Move libsystemproperties to external

native/jni/external/systemproperties/property_info_parser.cpp

@@ -0,0 +1,246 @@
+//
+// Copyright (C) 2017 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 "property_info_parser/property_info_parser.h"
+
+#include <fcntl.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+namespace android {
+namespace properties {
+
+namespace {
+
+// Binary search to find index of element in an array compared via f(search).
+template <typename F>
+int Find(uint32_t array_length, F&& f) {
+  int bottom = 0;
+  int top = array_length - 1;
+  while (top >= bottom) {
+    int search = (top + bottom) / 2;
+
+    auto cmp = f(search);
+
+    if (cmp == 0) return search;
+    if (cmp < 0) bottom = search + 1;
+    if (cmp > 0) top = search - 1;
+  }
+  return -1;
+}
+
+}  // namespace
+
+// Binary search the list of contexts to find the index of a given context string.
+// Only should be used for TrieSerializer to construct the Trie.
+int PropertyInfoArea::FindContextIndex(const char* context) const {
+  return Find(num_contexts(), [this, context](auto array_offset) {
+    auto string_offset = uint32_array(contexts_array_offset())[array_offset];
+    return strcmp(c_string(string_offset), context);
+  });
+}
+
+// Binary search the list of types to find the index of a given type string.
+// Only should be used for TrieSerializer to construct the Trie.
+int PropertyInfoArea::FindTypeIndex(const char* type) const {
+  return Find(num_types(), [this, type](auto array_offset) {
+    auto string_offset = uint32_array(types_array_offset())[array_offset];
+    return strcmp(c_string(string_offset), type);
+  });
+}
+
+// Binary search the list of children nodes to find a TrieNode for a given property piece.
+// Used to traverse the Trie in GetPropertyInfoIndexes().
+bool TrieNode::FindChildForString(const char* name, uint32_t namelen, TrieNode* child) const {
+  auto node_index = Find(trie_node_base_->num_child_nodes, [this, name, namelen](auto array_offset) {
+    const char* child_name = child_node(array_offset).name();
+    int cmp = strncmp(child_name, name, namelen);
+    if (cmp == 0 && child_name[namelen] != '\0') {
+      // We use strncmp() since name isn't null terminated, but we don't want to match only a
+      // prefix of a child node's name, so we check here if we did only match a prefix and
+      // return 1, to indicate to the binary search to search earlier in the array for the real
+      // match.
+      return 1;
+    }
+    return cmp;
+  });
+
+  if (node_index == -1) {
+    return false;
+  }
+  *child = child_node(node_index);
+  return true;
+}
+
+void PropertyInfoArea::CheckPrefixMatch(const char* remaining_name, const TrieNode& trie_node,
+                                        uint32_t* context_index, uint32_t* type_index) const {
+  const uint32_t remaining_name_size = strlen(remaining_name);
+  for (uint32_t i = 0; i < trie_node.num_prefixes(); ++i) {
+    auto prefix_len = trie_node.prefix(i)->namelen;
+    if (prefix_len > remaining_name_size) continue;
+
+    if (!strncmp(c_string(trie_node.prefix(i)->name_offset), remaining_name, prefix_len)) {
+      if (trie_node.prefix(i)->context_index != ~0u) {
+        *context_index = trie_node.prefix(i)->context_index;
+      }
+      if (trie_node.prefix(i)->type_index != ~0u) {
+        *type_index = trie_node.prefix(i)->type_index;
+      }
+      return;
+    }
+  }
+}
+
+void PropertyInfoArea::GetPropertyInfoIndexes(const char* name, uint32_t* context_index,
+                                              uint32_t* type_index) const {
+  uint32_t return_context_index = ~0u;
+  uint32_t return_type_index = ~0u;
+  const char* remaining_name = name;
+  auto trie_node = root_node();
+  while (true) {
+    const char* sep = strchr(remaining_name, '.');
+
+    // Apply prefix match for prefix deliminated with '.'
+    if (trie_node.context_index() != ~0u) {
+      return_context_index = trie_node.context_index();
+    }
+    if (trie_node.type_index() != ~0u) {
+      return_type_index = trie_node.type_index();
+    }
+
+    // Check prefixes at this node.  This comes after the node check since these prefixes are by
+    // definition longer than the node itself.
+    CheckPrefixMatch(remaining_name, trie_node, &return_context_index, &return_type_index);
+
+    if (sep == nullptr) {
+      break;
+    }
+
+    const uint32_t substr_size = sep - remaining_name;
+    TrieNode child_node;
+    if (!trie_node.FindChildForString(remaining_name, substr_size, &child_node)) {
+      break;
+    }
+
+    trie_node = child_node;
+    remaining_name = sep + 1;
+  }
+
+  // We've made it to a leaf node, so check contents and return appropriately.
+  // Check exact matches
+  for (uint32_t i = 0; i < trie_node.num_exact_matches(); ++i) {
+    if (!strcmp(c_string(trie_node.exact_match(i)->name_offset), remaining_name)) {
+      if (context_index != nullptr) {
+        if (trie_node.exact_match(i)->context_index != ~0u) {
+          *context_index = trie_node.exact_match(i)->context_index;
+        } else {
+          *context_index = return_context_index;
+        }
+      }
+      if (type_index != nullptr) {
+        if (trie_node.exact_match(i)->type_index != ~0u) {
+          *type_index = trie_node.exact_match(i)->type_index;
+        } else {
+          *type_index = return_type_index;
+        }
+      }
+      return;
+    }
+  }
+  // Check prefix matches for prefixes not deliminated with '.'
+  CheckPrefixMatch(remaining_name, trie_node, &return_context_index, &return_type_index);
+  // Return previously found prefix match.
+  if (context_index != nullptr) *context_index = return_context_index;
+  if (type_index != nullptr) *type_index = return_type_index;
+  return;
+}
+
+void PropertyInfoArea::GetPropertyInfo(const char* property, const char** context,
+                                       const char** type) const {
+  uint32_t context_index;
+  uint32_t type_index;
+  GetPropertyInfoIndexes(property, &context_index, &type_index);
+  if (context != nullptr) {
+    if (context_index == ~0u) {
+      *context = nullptr;
+    } else {
+      *context = this->context(context_index);
+    }
+  }
+  if (type != nullptr) {
+    if (type_index == ~0u) {
+      *type = nullptr;
+    } else {
+      *type = this->type(type_index);
+    }
+  }
+}
+
+bool PropertyInfoAreaFile::LoadDefaultPath() {
+  return LoadPath("/dev/__properties__/property_info");
+}
+
+bool PropertyInfoAreaFile::LoadPath(const char* filename) {
+  int fd = open(filename, O_CLOEXEC | O_NOFOLLOW | O_RDONLY);
+
+  struct stat fd_stat;
+  if (fstat(fd, &fd_stat) < 0) {
+    close(fd);
+    return false;
+  }
+
+  if ((fd_stat.st_uid != 0) || (fd_stat.st_gid != 0) ||
+      ((fd_stat.st_mode & (S_IWGRP | S_IWOTH)) != 0) ||
+      (fd_stat.st_size < static_cast<off_t>(sizeof(PropertyInfoArea)))) {
+    close(fd);
+    return false;
+  }
+
+  auto mmap_size = fd_stat.st_size;
+
+  void* map_result = mmap(nullptr, mmap_size, PROT_READ, MAP_SHARED, fd, 0);
+  if (map_result == MAP_FAILED) {
+    close(fd);
+    return false;
+  }
+
+  auto property_info_area = reinterpret_cast<PropertyInfoArea*>(map_result);
+  if (property_info_area->minimum_supported_version() > 1 ||
+      property_info_area->size() != mmap_size) {
+    munmap(map_result, mmap_size);
+    close(fd);
+    return false;
+  }
+
+  close(fd);
+  mmap_base_ = map_result;
+  mmap_size_ = mmap_size;
+  return true;
+}
+
+void PropertyInfoAreaFile::Reset() {
+  if (mmap_size_ > 0) {
+    munmap(mmap_base_, mmap_size_);
+  }
+  mmap_base_ = nullptr;
+  mmap_size_ = 0;
+}
+
+}  // namespace properties
+}  // namespace android