Add Pipe::WriteWithTimeout method

Summary:
This commit adds a WriteWithTimeout method to time Pipe class, analogous to the existing
ReadWithTimeout(). It also changes the meaning of passing zero as a timeout value. Previously,
zero was used as an infinite timeout value. Now, the meaning of zero timeout to return the data
avaiable without sleeping (basically, a non-blocking operation). This makes the behaviour of Pipe
consistent with the Communication/Connection classes. For blocking operatios with infinite
timeout, I introduce a special constant for this purpose.

Reviewers: ovyalov, zturner

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D11358

llvm-svn: 242764

1 files changed, 30 insertions, 3 deletions

diff --git a/lldb/source/Host/windows/PipeWindows.cpp b/lldb/source/Host/windows/PipeWindows.cpp
index d4afd6e7494..e2029971742 100644
--- a/lldb/source/Host/windows/PipeWindows.cpp
+++ b/lldb/source/Host/windows/PipeWindows.cpp
@@ -289,7 +289,7 @@ PipeWindows::ReadWithTimeout(void *buf, size_t size, const std::chrono::microsec
     if (!result && GetLastError() != ERROR_IO_PENDING)
         return Error(::GetLastError(), eErrorTypeWin32);
 
-    DWORD timeout = (duration == std::chrono::microseconds::zero()) ? INFINITE : duration.count() * 1000;
+    DWORD timeout = (duration == kInfiniteTimeout) ? INFINITE : duration.count() * 1000;
     DWORD wait_result = ::WaitForSingleObject(m_read_overlapped.hEvent, timeout);
     if (wait_result != WAIT_OBJECT_0)
     {
@@ -319,7 +319,10 @@ PipeWindows::ReadWithTimeout(void *buf, size_t size, const std::chrono::microsec
 }
 
 Error
-PipeWindows::Write(const void *buf, size_t num_bytes, size_t &bytes_written)
+PipeWindows::WriteWithTimeout(const void *buf,
+                              size_t num_bytes,
+                              const std::chrono::microseconds &duration,
+                              size_t &bytes_written)
 {
     if (!CanWrite())
         return Error(ERROR_INVALID_HANDLE, eErrorTypeWin32);
@@ -329,8 +332,32 @@ PipeWindows::Write(const void *buf, size_t num_bytes, size_t &bytes_written)
     if (!write_result && GetLastError() != ERROR_IO_PENDING)
         return Error(::GetLastError(), eErrorTypeWin32);
 
-    BOOL result = GetOverlappedResult(m_write, &m_write_overlapped, &sys_bytes_written, TRUE);
+    DWORD timeout = (duration == kInfiniteTimeout) ? INFINITE : duration.count() * 1000;
+    DWORD wait_result = ::WaitForSingleObject(m_write_overlapped.hEvent, timeout);
+    if (wait_result != WAIT_OBJECT_0)
+    {
+        // The operation probably failed.  However, if it timed out, we need to cancel the I/O.
+        // Between the time we returned from WaitForSingleObject and the time we call CancelIoEx,
+        // the operation may complete.  If that hapens, CancelIoEx will fail and return ERROR_NOT_FOUND.
+        // If that happens, the original operation should be considered to have been successful.
+        bool failed = true;
+        DWORD failure_error = ::GetLastError();
+        if (wait_result == WAIT_TIMEOUT)
+        {
+            BOOL cancel_result = CancelIoEx(m_read, &m_write_overlapped);
+            if (!cancel_result && GetLastError() == ERROR_NOT_FOUND)
+                failed = false;
+        }
+        if (failed)
+            return Error(failure_error, eErrorTypeWin32);
+    }
+
+    // Now we call GetOverlappedResult setting bWait to false, since we've already waited
+    // as long as we're willing to.
+    BOOL result = GetOverlappedResult(m_write, &m_write_overlapped, &sys_bytes_written, FALSE);
     if (!result)
         return Error(::GetLastError(), eErrorTypeWin32);
+
+    bytes_written = sys_bytes_written;
     return Error();
 }