implemented rfile reading

simulator_SIC_XE/src/string_reader.cpp

@@ -0,0 +1,27 @@
+#include "string_reader.h"
+
+StringReader::StringReader(const std::string &s)
+    : in(s)
+{}
+
+StringReader::~StringReader() = default;
+
+int StringReader::readByte() {
+    char c;
+    if (!in.get(c)) return -1;
+    return static_cast<unsigned char>(c);
+}
+
+bool StringReader::readBytes(uint8_t* buf, size_t len) {
+    in.read(reinterpret_cast<char*>(buf), static_cast<std::streamsize>(len));
+    return static_cast<size_t>(in.gcount()) == len;
+}
+
+std::string StringReader::readString(size_t len) {
+    std::string s;
+    s.resize(len);
+    in.read(reinterpret_cast<char*>(&s[0]), static_cast<std::streamsize>(len));
+    std::streamsize got = in.gcount();
+    if (static_cast<size_t>(got) < len) s.resize(static_cast<size_t>(got));
+    return s;
+}