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10 | |
10 | |
11 | Its homepage can be found here: |
11 | Its homepage can be found here: |
12 | |
12 | |
13 | http://software.schmorp.de/pkg/libecb |
13 | http://software.schmorp.de/pkg/libecb |
14 | |
14 | |
15 | It mainly provides a number of wrappers around GCC built-ins, together |
15 | It mainly provides a number of wrappers around many compiler built-ins, |
16 | with replacement functions for other compilers. In addition to this, |
16 | together with replacement functions for other compilers. In addition |
17 | it provides a number of other lowlevel C utilities, such as endianness |
17 | to this, it provides a number of other lowlevel C utilities, such as |
18 | detection, byte swapping or bit rotations. |
18 | endianness detection, byte swapping or bit rotations. |
19 | |
19 | |
20 | Or in other words, things that should be built into any standard C system, |
20 | Or in other words, things that should be built into any standard C |
21 | but aren't, implemented as efficient as possible with GCC, and still |
21 | system, but aren't, implemented as efficient as possible with GCC (clang, |
22 | correct with other compilers. |
22 | msvc...), and still correct with other compilers. |
23 | |
23 | |
24 | More might come. |
24 | More might come. |
25 | |
25 | |
26 | =head2 ABOUT THE HEADER |
26 | =head2 ABOUT THE HEADER |
27 | |
27 | |
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58 | |
58 | |
59 | =head2 TYPES / TYPE SUPPORT |
59 | =head2 TYPES / TYPE SUPPORT |
60 | |
60 | |
61 | ecb.h makes sure that the following types are defined (in the expected way): |
61 | ecb.h makes sure that the following types are defined (in the expected way): |
62 | |
62 | |
63 | int8_t uint8_t int16_t uint16_t |
63 | int8_t uint8_ |
64 | int32_t uint32_t int64_t uint64_t |
64 | int16_t uint16_t |
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65 | int32_t uint32_ |
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66 | int64_t uint64_t |
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67 | int_fast8_t uint_fast8_t |
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68 | int_fast16_t uint_fast16_t |
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69 | int_fast32_t uint_fast32_t |
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70 | int_fast64_t uint_fast64_t |
65 | intptr_t uintptr_t |
71 | intptr_t uintptr_t |
66 | |
72 | |
67 | The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this |
73 | The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this |
68 | platform (currently C<4> or C<8>) and can be used in preprocessor |
74 | platform (currently C<4> or C<8>) and can be used in preprocessor |
69 | expressions. |
75 | expressions. |
70 | |
76 | |
71 | For C<ptrdiff_t> and C<size_t> use C<stddef.h>. |
77 | For C<ptrdiff_t> and C<size_t> use C<stddef.h>/C<cstddef>. |
72 | |
78 | |
73 | =head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS |
79 | =head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS |
74 | |
80 | |
75 | All the following symbols expand to an expression that can be tested in |
81 | All the following symbols expand to an expression that can be tested in |
76 | preprocessor instructions as well as treated as a boolean (use C<!!> to |
82 | preprocessor instructions as well as treated as a boolean (use C<!!> to |
77 | ensure it's either C<0> or C<1> if you need that). |
83 | ensure it's either C<0> or C<1> if you need that). |
78 | |
84 | |
79 | =over 4 |
85 | =over |
80 | |
86 | |
81 | =item ECB_C |
87 | =item ECB_C |
82 | |
88 | |
83 | True if the implementation defines the C<__STDC__> macro to a true value, |
89 | True if the implementation defines the C<__STDC__> macro to a true value, |
84 | while not claiming to be C++. |
90 | while not claiming to be C++, i..e C, but not C++. |
85 | |
91 | |
86 | =item ECB_C99 |
92 | =item ECB_C99 |
87 | |
93 | |
88 | True if the implementation claims to be compliant to C99 (ISO/IEC |
94 | True if the implementation claims to be compliant to C99 (ISO/IEC |
89 | 9899:1999) or any later version, while not claiming to be C++. |
95 | 9899:1999) or any later version, while not claiming to be C++. |
90 | |
96 | |
91 | Note that later versions (ECB_C11) remove core features again (for |
97 | Note that later versions (ECB_C11) remove core features again (for |
92 | example, variable length arrays). |
98 | example, variable length arrays). |
93 | |
99 | |
94 | =item ECB_C11 |
100 | =item ECB_C11, ECB_C17 |
95 | |
101 | |
96 | True if the implementation claims to be compliant to C11 (ISO/IEC |
102 | True if the implementation claims to be compliant to C11/C17 (ISO/IEC |
97 | 9899:2011) or any later version, while not claiming to be C++. |
103 | 9899:2011, :20187) or any later version, while not claiming to be C++. |
98 | |
104 | |
99 | =item ECB_CPP |
105 | =item ECB_CPP |
100 | |
106 | |
101 | True if the implementation defines the C<__cplusplus__> macro to a true |
107 | True if the implementation defines the C<__cplusplus__> macro to a true |
102 | value, which is typically true for C++ compilers. |
108 | value, which is typically true for C++ compilers. |
103 | |
109 | |
104 | =item ECB_CPP11 |
110 | =item ECB_CPP11, ECB_CPP14, ECB_CPP17 |
105 | |
111 | |
106 | True if the implementation claims to be compliant to ISO/IEC 14882:2011 |
112 | True if the implementation claims to be compliant to C++11/C++14/C++17 |
107 | (C++11) or any later version. |
113 | (ISO/IEC 14882:2011, :2014, :2017) or any later version. |
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114 | |
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115 | Note that many C++20 features will likely have their own feature test |
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116 | macros (see e.g. L<http://eel.is/c++draft/cpp.predefined#1.8>). |
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117 | |
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118 | =item ECB_OPTIMIZE_SIZE |
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119 | |
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120 | Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol |
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121 | can also be defined before including F<ecb.h>, in which case it will be |
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122 | unchanged. |
108 | |
123 | |
109 | =item ECB_GCC_VERSION (major, minor) |
124 | =item ECB_GCC_VERSION (major, minor) |
110 | |
125 | |
111 | Expands to a true value (suitable for testing in by the preprocessor) |
126 | Expands to a true value (suitable for testing by the preprocessor) if the |
112 | if the compiler used is GNU C and the version is the given version, or |
127 | compiler used is GNU C and the version is the given version, or higher. |
113 | higher. |
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114 | |
128 | |
115 | This macro tries to return false on compilers that claim to be GCC |
129 | This macro tries to return false on compilers that claim to be GCC |
116 | compatible but aren't. |
130 | compatible but aren't. |
117 | |
131 | |
118 | =item ECB_EXTERN_C |
132 | =item ECB_EXTERN_C |
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137 | |
151 | |
138 | ECB_EXTERN_C_END |
152 | ECB_EXTERN_C_END |
139 | |
153 | |
140 | =item ECB_STDFP |
154 | =item ECB_STDFP |
141 | |
155 | |
142 | If this evaluates to a true value (suitable for testing in by the |
156 | If this evaluates to a true value (suitable for testing by the |
143 | preprocessor), then C<float> and C<double> use IEEE 754 single/binary32 |
157 | preprocessor), then C<float> and C<double> use IEEE 754 single/binary32 |
144 | and double/binary64 representations internally I<and> the endianness of |
158 | and double/binary64 representations internally I<and> the endianness of |
145 | both types match the endianness of C<uint32_t> and C<uint64_t>. |
159 | both types match the endianness of C<uint32_t> and C<uint64_t>. |
146 | |
160 | |
147 | This means you can just copy the bits of a C<float> (or C<double>) to an |
161 | This means you can just copy the bits of a C<float> (or C<double>) to an |
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149 | without having to think about format or endianness. |
163 | without having to think about format or endianness. |
150 | |
164 | |
151 | This is true for basically all modern platforms, although F<ecb.h> might |
165 | This is true for basically all modern platforms, although F<ecb.h> might |
152 | not be able to deduce this correctly everywhere and might err on the safe |
166 | not be able to deduce this correctly everywhere and might err on the safe |
153 | side. |
167 | side. |
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168 | |
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169 | =item ECB_64BIT_NATIVE |
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170 | |
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171 | Evaluates to a true value (suitable for both preprocessor and C code |
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172 | testing) if 64 bit integer types on this architecture are evaluated |
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173 | "natively", that is, with similar speeds as 32 bit integerss. While 64 bit |
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174 | integer support is very common (and in fatc required by libecb), 32 bit |
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175 | cpus have to emulate operations on them, so you might want to avoid them. |
154 | |
176 | |
155 | =item ECB_AMD64, ECB_AMD64_X32 |
177 | =item ECB_AMD64, ECB_AMD64_X32 |
156 | |
178 | |
157 | These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32 |
179 | These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32 |
158 | ABI, respectively, and undefined elsewhere. |
180 | ABI, respectively, and undefined elsewhere. |
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165 | |
187 | |
166 | =back |
188 | =back |
167 | |
189 | |
168 | =head2 MACRO TRICKERY |
190 | =head2 MACRO TRICKERY |
169 | |
191 | |
170 | =over 4 |
192 | =over |
171 | |
193 | |
172 | =item ECB_CONCAT (a, b) |
194 | =item ECB_CONCAT (a, b) |
173 | |
195 | |
174 | Expands any macros in C<a> and C<b>, then concatenates the result to form |
196 | Expands any macros in C<a> and C<b>, then concatenates the result to form |
175 | a single token. This is mainly useful to form identifiers from components, |
197 | a single token. This is mainly useful to form identifiers from components, |
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186 | it. This is mainly useful to get the contents of a macro in string form, |
208 | it. This is mainly useful to get the contents of a macro in string form, |
187 | e.g.: |
209 | e.g.: |
188 | |
210 | |
189 | #define SQL_LIMIT 100 |
211 | #define SQL_LIMIT 100 |
190 | sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT)); |
212 | sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT)); |
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213 | |
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214 | =item ECB_STRINGIFY_EXPR (expr) |
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215 | |
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216 | Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it |
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217 | is a valid expression. This is useful to catch typos or cases where the |
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218 | macro isn't available: |
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219 | |
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220 | #include <errno.h> |
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221 | |
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222 | ECB_STRINGIFY (EDOM); // "33" (on my system at least) |
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223 | ECB_STRINGIFY_EXPR (EDOM); // "33" |
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224 | |
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225 | // now imagine we had a typo: |
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226 | |
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227 | ECB_STRINGIFY (EDAM); // "EDAM" |
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228 | ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined |
191 | |
229 | |
192 | =back |
230 | =back |
193 | |
231 | |
194 | =head2 ATTRIBUTES |
232 | =head2 ATTRIBUTES |
195 | |
233 | |
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200 | declarations must be put before the whole declaration: |
238 | declarations must be put before the whole declaration: |
201 | |
239 | |
202 | ecb_const int mysqrt (int a); |
240 | ecb_const int mysqrt (int a); |
203 | ecb_unused int i; |
241 | ecb_unused int i; |
204 | |
242 | |
205 | =over 4 |
243 | =over |
206 | |
244 | |
207 | =item ecb_unused |
245 | =item ecb_unused |
208 | |
246 | |
209 | Marks a function or a variable as "unused", which simply suppresses a |
247 | Marks a function or a variable as "unused", which simply suppresses a |
210 | warning by GCC when it detects it as unused. This is useful when you e.g. |
248 | warning by the compiler when it detects it as unused. This is useful when |
211 | declare a variable but do not always use it: |
249 | you e.g. declare a variable but do not always use it: |
212 | |
250 | |
213 | { |
251 | { |
214 | ecb_unused int var; |
252 | ecb_unused int var; |
215 | |
253 | |
216 | #ifdef SOMECONDITION |
254 | #ifdef SOMECONDITION |
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226 | Similar to C<ecb_unused>, but marks a function, variable or type as |
264 | Similar to C<ecb_unused>, but marks a function, variable or type as |
227 | deprecated. This makes some compilers warn when the type is used. |
265 | deprecated. This makes some compilers warn when the type is used. |
228 | |
266 | |
229 | =item ecb_deprecated_message (message) |
267 | =item ecb_deprecated_message (message) |
230 | |
268 | |
231 | Same as C<ecb_deprecated>, but if possible, supply a diagnostic that is |
269 | Same as C<ecb_deprecated>, but if possible, the specified diagnostic is |
232 | used instead of a generic depreciation message when the object is being |
270 | used instead of a generic depreciation message when the object is being |
233 | used. |
271 | used. |
234 | |
272 | |
235 | =item ecb_inline |
273 | =item ecb_inline |
236 | |
274 | |
237 | Expands either to C<static inline> or to just C<static>, if inline |
275 | Expands either to (a compiler-specific equivalent of) C<static inline> or |
238 | isn't supported. It should be used to declare functions that should be |
276 | to just C<static>, if inline isn't supported. It should be used to declare |
239 | inlined, for code size or speed reasons. |
277 | functions that should be inlined, for code size or speed reasons. |
240 | |
278 | |
241 | Example: inline this function, it surely will reduce codesize. |
279 | Example: inline this function, it surely will reduce codesize. |
242 | |
280 | |
243 | ecb_inline int |
281 | ecb_inline int |
244 | negmul (int a, int b) |
282 | negmul (int a, int b) |
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246 | return - (a * b); |
284 | return - (a * b); |
247 | } |
285 | } |
248 | |
286 | |
249 | =item ecb_noinline |
287 | =item ecb_noinline |
250 | |
288 | |
251 | Prevent a function from being inlined - it might be optimised away, but |
289 | Prevents a function from being inlined - it might be optimised away, but |
252 | not inlined into other functions. This is useful if you know your function |
290 | not inlined into other functions. This is useful if you know your function |
253 | is rarely called and large enough for inlining not to be helpful. |
291 | is rarely called and large enough for inlining not to be helpful. |
254 | |
292 | |
255 | =item ecb_noreturn |
293 | =item ecb_noreturn |
256 | |
294 | |
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384 | |
422 | |
385 | =back |
423 | =back |
386 | |
424 | |
387 | =head2 OPTIMISATION HINTS |
425 | =head2 OPTIMISATION HINTS |
388 | |
426 | |
389 | =over 4 |
427 | =over |
390 | |
428 | |
391 | =item bool ecb_is_constant (expr) |
429 | =item bool ecb_is_constant (expr) |
392 | |
430 | |
393 | Returns true iff the expression can be deduced to be a compile-time |
431 | Returns true iff the expression can be deduced to be a compile-time |
394 | constant, and false otherwise. |
432 | constant, and false otherwise. |
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473 | real_reserve_method (size); /* presumably noinline */ |
511 | real_reserve_method (size); /* presumably noinline */ |
474 | } |
512 | } |
475 | |
513 | |
476 | =item ecb_assume (cond) |
514 | =item ecb_assume (cond) |
477 | |
515 | |
478 | Try to tell the compiler that some condition is true, even if it's not |
516 | Tries to tell the compiler that some condition is true, even if it's not |
479 | obvious. |
517 | obvious. This is not a function, but a statement: it cannot be used in |
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518 | another expression. |
480 | |
519 | |
481 | This can be used to teach the compiler about invariants or other |
520 | This can be used to teach the compiler about invariants or other |
482 | conditions that might improve code generation, but which are impossible to |
521 | conditions that might improve code generation, but which are impossible to |
483 | deduce form the code itself. |
522 | deduce form the code itself. |
484 | |
523 | |
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505 | |
544 | |
506 | =item ecb_unreachable () |
545 | =item ecb_unreachable () |
507 | |
546 | |
508 | This function does nothing itself, except tell the compiler that it will |
547 | This function does nothing itself, except tell the compiler that it will |
509 | never be executed. Apart from suppressing a warning in some cases, this |
548 | never be executed. Apart from suppressing a warning in some cases, this |
510 | function can be used to implement C<ecb_assume> or similar functions. |
549 | function can be used to implement C<ecb_assume> or similar functionality. |
511 | |
550 | |
512 | =item ecb_prefetch (addr, rw, locality) |
551 | =item ecb_prefetch (addr, rw, locality) |
513 | |
552 | |
514 | Tells the compiler to try to prefetch memory at the given C<addr>ess |
553 | Tells the compiler to try to prefetch memory at the given C<addr>ess |
515 | for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of |
554 | for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of |
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517 | the data will likely be accessed very often, and values in between mean |
556 | the data will likely be accessed very often, and values in between mean |
518 | something... in between. The memory pointed to by the address does not |
557 | something... in between. The memory pointed to by the address does not |
519 | need to be accessible (it could be a null pointer for example), but C<rw> |
558 | need to be accessible (it could be a null pointer for example), but C<rw> |
520 | and C<locality> must be compile-time constants. |
559 | and C<locality> must be compile-time constants. |
521 | |
560 | |
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561 | This is a statement, not a function: you cannot use it as part of an |
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562 | expression. |
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563 | |
522 | An obvious way to use this is to prefetch some data far away, in a big |
564 | An obvious way to use this is to prefetch some data far away, in a big |
523 | array you loop over. This prefetches memory some 128 array elements later, |
565 | array you loop over. This prefetches memory some 128 array elements later, |
524 | in the hope that it will be ready when the CPU arrives at that location. |
566 | in the hope that it will be ready when the CPU arrives at that location. |
525 | |
567 | |
526 | int sum = 0; |
568 | int sum = 0; |
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… | |
547 | |
589 | |
548 | =back |
590 | =back |
549 | |
591 | |
550 | =head2 BIT FIDDLING / BIT WIZARDRY |
592 | =head2 BIT FIDDLING / BIT WIZARDRY |
551 | |
593 | |
552 | =over 4 |
594 | =over |
553 | |
595 | |
554 | =item bool ecb_big_endian () |
596 | =item bool ecb_big_endian () |
555 | |
597 | |
556 | =item bool ecb_little_endian () |
598 | =item bool ecb_little_endian () |
557 | |
599 | |
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563 | |
605 | |
564 | =item int ecb_ctz32 (uint32_t x) |
606 | =item int ecb_ctz32 (uint32_t x) |
565 | |
607 | |
566 | =item int ecb_ctz64 (uint64_t x) |
608 | =item int ecb_ctz64 (uint64_t x) |
567 | |
609 | |
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610 | =item int ecb_ctz (T x) [C++] |
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611 | |
568 | Returns the index of the least significant bit set in C<x> (or |
612 | Returns the index of the least significant bit set in C<x> (or |
569 | equivalently the number of bits set to 0 before the least significant bit |
613 | equivalently the number of bits set to 0 before the least significant bit |
570 | set), starting from 0. If C<x> is 0 the result is undefined. |
614 | set), starting from 0. If C<x> is 0 the result is undefined. |
571 | |
615 | |
572 | For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>. |
616 | For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>. |
573 | |
617 | |
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618 | The overloaded C++ C<ecb_ctz> function supports C<uint8_t>, C<uint16_t>, |
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619 | C<uint32_t> and C<uint64_t> types. |
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620 | |
574 | For example: |
621 | For example: |
575 | |
622 | |
576 | ecb_ctz32 (3) = 0 |
623 | ecb_ctz32 (3) = 0 |
577 | ecb_ctz32 (6) = 1 |
624 | ecb_ctz32 (6) = 1 |
578 | |
625 | |
579 | =item bool ecb_is_pot32 (uint32_t x) |
626 | =item bool ecb_is_pot32 (uint32_t x) |
580 | |
627 | |
581 | =item bool ecb_is_pot64 (uint32_t x) |
628 | =item bool ecb_is_pot64 (uint32_t x) |
582 | |
629 | |
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630 | =item bool ecb_is_pot (T x) [C++] |
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631 | |
583 | Return true iff C<x> is a power of two or C<x == 0>. |
632 | Returns true iff C<x> is a power of two or C<x == 0>. |
584 | |
633 | |
585 | For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>. |
634 | For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>. |
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635 | |
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636 | The overloaded C++ C<ecb_is_pot> function supports C<uint8_t>, C<uint16_t>, |
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637 | C<uint32_t> and C<uint64_t> types. |
586 | |
638 | |
587 | =item int ecb_ld32 (uint32_t x) |
639 | =item int ecb_ld32 (uint32_t x) |
588 | |
640 | |
589 | =item int ecb_ld64 (uint64_t x) |
641 | =item int ecb_ld64 (uint64_t x) |
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642 | |
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643 | =item int ecb_ld64 (T x) [C++] |
590 | |
644 | |
591 | Returns the index of the most significant bit set in C<x>, or the number |
645 | Returns the index of the most significant bit set in C<x>, or the number |
592 | of digits the number requires in binary (so that C<< 2**ld <= x < |
646 | of digits the number requires in binary (so that C<< 2**ld <= x < |
593 | 2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is |
647 | 2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is |
594 | to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for |
648 | to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for |
… | |
… | |
599 | the given data type), while C<ecb_ld> returns how many bits the number |
653 | the given data type), while C<ecb_ld> returns how many bits the number |
600 | itself requires. |
654 | itself requires. |
601 | |
655 | |
602 | For smaller types than C<uint32_t> you can safely use C<ecb_ld32>. |
656 | For smaller types than C<uint32_t> you can safely use C<ecb_ld32>. |
603 | |
657 | |
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658 | The overloaded C++ C<ecb_ld> function supports C<uint8_t>, C<uint16_t>, |
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659 | C<uint32_t> and C<uint64_t> types. |
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660 | |
604 | =item int ecb_popcount32 (uint32_t x) |
661 | =item int ecb_popcount32 (uint32_t x) |
605 | |
662 | |
606 | =item int ecb_popcount64 (uint64_t x) |
663 | =item int ecb_popcount64 (uint64_t x) |
607 | |
664 | |
|
|
665 | =item int ecb_popcount (T x) [C++] |
|
|
666 | |
608 | Returns the number of bits set to 1 in C<x>. |
667 | Returns the number of bits set to 1 in C<x>. |
609 | |
668 | |
610 | For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>. |
669 | For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>. |
|
|
670 | |
|
|
671 | The overloaded C++ C<ecb_popcount> function supports C<uint8_t>, C<uint16_t>, |
|
|
672 | C<uint32_t> and C<uint64_t> types. |
611 | |
673 | |
612 | For example: |
674 | For example: |
613 | |
675 | |
614 | ecb_popcount32 (7) = 3 |
676 | ecb_popcount32 (7) = 3 |
615 | ecb_popcount32 (255) = 8 |
677 | ecb_popcount32 (255) = 8 |
… | |
… | |
618 | |
680 | |
619 | =item uint16_t ecb_bitrev16 (uint16_t x) |
681 | =item uint16_t ecb_bitrev16 (uint16_t x) |
620 | |
682 | |
621 | =item uint32_t ecb_bitrev32 (uint32_t x) |
683 | =item uint32_t ecb_bitrev32 (uint32_t x) |
622 | |
684 | |
|
|
685 | =item T ecb_bitrev (T x) [C++] |
|
|
686 | |
623 | Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1 |
687 | Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1 |
624 | and so on. |
688 | and so on. |
625 | |
689 | |
|
|
690 | The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types. |
|
|
691 | |
626 | Example: |
692 | Example: |
627 | |
693 | |
628 | ecb_bitrev8 (0xa7) = 0xea |
694 | ecb_bitrev8 (0xa7) = 0xea |
629 | ecb_bitrev32 (0xffcc4411) = 0x882233ff |
695 | ecb_bitrev32 (0xffcc4411) = 0x882233ff |
630 | |
696 | |
|
|
697 | =item T ecb_bitrev (T x) [C++] |
|
|
698 | |
|
|
699 | Overloaded C++ bitrev function. |
|
|
700 | |
|
|
701 | C<T> must be one of C<uint8_t>, C<uint16_t> or C<uint32_t>. |
|
|
702 | |
631 | =item uint32_t ecb_bswap16 (uint32_t x) |
703 | =item uint32_t ecb_bswap16 (uint32_t x) |
632 | |
704 | |
633 | =item uint32_t ecb_bswap32 (uint32_t x) |
705 | =item uint32_t ecb_bswap32 (uint32_t x) |
634 | |
706 | |
635 | =item uint64_t ecb_bswap64 (uint64_t x) |
707 | =item uint64_t ecb_bswap64 (uint64_t x) |
|
|
708 | |
|
|
709 | =item T ecb_bswap (T x) |
636 | |
710 | |
637 | These functions return the value of the 16-bit (32-bit, 64-bit) value |
711 | These functions return the value of the 16-bit (32-bit, 64-bit) value |
638 | C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in |
712 | C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in |
639 | C<ecb_bswap32>). |
713 | C<ecb_bswap32>). |
640 | |
714 | |
|
|
715 | The overloaded C++ C<ecb_bswap> function supports C<uint8_t>, C<uint16_t>, |
|
|
716 | C<uint32_t> and C<uint64_t> types. |
|
|
717 | |
641 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
718 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
642 | |
719 | |
643 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
720 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
644 | |
721 | |
645 | =item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
722 | =item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
… | |
… | |
656 | |
733 | |
657 | These two families of functions return the value of C<x> after rotating |
734 | These two families of functions return the value of C<x> after rotating |
658 | all the bits by C<count> positions to the right (C<ecb_rotr>) or left |
735 | all the bits by C<count> positions to the right (C<ecb_rotr>) or left |
659 | (C<ecb_rotl>). |
736 | (C<ecb_rotl>). |
660 | |
737 | |
661 | Current GCC versions understand these functions and usually compile them |
738 | Current GCC/clang versions understand these functions and usually compile |
662 | to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on |
739 | them to "optimal" code (e.g. a single C<rol> or a combination of C<shld> |
663 | x86). |
740 | on x86). |
|
|
741 | |
|
|
742 | =item T ecb_rotl (T x, unsigned int count) [C++] |
|
|
743 | |
|
|
744 | =item T ecb_rotr (T x, unsigned int count) [C++] |
|
|
745 | |
|
|
746 | Overloaded C++ rotl/rotr functions. |
|
|
747 | |
|
|
748 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
|
|
749 | |
|
|
750 | =back |
|
|
751 | |
|
|
752 | =head2 HOST ENDIANNESS CONVERSION |
|
|
753 | |
|
|
754 | =over |
|
|
755 | |
|
|
756 | =item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v) |
|
|
757 | |
|
|
758 | =item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v) |
|
|
759 | |
|
|
760 | =item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v) |
|
|
761 | |
|
|
762 | =item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v) |
|
|
763 | |
|
|
764 | =item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v) |
|
|
765 | |
|
|
766 | =item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v) |
|
|
767 | |
|
|
768 | Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order. |
|
|
769 | |
|
|
770 | The naming convention is C<ecb_>(C<be>|C<le>)C<_u>C<16|32|64>C<_to_host>, |
|
|
771 | where C<be> and C<le> stand for big endian and little endian, respectively. |
|
|
772 | |
|
|
773 | =item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v) |
|
|
774 | |
|
|
775 | =item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v) |
|
|
776 | |
|
|
777 | =item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v) |
|
|
778 | |
|
|
779 | =item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v) |
|
|
780 | |
|
|
781 | =item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v) |
|
|
782 | |
|
|
783 | =item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v) |
|
|
784 | |
|
|
785 | Like above, but converts I<from> host byte order to the specified |
|
|
786 | endianness. |
|
|
787 | |
|
|
788 | =back |
|
|
789 | |
|
|
790 | In C++ the following additional template functions are supported: |
|
|
791 | |
|
|
792 | =over |
|
|
793 | |
|
|
794 | =item T ecb_be_to_host (T v) |
|
|
795 | |
|
|
796 | =item T ecb_le_to_host (T v) |
|
|
797 | |
|
|
798 | =item T ecb_host_to_be (T v) |
|
|
799 | |
|
|
800 | =item T ecb_host_to_le (T v) |
|
|
801 | |
|
|
802 | =back |
|
|
803 | |
|
|
804 | These functions work like their C counterparts, above, but use templates, |
|
|
805 | which make them useful in generic code. |
|
|
806 | |
|
|
807 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t> |
|
|
808 | (so unlike their C counterparts, there is a version for C<uint8_t>, which |
|
|
809 | again can be useful in generic code). |
|
|
810 | |
|
|
811 | =head2 UNALIGNED LOAD/STORE |
|
|
812 | |
|
|
813 | These function load or store unaligned multi-byte values. |
|
|
814 | |
|
|
815 | =over |
|
|
816 | |
|
|
817 | =item uint_fast16_t ecb_peek_u16_u (const void *ptr) |
|
|
818 | |
|
|
819 | =item uint_fast32_t ecb_peek_u32_u (const void *ptr) |
|
|
820 | |
|
|
821 | =item uint_fast64_t ecb_peek_u64_u (const void *ptr) |
|
|
822 | |
|
|
823 | These functions load an unaligned, unsigned 16, 32 or 64 bit value from |
|
|
824 | memory. |
|
|
825 | |
|
|
826 | =item uint_fast16_t ecb_peek_be_u16_u (const void *ptr) |
|
|
827 | |
|
|
828 | =item uint_fast32_t ecb_peek_be_u32_u (const void *ptr) |
|
|
829 | |
|
|
830 | =item uint_fast64_t ecb_peek_be_u64_u (const void *ptr) |
|
|
831 | |
|
|
832 | =item uint_fast16_t ecb_peek_le_u16_u (const void *ptr) |
|
|
833 | |
|
|
834 | =item uint_fast32_t ecb_peek_le_u32_u (const void *ptr) |
|
|
835 | |
|
|
836 | =item uint_fast64_t ecb_peek_le_u64_u (const void *ptr) |
|
|
837 | |
|
|
838 | Like above, but additionally convert from big endian (C<be>) or little |
|
|
839 | endian (C<le>) byte order to host byte order while doing so. |
|
|
840 | |
|
|
841 | =item ecb_poke_u16_u (void *ptr, uint16_t v) |
|
|
842 | |
|
|
843 | =item ecb_poke_u32_u (void *ptr, uint32_t v) |
|
|
844 | |
|
|
845 | =item ecb_poke_u64_u (void *ptr, uint64_t v) |
|
|
846 | |
|
|
847 | These functions store an unaligned, unsigned 16, 32 or 64 bit value to |
|
|
848 | memory. |
|
|
849 | |
|
|
850 | =item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v) |
|
|
851 | |
|
|
852 | =item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v) |
|
|
853 | |
|
|
854 | =item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v) |
|
|
855 | |
|
|
856 | =item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v) |
|
|
857 | |
|
|
858 | =item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v) |
|
|
859 | |
|
|
860 | =item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v) |
|
|
861 | |
|
|
862 | Like above, but additionally convert from host byte order to big endian |
|
|
863 | (C<be>) or little endian (C<le>) byte order while doing so. |
|
|
864 | |
|
|
865 | =back |
|
|
866 | |
|
|
867 | In C++ the following additional template functions are supported: |
|
|
868 | |
|
|
869 | =over |
|
|
870 | |
|
|
871 | =item T ecb_peek<T> (const void *ptr) |
|
|
872 | |
|
|
873 | =item T ecb_peek_be<T> (const void *ptr) |
|
|
874 | |
|
|
875 | =item T ecb_peek_le<T> (const void *ptr) |
|
|
876 | |
|
|
877 | =item T ecb_peek_u<T> (const void *ptr) |
|
|
878 | |
|
|
879 | =item T ecb_peek_be_u<T> (const void *ptr) |
|
|
880 | |
|
|
881 | =item T ecb_peek_le_u<T> (const void *ptr) |
|
|
882 | |
|
|
883 | Similarly to their C counterparts, these functions load an unsigned 8, 16, |
|
|
884 | 32 or 64 bit value from memory, with optional conversion from big/little |
|
|
885 | endian. |
|
|
886 | |
|
|
887 | Since the type cannot be deduced, it has to be specified explicitly, e.g. |
|
|
888 | |
|
|
889 | uint_fast16_t v = ecb_peek<uint16_t> (ptr); |
|
|
890 | |
|
|
891 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
|
|
892 | |
|
|
893 | Unlike their C counterparts, these functions support 8 bit quantities |
|
|
894 | (C<uint8_t>) and also have an aligned version (without the C<_u> prefix), |
|
|
895 | all of which hopefully makes them more useful in generic code. |
|
|
896 | |
|
|
897 | =item ecb_poke (void *ptr, T v) |
|
|
898 | |
|
|
899 | =item ecb_poke_be (void *ptr, T v) |
|
|
900 | |
|
|
901 | =item ecb_poke_le (void *ptr, T v) |
|
|
902 | |
|
|
903 | =item ecb_poke_u (void *ptr, T v) |
|
|
904 | |
|
|
905 | =item ecb_poke_be_u (void *ptr, T v) |
|
|
906 | |
|
|
907 | =item ecb_poke_le_u (void *ptr, T v) |
|
|
908 | |
|
|
909 | Again, similarly to their C counterparts, these functions store an |
|
|
910 | unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to |
|
|
911 | big/little endian. |
|
|
912 | |
|
|
913 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
|
|
914 | |
|
|
915 | Unlike their C counterparts, these functions support 8 bit quantities |
|
|
916 | (C<uint8_t>) and also have an aligned version (without the C<_u> prefix), |
|
|
917 | all of which hopefully makes them more useful in generic code. |
664 | |
918 | |
665 | =back |
919 | =back |
666 | |
920 | |
667 | =head2 FLOATING POINT FIDDLING |
921 | =head2 FLOATING POINT FIDDLING |
668 | |
922 | |
669 | =over 4 |
923 | =over |
670 | |
924 | |
671 | =item ECB_INFINITY |
925 | =item ECB_INFINITY [-UECB_NO_LIBM] |
672 | |
926 | |
673 | Evaluates to positive infinity if supported by the platform, otherwise to |
927 | Evaluates to positive infinity if supported by the platform, otherwise to |
674 | a truly huge number. |
928 | a truly huge number. |
675 | |
929 | |
676 | =item ECB_NON |
930 | =item ECB_NAN [-UECB_NO_LIBM] |
677 | |
931 | |
678 | Evaluates to a quiet NAN if supported by the platform, otherwise to |
932 | Evaluates to a quiet NAN if supported by the platform, otherwise to |
679 | C<ECB_INFINITY>. |
933 | C<ECB_INFINITY>. |
680 | |
934 | |
681 | =item float ecb_ldexpf (float x, int exp) |
935 | =item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM] |
682 | |
936 | |
683 | Same as C<ldexpf>, but always available. |
937 | Same as C<ldexpf>, but always available. |
684 | |
938 | |
|
|
939 | =item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM] |
|
|
940 | |
685 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
941 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
686 | |
942 | |
687 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
943 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
688 | |
944 | |
689 | These functions each take an argument in the native C<float> or C<double> |
945 | These functions each take an argument in the native C<float> or C<double> |
690 | type and return the IEEE 754 bit representation of it. |
946 | type and return the IEEE 754 bit representation of it (binary16/half, |
|
|
947 | binary32/single or binary64/double precision). |
691 | |
948 | |
692 | The bit representation is just as IEEE 754 defines it, i.e. the sign bit |
949 | The bit representation is just as IEEE 754 defines it, i.e. the sign bit |
693 | will be the most significant bit, followed by exponent and mantissa. |
950 | will be the most significant bit, followed by exponent and mantissa. |
694 | |
951 | |
695 | This function should work even when the native floating point format isn't |
952 | This function should work even when the native floating point format isn't |
… | |
… | |
699 | |
956 | |
700 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
957 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
701 | be able to optimise away this function completely. |
958 | be able to optimise away this function completely. |
702 | |
959 | |
703 | These functions can be helpful when serialising floats to the network - you |
960 | These functions can be helpful when serialising floats to the network - you |
704 | can serialise the return value like a normal uint32_t/uint64_t. |
961 | can serialise the return value like a normal uint16_t/uint32_t/uint64_t. |
705 | |
962 | |
706 | Another use for these functions is to manipulate floating point values |
963 | Another use for these functions is to manipulate floating point values |
707 | directly. |
964 | directly. |
708 | |
965 | |
709 | Silly example: toggle the sign bit of a float. |
966 | Silly example: toggle the sign bit of a float. |
… | |
… | |
716 | |
973 | |
717 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
974 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
718 | |
975 | |
719 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
976 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
720 | |
977 | |
721 | =item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM] |
978 | =item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM] |
722 | |
979 | |
723 | The reverse operation of the previous function - takes the bit |
980 | The reverse operation of the previous function - takes the bit |
724 | representation of an IEEE binary16, binary32 or binary64 number and |
981 | representation of an IEEE binary16, binary32 or binary64 number (half, |
725 | converts it to the native C<float> or C<double> format. |
982 | single or double precision) and converts it to the native C<float> or |
|
|
983 | C<double> format. |
726 | |
984 | |
727 | This function should work even when the native floating point format isn't |
985 | This function should work even when the native floating point format isn't |
728 | IEEE compliant, of course at a speed and code size penalty, and of course |
986 | IEEE compliant, of course at a speed and code size penalty, and of course |
729 | also within reasonable limits (it tries to convert normals and denormals, |
987 | also within reasonable limits (it tries to convert normals and denormals, |
730 | and might be lucky for infinities, and with extraordinary luck, also for |
988 | and might be lucky for infinities, and with extraordinary luck, also for |
731 | negative zero). |
989 | negative zero). |
732 | |
990 | |
733 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
991 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
734 | be able to optimise away this function completely. |
992 | be able to optimise away this function completely. |
735 | |
993 | |
|
|
994 | =item uint16_t ecb_binary32_to_binary16 (uint32_t x) |
|
|
995 | |
|
|
996 | =item uint32_t ecb_binary16_to_binary32 (uint16_t x) |
|
|
997 | |
|
|
998 | Convert a IEEE binary32/single precision to binary16/half format, and vice |
|
|
999 | versa, handling all details (round-to-nearest-even, subnormals, infinity |
|
|
1000 | and NaNs) correctly. |
|
|
1001 | |
|
|
1002 | These are functions are available under C<-DECB_NO_LIBM>, since |
|
|
1003 | they do not rely on the platform floating point format. The |
|
|
1004 | C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are |
|
|
1005 | usually what you want. |
|
|
1006 | |
736 | =back |
1007 | =back |
737 | |
1008 | |
738 | =head2 ARITHMETIC |
1009 | =head2 ARITHMETIC |
739 | |
1010 | |
740 | =over 4 |
1011 | =over |
741 | |
1012 | |
742 | =item x = ecb_mod (m, n) |
1013 | =item x = ecb_mod (m, n) |
743 | |
1014 | |
744 | Returns C<m> modulo C<n>, which is the same as the positive remainder |
1015 | Returns C<m> modulo C<n>, which is the same as the positive remainder |
745 | of the division operation between C<m> and C<n>, using floored |
1016 | of the division operation between C<m> and C<n>, using floored |
… | |
… | |
752 | C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be |
1023 | C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be |
753 | negatable, that is, both C<m> and C<-m> must be representable in its |
1024 | negatable, that is, both C<m> and C<-m> must be representable in its |
754 | type (this typically excludes the minimum signed integer value, the same |
1025 | type (this typically excludes the minimum signed integer value, the same |
755 | limitation as for C</> and C<%> in C). |
1026 | limitation as for C</> and C<%> in C). |
756 | |
1027 | |
757 | Current GCC versions compile this into an efficient branchless sequence on |
1028 | Current GCC/clang versions compile this into an efficient branchless |
758 | almost all CPUs. |
1029 | sequence on almost all CPUs. |
759 | |
1030 | |
760 | For example, when you want to rotate forward through the members of an |
1031 | For example, when you want to rotate forward through the members of an |
761 | array for increasing C<m> (which might be negative), then you should use |
1032 | array for increasing C<m> (which might be negative), then you should use |
762 | C<ecb_mod>, as the C<%> operator might give either negative results, or |
1033 | C<ecb_mod>, as the C<%> operator might give either negative results, or |
763 | change direction for negative values: |
1034 | change direction for negative values: |
… | |
… | |
776 | |
1047 | |
777 | =back |
1048 | =back |
778 | |
1049 | |
779 | =head2 UTILITY |
1050 | =head2 UTILITY |
780 | |
1051 | |
781 | =over 4 |
1052 | =over |
782 | |
1053 | |
783 | =item element_count = ecb_array_length (name) |
1054 | =item element_count = ecb_array_length (name) |
784 | |
1055 | |
785 | Returns the number of elements in the array C<name>. For example: |
1056 | Returns the number of elements in the array C<name>. For example: |
786 | |
1057 | |
… | |
… | |
794 | |
1065 | |
795 | =head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF |
1066 | =head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF |
796 | |
1067 | |
797 | These symbols need to be defined before including F<ecb.h> the first time. |
1068 | These symbols need to be defined before including F<ecb.h> the first time. |
798 | |
1069 | |
799 | =over 4 |
1070 | =over |
800 | |
1071 | |
801 | =item ECB_NO_THREADS |
1072 | =item ECB_NO_THREADS |
802 | |
1073 | |
803 | If F<ecb.h> is never used from multiple threads, then this symbol can |
1074 | If F<ecb.h> is never used from multiple threads, then this symbol can |
804 | be defined, in which case memory fences (and similar constructs) are |
1075 | be defined, in which case memory fences (and similar constructs) are |
… | |
… | |
820 | dependencies on the math library (usually called F<-lm>) - these are |
1091 | dependencies on the math library (usually called F<-lm>) - these are |
821 | marked with [-UECB_NO_LIBM]. |
1092 | marked with [-UECB_NO_LIBM]. |
822 | |
1093 | |
823 | =back |
1094 | =back |
824 | |
1095 | |
|
|
1096 | =head1 UNDOCUMENTED FUNCTIONALITY |
825 | |
1097 | |
|
|
1098 | F<ecb.h> is full of undocumented functionality as well, some of which is |
|
|
1099 | intended to be internal-use only, some of which we forgot to document, and |
|
|
1100 | some of which we hide because we are not sure we will keep the interface |
|
|
1101 | stable. |
|
|
1102 | |
|
|
1103 | While you are welcome to rummage around and use whatever you find useful |
|
|
1104 | (we can't stop you), keep in mind that we will change undocumented |
|
|
1105 | functionality in incompatible ways without thinking twice, while we are |
|
|
1106 | considerably more conservative with documented things. |
|
|
1107 | |
|
|
1108 | =head1 AUTHORS |
|
|
1109 | |
|
|
1110 | C<libecb> is designed and maintained by: |
|
|
1111 | |
|
|
1112 | Emanuele Giaquinta <e.giaquinta@glauco.it> |
|
|
1113 | Marc Alexander Lehmann <schmorp@schmorp.de> |
|
|
1114 | |
|
|
1115 | |