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 @@ class CIODevice : public CObject {
 
  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();