No changes, move wxStreamTempInputBuffer to a header file.

[wxWidgets.git] / include / wx / private / streamtempinput.h

diff --git a/include/wx/private/streamtempinput.h b/include/wx/private/streamtempinput.h
new file mode 100644 (file)
index 0000000..72f3957
--- /dev/null
+++ b/include/wx/private/streamtempinput.h
@@ -0,0 +1,122 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/private/streamtempinput.h
+// Purpose:     defines wxStreamTempInputBuffer which is used by Unix and MSW
+//              implementations of wxExecute; this file is only used by the
+//              library and never by the user code
+// Author:      Vadim Zeitlin
+// Modified by: Rob Bresalier
+// Created:     2013-05-04
+// RCS-ID:      $Id$
+// Copyright:   (c) 2002 Vadim Zeitlin <vadim@wxwindows.org>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_PRIVATE_STREAMTEMPINPUT_H
+#define _WX_PRIVATE_STREAMTEMPINPUT_H
+
+#include "wx/private/pipestream.h"
+
+// ----------------------------------------------------------------------------
+// wxStreamTempInputBuffer
+// ----------------------------------------------------------------------------
+
+/*
+   wxStreamTempInputBuffer is a hack which we need to solve the problem of
+   executing a child process synchronously with IO redirecting: when we do
+   this, the child writes to a pipe we open to it but when the pipe buffer
+   (which has finite capacity, e.g. commonly just 4Kb) becomes full we have to
+   read data from it because the child blocks in its write() until then and if
+   it blocks we are never going to return from wxExecute() so we dead lock.
+
+   So here is the fix: we now read the output as soon as it appears into a temp
+   buffer (wxStreamTempInputBuffer object) and later just stuff it back into
+   the stream when the process terminates. See supporting code in wxExecute()
+   itself as well.
+
+   Note that this is horribly inefficient for large amounts of output (count
+   the number of times we copy the data around) and so a better API is badly
+   needed! However it's not easy to devise a way to do this keeping backwards
+   compatibility with the existing wxExecute(wxEXEC_SYNC)...
+*/
+class wxStreamTempInputBuffer
+{
+public:
+    wxStreamTempInputBuffer()
+    {
+        m_stream = NULL;
+        m_buffer = NULL;
+        m_size = 0;
+    }
+
+    // call to associate a stream with this buffer, otherwise nothing happens
+    // at all
+    void Init(wxPipeInputStream *stream)
+    {
+        wxASSERT_MSG( !m_stream, wxS("Can only initialize once") );
+
+        m_stream = stream;
+    }
+
+    // check for input on our stream and cache it in our buffer if any
+    //
+    // return true if anything was done
+    bool Update()
+    {
+        if ( !m_stream || !m_stream->CanRead() )
+            return false;
+
+        // realloc in blocks of 4Kb: this is the default (and minimal) buffer
+        // size of the Unix pipes so it should be the optimal step
+        //
+        // NB: don't use "static int" in this inline function, some compilers
+        //     (e.g. IBM xlC) don't like it
+        enum { incSize = 4096 };
+
+        void *buf = realloc(m_buffer, m_size + incSize);
+        if ( !buf )
+            return false;
+
+        m_buffer = buf;
+        m_stream->Read((char *)m_buffer + m_size, incSize);
+        m_size += m_stream->LastRead();
+
+        return true;
+    }
+
+    // check if can continue reading from the stream, this is used to disable
+    // the callback once we can't read anything more
+    bool Eof() const
+    {
+        // If we have no stream, always return true as we can't read any more.
+        return !m_stream || m_stream->Eof();
+    }
+
+    // dtor puts the data buffered during this object lifetime into the
+    // associated stream
+    ~wxStreamTempInputBuffer()
+    {
+        if ( m_buffer )
+        {
+            m_stream->Ungetch(m_buffer, m_size);
+            free(m_buffer);
+        }
+    }
+
+    const void *GetBuffer() const { return m_buffer; }
+
+    size_t GetSize() const { return m_size; }
+
+private:
+    // the stream we're buffering, if NULL we don't do anything at all
+    wxPipeInputStream *m_stream;
+
+    // the buffer of size m_size (NULL if m_size == 0)
+    void *m_buffer;
+
+    // the size of the buffer
+    size_t m_size;
+
+    wxDECLARE_NO_COPY_CLASS(wxStreamTempInputBuffer);
+};
+
+#endif // _WX_PRIVATE_STREAMTEMPINPUT_H