stdin

stdin

From e71bfae7f3a64f152cf7de9878f31e38b468ce1f Mon Sep 17 00:00:00 2001
From: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
Date: Thu, 17 Dec 2015 23:05:19 +0100
Subject: [PATCH] lots of fixes lol

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
---
 foo.cc | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/foo.cc b/foo.cc
index 3a83092..3fe87de 100644
--- a/foo.cc
+++ b/foo.cc
@@ -23,19 +23,21 @@ private:
     static Bank*        global_instance;
            unsigned int accounts[4];
            mutex        bank_lock;
+           unsigned int do_get_balance(unsigned int account_id);
+           void         do_set_balance(unsigned int account_id, unsigned int amount);
     Bank();
 };
 
-Bank* Bank::global_instance = 0;
+Bank* Bank::global_instance = nullptr;
 
 // Singleton instance of the bank
 Bank* Bank::instance() {
-    if (global_instance == 0) {
-       // avoid multiple creations of a bank instance
-       global_lock.lock();
+    // avoid multiple creations of a bank instance
+    global_lock.lock();
+    if (global_instance == nullptr) {
        global_instance = new Bank;
-       global_lock.unlock();
     }
+    global_lock.unlock();
     return global_instance;
 }
 
@@ -50,30 +52,40 @@ Bank::Bank() {
 unsigned int Bank::get_balance(unsigned int account_id) {
     // the lock_guard releases the lock when it gets out of scope
     lock_guard<mutex> lock(bank_lock);
+    return do_get_balance(account_id);
+}
+
+unsigned int Bank::do_get_balance(unsigned int account_id) {
     random_wait();
     return accounts[account_id];
 }
 
 /* sets the current balance for account_id */
 void Bank::set_balance(unsigned int account_id, unsigned int amount) {
-    // an account should never have a negative balance
-    assert(amount >= 0);
     lock_guard<mutex> lock(bank_lock);
+    do_set_balance(account_id, amount);
+}
+
+void Bank::do_set_balance(unsigned int account_id, unsigned int amount) {
+    // an account should never have a negative balance
     random_wait();
     accounts[account_id] = amount;
 }
 
 /* transfers the specified amount from account_id_1 to account_id_2 */
 void Bank::transfer(unsigned int account_id_1, unsigned int account_id_2, unsigned int amount) {
-    unsigned int balance_1 = get_balance(account_id_1);
+    lock_guard<mutex> lock(bank_lock);
+    unsigned int balance_1 = do_get_balance(account_id_1);
+    // ensure we have enough founds
+    assert(balance_1 > amount);
     random_wait();
-    unsigned int balance_2 = get_balance(account_id_2);
+    unsigned int balance_2 = do_get_balance(account_id_2);
 
     random_wait();
 
-    set_balance(account_id_1, balance_1 - amount);
+    do_set_balance(account_id_1, balance_1 - amount);
     random_wait();
-    set_balance(account_id_2, balance_2 + amount);
+    do_set_balance(account_id_2, balance_2 + amount);
 }
 
 void f1() {
-- 
2.6.4