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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_METRICS_PERSISTED_LOGS_H_
#define COMPONENTS_METRICS_PERSISTED_LOGS_H_
#include <string>
#include <vector>
#include "base/basictypes.h"
#include "base/logging.h"
#include "base/values.h"
class PrefService;
namespace metrics {
// Maintains a list of unsent logs that are written and restored from disk.
class PersistedLogs {
public:
// Used to produce a histogram that keeps track of the status of recalling
// persisted per logs.
enum LogReadStatus {
RECALL_SUCCESS, // We were able to correctly recall a persisted log.
LIST_EMPTY, // Attempting to recall from an empty list.
LIST_SIZE_MISSING, // Failed to recover list size using GetAsInteger().
LIST_SIZE_TOO_SMALL, // Too few elements in the list (less than 3).
LIST_SIZE_CORRUPTION, // List size is not as expected.
LOG_STRING_CORRUPTION, // Failed to recover log string using GetAsString().
CHECKSUM_CORRUPTION, // Failed to verify checksum.
CHECKSUM_STRING_CORRUPTION, // Failed to recover checksum string using
// GetAsString().
DECODE_FAIL, // Failed to decode log.
DEPRECATED_XML_PROTO_MISMATCH, // The XML and protobuf logs have
// inconsistent data.
END_RECALL_STATUS // Number of bins to use to create the histogram.
};
// Constructs a PersistedLogs that stores data in |local_state| under the
// preference |pref_name|.
// Calling code is responsible for ensuring that the lifetime of |local_state|
// is longer than the lifetime of PersistedLogs.
//
// When saving logs to disk, stores either the first |min_log_count| logs, or
// at least |min_log_bytes| bytes of logs, whichever is greater.
//
// If the optional |max_log_size| parameter is non-zero, all logs larger than
// that limit will be skipped when writing to disk.
PersistedLogs(PrefService* local_state,
const char* pref_name,
size_t min_log_count,
size_t min_log_bytes,
size_t max_log_size);
~PersistedLogs();
// Write list to storage.
void SerializeLogs() const;
// Reads the list from the preference.
LogReadStatus DeserializeLogs();
// Adds a log to the list.
void StoreLog(const std::string& log_data);
// Stages the most recent log. The staged_log will remain the same even if
// additional logs are added.
void StageLog();
// Remove the staged log.
void DiscardStagedLog();
// True if a log has been staged.
bool has_staged_log() const { return staged_log_index_ != -1; }
// Returns the element in the front of the list.
const std::string& staged_log() const {
DCHECK(has_staged_log());
return list_[staged_log_index_].compressed_log_data;
}
// Returns the element in the front of the list.
const std::string& staged_log_hash() const {
DCHECK(has_staged_log());
return list_[staged_log_index_].hash;
}
// The number of elements currently stored.
size_t size() const { return list_.size(); }
// True if there are no stored logs.
bool empty() const { return list_.empty(); }
private:
// Writes the list to the ListValue.
void WriteLogsToPrefList(base::ListValue* list) const;
// Reads the list from the ListValue.
LogReadStatus ReadLogsFromPrefList(const base::ListValue& list);
// A weak pointer to the PrefService object to read and write the preference
// from. Calling code should ensure this object continues to exist for the
// lifetime of the PersistedLogs object.
PrefService* local_state_;
// The name of the preference to serialize logs to/from.
const char* pref_name_;
// We will keep at least this |min_log_count_| logs or |min_log_bytes_| bytes
// of logs, whichever is greater, when writing to disk. These apply after
// skipping logs greater than |max_log_size_|.
const size_t min_log_count_;
const size_t min_log_bytes_;
// Logs greater than this size will not be written to disk.
const size_t max_log_size_;
struct LogHashPair {
// Initializes the members based on uncompressed |log_data|.
void Init(const std::string& log_data);
// Compressed log data - a serialized protobuf that's been gzipped.
std::string compressed_log_data;
// The SHA1 hash of log, stored to catch errors from memory corruption.
std::string hash;
};
// A list of all of the stored logs, stored with SHA1 hashes to check for
// corruption while they are stored in memory.
std::vector<LogHashPair> list_;
// The index and type of the log staged for upload. If nothing has been
// staged, the index will be -1.
int staged_log_index_;
DISALLOW_COPY_AND_ASSIGN(PersistedLogs);
};
} // namespace metrics
#endif // COMPONENTS_METRICS_PERSISTED_LOGS_H_
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