src/base/android_util.cc

// Copyright 2010-2014, Google Inc.
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//
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// modification, are permitted provided that the following conditions are
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//
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// notice, this list of conditions and the following disclaimer.
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// distribution.
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#include "base/android_util.h"

#include <fstream>

#include "base/logging.h"
#include "base/mutex.h"
#include "base/util.h"

namespace {
const char kBuildPropPath[] = "/system/build.prop";
static mozc::Mutex sys_prop_mutex;
}  // namespace

namespace mozc {
map<string, string> AndroidUtil::property_cache;
set<string> AndroidUtil::undefined_keys;
const char AndroidUtil::kSystemPropertyOsVersion[] = "ro.build.version.release";
const char AndroidUtil::kSystemPropertyModel[] = "ro.product.model";
const char AndroidUtil::kSystemPropertySdkVersion[] = "ro.build.version.sdk";

// static
string AndroidUtil::GetSystemProperty(const string &key,
                                      const string &default_value) {
  mozc::scoped_lock lock(&sys_prop_mutex);
  map<string, string>::iterator it = property_cache.find(key);
  if (it != property_cache.end()) {
    // Cache is found.
    return it->second;
  }
  if (undefined_keys.find(key) != undefined_keys.end()) {
    // Found the key invalid in the |undefined_keys| cache.
    return default_value;
  }
  // Cache is not found.
  // We have not been passed |key| yet. It is the first time.
  string value;
  if (GetPropertyFromFile(key, &value)) {
    // Successfully read from the property file.
    // Update the cache and return the result.
    property_cache[key] = value;
    return value;
  } else {
    // Reading from the file is failed.
    // Add |key| into |undefined_keys|.
    // If the same |key| is passed to this method in future,
    // GetPropertyFromFile() will not be invoked
    // and |default_value| will be directly returned.
    undefined_keys.insert(key);
    return default_value;
  }
}

// static
bool AndroidUtil::GetPropertyFromFile(const string &key,
                                      string *output) {
  std::ifstream ifs(kBuildPropPath);
  if (!ifs) {
    return false;
  }
  string line;
  bool found = false;
  string lhs;
  string rhs;
  while (getline(ifs, line)) {
    if (!mozc::AndroidUtil::ParseLine(line, &lhs, &rhs)) {
      continue;
    }
    if (key == lhs) {
      found = true;
      output->swap(rhs);
      break;
    }
  }
  ifs.close();
  return found;
}

// Valid line's format : /[ \t]*([^#=][^=]*)=([^\r\n]*)[\r\n]*/
// $1 == Key
// $2 == Value
// android_util_test.cc has some samples.
//
// static
bool AndroidUtil::ParseLine(
    const string &line, string *lhs, string *rhs) {
  DCHECK(lhs);
  DCHECK(rhs);
  string tmp_line = line;
  mozc::Util::ChopReturns(&tmp_line);
  // Trim white spaces at the head.
  size_t line_start = tmp_line.find_first_not_of(" \t");
  if (line_start != string::npos) {
    tmp_line = tmp_line.substr(line_start);
  }
  if (tmp_line.empty() || tmp_line.at(0) == '#') {
    return false;
  }
  size_t delimiter_pos = tmp_line.find('=');
  if (delimiter_pos == string::npos) {
    return false;
  }
  *lhs = tmp_line.substr(0, delimiter_pos);
  *rhs = tmp_line.substr(delimiter_pos + 1);
  return !lhs->empty();
}

// static
JNIEnv *AndroidUtil::GetEnv(JavaVM *vm) {
  JNIEnv *env;
  jint result = vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6);
  if (result == JNI_OK) {
    return env;
  }
  LOG(ERROR) << "Critical error: VM env is not available.";
  // We cannot throw an exception because there is no env.
  return NULL;
}
}  // namespace mozc