Linux: Try to minimize copying of string information when reading /proc data.

base/process_util_linux.cc

Index: base/process_util_linux.cc
diff --git a/base/process_util_linux.cc b/base/process_util_linux.cc
index 2f433d984eb628dbdeee3d6f711d303939ceb4ee..e4a24e75033765d7985afdbc037c1f9f40637317 100644
--- a/base/process_util_linux.cc
+++ b/base/process_util_linux.cc
@@ -123,18 +123,18 @@ ProcessId GetParentProcessId(ProcessHandle process) {
 
   StringTokenizer tokenizer(status, ":\n");
   ParsingState state = KEY_NAME;
-  std::string last_key_name;
+  StringPiece last_key_name;
   while (tokenizer.GetNext()) {
     switch (state) {
       case KEY_NAME:
-        last_key_name = tokenizer.token();
+        last_key_name = tokenizer.token_piece();
         state = KEY_VALUE;
         break;
       case KEY_VALUE:
         DCHECK(!last_key_name.empty());
         if (last_key_name == "PPid") {
           int ppid;
-          base::StringToInt(tokenizer.token(), &ppid);
+          base::StringToInt(tokenizer.token_piece(), &ppid);
           return ppid;
         }
         state = KEY_NAME;
@@ -380,12 +380,12 @@ bool ProcessMetrics::GetWorkingSetKBytes(WorkingSetKBytes* ws_usage) const {
           }
           if (last_key_name.starts_with(private_prefix)) {
             int cur;
-            base::StringToInt(tokenizer.token(), &cur);
+            base::StringToInt(tokenizer.token_piece(), &cur);
             private_kb += cur;
           } else if (last_key_name.starts_with(pss_prefix)) {
             have_pss = true;
             int cur;
-            base::StringToInt(tokenizer.token(), &cur);
+            base::StringToInt(tokenizer.token_piece(), &cur);
             pss_kb += cur;
           }
           state = KEY_NAME;
@@ -490,26 +490,26 @@ bool ProcessMetrics::GetIOCounters(IoCounters* io_counters) const {
 
   StringTokenizer tokenizer(proc_io_contents, ": \n");
   ParsingState state = KEY_NAME;
-  std::string last_key_name;
+  StringPiece last_key_name;
   while (tokenizer.GetNext()) {
     switch (state) {
       case KEY_NAME:
-        last_key_name = tokenizer.token();
+        last_key_name = tokenizer.token_piece();
         state = KEY_VALUE;
         break;
       case KEY_VALUE:
         DCHECK(!last_key_name.empty());
         if (last_key_name == "syscr") {
-          base::StringToInt64(tokenizer.token(),
+          base::StringToInt64(tokenizer.token_piece(),
               reinterpret_cast<int64*>(&(*io_counters).ReadOperationCount));
         } else if (last_key_name == "syscw") {
-          base::StringToInt64(tokenizer.token(),
+          base::StringToInt64(tokenizer.token_piece(),
               reinterpret_cast<int64*>(&(*io_counters).WriteOperationCount));
         } else if (last_key_name == "rchar") {
-          base::StringToInt64(tokenizer.token(),
+          base::StringToInt64(tokenizer.token_piece(),
               reinterpret_cast<int64*>(&(*io_counters).ReadTransferCount));
         } else if (last_key_name == "wchar") {
-          base::StringToInt64(tokenizer.token(),
+          base::StringToInt64(tokenizer.token_piece(),
               reinterpret_cast<int64*>(&(*io_counters).WriteTransferCount));
         }
         state = KEY_NAME;