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+/* This file is derived from source code used in MIT's 6.828
+   course.  The original copyright notice is reproduced in full
+   below. */
+
+/*
+ * Copyright (C) 1997 Massachusetts Institute of Technology 
+ *
+ * This software is being provided by the copyright holders under the
+ * following license. By obtaining, using and/or copying this software,
+ * you agree that you have read, understood, and will comply with the
+ * following terms and conditions:
+ *
+ * Permission to use, copy, modify, distribute, and sell this software
+ * and its documentation for any purpose and without fee or royalty is
+ * hereby granted, provided that the full text of this NOTICE appears on
+ * ALL copies of the software and documentation or portions thereof,
+ * including modifications, that you make.
+ *
+ * THIS SOFTWARE IS PROVIDED "AS IS," AND COPYRIGHT HOLDERS MAKE NO
+ * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED. BY WAY OF EXAMPLE,
+ * BUT NOT LIMITATION, COPYRIGHT HOLDERS MAKE NO REPRESENTATIONS OR
+ * WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR
+ * THAT THE USE OF THE SOFTWARE OR DOCUMENTATION WILL NOT INFRINGE ANY
+ * THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS. COPYRIGHT
+ * HOLDERS WILL BEAR NO LIABILITY FOR ANY USE OF THIS SOFTWARE OR
+ * DOCUMENTATION.
+ *
+ * The name and trademarks of copyright holders may NOT be used in
+ * advertising or publicity pertaining to the software without specific,
+ * written prior permission. Title to copyright in this software and any
+ * associated documentation will at all times remain with copyright
+ * holders. See the file AUTHORS which should have accompanied this software
+ * for a list of all copyright holders.
+ *
+ * This file may be derived from previously copyrighted software. This
+ * copyright applies only to those changes made by the copyright
+ * holders listed in the AUTHORS file. The rest of this file is covered by
+ * the copyright notices, if any, listed below.
+ */
+
+#ifndef THREADS_IO_H
+#define THREADS_IO_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+/* Reads and returns a byte from PORT. */
+static inline uint8_t
+inb (uint16_t port)
+{
+  /* See [IA32-v2a] "IN". */
+  uint8_t data;
+  asm volatile ("inb %w1,%0" : "=a" (data) : "d" (port));
+  return data;
+}
+
+/* Reads CNT bytes from PORT, one after another, and stores them
+   into the buffer starting at ADDR. */
+static inline void
+insb (uint16_t port, void *addr, size_t cnt)
+{
+  /* See [IA32-v2a] "INS". */
+  asm volatile ("cld; repne; insb"
+                : "=D" (addr), "=c" (cnt)
+                : "d" (port), "0" (addr), "1" (cnt)
+                : "memory", "cc");
+}
+
+/* Reads and returns 16 bits from PORT. */
+static inline uint16_t
+inw (uint16_t port)
+{
+  uint16_t data;
+  /* See [IA32-v2a] "IN". */
+  asm volatile ("inw %w1,%0" : "=a" (data) : "d" (port));
+  return data;
+}
+
+/* Reads CNT 16-bit (halfword) units from PORT, one after
+   another, and stores them into the buffer starting at ADDR. */
+static inline void
+insw (uint16_t port, void *addr, size_t cnt)
+{
+  /* See [IA32-v2a] "INS". */
+  asm volatile ("cld; repne; insw"
+                : "=D" (addr), "=c" (cnt)
+                : "d" (port), "0" (addr), "1" (cnt)
+                : "memory", "cc");
+}
+
+/* Reads and returns 32 bits from PORT. */
+static inline uint32_t
+inl (uint16_t port)
+{
+  /* See [IA32-v2a] "IN". */
+  uint32_t data;
+  asm volatile ("inl %w1,%0" : "=a" (data) : "d" (port));
+  return data;
+}
+
+/* Reads CNT 32-bit (word) units from PORT, one after another,
+   and stores them into the buffer starting at ADDR. */
+static inline void
+insl (uint16_t port, void *addr, size_t cnt)
+{
+  /* See [IA32-v2a] "INS". */
+  asm volatile ("cld; repne; insl"
+                : "=D" (addr), "=c" (cnt)
+                : "d" (port), "0" (addr), "1" (cnt)
+                : "memory", "cc");
+}
+
+/* Writes byte DATA to PORT. */
+static inline void
+outb (uint16_t port, uint8_t data)
+{
+  /* See [IA32-v2b] "OUT". */
+  asm volatile ("outb %0,%w1" : : "a" (data), "d" (port));
+}
+
+/* Writes to PORT each byte of data in the CNT-byte buffer
+   starting at ADDR. */
+static inline void
+outsb (uint16_t port, const void *addr, size_t cnt)
+{
+  /* See [IA32-v2b] "OUTS". */
+  asm volatile ("cld; repne; outsb"
+                : "=S" (addr), "=c" (cnt)
+                : "d" (port), "0" (addr), "1" (cnt)
+                : "cc");
+}
+
+/* Writes the 16-bit DATA to PORT. */
+static inline void
+outw (uint16_t port, uint16_t data)
+{
+  /* See [IA32-v2b] "OUT". */
+  asm volatile ("outw %0,%w1" : : "a" (data), "d" (port));
+}
+
+/* Writes to PORT each 16-bit unit (halfword) of data in the
+   CNT-halfword buffer starting at ADDR. */
+static inline void
+outsw (uint16_t port, const void *addr, size_t cnt)
+{
+  /* See [IA32-v2b] "OUTS". */
+  asm volatile ("cld; repne; outsw"
+                : "=S" (addr), "=c" (cnt)
+                : "d" (port), "0" (addr), "1" (cnt)
+                : "cc");
+}
+
+/* Writes the 32-bit DATA to PORT. */
+static inline void
+outl (uint16_t port, uint32_t data)
+{
+  /* See [IA32-v2b] "OUT". */
+  asm volatile ("outl %0,%w1" : : "a" (data), "d" (port));
+}
+
+/* Writes to PORT each 32-bit unit (word) of data in the CNT-word
+   buffer starting at ADDR. */
+static inline void
+outsl (uint16_t port, const void *addr, size_t cnt)
+{
+  /* See [IA32-v2b] "OUTS". */
+  asm volatile ("cld; repne; outsl"
+                : "=S" (addr), "=c" (cnt)
+                : "d" (port), "0" (addr), "1" (cnt)
+                : "cc");
+}
+
+#endif /* threads/io.h */