.\" @ROL64_
.\" @ROR64_
.\"
+.\" ENDSWAP16
+.\" ENDSWAP32
+.\" ENDSWAP64
+.\"
+.\" BTOH16
+.\" LTOH16
+.\" HTOB16
+.\" HTOL16
+.\" BTOH32
+.\" LTOH32
+.\" HTOB32
+.\" HTOL32
+.\" BTOH64
+.\" LTOH64
+.\" HTOB64
+.\" HTOL64
+.\"
.\" @GETBYTE
.\" @PUTBYTE
.\"
.I n
places.
.
+.SS "Byte order conversions"
+For each size suffix
+.IR w ,
+the macro invocation
+.BI ENDSWAP w ( x )
+returns the
+.IR w -bit
+value
+.IR x
+with its bytes reversed. The
+.B ENDSWAP8
+macro does nothing (except truncate its operand to 8 bits), but is
+provided for the sake of completeness.
+.PP
+A
+.I big-endian
+representation stores the most significant octet of an integer at the
+lowest address, with the following octets in decreasing order of
+significance. A
+.I little-endian
+representation instead stores the
+.I least
+significant octet at the lowest address, with the following octets in
+increasing order of significance. An environment has a preferred order
+for arranging the constituent octets of an integer of some given size in
+memory; this might be either the big- or little-endian representation
+just described, or something else strange.
+.PP
+It might be possible to rearrange the bits in an integer so that, when
+that integer is stored to memory in the environment's preferred manner,
+you end up with the big- or little-endian representation of the original
+integer; and, similarly, it might be possible to load a big- or
+little-endian representation of an integer into a variable using the
+environment's preferred ordering and then rearrange the bits so as to
+recover the integer value originally represented. If the environment is
+sufficiently strange, these things might not be possible, but this is
+actually quite rare.
+.PP
+Say that an integer has been converted to
+.I big-
+or
+.I "little-endian form"
+if, when it is stored in memory in the environment's preferred manner,
+one ends up with a big- or little-endian representation of the original
+integer. Equivalently, if one starts with a big- or little-endian
+representation of some integer, and loads it into a variable using the
+environment's preferred manner, one ends up with the big- or
+little-endian form of the original integer.
+.PP
+If these things are possible, then the following macros are defined.
+.TP
+.BI HTOL w ( x )
+Convert a
+.IR w -bit
+integer
+.I x
+to little-endian form.
+.TP
+.BI HTOB w ( x )
+Convert a
+.IR w -bit
+integer
+.I x
+to big-endian form.
+.TP
+.BI LTOH w ( x )
+Convert a
+.IR w -bit
+integer
+.I x
+from little-endian form.
+.TP
+.BI BTOH w ( x )
+Convert a
+.IR w -bit
+integer
+.I x
+from big-endian form.
+.
.SS "Load and store"
The macro invocation
.BI GETBYTE( p ", " o )
} while (0)
#endif
+/* --- Endianness swapping --- */
+
+#ifndef ENDSWAP8
+# define ENDSWAP8(x) U8(x)
+#endif
+#ifndef ENDSWAP16
+# define ENDSWAP16(x) \
+ ((((uint16)(x) >> 8)&0xff) | \
+ (((uint16)(x)&0xff) << 8))
+#endif
+#ifndef ENDSWAP24
+# define ENDSWAP24(x) \
+ ((((uint24)(x) >> 16)&0xff) | \
+ ((uint24)(x)&0xff00) | \
+ ((uint24)((x)&0xff) << 16))
+#endif
+#ifndef ENDSWAP32
+# define ENDSWAP32(x) \
+ (ENDSWAP16(((uint32)(x) >> 16)&0xffff) | \
+ ((uint32)ENDSWAP16((x)&0xffff) << 16))
+#endif
+#if defined(HAVE_UINT64) && !defined(ENDSWAP64)
+# define ENDSWAP64(x) \
+ (ENDSWAP32(((uint64)(x) >> 32)&0xffffffff) | \
+ ((uint64)ENDSWAP32((x)&0xffffffff) << 32))
+#endif
+#ifdef HAVE_UINT64
+# define ENDSWAP64_(z, x) \
+ ((z).i = ENDSWAP64((x).i))
+#else
+# define ENDSWAP64_(z, x) \
+ ((z).lo = ENDSWAP32((x).hi), \
+ (z).hi = ENDSWAP32((x).lo))
+#endif
+
+#define MLIB_LITTLE_ENDIAN 1234
+#define MLIB_BIG_ENDIAN 4321
+#if defined(__ORDER_LITTLE_ENDIAN__) && \
+ __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+# define MLIB_BYTE_ORDER MLIB_LITTLE_ENDIAN
+#elif defined(__ORDER_BIG_ENDIAN__) && \
+ __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+# define MLIB_BYTE_ORDER MLIB_BIG_ENDIAN
+#endif
+
+#if MLIB_BYTE_ORDER == MLIB_LITTLE_ENDIAN
+# define HTOL16(x) (x)
+# define LTOH16(x) (x)
+# define HTOB16(x) ENDSWAP16(x)
+# define BTOH16(x) ENDSWAP16(x)
+# define HTOL24(x) (x)
+# define LTOH24(x) (x)
+# define HTOB24(x) ENDSWAP24(x)
+# define BTOH24(x) ENDSWAP24(x)
+# define HTOL32(x) (x)
+# define LTOH32(x) (x)
+# define HTOB32(x) ENDSWAP32(x)
+# define BTOH32(x) ENDSWAP32(x)
+# ifdef HAVE_UINT64
+# define HTOL64(x) (x)
+# define LTOH64(x) (x)
+# define HTOB64(x) ENDSWAP64(x)
+# define BTOH64(x) ENDSWAP64(x)
+# endif
+# define HTOL64_(z, x) ASSIGN64(z, x)
+# define LTOH64_(z, x) ASSIGN64(z, x)
+# define HTOB64_(z, x) ENDSWAP64_(z, x)
+# define BTOH64_(z, x) ENDSWAP64_(z, x)
+#elif MLIB_BYTE_ORDER == MLIB_BIG_ENDIAN
+# define HTOL16(x) ENDSWAP16(x)
+# define LTOH16(x) ENDSWAP16(x)
+# define HTOB16(x) (x)
+# define BTOH16(x) (x)
+# define HTOL24(x) ENDSWAP24(x)
+# define LTOH24(x) ENDSWAP24(x)
+# define HTOB24(x) (x)
+# define BTOH24(x) (x)
+# define HTOL32(x) ENDSWAP32(x)
+# define LTOH32(x) ENDSWAP32(x)
+# define HTOB32(x) (x)
+# define BTOH32(x) (x)
+# ifdef HAVE_UINT64
+# define HTOL64(x) ENDSWAP64(x)
+# define LTOH64(x) ENDSWAP64(x)
+# define HTOB64(x) (x)
+# define BTOH64(x) (x)
+# define HTOL64_(z, x) ENDSWAP64_(z, x)
+# define LTOH64_(z, x) ENDSWAP64_(z, x)
+# define HTOB64_(z, x) ((z).i = (x).i)
+# define BTOH64_(z, x) ((z).i = (x).i)
+# endif
+# define HTOL64_(z, x) ENDSWAP64_(z, x)
+# define LTOH64_(z, x) ENDSWAP64_(z, x)
+# define HTOB64_(z, x) ASSIGN64(z, x)
+# define BTOH64_(z, x) ASSIGN64(z, x)
+#endif
+
/* --- Storage and retrieval --- */
#define GETBYTE(p, o) (((octet *)(p))[o] & MASK8)