Fix #29274: problem compiling cycles opencl kernel from directory with spaces.

Some drivers don't support passing include paths with spaces in them, nor does
the opencl spec specify anything about how to quote/escape such paths, so for
now we just resolved #includes ourselves. Alternative would have been to use c
preprocessor, but this also resolves all #ifdefs, which we do not want.

intern/cycles/util/util_path.cpp

@@ -162,5 +162,46 @@ bool path_read_binary(const string& path, vector<uint8_t>& binary)
 	return true;
 }
 
+static bool path_read_text(const string& path, string& text)
+{
+	vector<uint8_t> binary;
+
+	if(!path_exists(path) || !path_read_binary(path, binary))
+		return false;
+	
+	const char *str = (const char*)&binary[0];
+	size_t size = binary.size();
+	text = string(str, size);
+
+	return true;
+}
+
+string path_source_replace_includes(const string& source_, const string& path)
+{
+	/* our own little c preprocessor that replaces #includes with the file
+	   contents, to work around issue of opencl drivers not supporting
+	   include paths with spaces in them */
+	string source = source_;
+	const string include = "#include \"";
+	size_t n, pos = 0;
+
+	while((n = source.find(include, pos)) != string::npos) {
+		size_t n_start = n + include.size();
+		size_t n_end = source.find("\"", n_start);
+		string filename = source.substr(n_start, n_end - n_start);
+
+		string text, filepath = path_join(path, filename);
+
+		if(path_read_text(filepath, text)) {
+			text = path_source_replace_includes(text, path_dirname(filepath));
+			source.replace(n, n_end + 1 - n, "\n" + text + "\n");
+		}
+		else
+			pos = n_end;
+	}
+
+	return source;
+}
+
 CCL_NAMESPACE_END