逐步解說：在啟用 COM 的應用程式中使用並行執行階段
本檔示範如何在使用元件物件模型 （COM） 的應用程式中使用並行執行時間。
必要條件
開始本逐步解說之前，請先閱讀下列檔：
如需 COM 的詳細資訊，請參閱 元件物件模型 （COM） 。
管理 COM 程式庫的存留期
雖然使用 COM 搭配並行執行時間遵循與任何其他並行機制相同的原則，但下列指導方針可協助您有效地使用這些程式庫。
執行緒必須先呼叫 CoInitializeEx ，才能使用 COM 程式庫。
只要執行緒為每個呼叫提供相同的引數，執行緒就可以呼叫
CoInitializeEx多次。對於每個 呼叫
CoInitializeEx，執行緒也必須呼叫 CoUninitialize 。 換句話說，對 和CoUninitialize的CoInitializeEx呼叫必須平衡。若要從一個執行緒 Apartment 切換到另一個執行緒，執行緒必須先完全釋放 COM 程式庫，才能使用新的執行緒規格呼叫
CoInitializeEx。
當您搭配並行執行時間使用 COM 時，適用其他 COM 原則。 例如，在單一執行緒 Apartment 中建立物件的應用程式，並將該物件封送處理至另一個 Apartment 的應用程式也必須提供訊息迴圈來處理傳入訊息。 也請記住，在 Apartment 之間封送處理物件可能會降低效能。
搭配平行模式程式庫使用 COM
例如，當您在平行模式程式庫 （PPL） 中搭配元件使用 COM 時，請在每個工作或反復專案期間使用 COM 程式庫之前呼叫 CoInitializeEx ，並在每個工作或反復專案完成之前呼叫 CoUninitialize 。 下列範例示範如何使用並行：：structured_task_group 物件來管理 COM 程式庫 的存留期。
structured_task_group tasks;
// Create and run a task.
auto task = make_task([] {
// Initialize the COM library on the current thread.
CoInitializeEx(NULL, COINIT_MULTITHREADED);
// TODO: Perform task here.
// Free the COM library.
CoUninitialize();
});
tasks.run(task);
// TODO: Run additional tasks here.
// Wait for the tasks to finish.
tasks.wait();
當工作或平行演算法取消或工作主體擲回例外狀況時，您必須確定已正確釋放 COM 程式庫。 若要保證工作在結束之前呼叫 CoUninitialize ，請使用 try-finally 區塊或 資源擷取是初始化 （RAII） 模式。 下列範例會使用 try-finally 區塊，在工作完成或取消時，或擲回例外狀況時釋放 COM 程式庫。
structured_task_group tasks;
// Create and run a task.
auto task = make_task([] {
bool coinit = false;
__try {
// Initialize the COM library on the current thread.
CoInitializeEx(NULL, COINIT_MULTITHREADED);
coinit = true;
// TODO: Perform task here.
}
__finally {
// Free the COM library.
if (coinit)
CoUninitialize();
}
});
tasks.run(task);
// TODO: Run additional tasks here.
// Wait for the tasks to finish.
tasks.wait();
下列範例會使用 RAII 模式來定義 CCoInitializer 類別，以管理指定範圍內 COM 程式庫的存留期。
// An exception-safe wrapper class that manages the lifetime
// of the COM library in a given scope.
class CCoInitializer
{
public:
explicit CCoInitializer(DWORD dwCoInit = COINIT_APARTMENTTHREADED)
: _coinitialized(false)
{
// Initialize the COM library on the current thread.
HRESULT hr = CoInitializeEx(NULL, dwCoInit);
if (SUCCEEDED(hr))
_coinitialized = true;
}
~CCoInitializer()
{
// Free the COM library.
if (_coinitialized)
CoUninitialize();
}
private:
// Flags whether COM was properly initialized.
bool _coinitialized;
// Hide copy constructor and assignment operator.
CCoInitializer(const CCoInitializer&);
CCoInitializer& operator=(const CCoInitializer&);
};
您可以使用 類別 CCoInitializer ，在工作結束時自動釋放 COM 程式庫，如下所示。
structured_task_group tasks;
// Create and run a task.
auto task = make_task([] {
// Enable COM for the lifetime of the task.
CCoInitializer coinit(COINIT_MULTITHREADED);
// TODO: Perform task here.
// The CCoInitializer object frees the COM library
// when the task exits.
});
tasks.run(task);
// TODO: Run additional tasks here.
// Wait for the tasks to finish.
tasks.wait();
如需並行執行時間中取消的詳細資訊，請參閱 PPL 中的取消。
搭配非同步代理程式使用 COM
當您搭配非同步代理程式使用 COM 時， CoInitializeEx 請在代理程式的 concurrency：：agent：：run 方法中使用 COM 程式庫之前呼叫 。 然後在方法傳回之前 run 呼叫 CoUninitialize 。 請勿在代理程式的建構函式或解構函式中使用 COM 管理常式，也不會覆寫 concurrency：：agent：：start 或 concurrency：：agent：:d one 方法，因為這些方法是從方法不同的執行緒 run 呼叫。
下列範例示範名為 CCoAgent 的基本代理程式類別，該類別會在 方法中 run 管理 COM 程式庫。
class CCoAgent : public agent
{
protected:
void run()
{
// Initialize the COM library on the current thread.
CoInitializeEx(NULL, COINIT_MULTITHREADED);
// TODO: Perform work here.
// Free the COM library.
CoUninitialize();
// Set the agent to the finished state.
done();
}
};
本逐步解說稍後會提供完整的範例。
搭配輕量型工作使用 COM
工作排程器 檔 描述並行執行時間中輕量型工作的角色。 您可以使用 COM 搭配輕量型工作，就像您在 Windows API 中傳遞至 CreateThread 函式的任何執行緒常式一樣。 下列範例會顯示這一點。
// A basic lightweight task that you schedule directly from a
// Scheduler or ScheduleGroup object.
void ThreadProc(void* data)
{
// Initialize the COM library on the current thread.
CoInitializeEx(NULL, COINIT_MULTITHREADED);
// TODO: Perform work here.
// Free the COM library.
CoUninitialize();
}
啟用 COM 的應用程式範例
本節顯示一個完整的 COM 啟用應用程式，該應用程式會使用 IScriptControl 介面來執行計算第 n 個 Fibonacci 數位的腳本。 此範例會先從主執行緒呼叫腳本，然後使用 PPL 和代理程式同時呼叫腳本。
請考慮下列 Helper 函式， RunScriptProcedure 其會呼叫 物件中的 IScriptControl 程式。
// Calls a procedure in an IScriptControl object.
template<size_t ArgCount>
_variant_t RunScriptProcedure(IScriptControlPtr pScriptControl,
_bstr_t& procedureName, array<_variant_t, ArgCount>& arguments)
{
// Create a 1-dimensional, 0-based safe array.
SAFEARRAYBOUND rgsabound[] = { ArgCount, 0 };
CComSafeArray<VARIANT> sa(rgsabound, 1U);
// Copy the arguments to the safe array.
LONG lIndex = 0;
for_each(begin(arguments), end(arguments), [&](_variant_t& arg) {
HRESULT hr = sa.SetAt(lIndex, arg);
if (FAILED(hr))
throw hr;
++lIndex;
});
// Call the procedure in the script.
return pScriptControl->Run(procedureName, &sa.m_psa);
}
函 wmain 式會 IScriptControl 建立 物件、將腳本程式碼新增至該物件，以計算第 n 個 Fibonacci 數位，然後呼叫 函 RunScriptProcedure 式來執行該腳本。
int wmain()
{
HRESULT hr;
// Enable COM on this thread for the lifetime of the program.
CCoInitializer coinit(COINIT_MULTITHREADED);
// Create the script control.
IScriptControlPtr pScriptControl(__uuidof(ScriptControl));
// Set script control properties.
pScriptControl->Language = "JScript";
pScriptControl->AllowUI = TRUE;
// Add script code that computes the nth Fibonacci number.
hr = pScriptControl->AddCode(
"function fib(n) { if (n<2) return n; else return fib(n-1) + fib(n-2); }" );
if (FAILED(hr))
return hr;
// Test the script control by computing the 15th Fibonacci number.
wcout << endl << L"Main Thread:" << endl;
LONG lValue = 15;
array<_variant_t, 1> args = { _variant_t(lValue) };
_variant_t result = RunScriptProcedure(
pScriptControl,
_bstr_t("fib"),
args);
// Print the result.
wcout << L"fib(" << lValue << L") = " << result.lVal << endl;
return S_OK;
}
從 PPL 呼叫腳本
下列函 ParallelFibonacci 式會 使用 concurrency：:p arallel_for 演算法平行呼叫腳本。 此函式會 CCoInitializer 使用 類別來管理工作每次反覆運算期間 COM 程式庫的存留期。
// Computes multiple Fibonacci numbers in parallel by using
// the parallel_for algorithm.
HRESULT ParallelFibonacci(IScriptControlPtr pScriptControl)
{
try {
parallel_for(10L, 20L, [&pScriptControl](LONG lIndex)
{
// Enable COM for the lifetime of the task.
CCoInitializer coinit(COINIT_MULTITHREADED);
// Call the helper function to run the script procedure.
array<_variant_t, 1> args = { _variant_t(lIndex) };
_variant_t result = RunScriptProcedure(
pScriptControl,
_bstr_t("fib"),
args);
// Print the result.
wstringstream ss;
ss << L"fib(" << lIndex << L") = " << result.lVal << endl;
wcout << ss.str();
});
}
catch (HRESULT hr) {
return hr;
}
return S_OK;
}
若要搭配範例使用 函 ParallelFibonacci 式，請在函式傳回之前 wmain 新增下列程式碼。
// Use the parallel_for algorithm to compute multiple
// Fibonacci numbers in parallel.
wcout << endl << L"Parallel Fibonacci:" << endl;
if (FAILED(hr = ParallelFibonacci(pScriptControl)))
return hr;
從代理程式呼叫腳本
下列範例顯示 類別 FibonacciScriptAgent ，其會呼叫腳本程式來計算第 n 個 Fibonacci 數位。 類別 FibonacciScriptAgent 會使用訊息傳遞至腳本函式，以從主要程式接收輸入值。 方法 run 會管理整個工作的 COM 程式庫存留期。
// A basic agent that calls a script procedure to compute the
// nth Fibonacci number.
class FibonacciScriptAgent : public agent
{
public:
FibonacciScriptAgent(IScriptControlPtr pScriptControl, ISource<LONG>& source)
: _pScriptControl(pScriptControl)
, _source(source) { }
public:
// Retrieves the result code.
HRESULT GetHRESULT()
{
return receive(_result);
}
protected:
void run()
{
// Initialize the COM library on the current thread.
CoInitializeEx(NULL, COINIT_MULTITHREADED);
// Read values from the message buffer until
// we receive the sentinel value.
LONG lValue;
while ((lValue = receive(_source)) != Sentinel)
{
try {
// Call the helper function to run the script procedure.
array<_variant_t, 1> args = { _variant_t(lValue) };
_variant_t result = RunScriptProcedure(
_pScriptControl,
_bstr_t("fib"),
args);
// Print the result.
wstringstream ss;
ss << L"fib(" << lValue << L") = " << result.lVal << endl;
wcout << ss.str();
}
catch (HRESULT hr) {
send(_result, hr);
break;
}
}
// Set the result code (does nothing if a value is already set).
send(_result, S_OK);
// Free the COM library.
CoUninitialize();
// Set the agent to the finished state.
done();
}
public:
// Signals the agent to terminate.
static const LONG Sentinel = 0L;
private:
// The IScriptControl object that contains the script procedure.
IScriptControlPtr _pScriptControl;
// Message buffer from which to read arguments to the
// script procedure.
ISource<LONG>& _source;
// The result code for the overall operation.
single_assignment<HRESULT> _result;
};
下列函式 AgentFibonacci 會建立數個 物件，並使用訊息傳遞將數 FibonacciScriptAgent 個輸入值傳送給這些物件。
// Computes multiple Fibonacci numbers in parallel by using
// asynchronous agents.
HRESULT AgentFibonacci(IScriptControlPtr pScriptControl)
{
// Message buffer to hold arguments to the script procedure.
unbounded_buffer<LONG> values;
// Create several agents.
array<agent*, 3> agents =
{
new FibonacciScriptAgent(pScriptControl, values),
new FibonacciScriptAgent(pScriptControl, values),
new FibonacciScriptAgent(pScriptControl, values),
};
// Start each agent.
for_each(begin(agents), end(agents), [](agent* a) {
a->start();
});
// Send a few values to the agents.
send(values, 30L);
send(values, 22L);
send(values, 10L);
send(values, 12L);
// Send a sentinel value to each agent.
for_each(begin(agents), end(agents), [&values](agent*) {
send(values, FibonacciScriptAgent::Sentinel);
});
// Wait for all agents to finish.
agent::wait_for_all(3, &agents[0]);
// Determine the result code.
HRESULT hr = S_OK;
for_each(begin(agents), end(agents), [&hr](agent* a) {
HRESULT hrTemp;
if (FAILED(hrTemp =
reinterpret_cast<FibonacciScriptAgent*>(a)->GetHRESULT()))
{
hr = hrTemp;
}
});
// Clean up.
for_each(begin(agents), end(agents), [](agent* a) {
delete a;
});
return hr;
}
若要搭配範例使用 函 AgentFibonacci 式，請在函式傳回之前 wmain 新增下列程式碼。
// Use asynchronous agents to compute multiple
// Fibonacci numbers in parallel.
wcout << endl << L"Agent Fibonacci:" << endl;
if (FAILED(hr = AgentFibonacci(pScriptControl)))
return hr;
完整範例
下列程式碼顯示完整的範例，它會使用平行演算法和非同步代理程式來呼叫計算 Fibonacci 數位的腳本程式。
// parallel-scripts.cpp
// compile with: /EHsc
#include <agents.h>
#include <ppl.h>
#include <array>
#include <sstream>
#include <iostream>
#include <atlsafe.h>
// TODO: Change this path if necessary.
#import "C:\windows\system32\msscript.ocx"
using namespace concurrency;
using namespace MSScriptControl;
using namespace std;
// An exception-safe wrapper class that manages the lifetime
// of the COM library in a given scope.
class CCoInitializer
{
public:
explicit CCoInitializer(DWORD dwCoInit = COINIT_APARTMENTTHREADED)
: _coinitialized(false)
{
// Initialize the COM library on the current thread.
HRESULT hr = CoInitializeEx(NULL, dwCoInit);
if (FAILED(hr))
throw hr;
_coinitialized = true;
}
~CCoInitializer()
{
// Free the COM library.
if (_coinitialized)
CoUninitialize();
}
private:
// Flags whether COM was properly initialized.
bool _coinitialized;
// Hide copy constructor and assignment operator.
CCoInitializer(const CCoInitializer&);
CCoInitializer& operator=(const CCoInitializer&);
};
// Calls a procedure in an IScriptControl object.
template<size_t ArgCount>
_variant_t RunScriptProcedure(IScriptControlPtr pScriptControl,
_bstr_t& procedureName, array<_variant_t, ArgCount>& arguments)
{
// Create a 1-dimensional, 0-based safe array.
SAFEARRAYBOUND rgsabound[] = { ArgCount, 0 };
CComSafeArray<VARIANT> sa(rgsabound, 1U);
// Copy the arguments to the safe array.
LONG lIndex = 0;
for_each(begin(arguments), end(arguments), [&](_variant_t& arg) {
HRESULT hr = sa.SetAt(lIndex, arg);
if (FAILED(hr))
throw hr;
++lIndex;
});
// Call the procedure in the script.
return pScriptControl->Run(procedureName, &sa.m_psa);
}
// Computes multiple Fibonacci numbers in parallel by using
// the parallel_for algorithm.
HRESULT ParallelFibonacci(IScriptControlPtr pScriptControl)
{
try {
parallel_for(10L, 20L, [&pScriptControl](LONG lIndex)
{
// Enable COM for the lifetime of the task.
CCoInitializer coinit(COINIT_MULTITHREADED);
// Call the helper function to run the script procedure.
array<_variant_t, 1> args = { _variant_t(lIndex) };
_variant_t result = RunScriptProcedure(
pScriptControl,
_bstr_t("fib"),
args);
// Print the result.
wstringstream ss;
ss << L"fib(" << lIndex << L") = " << result.lVal << endl;
wcout << ss.str();
});
}
catch (HRESULT hr) {
return hr;
}
return S_OK;
}
// A basic agent that calls a script procedure to compute the
// nth Fibonacci number.
class FibonacciScriptAgent : public agent
{
public:
FibonacciScriptAgent(IScriptControlPtr pScriptControl, ISource<LONG>& source)
: _pScriptControl(pScriptControl)
, _source(source) { }
public:
// Retrieves the result code.
HRESULT GetHRESULT()
{
return receive(_result);
}
protected:
void run()
{
// Initialize the COM library on the current thread.
CoInitializeEx(NULL, COINIT_MULTITHREADED);
// Read values from the message buffer until
// we receive the sentinel value.
LONG lValue;
while ((lValue = receive(_source)) != Sentinel)
{
try {
// Call the helper function to run the script procedure.
array<_variant_t, 1> args = { _variant_t(lValue) };
_variant_t result = RunScriptProcedure(
_pScriptControl,
_bstr_t("fib"),
args);
// Print the result.
wstringstream ss;
ss << L"fib(" << lValue << L") = " << result.lVal << endl;
wcout << ss.str();
}
catch (HRESULT hr) {
send(_result, hr);
break;
}
}
// Set the result code (does nothing if a value is already set).
send(_result, S_OK);
// Free the COM library.
CoUninitialize();
// Set the agent to the finished state.
done();
}
public:
// Signals the agent to terminate.
static const LONG Sentinel = 0L;
private:
// The IScriptControl object that contains the script procedure.
IScriptControlPtr _pScriptControl;
// Message buffer from which to read arguments to the
// script procedure.
ISource<LONG>& _source;
// The result code for the overall operation.
single_assignment<HRESULT> _result;
};
// Computes multiple Fibonacci numbers in parallel by using
// asynchronous agents.
HRESULT AgentFibonacci(IScriptControlPtr pScriptControl)
{
// Message buffer to hold arguments to the script procedure.
unbounded_buffer<LONG> values;
// Create several agents.
array<agent*, 3> agents =
{
new FibonacciScriptAgent(pScriptControl, values),
new FibonacciScriptAgent(pScriptControl, values),
new FibonacciScriptAgent(pScriptControl, values),
};
// Start each agent.
for_each(begin(agents), end(agents), [](agent* a) {
a->start();
});
// Send a few values to the agents.
send(values, 30L);
send(values, 22L);
send(values, 10L);
send(values, 12L);
// Send a sentinel value to each agent.
for_each(begin(agents), end(agents), [&values](agent*) {
send(values, FibonacciScriptAgent::Sentinel);
});
// Wait for all agents to finish.
agent::wait_for_all(3, &agents[0]);
// Determine the result code.
HRESULT hr = S_OK;
for_each(begin(agents), end(agents), [&hr](agent* a) {
HRESULT hrTemp;
if (FAILED(hrTemp =
reinterpret_cast<FibonacciScriptAgent*>(a)->GetHRESULT()))
{
hr = hrTemp;
}
});
// Clean up.
for_each(begin(agents), end(agents), [](agent* a) {
delete a;
});
return hr;
}
int wmain()
{
HRESULT hr;
// Enable COM on this thread for the lifetime of the program.
CCoInitializer coinit(COINIT_MULTITHREADED);
// Create the script control.
IScriptControlPtr pScriptControl(__uuidof(ScriptControl));
// Set script control properties.
pScriptControl->Language = "JScript";
pScriptControl->AllowUI = TRUE;
// Add script code that computes the nth Fibonacci number.
hr = pScriptControl->AddCode(
"function fib(n) { if (n<2) return n; else return fib(n-1) + fib(n-2); }" );
if (FAILED(hr))
return hr;
// Test the script control by computing the 15th Fibonacci number.
wcout << L"Main Thread:" << endl;
long n = 15;
array<_variant_t, 1> args = { _variant_t(n) };
_variant_t result = RunScriptProcedure(
pScriptControl,
_bstr_t("fib"),
args);
// Print the result.
wcout << L"fib(" << n << L") = " << result.lVal << endl;
// Use the parallel_for algorithm to compute multiple
// Fibonacci numbers in parallel.
wcout << endl << L"Parallel Fibonacci:" << endl;
if (FAILED(hr = ParallelFibonacci(pScriptControl)))
return hr;
// Use asynchronous agents to compute multiple
// Fibonacci numbers in parallel.
wcout << endl << L"Agent Fibonacci:" << endl;
if (FAILED(hr = AgentFibonacci(pScriptControl)))
return hr;
return S_OK;
}
此範例會產生下列範例輸出。
Main Thread:
fib(15) = 610
Parallel Fibonacci:
fib(15) = 610
fib(10) = 55
fib(16) = 987
fib(18) = 2584
fib(11) = 89
fib(17) = 1597
fib(19) = 4181
fib(12) = 144
fib(13) = 233
fib(14) = 377
Agent Fibonacci:
fib(30) = 832040
fib(22) = 17711
fib(10) = 55
fib(12) = 144
編譯程式碼
複製範例程式碼，並將其貼到 Visual Studio 專案中，或貼到名為 parallel-scripts.cpp 的檔案中，然後在 Visual Studio 命令提示字元視窗中執行下列命令。
cl.exe /EHsc parallel-scripts.cpp /link ole32.lib
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