michael@0: /*
michael@0:  * Copyright 2013 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #include <unistd.h>
michael@0: #include <sys/mman.h>
michael@0: #include "SkDiscardableMemory.h"
michael@0: #include "SkTypes.h"
michael@0: #include "android/ashmem.h"
michael@0: 
michael@0: ////////////////////////////////////////////////////////////////////////////////
michael@0: namespace {
michael@0: /**
michael@0:  *  DiscardableMemory implementation that uses the Android kernel's
michael@0:  *  ashmem (Android shared memory).
michael@0:  */
michael@0: class SkAshmemDiscardableMemory : public SkDiscardableMemory {
michael@0: public:
michael@0:     SkAshmemDiscardableMemory(int fd, void* address, size_t size);
michael@0:     virtual ~SkAshmemDiscardableMemory();
michael@0:     virtual bool lock() SK_OVERRIDE;
michael@0:     virtual void* data() SK_OVERRIDE;
michael@0:     virtual void unlock() SK_OVERRIDE;
michael@0: private:
michael@0:     bool         fLocked;
michael@0:     int          fFd;
michael@0:     void*        fMemory;
michael@0:     const size_t fSize;
michael@0: };
michael@0: 
michael@0: SkAshmemDiscardableMemory::SkAshmemDiscardableMemory(int fd,
michael@0:                                                      void* address,
michael@0:                                                      size_t size)
michael@0:     : fLocked(true)  // Ashmem pages are pinned by default.
michael@0:     , fFd(fd)
michael@0:     , fMemory(address)
michael@0:     , fSize(size) {
michael@0:     SkASSERT(fFd >= 0);
michael@0:     SkASSERT(fMemory != NULL);
michael@0:     SkASSERT(fSize > 0);
michael@0: }
michael@0: 
michael@0: SkAshmemDiscardableMemory::~SkAshmemDiscardableMemory() {
michael@0:     SkASSERT(!fLocked);
michael@0:     if (NULL != fMemory) {
michael@0:         munmap(fMemory, fSize);
michael@0:     }
michael@0:     if (fFd != -1) {
michael@0:         close(fFd);
michael@0:     }
michael@0: }
michael@0: 
michael@0: bool SkAshmemDiscardableMemory::lock() {
michael@0:     SkASSERT(!fLocked);
michael@0:     if (-1 == fFd) {
michael@0:         fLocked = false;
michael@0:         return false;
michael@0:     }
michael@0:     SkASSERT(fMemory != NULL);
michael@0:     if (fLocked || (ASHMEM_NOT_PURGED == ashmem_pin_region(fFd, 0, 0))) {
michael@0:         fLocked = true;
michael@0:         return true;
michael@0:     } else {
michael@0:         munmap(fMemory, fSize);
michael@0:         fMemory = NULL;
michael@0: 
michael@0:         close(fFd);
michael@0:         fFd = -1;
michael@0:         fLocked = false;
michael@0:         return false;
michael@0:     }
michael@0: }
michael@0: 
michael@0: void* SkAshmemDiscardableMemory::data() {
michael@0:     SkASSERT(fLocked);
michael@0:     return fLocked ? fMemory : NULL;
michael@0: }
michael@0: 
michael@0: void SkAshmemDiscardableMemory::unlock() {
michael@0:     SkASSERT(fLocked);
michael@0:     if (fLocked && (fFd != -1)) {
michael@0:         ashmem_unpin_region(fFd, 0, 0);
michael@0:     }
michael@0:     fLocked = false;
michael@0: }
michael@0: }  // namespace
michael@0: ////////////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: SkDiscardableMemory* SkDiscardableMemory::Create(size_t bytes) {
michael@0:     // ashmem likes lengths on page boundaries.
michael@0:     const size_t mask = getpagesize() - 1;
michael@0:     size_t size = (bytes + mask) & ~mask;
michael@0: 
michael@0:     static const char name[] = "Skia_Ashmem_Discardable_Memory";
michael@0:     int fd = ashmem_create_region(name, size);
michael@0:     if (fd < 0) {
michael@0:         return NULL;
michael@0:     }
michael@0:     if (0 != ashmem_set_prot_region(fd, PROT_READ | PROT_WRITE)) {
michael@0:         close(fd);
michael@0:         return NULL;
michael@0:     }
michael@0:     void* addr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
michael@0:     if ((MAP_FAILED == addr) || (NULL == addr)) {
michael@0:         close(fd);
michael@0:         return NULL;
michael@0:     }
michael@0: 
michael@0:     return SkNEW_ARGS(SkAshmemDiscardableMemory, (fd, addr, size));
michael@0: }