diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h index 550107f8..2a64d342 100644 --- a/include/fmt/format-inl.h +++ b/include/fmt/format-inl.h @@ -460,7 +460,10 @@ int grisu2_gen_digits(char* buf, fp value, uint64_t error_ulp, int& exp, uint64_t fractional = value.f & (one.f - 1); exp = count_digits(integral); // kappa in Grisu. int size = 0; - if (stop.on_exp(exp)) return size; + if (stop.init(buf, size, value.f, data::POWERS_OF_10_64[exp] << -one.e, + error_ulp, exp)) { + return size; + } // Generate digits for the integral part. This can produce up to 10 digits. do { uint32_t digit = 0; @@ -541,17 +544,44 @@ struct fixed_stop { return full_exp <= 0 && -full_exp >= precision; } - bool on_exp(int exp) { + enum round_direction { unknown, up, down }; + + static round_direction round(uint64_t remainder, uint64_t divisor, + uint64_t error) { + assert(error < divisor && error < divisor - error); + // Round down if (remainder + error) * 2 <= divisor. + if (remainder < divisor - remainder && error * 2 <= divisor - remainder * 2) + return down; + // Round up if (remainder - error) * 2 >= divisor. + if (remainder >= error && + remainder - error >= divisor - (remainder - error)) { + return up; + } + return unknown; + } + + bool init(char* buf, int& size, uint64_t remainder, uint64_t divisor, + uint64_t error, int& exp) { if (!fixed) return false; - exp += exp10; - if (exp >= 0) precision += exp; - // TODO: round - return enough_precision(exp); + int full_exp = exp + exp10; + if (full_exp >= 0) precision += full_exp; + if (!enough_precision(full_exp)) return false; + switch (round(remainder, divisor, error)) { + case unknown: + size = -1; + break; + case up: + buf[size++] = '1'; + break; + case down: + break; + } + return true; } // TODO: test bool operator()(char* buf, int& size, uint64_t remainder, uint64_t divisor, - uint64_t error, int& exp, bool integral) { + uint64_t error, int& exp, bool integral) const { assert(remainder < divisor); if (size != precision && !enough_precision(exp + exp10)) return false; if (!integral) { @@ -565,12 +595,11 @@ struct fixed_stop { } else { assert(error == 1 && divisor > 2); } - // Round down if (remainder + error) * 2 <= divisor. - if (remainder < divisor - remainder && error * 2 <= divisor - remainder * 2) - return true; - // Round up if (remainder - error) * 2 >= divisor. - if (remainder >= error && - remainder - error >= divisor - (remainder - error)) { + switch (round(remainder, divisor, error)) { + case unknown: + size = -1; + break; + case up: ++buf[size - 1]; for (int i = size - 1; i > 0 && buf[i] > '9'; --i) { buf[i] = '0'; @@ -580,9 +609,10 @@ struct fixed_stop { buf[0] = '1'; ++exp; } - return true; + break; + case down: + break; } - size = -1; return true; } }; @@ -591,7 +621,7 @@ struct fixed_stop { struct shortest_stop { fp diff; // wp_w in Grisu. - bool on_exp(int) { return false; } + bool init(char*, int&, uint64_t, uint64_t, uint64_t, int&) { return false; } bool operator()(char* buf, int& size, uint64_t remainder, uint64_t divisor, uint64_t error, int& exp, bool integral) { diff --git a/test/format-test.cc b/test/format-test.cc index ac6d7628..466a07ce 100644 --- a/test/format-test.cc +++ b/test/format-test.cc @@ -1472,6 +1472,7 @@ TEST(FormatterTest, FormatDouble) { TEST(FormatterTest, PrecisionRounding) { EXPECT_EQ("0.000", format("{:.3f}", 0.00049)); + EXPECT_EQ("0.001", format("{:.3f}", 0.0005)); } TEST(FormatterTest, FormatNaN) {