1 files changed, 104 insertions, 0 deletions
diff --git a/libs/ui/BufferHubMetadata.cpp b/libs/ui/BufferHubMetadata.cpp
new file mode 100644
index 0000000000..05bc7ddfbe
--- /dev/null
+++ b/libs/ui/BufferHubMetadata.cpp
@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <sys/mman.h>
+#include <limits>
+
+#include <cutils/ashmem.h>
+#include <log/log.h>
+#include <ui/BufferHubMetadata.h>
+
+namespace android {
+
+namespace {
+
+static const int kAshmemProt = PROT_READ | PROT_WRITE;
+
+} // namespace
+
+using BufferHubDefs::kMetadataHeaderSize;
+using BufferHubDefs::MetadataHeader;
+
+/* static */
+BufferHubMetadata BufferHubMetadata::create(size_t userMetadataSize) {
+    // The size the of metadata buffer is used as the "width" parameter during allocation. Thus it
+    // cannot overflow uint32_t.
+    if (userMetadataSize >= (std::numeric_limits<uint32_t>::max() - kMetadataHeaderSize)) {
+        ALOGE("BufferHubMetadata::Create: metadata size too big: %zu.", userMetadataSize);
+        return {};
+    }
+
+    const size_t metadataSize = userMetadataSize + kMetadataHeaderSize;
+    int fd = ashmem_create_region(/*name=*/"BufferHubMetadata", metadataSize);
+    if (fd < 0) {
+        ALOGE("BufferHubMetadata::Create: failed to create ashmem region.");
+        return {};
+    }
+
+    // Hand over the ownership of the fd to a unique_fd immediately after the successful
+    // return of ashmem_create_region. The ashmemFd is going to own the fd and to prevent fd
+    // leaks during error handling.
+    unique_fd ashmemFd{fd};
+
+    if (ashmem_set_prot_region(ashmemFd.get(), kAshmemProt) != 0) {
+        ALOGE("BufferHubMetadata::Create: failed to set protect region.");
+        return {};
+    }
+
+    return BufferHubMetadata::import(std::move(ashmemFd));
+}
+
+/* static */
+BufferHubMetadata BufferHubMetadata::import(unique_fd ashmemFd) {
+    if (!ashmem_valid(ashmemFd.get())) {
+        ALOGE("BufferHubMetadata::Import: invalid ashmem fd.");
+        return {};
+    }
+
+    size_t metadataSize = static_cast<size_t>(ashmem_get_size_region(ashmemFd.get()));
+    size_t userMetadataSize = metadataSize - kMetadataHeaderSize;
+
+    // Note that here the buffer state is mapped from shared memory as an atomic object. The
+    // std::atomic's constructor will not be called so that the original value stored in the memory
+    // region can be preserved.
+    auto metadataHeader = static_cast<MetadataHeader*>(mmap(nullptr, metadataSize, kAshmemProt,
+                                                            MAP_SHARED, ashmemFd.get(),
+                                                            /*offset=*/0));
+    if (metadataHeader == nullptr) {
+        ALOGE("BufferHubMetadata::Import: failed to map region.");
+        return {};
+    }
+
+    return BufferHubMetadata(userMetadataSize, std::move(ashmemFd), metadataHeader);
+}
+
+BufferHubMetadata::BufferHubMetadata(size_t userMetadataSize, unique_fd ashmemFd,
+                                     MetadataHeader* metadataHeader)
+      : mUserMetadataSize(userMetadataSize),
+        mAshmemFd(std::move(ashmemFd)),
+        mMetadataHeader(metadataHeader) {}
+
+BufferHubMetadata::~BufferHubMetadata() {
+    if (mMetadataHeader != nullptr) {
+        int ret = munmap(mMetadataHeader, metadataSize());
+        ALOGE_IF(ret != 0,
+                 "BufferHubMetadata::~BufferHubMetadata: failed to unmap ashmem, error=%d.", errno);
+        mMetadataHeader = nullptr;
+    }
+}
+
+} // namespace android