Speed up field trial parser for large inputs
Change search for next separator to be linear in length of the string
(instead of potentially quadratic)
Reduce copying of std::string by switch to string_view
Throttle logging about unknown key.
Bug: b/204541739
Change-Id: I81d5cd4432966a0a5808077f9001bc62960e5e60
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/237500
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Fanny Linderborg <linderborg@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35330}
diff --git a/rtc_base/experiments/field_trial_parser.cc b/rtc_base/experiments/field_trial_parser.cc
index 8fc89ce..952250b 100644
--- a/rtc_base/experiments/field_trial_parser.cc
+++ b/rtc_base/experiments/field_trial_parser.cc
@@ -16,19 +16,12 @@
#include <type_traits>
#include <utility>
+#include "absl/strings/string_view.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_conversions.h"
namespace webrtc {
-namespace {
-
-int FindOrEnd(std::string str, size_t start, char delimiter) {
- size_t pos = str.find(delimiter, start);
- pos = (pos == std::string::npos) ? str.length() : pos;
- return static_cast<int>(pos);
-}
-} // namespace
FieldTrialParameterInterface::FieldTrialParameterInterface(std::string key)
: key_(key) {}
@@ -39,8 +32,8 @@
void ParseFieldTrial(
std::initializer_list<FieldTrialParameterInterface*> fields,
- std::string trial_string) {
- std::map<std::string, FieldTrialParameterInterface*> field_map;
+ absl::string_view trial_string) {
+ std::map<absl::string_view, FieldTrialParameterInterface*> field_map;
FieldTrialParameterInterface* keyless_field = nullptr;
for (FieldTrialParameterInterface* field : fields) {
field->MarkAsUsed();
@@ -60,18 +53,29 @@
field_map[field->key_] = field;
}
}
+ bool logged_unknown_key = false;
- size_t i = 0;
- while (i < trial_string.length()) {
- int val_end = FindOrEnd(trial_string, i, ',');
- int colon_pos = FindOrEnd(trial_string, i, ':');
- int key_end = std::min(val_end, colon_pos);
- int val_begin = key_end + 1;
- std::string key = trial_string.substr(i, key_end - i);
+ absl::string_view tail = trial_string;
+ while (!tail.empty()) {
+ size_t key_end = tail.find_first_of(",:");
+ absl::string_view key = tail.substr(0, key_end);
absl::optional<std::string> opt_value;
- if (val_end >= val_begin)
- opt_value = trial_string.substr(val_begin, val_end - val_begin);
- i = val_end + 1;
+ if (key_end == absl::string_view::npos) {
+ tail = "";
+ } else if (tail[key_end] == ':') {
+ tail = tail.substr(key_end + 1);
+ size_t value_end = tail.find(',');
+ opt_value.emplace(tail.substr(0, value_end));
+ if (value_end == absl::string_view::npos) {
+ tail = "";
+ } else {
+ tail = tail.substr(value_end + 1);
+ }
+ } else {
+ RTC_DCHECK_EQ(tail[key_end], ',');
+ tail = tail.substr(key_end + 1);
+ }
+
auto field = field_map.find(key);
if (field != field_map.end()) {
if (!field->second->Parse(std::move(opt_value))) {
@@ -79,7 +83,7 @@
<< "' in trial: \"" << trial_string << "\"";
}
} else if (!opt_value && keyless_field && !key.empty()) {
- if (!keyless_field->Parse(key)) {
+ if (!keyless_field->Parse(std::string(key))) {
RTC_LOG(LS_WARNING) << "Failed to read empty key field with value '"
<< key << "' in trial: \"" << trial_string << "\"";
}
@@ -87,14 +91,17 @@
// "_" is be used to prefix keys that are part of the string for
// debugging purposes but not neccessarily used.
// e.g. WebRTC-Experiment/param: value, _DebuggingString
- RTC_LOG(LS_INFO) << "No field with key: '" << key
- << "' (found in trial: \"" << trial_string << "\")";
- std::string valid_keys;
- for (const auto& f : field_map) {
- valid_keys += f.first;
- valid_keys += ", ";
+ if (!logged_unknown_key) {
+ RTC_LOG(LS_INFO) << "No field with key: '" << key
+ << "' (found in trial: \"" << trial_string << "\")";
+ std::string valid_keys;
+ for (const auto& f : field_map) {
+ valid_keys.append(f.first.data(), f.first.size());
+ valid_keys += ", ";
+ }
+ RTC_LOG(LS_INFO) << "Valid keys are: " << valid_keys;
+ logged_unknown_key = true;
}
- RTC_LOG(LS_INFO) << "Valid keys are: " << valid_keys;
}
}
diff --git a/rtc_base/experiments/field_trial_parser.h b/rtc_base/experiments/field_trial_parser.h
index 42535ed..c67ef54 100644
--- a/rtc_base/experiments/field_trial_parser.h
+++ b/rtc_base/experiments/field_trial_parser.h
@@ -18,6 +18,7 @@
#include <string>
#include <vector>
+#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
// Field trial parser functionality. Provides funcitonality to parse field trial
@@ -48,7 +49,7 @@
explicit FieldTrialParameterInterface(std::string key);
friend void ParseFieldTrial(
std::initializer_list<FieldTrialParameterInterface*> fields,
- std::string raw_string);
+ absl::string_view trial_string);
void MarkAsUsed() { used_ = true; }
virtual bool Parse(absl::optional<std::string> str_value) = 0;
@@ -65,7 +66,7 @@
// with extracted values if available.
void ParseFieldTrial(
std::initializer_list<FieldTrialParameterInterface*> fields,
- std::string raw_string);
+ absl::string_view trial_string);
// Specialize this in code file for custom types. Should return absl::nullopt if
// the given string cannot be properly parsed.
