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+/*---------------------------------------------------------------------------
+ *
+ * Ryu floating-point output for single precision.
+ *
+ * Portions Copyright (c) 2018-2023, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * src/common/f2s.c
+ *
+ * This is a modification of code taken from github.com/ulfjack/ryu under the
+ * terms of the Boost license (not the Apache license). The original copyright
+ * notice follows:
+ *
+ * Copyright 2018 Ulf Adams
+ *
+ * The contents of this file may be used under the terms of the Apache
+ * License, Version 2.0.
+ *
+ * (See accompanying file LICENSE-Apache or copy at
+ * http://www.apache.org/licenses/LICENSE-2.0)
+ *
+ * Alternatively, the contents of this file may be used under the terms of the
+ * Boost Software License, Version 1.0.
+ *
+ * (See accompanying file LICENSE-Boost or copy at
+ * https://www.boost.org/LICENSE_1_0.txt)
+ *
+ * Unless required by applicable law or agreed to in writing, this software is
+ * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.
+ *
+ *---------------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#endif
+
+#include "common/shortest_dec.h"
+#include "digit_table.h"
+#include "ryu_common.h"
+
+#define FLOAT_MANTISSA_BITS 23
+#define FLOAT_EXPONENT_BITS 8
+#define FLOAT_BIAS 127
+
+/*
+ * This table is generated (by the upstream) by PrintFloatLookupTable,
+ * and modified (by us) to add UINT64CONST.
+ */
+#define FLOAT_POW5_INV_BITCOUNT 59
+static const uint64 FLOAT_POW5_INV_SPLIT[31] = {
+ UINT64CONST(576460752303423489), UINT64CONST(461168601842738791), UINT64CONST(368934881474191033), UINT64CONST(295147905179352826),
+ UINT64CONST(472236648286964522), UINT64CONST(377789318629571618), UINT64CONST(302231454903657294), UINT64CONST(483570327845851670),
+ UINT64CONST(386856262276681336), UINT64CONST(309485009821345069), UINT64CONST(495176015714152110), UINT64CONST(396140812571321688),
+ UINT64CONST(316912650057057351), UINT64CONST(507060240091291761), UINT64CONST(405648192073033409), UINT64CONST(324518553658426727),
+ UINT64CONST(519229685853482763), UINT64CONST(415383748682786211), UINT64CONST(332306998946228969), UINT64CONST(531691198313966350),
+ UINT64CONST(425352958651173080), UINT64CONST(340282366920938464), UINT64CONST(544451787073501542), UINT64CONST(435561429658801234),
+ UINT64CONST(348449143727040987), UINT64CONST(557518629963265579), UINT64CONST(446014903970612463), UINT64CONST(356811923176489971),
+ UINT64CONST(570899077082383953), UINT64CONST(456719261665907162), UINT64CONST(365375409332725730)
+};
+#define FLOAT_POW5_BITCOUNT 61
+static const uint64 FLOAT_POW5_SPLIT[47] = {
+ UINT64CONST(1152921504606846976), UINT64CONST(1441151880758558720), UINT64CONST(1801439850948198400), UINT64CONST(2251799813685248000),
+ UINT64CONST(1407374883553280000), UINT64CONST(1759218604441600000), UINT64CONST(2199023255552000000), UINT64CONST(1374389534720000000),
+ UINT64CONST(1717986918400000000), UINT64CONST(2147483648000000000), UINT64CONST(1342177280000000000), UINT64CONST(1677721600000000000),
+ UINT64CONST(2097152000000000000), UINT64CONST(1310720000000000000), UINT64CONST(1638400000000000000), UINT64CONST(2048000000000000000),
+ UINT64CONST(1280000000000000000), UINT64CONST(1600000000000000000), UINT64CONST(2000000000000000000), UINT64CONST(1250000000000000000),
+ UINT64CONST(1562500000000000000), UINT64CONST(1953125000000000000), UINT64CONST(1220703125000000000), UINT64CONST(1525878906250000000),
+ UINT64CONST(1907348632812500000), UINT64CONST(1192092895507812500), UINT64CONST(1490116119384765625), UINT64CONST(1862645149230957031),
+ UINT64CONST(1164153218269348144), UINT64CONST(1455191522836685180), UINT64CONST(1818989403545856475), UINT64CONST(2273736754432320594),
+ UINT64CONST(1421085471520200371), UINT64CONST(1776356839400250464), UINT64CONST(2220446049250313080), UINT64CONST(1387778780781445675),
+ UINT64CONST(1734723475976807094), UINT64CONST(2168404344971008868), UINT64CONST(1355252715606880542), UINT64CONST(1694065894508600678),
+ UINT64CONST(2117582368135750847), UINT64CONST(1323488980084844279), UINT64CONST(1654361225106055349), UINT64CONST(2067951531382569187),
+ UINT64CONST(1292469707114105741), UINT64CONST(1615587133892632177), UINT64CONST(2019483917365790221)
+};
+
+static inline uint32
+pow5Factor(uint32 value)
+{
+ uint32 count = 0;
+
+ for (;;)
+ {
+ Assert(value != 0);
+ const uint32 q = value / 5;
+ const uint32 r = value % 5;
+
+ if (r != 0)
+ break;
+
+ value = q;
+ ++count;
+ }
+ return count;
+}
+
+/* Returns true if value is divisible by 5^p. */
+static inline bool
+multipleOfPowerOf5(const uint32 value, const uint32 p)
+{
+ return pow5Factor(value) >= p;
+}
+
+/* Returns true if value is divisible by 2^p. */
+static inline bool
+multipleOfPowerOf2(const uint32 value, const uint32 p)
+{
+ /* return __builtin_ctz(value) >= p; */
+ return (value & ((1u << p) - 1)) == 0;
+}
+
+/*
+ * It seems to be slightly faster to avoid uint128_t here, although the
+ * generated code for uint128_t looks slightly nicer.
+ */
+static inline uint32
+mulShift(const uint32 m, const uint64 factor, const int32 shift)
+{
+ /*
+ * The casts here help MSVC to avoid calls to the __allmul library
+ * function.
+ */
+ const uint32 factorLo = (uint32) (factor);
+ const uint32 factorHi = (uint32) (factor >> 32);
+ const uint64 bits0 = (uint64) m * factorLo;
+ const uint64 bits1 = (uint64) m * factorHi;
+
+ Assert(shift > 32);
+
+#ifdef RYU_32_BIT_PLATFORM
+
+ /*
+ * On 32-bit platforms we can avoid a 64-bit shift-right since we only
+ * need the upper 32 bits of the result and the shift value is > 32.
+ */
+ const uint32 bits0Hi = (uint32) (bits0 >> 32);
+ uint32 bits1Lo = (uint32) (bits1);
+ uint32 bits1Hi = (uint32) (bits1 >> 32);
+
+ bits1Lo += bits0Hi;
+ bits1Hi += (bits1Lo < bits0Hi);
+
+ const int32 s = shift - 32;
+
+ return (bits1Hi << (32 - s)) | (bits1Lo >> s);
+
+#else /* RYU_32_BIT_PLATFORM */
+
+ const uint64 sum = (bits0 >> 32) + bits1;
+ const uint64 shiftedSum = sum >> (shift - 32);
+
+ Assert(shiftedSum <= PG_UINT32_MAX);
+ return (uint32) shiftedSum;
+
+#endif /* RYU_32_BIT_PLATFORM */
+}
+
+static inline uint32
+mulPow5InvDivPow2(const uint32 m, const uint32 q, const int32 j)
+{
+ return mulShift(m, FLOAT_POW5_INV_SPLIT[q], j);
+}
+
+static inline uint32
+mulPow5divPow2(const uint32 m, const uint32 i, const int32 j)
+{
+ return mulShift(m, FLOAT_POW5_SPLIT[i], j);
+}
+
+static inline uint32
+decimalLength(const uint32 v)
+{
+ /* Function precondition: v is not a 10-digit number. */
+ /* (9 digits are sufficient for round-tripping.) */
+ Assert(v < 1000000000);
+ if (v >= 100000000)
+ {
+ return 9;
+ }
+ if (v >= 10000000)
+ {
+ return 8;
+ }
+ if (v >= 1000000)
+ {
+ return 7;
+ }
+ if (v >= 100000)
+ {
+ return 6;
+ }
+ if (v >= 10000)
+ {
+ return 5;
+ }
+ if (v >= 1000)
+ {
+ return 4;
+ }
+ if (v >= 100)
+ {
+ return 3;
+ }
+ if (v >= 10)
+ {
+ return 2;
+ }
+ return 1;
+}
+
+/* A floating decimal representing m * 10^e. */
+typedef struct floating_decimal_32
+{
+ uint32 mantissa;
+ int32 exponent;
+} floating_decimal_32;
+
+static inline floating_decimal_32
+f2d(const uint32 ieeeMantissa, const uint32 ieeeExponent)
+{
+ int32 e2;
+ uint32 m2;
+
+ if (ieeeExponent == 0)
+ {
+ /* We subtract 2 so that the bounds computation has 2 additional bits. */
+ e2 = 1 - FLOAT_BIAS - FLOAT_MANTISSA_BITS - 2;
+ m2 = ieeeMantissa;
+ }
+ else
+ {
+ e2 = ieeeExponent - FLOAT_BIAS - FLOAT_MANTISSA_BITS - 2;
+ m2 = (1u << FLOAT_MANTISSA_BITS) | ieeeMantissa;
+ }
+
+#if STRICTLY_SHORTEST
+ const bool even = (m2 & 1) == 0;
+ const bool acceptBounds = even;
+#else
+ const bool acceptBounds = false;
+#endif
+
+ /* Step 2: Determine the interval of legal decimal representations. */
+ const uint32 mv = 4 * m2;
+ const uint32 mp = 4 * m2 + 2;
+
+ /* Implicit bool -> int conversion. True is 1, false is 0. */
+ const uint32 mmShift = ieeeMantissa != 0 || ieeeExponent <= 1;
+ const uint32 mm = 4 * m2 - 1 - mmShift;
+
+ /* Step 3: Convert to a decimal power base using 64-bit arithmetic. */
+ uint32 vr,
+ vp,
+ vm;
+ int32 e10;
+ bool vmIsTrailingZeros = false;
+ bool vrIsTrailingZeros = false;
+ uint8 lastRemovedDigit = 0;
+
+ if (e2 >= 0)
+ {
+ const uint32 q = log10Pow2(e2);
+
+ e10 = q;
+
+ const int32 k = FLOAT_POW5_INV_BITCOUNT + pow5bits(q) - 1;
+ const int32 i = -e2 + q + k;
+
+ vr = mulPow5InvDivPow2(mv, q, i);
+ vp = mulPow5InvDivPow2(mp, q, i);
+ vm = mulPow5InvDivPow2(mm, q, i);
+
+ if (q != 0 && (vp - 1) / 10 <= vm / 10)
+ {
+ /*
+ * We need to know one removed digit even if we are not going to
+ * loop below. We could use q = X - 1 above, except that would
+ * require 33 bits for the result, and we've found that 32-bit
+ * arithmetic is faster even on 64-bit machines.
+ */
+ const int32 l = FLOAT_POW5_INV_BITCOUNT + pow5bits(q - 1) - 1;
+
+ lastRemovedDigit = (uint8) (mulPow5InvDivPow2(mv, q - 1, -e2 + q - 1 + l) % 10);
+ }
+ if (q <= 9)
+ {
+ /*
+ * The largest power of 5 that fits in 24 bits is 5^10, but q <= 9
+ * seems to be safe as well.
+ *
+ * Only one of mp, mv, and mm can be a multiple of 5, if any.
+ */
+ if (mv % 5 == 0)
+ {
+ vrIsTrailingZeros = multipleOfPowerOf5(mv, q);
+ }
+ else if (acceptBounds)
+ {
+ vmIsTrailingZeros = multipleOfPowerOf5(mm, q);
+ }
+ else
+ {
+ vp -= multipleOfPowerOf5(mp, q);
+ }
+ }
+ }
+ else
+ {
+ const uint32 q = log10Pow5(-e2);
+
+ e10 = q + e2;
+
+ const int32 i = -e2 - q;
+ const int32 k = pow5bits(i) - FLOAT_POW5_BITCOUNT;
+ int32 j = q - k;
+
+ vr = mulPow5divPow2(mv, i, j);
+ vp = mulPow5divPow2(mp, i, j);
+ vm = mulPow5divPow2(mm, i, j);
+
+ if (q != 0 && (vp - 1) / 10 <= vm / 10)
+ {
+ j = q - 1 - (pow5bits(i + 1) - FLOAT_POW5_BITCOUNT);
+ lastRemovedDigit = (uint8) (mulPow5divPow2(mv, i + 1, j) % 10);
+ }
+ if (q <= 1)
+ {
+ /*
+ * {vr,vp,vm} is trailing zeros if {mv,mp,mm} has at least q
+ * trailing 0 bits.
+ */
+ /* mv = 4 * m2, so it always has at least two trailing 0 bits. */
+ vrIsTrailingZeros = true;
+ if (acceptBounds)
+ {
+ /*
+ * mm = mv - 1 - mmShift, so it has 1 trailing 0 bit iff
+ * mmShift == 1.
+ */
+ vmIsTrailingZeros = mmShift == 1;
+ }
+ else
+ {
+ /*
+ * mp = mv + 2, so it always has at least one trailing 0 bit.
+ */
+ --vp;
+ }
+ }
+ else if (q < 31)
+ {
+ /* TODO(ulfjack):Use a tighter bound here. */
+ vrIsTrailingZeros = multipleOfPowerOf2(mv, q - 1);
+ }
+ }
+
+ /*
+ * Step 4: Find the shortest decimal representation in the interval of
+ * legal representations.
+ */
+ uint32 removed = 0;
+ uint32 output;
+
+ if (vmIsTrailingZeros || vrIsTrailingZeros)
+ {
+ /* General case, which happens rarely (~4.0%). */
+ while (vp / 10 > vm / 10)
+ {
+ vmIsTrailingZeros &= vm - (vm / 10) * 10 == 0;
+ vrIsTrailingZeros &= lastRemovedDigit == 0;
+ lastRemovedDigit = (uint8) (vr % 10);
+ vr /= 10;
+ vp /= 10;
+ vm /= 10;
+ ++removed;
+ }
+ if (vmIsTrailingZeros)
+ {
+ while (vm % 10 == 0)
+ {
+ vrIsTrailingZeros &= lastRemovedDigit == 0;
+ lastRemovedDigit = (uint8) (vr % 10);
+ vr /= 10;
+ vp /= 10;
+ vm /= 10;
+ ++removed;
+ }
+ }
+
+ if (vrIsTrailingZeros && lastRemovedDigit == 5 && vr % 2 == 0)
+ {
+ /* Round even if the exact number is .....50..0. */
+ lastRemovedDigit = 4;
+ }
+
+ /*
+ * We need to take vr + 1 if vr is outside bounds or we need to round
+ * up.
+ */
+ output = vr + ((vr == vm && (!acceptBounds || !vmIsTrailingZeros)) || lastRemovedDigit >= 5);
+ }
+ else
+ {
+ /*
+ * Specialized for the common case (~96.0%). Percentages below are
+ * relative to this.
+ *
+ * Loop iterations below (approximately): 0: 13.6%, 1: 70.7%, 2:
+ * 14.1%, 3: 1.39%, 4: 0.14%, 5+: 0.01%
+ */
+ while (vp / 10 > vm / 10)
+ {
+ lastRemovedDigit = (uint8) (vr % 10);
+ vr /= 10;
+ vp /= 10;
+ vm /= 10;
+ ++removed;
+ }
+
+ /*
+ * We need to take vr + 1 if vr is outside bounds or we need to round
+ * up.
+ */
+ output = vr + (vr == vm || lastRemovedDigit >= 5);
+ }
+
+ const int32 exp = e10 + removed;
+
+ floating_decimal_32 fd;
+
+ fd.exponent = exp;
+ fd.mantissa = output;
+ return fd;
+}
+
+static inline int
+to_chars_f(const floating_decimal_32 v, const uint32 olength, char *const result)
+{
+ /* Step 5: Print the decimal representation. */
+ int index = 0;
+
+ uint32 output = v.mantissa;
+ int32 exp = v.exponent;
+
+ /*----
+ * On entry, mantissa * 10^exp is the result to be output.
+ * Caller has already done the - sign if needed.
+ *
+ * We want to insert the point somewhere depending on the output length
+ * and exponent, which might mean adding zeros:
+ *
+ * exp | format
+ * 1+ | ddddddddd000000
+ * 0 | ddddddddd
+ * -1 .. -len+1 | dddddddd.d to d.ddddddddd
+ * -len ... | 0.ddddddddd to 0.000dddddd
+ */
+ uint32 i = 0;
+ int32 nexp = exp + olength;
+
+ if (nexp <= 0)
+ {
+ /* -nexp is number of 0s to add after '.' */
+ Assert(nexp >= -3);
+ /* 0.000ddddd */
+ index = 2 - nexp;
+ /* copy 8 bytes rather than 5 to let compiler optimize */
+ memcpy(result, "0.000000", 8);
+ }
+ else if (exp < 0)
+ {
+ /*
+ * dddd.dddd; leave space at the start and move the '.' in after
+ */
+ index = 1;
+ }
+ else
+ {
+ /*
+ * We can save some code later by pre-filling with zeros. We know that
+ * there can be no more than 6 output digits in this form, otherwise
+ * we would not choose fixed-point output. memset 8 rather than 6
+ * bytes to let the compiler optimize it.
+ */
+ Assert(exp < 6 && exp + olength <= 6);
+ memset(result, '0', 8);
+ }
+
+ while (output >= 10000)
+ {
+ const uint32 c = output - 10000 * (output / 10000);
+ const uint32 c0 = (c % 100) << 1;
+ const uint32 c1 = (c / 100) << 1;
+
+ output /= 10000;
+
+ memcpy(result + index + olength - i - 2, DIGIT_TABLE + c0, 2);
+ memcpy(result + index + olength - i - 4, DIGIT_TABLE + c1, 2);
+ i += 4;
+ }
+ if (output >= 100)
+ {
+ const uint32 c = (output % 100) << 1;
+
+ output /= 100;
+ memcpy(result + index + olength - i - 2, DIGIT_TABLE + c, 2);
+ i += 2;
+ }
+ if (output >= 10)
+ {
+ const uint32 c = output << 1;
+
+ memcpy(result + index + olength - i - 2, DIGIT_TABLE + c, 2);
+ }
+ else
+ {
+ result[index] = (char) ('0' + output);
+ }
+
+ if (index == 1)
+ {
+ /*
+ * nexp is 1..6 here, representing the number of digits before the
+ * point. A value of 7+ is not possible because we switch to
+ * scientific notation when the display exponent reaches 6.
+ */
+ Assert(nexp < 7);
+ /* gcc only seems to want to optimize memmove for small 2^n */
+ if (nexp & 4)
+ {
+ memmove(result + index - 1, result + index, 4);
+ index += 4;
+ }
+ if (nexp & 2)
+ {
+ memmove(result + index - 1, result + index, 2);
+ index += 2;
+ }
+ if (nexp & 1)
+ {
+ result[index - 1] = result[index];
+ }
+ result[nexp] = '.';
+ index = olength + 1;
+ }
+ else if (exp >= 0)
+ {
+ /* we supplied the trailing zeros earlier, now just set the length. */
+ index = olength + exp;
+ }
+ else
+ {
+ index = olength + (2 - nexp);
+ }
+
+ return index;
+}
+
+static inline int
+to_chars(const floating_decimal_32 v, const bool sign, char *const result)
+{
+ /* Step 5: Print the decimal representation. */
+ int index = 0;
+
+ uint32 output = v.mantissa;
+ uint32 olength = decimalLength(output);
+ int32 exp = v.exponent + olength - 1;
+
+ if (sign)
+ result[index++] = '-';
+
+ /*
+ * The thresholds for fixed-point output are chosen to match printf
+ * defaults. Beware that both the code of to_chars_f and the value of
+ * FLOAT_SHORTEST_DECIMAL_LEN are sensitive to these thresholds.
+ */
+ if (exp >= -4 && exp < 6)
+ return to_chars_f(v, olength, result + index) + sign;
+
+ /*
+ * If v.exponent is exactly 0, we might have reached here via the small
+ * integer fast path, in which case v.mantissa might contain trailing
+ * (decimal) zeros. For scientific notation we need to move these zeros
+ * into the exponent. (For fixed point this doesn't matter, which is why
+ * we do this here rather than above.)
+ *
+ * Since we already calculated the display exponent (exp) above based on
+ * the old decimal length, that value does not change here. Instead, we
+ * just reduce the display length for each digit removed.
+ *
+ * If we didn't get here via the fast path, the raw exponent will not
+ * usually be 0, and there will be no trailing zeros, so we pay no more
+ * than one div10/multiply extra cost. We claw back half of that by
+ * checking for divisibility by 2 before dividing by 10.
+ */
+ if (v.exponent == 0)
+ {
+ while ((output & 1) == 0)
+ {
+ const uint32 q = output / 10;
+ const uint32 r = output - 10 * q;
+
+ if (r != 0)
+ break;
+ output = q;
+ --olength;
+ }
+ }
+
+ /*----
+ * Print the decimal digits.
+ * The following code is equivalent to:
+ *
+ * for (uint32 i = 0; i < olength - 1; ++i) {
+ * const uint32 c = output % 10; output /= 10;
+ * result[index + olength - i] = (char) ('0' + c);
+ * }
+ * result[index] = '0' + output % 10;
+ */
+ uint32 i = 0;
+
+ while (output >= 10000)
+ {
+ const uint32 c = output - 10000 * (output / 10000);
+ const uint32 c0 = (c % 100) << 1;
+ const uint32 c1 = (c / 100) << 1;
+
+ output /= 10000;
+
+ memcpy(result + index + olength - i - 1, DIGIT_TABLE + c0, 2);
+ memcpy(result + index + olength - i - 3, DIGIT_TABLE + c1, 2);
+ i += 4;
+ }
+ if (output >= 100)
+ {
+ const uint32 c = (output % 100) << 1;
+
+ output /= 100;
+ memcpy(result + index + olength - i - 1, DIGIT_TABLE + c, 2);
+ i += 2;
+ }
+ if (output >= 10)
+ {
+ const uint32 c = output << 1;
+
+ /*
+ * We can't use memcpy here: the decimal dot goes between these two
+ * digits.
+ */
+ result[index + olength - i] = DIGIT_TABLE[c + 1];
+ result[index] = DIGIT_TABLE[c];
+ }
+ else
+ {
+ result[index] = (char) ('0' + output);
+ }
+
+ /* Print decimal point if needed. */
+ if (olength > 1)
+ {
+ result[index + 1] = '.';
+ index += olength + 1;
+ }
+ else
+ {
+ ++index;
+ }
+
+ /* Print the exponent. */
+ result[index++] = 'e';
+ if (exp < 0)
+ {
+ result[index++] = '-';
+ exp = -exp;
+ }
+ else
+ result[index++] = '+';
+
+ memcpy(result + index, DIGIT_TABLE + 2 * exp, 2);
+ index += 2;
+
+ return index;
+}
+
+static inline bool
+f2d_small_int(const uint32 ieeeMantissa,
+ const uint32 ieeeExponent,
+ floating_decimal_32 *v)
+{
+ const int32 e2 = (int32) ieeeExponent - FLOAT_BIAS - FLOAT_MANTISSA_BITS;
+
+ /*
+ * Avoid using multiple "return false;" here since it tends to provoke the
+ * compiler into inlining multiple copies of f2d, which is undesirable.
+ */
+
+ if (e2 >= -FLOAT_MANTISSA_BITS && e2 <= 0)
+ {
+ /*----
+ * Since 2^23 <= m2 < 2^24 and 0 <= -e2 <= 23:
+ * 1 <= f = m2 / 2^-e2 < 2^24.
+ *
+ * Test if the lower -e2 bits of the significand are 0, i.e. whether
+ * the fraction is 0. We can use ieeeMantissa here, since the implied
+ * 1 bit can never be tested by this; the implied 1 can only be part
+ * of a fraction if e2 < -FLOAT_MANTISSA_BITS which we already
+ * checked. (e.g. 0.5 gives ieeeMantissa == 0 and e2 == -24)
+ */
+ const uint32 mask = (1U << -e2) - 1;
+ const uint32 fraction = ieeeMantissa & mask;
+
+ if (fraction == 0)
+ {
+ /*----
+ * f is an integer in the range [1, 2^24).
+ * Note: mantissa might contain trailing (decimal) 0's.
+ * Note: since 2^24 < 10^9, there is no need to adjust
+ * decimalLength().
+ */
+ const uint32 m2 = (1U << FLOAT_MANTISSA_BITS) | ieeeMantissa;
+
+ v->mantissa = m2 >> -e2;
+ v->exponent = 0;
+ return true;
+ }
+ }
+
+ return false;
+}
+
+/*
+ * Store the shortest decimal representation of the given float as an
+ * UNTERMINATED string in the caller's supplied buffer (which must be at least
+ * FLOAT_SHORTEST_DECIMAL_LEN-1 bytes long).
+ *
+ * Returns the number of bytes stored.
+ */
+int
+float_to_shortest_decimal_bufn(float f, char *result)
+{
+ /*
+ * Step 1: Decode the floating-point number, and unify normalized and
+ * subnormal cases.
+ */
+ const uint32 bits = float_to_bits(f);
+
+ /* Decode bits into sign, mantissa, and exponent. */
+ const bool ieeeSign = ((bits >> (FLOAT_MANTISSA_BITS + FLOAT_EXPONENT_BITS)) & 1) != 0;
+ const uint32 ieeeMantissa = bits & ((1u << FLOAT_MANTISSA_BITS) - 1);
+ const uint32 ieeeExponent = (bits >> FLOAT_MANTISSA_BITS) & ((1u << FLOAT_EXPONENT_BITS) - 1);
+
+ /* Case distinction; exit early for the easy cases. */
+ if (ieeeExponent == ((1u << FLOAT_EXPONENT_BITS) - 1u) || (ieeeExponent == 0 && ieeeMantissa == 0))
+ {
+ return copy_special_str(result, ieeeSign, (ieeeExponent != 0), (ieeeMantissa != 0));
+ }
+
+ floating_decimal_32 v;
+ const bool isSmallInt = f2d_small_int(ieeeMantissa, ieeeExponent, &v);
+
+ if (!isSmallInt)
+ {
+ v = f2d(ieeeMantissa, ieeeExponent);
+ }
+
+ return to_chars(v, ieeeSign, result);
+}
+
+/*
+ * Store the shortest decimal representation of the given float as a
+ * null-terminated string in the caller's supplied buffer (which must be at
+ * least FLOAT_SHORTEST_DECIMAL_LEN bytes long).
+ *
+ * Returns the string length.
+ */
+int
+float_to_shortest_decimal_buf(float f, char *result)
+{
+ const int index = float_to_shortest_decimal_bufn(f, result);
+
+ /* Terminate the string. */
+ Assert(index < FLOAT_SHORTEST_DECIMAL_LEN);
+ result[index] = '\0';
+ return index;
+}
+
+/*
+ * Return the shortest decimal representation as a null-terminated palloc'd
+ * string (outside the backend, uses malloc() instead).
+ *
+ * Caller is responsible for freeing the result.
+ */
+char *
+float_to_shortest_decimal(float f)
+{
+ char *const result = (char *) palloc(FLOAT_SHORTEST_DECIMAL_LEN);
+
+ float_to_shortest_decimal_buf(f, result);
+ return result;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-02 01:59:36 +0000