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// Copyright 2014 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <string>
#include <vector>
namespace metrics {
class MetricSample;
// Metrics helpers to serialize and deserialize metrics collected by
// ChromeOS.
namespace SerializationUtils {
// Deserializes a sample passed as a string and return a sample.
// The return value will either be a std::unique_ptr to a Metric sample (if the
// deserialization was successful) or a NULL std::unique_ptr.
MetricSample ParseSample(const std::string& sample);
// Reads samples from a file, and modifies the file to reflect the samples
// processed. If all samples are read, truncates the file to zero size and
// returns true. If sample_batch_max_length is exceeded when reading a batch of
// samples, changes the file to logically contain only the remaining samples.
// Returns false if samples are left for further processing, true in all other
// cases (including errors).
bool ReadAndTruncateMetricsFromFile(const std::string& filename,
std::vector<MetricSample>* metrics,
size_t sample_batch_max_length);
// Serializes a vector of samples and writes them to filename.
// The format for each sample is:
// message_size, serialized_message
// where
// * message_size is the total length of the message (message_size +
// serialized_message) on 4 bytes
// * serialized_message is the serialized version of sample (using ToString)
// NB: the file will never leave the device so message_size will be written
// with the architecture's endianness.
bool WriteMetricsToFile(const std::vector<MetricSample>& samples,
const std::string& filename);
// Maximum length of a serialized message.
static const size_t kMessageMaxLength = 1024;
// Maximum size of serialized messages that we will read and upload in one
// pass. If a device does not have connectivity for a long time, a large
// number of messages can accumulate. Without this limit, the large number of
// messages can put strain on resources (such as RAM for the metrics daemon's
// heap) when connectivity is restored and the upload is attempted.
static const size_t kSampleBatchMaxLength = 10 * 1024 * 1024;
} // namespace SerializationUtils
} // namespace metrics