804 lines
21 KiB
C
804 lines
21 KiB
C
/*---------------------------------------------------------------------------
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*
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* Ryu floating-point output for single precision.
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*
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* Portions Copyright (c) 2018-2023, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/common/f2s.c
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*
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* This is a modification of code taken from github.com/ulfjack/ryu under the
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* terms of the Boost license (not the Apache license). The original copyright
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* notice follows:
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*
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* Copyright 2018 Ulf Adams
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*
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* The contents of this file may be used under the terms of the Apache
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* License, Version 2.0.
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*
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* (See accompanying file LICENSE-Apache or copy at
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* http://www.apache.org/licenses/LICENSE-2.0)
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*
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* Alternatively, the contents of this file may be used under the terms of the
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* Boost Software License, Version 1.0.
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*
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* (See accompanying file LICENSE-Boost or copy at
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* https://www.boost.org/LICENSE_1_0.txt)
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*
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* Unless required by applicable law or agreed to in writing, this software is
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* distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied.
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*
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*---------------------------------------------------------------------------
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*/
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#ifndef FRONTEND
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#include "postgres.h"
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#else
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#include "postgres_fe.h"
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#endif
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#include "common/shortest_dec.h"
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#include "digit_table.h"
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#include "ryu_common.h"
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#define FLOAT_MANTISSA_BITS 23
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#define FLOAT_EXPONENT_BITS 8
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#define FLOAT_BIAS 127
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/*
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* This table is generated (by the upstream) by PrintFloatLookupTable,
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* and modified (by us) to add UINT64CONST.
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*/
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#define FLOAT_POW5_INV_BITCOUNT 59
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static const uint64 FLOAT_POW5_INV_SPLIT[31] = {
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UINT64CONST(576460752303423489), UINT64CONST(461168601842738791), UINT64CONST(368934881474191033), UINT64CONST(295147905179352826),
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UINT64CONST(472236648286964522), UINT64CONST(377789318629571618), UINT64CONST(302231454903657294), UINT64CONST(483570327845851670),
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UINT64CONST(386856262276681336), UINT64CONST(309485009821345069), UINT64CONST(495176015714152110), UINT64CONST(396140812571321688),
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UINT64CONST(316912650057057351), UINT64CONST(507060240091291761), UINT64CONST(405648192073033409), UINT64CONST(324518553658426727),
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UINT64CONST(519229685853482763), UINT64CONST(415383748682786211), UINT64CONST(332306998946228969), UINT64CONST(531691198313966350),
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UINT64CONST(425352958651173080), UINT64CONST(340282366920938464), UINT64CONST(544451787073501542), UINT64CONST(435561429658801234),
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UINT64CONST(348449143727040987), UINT64CONST(557518629963265579), UINT64CONST(446014903970612463), UINT64CONST(356811923176489971),
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UINT64CONST(570899077082383953), UINT64CONST(456719261665907162), UINT64CONST(365375409332725730)
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};
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#define FLOAT_POW5_BITCOUNT 61
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static const uint64 FLOAT_POW5_SPLIT[47] = {
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UINT64CONST(1152921504606846976), UINT64CONST(1441151880758558720), UINT64CONST(1801439850948198400), UINT64CONST(2251799813685248000),
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UINT64CONST(1407374883553280000), UINT64CONST(1759218604441600000), UINT64CONST(2199023255552000000), UINT64CONST(1374389534720000000),
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UINT64CONST(1717986918400000000), UINT64CONST(2147483648000000000), UINT64CONST(1342177280000000000), UINT64CONST(1677721600000000000),
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UINT64CONST(2097152000000000000), UINT64CONST(1310720000000000000), UINT64CONST(1638400000000000000), UINT64CONST(2048000000000000000),
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UINT64CONST(1280000000000000000), UINT64CONST(1600000000000000000), UINT64CONST(2000000000000000000), UINT64CONST(1250000000000000000),
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UINT64CONST(1562500000000000000), UINT64CONST(1953125000000000000), UINT64CONST(1220703125000000000), UINT64CONST(1525878906250000000),
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UINT64CONST(1907348632812500000), UINT64CONST(1192092895507812500), UINT64CONST(1490116119384765625), UINT64CONST(1862645149230957031),
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UINT64CONST(1164153218269348144), UINT64CONST(1455191522836685180), UINT64CONST(1818989403545856475), UINT64CONST(2273736754432320594),
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UINT64CONST(1421085471520200371), UINT64CONST(1776356839400250464), UINT64CONST(2220446049250313080), UINT64CONST(1387778780781445675),
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UINT64CONST(1734723475976807094), UINT64CONST(2168404344971008868), UINT64CONST(1355252715606880542), UINT64CONST(1694065894508600678),
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UINT64CONST(2117582368135750847), UINT64CONST(1323488980084844279), UINT64CONST(1654361225106055349), UINT64CONST(2067951531382569187),
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UINT64CONST(1292469707114105741), UINT64CONST(1615587133892632177), UINT64CONST(2019483917365790221)
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};
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static inline uint32
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pow5Factor(uint32 value)
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{
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uint32 count = 0;
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for (;;)
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{
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Assert(value != 0);
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const uint32 q = value / 5;
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const uint32 r = value % 5;
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if (r != 0)
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break;
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value = q;
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++count;
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}
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return count;
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}
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/* Returns true if value is divisible by 5^p. */
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static inline bool
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multipleOfPowerOf5(const uint32 value, const uint32 p)
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{
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return pow5Factor(value) >= p;
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}
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/* Returns true if value is divisible by 2^p. */
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static inline bool
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multipleOfPowerOf2(const uint32 value, const uint32 p)
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{
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/* return __builtin_ctz(value) >= p; */
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return (value & ((1u << p) - 1)) == 0;
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}
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/*
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* It seems to be slightly faster to avoid uint128_t here, although the
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* generated code for uint128_t looks slightly nicer.
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*/
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static inline uint32
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mulShift(const uint32 m, const uint64 factor, const int32 shift)
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{
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/*
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* The casts here help MSVC to avoid calls to the __allmul library
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* function.
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*/
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const uint32 factorLo = (uint32) (factor);
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const uint32 factorHi = (uint32) (factor >> 32);
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const uint64 bits0 = (uint64) m * factorLo;
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const uint64 bits1 = (uint64) m * factorHi;
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Assert(shift > 32);
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#ifdef RYU_32_BIT_PLATFORM
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/*
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* On 32-bit platforms we can avoid a 64-bit shift-right since we only
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* need the upper 32 bits of the result and the shift value is > 32.
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*/
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const uint32 bits0Hi = (uint32) (bits0 >> 32);
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uint32 bits1Lo = (uint32) (bits1);
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uint32 bits1Hi = (uint32) (bits1 >> 32);
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bits1Lo += bits0Hi;
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bits1Hi += (bits1Lo < bits0Hi);
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const int32 s = shift - 32;
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return (bits1Hi << (32 - s)) | (bits1Lo >> s);
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#else /* RYU_32_BIT_PLATFORM */
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const uint64 sum = (bits0 >> 32) + bits1;
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const uint64 shiftedSum = sum >> (shift - 32);
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Assert(shiftedSum <= PG_UINT32_MAX);
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return (uint32) shiftedSum;
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#endif /* RYU_32_BIT_PLATFORM */
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}
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static inline uint32
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mulPow5InvDivPow2(const uint32 m, const uint32 q, const int32 j)
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{
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return mulShift(m, FLOAT_POW5_INV_SPLIT[q], j);
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}
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static inline uint32
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mulPow5divPow2(const uint32 m, const uint32 i, const int32 j)
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{
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return mulShift(m, FLOAT_POW5_SPLIT[i], j);
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}
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static inline uint32
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decimalLength(const uint32 v)
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{
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/* Function precondition: v is not a 10-digit number. */
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/* (9 digits are sufficient for round-tripping.) */
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Assert(v < 1000000000);
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if (v >= 100000000)
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{
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return 9;
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}
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if (v >= 10000000)
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{
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return 8;
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}
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if (v >= 1000000)
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{
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return 7;
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}
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if (v >= 100000)
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{
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return 6;
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}
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if (v >= 10000)
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{
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return 5;
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}
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if (v >= 1000)
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{
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return 4;
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}
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if (v >= 100)
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{
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return 3;
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}
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if (v >= 10)
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{
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return 2;
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}
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return 1;
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}
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/* A floating decimal representing m * 10^e. */
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typedef struct floating_decimal_32
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{
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uint32 mantissa;
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int32 exponent;
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} floating_decimal_32;
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static inline floating_decimal_32
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f2d(const uint32 ieeeMantissa, const uint32 ieeeExponent)
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{
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int32 e2;
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uint32 m2;
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if (ieeeExponent == 0)
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{
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/* We subtract 2 so that the bounds computation has 2 additional bits. */
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e2 = 1 - FLOAT_BIAS - FLOAT_MANTISSA_BITS - 2;
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m2 = ieeeMantissa;
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}
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else
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{
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e2 = ieeeExponent - FLOAT_BIAS - FLOAT_MANTISSA_BITS - 2;
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m2 = (1u << FLOAT_MANTISSA_BITS) | ieeeMantissa;
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}
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#if STRICTLY_SHORTEST
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const bool even = (m2 & 1) == 0;
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const bool acceptBounds = even;
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#else
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const bool acceptBounds = false;
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#endif
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/* Step 2: Determine the interval of legal decimal representations. */
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const uint32 mv = 4 * m2;
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const uint32 mp = 4 * m2 + 2;
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/* Implicit bool -> int conversion. True is 1, false is 0. */
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const uint32 mmShift = ieeeMantissa != 0 || ieeeExponent <= 1;
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const uint32 mm = 4 * m2 - 1 - mmShift;
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/* Step 3: Convert to a decimal power base using 64-bit arithmetic. */
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uint32 vr,
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vp,
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vm;
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int32 e10;
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bool vmIsTrailingZeros = false;
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bool vrIsTrailingZeros = false;
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uint8 lastRemovedDigit = 0;
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if (e2 >= 0)
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{
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const uint32 q = log10Pow2(e2);
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e10 = q;
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const int32 k = FLOAT_POW5_INV_BITCOUNT + pow5bits(q) - 1;
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const int32 i = -e2 + q + k;
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vr = mulPow5InvDivPow2(mv, q, i);
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vp = mulPow5InvDivPow2(mp, q, i);
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vm = mulPow5InvDivPow2(mm, q, i);
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if (q != 0 && (vp - 1) / 10 <= vm / 10)
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{
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/*
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* We need to know one removed digit even if we are not going to
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* loop below. We could use q = X - 1 above, except that would
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* require 33 bits for the result, and we've found that 32-bit
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* arithmetic is faster even on 64-bit machines.
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*/
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const int32 l = FLOAT_POW5_INV_BITCOUNT + pow5bits(q - 1) - 1;
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lastRemovedDigit = (uint8) (mulPow5InvDivPow2(mv, q - 1, -e2 + q - 1 + l) % 10);
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}
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if (q <= 9)
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{
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/*
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* The largest power of 5 that fits in 24 bits is 5^10, but q <= 9
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* seems to be safe as well.
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*
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* Only one of mp, mv, and mm can be a multiple of 5, if any.
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*/
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if (mv % 5 == 0)
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{
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vrIsTrailingZeros = multipleOfPowerOf5(mv, q);
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}
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else if (acceptBounds)
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{
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vmIsTrailingZeros = multipleOfPowerOf5(mm, q);
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}
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else
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{
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vp -= multipleOfPowerOf5(mp, q);
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}
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}
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}
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else
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{
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const uint32 q = log10Pow5(-e2);
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e10 = q + e2;
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const int32 i = -e2 - q;
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const int32 k = pow5bits(i) - FLOAT_POW5_BITCOUNT;
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int32 j = q - k;
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vr = mulPow5divPow2(mv, i, j);
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vp = mulPow5divPow2(mp, i, j);
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vm = mulPow5divPow2(mm, i, j);
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if (q != 0 && (vp - 1) / 10 <= vm / 10)
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{
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j = q - 1 - (pow5bits(i + 1) - FLOAT_POW5_BITCOUNT);
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lastRemovedDigit = (uint8) (mulPow5divPow2(mv, i + 1, j) % 10);
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}
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if (q <= 1)
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{
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/*
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* {vr,vp,vm} is trailing zeros if {mv,mp,mm} has at least q
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* trailing 0 bits.
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*/
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/* mv = 4 * m2, so it always has at least two trailing 0 bits. */
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vrIsTrailingZeros = true;
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if (acceptBounds)
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{
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/*
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* mm = mv - 1 - mmShift, so it has 1 trailing 0 bit iff
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* mmShift == 1.
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*/
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vmIsTrailingZeros = mmShift == 1;
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}
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else
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{
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/*
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* mp = mv + 2, so it always has at least one trailing 0 bit.
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*/
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--vp;
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}
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}
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else if (q < 31)
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{
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/* TODO(ulfjack):Use a tighter bound here. */
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vrIsTrailingZeros = multipleOfPowerOf2(mv, q - 1);
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}
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}
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/*
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* Step 4: Find the shortest decimal representation in the interval of
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* legal representations.
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*/
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uint32 removed = 0;
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uint32 output;
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if (vmIsTrailingZeros || vrIsTrailingZeros)
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{
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/* General case, which happens rarely (~4.0%). */
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while (vp / 10 > vm / 10)
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{
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vmIsTrailingZeros &= vm - (vm / 10) * 10 == 0;
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vrIsTrailingZeros &= lastRemovedDigit == 0;
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lastRemovedDigit = (uint8) (vr % 10);
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vr /= 10;
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vp /= 10;
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vm /= 10;
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++removed;
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}
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if (vmIsTrailingZeros)
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{
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while (vm % 10 == 0)
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{
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vrIsTrailingZeros &= lastRemovedDigit == 0;
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lastRemovedDigit = (uint8) (vr % 10);
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vr /= 10;
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vp /= 10;
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vm /= 10;
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++removed;
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}
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}
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if (vrIsTrailingZeros && lastRemovedDigit == 5 && vr % 2 == 0)
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{
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/* Round even if the exact number is .....50..0. */
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lastRemovedDigit = 4;
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}
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/*
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* We need to take vr + 1 if vr is outside bounds or we need to round
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* up.
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*/
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output = vr + ((vr == vm && (!acceptBounds || !vmIsTrailingZeros)) || lastRemovedDigit >= 5);
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}
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else
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{
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/*
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* Specialized for the common case (~96.0%). Percentages below are
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* relative to this.
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*
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* Loop iterations below (approximately): 0: 13.6%, 1: 70.7%, 2:
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* 14.1%, 3: 1.39%, 4: 0.14%, 5+: 0.01%
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*/
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while (vp / 10 > vm / 10)
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{
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lastRemovedDigit = (uint8) (vr % 10);
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vr /= 10;
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vp /= 10;
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vm /= 10;
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++removed;
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}
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/*
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* We need to take vr + 1 if vr is outside bounds or we need to round
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* up.
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*/
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output = vr + (vr == vm || lastRemovedDigit >= 5);
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}
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const int32 exp = e10 + removed;
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floating_decimal_32 fd;
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fd.exponent = exp;
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fd.mantissa = output;
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return fd;
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}
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static inline int
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to_chars_f(const floating_decimal_32 v, const uint32 olength, char *const result)
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{
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/* Step 5: Print the decimal representation. */
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int index = 0;
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uint32 output = v.mantissa;
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int32 exp = v.exponent;
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/*----
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* On entry, mantissa * 10^exp is the result to be output.
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* Caller has already done the - sign if needed.
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*
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* We want to insert the point somewhere depending on the output length
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* and exponent, which might mean adding zeros:
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*
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* exp | format
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* 1+ | ddddddddd000000
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* 0 | ddddddddd
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* -1 .. -len+1 | dddddddd.d to d.ddddddddd
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* -len ... | 0.ddddddddd to 0.000dddddd
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*/
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uint32 i = 0;
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int32 nexp = exp + olength;
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if (nexp <= 0)
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{
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/* -nexp is number of 0s to add after '.' */
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Assert(nexp >= -3);
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/* 0.000ddddd */
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index = 2 - nexp;
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/* copy 8 bytes rather than 5 to let compiler optimize */
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memcpy(result, "0.000000", 8);
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}
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else if (exp < 0)
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{
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/*
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* dddd.dddd; leave space at the start and move the '.' in after
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*/
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index = 1;
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}
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else
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{
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/*
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* We can save some code later by pre-filling with zeros. We know that
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* there can be no more than 6 output digits in this form, otherwise
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* we would not choose fixed-point output. memset 8 rather than 6
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* bytes to let the compiler optimize it.
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*/
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Assert(exp < 6 && exp + olength <= 6);
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memset(result, '0', 8);
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}
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while (output >= 10000)
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{
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const uint32 c = output - 10000 * (output / 10000);
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const uint32 c0 = (c % 100) << 1;
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const uint32 c1 = (c / 100) << 1;
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|
|
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;
|
|
}
|