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1 : /*---------------------------------------------------------------------------
2 : *
3 : * Common routines for Ryu floating-point output.
4 : *
5 : * Portions Copyright (c) 2018-2026, PostgreSQL Global Development Group
6 : *
7 : * IDENTIFICATION
8 : * src/common/ryu_common.h
9 : *
10 : * This is a modification of code taken from github.com/ulfjack/ryu under the
11 : * terms of the Boost license (not the Apache license). The original copyright
12 : * notice follows:
13 : *
14 : * Copyright 2018 Ulf Adams
15 : *
16 : * The contents of this file may be used under the terms of the Apache
17 : * License, Version 2.0.
18 : *
19 : * (See accompanying file LICENSE-Apache or copy at
20 : * http://www.apache.org/licenses/LICENSE-2.0)
21 : *
22 : * Alternatively, the contents of this file may be used under the terms of the
23 : * Boost Software License, Version 1.0.
24 : *
25 : * (See accompanying file LICENSE-Boost or copy at
26 : * https://www.boost.org/LICENSE_1_0.txt)
27 : *
28 : * Unless required by applicable law or agreed to in writing, this software is
29 : * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
30 : * KIND, either express or implied.
31 : *
32 : *---------------------------------------------------------------------------
33 : */
34 : #ifndef RYU_COMMON_H
35 : #define RYU_COMMON_H
36 :
37 : /*
38 : * Upstream Ryu's output is always the shortest possible. But we adjust that
39 : * slightly to improve portability: we avoid outputting the exact midpoint
40 : * value between two representable floats, since that relies on the reader
41 : * getting the round-to-even rule correct, which seems to be the common
42 : * failure mode.
43 : *
44 : * Defining this to 1 would restore the upstream behavior.
45 : */
46 : #define STRICTLY_SHORTEST 0
47 :
48 : #if SIZEOF_SIZE_T < 8
49 : #define RYU_32_BIT_PLATFORM
50 : #endif
51 :
52 : /* Returns e == 0 ? 1 : ceil(log_2(5^e)). */
53 : static inline uint32
54 1953762 : pow5bits(const int32 e)
55 : {
56 : /*
57 : * This approximation works up to the point that the multiplication
58 : * overflows at e = 3529.
59 : *
60 : * If the multiplication were done in 64 bits, it would fail at 5^4004
61 : * which is just greater than 2^9297.
62 : */
63 : Assert(e >= 0);
64 : Assert(e <= 3528);
65 1953762 : return ((((uint32) e) * 1217359) >> 19) + 1;
66 : }
67 :
68 : /* Returns floor(log_10(2^e)). */
69 : static inline int32
70 1602 : log10Pow2(const int32 e)
71 : {
72 : /*
73 : * The first value this approximation fails for is 2^1651 which is just
74 : * greater than 10^297.
75 : */
76 : Assert(e >= 0);
77 : Assert(e <= 1650);
78 1602 : return (int32) ((((uint32) e) * 78913) >> 18);
79 : }
80 :
81 : /* Returns floor(log_10(5^e)). */
82 : static inline int32
83 1944184 : log10Pow5(const int32 e)
84 : {
85 : /*
86 : * The first value this approximation fails for is 5^2621 which is just
87 : * greater than 10^1832.
88 : */
89 : Assert(e >= 0);
90 : Assert(e <= 2620);
91 1944184 : return (int32) ((((uint32) e) * 732923) >> 20);
92 : }
93 :
94 : static inline int
95 458515 : copy_special_str(char *const result, const bool sign, const bool exponent, const bool mantissa)
96 : {
97 458515 : if (mantissa)
98 : {
99 264 : memcpy(result, "NaN", 3);
100 264 : return 3;
101 : }
102 458251 : if (sign)
103 : {
104 206 : result[0] = '-';
105 : }
106 458251 : if (exponent)
107 : {
108 543 : memcpy(result + sign, "Infinity", 8);
109 543 : return sign + 8;
110 : }
111 457708 : result[sign] = '0';
112 457708 : return sign + 1;
113 : }
114 :
115 : static inline uint32
116 174791 : float_to_bits(const float f)
117 : {
118 174791 : uint32 bits = 0;
119 :
120 174791 : memcpy(&bits, &f, sizeof(float));
121 174791 : return bits;
122 : }
123 :
124 : static inline uint64
125 4354693 : double_to_bits(const double d)
126 : {
127 4354693 : uint64 bits = 0;
128 :
129 4354693 : memcpy(&bits, &d, sizeof(double));
130 4354693 : return bits;
131 : }
132 :
133 : #endif /* RYU_COMMON_H */
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