initial checkin of SkSL compiler

src/sksl/SkSLMain.cpp

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "stdio.h"
+#include <fstream>
+#include "SkSLCompiler.h"
+
+/**
+ * Very simple standalone executable to facilitate testing.
+ */
+int main(int argc, const char** argv) {
+    if (argc != 3) {
+        printf("usage: skslc <input> <output>\n");
+        exit(1);
+    }
+    SkSL::Program::Kind kind;
+    size_t len = strlen(argv[1]);
+    if (len > 5 && !strcmp(argv[1] + strlen(argv[1]) - 5, ".vert")) {
+        kind = SkSL::Program::kVertex_Kind;
+    } else if (len > 5 && !strcmp(argv[1] + strlen(argv[1]) - 5, ".frag")) {
+        kind = SkSL::Program::kFragment_Kind;
+    } else {
+        printf("input filename must end in '.vert' or '.frag'\n");
+        exit(1);
+    }
+
+    std::ifstream in(argv[1]);
+    std::string text((std::istreambuf_iterator<char>(in)),
+                     std::istreambuf_iterator<char>());
+    if (in.rdstate()) {
+        printf("error reading '%s'\n", argv[1]);
+        exit(2);
+    }
+    std::ofstream out(argv[2], std::ofstream::binary);
+    SkSL::Compiler compiler;
+    if (!compiler.toSPIRV(kind, text, out)) {
+        printf("%s", compiler.errorText().c_str());
+        exit(3);
+    }
+    if (out.rdstate()) {
+        printf("error writing '%s'\n", argv[2]);
+        exit(4);
+    }
+}