clean up UNO available() implementations

There seems to be some confusion here. available() is actually the
number of bytes that can be read without blocking, but most
implementations seems to be just returning the number of bytes remaining
in the stream. Since we're doing that, let's do it properly.

(*) some of them were just casting, instead of clamping, which will
return wrong values sometimes.
(*) FileStreamWrapper_Impl/OInputStreamWrapper/OTempFileService were
doing unnecessary work, instead of just asking the underlying SvStream
for it's remaining size

Change-Id: I3ef26e0363e989ed3e00be0fdb993e1cdeb7819f
Reviewed-on: https://gerrit.libreoffice.org/57264
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 8 insertions, 2 deletions

diff --git a/xmlhelp/source/cxxhelp/provider/inputstream.cxx b/xmlhelp/source/cxxhelp/provider/inputstream.cxx
index 19e88810799e..e5f18bb5fcc9 100644
--- a/xmlhelp/source/cxxhelp/provider/inputstream.cxx
+++ b/xmlhelp/source/cxxhelp/provider/inputstream.cxx
@@ -116,7 +116,13 @@ XInputStream_impl::skipBytes(
 sal_Int32 SAL_CALL
 XInputStream_impl::available()
 {
-    return 0;
+    sal_uInt64 uPos;
+    if( osl::FileBase::E_None != m_aFile.getPos( uPos ) )
+        throw io::IOException();
+    sal_uInt64 uSize;
+    if( osl::FileBase::E_None != m_aFile.getSize( uSize ) )
+        throw io::IOException();
+    return std::min<sal_uInt64>(SAL_MAX_INT32, uSize - uPos);
 }
 
 
diff --git a/xmlhelp/source/cxxhelp/provider/urlparameter.cxx b/xmlhelp/source/cxxhelp/provider/urlparameter.cxx
index fb0aa90cb62b..8ed8f80a1c69 100644
--- a/xmlhelp/source/cxxhelp/provider/urlparameter.cxx
+++ b/xmlhelp/source/cxxhelp/provider/urlparameter.cxx
@@ -924,7 +924,7 @@ void SAL_CALL InputStreamTransformer::skipBytes( sal_Int32 nBytesToSkip )
 sal_Int32 SAL_CALL InputStreamTransformer::available()
 {
     osl::MutexGuard aGuard( m_aMutex );
-    return std::max<sal_Int32>(buffer.getLength() - pos, 0);
+    return std::min<sal_Int64>(SAL_MAX_INT32, buffer.getLength() - pos);
 }