LibCore: Add CFileStreamReader, a simple streaming CFile reader.

This is extremely barebones right now, but can be used to easily read binary
data from a CFile piece by piece.

Libraries/LibCore/CFileStreamReader.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <AK/StdLibExtras.h>
+#include <LibCore/CFile.h>
+
+class CFileStreamReader {
+public:
+    CFileStreamReader(CFile& file)
+        : m_file(file)
+    {
+    }
+
+    bool handle_read_failure()
+    {
+        return exchange(m_had_failure, false);
+    }
+
+    template<typename T>
+    CFileStreamReader& operator>>(T& value)
+    {
+        int nread = m_file.read((u8*)&value, sizeof(T));
+        ASSERT(nread == sizeof(T));
+        if (nread != sizeof(T))
+            m_had_failure = true;
+        return *this;
+    }
+
+private:
+    CFile& m_file;
+    bool m_had_failure { false };
+};

Libraries/LibCore/CIODevice.cpp

@@ -22,6 +22,13 @@ const char* CIODevice::error_string() const
     return strerror(m_error);
 }
 
+int CIODevice::read(u8* buffer, int length)
+{
+    auto read_buffer = read(length);
+    memcpy(buffer, read_buffer.data(), length);
+    return read_buffer.size();
+}
+
 ByteBuffer CIODevice::read(int max_size)
 {
     if (m_fd < 0)

Libraries/LibCore/CIODevice.h

@@ -28,6 +28,9 @@ public:
 
     bool has_error() const { return m_error != 0; }
 
+
+    int read(u8* buffer, int length);
+
     ByteBuffer read(int max_size);
     ByteBuffer read_line(int max_size);
     ByteBuffer read_all();