… | |
… | |
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 |
|
|
65 | int32_t uint32_ |
|
|
66 | int64_t uint64_t |
|
|
67 | int_fast8_t uint_fast8_t |
|
|
68 | int_fast16_t uint_fast16_t |
|
|
69 | int_fast32_t uint_fast32_t |
|
|
70 | int_fast64_t uint_fast64_t |
65 | intptr_t uintptr_t ptrdiff_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 | |
|
|
77 | For C<ptrdiff_t> and C<size_t> use C<stddef.h>/C<cstddef>. |
|
|
78 | |
71 | =head2 LANGUAGE/COMPILER VERSIONS |
79 | =head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS |
72 | |
80 | |
73 | 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 |
74 | 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 |
75 | 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). |
76 | |
84 | |
77 | =over 4 |
85 | =over 4 |
78 | |
86 | |
79 | =item ECB_C |
87 | =item ECB_C |
80 | |
88 | |
81 | 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, |
82 | which is typically true for both C and C++ compilers. |
90 | while not claiming to be C++. |
83 | |
91 | |
84 | =item ECB_C99 |
92 | =item ECB_C99 |
85 | |
93 | |
86 | True if the implementation claims to be C99 compliant. |
94 | True if the implementation claims to be compliant to C99 (ISO/IEC |
|
|
95 | 9899:1999) or any later version, while not claiming to be C++. |
87 | |
96 | |
88 | =item ECB_C11 |
97 | Note that later versions (ECB_C11) remove core features again (for |
|
|
98 | example, variable length arrays). |
89 | |
99 | |
|
|
100 | =item ECB_C11, ECB_C17 |
|
|
101 | |
90 | True if the implementation claims to be C11 compliant. |
102 | True if the implementation claims to be compliant to C11/C17 (ISO/IEC |
|
|
103 | 9899:2011, :20187) or any later version, while not claiming to be C++. |
91 | |
104 | |
92 | =item ECB_CPP |
105 | =item ECB_CPP |
93 | |
106 | |
94 | 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 |
95 | value, which is typically true for C++ compilers. |
108 | value, which is typically true for C++ compilers. |
96 | |
109 | |
97 | =item ECB_CPP98 |
110 | =item ECB_CPP11, ECB_CPP14, ECB_CPP17 |
98 | |
111 | |
99 | True if the implementation claims to be compliant to ISO/IEC 14882:1998 |
112 | True if the implementation claims to be compliant to C++11/C++14/C++17 |
100 | (the first C++ ISO standard) or any later version. Typically true for all |
113 | (ISO/IEC 14882:2011, :2014, :2017) or any later version. |
101 | C++ compilers. |
|
|
102 | |
114 | |
103 | =item ECB_CPP11 |
|
|
104 | |
|
|
105 | True if the implementation claims to be compliant to ISO/IEC 14882:2011 |
|
|
106 | (C++11) or any later version. |
|
|
107 | |
|
|
108 | =item ECB_GCC_VERSION(major,minor) |
115 | =item ECB_GCC_VERSION (major, minor) |
109 | |
116 | |
110 | Expands to a true value (suitable for testing in by the preprocessor) |
117 | Expands to a true value (suitable for testing in by the preprocessor) |
111 | if the compiler used is GNU C and the version is the given version, or |
118 | if the compiler used is GNU C and the version is the given version, or |
112 | higher. |
119 | higher. |
113 | |
120 | |
114 | This macro tries to return false on compilers that claim to be GCC |
121 | This macro tries to return false on compilers that claim to be GCC |
115 | compatible but aren't. |
122 | compatible but aren't. |
116 | |
123 | |
117 | =back |
124 | =item ECB_EXTERN_C |
118 | |
125 | |
|
|
126 | Expands to C<extern "C"> in C++, and a simple C<extern> in C. |
|
|
127 | |
|
|
128 | This can be used to declare a single external C function: |
|
|
129 | |
|
|
130 | ECB_EXTERN_C int printf (const char *format, ...); |
|
|
131 | |
|
|
132 | =item ECB_EXTERN_C_BEG / ECB_EXTERN_C_END |
|
|
133 | |
|
|
134 | These two macros can be used to wrap multiple C<extern "C"> definitions - |
|
|
135 | they expand to nothing in C. |
|
|
136 | |
|
|
137 | They are most useful in header files: |
|
|
138 | |
|
|
139 | ECB_EXTERN_C_BEG |
|
|
140 | |
|
|
141 | int mycfun1 (int x); |
|
|
142 | int mycfun2 (int x); |
|
|
143 | |
|
|
144 | ECB_EXTERN_C_END |
|
|
145 | |
|
|
146 | =item ECB_STDFP |
|
|
147 | |
|
|
148 | If this evaluates to a true value (suitable for testing in by the |
|
|
149 | preprocessor), then C<float> and C<double> use IEEE 754 single/binary32 |
|
|
150 | and double/binary64 representations internally I<and> the endianness of |
|
|
151 | both types match the endianness of C<uint32_t> and C<uint64_t>. |
|
|
152 | |
|
|
153 | This means you can just copy the bits of a C<float> (or C<double>) to an |
|
|
154 | C<uint32_t> (or C<uint64_t>) and get the raw IEEE 754 bit representation |
|
|
155 | without having to think about format or endianness. |
|
|
156 | |
|
|
157 | This is true for basically all modern platforms, although F<ecb.h> might |
|
|
158 | not be able to deduce this correctly everywhere and might err on the safe |
|
|
159 | side. |
|
|
160 | |
|
|
161 | =item ECB_AMD64, ECB_AMD64_X32 |
|
|
162 | |
|
|
163 | These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32 |
|
|
164 | ABI, respectively, and undefined elsewhere. |
|
|
165 | |
|
|
166 | The designers of the new X32 ABI for some inexplicable reason decided to |
|
|
167 | make it look exactly like amd64, even though it's completely incompatible |
|
|
168 | to that ABI, breaking about every piece of software that assumed that |
|
|
169 | C<__x86_64> stands for, well, the x86-64 ABI, making these macros |
|
|
170 | necessary. |
|
|
171 | |
|
|
172 | =back |
|
|
173 | |
|
|
174 | =head2 MACRO TRICKERY |
|
|
175 | |
|
|
176 | =over 4 |
|
|
177 | |
|
|
178 | =item ECB_CONCAT (a, b) |
|
|
179 | |
|
|
180 | Expands any macros in C<a> and C<b>, then concatenates the result to form |
|
|
181 | a single token. This is mainly useful to form identifiers from components, |
|
|
182 | e.g.: |
|
|
183 | |
|
|
184 | #define S1 str |
|
|
185 | #define S2 cpy |
|
|
186 | |
|
|
187 | ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src); |
|
|
188 | |
|
|
189 | =item ECB_STRINGIFY (arg) |
|
|
190 | |
|
|
191 | Expands any macros in C<arg> and returns the stringified version of |
|
|
192 | it. This is mainly useful to get the contents of a macro in string form, |
|
|
193 | e.g.: |
|
|
194 | |
|
|
195 | #define SQL_LIMIT 100 |
|
|
196 | sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT)); |
|
|
197 | |
|
|
198 | =item ECB_STRINGIFY_EXPR (expr) |
|
|
199 | |
|
|
200 | Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it |
|
|
201 | is a valid expression. This is useful to catch typos or cases where the |
|
|
202 | macro isn't available: |
|
|
203 | |
|
|
204 | #include <errno.h> |
|
|
205 | |
|
|
206 | ECB_STRINGIFY (EDOM); // "33" (on my system at least) |
|
|
207 | ECB_STRINGIFY_EXPR (EDOM); // "33" |
|
|
208 | |
|
|
209 | // now imagine we had a typo: |
|
|
210 | |
|
|
211 | ECB_STRINGIFY (EDAM); // "EDAM" |
|
|
212 | ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined |
|
|
213 | |
|
|
214 | =back |
|
|
215 | |
119 | =head2 GCC ATTRIBUTES |
216 | =head2 ATTRIBUTES |
120 | |
217 | |
121 | A major part of libecb deals with GCC attributes. These are additional |
218 | A major part of libecb deals with additional attributes that can be |
122 | attributes that you can assign to functions, variables and sometimes even |
219 | assigned to functions, variables and sometimes even types - much like |
123 | types - much like C<const> or C<volatile> in C. |
220 | C<const> or C<volatile> in C. They are implemented using either GCC |
124 | |
221 | attributes or other compiler/language specific features. Attributes |
125 | While GCC allows declarations to show up in many surprising places, |
|
|
126 | but not in many expected places, the safest way is to put attribute |
|
|
127 | declarations before the whole declaration: |
222 | declarations must be put before the whole declaration: |
128 | |
223 | |
129 | ecb_const int mysqrt (int a); |
224 | ecb_const int mysqrt (int a); |
130 | ecb_unused int i; |
225 | ecb_unused int i; |
131 | |
226 | |
132 | For variables, it is often nicer to put the attribute after the name, and |
|
|
133 | avoid multiple declarations using commas: |
|
|
134 | |
|
|
135 | int i ecb_unused; |
|
|
136 | |
|
|
137 | =over 4 |
227 | =over 4 |
138 | |
|
|
139 | =item ecb_attribute ((attrs...)) |
|
|
140 | |
|
|
141 | A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to |
|
|
142 | nothing on other compilers, so the effect is that only GCC sees these. |
|
|
143 | |
|
|
144 | Example: use the C<deprecated> attribute on a function. |
|
|
145 | |
|
|
146 | ecb_attribute((__deprecated__)) void |
|
|
147 | do_not_use_me_anymore (void); |
|
|
148 | |
228 | |
149 | =item ecb_unused |
229 | =item ecb_unused |
150 | |
230 | |
151 | Marks a function or a variable as "unused", which simply suppresses a |
231 | Marks a function or a variable as "unused", which simply suppresses a |
152 | warning by GCC when it detects it as unused. This is useful when you e.g. |
232 | warning by GCC when it detects it as unused. This is useful when you e.g. |
153 | declare a variable but do not always use it: |
233 | declare a variable but do not always use it: |
154 | |
234 | |
155 | { |
235 | { |
156 | int var ecb_unused; |
236 | ecb_unused int var; |
157 | |
237 | |
158 | #ifdef SOMECONDITION |
238 | #ifdef SOMECONDITION |
159 | var = ...; |
239 | var = ...; |
160 | return var; |
240 | return var; |
161 | #else |
241 | #else |
162 | return 0; |
242 | return 0; |
163 | #endif |
243 | #endif |
164 | } |
244 | } |
165 | |
245 | |
|
|
246 | =item ecb_deprecated |
|
|
247 | |
|
|
248 | Similar to C<ecb_unused>, but marks a function, variable or type as |
|
|
249 | deprecated. This makes some compilers warn when the type is used. |
|
|
250 | |
|
|
251 | =item ecb_deprecated_message (message) |
|
|
252 | |
|
|
253 | Same as C<ecb_deprecated>, but if possible, the specified diagnostic is |
|
|
254 | used instead of a generic depreciation message when the object is being |
|
|
255 | used. |
|
|
256 | |
166 | =item ecb_inline |
257 | =item ecb_inline |
167 | |
258 | |
168 | This is not actually an attribute, but you use it like one. It expands |
259 | Expands either to (a compiler-specific equivalent of) C<static inline> or |
169 | either to C<static inline> or to just C<static>, if inline isn't |
260 | to just C<static>, if inline isn't supported. It should be used to declare |
170 | supported. It should be used to declare functions that should be inlined, |
261 | functions that should be inlined, for code size or speed reasons. |
171 | for code size or speed reasons. |
|
|
172 | |
262 | |
173 | Example: inline this function, it surely will reduce codesize. |
263 | Example: inline this function, it surely will reduce codesize. |
174 | |
264 | |
175 | ecb_inline int |
265 | ecb_inline int |
176 | negmul (int a, int b) |
266 | negmul (int a, int b) |
… | |
… | |
178 | return - (a * b); |
268 | return - (a * b); |
179 | } |
269 | } |
180 | |
270 | |
181 | =item ecb_noinline |
271 | =item ecb_noinline |
182 | |
272 | |
183 | Prevent a function from being inlined - it might be optimised away, but |
273 | Prevents a function from being inlined - it might be optimised away, but |
184 | not inlined into other functions. This is useful if you know your function |
274 | not inlined into other functions. This is useful if you know your function |
185 | is rarely called and large enough for inlining not to be helpful. |
275 | is rarely called and large enough for inlining not to be helpful. |
186 | |
276 | |
187 | =item ecb_noreturn |
277 | =item ecb_noreturn |
188 | |
278 | |
… | |
… | |
198 | } |
288 | } |
199 | |
289 | |
200 | In this case, the compiler would probably be smart enough to deduce it on |
290 | In this case, the compiler would probably be smart enough to deduce it on |
201 | its own, so this is mainly useful for declarations. |
291 | its own, so this is mainly useful for declarations. |
202 | |
292 | |
|
|
293 | =item ecb_restrict |
|
|
294 | |
|
|
295 | Expands to the C<restrict> keyword or equivalent on compilers that support |
|
|
296 | them, and to nothing on others. Must be specified on a pointer type or |
|
|
297 | an array index to indicate that the memory doesn't alias with any other |
|
|
298 | restricted pointer in the same scope. |
|
|
299 | |
|
|
300 | Example: multiply a vector, and allow the compiler to parallelise the |
|
|
301 | loop, because it knows it doesn't overwrite input values. |
|
|
302 | |
|
|
303 | void |
|
|
304 | multiply (ecb_restrict float *src, |
|
|
305 | ecb_restrict float *dst, |
|
|
306 | int len, float factor) |
|
|
307 | { |
|
|
308 | int i; |
|
|
309 | |
|
|
310 | for (i = 0; i < len; ++i) |
|
|
311 | dst [i] = src [i] * factor; |
|
|
312 | } |
|
|
313 | |
203 | =item ecb_const |
314 | =item ecb_const |
204 | |
315 | |
205 | Declares that the function only depends on the values of its arguments, |
316 | Declares that the function only depends on the values of its arguments, |
206 | much like a mathematical function. It specifically does not read or write |
317 | much like a mathematical function. It specifically does not read or write |
207 | any memory any arguments might point to, global variables, or call any |
318 | any memory any arguments might point to, global variables, or call any |
… | |
… | |
267 | functions only called in exceptional or rare cases. |
378 | functions only called in exceptional or rare cases. |
268 | |
379 | |
269 | =item ecb_artificial |
380 | =item ecb_artificial |
270 | |
381 | |
271 | Declares the function as "artificial", in this case meaning that this |
382 | Declares the function as "artificial", in this case meaning that this |
272 | function is not really mean to be a function, but more like an accessor |
383 | function is not really meant to be a function, but more like an accessor |
273 | - many methods in C++ classes are mere accessor functions, and having a |
384 | - many methods in C++ classes are mere accessor functions, and having a |
274 | crash reported in such a method, or single-stepping through them, is not |
385 | crash reported in such a method, or single-stepping through them, is not |
275 | usually so helpful, especially when it's inlined to just a few instructions. |
386 | usually so helpful, especially when it's inlined to just a few instructions. |
276 | |
387 | |
277 | Marking them as artificial will instruct the debugger about just this, |
388 | Marking them as artificial will instruct the debugger about just this, |
… | |
… | |
297 | |
408 | |
298 | =head2 OPTIMISATION HINTS |
409 | =head2 OPTIMISATION HINTS |
299 | |
410 | |
300 | =over 4 |
411 | =over 4 |
301 | |
412 | |
|
|
413 | =item ECB_OPTIMIZE_SIZE |
|
|
414 | |
|
|
415 | Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol |
|
|
416 | can also be defined before including F<ecb.h>, in which case it will be |
|
|
417 | unchanged. |
|
|
418 | |
302 | =item bool ecb_is_constant(expr) |
419 | =item bool ecb_is_constant (expr) |
303 | |
420 | |
304 | Returns true iff the expression can be deduced to be a compile-time |
421 | Returns true iff the expression can be deduced to be a compile-time |
305 | constant, and false otherwise. |
422 | constant, and false otherwise. |
306 | |
423 | |
307 | For example, when you have a C<rndm16> function that returns a 16 bit |
424 | For example, when you have a C<rndm16> function that returns a 16 bit |
… | |
… | |
325 | return is_constant (n) && !(n & (n - 1)) |
442 | return is_constant (n) && !(n & (n - 1)) |
326 | ? rndm16 () & (num - 1) |
443 | ? rndm16 () & (num - 1) |
327 | : (n * (uint32_t)rndm16 ()) >> 16; |
444 | : (n * (uint32_t)rndm16 ()) >> 16; |
328 | } |
445 | } |
329 | |
446 | |
330 | =item bool ecb_expect (expr, value) |
447 | =item ecb_expect (expr, value) |
331 | |
448 | |
332 | Evaluates C<expr> and returns it. In addition, it tells the compiler that |
449 | Evaluates C<expr> and returns it. In addition, it tells the compiler that |
333 | the C<expr> evaluates to C<value> a lot, which can be used for static |
450 | the C<expr> evaluates to C<value> a lot, which can be used for static |
334 | branch optimisations. |
451 | branch optimisations. |
335 | |
452 | |
… | |
… | |
382 | { |
499 | { |
383 | if (ecb_expect_false (current + size > end)) |
500 | if (ecb_expect_false (current + size > end)) |
384 | real_reserve_method (size); /* presumably noinline */ |
501 | real_reserve_method (size); /* presumably noinline */ |
385 | } |
502 | } |
386 | |
503 | |
387 | =item bool ecb_assume (cond) |
504 | =item ecb_assume (cond) |
388 | |
505 | |
389 | Try to tell the compiler that some condition is true, even if it's not |
506 | Tries to tell the compiler that some condition is true, even if it's not |
390 | obvious. |
507 | obvious. This is not a function, but a statement: it cannot be used in |
|
|
508 | another expression. |
391 | |
509 | |
392 | This can be used to teach the compiler about invariants or other |
510 | This can be used to teach the compiler about invariants or other |
393 | conditions that might improve code generation, but which are impossible to |
511 | conditions that might improve code generation, but which are impossible to |
394 | deduce form the code itself. |
512 | deduce form the code itself. |
395 | |
513 | |
… | |
… | |
412 | |
530 | |
413 | Then the compiler I<might> be able to optimise out the second call |
531 | Then the compiler I<might> be able to optimise out the second call |
414 | completely, as it knows that C<< current + 1 > end >> is false and the |
532 | completely, as it knows that C<< current + 1 > end >> is false and the |
415 | call will never be executed. |
533 | call will never be executed. |
416 | |
534 | |
417 | =item bool ecb_unreachable () |
535 | =item ecb_unreachable () |
418 | |
536 | |
419 | This function does nothing itself, except tell the compiler that it will |
537 | This function does nothing itself, except tell the compiler that it will |
420 | never be executed. Apart from suppressing a warning in some cases, this |
538 | never be executed. Apart from suppressing a warning in some cases, this |
421 | function can be used to implement C<ecb_assume> or similar functions. |
539 | function can be used to implement C<ecb_assume> or similar functionality. |
422 | |
540 | |
423 | =item bool ecb_prefetch (addr, rw, locality) |
541 | =item ecb_prefetch (addr, rw, locality) |
424 | |
542 | |
425 | Tells the compiler to try to prefetch memory at the given C<addr>ess |
543 | Tells the compiler to try to prefetch memory at the given C<addr>ess |
426 | for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of |
544 | for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of |
427 | C<0> means that there will only be one access later, C<3> means that |
545 | C<0> means that there will only be one access later, C<3> means that |
428 | the data will likely be accessed very often, and values in between mean |
546 | the data will likely be accessed very often, and values in between mean |
429 | something... in between. The memory pointed to by the address does not |
547 | something... in between. The memory pointed to by the address does not |
430 | need to be accessible (it could be a null pointer for example), but C<rw> |
548 | need to be accessible (it could be a null pointer for example), but C<rw> |
431 | and C<locality> must be compile-time constants. |
549 | and C<locality> must be compile-time constants. |
432 | |
550 | |
|
|
551 | This is a statement, not a function: you cannot use it as part of an |
|
|
552 | expression. |
|
|
553 | |
433 | An obvious way to use this is to prefetch some data far away, in a big |
554 | An obvious way to use this is to prefetch some data far away, in a big |
434 | array you loop over. This prefetches memory some 128 array elements later, |
555 | array you loop over. This prefetches memory some 128 array elements later, |
435 | in the hope that it will be ready when the CPU arrives at that location. |
556 | in the hope that it will be ready when the CPU arrives at that location. |
436 | |
557 | |
437 | int sum = 0; |
558 | int sum = 0; |
… | |
… | |
489 | |
610 | |
490 | =item bool ecb_is_pot32 (uint32_t x) |
611 | =item bool ecb_is_pot32 (uint32_t x) |
491 | |
612 | |
492 | =item bool ecb_is_pot64 (uint32_t x) |
613 | =item bool ecb_is_pot64 (uint32_t x) |
493 | |
614 | |
494 | Return true iff C<x> is a power of two or C<x == 0>. |
615 | Returns true iff C<x> is a power of two or C<x == 0>. |
495 | |
616 | |
496 | For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>. |
617 | For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>. |
497 | |
618 | |
498 | =item int ecb_ld32 (uint32_t x) |
619 | =item int ecb_ld32 (uint32_t x) |
499 | |
620 | |
500 | =item int ecb_ld64 (uint64_t x) |
621 | =item int ecb_ld64 (uint64_t x) |
501 | |
622 | |
… | |
… | |
547 | |
668 | |
548 | These functions return the value of the 16-bit (32-bit, 64-bit) value |
669 | These functions return the value of the 16-bit (32-bit, 64-bit) value |
549 | C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in |
670 | C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in |
550 | C<ecb_bswap32>). |
671 | C<ecb_bswap32>). |
551 | |
672 | |
|
|
673 | =item T ecb_bswap (T x) [C++] |
|
|
674 | |
|
|
675 | For C++, an additional generic bswap function is provided. It supports |
|
|
676 | C<uint8_t>, C<uint16_t>, C<uint32_t> and C<uint64_t>. |
|
|
677 | |
552 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
678 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
553 | |
679 | |
554 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
680 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
555 | |
681 | |
556 | =item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
682 | =item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
… | |
… | |
570 | (C<ecb_rotl>). |
696 | (C<ecb_rotl>). |
571 | |
697 | |
572 | Current GCC versions understand these functions and usually compile them |
698 | Current GCC versions understand these functions and usually compile them |
573 | to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on |
699 | to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on |
574 | x86). |
700 | x86). |
|
|
701 | |
|
|
702 | =back |
|
|
703 | |
|
|
704 | =head2 HOST ENDIANNESS CONVERSION |
|
|
705 | |
|
|
706 | =over 4 |
|
|
707 | |
|
|
708 | =item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v) |
|
|
709 | |
|
|
710 | =item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v) |
|
|
711 | |
|
|
712 | =item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v) |
|
|
713 | |
|
|
714 | =item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v) |
|
|
715 | |
|
|
716 | =item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v) |
|
|
717 | |
|
|
718 | =item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v) |
|
|
719 | |
|
|
720 | Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order. |
|
|
721 | |
|
|
722 | The naming convention is C<ecb_>(C<be>|C<le>)C<_u>C<16|32|64>C<_to_host>, |
|
|
723 | where be and le stand for big endian and little endian, respectively. |
|
|
724 | |
|
|
725 | =item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v) |
|
|
726 | |
|
|
727 | =item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v) |
|
|
728 | |
|
|
729 | =item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v) |
|
|
730 | |
|
|
731 | =item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v) |
|
|
732 | |
|
|
733 | =item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v) |
|
|
734 | |
|
|
735 | =item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v) |
|
|
736 | |
|
|
737 | Like above, but converts I<from> host byte order to the specified |
|
|
738 | endianness. |
|
|
739 | |
|
|
740 | =back |
|
|
741 | |
|
|
742 | In C++ the following additional functions are supported: |
|
|
743 | |
|
|
744 | =over 4 |
|
|
745 | |
|
|
746 | =item T ecb_be_to_host (T v) |
|
|
747 | |
|
|
748 | =item T ecb_le_to_host (T v) |
|
|
749 | |
|
|
750 | =item T ecb_host_to_be (T v) |
|
|
751 | |
|
|
752 | =item T ecb_host_to_le (T v) |
|
|
753 | |
|
|
754 | These work like their C counterparts, above, but use templates for the |
|
|
755 | type, which make them useful in generic code. |
|
|
756 | |
|
|
757 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t> |
|
|
758 | (so unlike their C counterparts, there is a version for C<uint8_t>, which |
|
|
759 | again can be useful in generic code). |
|
|
760 | |
|
|
761 | =head2 UNALIGNED LOAD/STORE |
|
|
762 | |
|
|
763 | These function load or store unaligned multi-byte values. |
|
|
764 | |
|
|
765 | =over 4 |
|
|
766 | |
|
|
767 | =item uint_fast16_t ecb_peek_u16_u (const void *ptr) |
|
|
768 | |
|
|
769 | =item uint_fast32_t ecb_peek_u32_u (const void *ptr) |
|
|
770 | |
|
|
771 | =item uint_fast64_t ecb_peek_u64_u (const void *ptr) |
|
|
772 | |
|
|
773 | These functions load an unaligned, unsigned 16, 32 or 64 bit value from |
|
|
774 | memory. |
|
|
775 | |
|
|
776 | =item uint_fast16_t ecb_peek_be_u16_u (const void *ptr) |
|
|
777 | |
|
|
778 | =item uint_fast32_t ecb_peek_be_u32_u (const void *ptr) |
|
|
779 | |
|
|
780 | =item uint_fast64_t ecb_peek_be_u64_u (const void *ptr) |
|
|
781 | |
|
|
782 | =item uint_fast16_t ecb_peek_le_u16_u (const void *ptr) |
|
|
783 | |
|
|
784 | =item uint_fast32_t ecb_peek_le_u32_u (const void *ptr) |
|
|
785 | |
|
|
786 | =item uint_fast64_t ecb_peek_le_u64_u (const void *ptr) |
|
|
787 | |
|
|
788 | Like above, but additionally convert from big endian (C<be>) or little |
|
|
789 | endian (C<le>) byte order to host byte order while doing so. |
|
|
790 | |
|
|
791 | =item ecb_poke_u16_u (void *ptr, uint16_t v) |
|
|
792 | |
|
|
793 | =item ecb_poke_u32_u (void *ptr, uint32_t v) |
|
|
794 | |
|
|
795 | =item ecb_poke_u64_u (void *ptr, uint64_t v) |
|
|
796 | |
|
|
797 | These functions store an unaligned, unsigned 16, 32 or 64 bit value to |
|
|
798 | memory. |
|
|
799 | |
|
|
800 | =item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v) |
|
|
801 | |
|
|
802 | =item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v) |
|
|
803 | |
|
|
804 | =item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v) |
|
|
805 | |
|
|
806 | =item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v) |
|
|
807 | |
|
|
808 | =item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v) |
|
|
809 | |
|
|
810 | =item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v) |
|
|
811 | |
|
|
812 | Like above, but additionally convert from host byte order to big endian |
|
|
813 | (C<be>) or little endian (C<le>) byte order while doing so. |
|
|
814 | |
|
|
815 | =back |
|
|
816 | |
|
|
817 | In C++ the following additional functions are supported: |
|
|
818 | |
|
|
819 | =over 4 |
|
|
820 | |
|
|
821 | =item T ecb_peek (const void *ptr) |
|
|
822 | |
|
|
823 | =item T ecb_peek_be (const void *ptr) |
|
|
824 | |
|
|
825 | =item T ecb_peek_le (const void *ptr) |
|
|
826 | |
|
|
827 | =item T ecb_peek_u (const void *ptr) |
|
|
828 | |
|
|
829 | =item T ecb_peek_be_u (const void *ptr) |
|
|
830 | |
|
|
831 | =item T ecb_peek_le_u (const void *ptr) |
|
|
832 | |
|
|
833 | Similarly to their C counterparts, these functions load an unsigned 8, 16, |
|
|
834 | 32 or 64 bit value from memory, with optional conversion from big/little |
|
|
835 | endian. |
|
|
836 | |
|
|
837 | Since the type cannot be deduced, it has top be specified explicitly, e.g. |
|
|
838 | |
|
|
839 | uint_fast16_t v = ecb_peek<uint16_t> (ptr); |
|
|
840 | |
|
|
841 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
|
|
842 | |
|
|
843 | Unlike their C counterparts, these functions support 8 bit quantities |
|
|
844 | (C<uint8_t>) and also have an aligned version (without the C<_u> prefix), |
|
|
845 | all of which hopefully makes them more useful in generic code. |
|
|
846 | |
|
|
847 | =item ecb_poke (void *ptr, T v) |
|
|
848 | |
|
|
849 | =item ecb_poke_be (void *ptr, T v) |
|
|
850 | |
|
|
851 | =item ecb_poke_le (void *ptr, T v) |
|
|
852 | |
|
|
853 | =item ecb_poke_u (void *ptr, T v) |
|
|
854 | |
|
|
855 | =item ecb_poke_be_u (void *ptr, T v) |
|
|
856 | |
|
|
857 | =item ecb_poke_le_u (void *ptr, T v) |
|
|
858 | |
|
|
859 | Again, similarly to their C counterparts, these functions store an |
|
|
860 | unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to |
|
|
861 | big/little endian. |
|
|
862 | |
|
|
863 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
|
|
864 | |
|
|
865 | Unlike their C counterparts, these functions support 8 bit quantities |
|
|
866 | (C<uint8_t>) and also have an aligned version (without the C<_u> prefix), |
|
|
867 | all of which hopefully makes them more useful in generic code. |
|
|
868 | |
|
|
869 | =back |
|
|
870 | |
|
|
871 | =head2 FLOATING POINT FIDDLING |
|
|
872 | |
|
|
873 | =over 4 |
|
|
874 | |
|
|
875 | =item ECB_INFINITY [-UECB_NO_LIBM] |
|
|
876 | |
|
|
877 | Evaluates to positive infinity if supported by the platform, otherwise to |
|
|
878 | a truly huge number. |
|
|
879 | |
|
|
880 | =item ECB_NAN [-UECB_NO_LIBM] |
|
|
881 | |
|
|
882 | Evaluates to a quiet NAN if supported by the platform, otherwise to |
|
|
883 | C<ECB_INFINITY>. |
|
|
884 | |
|
|
885 | =item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM] |
|
|
886 | |
|
|
887 | Same as C<ldexpf>, but always available. |
|
|
888 | |
|
|
889 | =item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM] |
|
|
890 | |
|
|
891 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
|
|
892 | |
|
|
893 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
|
|
894 | |
|
|
895 | These functions each take an argument in the native C<float> or C<double> |
|
|
896 | type and return the IEEE 754 bit representation of it (binary16/half, |
|
|
897 | binary32/single or binary64/double precision). |
|
|
898 | |
|
|
899 | The bit representation is just as IEEE 754 defines it, i.e. the sign bit |
|
|
900 | will be the most significant bit, followed by exponent and mantissa. |
|
|
901 | |
|
|
902 | This function should work even when the native floating point format isn't |
|
|
903 | IEEE compliant, of course at a speed and code size penalty, and of course |
|
|
904 | also within reasonable limits (it tries to convert NaNs, infinities and |
|
|
905 | denormals, but will likely convert negative zero to positive zero). |
|
|
906 | |
|
|
907 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
|
|
908 | be able to optimise away this function completely. |
|
|
909 | |
|
|
910 | These functions can be helpful when serialising floats to the network - you |
|
|
911 | can serialise the return value like a normal uint16_t/uint32_t/uint64_t. |
|
|
912 | |
|
|
913 | Another use for these functions is to manipulate floating point values |
|
|
914 | directly. |
|
|
915 | |
|
|
916 | Silly example: toggle the sign bit of a float. |
|
|
917 | |
|
|
918 | /* On gcc-4.7 on amd64, */ |
|
|
919 | /* this results in a single add instruction to toggle the bit, and 4 extra */ |
|
|
920 | /* instructions to move the float value to an integer register and back. */ |
|
|
921 | |
|
|
922 | x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U) |
|
|
923 | |
|
|
924 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
|
|
925 | |
|
|
926 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
|
|
927 | |
|
|
928 | =item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM] |
|
|
929 | |
|
|
930 | The reverse operation of the previous function - takes the bit |
|
|
931 | representation of an IEEE binary16, binary32 or binary64 number (half, |
|
|
932 | single or double precision) and converts it to the native C<float> or |
|
|
933 | C<double> format. |
|
|
934 | |
|
|
935 | This function should work even when the native floating point format isn't |
|
|
936 | IEEE compliant, of course at a speed and code size penalty, and of course |
|
|
937 | also within reasonable limits (it tries to convert normals and denormals, |
|
|
938 | and might be lucky for infinities, and with extraordinary luck, also for |
|
|
939 | negative zero). |
|
|
940 | |
|
|
941 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
|
|
942 | be able to optimise away this function completely. |
|
|
943 | |
|
|
944 | =item uint16_t ecb_binary32_to_binary16 (uint32_t x) |
|
|
945 | |
|
|
946 | =item uint32_t ecb_binary16_to_binary32 (uint16_t x) |
|
|
947 | |
|
|
948 | Convert a IEEE binary32/single precision to binary16/half format, and vice |
|
|
949 | versa, handling all details (round-to-nearest-even, subnormals, infinity |
|
|
950 | and NaNs) correctly. |
|
|
951 | |
|
|
952 | These are functions are available under C<-DECB_NO_LIBM>, since |
|
|
953 | they do not rely on the platform floating point format. The |
|
|
954 | C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are |
|
|
955 | usually what you want. |
575 | |
956 | |
576 | =back |
957 | =back |
577 | |
958 | |
578 | =head2 ARITHMETIC |
959 | =head2 ARITHMETIC |
579 | |
960 | |
… | |
… | |
636 | |
1017 | |
637 | These symbols need to be defined before including F<ecb.h> the first time. |
1018 | These symbols need to be defined before including F<ecb.h> the first time. |
638 | |
1019 | |
639 | =over 4 |
1020 | =over 4 |
640 | |
1021 | |
641 | =item ECB_NO_THRADS |
1022 | =item ECB_NO_THREADS |
642 | |
1023 | |
643 | If F<ecb.h> is never used from multiple threads, then this symbol can |
1024 | If F<ecb.h> is never used from multiple threads, then this symbol can |
644 | be defined, in which case memory fences (and similar constructs) are |
1025 | be defined, in which case memory fences (and similar constructs) are |
645 | completely removed, leading to more efficient code and fewer dependencies. |
1026 | completely removed, leading to more efficient code and fewer dependencies. |
646 | |
1027 | |
… | |
… | |
652 | multiple threads, but never concurrently (e.g. if the system the program |
1033 | multiple threads, but never concurrently (e.g. if the system the program |
653 | runs on has only a single CPU with a single core, no hyperthreading and so |
1034 | runs on has only a single CPU with a single core, no hyperthreading and so |
654 | on), then this symbol can be defined, leading to more efficient code and |
1035 | on), then this symbol can be defined, leading to more efficient code and |
655 | fewer dependencies. |
1036 | fewer dependencies. |
656 | |
1037 | |
657 | =back |
1038 | =item ECB_NO_LIBM |
658 | |
1039 | |
|
|
1040 | When defined to C<1>, do not export any functions that might introduce |
|
|
1041 | dependencies on the math library (usually called F<-lm>) - these are |
|
|
1042 | marked with [-UECB_NO_LIBM]. |
659 | |
1043 | |
|
|
1044 | =back |
|
|
1045 | |
|
|
1046 | =head1 UNDOCUMENTED FUNCTIONALITY |
|
|
1047 | |
|
|
1048 | F<ecb.h> is full of undocumented functionality as well, some of which is |
|
|
1049 | intended to be internal-use only, some of which we forgot to document, and |
|
|
1050 | some of which we hide because we are not sure we will keep the interface |
|
|
1051 | stable. |
|
|
1052 | |
|
|
1053 | While you are welcome to rummage around and use whatever you find useful |
|
|
1054 | (we can't stop you), keep in mind that we will change undocumented |
|
|
1055 | functionality in incompatible ways without thinking twice, while we are |
|
|
1056 | considerably more conservative with documented things. |
|
|
1057 | |
|
|
1058 | =head1 AUTHORS |
|
|
1059 | |
|
|
1060 | C<libecb> is designed and maintained by: |
|
|
1061 | |
|
|
1062 | Emanuele Giaquinta <e.giaquinta@glauco.it> |
|
|
1063 | Marc Alexander Lehmann <schmorp@schmorp.de> |
|
|
1064 | |
|
|
1065 | |