charconv.cpp revision 337143 
1//===------------------------- charconv.cpp -------------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is dual licensed under the MIT and the University of Illinois Open
6// Source Licenses. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "charconv"
11#include <string.h>
12
13_LIBCPP_BEGIN_NAMESPACE_STD
14
15namespace __itoa
16{
17
18static constexpr char cDigitsLut[200] = {
19    '0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0',
20    '7', '0', '8', '0', '9', '1', '0', '1', '1', '1', '2', '1', '3', '1', '4',
21    '1', '5', '1', '6', '1', '7', '1', '8', '1', '9', '2', '0', '2', '1', '2',
22    '2', '2', '3', '2', '4', '2', '5', '2', '6', '2', '7', '2', '8', '2', '9',
23    '3', '0', '3', '1', '3', '2', '3', '3', '3', '4', '3', '5', '3', '6', '3',
24    '7', '3', '8', '3', '9', '4', '0', '4', '1', '4', '2', '4', '3', '4', '4',
25    '4', '5', '4', '6', '4', '7', '4', '8', '4', '9', '5', '0', '5', '1', '5',
26    '2', '5', '3', '5', '4', '5', '5', '5', '6', '5', '7', '5', '8', '5', '9',
27    '6', '0', '6', '1', '6', '2', '6', '3', '6', '4', '6', '5', '6', '6', '6',
28    '7', '6', '8', '6', '9', '7', '0', '7', '1', '7', '2', '7', '3', '7', '4',
29    '7', '5', '7', '6', '7', '7', '7', '8', '7', '9', '8', '0', '8', '1', '8',
30    '2', '8', '3', '8', '4', '8', '5', '8', '6', '8', '7', '8', '8', '8', '9',
31    '9', '0', '9', '1', '9', '2', '9', '3', '9', '4', '9', '5', '9', '6', '9',
32    '7', '9', '8', '9', '9'};
33
34template <typename T>
35inline _LIBCPP_INLINE_VISIBILITY char*
36append1(char* buffer, T i)
37{
38    *buffer = '0' + static_cast<char>(i);
39    return buffer + 1;
40}
41
42template <typename T>
43inline _LIBCPP_INLINE_VISIBILITY char*
44append2(char* buffer, T i)
45{
46    memcpy(buffer, &cDigitsLut[(i)*2], 2);
47    return buffer + 2;
48}
49
50template <typename T>
51inline _LIBCPP_INLINE_VISIBILITY char*
52append3(char* buffer, T i)
53{
54    return append2(append1(buffer, (i) / 100), (i) % 100);
55}
56
57template <typename T>
58inline _LIBCPP_INLINE_VISIBILITY char*
59append4(char* buffer, T i)
60{
61    return append2(append2(buffer, (i) / 100), (i) % 100);
62}
63
64char*
65__u32toa(uint32_t value, char* buffer)
66{
67    if (value < 10000)
68    {
69        if (value < 100)
70        {
71            if (value < 10)
72                buffer = append1(buffer, value);
73            else
74                buffer = append2(buffer, value);
75        }
76        else
77        {
78            if (value < 1000)
79                buffer = append3(buffer, value);
80            else
81                buffer = append4(buffer, value);
82        }
83    }
84    else if (value < 100000000)
85    {
86        // value = bbbbcccc
87        const uint32_t b = value / 10000;
88        const uint32_t c = value % 10000;
89
90        if (value < 1000000)
91        {
92            if (value < 100000)
93                buffer = append1(buffer, b);
94            else
95                buffer = append2(buffer, b);
96        }
97        else
98        {
99            if (value < 10000000)
100                buffer = append3(buffer, b);
101            else
102                buffer = append4(buffer, b);
103        }
104
105        buffer = append4(buffer, c);
106    }
107    else
108    {
109        // value = aabbbbcccc in decimal
110        const uint32_t a = value / 100000000;  // 1 to 42
111        value %= 100000000;
112
113        if (a < 10)
114            buffer = append1(buffer, a);
115        else
116            buffer = append2(buffer, a);
117
118        buffer = append4(buffer, value / 10000);
119        buffer = append4(buffer, value % 10000);
120    }
121
122    return buffer;
123}
124
125char*
126__u64toa(uint64_t value, char* buffer)
127{
128    if (value < 100000000)
129    {
130        uint32_t v = static_cast<uint32_t>(value);
131        if (v < 10000)
132        {
133            if (v < 100)
134            {
135                if (v < 10)
136                    buffer = append1(buffer, v);
137                else
138                    buffer = append2(buffer, v);
139            }
140            else
141            {
142                if (v < 1000)
143                    buffer = append3(buffer, v);
144                else
145                    buffer = append4(buffer, v);
146            }
147        }
148        else
149        {
150            // value = bbbbcccc
151            const uint32_t b = v / 10000;
152            const uint32_t c = v % 10000;
153
154            if (v < 1000000)
155            {
156                if (v < 100000)
157                    buffer = append1(buffer, b);
158                else
159                    buffer = append2(buffer, b);
160            }
161            else
162            {
163                if (v < 10000000)
164                    buffer = append3(buffer, b);
165                else
166                    buffer = append4(buffer, b);
167            }
168
169            buffer = append4(buffer, c);
170        }
171    }
172    else if (value < 10000000000000000)
173    {
174        const uint32_t v0 = static_cast<uint32_t>(value / 100000000);
175        const uint32_t v1 = static_cast<uint32_t>(value % 100000000);
176
177        const uint32_t b0 = v0 / 10000;
178        const uint32_t c0 = v0 % 10000;
179
180        if (v0 < 1000000)
181        {
182            if (v0 < 100000)
183                buffer = append1(buffer, b0);
184            else
185                buffer = append2(buffer, b0);
186        }
187        else
188        {
189            if (v0 < 10000000)
190                buffer = append3(buffer, b0);
191            else
192                buffer = append4(buffer, b0);
193        }
194
195        buffer = append4(buffer, c0);
196        buffer = append4(buffer, v1 / 10000);
197        buffer = append4(buffer, v1 % 10000);
198    }
199    else
200    {
201        const uint32_t a =
202            static_cast<uint32_t>(value / 10000000000000000);  // 1 to 1844
203        value %= 10000000000000000;
204
205        if (a < 100)
206        {
207            if (a < 10)
208                buffer = append1(buffer, a);
209            else
210                buffer = append2(buffer, a);
211        }
212        else
213        {
214            if (a < 1000)
215                buffer = append3(buffer, a);
216            else
217                buffer = append4(buffer, a);
218        }
219
220        const uint32_t v0 = static_cast<uint32_t>(value / 100000000);
221        const uint32_t v1 = static_cast<uint32_t>(value % 100000000);
222        buffer = append4(buffer, v0 / 10000);
223        buffer = append4(buffer, v0 % 10000);
224        buffer = append4(buffer, v1 / 10000);
225        buffer = append4(buffer, v1 % 10000);
226    }
227
228    return buffer;
229}
230
231}  // namespace __itoa
232
233_LIBCPP_END_NAMESPACE_STD
234