdt/shmctl calls), you can also link to this library directly.
https://github.com/pelya/android-shmem
来源：https://stackoverflow.com/questions/17510157/shm-replacement-based-on-ashmem