refactor: Modernize AutoFile

* Add m_ prefix to the std::FILE member variable
* Add std namespace where possible, to avoid confusion with member
  functions of the same name.
* Add AutoFile::feof() member function, to be used in place of
  std::feof(AutoFile::Get())
* Simplify fclose() in terms of release()
* Fix typo in the error message in the ignore member function.

Author: MarcoFalke

src/streams.h

@@ -480,73 +480,74 @@ class BitStreamWriter
 class AutoFile
 {
 protected:
-    FILE* file;
+    std::FILE* m_file;
 
 public:
-    explicit AutoFile(FILE* filenew) : file{filenew} {}
+    explicit AutoFile(std::FILE* file) : m_file{file} {}
 
-    ~AutoFile()
-    {
-        fclose();
-    }
+    ~AutoFile() { fclose(); }
 
     // Disallow copies
     AutoFile(const AutoFile&) = delete;
     AutoFile& operator=(const AutoFile&) = delete;
 
+    bool feof() const { return std::feof(m_file); }
+
     int fclose()
     {
-        int retval{0};
-        if (file) {
-            retval = ::fclose(file);
-            file = nullptr;
-        }
-        return retval;
+        if (auto rel{release()}) return std::fclose(rel);
+        return 0;
     }
 
     /** Get wrapped FILE* with transfer of ownership.
      * @note This will invalidate the AutoFile object, and makes it the responsibility of the caller
      * of this function to clean up the returned FILE*.
      */
-    FILE* release()             { FILE* ret = file; file = nullptr; return ret; }
+    std::FILE* release()
+    {
+        std::FILE* ret{m_file};
+        m_file = nullptr;
+        return ret;
+    }
 
     /** Get wrapped FILE* without transfer of ownership.
      * @note Ownership of the FILE* will remain with this class. Use this only if the scope of the
      * AutoFile outlives use of the passed pointer.
      */
-    FILE* Get() const           { return file; }
+    std::FILE* Get() const { return m_file; }
 
     /** Return true if the wrapped FILE* is nullptr, false otherwise.
      */
-    bool IsNull() const         { return (file == nullptr); }
+    bool IsNull() const { return m_file == nullptr; }
 
     //
     // Stream subset
     //
     void read(Span<std::byte> dst)
     {
-        if (!file) throw std::ios_base::failure("AutoFile::read: file handle is nullptr");
-        if (fread(dst.data(), 1, dst.size(), file) != dst.size()) {
-            throw std::ios_base::failure(feof(file) ? "AutoFile::read: end of file" : "AutoFile::read: fread failed");
+        if (!m_file) throw std::ios_base::failure("AutoFile::read: file handle is nullptr");
+        if (std::fread(dst.data(), 1, dst.size(), m_file) != dst.size()) {
+            throw std::ios_base::failure(feof() ? "AutoFile::read: end of file" : "AutoFile::read: fread failed");
         }
     }
 
     void ignore(size_t nSize)
     {
-        if (!file) throw std::ios_base::failure("AutoFile::ignore: file handle is nullptr");
+        if (!m_file) throw std::ios_base::failure("AutoFile::ignore: file handle is nullptr");
         unsigned char data[4096];
         while (nSize > 0) {
             size_t nNow = std::min<size_t>(nSize, sizeof(data));
-            if (fread(data, 1, nNow, file) != nNow)
-                throw std::ios_base::failure(feof(file) ? "AutoFile::ignore: end of file" : "AutoFile::read: fread failed");
+            if (std::fread(data, 1, nNow, m_file) != nNow) {
+                throw std::ios_base::failure(feof() ? "AutoFile::ignore: end of file" : "AutoFile::ignore: fread failed");
+            }
             nSize -= nNow;
         }
     }
 
     void write(Span<const std::byte> src)
     {
-        if (!file) throw std::ios_base::failure("AutoFile::write: file handle is nullptr");
-        if (fwrite(src.data(), 1, src.size(), file) != src.size()) {
+        if (!m_file) throw std::ios_base::failure("AutoFile::write: file handle is nullptr");
+        if (std::fwrite(src.data(), 1, src.size(), m_file) != src.size()) {
             throw std::ios_base::failure("AutoFile::write: write failed");
         }
     }