From af9e6637c0fd154a6469a07913e233aad2b4d8f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Peter=20Bostr=C3=B6m?= <pbos@webrtc.org>
Date: Thu, 21 Jan 2016 16:56:52 +0100
Subject: [PATCH] Make rtc::CriticalSection lockable from f() const.

Removes the use of mutable rtc::CriticalSection across the code.

BUG=
R=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1611223002 .

Cr-Commit-Position: refs/heads/master@{#11342}
---
 webrtc/base/criticalsection.cc | 10 +++++-----
 webrtc/base/criticalsection.h  | 25 ++++++++++++++-----------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/webrtc/base/criticalsection.cc b/webrtc/base/criticalsection.cc
index 1f50c2355d..2c6b100a7d 100644
--- a/webrtc/base/criticalsection.cc
+++ b/webrtc/base/criticalsection.cc
@@ -36,7 +36,7 @@ CriticalSection::~CriticalSection() {
 #endif
 }
 
-void CriticalSection::Enter() EXCLUSIVE_LOCK_FUNCTION() {
+void CriticalSection::Enter() const EXCLUSIVE_LOCK_FUNCTION() {
 #if defined(WEBRTC_WIN)
   EnterCriticalSection(&crit_);
 #else
@@ -53,7 +53,7 @@ void CriticalSection::Enter() EXCLUSIVE_LOCK_FUNCTION() {
 #endif
 }
 
-bool CriticalSection::TryEnter() EXCLUSIVE_TRYLOCK_FUNCTION(true) {
+bool CriticalSection::TryEnter() const EXCLUSIVE_TRYLOCK_FUNCTION(true) {
 #if defined(WEBRTC_WIN)
   return TryEnterCriticalSection(&crit_) != FALSE;
 #else
@@ -71,7 +71,7 @@ bool CriticalSection::TryEnter() EXCLUSIVE_TRYLOCK_FUNCTION(true) {
   return true;
 #endif
 }
-void CriticalSection::Leave() UNLOCK_FUNCTION() {
+void CriticalSection::Leave() const UNLOCK_FUNCTION() {
   RTC_DCHECK(CurrentThreadIsOwner());
 #if defined(WEBRTC_WIN)
   LeaveCriticalSection(&crit_);
@@ -115,10 +115,10 @@ bool CriticalSection::IsLocked() const {
 #endif
 }
 
-CritScope::CritScope(CriticalSection* cs) : cs_(cs) { cs_->Enter(); }
+CritScope::CritScope(const CriticalSection* cs) : cs_(cs) { cs_->Enter(); }
 CritScope::~CritScope() { cs_->Leave(); }
 
-TryCritScope::TryCritScope(CriticalSection* cs)
+TryCritScope::TryCritScope(const CriticalSection* cs)
     : cs_(cs), locked_(cs->TryEnter()) {
   CS_DEBUG_CODE(lock_was_called_ = false);
 }
diff --git a/webrtc/base/criticalsection.h b/webrtc/base/criticalsection.h
index 5b3eaf5684..cc54eca1f0 100644
--- a/webrtc/base/criticalsection.h
+++ b/webrtc/base/criticalsection.h
@@ -41,14 +41,17 @@
 
 namespace rtc {
 
+// Locking methods (Enter, TryEnter, Leave)are const to permit protecting
+// members inside a const context without requiring mutable CriticalSections
+// everywhere.
 class LOCKABLE CriticalSection {
  public:
   CriticalSection();
   ~CriticalSection();
 
-  void Enter() EXCLUSIVE_LOCK_FUNCTION();
-  bool TryEnter() EXCLUSIVE_TRYLOCK_FUNCTION(true);
-  void Leave() UNLOCK_FUNCTION();
+  void Enter() const EXCLUSIVE_LOCK_FUNCTION();
+  bool TryEnter() const EXCLUSIVE_TRYLOCK_FUNCTION(true);
+  void Leave() const UNLOCK_FUNCTION();
 
   // Use only for RTC_DCHECKing.
   bool CurrentThreadIsOwner() const;
@@ -57,21 +60,21 @@ class LOCKABLE CriticalSection {
 
  private:
 #if defined(WEBRTC_WIN)
-  CRITICAL_SECTION crit_;
+  mutable CRITICAL_SECTION crit_;
 #elif defined(WEBRTC_POSIX)
-  pthread_mutex_t mutex_;
-  CS_DEBUG_CODE(pthread_t thread_);
-  CS_DEBUG_CODE(int recursion_count_);
+  mutable pthread_mutex_t mutex_;
+  CS_DEBUG_CODE(mutable pthread_t thread_);
+  CS_DEBUG_CODE(mutable int recursion_count_);
 #endif
 };
 
 // CritScope, for serializing execution through a scope.
 class SCOPED_LOCKABLE CritScope {
  public:
-  explicit CritScope(CriticalSection* cs) EXCLUSIVE_LOCK_FUNCTION(cs);
+  explicit CritScope(const CriticalSection* cs) EXCLUSIVE_LOCK_FUNCTION(cs);
   ~CritScope() UNLOCK_FUNCTION();
  private:
-  CriticalSection* const cs_;
+  const CriticalSection* const cs_;
   RTC_DISALLOW_COPY_AND_ASSIGN(CritScope);
 };
 
@@ -84,7 +87,7 @@ class SCOPED_LOCKABLE CritScope {
 // lock was taken. If you're not calling locked(), you're doing it wrong!
 class TryCritScope {
  public:
-  explicit TryCritScope(CriticalSection* cs);
+  explicit TryCritScope(const CriticalSection* cs);
   ~TryCritScope();
 #if defined(WEBRTC_WIN)
   _Check_return_ bool locked() const;
@@ -92,7 +95,7 @@ class TryCritScope {
   bool locked() const __attribute__ ((__warn_unused_result__));
 #endif
  private:
-  CriticalSection* const cs_;
+  const CriticalSection* const cs_;
   const bool locked_;
   CS_DEBUG_CODE(mutable bool lock_was_called_);
   RTC_DISALLOW_COPY_AND_ASSIGN(TryCritScope);