lib: establish Zircon libc++ and KTL foundation

1 files changed, 50 insertions, 0 deletions

diff --git a/lib/libc/include/multi-file.h b/lib/libc/include/multi-file.h
new file mode 100644
index 0000000..a04a031
--- /dev/null
+++ b/lib/libc/include/multi-file.h
@@ -0,0 +1,50 @@
+// Copyright 2022 The Fuchsia Authors
+//
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT
+
+#ifndef ZIRCON_KERNEL_LIB_LIBC_INCLUDE_MULTI_FILE_H_
+#define ZIRCON_KERNEL_LIB_LIBC_INCLUDE_MULTI_FILE_H_
+
+#include <stdio.h>
+
+#include <ktl/array.h>
+#include <ktl/forward.h>
+#include <ktl/string_view.h>
+#include <ktl/type_traits.h>
+
+// MultiFile broadcasts Write calls across multiple FILE* pointers.  Each
+// pointer is ignored if it's null.  MultiFile::Write always returns success,
+// ignoring any failures or short writes from the underlying FILE objects.
+template <size_t N>
+class MultiFile : public FILE {
+ public:
+  using FileArray = ktl::array<FILE*, N>;
+
+  constexpr MultiFile() : FILE{this} {}
+
+  constexpr explicit MultiFile(const FileArray& files) : FILE{this}, files_(files) {}
+
+  constexpr MultiFile(const MultiFile& other) : MultiFile(other.files_) {}
+
+  FileArray& files() { return files_; }
+  const FileArray& files() const { return files_; }
+
+  int Write(ktl::string_view str) {
+    for (FILE* file : files_) {
+      if (file) {
+        file->Write(str);
+      }
+    }
+    return static_cast<int>(str.size());
+  }
+
+ private:
+  FileArray files_ = {};
+};
+
+template <size_t N>
+MultiFile(const ktl::array<FILE*, N>&) -> MultiFile<N>;
+
+#endif  // ZIRCON_KERNEL_LIB_LIBC_INCLUDE_MULTI_FILE_H_