diff options
Diffstat (limited to 'util/host-utils.c')
-rw-r--r-- | util/host-utils.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/util/host-utils.c b/util/host-utils.c index f0784d6..37c1706 100644 --- a/util/host-utils.c +++ b/util/host-utils.c @@ -86,4 +86,42 @@ void muls64 (uint64_t *plow, uint64_t *phigh, int64_t a, int64_t b) } *phigh = rh; } + +/* Unsigned 128x64 division. Returns 1 if overflow (divide by zero or */ +/* quotient exceeds 64 bits). Otherwise returns quotient via plow and */ +/* remainder via phigh. */ +int divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor) +{ + uint64_t dhi = *phigh; + uint64_t dlo = *plow; + unsigned i; + uint64_t carry = 0; + + if (divisor == 0) { + return 1; + } else if (dhi == 0) { + *plow = dlo / divisor; + *phigh = dlo % divisor; + return 0; + } else if (dhi > divisor) { + return 1; + } else { + + for (i = 0; i < 64; i++) { + carry = dhi >> 63; + dhi = (dhi << 1) | (dlo >> 63); + if (carry || (dhi >= divisor)) { + dhi -= divisor; + carry = 1; + } else { + carry = 0; + } + dlo = (dlo << 1) | carry; + } + + *plow = dlo; + *phigh = dhi; + return 0; + } +} #endif /* !CONFIG_INT128 */ |