From 11fab41c3638e9368c5589c4092af0b0e29ff054 Mon Sep 17 00:00:00 2001
From: Ilya Kitaev <mbg033@gmail.com>
Date: Thu, 6 Oct 2016 23:25:43 +0300
Subject: [PATCH] libwallet_api: TransactionHistory: read/write
 syncchronization

---
 src/wallet/api/transaction_history.cpp | 31 ++++++++++++++++----------
 src/wallet/api/transaction_history.h   |  4 ++--
 2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/src/wallet/api/transaction_history.cpp b/src/wallet/api/transaction_history.cpp
index 5f99750d5..df495591f 100644
--- a/src/wallet/api/transaction_history.cpp
+++ b/src/wallet/api/transaction_history.cpp
@@ -60,12 +60,24 @@ TransactionHistoryImpl::~TransactionHistoryImpl()
 
 int TransactionHistoryImpl::count() const
 {
-    boost::lock_guard<boost::mutex> guarg(m_historyMutex);
-    return m_history.size();
+    boost::shared_lock<boost::shared_mutex> lock(m_historyMutex);
+    int result = m_history.size();
+    return result;
+}
+
+TransactionInfo *TransactionHistoryImpl::transaction(int index) const
+{
+    boost::shared_lock<boost::shared_mutex> lock(m_historyMutex);
+    // sanity check
+    if (index < 0)
+        return nullptr;
+    unsigned index_ = static_cast<unsigned>(index);
+    return index_ < m_history.size() ? m_history[index_] : nullptr;
 }
 
 TransactionInfo *TransactionHistoryImpl::transaction(const std::string &id) const
 {
+    boost::shared_lock<boost::shared_mutex> lock(m_historyMutex);
     auto itr = std::find_if(m_history.begin(), m_history.end(),
                             [&](const TransactionInfo * ti) {
         return ti->hash() == id;
@@ -75,13 +87,16 @@ TransactionInfo *TransactionHistoryImpl::transaction(const std::string &id) cons
 
 std::vector<TransactionInfo *> TransactionHistoryImpl::getAll() const
 {
+    boost::shared_lock<boost::shared_mutex> lock(m_historyMutex);
     return m_history;
 }
 
 void TransactionHistoryImpl::refresh()
 {
     // multithreaded access:
-    boost::lock_guard<boost::mutex> guarg(m_historyMutex);
+    // boost::lock_guard<boost::mutex> guarg(m_historyMutex);
+    // for "write" access, locking exclusively
+    boost::unique_lock<boost::shared_mutex> lock(m_historyMutex);
 
     // TODO: configurable values;
     uint64_t min_height = 0;
@@ -190,16 +205,8 @@ void TransactionHistoryImpl::refresh()
         ti->m_timestamp = pd.m_timestamp;
         m_history.push_back(ti);
     }
-
 }
 
-TransactionInfo *TransactionHistoryImpl::transaction(int index) const
-{
-    // sanity check
-    if (index < 0)
-        return nullptr;
-    unsigned index_ = static_cast<unsigned>(index);
-    return index_ < m_history.size() ? m_history[index_] : nullptr;
-}
+
 
 }
diff --git a/src/wallet/api/transaction_history.h b/src/wallet/api/transaction_history.h
index 04db7e8e1..1b6617ead 100644
--- a/src/wallet/api/transaction_history.h
+++ b/src/wallet/api/transaction_history.h
@@ -29,7 +29,7 @@
 // Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
 
 #include "wallet/wallet2_api.h"
-#include <boost/thread/mutex.hpp>
+#include <boost/thread/shared_mutex.hpp>
 
 namespace Bitmonero {
 
@@ -52,7 +52,7 @@ private:
     // TransactionHistory is responsible of memory management
     std::vector<TransactionInfo*> m_history;
     WalletImpl *m_wallet;
-    mutable boost::mutex        m_historyMutex;
+    mutable boost::shared_mutex   m_historyMutex;
 };
 
 }