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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.
#include "components/metrics/persisted_logs.h"
#include <string>
#include "base/base64.h"
#include "base/md5.h"
#include "base/metrics/histogram.h"
#include "base/prefs/pref_service.h"
#include "base/prefs/scoped_user_pref_update.h"
#include "base/sha1.h"
#include "base/timer/elapsed_timer.h"
#include "components/metrics/compression_utils.h"
namespace metrics {
namespace {
PersistedLogs::LogReadStatus MakeRecallStatusHistogram(
PersistedLogs::LogReadStatus status) {
UMA_HISTOGRAM_ENUMERATION("PrefService.PersistentLogRecallProtobufs",
status, PersistedLogs::END_RECALL_STATUS);
return status;
}
// Reads the value at |index| from |list_value| as a string and Base64-decodes
// it into |result|. Returns true on success.
bool ReadBase64String(const base::ListValue& list_value,
size_t index,
std::string* result) {
std::string base64_result;
if (!list_value.GetString(index, &base64_result))
return false;
return base::Base64Decode(base64_result, result);
}
// Base64-encodes |str| and appends the result to |list_value|.
void AppendBase64String(const std::string& str, base::ListValue* list_value) {
std::string base64_str;
base::Base64Encode(str, &base64_str);
list_value->AppendString(base64_str);
}
} // namespace
void PersistedLogs::LogHashPair::Init(const std::string& log_data) {
DCHECK(!log_data.empty());
if (!GzipCompress(log_data, &compressed_log_data)) {
NOTREACHED();
return;
}
UMA_HISTOGRAM_PERCENTAGE(
"UMA.ProtoCompressionRatio",
static_cast<int>(100 * compressed_log_data.size() / log_data.size()));
UMA_HISTOGRAM_CUSTOM_COUNTS(
"UMA.ProtoGzippedKBSaved",
static_cast<int>((log_data.size() - compressed_log_data.size()) / 1024),
1, 2000, 50);
hash = base::SHA1HashString(log_data);
}
PersistedLogs::PersistedLogs(PrefService* local_state,
const char* pref_name,
size_t min_log_count,
size_t min_log_bytes,
size_t max_log_size)
: local_state_(local_state),
pref_name_(pref_name),
min_log_count_(min_log_count),
min_log_bytes_(min_log_bytes),
max_log_size_(max_log_size != 0 ? max_log_size : static_cast<size_t>(-1)),
staged_log_index_(-1) {
DCHECK(local_state_);
// One of the limit arguments must be non-zero.
DCHECK(min_log_count_ > 0 || min_log_bytes_ > 0);
}
PersistedLogs::~PersistedLogs() {}
void PersistedLogs::SerializeLogs() const {
ListPrefUpdate update(local_state_, pref_name_);
WriteLogsToPrefList(update.Get());
}
PersistedLogs::LogReadStatus PersistedLogs::DeserializeLogs() {
return ReadLogsFromPrefList(*local_state_->GetList(pref_name_));
}
void PersistedLogs::StoreLog(const std::string& log_data) {
list_.push_back(LogHashPair());
list_.back().Init(log_data);
}
void PersistedLogs::StageLog() {
// CHECK, rather than DCHECK, because swap()ing with an empty list causes
// hard-to-identify crashes much later.
CHECK(!list_.empty());
DCHECK(!has_staged_log());
staged_log_index_ = list_.size() - 1;
DCHECK(has_staged_log());
}
void PersistedLogs::DiscardStagedLog() {
DCHECK(has_staged_log());
DCHECK_LT(static_cast<size_t>(staged_log_index_), list_.size());
list_.erase(list_.begin() + staged_log_index_);
staged_log_index_ = -1;
}
void PersistedLogs::WriteLogsToPrefList(base::ListValue* list_value) const {
list_value->Clear();
// Keep the most recent logs which are smaller than |max_log_size_|.
// We keep at least |min_log_bytes_| and |min_log_count_| of logs before
// discarding older logs.
size_t start = list_.size();
size_t saved_log_count = 0;
size_t bytes_used = 0;
for (; start > 0; --start) {
size_t log_size = list_[start - 1].compressed_log_data.length();
if (bytes_used >= min_log_bytes_ &&
saved_log_count >= min_log_count_) {
break;
}
// Oversized logs won't be persisted, so don't count them.
if (log_size > max_log_size_)
continue;
bytes_used += log_size;
++saved_log_count;
}
for (size_t i = start; i < list_.size(); ++i) {
size_t log_size = list_[i].compressed_log_data.length();
if (log_size > max_log_size_) {
UMA_HISTOGRAM_COUNTS("UMA.Large Accumulated Log Not Persisted",
static_cast<int>(log_size));
continue;
}
AppendBase64String(list_[i].compressed_log_data, list_value);
AppendBase64String(list_[i].hash, list_value);
}
}
PersistedLogs::LogReadStatus PersistedLogs::ReadLogsFromPrefList(
const base::ListValue& list_value) {
if (list_value.empty())
return MakeRecallStatusHistogram(LIST_EMPTY);
// For each log, there's two entries in the list (the data and the hash).
DCHECK_EQ(0U, list_value.GetSize() % 2);
const size_t log_count = list_value.GetSize() / 2;
// Resize |list_| ahead of time, so that values can be decoded directly into
// the elements of the list.
DCHECK(list_.empty());
list_.resize(log_count);
for (size_t i = 0; i < log_count; ++i) {
if (!ReadBase64String(list_value, i * 2, &list_[i].compressed_log_data) ||
!ReadBase64String(list_value, i * 2 + 1, &list_[i].hash)) {
list_.clear();
return MakeRecallStatusHistogram(LOG_STRING_CORRUPTION);
}
}
return MakeRecallStatusHistogram(RECALL_SUCCESS);
}
} // namespace metrics
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