1 files changed, 110 insertions, 0 deletions
diff --git a/include/ruby/io/buffer.h b/include/ruby/io/buffer.h
new file mode 100644
index 0000000000..e4d98bf051
--- /dev/null
+++ b/include/ruby/io/buffer.h
@@ -0,0 +1,110 @@
+#ifndef RUBY_IO_BUFFER_H
+#define RUBY_IO_BUFFER_H
+/**
+ * @file
+ * @author     Samuel Williams
+ * @date       Fri  2 Jul 2021 16:29:01 NZST
+ * @copyright  Copyright (C) 2021 Samuel Williams
+ * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
+ *             Permission  is hereby  granted,  to  either redistribute  and/or
+ *             modify this file, provided that  the conditions mentioned in the
+ *             file COPYING are met.  Consult the file for details.
+ */
+
+#pragma once
+
+#include "ruby/ruby.h"
+#include "ruby/internal/config.h"
+
+RBIMPL_SYMBOL_EXPORT_BEGIN()
+
+// WARNING: This entire interface is experimental and may change in the future!
+#define RB_IO_BUFFER_EXPERIMENTAL 1
+
+#define RUBY_IO_BUFFER_VERSION 2
+
+// The `IO::Buffer` class.
+RUBY_EXTERN VALUE rb_cIOBuffer;
+
+// The operating system page size.
+RUBY_EXTERN size_t RUBY_IO_BUFFER_PAGE_SIZE;
+
+// The default buffer size, usually a (small) multiple of the page size.
+// Can be overridden by the RUBY_IO_BUFFER_DEFAULT_SIZE environment variable.
+RUBY_EXTERN size_t RUBY_IO_BUFFER_DEFAULT_SIZE;
+
+// Represents the internal state of the buffer.
+// More than one flag can be set at a time.
+enum rb_io_buffer_flags {
+    // The memory in the buffer is owned by someone else.
+    // More specifically, it means that someone else owns the buffer and we shouldn't try to resize it.
+    RB_IO_BUFFER_EXTERNAL = 1,
+    // The memory in the buffer is allocated internally.
+    RB_IO_BUFFER_INTERNAL = 2,
+    // The memory in the buffer is mapped.
+    // A non-private mapping is marked as external.
+    RB_IO_BUFFER_MAPPED = 4,
+
+    // A mapped buffer that is also shared.
+    RB_IO_BUFFER_SHARED = 8,
+
+    // The buffer is locked and cannot be resized.
+    // More specifically, it means we can't change the base address or size.
+    // A buffer is typically locked before a system call that uses the data.
+    RB_IO_BUFFER_LOCKED = 32,
+
+    // The buffer mapping is private and will not impact other processes or the underlying file.
+    RB_IO_BUFFER_PRIVATE = 64,
+
+    // The buffer is read-only and cannot be modified.
+    RB_IO_BUFFER_READONLY = 128,
+
+    // The buffer is backed by a file.
+    RB_IO_BUFFER_FILE = 256,
+};
+
+// Represents the endian of the data types.
+enum rb_io_buffer_endian {
+    // The least significant units are put first.
+    RB_IO_BUFFER_LITTLE_ENDIAN = 4,
+    RB_IO_BUFFER_BIG_ENDIAN = 8,
+
+#if defined(WORDS_BIGENDIAN)
+    RB_IO_BUFFER_HOST_ENDIAN = RB_IO_BUFFER_BIG_ENDIAN,
+#else
+    RB_IO_BUFFER_HOST_ENDIAN = RB_IO_BUFFER_LITTLE_ENDIAN,
+#endif
+
+    RB_IO_BUFFER_NETWORK_ENDIAN = RB_IO_BUFFER_BIG_ENDIAN
+};
+
+VALUE rb_io_buffer_new(void *base, size_t size, enum rb_io_buffer_flags flags);
+VALUE rb_io_buffer_map(VALUE io, size_t size, rb_off_t offset, enum rb_io_buffer_flags flags);
+
+VALUE rb_io_buffer_lock(VALUE self);
+VALUE rb_io_buffer_unlock(VALUE self);
+int rb_io_buffer_try_unlock(VALUE self);
+
+VALUE rb_io_buffer_free(VALUE self);
+VALUE rb_io_buffer_free_locked(VALUE self);
+
+// Access the internal buffer and flags. Validates the pointers.
+// The points may not remain valid if the source buffer is manipulated.
+// Consider using rb_io_buffer_lock if needed.
+enum rb_io_buffer_flags rb_io_buffer_get_bytes(VALUE self, void **base, size_t *size);
+void rb_io_buffer_get_bytes_for_reading(VALUE self, const void **base, size_t *size);
+void rb_io_buffer_get_bytes_for_writing(VALUE self, void **base, size_t *size);
+
+VALUE rb_io_buffer_transfer(VALUE self);
+void rb_io_buffer_resize(VALUE self, size_t size);
+void rb_io_buffer_clear(VALUE self, uint8_t value, size_t offset, size_t length);
+
+// The length is the minimum required length.
+VALUE rb_io_buffer_read(VALUE self, VALUE io, size_t length, size_t offset);
+VALUE rb_io_buffer_pread(VALUE self, VALUE io, rb_off_t from, size_t length, size_t offset);
+VALUE rb_io_buffer_write(VALUE self, VALUE io, size_t length, size_t offset);
+VALUE rb_io_buffer_pwrite(VALUE self, VALUE io, rb_off_t from, size_t length, size_t offset);
+
+RBIMPL_SYMBOL_EXPORT_END()
+
+#endif  /* RUBY_IO_BUFFER_H */