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Diffstat (limited to 'fluent-bit/lib/jemalloc-5.3.0/include/jemalloc/internal/fxp.h')
-rw-r--r-- | fluent-bit/lib/jemalloc-5.3.0/include/jemalloc/internal/fxp.h | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/fluent-bit/lib/jemalloc-5.3.0/include/jemalloc/internal/fxp.h b/fluent-bit/lib/jemalloc-5.3.0/include/jemalloc/internal/fxp.h new file mode 100644 index 00000000..415a9828 --- /dev/null +++ b/fluent-bit/lib/jemalloc-5.3.0/include/jemalloc/internal/fxp.h @@ -0,0 +1,126 @@ +#ifndef JEMALLOC_INTERNAL_FXP_H +#define JEMALLOC_INTERNAL_FXP_H + +/* + * A simple fixed-point math implementation, supporting only unsigned values + * (with overflow being an error). + * + * It's not in general safe to use floating point in core code, because various + * libc implementations we get linked against can assume that malloc won't touch + * floating point state and call it with an unusual calling convention. + */ + +/* + * High 16 bits are the integer part, low 16 are the fractional part. Or + * equivalently, repr == 2**16 * val, where we use "val" to refer to the + * (imaginary) fractional representation of the true value. + * + * We pick a uint32_t here since it's convenient in some places to + * double the representation size (i.e. multiplication and division use + * 64-bit integer types), and a uint64_t is the largest type we're + * certain is available. + */ +typedef uint32_t fxp_t; +#define FXP_INIT_INT(x) ((x) << 16) +#define FXP_INIT_PERCENT(pct) (((pct) << 16) / 100) + +/* + * Amount of precision used in parsing and printing numbers. The integer bound + * is simply because the integer part of the number gets 16 bits, and so is + * bounded by 65536. + * + * We use a lot of precision for the fractional part, even though most of it + * gets rounded off; this lets us get exact values for the important special + * case where the denominator is a small power of 2 (for instance, + * 1/512 == 0.001953125 is exactly representable even with only 16 bits of + * fractional precision). We need to left-shift by 16 before dividing by + * 10**precision, so we pick precision to be floor(log(2**48)) = 14. + */ +#define FXP_INTEGER_PART_DIGITS 5 +#define FXP_FRACTIONAL_PART_DIGITS 14 + +/* + * In addition to the integer and fractional parts of the number, we need to + * include a null character and (possibly) a decimal point. + */ +#define FXP_BUF_SIZE (FXP_INTEGER_PART_DIGITS + FXP_FRACTIONAL_PART_DIGITS + 2) + +static inline fxp_t +fxp_add(fxp_t a, fxp_t b) { + return a + b; +} + +static inline fxp_t +fxp_sub(fxp_t a, fxp_t b) { + assert(a >= b); + return a - b; +} + +static inline fxp_t +fxp_mul(fxp_t a, fxp_t b) { + uint64_t unshifted = (uint64_t)a * (uint64_t)b; + /* + * Unshifted is (a.val * 2**16) * (b.val * 2**16) + * == (a.val * b.val) * 2**32, but we want + * (a.val * b.val) * 2 ** 16. + */ + return (uint32_t)(unshifted >> 16); +} + +static inline fxp_t +fxp_div(fxp_t a, fxp_t b) { + assert(b != 0); + uint64_t unshifted = ((uint64_t)a << 32) / (uint64_t)b; + /* + * Unshifted is (a.val * 2**16) * (2**32) / (b.val * 2**16) + * == (a.val / b.val) * (2 ** 32), which again corresponds to a right + * shift of 16. + */ + return (uint32_t)(unshifted >> 16); +} + +static inline uint32_t +fxp_round_down(fxp_t a) { + return a >> 16; +} + +static inline uint32_t +fxp_round_nearest(fxp_t a) { + uint32_t fractional_part = (a & ((1U << 16) - 1)); + uint32_t increment = (uint32_t)(fractional_part >= (1U << 15)); + return (a >> 16) + increment; +} + +/* + * Approximately computes x * frac, without the size limitations that would be + * imposed by converting u to an fxp_t. + */ +static inline size_t +fxp_mul_frac(size_t x_orig, fxp_t frac) { + assert(frac <= (1U << 16)); + /* + * Work around an over-enthusiastic warning about type limits below (on + * 32-bit platforms, a size_t is always less than 1ULL << 48). + */ + uint64_t x = (uint64_t)x_orig; + /* + * If we can guarantee no overflow, multiply first before shifting, to + * preserve some precision. Otherwise, shift first and then multiply. + * In the latter case, we only lose the low 16 bits of a 48-bit number, + * so we're still accurate to within 1/2**32. + */ + if (x < (1ULL << 48)) { + return (size_t)((x * frac) >> 16); + } else { + return (size_t)((x >> 16) * (uint64_t)frac); + } +} + +/* + * Returns true on error. Otherwise, returns false and updates *ptr to point to + * the first character not parsed (because it wasn't a digit). + */ +bool fxp_parse(fxp_t *a, const char *ptr, char **end); +void fxp_print(fxp_t a, char buf[FXP_BUF_SIZE]); + +#endif /* JEMALLOC_INTERNAL_FXP_H */ |