在某些Windows安装中，我们突然遇到智能卡api的问题。 调用SCardEstablishContext函数时似乎存在内存泄漏。 可以在控制台应用程序中重现该问题，其中包含可用的代码示例 http://www.pinvoke.net/default.aspx/winscard.scardestablishcontext
class Program
{
#region Win32
// WinSCard APIs to be imported.
[DllImport("WinScard.dll")]
static extern int SCardEstablishContext(uint dwScope,
IntPtr notUsed1,
IntPtr notUsed2,
out IntPtr phContext);
[DllImport("WinScard.dll")]
static extern int SCardReleaseContext(IntPtr phContext);
[DllImport("WinScard.dll")]
static extern int SCardConnect(IntPtr hContext,
string cReaderName,
uint dwShareMode,
uint dwPrefProtocol,
ref IntPtr phCard,
ref IntPtr ActiveProtocol);
[DllImport("WinScard.dll")]
static extern int SCardDisconnect(IntPtr hCard, int Disposition);
[DllImport("WinScard.dll", EntryPoint = "SCardListReadersA", CharSet = CharSet.Ansi)]
static extern int SCardListReaders(
IntPtr hContext,
byte[] mszGroups,
byte[] mszReaders,
ref UInt32 pcchReaders);
#endregion
static void Main(string[] args)
{
while (true)
{
SmartCardInserted();
System.Threading.Thread.Sleep(10);
}
}
internal static bool SmartCardInserted()
{
bool cardInserted = false;
IntPtr hContext = IntPtr.Zero;
try
{
List<string> readersList = new List<string>();
int ret = 0;
uint pcchReaders = 0;
int nullindex = -1;
char nullchar = (char)0;
// Establish context.
ret = SCardEstablishContext(2, IntPtr.Zero, IntPtr.Zero, out hContext);
// First call with 3rd parameter set to null gets readers buffer length.
ret = SCardListReaders(hContext, null, null, ref pcchReaders);
byte[] mszReaders = new byte[pcchReaders];
// Fill readers buffer with second call.
ret = SCardListReaders(hContext, null, mszReaders, ref pcchReaders);
// Populate List with readers.
ASCIIEncoding ascii = new ASCIIEncoding();
string currbuff = ascii.GetString(mszReaders);
int len = (int)pcchReaders;
if (len > 0)
{
while (currbuff[0] != nullchar)
{
nullindex = currbuff.IndexOf(nullchar); // Get null end character.
string reader = currbuff.Substring(0, nullindex);
readersList.Add(reader);
len = len - (reader.Length + 1);
currbuff = currbuff.Substring(nullindex + 1, len);
}
}
// We have list of readers, check for cards.
IntPtr phCard = IntPtr.Zero;
IntPtr ActiveProtocol = IntPtr.Zero;
int result = 0;
foreach (string readerName in readersList)
{
try
{
result = SCardConnect(hContext, readerName, 2, 3, ref phCard, ref ActiveProtocol);
if (result == 0)
{
cardInserted = true;
break;
}
}
finally
{
SCardDisconnect(phCard, 0);
}
}
}
finally
{
SCardReleaseContext(hContext);
}
return cardInserted;
}
}
为了测试，我们将方法SmartCardInserted（）称为无限循环，延迟时间小=＆gt;记忆不断增长，分配了新的小岛。
我们在运行Windows 10或Windows Server 2012的系统上看到此问题，但在Windows Server 2008上没有。
非常感谢任何想法！
答案 0 :(得分：5)
问题似乎已经在Windows 10的v1709中发布。重现该错误的代码最短是
while(true) {
ret = SCardEstablishContext(2, IntPtr.Zero, IntPtr.Zero, out hContext);
SCardReleaseContext(hContext);
}
每次建立和释放上下文时，它会泄漏~264字节的内存。
如果你在循环之外维护hContext并且只创建一个上下文，如果它是IntPtr.Zero你应该能够避免泄漏。然后，当您调用SCardListReaders时，检查是否返回SCARD_E_INVALID_HANDLE并使您的hContext无效。
class Program
{
#region Win32
// WinSCard APIs to be imported.
[DllImport("WinScard.dll")]
static extern int SCardEstablishContext(uint dwScope,
IntPtr notUsed1,
IntPtr notUsed2,
out IntPtr phContext);
[DllImport("WinScard.dll")]
static extern int SCardReleaseContext(IntPtr phContext);
[DllImport("WinScard.dll")]
static extern int SCardConnect(IntPtr hContext,
string cReaderName,
uint dwShareMode,
uint dwPrefProtocol,
ref IntPtr phCard,
ref IntPtr ActiveProtocol);
[DllImport("WinScard.dll")]
static extern int SCardDisconnect(IntPtr hCard, int Disposition);
[DllImport("WinScard.dll", EntryPoint = "SCardListReadersA", CharSet = CharSet.Ansi)]
static extern int SCardListReaders(
IntPtr hContext,
byte[] mszGroups,
byte[] mszReaders,
ref UInt32 pcchReaders);
#endregion
static void Main(string[] args)
{
IntPtr hContext = IntPtr.Zero;
while (true)
{
SmartCardInserted(hContext);
System.Threading.Thread.Sleep(10);
}
SCardReleaseContext(hContext);
}
internal static bool SmartCardInserted(IntPtr hContext)
{
bool cardInserted = false;
try
{
List<string> readersList = new List<string>();
int ret = 0;
uint pcchReaders = 0;
int nullindex = -1;
char nullchar = (char)0;
// Establish context.
if(hContext == IntPtr.Zero)
ret = SCardEstablishContext(2, IntPtr.Zero, IntPtr.Zero, out hContext);
// First call with 3rd parameter set to null gets readers buffer length.
ret = SCardListReaders(hContext, null, null, ref pcchReaders);
if(ret == 0x80100003) // SCARD_E_INVALID_HANDLE = 0x80100003, // The supplied handle was invalid
{
try
{
SCardReleaseContext(hContext);
}
catch {}
finally
{
hContext = IntPtr.Zero;
}
return false;
}
byte[] mszReaders = new byte[pcchReaders];
// Fill readers buffer with second call.
ret = SCardListReaders(hContext, null, mszReaders, ref pcchReaders);
// Populate List with readers.
ASCIIEncoding ascii = new ASCIIEncoding();
string currbuff = ascii.GetString(mszReaders);
int len = (int)pcchReaders;
if (len > 0)
{
while (currbuff[0] != nullchar)
{
nullindex = currbuff.IndexOf(nullchar); // Get null end character.
string reader = currbuff.Substring(0, nullindex);
readersList.Add(reader);
len = len - (reader.Length + 1);
currbuff = currbuff.Substring(nullindex + 1, len);
}
}
// We have list of readers, check for cards.
IntPtr phCard = IntPtr.Zero;
IntPtr ActiveProtocol = IntPtr.Zero;
int result = 0;
foreach (string readerName in readersList)
{
try
{
result = SCardConnect(hContext, readerName, 2, 3, ref phCard, ref ActiveProtocol);
if (result == 0)
{
cardInserted = true;
break;
}
}
finally
{
SCardDisconnect(phCard, 0);
}
}
}
return cardInserted;
}
}
在修复Winscard.dll API之前，这是一种解决方法。