Running tests in slang-test process (#740)

* First pass at having an interface to write text to that can be replaced.
Simplifed and made more rigerous the interface used to write formatted strings.

* Added AppContext to simplify setting up and parsing around of streams.

* Added more simplified way to get the std error/out from AppContext.

* Work in progress using dll for tools to speed up testing.

* First pass at ISlangWriter interface.

* Added support for writing VaArgs.
Added NullWriter.

* Use ISlangWriter for output.

* Use ISlangWriter for output - replacing OutputCallback.
Make IRDump go to ISlangWriter

* SlangWriterTargetType -> SlangWriterChannel
Improvements around AppContext

* Shared library working with slang-reflection-test.

* Dll testing working for render-test.

* Include va_list definintion from header.

* Fix errors from clang.

* Fix typo for linux.

* Added -usexes option

* Fix typo.

* Fix arguments problem on linux.

* Fix typo for linux.

* Add windows tool shared library projects.

* Fix warning from x86 win build.
Fix signed warning from slang-test/main.cpp

* First attempt at getting premake to work on travis, and run tests.

* Try moving build out into script.

* Invoke bash scripts so they don't have to be executable.

* Drive configuration/tests from env parameters set by travis

* Try using source to run travis tests.

* Remove the build.linux directory - but doing so will overwrite Makefile.

* Made -fno-delete-null-pointer-checks gcc only.

* Try to fix warning from -fno-delete-null-pointer-checks

* Turn of warnings for unknown switches.

* Try to make premake choose the correct tooling.

* Disabled missing braces warning.

* Disable -Wundefined-var-template on clang.

* -Wunused-function disabled for clang.

* Fix typo due to SlangBool.

* Remove this nullptr tests.

* "-Wno-unused-private-field" for clang.

* Added "-Wno-undefined-bool-conversion"

* Add DominatorList::end fix.

* Split scripts into travis_build.sh travis_test.sh

* Fix gcc/clang template pre-declaration issue around QualType.

* Fix premake to build such that pthread correctly links with slang-glslang

1 files changed, 6 insertions, 2 deletions

diff --git a/source/core/slang-string.h b/source/core/slang-string.h
index fb60ef562..435e2b29b 100644
--- a/source/core/slang-string.h
+++ b/source/core/slang-string.h
@@ -329,8 +329,7 @@ namespace Slang
         }
 
         void ensureUniqueStorageWithCapacity(UInt capacity);
-        char* prepareForAppend(UInt count);
-
+     
         RefPtr<StringRepresentation> buffer;
 
     public:
@@ -347,6 +346,11 @@ namespace Slang
 		{
 		}
 
+            /// Returns a buffer which can hold at least count chars
+        char* prepareForAppend(UInt count);
+            /// Append data written to buffer output via 'prepareForAppend' directly written 'inplace'
+        void appendInPlace(const char* chars, UInt count);
+
         SLANG_FORCE_INLINE StringRepresentation* getStringRepresentation() const { return buffer; }
 
 		const char * begin() const