glslang: Allow programmatically prepending code to a shader without worrying...

glslang: Allow programmatically prepending code to a shader without worrying about #version being first, to implement command-line-defined macros.  From Dejan Mircevski <deki@google.com>.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@31448 e7fa87d3-cd2b-0410-9028-fcbf551c1848

glslang/MachineIndependent/ShaderLang.cpp

@@ -435,6 +435,7 @@ bool CompileDeferred(
     const char* const shaderStrings[],
     const int numStrings,
     const int* inputLengths,
+    const char* customPreamble,
     const EShOptimizationLevel optLevel,
     const TBuiltInResource* resources,
     int defaultVersion,         // use 100 for ES environment, 110 for desktop
@@ -457,18 +458,20 @@ bool CompileDeferred(
     // which lets the grammar accept what was a null (post preprocessing) shader.
     //
     // Shader will look like
-    //   string 0:                preamble
-    //   string 1...numStrings:   user's shader
-    //   string numStrings+1:     "int;"
-    //
-    size_t* lengths = new size_t[numStrings + 2];
-    const char** strings = new const char*[numStrings + 2];
+    //   string 0:                system preamble
+    //   string 1:                custom preamble
+    //   string 2...numStrings+1: user's shader
+    //   string numStrings+2:     "int;"
+    const int numPre = 2;
+    const int numPost = 1;
+    size_t* lengths = new size_t[numStrings + numPre + numPost];
+    const char** strings = new const char*[numStrings + numPre + numPost];
     for (int s = 0; s < numStrings; ++s) {
-        strings[s + 1] = shaderStrings[s];
+        strings[s + numPre] = shaderStrings[s];
         if (inputLengths == 0 || inputLengths[s] < 0)
-            lengths[s + 1] = strlen(shaderStrings[s]);
+            lengths[s + numPre] = strlen(shaderStrings[s]);
         else
-            lengths[s + 1] = inputLengths[s];
+            lengths[s + numPre] = inputLengths[s];
     }
 
     // First, without using the preprocessor or parser, find the #version, so we know what
@@ -476,7 +479,7 @@ bool CompileDeferred(
     // outlined above, just the user shader.
     int version;
     EProfile profile;
-    glslang::TInputScanner userInput(numStrings, &strings[1], &lengths[1]);  // no preamble
+    glslang::TInputScanner userInput(numStrings, &strings[numPre], &lengths[numPre]);  // no preamble
     bool versionNotFirstToken;
     bool versionNotFirst = userInput.scanVersion(version, profile, versionNotFirstToken);
     bool versionNotFound = version == 0;
@@ -534,9 +537,12 @@ bool CompileDeferred(
     // Fill in the strings as outlined above.
     strings[0] = parseContext.getPreamble();
     lengths[0] = strlen(strings[0]);
-    strings[numStrings + 1] = "\n int;";
-    lengths[numStrings + 1] = strlen(strings[numStrings + 1]);
-    TInputScanner fullInput(numStrings + 2, strings, lengths, 1, 1);
+    strings[1] = customPreamble;
+    lengths[1] = strlen(strings[1]);
+    assert(2 == numPre);
+    strings[numStrings + numPre] = "\n int;";
+    lengths[numStrings + numPre] = strlen(strings[numStrings + numPre]);
+    TInputScanner fullInput(numStrings + numPre + numPost, strings, lengths, numPre, numPost);
 
     // Push a new symbol allocation scope that will get used for the shader's globals.
     symbolTable.push();
@@ -707,7 +713,7 @@ int ShCompile(
     compiler->infoSink.debug.erase();
 
     TIntermediate intermediate(compiler->getLanguage());
-    bool success = CompileDeferred(compiler, shaderStrings, numStrings, inputLengths, optLevel, resources, defaultVersion, forwardCompatible, messages, intermediate);
+    bool success = CompileDeferred(compiler, shaderStrings, numStrings, inputLengths, "", optLevel, resources, defaultVersion, forwardCompatible, messages, intermediate);
 
     //
     // Call the machine dependent compiler
@@ -966,7 +972,7 @@ public:
 };
 
 TShader::TShader(EShLanguage s) 
-    : pool(0), stage(s)
+    : pool(0), stage(s), preamble("")
 {
     infoSink = new TInfoSink;
     compiler = new TDeferredCompiler(stage, *infoSink);
@@ -993,8 +999,10 @@ bool TShader::parse(const TBuiltInResource* builtInResources, int defaultVersion
     
     pool = new TPoolAllocator();
     SetThreadPoolAllocator(*pool);
+    if (! preamble)
+        preamble = "";
 
-    return CompileDeferred(compiler, strings, numStrings, nullptr, EShOptNone, builtInResources, defaultVersion, forwardCompatible, messages, *intermediate);
+    return CompileDeferred(compiler, strings, numStrings, nullptr, preamble, EShOptNone, builtInResources, defaultVersion, forwardCompatible, messages, *intermediate);
 }
 
 const char* TShader::getInfoLog()

glslang/Public/ShaderLang.h

@@ -263,11 +263,13 @@ bool InitializeProcess();
 // Call once per process to tear down everything
 void FinalizeProcess();
 
-// Make one TShader per shader that you will link into a program.  Then
-// provide the shader through setStrings(), then call parse(), then query
-// the info logs.
+// Make one TShader per shader that you will link into a program.  Then provide
+// the shader through setStrings(), then call parse(), then query the info logs.
+// Optionally use setPreamble() to set a special shader string that will be
+// processed before all others but won't affect the validity of #version.
 //
-// N.B.: Does not yet support having the same TShader instance being linked into multiple programs.
+// N.B.: Does not yet support having the same TShader instance being linked into
+// multiple programs.
 //
 // N.B.: Destruct a linked program *before* destructing the shaders linked into it.
 //
@@ -276,6 +278,7 @@ public:
     explicit TShader(EShLanguage);
     virtual ~TShader();
     void setStrings(const char* const* s, int n) { strings = s; numStrings = n; }
+    void setPreamble(const char* s) { preamble = s; }
     bool parse(const TBuiltInResource*, int defaultVersion, bool forwardCompatible, EShMessages);
 
     const char* getInfoLog();
@@ -290,6 +293,7 @@ protected:
     TIntermediate* intermediate;
     TInfoSink* infoSink;
     const char* const* strings;
+    const char* preamble;
     int numStrings;
 
     friend class TProgram;