From 4c68a10264347cc04b1a6634000595f160792231 Mon Sep 17 00:00:00 2001
From: =?utf8?q?V=C3=A1clav=20Slav=C3=ADk?= <vslavik@fastmail.fm>
Date: Sun, 11 Apr 2004 19:34:56 +0000
Subject: [PATCH] improvements to zlib streams (patch 929416): 1. CanHandleGZip
 static method 2. code cleanup 3. 2.4 compatibility mode

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@26713 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
---
 docs/changes.txt           |   3 +
 docs/latex/wx/strmzlib.tex |  55 ++++++++++---
 include/wx/zstream.h       |  23 ++++--
 src/common/zstream.cpp     | 161 +++++++++++++++++++++++++------------
 4 files changed, 172 insertions(+), 70 deletions(-)

diff --git a/docs/changes.txt b/docs/changes.txt
index 6dd0708c9b..1ab41e7a4f 100644
--- a/docs/changes.txt
+++ b/docs/changes.txt
@@ -42,6 +42,9 @@ INCOMPATIBLE CHANGES SINCE 2.4.x
 - wxTaskBarIcon objects must now be destroyed before the application can exit.
   Previously, the application terminated if there were no top level windows;
   now it terminates if there are no top level windows or taskbar icons left.
+- wxZlibInputStream is not by default compatible with the output of the
+  2.4.x version of wxZlibOutputStream. However, there is a compatibilty mode,
+  switched on by passing wxZLIB_24COMPATIBLE to the constructor.
 
 wxTaskBarIcon must be explicitly destroyed now, otherwise the application
   won't exit even though there are no top level windows
diff --git a/docs/latex/wx/strmzlib.tex b/docs/latex/wx/strmzlib.tex
index d563a50640..46945e16ad 100644
--- a/docs/latex/wx/strmzlib.tex
+++ b/docs/latex/wx/strmzlib.tex
@@ -4,7 +4,8 @@
 \section{\class{wxZlibInputStream}}\label{wxzlibinputstream}
 
 This filter stream decompresses a stream that is in zlib or gzip format.
-Note that reading the gzip format requires zlib version 1.2.0 greater.
+Note that reading the gzip format requires zlib version 1.2.1 or greater,
+(the builtin version does support gzips).
 
 The stream is not seekable, \helpref{SeekI()}{wxinputstreamseeki} returns
  {\it wxInvalidOffset}. Also \helpref{GetSize()}{wxstreambasegetsize} is
@@ -27,25 +28,45 @@ not supported, it always returns $0$.
 
 \membersection{wxZlibInputStream::wxZlibInputStream}
 
-\func{}{wxZlibInputStream}{\param{wxInputStream\&}{ stream}, \param{int}{ flags = wxZLIB\_ZLIB | wxZLIB\_GZIP}}
+\func{}{wxZlibInputStream}{\param{wxInputStream\&}{ stream}, \param{int}{ flags = wxZLIB\_AUTO}}
 
 The {\it flags} wxZLIB\_ZLIB and wxZLIB\_GZIP specify whether the input data
-is in zlib or gzip format. If both are used, bitwise ored, then zlib will
+is in zlib or gzip format. If wxZLIB\_AUTO is used, then zlib will
 autodetect the stream type, this is the default.
-If {\it flags} is zero, then the data is assumed to be a raw deflate stream
-without either zlib or gzip headers.
+
+If {\it flags} is wxZLIB\_NO\_HEADER, then the data is assumed to be a raw
+deflate stream without either zlib or gzip headers. This is a lower level
+mode, which is not usually used directly. It can be used to read a raw
+deflate stream embedded in a higher level protocol.
+
+%if WXWIN_COMPATIBILITY_2_4
+This version is not by default compatible with the output produced by
+the version of {\it wxZlibOutputStream} in wxWidgets 2.4.x. However,
+there is a compatibilty mode, which is switched on by passing
+wxZLIB\_24COMPATIBLE for flags. Note that in when operating in compatibilty
+mode error checking is very much reduced.
+%endif
 
 The following symbols can be use for the flags:
 
 \begin{verbatim}
 // Flags
 enum {
-    wxZLIB_NO_HEADER = 0,   // raw deflate stream, no header or checksum
-    wxZLIB_ZLIB = 1,        // zlib header and checksum
-    wxZLIB_GZIP = 2         // gzip header and checksum, requires zlib 1.2+
+#if WXWIN_COMPATIBILITY_2_4
+    wxZLIB_24COMPATIBLE = 4, // read v2.4.x data without error
+#endif
+    wxZLIB_NO_HEADER = 0,    // raw deflate stream, no header or checksum
+    wxZLIB_ZLIB = 1,         // zlib header and checksum
+    wxZLIB_GZIP = 2,         // gzip header and checksum, requires zlib 1.2.1+
+    wxZLIB_AUTO = 3          // autodetect header zlib or gzip
 };
 \end{verbatim}
 
+\membersection{wxZlibInputStream::CanHandleGZip}\label{wxzlibinputstreamcanhandlegzip}
+
+\func{static bool}{CanHandleGZip}{\void}
+
+Returns true if zlib library in use can handle gzip compressed data.
 
 % -----------------------------------------------------------------------------
 % wxZlibOutputStream
@@ -54,7 +75,8 @@ enum {
 
 This stream compresses all data written to it. The compressed output can be
 in zlib or gzip format.
-Note that writing the gzip format requires zlib version 1.2.0 greater.
+Note that writing the gzip format requires zlib version 1.2.1 or greater
+(the builtin version does support gzips).
 
 The stream is not seekable, \helpref{SeekO()}{wxoutputstreamseeko} returns
  {\it wxInvalidOffset}.
@@ -86,8 +108,11 @@ value (currently equivalent to 6).
 
 The {\it flags} wxZLIB\_ZLIB and wxZLIB\_GZIP specify whether the output data
 will be in zlib or gzip format. wxZLIB\_ZLIB is the default.
-If {\it flags} is zero, then a raw deflate stream is output without either
-zlib or gzip headers.
+
+If {\it flags} is wxZLIB\_NO\_HEADER, then a raw deflate stream is output
+without either zlib or gzip headers. This is a lower level
+mode, which is not usually used directly. It can be used to embed a raw
+deflate stream in a higher level protocol.
 
 The following symbols can be use for the compression level and flags:
 
@@ -104,7 +129,13 @@ enum {
 enum {
     wxZLIB_NO_HEADER = 0,   // raw deflate stream, no header or checksum
     wxZLIB_ZLIB = 1,        // zlib header and checksum
-    wxZLIB_GZIP = 2         // gzip header and checksum, requires zlib 1.2+
+    wxZLIB_GZIP = 2         // gzip header and checksum, requires zlib 1.2.1+
 };
 \end{verbatim}
 
+\membersection{wxZlibOutputStream::CanHandleGZip}\label{wxoutputstreamcanhandlegzip}
+
+\func{static bool}{CanHandleGZip}{\void}
+
+Returns true if zlib library in use can handle gzip compressed data.
+
diff --git a/include/wx/zstream.h b/include/wx/zstream.h
index de88e07b56..748abd7b47 100644
--- a/include/wx/zstream.h
+++ b/include/wx/zstream.h
@@ -31,19 +31,25 @@ enum {
 
 // Flags
 enum {
-    wxZLIB_NO_HEADER = 0,   // raw deflate stream, no header or checksum
-    wxZLIB_ZLIB = 1,        // zlib header and checksum
-    wxZLIB_GZIP = 2         // gzip header and checksum, requires zlib 1.2+
+#if WXWIN_COMPATIBILITY_2_4
+    wxZLIB_24COMPATIBLE = 4, // read v2.4.x data without error
+#endif
+    wxZLIB_NO_HEADER = 0,    // raw deflate stream, no header or checksum
+    wxZLIB_ZLIB = 1,         // zlib header and checksum
+    wxZLIB_GZIP = 2,         // gzip header and checksum, requires zlib 1.2.1+
+    wxZLIB_AUTO = 3          // autodetect header zlib or gzip
 };
 
 class WXDLLIMPEXP_BASE wxZlibInputStream: public wxFilterInputStream {
  public:
-  wxZlibInputStream(wxInputStream& stream, int flags = wxZLIB_ZLIB | wxZLIB_GZIP);
+  wxZlibInputStream(wxInputStream& stream, int flags = wxZLIB_AUTO);
   virtual ~wxZlibInputStream();
 
   char Peek() { return wxInputStream::Peek(); }
   size_t GetSize() const { return wxInputStream::GetSize(); }
 
+  static bool CanHandleGZip();
+
  protected:
   size_t OnSysRead(void *buffer, size_t size);
   off_t OnSysTell() const { return m_pos; }
@@ -53,8 +59,11 @@ class WXDLLIMPEXP_BASE wxZlibInputStream: public wxFilterInputStream {
   unsigned char *m_z_buffer;
   struct z_stream_s *m_inflate;
   off_t m_pos;
+#if WXWIN_COMPATIBILITY_2_4
+  bool m_24compatibilty;
+#endif
 
-    DECLARE_NO_COPY_CLASS(wxZlibInputStream)
+  DECLARE_NO_COPY_CLASS(wxZlibInputStream)
 };
 
 class WXDLLIMPEXP_BASE wxZlibOutputStream: public wxFilterOutputStream {
@@ -65,6 +74,8 @@ class WXDLLIMPEXP_BASE wxZlibOutputStream: public wxFilterOutputStream {
   void Sync() { DoFlush(false); }
   size_t GetSize() const { return (size_t)m_pos; }
 
+  static bool CanHandleGZip();
+
  protected:
   size_t OnSysWrite(const void *buffer, size_t size);
   off_t OnSysTell() const { return m_pos; }
@@ -77,7 +88,7 @@ class WXDLLIMPEXP_BASE wxZlibOutputStream: public wxFilterOutputStream {
   struct z_stream_s *m_deflate;
   off_t m_pos;
 
-    DECLARE_NO_COPY_CLASS(wxZlibOutputStream)
+  DECLARE_NO_COPY_CLASS(wxZlibOutputStream)
 };
 
 #endif
diff --git a/src/common/zstream.cpp b/src/common/zstream.cpp
index 5372d21481..09d616bab2 100644
--- a/src/common/zstream.cpp
+++ b/src/common/zstream.cpp
@@ -38,7 +38,9 @@
 #endif
 
 enum {
-    ZSTREAM_BUFFER_SIZE = 16384
+    ZSTREAM_BUFFER_SIZE = 16384,
+    ZSTREAM_GZIP        = 0x10,     // gzip header
+    ZSTREAM_AUTO        = 0x20      // auto detect between gzip and zlib
 };
 
 //////////////////////
@@ -53,25 +55,43 @@ wxZlibInputStream::wxZlibInputStream(wxInputStream& stream, int flags)
   m_z_size = ZSTREAM_BUFFER_SIZE;
   m_pos = 0;
 
+#if WXWIN_COMPATIBILITY_2_4
+  // treat compatibilty mode as auto
+  m_24compatibilty = flags == wxZLIB_24COMPATIBLE;
+  if (m_24compatibilty)
+    flags = wxZLIB_AUTO;
+#endif
+
+  // if gzip is asked for but not supported...
+  if ((flags == wxZLIB_GZIP || flags == wxZLIB_AUTO) && !CanHandleGZip()) {
+    if (flags == wxZLIB_AUTO) {
+      // an error will come later if the input turns out not to be a zlib
+      flags = wxZLIB_ZLIB;
+    }
+    else {
+      wxLogError(_("Gzip not supported by this version of zlib"));
+      m_lasterror = wxSTREAM_READ_ERROR;
+      return;
+    }
+  }
+
   if (m_z_buffer) {
     m_inflate = new z_stream_s;
 
     if (m_inflate) {
       memset(m_inflate, 0, sizeof(z_stream_s));
 
-      wxASSERT((flags & ~(wxZLIB_ZLIB | wxZLIB_GZIP)) == 0);
- 
-      // when autodetecting between gzip & zlib, silently drop gzip flag
-      // if the version of zlib doesn't support it
-      if (flags == (wxZLIB_ZLIB | wxZLIB_GZIP)
-              && strcmp(zlib_version, "1.2.") < 0)
-        flags &= ~wxZLIB_GZIP;
-
-      int bits = flags ? MAX_WBITS : -MAX_WBITS;
-      if (flags & wxZLIB_GZIP)
-        bits |= (flags & wxZLIB_ZLIB) ? 0x20 : 0x10;
+      // see zlib.h for documentation on windowBits
+      int windowBits = MAX_WBITS;
+      switch (flags) {
+        case wxZLIB_NO_HEADER:  windowBits = -MAX_WBITS; break;
+        case wxZLIB_ZLIB:       windowBits = MAX_WBITS; break;
+        case wxZLIB_GZIP:       windowBits = MAX_WBITS | ZSTREAM_GZIP; break;
+        case wxZLIB_AUTO:       windowBits = MAX_WBITS | ZSTREAM_AUTO; break;
+        default:                wxFAIL_MSG(wxT("Invalid zlib flag"));
+      }
 
-      if (inflateInit2(m_inflate, bits) == Z_OK)
+      if (inflateInit2(m_inflate, windowBits) == Z_OK)
         return;
     }
   }
@@ -102,36 +122,49 @@ size_t wxZlibInputStream::OnSysRead(void *buffer, size_t size)
   m_inflate->avail_out = size;
 
   while (err == Z_OK && m_inflate->avail_out > 0) {
-    if (m_inflate->avail_in == 0) {
+    if (m_inflate->avail_in == 0 && m_parent_i_stream->IsOk()) {
       m_parent_i_stream->Read(m_z_buffer, m_z_size);
       m_inflate->next_in = m_z_buffer;
       m_inflate->avail_in = m_parent_i_stream->LastRead();
+    }
+    err = inflate(m_inflate, Z_SYNC_FLUSH);
+  }
 
-      if (m_inflate->avail_in == 0) {
-        if (m_parent_i_stream->Eof())
-          wxLogError(_("Can't read inflate stream: unexpected EOF in underlying stream."));
-        m_lasterror = wxSTREAM_READ_ERROR;
+  switch (err) {
+    case Z_OK:
         break;
+
+    case Z_STREAM_END:
+      // Unread any data taken from past the end of the deflate stream, so that
+      // any additional data can be read from the underlying stream (the crc
+      // in a gzip for example)
+      if (m_inflate->avail_in) {
+        m_parent_i_stream->Ungetch(m_inflate->next_in, m_inflate->avail_in);
+        m_inflate->avail_in = 0;
       }
-    }
-    err = inflate(m_inflate, Z_NO_FLUSH);
-  }
+      m_lasterror = wxSTREAM_EOF;
+      break;
 
-  if (err == Z_STREAM_END) {
-    // Unread any data taken from past the end of the deflate stream, so that
-    // any additional data can be read from the underlying stream (the crc
-    // in a gzip for example)
-    if (m_inflate->avail_in) {
-      m_parent_i_stream->Ungetch(m_inflate->next_in, m_inflate->avail_in);
-      m_inflate->avail_in = 0;
-    }
-    m_lasterror = wxSTREAM_EOF;
-  } else if (err != Z_OK) {
-    wxString msg(m_inflate->msg, *wxConvCurrent);
-    if (!msg)
-      msg.Format(_("zlib error %d"), err);
-    wxLogError(_("Can't read from inflate stream: %s\n"), msg.c_str());
-    m_lasterror = wxSTREAM_READ_ERROR;
+    case Z_BUF_ERROR:
+      // Indicates that zlib was expecting more data, but the parent stream
+      // has none. Other than Eof the error will have been already reported
+      // by the parent strean,
+      m_lasterror = wxSTREAM_READ_ERROR;
+      if (m_parent_i_stream->Eof())
+#if WXWIN_COMPATIBILITY_2_4
+        if (m_24compatibilty)
+          m_lasterror = wxSTREAM_EOF;
+        else
+#endif
+          wxLogError(_("Can't read inflate stream: unexpected EOF in underlying stream."));
+      break;
+
+    default:
+      wxString msg(m_inflate->msg, *wxConvCurrent);
+      if (!msg)
+        msg.Format(_("zlib error %d"), err);
+      wxLogError(_("Can't read from inflate stream: %s"), msg.c_str());
+      m_lasterror = wxSTREAM_READ_ERROR;
   }
 
   size -= m_inflate->avail_out;
@@ -139,6 +172,15 @@ size_t wxZlibInputStream::OnSysRead(void *buffer, size_t size)
   return size;
 }
 
+/* static */ bool wxZlibInputStream::CanHandleGZip()
+{
+  const char *dot = strchr(zlibVersion(), '.');
+  int major = atoi(zlibVersion());
+  int minor = dot ? atoi(dot + 1) : 0;
+  return major > 1 || (major == 1 && minor >= 2);
+}
+
+
 //////////////////////
 // wxZlibOutputStream
 //////////////////////
@@ -162,24 +204,34 @@ wxZlibOutputStream::wxZlibOutputStream(wxOutputStream& stream,
     wxASSERT_MSG(level >= 0 && level <= 9, wxT("wxZlibOutputStream compression level must be between 0 and 9!"));
   }
 
-  if (m_z_buffer) {
-     m_deflate = new z_stream_s;
+  // if gzip is asked for but not supported...
+  if (flags == wxZLIB_GZIP && !CanHandleGZip()) {
+    wxLogError(_("Gzip not supported by this version of zlib"));
+    m_lasterror = wxSTREAM_WRITE_ERROR;
+    return;
+  }
 
-     if (m_deflate) {
-        memset(m_deflate, 0, sizeof(z_stream_s));
-        m_deflate->next_out = m_z_buffer;
-        m_deflate->avail_out = m_z_size;
+  if (m_z_buffer) {
+    m_deflate = new z_stream_s;
 
-        wxASSERT(flags == 0 || flags == wxZLIB_ZLIB || flags == wxZLIB_GZIP);
+    if (m_deflate) {
+      memset(m_deflate, 0, sizeof(z_stream_s));
+      m_deflate->next_out = m_z_buffer;
+      m_deflate->avail_out = m_z_size;
  
-        int bits = flags ? MAX_WBITS : -MAX_WBITS;
-        if (flags & wxZLIB_GZIP)
-            bits |= 0x10;
-
-        if (deflateInit2(m_deflate, level, Z_DEFLATED, bits, 
-                         8, Z_DEFAULT_STRATEGY) == Z_OK)
-          return;
-     }
+      // see zlib.h for documentation on windowBits
+      int windowBits = MAX_WBITS;
+      switch (flags) {
+        case wxZLIB_NO_HEADER:  windowBits = -MAX_WBITS; break;
+        case wxZLIB_ZLIB:       windowBits = MAX_WBITS; break;
+        case wxZLIB_GZIP:       windowBits = MAX_WBITS | ZSTREAM_GZIP; break;
+        default:                wxFAIL_MSG(wxT("Invalid zlib flag"));
+      }
+
+      if (deflateInit2(m_deflate, level, Z_DEFLATED, windowBits, 
+                       8, Z_DEFAULT_STRATEGY) == Z_OK)
+        return;
+    }
   }
 
   wxLogError(_("Can't initialize zlib deflate stream."));
@@ -261,7 +313,7 @@ size_t wxZlibOutputStream::OnSysWrite(const void *buffer, size_t size)
     wxString msg(m_deflate->msg, *wxConvCurrent);
     if (!msg)
       msg.Format(_("zlib error %d"), err);
-    wxLogError(_("Can't write to deflate stream: %s\n"), msg.c_str());
+    wxLogError(_("Can't write to deflate stream: %s"), msg.c_str());
   }
 
   size -= m_deflate->avail_in;
@@ -269,6 +321,11 @@ size_t wxZlibOutputStream::OnSysWrite(const void *buffer, size_t size)
   return size;
 }
 
+/* static */ bool wxZlibOutputStream::CanHandleGZip()
+{ 
+  return wxZlibInputStream::CanHandleGZip();
+}
+
 #endif
   // wxUSE_ZLIB && wxUSE_STREAMS
   
-- 
2.50.0

