Remove double map fetch in GetFlag*ValueForInstances

Calling `find` first then `operator[]` traverses the map twice.

go/totw/202

Bug: b/470453334

Author: Databean

base/cvd/cuttlefish/host/commands/assemble_cvd/BUILD.bazel

@@ -306,6 +306,7 @@ cf_cc_library(
         "//cuttlefish/host/libs/vhal_proxy_server",
         "//cuttlefish/host/libs/vm_manager",
         "//libbase",
+        "@abseil-cpp//absl/strings",
         "@fmt",
         "@fruit",
         "@gflags",

base/cvd/cuttlefish/host/commands/assemble_cvd/flags.cc

@@ -27,15 +27,16 @@
 #include <unordered_map>
 #include <vector>
 
-#include <android-base/file.h>
-#include <android-base/logging.h>
-#include <android-base/parseint.h>
-#include <android-base/strings.h>
-#include <fmt/format.h>
-#include <fruit/fruit.h>
-#include <gflags/gflags.h>
-#include <json/json.h>
-#include <json/writer.h>
+#include "absl/strings/str_split.h"
+#include "android-base/file.h"
+#include "android-base/logging.h"
+#include "android-base/parseint.h"
+#include "android-base/strings.h"
+#include "fmt/format.h"
+#include "fruit/fruit.h"
+#include "gflags/gflags.h"
+#include "json/json.h"
+#include "json/writer.h"
 
 #include "cuttlefish/common/libs/utils/base64.h"
 #include "cuttlefish/common/libs/utils/container.h"
@@ -177,20 +178,23 @@ std::map<std::string, std::string> CurrentFlagsToDefaultValue() {
 }
 
 Result<std::vector<bool>> GetFlagBoolValueForInstances(
-    const std::string& flag_values, int32_t instances_size, const std::string& flag_name,
-    std::map<std::string, std::string>& name_to_default_value) {
-  std::vector<std::string> flag_vec = android::base::Split(flag_values, ",");
+    const std::string& flag_values, int32_t instances_size,
+    const std::string& flag_name,
+    const std::map<std::string, std::string>& name_to_default_value) {
+  std::vector<std::string_view> flag_vec = absl::StrSplit(flag_values, ",");
   std::vector<bool> value_vec(instances_size);
 
-  CF_EXPECT(name_to_default_value.find(flag_name) != name_to_default_value.end());
-  std::vector<std::string> default_value_vec =  android::base::Split(name_to_default_value[flag_name], ",");
+  auto default_value_it = name_to_default_value.find(flag_name);
+  CF_EXPECT(default_value_it != name_to_default_value.end());
+  std::vector<std::string_view> default_value_vec =
+      absl::StrSplit(default_value_it->second, ",");
 
   for (int instance_index=0; instance_index<instances_size; instance_index++) {
     if (instance_index >= flag_vec.size()) {
       value_vec[instance_index] = value_vec[0];
     } else {
       if (flag_vec[instance_index] == "unset" || flag_vec[instance_index] == "\"unset\"") {
-        std::string default_value = default_value_vec[0];
+        std::string_view default_value = default_value_vec[0];
         if (instance_index < default_value_vec.size()) {
           default_value = default_value_vec[instance_index];
         }
@@ -204,13 +208,16 @@ Result<std::vector<bool>> GetFlagBoolValueForInstances(
 }
 
 Result<std::vector<int>> GetFlagIntValueForInstances(
-    const std::string& flag_values, int32_t instances_size, const std::string& flag_name,
-    std::map<std::string, std::string>& name_to_default_value) {
-  std::vector<std::string> flag_vec = android::base::Split(flag_values, ",");
+    const std::string& flag_values, int32_t instances_size,
+    const std::string& flag_name,
+    const std::map<std::string, std::string>& name_to_default_value) {
+  std::vector<std::string> flag_vec = absl::StrSplit(flag_values, ",");
   std::vector<int> value_vec(instances_size);
 
-  CF_EXPECT(name_to_default_value.find(flag_name) != name_to_default_value.end());
-  std::vector<std::string> default_value_vec =  android::base::Split(name_to_default_value[flag_name], ",");
+  auto default_value_it = name_to_default_value.find(flag_name);
+  CF_EXPECT(default_value_it != name_to_default_value.end());
+  std::vector<std::string> default_value_vec =
+      absl::StrSplit(default_value_it->second, ",");
 
   for (int instance_index=0; instance_index<instances_size; instance_index++) {
     if (instance_index >= flag_vec.size()) {
@@ -237,19 +244,22 @@ Result<std::vector<int>> GetFlagIntValueForInstances(
 
 Result<std::vector<std::string>> GetFlagStrValueForInstances(
     const std::string& flag_values, int32_t instances_size,
-    const std::string& flag_name, std::map<std::string, std::string>& name_to_default_value) {
-  std::vector<std::string> flag_vec = android::base::Split(flag_values, ",");
+    const std::string& flag_name,
+    const std::map<std::string, std::string>& name_to_default_value) {
+  std::vector<std::string_view> flag_vec = absl::StrSplit(flag_values, ",");
   std::vector<std::string> value_vec(instances_size);
 
-  CF_EXPECT(name_to_default_value.find(flag_name) != name_to_default_value.end());
-  std::vector<std::string> default_value_vec =  android::base::Split(name_to_default_value[flag_name], ",");
+  auto default_value_it = name_to_default_value.find(flag_name);
+  CF_EXPECT(default_value_it != name_to_default_value.end());
+  std::vector<std::string_view> default_value_vec =
+      absl::StrSplit(default_value_it->second, ",");
 
   for (int instance_index=0; instance_index<instances_size; instance_index++) {
     if (instance_index >= flag_vec.size()) {
       value_vec[instance_index] = value_vec[0];
     } else {
       if (flag_vec[instance_index] == "unset" || flag_vec[instance_index] == "\"unset\"") {
-        std::string default_value = default_value_vec[0];
+        std::string_view default_value = default_value_vec[0];
         if (instance_index < default_value_vec.size()) {
           default_value = default_value_vec[instance_index];
         }