… | |
… | |
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_t int16_t uint16_t |
64 | int32_t uint32_t int64_t uint64_t |
64 | int32_t uint32_t int64_t uint64_t |
65 | intptr_t uintptr_t ptrdiff_t |
65 | intptr_t uintptr_t |
66 | |
66 | |
67 | The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this |
67 | 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 |
68 | platform (currently C<4> or C<8>) and can be used in preprocessor |
69 | expressions. |
69 | expressions. |
70 | |
70 | |
|
|
71 | For C<ptrdiff_t> and C<size_t> use C<stddef.h>. |
|
|
72 | |
71 | =head2 LANGUAGE/COMPILER VERSIONS |
73 | =head2 LANGUAGE/COMPILER VERSIONS |
72 | |
74 | |
73 | All the following symbols expand to an expressionb that cna be tested in |
75 | 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 |
76 | 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). |
77 | ensure it's either C<0> or C<1> if you need that). |
76 | |
78 | |
77 | =over 4 |
79 | =over 4 |
78 | |
80 | |
79 | =item ECB_C |
81 | =item ECB_C |
80 | |
82 | |
81 | True if the implementation defines the C<__STDC__> macro to a true value, |
83 | True if the implementation defines the C<__STDC__> macro to a true value, |
82 | which is typically true for both C and C++ compilers. |
84 | while not claiming to be C++. |
83 | |
85 | |
84 | =item ECB_C99 |
86 | =item ECB_C99 |
85 | |
87 | |
86 | True if the implementation claims to be C99 compliant. |
88 | 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++. |
|
|
90 | |
|
|
91 | Note that later versions (ECB_C11) remove core features again (for |
|
|
92 | example, variable length arrays). |
87 | |
93 | |
88 | =item ECB_C11 |
94 | =item ECB_C11 |
89 | |
95 | |
90 | True if the implementation claims to be C11 compliant. |
96 | True if the implementation claims to be compliant to C11 (ISO/IEC |
|
|
97 | 9899:2011) or any later version, while not claiming to be C++. |
91 | |
98 | |
92 | =item ECB_CPP |
99 | =item ECB_CPP |
93 | |
100 | |
94 | True if the implementation defines the C<__cplusplus__> macro to a true |
101 | True if the implementation defines the C<__cplusplus__> macro to a true |
95 | value, which is typically true for C++ compilers. |
102 | value, which is typically true for C++ compilers. |
96 | |
103 | |
97 | =item ECB_CPP98 |
|
|
98 | |
|
|
99 | True if the implementation claims to be compliant to ISO/IEC 14882:1998 |
|
|
100 | (the first C++ ISO standard) or any later vwersion. Typically true for all |
|
|
101 | C++ compilers. |
|
|
102 | |
|
|
103 | =item ECB_CPP11 |
104 | =item ECB_CPP11 |
104 | |
105 | |
105 | True if the implementation claims to be compliant to ISO/IEC 14882:2011 |
106 | True if the implementation claims to be compliant to ISO/IEC 14882:2011 |
106 | (C++11) or any later vwersion. |
107 | (C++11) or any later version. |
107 | |
108 | |
108 | =item ECB_GCC_VERSION(major,minor) |
109 | =item ECB_GCC_VERSION (major, minor) |
109 | |
110 | |
110 | Expands to a true value (suitable for testing in by the preprocessor) |
111 | 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 givne version, or |
112 | if the compiler used is GNU C and the version is the given version, or |
112 | higher. |
113 | higher. |
113 | |
114 | |
114 | This macro tries to return false on compilers that claim to be GCC |
115 | This macro tries to return false on compilers that claim to be GCC |
115 | compatible but aren't. |
116 | compatible but aren't. |
|
|
117 | |
|
|
118 | =item ECB_EXTERN_C |
|
|
119 | |
|
|
120 | Expands to C<extern "C"> in C++, and a simple C<extern> in C. |
|
|
121 | |
|
|
122 | This can be used to declare a single external C function: |
|
|
123 | |
|
|
124 | ECB_EXTERN_C int printf (const char *format, ...); |
|
|
125 | |
|
|
126 | =item ECB_EXTERN_C_BEG / ECB_EXTERN_C_END |
|
|
127 | |
|
|
128 | These two macros can be used to wrap multiple C<extern "C"> definitions - |
|
|
129 | they expand to nothing in C. |
|
|
130 | |
|
|
131 | They are most useful in header files: |
|
|
132 | |
|
|
133 | ECB_EXTERN_C_BEG |
|
|
134 | |
|
|
135 | int mycfun1 (int x); |
|
|
136 | int mycfun2 (int x); |
|
|
137 | |
|
|
138 | ECB_EXTERN_C_END |
|
|
139 | |
|
|
140 | =item ECB_STDFP |
|
|
141 | |
|
|
142 | If this evaluates to a true value (suitable for testing in by the |
|
|
143 | preprocessor), then C<float> and C<double> use IEEE 754 single/binary32 |
|
|
144 | and double/binary64 representations internally I<and> the endianness of |
|
|
145 | both types match the endianness of C<uint32_t> and C<uint64_t>. |
|
|
146 | |
|
|
147 | This means you can just copy the bits of a C<float> (or C<double>) to an |
|
|
148 | C<uint32_t> (or C<uint64_t>) and get the raw IEEE 754 bit representation |
|
|
149 | without having to think about format or endianness. |
|
|
150 | |
|
|
151 | 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 |
|
|
153 | side. |
|
|
154 | |
|
|
155 | =item ECB_AMD64, ECB_AMD64_X32 |
|
|
156 | |
|
|
157 | These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32 |
|
|
158 | ABI, respectively, and undefined elsewhere. |
|
|
159 | |
|
|
160 | The designers of the new X32 ABI for some inexplicable reason decided to |
|
|
161 | make it look exactly like amd64, even though it's completely incompatible |
|
|
162 | to that ABI, breaking about every piece of software that assumed that |
|
|
163 | C<__x86_64> stands for, well, the x86-64 ABI, making these macros |
|
|
164 | necessary. |
116 | |
165 | |
117 | =back |
166 | =back |
118 | |
167 | |
119 | =head2 GCC ATTRIBUTES |
168 | =head2 GCC ATTRIBUTES |
120 | |
169 | |
… | |
… | |
136 | |
185 | |
137 | =over 4 |
186 | =over 4 |
138 | |
187 | |
139 | =item ecb_attribute ((attrs...)) |
188 | =item ecb_attribute ((attrs...)) |
140 | |
189 | |
141 | A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to |
190 | A simple wrapper that expands to C<__attribute__((attrs))> on GCC 3.1+ and |
142 | nothing on other compilers, so the effect is that only GCC sees these. |
191 | Clang 2.8+, and to nothing on other compilers, so the effect is that only |
|
|
192 | GCC and Clang see these. |
143 | |
193 | |
144 | Example: use the C<deprecated> attribute on a function. |
194 | Example: use the C<deprecated> attribute on a function. |
145 | |
195 | |
146 | ecb_attribute((__deprecated__)) void |
196 | ecb_attribute((__deprecated__)) void |
147 | do_not_use_me_anymore (void); |
197 | do_not_use_me_anymore (void); |
… | |
… | |
161 | #else |
211 | #else |
162 | return 0; |
212 | return 0; |
163 | #endif |
213 | #endif |
164 | } |
214 | } |
165 | |
215 | |
|
|
216 | =item ecb_deprecated |
|
|
217 | |
|
|
218 | Similar to C<ecb_unused>, but marks a function, variable or type as |
|
|
219 | deprecated. This makes some compilers warn when the type is used. |
|
|
220 | |
166 | =item ecb_inline |
221 | =item ecb_inline |
167 | |
222 | |
168 | This is not actually an attribute, but you use it like one. It expands |
223 | This is not actually an attribute, but you use it like one. It expands |
169 | either to C<static inline> or to just C<static>, if inline isn't |
224 | either to C<static inline> or to just C<static>, if inline isn't |
170 | supported. It should be used to declare functions that should be inlined, |
225 | supported. It should be used to declare functions that should be inlined, |
… | |
… | |
198 | } |
253 | } |
199 | |
254 | |
200 | In this case, the compiler would probably be smart enough to deduce it on |
255 | In this case, the compiler would probably be smart enough to deduce it on |
201 | its own, so this is mainly useful for declarations. |
256 | its own, so this is mainly useful for declarations. |
202 | |
257 | |
|
|
258 | =item ecb_restrict |
|
|
259 | |
|
|
260 | Expands to the C<restrict> keyword or equivalent on compilers that support |
|
|
261 | them, and to nothing on others. Must be specified on a pointer type or |
|
|
262 | an array index to indicate that the memory doesn't alias with any other |
|
|
263 | restricted pointer in the same scope. |
|
|
264 | |
|
|
265 | Example: multiply a vector, and allow the compiler to parallelise the |
|
|
266 | loop, because it knows it doesn't overwrite input values. |
|
|
267 | |
|
|
268 | void |
|
|
269 | multiply (float *ecb_restrict src, |
|
|
270 | float *ecb_restrict dst, |
|
|
271 | int len, float factor) |
|
|
272 | { |
|
|
273 | int i; |
|
|
274 | |
|
|
275 | for (i = 0; i < len; ++i) |
|
|
276 | dst [i] = src [i] * factor; |
|
|
277 | } |
|
|
278 | |
203 | =item ecb_const |
279 | =item ecb_const |
204 | |
280 | |
205 | Declares that the function only depends on the values of its arguments, |
281 | 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 |
282 | 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 |
283 | any memory any arguments might point to, global variables, or call any |
… | |
… | |
267 | functions only called in exceptional or rare cases. |
343 | functions only called in exceptional or rare cases. |
268 | |
344 | |
269 | =item ecb_artificial |
345 | =item ecb_artificial |
270 | |
346 | |
271 | Declares the function as "artificial", in this case meaning that this |
347 | 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 |
348 | 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 |
349 | - 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 |
350 | 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. |
351 | usually so helpful, especially when it's inlined to just a few instructions. |
276 | |
352 | |
277 | Marking them as artificial will instruct the debugger about just this, |
353 | Marking them as artificial will instruct the debugger about just this, |
… | |
… | |
297 | |
373 | |
298 | =head2 OPTIMISATION HINTS |
374 | =head2 OPTIMISATION HINTS |
299 | |
375 | |
300 | =over 4 |
376 | =over 4 |
301 | |
377 | |
302 | =item bool ecb_is_constant(expr) |
378 | =item bool ecb_is_constant (expr) |
303 | |
379 | |
304 | Returns true iff the expression can be deduced to be a compile-time |
380 | Returns true iff the expression can be deduced to be a compile-time |
305 | constant, and false otherwise. |
381 | constant, and false otherwise. |
306 | |
382 | |
307 | For example, when you have a C<rndm16> function that returns a 16 bit |
383 | For example, when you have a C<rndm16> function that returns a 16 bit |
… | |
… | |
573 | to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on |
649 | to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on |
574 | x86). |
650 | x86). |
575 | |
651 | |
576 | =back |
652 | =back |
577 | |
653 | |
|
|
654 | =head2 FLOATING POINT FIDDLING |
|
|
655 | |
|
|
656 | =over 4 |
|
|
657 | |
|
|
658 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
|
|
659 | |
|
|
660 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
|
|
661 | |
|
|
662 | These functions each take an argument in the native C<float> or C<double> |
|
|
663 | type and return the IEEE 754 bit representation of it. |
|
|
664 | |
|
|
665 | The bit representation is just as IEEE 754 defines it, i.e. the sign bit |
|
|
666 | will be the most significant bit, followed by exponent and mantissa. |
|
|
667 | |
|
|
668 | This function should work even when the native floating point format isn't |
|
|
669 | IEEE compliant, of course at a speed and code size penalty, and of course |
|
|
670 | also within reasonable limits (it tries to convert NaNs, infinities and |
|
|
671 | denormals, but will likely convert negative zero to positive zero). |
|
|
672 | |
|
|
673 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
|
|
674 | be able to optimise away this function completely. |
|
|
675 | |
|
|
676 | These functions can be helpful when serialising floats to the network - you |
|
|
677 | can serialise the return value like a normal uint32_t/uint64_t. |
|
|
678 | |
|
|
679 | Another use for these functions is to manipulate floating point values |
|
|
680 | directly. |
|
|
681 | |
|
|
682 | Silly example: toggle the sign bit of a float. |
|
|
683 | |
|
|
684 | /* On gcc-4.7 on amd64, */ |
|
|
685 | /* this results in a single add instruction to toggle the bit, and 4 extra */ |
|
|
686 | /* instructions to move the float value to an integer register and back. */ |
|
|
687 | |
|
|
688 | x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U) |
|
|
689 | |
|
|
690 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
|
|
691 | |
|
|
692 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
|
|
693 | |
|
|
694 | =item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM] |
|
|
695 | |
|
|
696 | The reverse operation of the previous function - takes the bit |
|
|
697 | representation of an IEEE binary16, binary32 or binary64 number and |
|
|
698 | converts it to the native C<float> or C<double> format. |
|
|
699 | |
|
|
700 | This function should work even when the native floating point format isn't |
|
|
701 | IEEE compliant, of course at a speed and code size penalty, and of course |
|
|
702 | also within reasonable limits (it tries to convert normals and denormals, |
|
|
703 | and might be lucky for infinities, and with extraordinary luck, also for |
|
|
704 | negative zero). |
|
|
705 | |
|
|
706 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
|
|
707 | be able to optimise away this function completely. |
|
|
708 | |
|
|
709 | =back |
|
|
710 | |
578 | =head2 ARITHMETIC |
711 | =head2 ARITHMETIC |
579 | |
712 | |
580 | =over 4 |
713 | =over 4 |
581 | |
714 | |
582 | =item x = ecb_mod (m, n) |
715 | =item x = ecb_mod (m, n) |
… | |
… | |
636 | |
769 | |
637 | These symbols need to be defined before including F<ecb.h> the first time. |
770 | These symbols need to be defined before including F<ecb.h> the first time. |
638 | |
771 | |
639 | =over 4 |
772 | =over 4 |
640 | |
773 | |
641 | =item ECB_NO_THRADS |
774 | =item ECB_NO_THREADS |
642 | |
775 | |
643 | If F<ecb.h> is never used from multiple threads, then this symbol can |
776 | 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 |
777 | be defined, in which case memory fences (and similar constructs) are |
645 | completely removed, leading to more efficient code and fewer dependencies. |
778 | completely removed, leading to more efficient code and fewer dependencies. |
646 | |
779 | |
… | |
… | |
652 | multiple threads, but never concurrently (e.g. if the system the program |
785 | 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 |
786 | 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 |
787 | on), then this symbol can be defined, leading to more efficient code and |
655 | fewer dependencies. |
788 | fewer dependencies. |
656 | |
789 | |
|
|
790 | =item ECB_NO_LIBM |
|
|
791 | |
|
|
792 | When defined to C<1>, do not export any functions that might introduce |
|
|
793 | dependencies on the math library (usually called F<-lm>) - these are |
|
|
794 | marked with [-UECB_NO_LIBM]. |
|
|
795 | |
657 | =back |
796 | =back |
658 | |
797 | |
659 | |
798 | |