lttng lib: portable bitfield read/write header

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/lttng/lib/bitfield.h

+#ifndef _BABELTRACE_BITFIELD_H
+#define _BABELTRACE_BITFIELD_H
+
+/*
+ * BabelTrace
+ *
+ * Bitfields read/write functions.
+ *
+ * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ */
+
+#include "../ltt-endian.h"
+
+#ifndef CHAR_BIT
+#define CHAR_BIT 8
+#endif
+
+/* We can't shift a int from 32 bit, >> 32 and << 32 on int is undefined */
+#define _bt_piecewise_rshift(_v, _shift)				\
+({									\
+	typeof(_v) ___v = (_v);						\
+	typeof(_shift) ___shift = (_shift);				\
+	unsigned long sb = (___shift) / (sizeof(___v) * CHAR_BIT - 1);	\
+	unsigned long final = (___shift) % (sizeof(___v) * CHAR_BIT - 1); \
+									\
+	for (; sb; sb--)						\
+		___v >>= sizeof(___v) * CHAR_BIT - 1;			\
+	___v >>= final;							\
+})
+
+#define _bt_piecewise_lshift(_v, _shift)				\
+({									\
+	typeof(_v) ___v = (_v);						\
+	typeof(_shift) ___shift = (_shift);				\
+	unsigned long sb = (___shift) / (sizeof(___v) * CHAR_BIT - 1);	\
+	unsigned long final = (___shift) % (sizeof(___v) * CHAR_BIT - 1); \
+									\
+	for (; sb; sb--)						\
+		___v <<= sizeof(___v) * CHAR_BIT - 1;			\
+	___v <<= final;							\
+})
+
+#define _bt_is_signed_type(type)	(((type)(-1)) < 0)
+
+#define _bt_unsigned_cast(type, v)					\
+({									\
+	(sizeof(v) < sizeof(type)) ?					\
+		((type) (v)) & (~(~(type) 0 << (sizeof(v) * CHAR_BIT))) : \
+		(type) (v);						\
+})
+
+/*
+ * bt_bitfield_write - write integer to a bitfield in native endianness
+ *
+ * Save integer to the bitfield, which starts at the "start" bit, has "len"
+ * bits.
+ * The inside of a bitfield is from high bits to low bits.
+ * Uses native endianness.
+ * For unsigned "v", pad MSB with 0 if bitfield is larger than v.
+ * For signed "v", sign-extend v if bitfield is larger than v.
+ *
+ * On little endian, bytes are placed from the less significant to the most
+ * significant. Also, consecutive bitfields are placed from lower bits to higher
+ * bits.
+ *
+ * On big endian, bytes are places from most significant to less significant.
+ * Also, consecutive bitfields are placed from higher to lower bits.
+ */
+
+#define _bt_bitfield_write_le(_ptr, type, _start, _length, _v)		\
+do {									\
+	typeof(_v) __v = (_v);						\
+	type *__ptr = (void *) (_ptr);					\
+	unsigned long __start = (_start), __length = (_length);		\
+	type mask, cmask;						\
+	unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */	\
+	unsigned long start_unit, end_unit, this_unit;			\
+	unsigned long end, cshift; /* cshift is "complement shift" */	\
+									\
+	if (!__length)							\
+		break;							\
+									\
+	end = __start + __length;					\
+	start_unit = __start / ts;					\
+	end_unit = (end + (ts - 1)) / ts;				\
+									\
+	/* Trim v high bits */						\
+	if (__length < sizeof(__v) * CHAR_BIT)				\
+		__v &= ~((~(typeof(__v)) 0) << __length);		\
+									\
+	/* We can now append v with a simple "or", shift it piece-wise */ \
+	this_unit = start_unit;						\
+	if (start_unit == end_unit - 1) {				\
+		mask = ~((~(type) 0) << (__start % ts));		\
+		if (end % ts)						\
+			mask |= (~(type) 0) << (end % ts);		\
+		cmask = (type) __v << (__start % ts);			\
+		cmask &= ~mask;						\
+		__ptr[this_unit] &= mask;				\
+		__ptr[this_unit] |= cmask;				\
+		break;							\
+	}								\
+	if (__start % ts) {						\
+		cshift = __start % ts;					\
+		mask = ~((~(type) 0) << cshift);			\
+		cmask = (type) __v << cshift;				\
+		cmask &= ~mask;						\
+		__ptr[this_unit] &= mask;				\
+		__ptr[this_unit] |= cmask;				\
+		__v = _bt_piecewise_rshift(__v, ts - cshift);		\
+		__start += ts - cshift;					\
+		this_unit++;						\
+	}								\
+	for (; this_unit < end_unit - 1; this_unit++) {			\
+		__ptr[this_unit] = (type) __v;				\
+		__v = _bt_piecewise_rshift(__v, ts);			\
+		__start += ts;						\
+	}								\
+	if (end % ts) {							\
+		mask = (~(type) 0) << (end % ts);			\
+		cmask = (type) __v;					\
+		cmask &= ~mask;						\
+		__ptr[this_unit] &= mask;				\
+		__ptr[this_unit] |= cmask;				\
+	} else								\
+		__ptr[this_unit] = (type) __v;				\
+} while (0)
+
+#define _bt_bitfield_write_be(_ptr, type, _start, _length, _v)		\
+do {									\
+	typeof(_v) __v = (_v);						\
+	type *__ptr = (void *) (_ptr);					\
+	unsigned long __start = (_start), __length = (_length);		\
+	type mask, cmask;						\
+	unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */	\
+	unsigned long start_unit, end_unit, this_unit;			\
+	unsigned long end, cshift; /* cshift is "complement shift" */	\
+									\
+	if (!__length)							\
+		break;							\
+									\
+	end = __start + __length;					\
+	start_unit = __start / ts;					\
+	end_unit = (end + (ts - 1)) / ts;				\
+									\
+	/* Trim v high bits */						\
+	if (__length < sizeof(__v) * CHAR_BIT)				\
+		__v &= ~((~(typeof(__v)) 0) << __length);		\
+									\
+	/* We can now append v with a simple "or", shift it piece-wise */ \
+	this_unit = end_unit - 1;					\
+	if (start_unit == end_unit - 1) {				\
+		mask = ~((~(type) 0) << ((ts - (end % ts)) % ts));	\
+		if (__start % ts)					\
+			mask |= (~((type) 0)) << (ts - (__start % ts));	\
+		cmask = (type) __v << ((ts - (end % ts)) % ts);		\
+		cmask &= ~mask;						\
+		__ptr[this_unit] &= mask;				\
+		__ptr[this_unit] |= cmask;				\
+		break;							\
+	}								\
+	if (end % ts) {							\
+		cshift = end % ts;					\
+		mask = ~((~(type) 0) << (ts - cshift));			\
+		cmask = (type) __v << (ts - cshift);			\
+		cmask &= ~mask;						\
+		__ptr[this_unit] &= mask;				\
+		__ptr[this_unit] |= cmask;				\
+		__v = _bt_piecewise_rshift(__v, cshift);		\
+		end -= cshift;						\
+		this_unit--;						\
+	}								\
+	for (; (long) this_unit >= (long) start_unit + 1; this_unit--) { \
+		__ptr[this_unit] = (type) __v;				\
+		__v = _bt_piecewise_rshift(__v, ts);			\
+		end -= ts;						\
+	}								\
+	if (__start % ts) {						\
+		mask = (~(type) 0) << (ts - (__start % ts));		\
+		cmask = (type) __v;					\
+		cmask &= ~mask;						\
+		__ptr[this_unit] &= mask;				\
+		__ptr[this_unit] |= cmask;				\
+	} else								\
+		__ptr[this_unit] = (type) __v;				\
+} while (0)
+
+/*
+ * bt_bitfield_write - write integer to a bitfield in native endianness
+ * bt_bitfield_write_le - write integer to a bitfield in little endian
+ * bt_bitfield_write_be - write integer to a bitfield in big endian
+ */
+
+#if (__BYTE_ORDER == __LITTLE_ENDIAN)
+
+#define bt_bitfield_write(ptr, type, _start, _length, _v)		\
+	_bt_bitfield_write_le(ptr, type, _start, _length, _v)
+
+#define bt_bitfield_write_le(ptr, type, _start, _length, _v)		\
+	_bt_bitfield_write_le(ptr, type, _start, _length, _v)
+	
+#define bt_bitfield_write_be(ptr, type, _start, _length, _v)		\
+	_bt_bitfield_write_be(ptr, unsigned char, _start, _length, _v)
+
+#elif (__BYTE_ORDER == __BIG_ENDIAN)
+
+#define bt_bitfield_write(ptr, type, _start, _length, _v)		\
+	_bt_bitfield_write_be(ptr, type, _start, _length, _v)
+
+#define bt_bitfield_write_le(ptr, type, _start, _length, _v)		\
+	_bt_bitfield_write_le(ptr, unsigned char, _start, _length, _v)
+	
+#define bt_bitfield_write_be(ptr, type, _start, _length, _v)		\
+	_bt_bitfield_write_be(ptr, type, _start, _length, _v)
+
+#else /* (BYTE_ORDER == PDP_ENDIAN) */
+
+#error "Byte order not supported"
+
+#endif
+
+#define _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)	\
+do {									\
+	typeof(*(_vptr)) *__vptr = (_vptr);				\
+	typeof(*__vptr) __v;						\
+	type *__ptr = (void *) (_ptr);					\
+	unsigned long __start = (_start), __length = (_length);		\
+	type mask, cmask;						\
+	unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */	\
+	unsigned long start_unit, end_unit, this_unit;			\
+	unsigned long end, cshift; /* cshift is "complement shift" */	\
+									\
+	if (!__length) {						\
+		*__vptr = 0;						\
+		break;							\
+	}								\
+									\
+	end = __start + __length;					\
+	start_unit = __start / ts;					\
+	end_unit = (end + (ts - 1)) / ts;				\
+									\
+	this_unit = end_unit - 1;					\
+	if (_bt_is_signed_type(typeof(__v))				\
+	    && (__ptr[this_unit] & ((type) 1 << ((end % ts ? : ts) - 1)))) \
+		__v = ~(typeof(__v)) 0;					\
+	else								\
+		__v = 0;						\
+	if (start_unit == end_unit - 1) {				\
+		cmask = __ptr[this_unit];				\
+		cmask >>= (__start % ts);				\
+		if ((end - __start) % ts) {				\
+			mask = ~((~(type) 0) << (end - __start));	\
+			cmask &= mask;					\
+		}							\
+		__v = _bt_piecewise_lshift(__v, end - __start);		\
+		__v |= _bt_unsigned_cast(typeof(__v), cmask);		\
+		*__vptr = __v;						\
+		break;							\
+	}								\
+	if (end % ts) {							\
+		cshift = end % ts;					\
+		mask = ~((~(type) 0) << cshift);			\
+		cmask = __ptr[this_unit];				\
+		cmask &= mask;						\
+		__v = _bt_piecewise_lshift(__v, cshift);		\
+		__v |= _bt_unsigned_cast(typeof(__v), cmask);		\
+		end -= cshift;						\
+		this_unit--;						\
+	}								\
+	for (; (long) this_unit >= (long) start_unit + 1; this_unit--) { \
+		__v = _bt_piecewise_lshift(__v, ts);			\
+		__v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
+		end -= ts;						\
+	}								\
+	if (__start % ts) {						\
+		mask = ~((~(type) 0) << (ts - (__start % ts)));		\
+		cmask = __ptr[this_unit];				\
+		cmask >>= (__start % ts);				\
+		cmask &= mask;						\
+		__v = _bt_piecewise_lshift(__v, ts - (__start % ts));	\
+		__v |= _bt_unsigned_cast(typeof(__v), cmask);		\
+	} else {							\
+		__v = _bt_piecewise_lshift(__v, ts);			\
+		__v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
+	}								\
+	*__vptr = __v;							\
+} while (0)
+
+#define _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)	\
+do {									\
+	typeof(*(_vptr)) *__vptr = (_vptr);				\
+	typeof(*__vptr) __v;						\
+	type *__ptr = (void *) (_ptr);					\
+	unsigned long __start = (_start), __length = (_length);		\
+	type mask, cmask;						\
+	unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */	\
+	unsigned long start_unit, end_unit, this_unit;			\
+	unsigned long end, cshift; /* cshift is "complement shift" */	\
+									\
+	if (!__length) {						\
+		*__vptr = 0;						\
+		break;							\
+	}								\
+									\
+	end = __start + __length;					\
+	start_unit = __start / ts;					\
+	end_unit = (end + (ts - 1)) / ts;				\
+									\
+	this_unit = start_unit;						\
+	if (_bt_is_signed_type(typeof(__v))				\
+	    && (__ptr[this_unit] & ((type) 1 << (ts - (__start % ts) - 1)))) \
+		__v = ~(typeof(__v)) 0;					\
+	else								\
+		__v = 0;						\
+	if (start_unit == end_unit - 1) {				\
+		cmask = __ptr[this_unit];				\
+		cmask >>= (ts - (end % ts)) % ts;			\
+		if ((end - __start) % ts) {				\
+			mask = ~((~(type) 0) << (end - __start));	\
+			cmask &= mask;					\
+		}							\
+		__v = _bt_piecewise_lshift(__v, end - __start);		\
+		__v |= _bt_unsigned_cast(typeof(__v), cmask);		\
+		*__vptr = __v;						\
+		break;							\
+	}								\
+	if (__start % ts) {						\
+		cshift = __start % ts;					\
+		mask = ~((~(type) 0) << (ts - cshift));			\
+		cmask = __ptr[this_unit];				\
+		cmask &= mask;						\
+		__v = _bt_piecewise_lshift(__v, ts - cshift);		\
+		__v |= _bt_unsigned_cast(typeof(__v), cmask);		\
+		__start += ts - cshift;					\
+		this_unit++;						\
+	}								\
+	for (; this_unit < end_unit - 1; this_unit++) {			\
+		__v = _bt_piecewise_lshift(__v, ts);			\
+		__v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
+		__start += ts;						\
+	}								\
+	if (end % ts) {							\
+		mask = ~((~(type) 0) << (end % ts));			\
+		cmask = __ptr[this_unit];				\
+		cmask >>= ts - (end % ts);				\
+		cmask &= mask;						\
+		__v = _bt_piecewise_lshift(__v, end % ts);		\
+		__v |= _bt_unsigned_cast(typeof(__v), cmask);		\
+	} else {							\
+		__v = _bt_piecewise_lshift(__v, ts);			\
+		__v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
+	}								\
+	*__vptr = __v;							\
+} while (0)
+
+/*
+ * bt_bitfield_read - read integer from a bitfield in native endianness
+ * bt_bitfield_read_le - read integer from a bitfield in little endian
+ * bt_bitfield_read_be - read integer from a bitfield in big endian
+ */
+
+#if (__BYTE_ORDER == __LITTLE_ENDIAN)
+
+#define bt_bitfield_read(_ptr, type, _start, _length, _vptr)		\
+	_bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)
+
+#define bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)		\
+	_bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)
+	
+#define bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)		\
+	_bt_bitfield_read_be(_ptr, unsigned char, _start, _length, _vptr)
+
+#elif (__BYTE_ORDER == __BIG_ENDIAN)
+
+#define bt_bitfield_read(_ptr, type, _start, _length, _vptr)		\
+	_bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)
+
+#define bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)		\
+	_bt_bitfield_read_le(_ptr, unsigned char, _start, _length, _vptr)
+	
+#define bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)		\
+	_bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)
+
+#else /* (__BYTE_ORDER == __PDP_ENDIAN) */
+
+#error "Byte order not supported"
+
+#endif
+
+#endif /* _BABELTRACE_BITFIELD_H */