… | |
… | |
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 |
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 |
… | |
… | |
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. |
108 | |
114 | |
109 | =item ECB_GCC_VERSION (major, minor) |
115 | =item ECB_GCC_VERSION (major, minor) |
110 | |
116 | |
111 | 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) |
112 | 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 |
… | |
… | |
186 | it. This is mainly useful to get the contents of a macro in string form, |
192 | it. This is mainly useful to get the contents of a macro in string form, |
187 | e.g.: |
193 | e.g.: |
188 | |
194 | |
189 | #define SQL_LIMIT 100 |
195 | #define SQL_LIMIT 100 |
190 | sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT)); |
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 |
191 | |
213 | |
192 | =back |
214 | =back |
193 | |
215 | |
194 | =head2 ATTRIBUTES |
216 | =head2 ATTRIBUTES |
195 | |
217 | |
… | |
… | |
226 | Similar to C<ecb_unused>, but marks a function, variable or type as |
248 | 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. |
249 | deprecated. This makes some compilers warn when the type is used. |
228 | |
250 | |
229 | =item ecb_deprecated_message (message) |
251 | =item ecb_deprecated_message (message) |
230 | |
252 | |
231 | Same as C<ecb_deprecated>, but if possible, supply a diagnostic that is |
253 | 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 |
254 | used instead of a generic depreciation message when the object is being |
233 | used. |
255 | used. |
234 | |
256 | |
235 | =item ecb_inline |
257 | =item ecb_inline |
236 | |
258 | |
237 | Expands either to C<static inline> or to just C<static>, if inline |
259 | 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 |
260 | to just C<static>, if inline isn't supported. It should be used to declare |
239 | inlined, for code size or speed reasons. |
261 | functions that should be inlined, for code size or speed reasons. |
240 | |
262 | |
241 | Example: inline this function, it surely will reduce codesize. |
263 | Example: inline this function, it surely will reduce codesize. |
242 | |
264 | |
243 | ecb_inline int |
265 | ecb_inline int |
244 | negmul (int a, int b) |
266 | negmul (int a, int b) |
… | |
… | |
246 | return - (a * b); |
268 | return - (a * b); |
247 | } |
269 | } |
248 | |
270 | |
249 | =item ecb_noinline |
271 | =item ecb_noinline |
250 | |
272 | |
251 | 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 |
252 | 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 |
253 | 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. |
254 | |
276 | |
255 | =item ecb_noreturn |
277 | =item ecb_noreturn |
256 | |
278 | |
… | |
… | |
385 | =back |
407 | =back |
386 | |
408 | |
387 | =head2 OPTIMISATION HINTS |
409 | =head2 OPTIMISATION HINTS |
388 | |
410 | |
389 | =over 4 |
411 | =over 4 |
|
|
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. |
390 | |
418 | |
391 | =item bool ecb_is_constant (expr) |
419 | =item bool ecb_is_constant (expr) |
392 | |
420 | |
393 | 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 |
394 | constant, and false otherwise. |
422 | constant, and false otherwise. |
… | |
… | |
473 | real_reserve_method (size); /* presumably noinline */ |
501 | real_reserve_method (size); /* presumably noinline */ |
474 | } |
502 | } |
475 | |
503 | |
476 | =item ecb_assume (cond) |
504 | =item ecb_assume (cond) |
477 | |
505 | |
478 | 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 |
479 | obvious. |
507 | obvious. This is not a function, but a statement: it cannot be used in |
|
|
508 | another expression. |
480 | |
509 | |
481 | 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 |
482 | conditions that might improve code generation, but which are impossible to |
511 | conditions that might improve code generation, but which are impossible to |
483 | deduce form the code itself. |
512 | deduce form the code itself. |
484 | |
513 | |
… | |
… | |
505 | |
534 | |
506 | =item ecb_unreachable () |
535 | =item ecb_unreachable () |
507 | |
536 | |
508 | 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 |
509 | 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 |
510 | 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. |
511 | |
540 | |
512 | =item ecb_prefetch (addr, rw, locality) |
541 | =item ecb_prefetch (addr, rw, locality) |
513 | |
542 | |
514 | 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 |
515 | 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 |
… | |
… | |
517 | 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 |
518 | 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 |
519 | 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> |
520 | and C<locality> must be compile-time constants. |
549 | and C<locality> must be compile-time constants. |
521 | |
550 | |
|
|
551 | This is a statement, not a function: you cannot use it as part of an |
|
|
552 | expression. |
|
|
553 | |
522 | 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 |
523 | 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, |
524 | 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. |
525 | |
557 | |
526 | int sum = 0; |
558 | int sum = 0; |
… | |
… | |
578 | |
610 | |
579 | =item bool ecb_is_pot32 (uint32_t x) |
611 | =item bool ecb_is_pot32 (uint32_t x) |
580 | |
612 | |
581 | =item bool ecb_is_pot64 (uint32_t x) |
613 | =item bool ecb_is_pot64 (uint32_t x) |
582 | |
614 | |
583 | 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>. |
584 | |
616 | |
585 | 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>. |
586 | |
618 | |
587 | =item int ecb_ld32 (uint32_t x) |
619 | =item int ecb_ld32 (uint32_t x) |
588 | |
620 | |
589 | =item int ecb_ld64 (uint64_t x) |
621 | =item int ecb_ld64 (uint64_t x) |
590 | |
622 | |
… | |
… | |
636 | |
668 | |
637 | 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 |
638 | 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 |
639 | C<ecb_bswap32>). |
671 | C<ecb_bswap32>). |
640 | |
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 | |
641 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
678 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
642 | |
679 | |
643 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
680 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
644 | |
681 | |
645 | =item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
682 | =item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
… | |
… | |
662 | 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 |
663 | x86). |
700 | x86). |
664 | |
701 | |
665 | =back |
702 | =back |
666 | |
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) |
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852 | |
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853 | =item ecb_poke_u (void *ptr, T v) |
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854 | |
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855 | =item ecb_poke_be_u (void *ptr, T v) |
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856 | |
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857 | =item ecb_poke_le_u (void *ptr, T v) |
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858 | |
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859 | Again, similarly to their C counterparts, these functions store an |
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860 | unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to |
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861 | big/little endian. |
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862 | |
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863 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
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864 | |
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865 | Unlike their C counterparts, these functions support 8 bit quantities |
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866 | (C<uint8_t>) and also have an aligned version (without the C<_u> prefix), |
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867 | all of which hopefully makes them more useful in generic code. |
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868 | |
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869 | =back |
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870 | |
667 | =head2 FLOATING POINT FIDDLING |
871 | =head2 FLOATING POINT FIDDLING |
668 | |
872 | |
669 | =over 4 |
873 | =over 4 |
670 | |
874 | |
671 | =item ECB_INFINITY |
875 | =item ECB_INFINITY [-UECB_NO_LIBM] |
672 | |
876 | |
673 | Evaluates to positive infinity if supported by the platform, otherwise to |
877 | Evaluates to positive infinity if supported by the platform, otherwise to |
674 | a truly huge number. |
878 | a truly huge number. |
675 | |
879 | |
676 | =item ECB_NON |
880 | =item ECB_NAN [-UECB_NO_LIBM] |
677 | |
881 | |
678 | Evaluates to a quiet NAN if supported by the platform, otherwise to |
882 | Evaluates to a quiet NAN if supported by the platform, otherwise to |
679 | C<ECB_INFINITY>. |
883 | C<ECB_INFINITY>. |
680 | |
884 | |
681 | =item float ecb_ldexpf (float x, int exp) |
885 | =item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM] |
682 | |
886 | |
683 | Same as C<ldexpf>, but always available. |
887 | Same as C<ldexpf>, but always available. |
684 | |
888 | |
|
|
889 | =item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM] |
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890 | |
685 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
891 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
686 | |
892 | |
687 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
893 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
688 | |
894 | |
689 | These functions each take an argument in the native C<float> or C<double> |
895 | 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. |
896 | type and return the IEEE 754 bit representation of it (binary16/half, |
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897 | binary32/single or binary64/double precision). |
691 | |
898 | |
692 | The bit representation is just as IEEE 754 defines it, i.e. the sign bit |
899 | 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. |
900 | will be the most significant bit, followed by exponent and mantissa. |
694 | |
901 | |
695 | This function should work even when the native floating point format isn't |
902 | This function should work even when the native floating point format isn't |
… | |
… | |
699 | |
906 | |
700 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
907 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
701 | be able to optimise away this function completely. |
908 | be able to optimise away this function completely. |
702 | |
909 | |
703 | These functions can be helpful when serialising floats to the network - you |
910 | 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. |
911 | can serialise the return value like a normal uint16_t/uint32_t/uint64_t. |
705 | |
912 | |
706 | Another use for these functions is to manipulate floating point values |
913 | Another use for these functions is to manipulate floating point values |
707 | directly. |
914 | directly. |
708 | |
915 | |
709 | Silly example: toggle the sign bit of a float. |
916 | Silly example: toggle the sign bit of a float. |
… | |
… | |
716 | |
923 | |
717 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
924 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
718 | |
925 | |
719 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
926 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
720 | |
927 | |
721 | =item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM] |
928 | =item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM] |
722 | |
929 | |
723 | The reverse operation of the previous function - takes the bit |
930 | The reverse operation of the previous function - takes the bit |
724 | representation of an IEEE binary16, binary32 or binary64 number and |
931 | representation of an IEEE binary16, binary32 or binary64 number (half, |
725 | converts it to the native C<float> or C<double> format. |
932 | single or double precision) and converts it to the native C<float> or |
|
|
933 | C<double> format. |
726 | |
934 | |
727 | This function should work even when the native floating point format isn't |
935 | 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 |
936 | 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, |
937 | also within reasonable limits (it tries to convert normals and denormals, |
730 | and might be lucky for infinities, and with extraordinary luck, also for |
938 | and might be lucky for infinities, and with extraordinary luck, also for |
731 | negative zero). |
939 | negative zero). |
732 | |
940 | |
733 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
941 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
734 | be able to optimise away this function completely. |
942 | be able to optimise away this function completely. |
|
|
943 | |
|
|
944 | =item uint16_t ecb_binary32_to_binary16 (uint32_t x) |
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|
945 | |
|
|
946 | =item uint32_t ecb_binary16_to_binary32 (uint16_t x) |
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|
947 | |
|
|
948 | Convert a IEEE binary32/single precision to binary16/half format, and vice |
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|
949 | versa, handling all details (round-to-nearest-even, subnormals, infinity |
|
|
950 | and NaNs) correctly. |
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|
951 | |
|
|
952 | These are functions are available under C<-DECB_NO_LIBM>, since |
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|
953 | they do not rely on the platform floating point format. The |
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954 | C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are |
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|
955 | usually what you want. |
735 | |
956 | |
736 | =back |
957 | =back |
737 | |
958 | |
738 | =head2 ARITHMETIC |
959 | =head2 ARITHMETIC |
739 | |
960 | |
… | |
… | |
820 | dependencies on the math library (usually called F<-lm>) - these are |
1041 | dependencies on the math library (usually called F<-lm>) - these are |
821 | marked with [-UECB_NO_LIBM]. |
1042 | marked with [-UECB_NO_LIBM]. |
822 | |
1043 | |
823 | =back |
1044 | =back |
824 | |
1045 | |
|
|
1046 | =head1 UNDOCUMENTED FUNCTIONALITY |
825 | |
1047 | |
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|
1048 | F<ecb.h> is full of undocumented functionality as well, some of which is |
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|
1049 | intended to be internal-use only, some of which we forgot to document, and |
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1050 | some of which we hide because we are not sure we will keep the interface |
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1051 | stable. |
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1052 | |
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1053 | While you are welcome to rummage around and use whatever you find useful |
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1054 | (we can't stop you), keep in mind that we will change undocumented |
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|
1055 | functionality in incompatible ways without thinking twice, while we are |
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1056 | considerably more conservative with documented things. |
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1057 | |
|
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1058 | =head1 AUTHORS |
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1059 | |
|
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1060 | C<libecb> is designed and maintained by: |
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1061 | |
|
|
1062 | Emanuele Giaquinta <e.giaquinta@glauco.it> |
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|
1063 | Marc Alexander Lehmann <schmorp@schmorp.de> |
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1064 | |
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1065 | |