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Diffstat (limited to 'subprojects/exess/src/int_math.c')
-rw-r--r-- | subprojects/exess/src/int_math.c | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/subprojects/exess/src/int_math.c b/subprojects/exess/src/int_math.c new file mode 100644 index 00000000..ce263b43 --- /dev/null +++ b/subprojects/exess/src/int_math.c @@ -0,0 +1,78 @@ +/* + Copyright 2019-2021 David Robillard <d@drobilla.net> + + Permission to use, copy, modify, and/or distribute this software for any + purpose with or without fee is hereby granted, provided that the above + copyright notice and this permission notice appear in all copies. + + THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. +*/ + +#include "int_math.h" + +#include "exess_config.h" + +#include <assert.h> + +unsigned +exess_clz32(const uint32_t i) +{ + assert(i != 0); + +#if USE_BUILTIN_CLZ + return (unsigned)__builtin_clz(i); +#else + unsigned n = 32u; + uint32_t bits = i; + for (unsigned s = 16; s > 0; s >>= 1) { + const uint32_t left = bits >> s; + if (left) { + n -= s; + bits = left; + } + } + return n - bits; +#endif +} + +unsigned +exess_clz64(const uint64_t i) +{ + assert(i != 0); + +#if USE_BUILTIN_CLZLL + return (unsigned)__builtin_clzll(i); +#else + return i & 0xFFFFFFFF00000000 ? exess_clz32((uint32_t)(i >> 32u)) + : 32u + exess_clz32(i & 0xFFFFFFFF); +#endif +} + +uint64_t +exess_ilog2(const uint64_t i) +{ + assert(i != 0); + return (64u - exess_clz64(i | 1u)) - 1u; +} + +uint64_t +exess_ilog10(const uint64_t i) +{ + // See https://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10 + const uint64_t log2 = exess_ilog2(i); + const uint64_t t = (log2 + 1u) * 1233u >> 12u; + + return t - (i < POW10[t]) + (i == 0); +} + +uint8_t +exess_num_digits(const uint64_t i) +{ + return i == 0u ? 1u : (uint8_t)(exess_ilog10(i) + 1u); +} |