贡献一个开源的浮点数转字符串函数，附带随机舍入函数

test01

1. /* This Source Code Form is subject to the terms of the Mozilla Public
   
2. * License, v. 2.0. If a copy of the MPL was not distributed with this
   
3. * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   
4. 
   
5. double random_round (double x, int_fast8_t rounded_to_exp10)
   
6. {
   
7.   const uint_fast8_t MAX_SIGNIFICANT_FIGURES = 5;  //float floor(log10(pow(2, 23)))-1, double floor(log10(pow(2, 52)))-1
   
8.   
   
9.   if (not isfinite(x))
   
10.   {
    
11.     return x;
    
12.   }
    
13.   double absolute_value = fabs(x);
    
14.   if ((floor(log10(absolute_value)) - rounded_to_exp10) >= MAX_SIGNIFICANT_FIGURES)
    
15.   {
    
16.     return x;
    
17.   }
    
18.   
    
19.   double integer_part, decimal_part;
    
20.   decimal_part = modf(absolute_value * pow(10, -rounded_to_exp10), &integer_part);
    
21.   if(decimal_part > 0.5)
    
22.   {
    
23.     integer_part += 1;
    
24.   }
    
25.   else
    
26.   {
    
27.     if(decimal_part == 0.5)
    
28.     {
    
29.       integer_part += rand() % 2;
    
30.     }
    
31.   }
    
32.   return copysign((integer_part + 0.1) * pow(10, rounded_to_exp10), x);
    
33. }
    
34. 
    
35. uint_fast8_t floating_number_to_string (double input_number, uint_fast8_t decimal_digits, char numeric_string[], uint_fast8_t array_len)  //input_number range is 99999 to 0.000001. Returns the numeric string length. The random roundoff, pay attention to the random number seed.
    
36. {
    
37.   const uint_fast8_t MAX_SIGNIFICANT_FIGURES = 5;  //float floor(log10(2^23))-1
    
38.   const uint_fast8_t MIN_DECIMAL = 6;
    
39.   
    
40.   char temp_string[10];  //a sign + (decimal_digits == 0 ? MAX_SIGNIFICANT_FIGURES : max((MAX_SIGNIFICANT_FIGURES + a decimal), (a zero + a decimal + MIN_DECIMAL))) + '\x0'
    
41.   double absolute_value;
    
42.   double num_exp10;
    
43. 
    
44.   if (not isfinite(input_number))
    
45.   {
    
46.     return 0;
    
47.   }
    
48.   if (decimal_digits > MIN_DECIMAL)
    
49.   {
    
50.     return 0;
    
51.   }
    
52.   
    
53.   absolute_value = fabs(input_number);
    
54.   num_exp10 = floor(log10(absolute_value));
    
55.   if (num_exp10 >= MAX_SIGNIFICANT_FIGURES)
    
56.   {  //Value ultra range error
    
57.     return 0;
    
58.   }
    
59.   double num_tail_exp10 = fmax((num_exp10 + 1 - MAX_SIGNIFICANT_FIGURES), (-((int_fast8_t)decimal_digits)));  //Plus integer part
    
60.   input_number = random_round(absolute_value, lround(num_tail_exp10));
    
61.   
    
62.   absolute_value = fabs(input_number);
    
63.   num_exp10 = floor(log10(absolute_value));
    
64.   int_fast8_t num_int_exp10 = lround(num_exp10);
    
65.   if (num_int_exp10 >= MAX_SIGNIFICANT_FIGURES)
    
66.   {  //Value ultra range error
    
67.     return 0;
    
68.   }
    
69.   num_tail_exp10 = fmax((num_exp10 + 1 - MAX_SIGNIFICANT_FIGURES), (-((int_fast8_t)decimal_digits)));  //Plus integer part
    
70.   int_fast8_t num_int_tail_exp10 = lround(num_tail_exp10);
    
71.   if (num_int_tail_exp10 > num_int_exp10)
    
72.   {
    
73.     num_exp10 = num_tail_exp10;
    
74.     num_int_exp10 = num_int_tail_exp10;
    
75.   }
    
76.   
    
77.   uint_fast8_t num_count = num_int_exp10 - num_int_tail_exp10 + 1;
    
78.   double intermediate_number = absolute_value * pow(10, -num_exp10);
    
79.   double digital_character[num_count];
    
80.   for (int_fast8_t i = 0; i < num_count; ++i)
    
81.   {
    
82.     intermediate_number = modf(intermediate_number, &digital_character[i]) * 10;
    
83.   }
    
84.   
    
85.   int_fast8_t i = 0;
    
86.   uint_fast8_t n;
    
87.   if ((input_number < 0 ? 1 : 0) == 1)
    
88.   {
    
89.     temp_string[i] = '-'; ++i;
    
90.   }
    
91.   int_fast8_t j = 0;
    
92.   if (num_int_exp10 >= 0)
    
93.   {
    
94.     n = i + num_int_exp10;
    
95.     while(i <= n)
    
96.     {
    
97.       temp_string[i] = (char)(lround(digital_character[j]) + 0x30);  //0x30 == '0'
    
98.       ++i;
    
99.       ++j;
    
100.     }
     
101.     if ((num_int_tail_exp10 < 0 ? 1 : 0) == 1)
     
102.     {
     
103.       temp_string[i] = '.'; ++i;
     
104.     }
     
105.     n = i + abs(num_int_tail_exp10);
     
106.     while(i < n)
     
107.     {
     
108.       temp_string[i] = (char)(lround(digital_character[j]) + 0x30);  //0x30 == '0'
     
109.       ++i;
     
110.       ++j;
     
111.     }
     
112.   }
     
113.   else
     
114.   {
     
115.     temp_string[i] = '0'; ++i;
     
116.     temp_string[i] = '.'; ++i;
     
117.     n = i + (-1 - num_int_exp10);
     
118.     while(i < n)
     
119.     {
     
120.       temp_string[i] = '0'; ++i;
     
121.     }
     
122.     n = i + (num_int_exp10 - num_int_tail_exp10);
     
123.     while(i <= n)
     
124.     {
     
125.       temp_string[i] = (char)(lround(digital_character[j]) + 0x30);  //0x30 == '0'
     
126.       ++i;
     
127.       ++j;
     
128.     }
     
129.   }
     
130.   temp_string[i] = '\x0';
     
131.   n = i;
     
132.   if ((n + 1) > array_len)
     
133.   {
     
134.     return 0;
     
135.   }
     
136.   for (i=0; i <= n; ++i)
     
137.   {
     
138.     numeric_string[i] = temp_string[i];
     
139.   }
     
140.   return n;  //Returns the numeric string length
     
141. }

复制代码

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
纯C11草案标准写的
有什么使用问题欢迎留言

test01

哈哈，会贴代码了

test01

为更方便大家应用，变更了开源许可证