… | |
… | |
186 | it. This is mainly useful to get the contents of a macro in string form, |
186 | it. This is mainly useful to get the contents of a macro in string form, |
187 | e.g.: |
187 | e.g.: |
188 | |
188 | |
189 | #define SQL_LIMIT 100 |
189 | #define SQL_LIMIT 100 |
190 | sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT)); |
190 | sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT)); |
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191 | |
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192 | =item ECB_STRINGIFY_EXPR (expr) |
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193 | |
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194 | Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it |
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195 | is a valid expression. This is useful to catch typos or cases where the |
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196 | macro isn't available: |
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197 | |
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198 | #include <errno.h> |
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199 | |
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200 | ECB_STRINGIFY (EDOM); // "33" (on my system at least) |
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201 | ECB_STRINGIFY_EXPR (EDOM); // "33" |
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202 | |
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203 | // now imagine we had a typo: |
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204 | |
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205 | ECB_STRINGIFY (EDAM); // "EDAM" |
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206 | ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined |
191 | |
207 | |
192 | =back |
208 | =back |
193 | |
209 | |
194 | =head2 ATTRIBUTES |
210 | =head2 ATTRIBUTES |
195 | |
211 | |
… | |
… | |
226 | Similar to C<ecb_unused>, but marks a function, variable or type as |
242 | 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. |
243 | deprecated. This makes some compilers warn when the type is used. |
228 | |
244 | |
229 | =item ecb_deprecated_message (message) |
245 | =item ecb_deprecated_message (message) |
230 | |
246 | |
231 | Same as C<ecb_deprecated>, but if possible, supply a diagnostic that is |
247 | 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 |
248 | used instead of a generic depreciation message when the object is being |
233 | used. |
249 | used. |
234 | |
250 | |
235 | =item ecb_inline |
251 | =item ecb_inline |
236 | |
252 | |
… | |
… | |
246 | return - (a * b); |
262 | return - (a * b); |
247 | } |
263 | } |
248 | |
264 | |
249 | =item ecb_noinline |
265 | =item ecb_noinline |
250 | |
266 | |
251 | Prevent a function from being inlined - it might be optimised away, but |
267 | 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 |
268 | 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. |
269 | is rarely called and large enough for inlining not to be helpful. |
254 | |
270 | |
255 | =item ecb_noreturn |
271 | =item ecb_noreturn |
256 | |
272 | |
… | |
… | |
473 | real_reserve_method (size); /* presumably noinline */ |
489 | real_reserve_method (size); /* presumably noinline */ |
474 | } |
490 | } |
475 | |
491 | |
476 | =item ecb_assume (cond) |
492 | =item ecb_assume (cond) |
477 | |
493 | |
478 | Try to tell the compiler that some condition is true, even if it's not |
494 | Tries to tell the compiler that some condition is true, even if it's not |
479 | obvious. |
495 | obvious. This is not a function, but a statement: it cannot be used in |
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496 | another expression. |
480 | |
497 | |
481 | This can be used to teach the compiler about invariants or other |
498 | This can be used to teach the compiler about invariants or other |
482 | conditions that might improve code generation, but which are impossible to |
499 | conditions that might improve code generation, but which are impossible to |
483 | deduce form the code itself. |
500 | deduce form the code itself. |
484 | |
501 | |
… | |
… | |
505 | |
522 | |
506 | =item ecb_unreachable () |
523 | =item ecb_unreachable () |
507 | |
524 | |
508 | This function does nothing itself, except tell the compiler that it will |
525 | 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 |
526 | 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. |
527 | function can be used to implement C<ecb_assume> or similar functionality. |
511 | |
528 | |
512 | =item ecb_prefetch (addr, rw, locality) |
529 | =item ecb_prefetch (addr, rw, locality) |
513 | |
530 | |
514 | Tells the compiler to try to prefetch memory at the given C<addr>ess |
531 | 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 |
532 | 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 |
534 | 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 |
535 | 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> |
536 | need to be accessible (it could be a null pointer for example), but C<rw> |
520 | and C<locality> must be compile-time constants. |
537 | and C<locality> must be compile-time constants. |
521 | |
538 | |
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|
539 | This is a statement, not a function: you cannot use it as part of an |
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540 | expression. |
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|
541 | |
522 | An obvious way to use this is to prefetch some data far away, in a big |
542 | 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, |
543 | 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. |
544 | in the hope that it will be ready when the CPU arrives at that location. |
525 | |
545 | |
526 | int sum = 0; |
546 | int sum = 0; |
… | |
… | |
578 | |
598 | |
579 | =item bool ecb_is_pot32 (uint32_t x) |
599 | =item bool ecb_is_pot32 (uint32_t x) |
580 | |
600 | |
581 | =item bool ecb_is_pot64 (uint32_t x) |
601 | =item bool ecb_is_pot64 (uint32_t x) |
582 | |
602 | |
583 | Return true iff C<x> is a power of two or C<x == 0>. |
603 | Returns true iff C<x> is a power of two or C<x == 0>. |
584 | |
604 | |
585 | For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>. |
605 | For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>. |
586 | |
606 | |
587 | =item int ecb_ld32 (uint32_t x) |
607 | =item int ecb_ld32 (uint32_t x) |
588 | |
608 | |
589 | =item int ecb_ld64 (uint64_t x) |
609 | =item int ecb_ld64 (uint64_t x) |
590 | |
610 | |
… | |
… | |
666 | |
686 | |
667 | =head2 FLOATING POINT FIDDLING |
687 | =head2 FLOATING POINT FIDDLING |
668 | |
688 | |
669 | =over 4 |
689 | =over 4 |
670 | |
690 | |
671 | =item ECB_INFINITY |
691 | =item ECB_INFINITY [-UECB_NO_LIBM] |
672 | |
692 | |
673 | Evaluates to positive infinity if supported by the platform, otherwise to |
693 | Evaluates to positive infinity if supported by the platform, otherwise to |
674 | a truly huge number. |
694 | a truly huge number. |
675 | |
695 | |
676 | =item ECB_NON |
696 | =item ECB_NAN [-UECB_NO_LIBM] |
677 | |
697 | |
678 | Evaluates to a quiet NAN if supported by the platform, otherwise to |
698 | Evaluates to a quiet NAN if supported by the platform, otherwise to |
679 | C<ECB_INFINITY>. |
699 | C<ECB_INFINITY>. |
680 | |
700 | |
681 | =item float ecb_ldexpf (float x, int exp) |
701 | =item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM] |
682 | |
702 | |
683 | Same as C<ldexpf>, but always available. |
703 | Same as C<ldexpf>, but always available. |
684 | |
704 | |
|
|
705 | =item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM] |
|
|
706 | |
685 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
707 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
686 | |
708 | |
687 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
709 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
688 | |
710 | |
689 | These functions each take an argument in the native C<float> or C<double> |
711 | 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. |
712 | type and return the IEEE 754 bit representation of it (binary16/half, |
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|
713 | binary32/single or binary64/double precision). |
691 | |
714 | |
692 | The bit representation is just as IEEE 754 defines it, i.e. the sign bit |
715 | 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. |
716 | will be the most significant bit, followed by exponent and mantissa. |
694 | |
717 | |
695 | This function should work even when the native floating point format isn't |
718 | This function should work even when the native floating point format isn't |
… | |
… | |
699 | |
722 | |
700 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
723 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
701 | be able to optimise away this function completely. |
724 | be able to optimise away this function completely. |
702 | |
725 | |
703 | These functions can be helpful when serialising floats to the network - you |
726 | 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. |
727 | can serialise the return value like a normal uint16_t/uint32_t/uint64_t. |
705 | |
728 | |
706 | Another use for these functions is to manipulate floating point values |
729 | Another use for these functions is to manipulate floating point values |
707 | directly. |
730 | directly. |
708 | |
731 | |
709 | Silly example: toggle the sign bit of a float. |
732 | Silly example: toggle the sign bit of a float. |
… | |
… | |
716 | |
739 | |
717 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
740 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
718 | |
741 | |
719 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
742 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
720 | |
743 | |
721 | =item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM] |
744 | =item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM] |
722 | |
745 | |
723 | The reverse operation of the previous function - takes the bit |
746 | The reverse operation of the previous function - takes the bit |
724 | representation of an IEEE binary16, binary32 or binary64 number and |
747 | representation of an IEEE binary16, binary32 or binary64 number (half, |
725 | converts it to the native C<float> or C<double> format. |
748 | single or double precision) and converts it to the native C<float> or |
|
|
749 | C<double> format. |
726 | |
750 | |
727 | This function should work even when the native floating point format isn't |
751 | 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 |
752 | 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, |
753 | also within reasonable limits (it tries to convert normals and denormals, |
730 | and might be lucky for infinities, and with extraordinary luck, also for |
754 | and might be lucky for infinities, and with extraordinary luck, also for |
731 | negative zero). |
755 | negative zero). |
732 | |
756 | |
733 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
757 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
734 | be able to optimise away this function completely. |
758 | be able to optimise away this function completely. |
|
|
759 | |
|
|
760 | =item uint16_t ecb_binary32_to_binary16 (uint32_t x) |
|
|
761 | |
|
|
762 | =item uint32_t ecb_binary16_to_binary32 (uint16_t x) |
|
|
763 | |
|
|
764 | Convert a IEEE binary32/single precision to binary16/half format, and vice |
|
|
765 | versa, handling all details (round-to-even, subnormals, infinity and NaNs) |
|
|
766 | correctly. |
|
|
767 | |
|
|
768 | These are functions are available under C<-DECB_NO_LIBM>, since |
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|
769 | they do not rely on the platform floating point format. The |
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|
770 | C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are |
|
|
771 | usually what you want. |
735 | |
772 | |
736 | =back |
773 | =back |
737 | |
774 | |
738 | =head2 ARITHMETIC |
775 | =head2 ARITHMETIC |
739 | |
776 | |
… | |
… | |
820 | dependencies on the math library (usually called F<-lm>) - these are |
857 | dependencies on the math library (usually called F<-lm>) - these are |
821 | marked with [-UECB_NO_LIBM]. |
858 | marked with [-UECB_NO_LIBM]. |
822 | |
859 | |
823 | =back |
860 | =back |
824 | |
861 | |
|
|
862 | =head1 UNDOCUMENTED FUNCTIONALITY |
825 | |
863 | |
|
|
864 | F<ecb.h> is full of undocumented functionality as well, some of which is |
|
|
865 | intended to be internal-use only, some of which we forgot to document, and |
|
|
866 | some of which we hide because we are not sure we will keep the interface |
|
|
867 | stable. |
|
|
868 | |
|
|
869 | While you are welcome to rummage around and use whatever you find useful |
|
|
870 | (we can't stop you), keep in mind that we will change undocumented |
|
|
871 | functionality in incompatible ways without thinking twice, while we are |
|
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872 | considerably more conservative with documented things. |
|
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873 | |
|
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874 | =head1 AUTHORS |
|
|
875 | |
|
|
876 | C<libecb> is designed and maintained by: |
|
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877 | |
|
|
878 | Emanuele Giaquinta <e.giaquinta@glauco.it> |
|
|
879 | Marc Alexander Lehmann <schmorp@schmorp.de> |
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880 | |
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881 | |