1 /*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "floatRt.h"
18 #include <stdbool.h>
19
20
21 #include <stdio.h>
22
23 /*
24 * FLOAT:
25 * seeeeeee emmmmmmm mmmmmmmm mmmmmmmm
26 *
27 * s = negative
28 * e = exponent
29 * m = mantissa (with one bit removed)
30 *
31 * if (e == 0xFF)
32 * if (f) val = inf
33 * else val = nan
34 * goto valDone
35 * else if (e == 0x00)
36 * useLeadingOne = 0
37 * e = -126
38 * else
39 * e = e - 127
40 * useLeadingOne = 1
41 *
42 * val = ((useLeadingOne << 24) + m) / (2 ^ 23)
43 * val *= 2 ^ e
44 *
45 * valDone:
46 *
47 * if (s)
48 * val = -val;
49 */
50
51 #define BIT_SIGN 0x80000000UL
52 #define MANTISSA_BITS 23
53 #define EXP_SHIFT MANTISSA_BITS
54 #define EXP_ADJUST 127
55
56
57 #ifdef USE_NANOHUB_FLOAT_RUNTIME
58
floatToUint64(float f)59 uint64_t floatToUint64(float f)
60 {
61 uint32_t e, word = *(const uint32_t*)&f;
62 uint64_t ret;
63
64
65 //all negatives become zero
66 if (word & BIT_SIGN)
67 return 0;
68
69 //all values with exponent < 0 are less than one and thus become zero
70 if (word < (EXP_ADJUST << EXP_SHIFT))
71 return 0;
72
73 //standard does not say what happens to NaNs, infs & other too-large values, we return a large value as an approximation (though a zero would be equally valid)
74 if (word >= (EXP_ADJUST + 64) << EXP_SHIFT)
75 return 0xFFFFFFFFFFFFFFFFULL;
76
77 //get mantissa and the implied leading one
78 ret = (word & ((1 << MANTISSA_BITS) - 1)) | (1 << MANTISSA_BITS);
79 e = ((word >> EXP_SHIFT) - EXP_ADJUST);
80
81 //shift it by the exp
82 if (e < MANTISSA_BITS)
83 ret >>= MANTISSA_BITS - e;
84 else
85 ret <<= e - MANTISSA_BITS;
86
87 return ret;
88 }
89
floatToInt64(float f)90 int64_t floatToInt64(float f)
91 {
92 uint32_t e, word = *(const uint32_t*)&f;
93 bool neg = (word & BIT_SIGN);
94 uint64_t ret;
95
96
97 //all negatives become positive for now
98 word &=~ BIT_SIGN;
99
100 //all values with exponent < 0 are less than one and thus become zero
101 if (word < (EXP_ADJUST << EXP_SHIFT))
102 return 0;
103
104 //standard does not say what happens to NaNs, infs & other too-large values, we return a large value as an approximation (though a zero would be equally valid)
105 if (word >= (EXP_ADJUST + 63) << EXP_SHIFT)
106 ret = 0x7FFFFFFFFFFFFFFFULL;
107
108 else {
109 //get mantissa and the implied leading one
110 ret = (word & ((1 << MANTISSA_BITS) - 1)) | (1 << MANTISSA_BITS);
111 e = ((word >> EXP_SHIFT) - EXP_ADJUST);
112
113 //shift it by the exp
114 if (e < MANTISSA_BITS)
115 ret >>= MANTISSA_BITS - e;
116 else
117 ret <<= e - MANTISSA_BITS;
118 }
119
120 if (neg)
121 ret = -ret;
122
123 return ret;
124 }
125
floatFromUint64(uint64_t v)126 float floatFromUint64(uint64_t v)
127 {
128 uint32_t hi = v >> 32, lo = v;
129
130 if (!hi) //this is very fast for cases where we fit into a uint32_t
131 return(float)lo;
132 else {
133 return ((float)hi) * 4294967296.0f + (float)lo;
134 }
135 }
136
floatFromInt64(int64_t v)137 float floatFromInt64(int64_t v)
138 {
139 uint32_t hi = ((uint64_t)v) >> 32, lo = v;
140
141 if ((hi == 0x00000000 && !(lo >> 31)) || (hi == 0xffffffff && (lo >> 31))) //this complex test is a lot faster then the simpler ((v >> 33) == -1 || (v >> 33) == 0)
142 return (float)(int32_t)lo;
143 else if (hi >> 31) //the case of 0x8000000000000000 is handled here, as negated it remains the same
144 return -floatFromUint64(-v);
145 else
146 return floatFromUint64(v);
147 }
148
149
150
151
152
153 #endif // USE_NANOHUB_FLOAT_RUNTIME
154