| 1 | /* |
| 2 | * Common Trace Format |
| 3 | * |
| 4 | * Floating point read/write functions. |
| 5 | * |
| 6 | * Copyright (c) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 7 | * |
| 8 | * This library is free software; you can redistribute it and/or |
| 9 | * modify it under the terms of the GNU Lesser General Public |
| 10 | * License as published by the Free Software Foundation; either |
| 11 | * version 2.1 of the License, or (at your option) any later version. |
| 12 | * |
| 13 | * This library is distributed in the hope that it will be useful, |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 16 | * Lesser General Public License for more details. |
| 17 | * |
| 18 | * You should have received a copy of the GNU Lesser General Public |
| 19 | * License along with this library; if not, write to the Free Software |
| 20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 21 | * |
| 22 | * Reference: ISO C99 standard 5.2.4 |
| 23 | */ |
| 24 | |
| 25 | #include <babeltrace/ctf/types.h> |
| 26 | #include <glib.h> |
| 27 | #include <float.h> /* C99 floating point definitions */ |
| 28 | #include <endian.h> |
| 29 | |
| 30 | /* |
| 31 | * This library is limited to binary representation of floating point values. |
| 32 | * Sign-extension of the exponents is assumed to keep the NaN, +inf, -inf |
| 33 | * values, but this should be double-checked (TODO). |
| 34 | */ |
| 35 | |
| 36 | /* |
| 37 | * Aliasing float/double and unsigned long is not strictly permitted by strict |
| 38 | * aliasing, but in practice type prunning is well supported, and this permits |
| 39 | * us to use per-word read/writes rather than per-byte. |
| 40 | */ |
| 41 | |
| 42 | #if defined(__GNUC__) || defined(__MINGW32__) || defined(_MSC_VER) |
| 43 | #define HAS_TYPE_PRUNING |
| 44 | #endif |
| 45 | |
| 46 | #if (FLT_RADIX != 2) |
| 47 | |
| 48 | #error "Unsupported floating point radix" |
| 49 | |
| 50 | #endif |
| 51 | |
| 52 | union doubleIEEE754 { |
| 53 | double v; |
| 54 | #ifdef HAS_TYPE_PRUNING |
| 55 | unsigned long bits[(sizeof(double) + sizeof(unsigned long) - 1) / sizeof(unsigned long)]; |
| 56 | #else |
| 57 | unsigned char bits[sizeof(double)]; |
| 58 | #endif |
| 59 | }; |
| 60 | |
| 61 | union ldoubleIEEE754 { |
| 62 | long double v; |
| 63 | #ifdef HAS_TYPE_PRUNING |
| 64 | unsigned long bits[(sizeof(long double) + sizeof(unsigned long) - 1) / sizeof(unsigned long)]; |
| 65 | #else |
| 66 | unsigned char bits[sizeof(long double)]; |
| 67 | #endif |
| 68 | }; |
| 69 | |
| 70 | struct pos_len { |
| 71 | size_t sign_start, exp_start, mantissa_start, len; |
| 72 | }; |
| 73 | |
| 74 | void ctf_float_copy(unsigned char *destp, const struct ctf_float *dest, |
| 75 | const unsigned char *src, const struct ctf_float *src) |
| 76 | { |
| 77 | struct pos_len destpos, srcpos; |
| 78 | union { |
| 79 | unsigned long long u; |
| 80 | long long s; |
| 81 | } tmp; |
| 82 | |
| 83 | destpos.len = dest.exp_len + dest.mantissa_len; |
| 84 | if (dest.byte_order == LITTLE_ENDIAN) { |
| 85 | destpos.sign_start = destpos.len - 1; |
| 86 | destpos.exp_start = destpos.sign_start - dest->exp_len; |
| 87 | destpos.mantissa_start = 0; |
| 88 | } else { |
| 89 | destpos.sign_start = 0; |
| 90 | destpos.exp_start = 1; |
| 91 | destpos.mantissa_start = destpos.exp_start + dest->exp_len; |
| 92 | } |
| 93 | |
| 94 | srcpos.len = src.exp_len + src.mantissa_len; |
| 95 | if (src.byte_order == LITTLE_ENDIAN) { |
| 96 | srcpos.sign_start = srcpos.len - 1; |
| 97 | srcpos.exp_start = srcpos.sign_start - src->exp_len; |
| 98 | srcpos.mantissa_start = 0; |
| 99 | } else { |
| 100 | srcpos.sign_start = 0; |
| 101 | srcpos.exp_start = 1; |
| 102 | srcpos.mantissa_start = srcpos.exp_start + src->exp_len; |
| 103 | } |
| 104 | |
| 105 | /* sign */ |
| 106 | tmp.u = ctf_bitfield_unsigned_read(ptr, srcpos.sign_start, 1, |
| 107 | src->byte_order); |
| 108 | ctf_bitfield_unsigned_write(&u.bits, destpos.sign_start, 1, |
| 109 | dest->byte_order, tmp.u); |
| 110 | |
| 111 | /* mantissa (without leading 1). No sign extend. */ |
| 112 | tmp.u = ctf_bitfield_unsigned_read(ptr, srcpos.mantissa_start, |
| 113 | src->mantissa_len - 1, |
| 114 | src->byte_order); |
| 115 | ctf_bitfield_unsigned_write(&u.bits, destpos.mantissa_start, |
| 116 | dest->mantissa_len - 1, dest->byte_order, |
| 117 | tmp.u); |
| 118 | |
| 119 | /* exponent, with sign-extend. */ |
| 120 | tmp.s = ctf_bitfield_signed_read(ptr, srcpos.exp_start, src->exp_len, |
| 121 | src->byte_order); |
| 122 | ctf_bitfield_signed_write(&u.bits, destpos.exp_start, dest->exp_len, |
| 123 | dest->byte_order, tmp.s); |
| 124 | } |
| 125 | |
| 126 | double ctf_double_read(const unsigned char *ptr, const struct ctf_float *src) |
| 127 | { |
| 128 | union doubleIEEE754 u; |
| 129 | struct ctf_float dest = { |
| 130 | .exp_len = sizeof(double) * CHAR_BIT - DBL_MANT_DIG, |
| 131 | .mantissa_len = DBL_MANT_DIG, |
| 132 | .byte_order = BYTE_ORDER, |
| 133 | }; |
| 134 | |
| 135 | ctf_float_copy(&u.bits, &dest, ptr, src); |
| 136 | return u.v; |
| 137 | } |
| 138 | |
| 139 | size_t ctf_double_write(unsigned char *ptr, const struct ctf_float *dest, |
| 140 | double v) |
| 141 | { |
| 142 | union doubleIEEE754 u; |
| 143 | struct ctf_float src = { |
| 144 | .exp_len = sizeof(double) * CHAR_BIT - DBL_MANT_DIG, |
| 145 | .mantissa_len = DBL_MANT_DIG, |
| 146 | .byte_order = BYTE_ORDER, |
| 147 | }; |
| 148 | |
| 149 | if (!ptr) |
| 150 | goto end; |
| 151 | u.v = v; |
| 152 | ctf_float_copy(ptr, dest, &u.bits, &src); |
| 153 | end: |
| 154 | return len; |
| 155 | } |
| 156 | |
| 157 | long double ctf_ldouble_read(const unsigned char *ptr, |
| 158 | const struct ctf_float *src) |
| 159 | { |
| 160 | union ldoubleIEEE754 u; |
| 161 | struct ctf_float dest = { |
| 162 | .exp_len = sizeof(double) * CHAR_BIT - LDBL_MANT_DIG, |
| 163 | .mantissa_len = LDBL_MANT_DIG, |
| 164 | .byte_order = BYTE_ORDER, |
| 165 | }; |
| 166 | |
| 167 | ctf_float_copy(&u.bits, &dest, ptr, src); |
| 168 | return u.v; |
| 169 | } |
| 170 | |
| 171 | size_t ctf_ldouble_write(unsigned char *ptr, const struct ctf_float *dest, |
| 172 | long double v) |
| 173 | { |
| 174 | union ldoubleIEEE754 u; |
| 175 | struct ctf_float src = { |
| 176 | .exp_len = sizeof(double) * CHAR_BIT - LDBL_MANT_DIG, |
| 177 | .mantissa_len = LDBL_MANT_DIG, |
| 178 | .byte_order = BYTE_ORDER, |
| 179 | }; |
| 180 | |
| 181 | if (!ptr) |
| 182 | goto end; |
| 183 | u.v = v; |
| 184 | ctf_float_copy(ptr, dest, &u.bits, &src); |
| 185 | end: |
| 186 | return len; |
| 187 | } |