#define _BABELTRACE_BITFIELD_H
/*
- * BabelTrace
- *
- * Bitfields read/write functions.
- *
- * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright 2010-2019 - 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
#include <limits.h> /* C99 5.2.4.2 Numerical limits */
#include <lttng/ust-endian.h> /* Non-standard BIG_ENDIAN, LITTLE_ENDIAN, BYTE_ORDER */
-/* 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; \
-})
+/*
+ * This header strictly follows the C99 standard, except for use of the
+ * compiler-specific __typeof__.
+ */
+
+/*
+ * This bitfield header requires the compiler representation of signed
+ * integers to be two's complement.
+ */
+#if (-1 != ~0)
+#error "bitfield.h requires the compiler representation of signed integers to be two's complement."
+#endif
#define _bt_is_signed_type(type) ((type) -1 < (type) 0)
-#define _bt_unsigned_cast(type, v) \
-({ \
- (sizeof(v) < sizeof(type)) ? \
- ((type) (v)) & (~(~(type) 0 << (sizeof(v) * CHAR_BIT))) : \
- (type) (v); \
-})
+/*
+ * Produce a build-time error if the condition `cond` is non-zero.
+ * Evaluates as a size_t expression.
+ */
+#define _BT_BUILD_ASSERT(cond) \
+ sizeof(struct { int f:(2 * !!(cond) - 1); })
+
+/*
+ * Cast value `v` to an unsigned integer of the same size as `v`.
+ */
+#define _bt_cast_value_to_unsigned(v) \
+ (sizeof(v) == sizeof(uint8_t) ? (uint8_t) (v) : \
+ sizeof(v) == sizeof(uint16_t) ? (uint16_t) (v) : \
+ sizeof(v) == sizeof(uint32_t) ? (uint32_t) (v) : \
+ sizeof(v) == sizeof(uint64_t) ? (uint64_t) (v) : \
+ _BT_BUILD_ASSERT(sizeof(v) <= sizeof(uint64_t)))
+
+/*
+ * Cast value `v` to an unsigned integer type of the size of type `type`
+ * *without* sign-extension.
+ *
+ * The unsigned cast ensures that we're not shifting a negative value,
+ * which is undefined in C. However, this limits the maximum type size
+ * of `type` to 64-bit. Generate a compile-time error if the size of
+ * `type` is larger than 64-bit.
+ */
+#define _bt_cast_value_to_unsigned_type(type, v) \
+ (sizeof(type) == sizeof(uint8_t) ? \
+ (uint8_t) _bt_cast_value_to_unsigned(v) : \
+ sizeof(type) == sizeof(uint16_t) ? \
+ (uint16_t) _bt_cast_value_to_unsigned(v) : \
+ sizeof(type) == sizeof(uint32_t) ? \
+ (uint32_t) _bt_cast_value_to_unsigned(v) : \
+ sizeof(type) == sizeof(uint64_t) ? \
+ (uint64_t) _bt_cast_value_to_unsigned(v) : \
+ _BT_BUILD_ASSERT(sizeof(v) <= sizeof(uint64_t)))
+
+/*
+ * _bt_fill_mask evaluates to a "type" integer with all bits set.
+ */
+#define _bt_fill_mask(type) ((type) ~(type) 0)
+
+/*
+ * Left shift a value `v` of `shift` bits.
+ *
+ * The type of `v` can be signed or unsigned integer.
+ * The value of `shift` must be less than the size of `v` (in bits),
+ * otherwise the behavior is undefined.
+ * Evaluates to the result of the shift operation.
+ *
+ * According to the C99 standard, left shift of a left hand-side signed
+ * type is undefined if it has a negative value or if the result cannot
+ * be represented in the result type. This bitfield header discards the
+ * bits that are left-shifted beyond the result type representation,
+ * which is the behavior of an unsigned type left shift operation.
+ * Therefore, always perform left shift on an unsigned type.
+ *
+ * This macro should not be used if `shift` can be greater or equal than
+ * the bitwidth of `v`. See `_bt_safe_lshift`.
+ */
+#define _bt_lshift(v, shift) \
+ ((__typeof__(v)) (_bt_cast_value_to_unsigned(v) << (shift)))
+
+/*
+ * Generate a mask of type `type` with the `length` least significant bits
+ * cleared, and the most significant bits set.
+ */
+#define _bt_make_mask_complement(type, length) \
+ _bt_lshift(_bt_fill_mask(type), length)
+
+/*
+ * Generate a mask of type `type` with the `length` least significant bits
+ * set, and the most significant bits cleared.
+ */
+#define _bt_make_mask(type, length) \
+ ((type) ~_bt_make_mask_complement(type, length))
+
+/*
+ * Right shift a value `v` of `shift` bits.
+ *
+ * The type of `v` can be signed or unsigned integer.
+ * The value of `shift` must be less than the size of `v` (in bits),
+ * otherwise the behavior is undefined.
+ * Evaluates to the result of the shift operation.
+ *
+ * According to the C99 standard, right shift of a left hand-side signed
+ * type which has a negative value is implementation defined. This
+ * bitfield header relies on the right shift implementation carrying the
+ * sign bit. If the compiler implementation has a different behavior,
+ * emulate carrying the sign bit.
+ *
+ * This macro should not be used if `shift` can be greater or equal than
+ * the bitwidth of `v`. See `_bt_safe_rshift`.
+ */
+#if ((-1 >> 1) == -1)
+#define _bt_rshift(v, shift) ((v) >> (shift))
+#else
+#define _bt_rshift(v, shift) \
+ ((__typeof__(v)) ((_bt_cast_value_to_unsigned(v) >> (shift)) | \
+ ((v) < 0 ? _bt_make_mask_complement(__typeof__(v), \
+ sizeof(v) * CHAR_BIT - (shift)) : 0)))
+#endif
+
+/*
+ * Right shift a signed or unsigned integer with `shift` value being an
+ * arbitrary number of bits. `v` is modified by this macro. The shift
+ * is transformed into a sequence of `_nr_partial_shifts` consecutive
+ * shift operations, each of a number of bits smaller than the bitwidth
+ * of `v`, ending with a shift of the number of left over bits.
+ */
+#define _bt_safe_rshift(v, shift) \
+do { \
+ unsigned long _nr_partial_shifts = (shift) / (sizeof(v) * CHAR_BIT - 1); \
+ unsigned long _leftover_bits = (shift) % (sizeof(v) * CHAR_BIT - 1); \
+ \
+ for (; _nr_partial_shifts; _nr_partial_shifts--) \
+ (v) = _bt_rshift(v, sizeof(v) * CHAR_BIT - 1); \
+ (v) = _bt_rshift(v, _leftover_bits); \
+} while (0)
+
+/*
+ * Left shift a signed or unsigned integer with `shift` value being an
+ * arbitrary number of bits. `v` is modified by this macro. The shift
+ * is transformed into a sequence of `_nr_partial_shifts` consecutive
+ * shift operations, each of a number of bits smaller than the bitwidth
+ * of `v`, ending with a shift of the number of left over bits.
+ */
+#define _bt_safe_lshift(v, shift) \
+do { \
+ unsigned long _nr_partial_shifts = (shift) / (sizeof(v) * CHAR_BIT - 1); \
+ unsigned long _leftover_bits = (shift) % (sizeof(v) * CHAR_BIT - 1); \
+ \
+ for (; _nr_partial_shifts; _nr_partial_shifts--) \
+ (v) = _bt_lshift(v, sizeof(v) * CHAR_BIT - 1); \
+ (v) = _bt_lshift(v, _leftover_bits); \
+} while (0)
/*
* bt_bitfield_write - write integer to a bitfield in native endianness
#define _bt_bitfield_write_le(_ptr, type, _start, _length, _v) \
do { \
- __typeof__(_v) __v = (_v); \
+ __typeof__(_v) __v = (_v); \
type *__ptr = (void *) (_ptr); \
unsigned long __start = (_start), __length = (_length); \
type mask, cmask; \
\
/* Trim v high bits */ \
if (__length < sizeof(__v) * CHAR_BIT) \
- __v &= ~((~(__typeof__(__v)) 0) << __length); \
+ __v &= _bt_make_mask(__typeof__(__v), __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)); \
+ mask = _bt_make_mask(type, __start % ts); \
if (end % ts) \
- mask |= (~(type) 0) << (end % ts); \
- cmask = (type) __v << (__start % ts); \
+ mask |= _bt_make_mask_complement(type, end % ts); \
+ cmask = _bt_lshift((type) (__v), __start % ts); \
cmask &= ~mask; \
__ptr[this_unit] &= mask; \
__ptr[this_unit] |= cmask; \
} \
if (__start % ts) { \
cshift = __start % ts; \
- mask = ~((~(type) 0) << cshift); \
- cmask = (type) __v << cshift; \
+ mask = _bt_make_mask(type, cshift); \
+ cmask = _bt_lshift((type) (__v), cshift); \
cmask &= ~mask; \
__ptr[this_unit] &= mask; \
__ptr[this_unit] |= cmask; \
- __v = _bt_piecewise_rshift(__v, ts - cshift); \
+ _bt_safe_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); \
+ _bt_safe_rshift(__v, ts); \
__start += ts; \
} \
if (end % ts) { \
- mask = (~(type) 0) << (end % ts); \
+ mask = _bt_make_mask_complement(type, end % ts); \
cmask = (type) __v; \
cmask &= ~mask; \
__ptr[this_unit] &= mask; \
#define _bt_bitfield_write_be(_ptr, type, _start, _length, _v) \
do { \
- __typeof__(_v) __v = (_v); \
+ __typeof__(_v) __v = (_v); \
type *__ptr = (void *) (_ptr); \
unsigned long __start = (_start), __length = (_length); \
type mask, cmask; \
\
/* Trim v high bits */ \
if (__length < sizeof(__v) * CHAR_BIT) \
- __v &= ~((~(__typeof__(__v)) 0) << __length); \
+ __v &= _bt_make_mask(__typeof__(__v), __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)); \
+ mask = _bt_make_mask(type, (ts - (end % ts)) % ts); \
if (__start % ts) \
- mask |= (~((type) 0)) << (ts - (__start % ts)); \
- cmask = (type) __v << ((ts - (end % ts)) % ts); \
+ mask |= _bt_make_mask_complement(type, ts - (__start % ts)); \
+ cmask = _bt_lshift((type) (__v), (ts - (end % ts)) % ts); \
cmask &= ~mask; \
__ptr[this_unit] &= mask; \
__ptr[this_unit] |= cmask; \
} \
if (end % ts) { \
cshift = end % ts; \
- mask = ~((~(type) 0) << (ts - cshift)); \
- cmask = (type) __v << (ts - cshift); \
+ mask = _bt_make_mask(type, ts - cshift); \
+ cmask = _bt_lshift((type) (__v), ts - cshift); \
cmask &= ~mask; \
__ptr[this_unit] &= mask; \
__ptr[this_unit] |= cmask; \
- __v = _bt_piecewise_rshift(__v, cshift); \
+ _bt_safe_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); \
+ _bt_safe_rshift(__v, ts); \
end -= ts; \
} \
if (__start % ts) { \
- mask = (~(type) 0) << (ts - (__start % ts)); \
+ mask = _bt_make_mask_complement(type, ts - (__start % ts)); \
cmask = (type) __v; \
cmask &= ~mask; \
__ptr[this_unit] &= mask; \
#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)
#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)
#define _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr) \
do { \
__typeof__(*(_vptr)) *__vptr = (_vptr); \
- __typeof__(*__vptr) __v; \
+ __typeof__(*__vptr) __v; \
type *__ptr = (void *) (_ptr); \
unsigned long __start = (_start), __length = (_length); \
type mask, cmask; \
\
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; \
+ && (__ptr[this_unit] & _bt_lshift((type) 1, (end % ts ? end % ts : ts) - 1))) \
+ __v = ~(__typeof__(__v)) 0; \
else \
__v = 0; \
if (start_unit == end_unit - 1) { \
cmask = __ptr[this_unit]; \
- cmask >>= (__start % ts); \
+ cmask = _bt_rshift(cmask, __start % ts); \
if ((end - __start) % ts) { \
- mask = ~((~(type) 0) << (end - __start)); \
+ mask = _bt_make_mask(type, end - __start); \
cmask &= mask; \
} \
- __v = _bt_piecewise_lshift(__v, end - __start); \
- __v |= _bt_unsigned_cast(__typeof__(__v), cmask); \
+ _bt_safe_lshift(__v, end - __start); \
+ __v |= _bt_cast_value_to_unsigned_type(__typeof__(__v), cmask); \
*__vptr = __v; \
break; \
} \
if (end % ts) { \
cshift = end % ts; \
- mask = ~((~(type) 0) << cshift); \
+ mask = _bt_make_mask(type, cshift); \
cmask = __ptr[this_unit]; \
cmask &= mask; \
- __v = _bt_piecewise_lshift(__v, cshift); \
- __v |= _bt_unsigned_cast(__typeof__(__v), cmask); \
+ _bt_safe_lshift(__v, cshift); \
+ __v |= _bt_cast_value_to_unsigned_type(__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]);\
+ _bt_safe_lshift(__v, ts); \
+ __v |= _bt_cast_value_to_unsigned_type(__typeof__(__v), __ptr[this_unit]); \
end -= ts; \
} \
if (__start % ts) { \
- mask = ~((~(type) 0) << (ts - (__start % ts))); \
+ mask = _bt_make_mask(type, ts - (__start % ts)); \
cmask = __ptr[this_unit]; \
- cmask >>= (__start % ts); \
+ cmask = _bt_rshift(cmask, __start % ts); \
cmask &= mask; \
- __v = _bt_piecewise_lshift(__v, ts - (__start % ts)); \
- __v |= _bt_unsigned_cast(__typeof__(__v), cmask); \
+ _bt_safe_lshift(__v, ts - (__start % ts)); \
+ __v |= _bt_cast_value_to_unsigned_type(__typeof__(__v), cmask); \
} else { \
- __v = _bt_piecewise_lshift(__v, ts); \
- __v |= _bt_unsigned_cast(__typeof__(__v), __ptr[this_unit]);\
+ _bt_safe_lshift(__v, ts); \
+ __v |= _bt_cast_value_to_unsigned_type(__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; \
+ __typeof__(*__vptr) __v; \
type *__ptr = (void *) (_ptr); \
unsigned long __start = (_start), __length = (_length); \
type mask, cmask; \
\
this_unit = start_unit; \
if (_bt_is_signed_type(__typeof__(__v)) \
- && (__ptr[this_unit] & ((type) 1 << (ts - (__start % ts) - 1)))) \
- __v = ~(__typeof__(__v)) 0; \
+ && (__ptr[this_unit] & _bt_lshift((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; \
+ cmask = _bt_rshift(cmask, (ts - (end % ts)) % ts); \
if ((end - __start) % ts) { \
- mask = ~((~(type) 0) << (end - __start)); \
+ mask = _bt_make_mask(type, end - __start); \
cmask &= mask; \
} \
- __v = _bt_piecewise_lshift(__v, end - __start); \
- __v |= _bt_unsigned_cast(__typeof__(__v), cmask); \
+ _bt_safe_lshift(__v, end - __start); \
+ __v |= _bt_cast_value_to_unsigned_type(__typeof__(__v), cmask); \
*__vptr = __v; \
break; \
} \
if (__start % ts) { \
cshift = __start % ts; \
- mask = ~((~(type) 0) << (ts - cshift)); \
+ mask = _bt_make_mask(type, ts - cshift); \
cmask = __ptr[this_unit]; \
cmask &= mask; \
- __v = _bt_piecewise_lshift(__v, ts - cshift); \
- __v |= _bt_unsigned_cast(__typeof__(__v), cmask); \
+ _bt_safe_lshift(__v, ts - cshift); \
+ __v |= _bt_cast_value_to_unsigned_type(__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]);\
+ _bt_safe_lshift(__v, ts); \
+ __v |= _bt_cast_value_to_unsigned_type(__typeof__(__v), __ptr[this_unit]); \
__start += ts; \
} \
if (end % ts) { \
- mask = ~((~(type) 0) << (end % ts)); \
+ mask = _bt_make_mask(type, end % ts); \
cmask = __ptr[this_unit]; \
- cmask >>= ts - (end % ts); \
+ cmask = _bt_rshift(cmask, ts - (end % ts)); \
cmask &= mask; \
- __v = _bt_piecewise_lshift(__v, end % ts); \
- __v |= _bt_unsigned_cast(__typeof__(__v), cmask); \
+ _bt_safe_lshift(__v, end % ts); \
+ __v |= _bt_cast_value_to_unsigned_type(__typeof__(__v), cmask); \
} else { \
- __v = _bt_piecewise_lshift(__v, ts); \
- __v |= _bt_unsigned_cast(__typeof__(__v), __ptr[this_unit]);\
+ _bt_safe_lshift(__v, ts); \
+ __v |= _bt_cast_value_to_unsigned_type(__typeof__(__v), __ptr[this_unit]); \
} \
*__vptr = __v; \
} while (0)
#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)
#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)
projects / lttng-ust.git / commitdiff
