… | |
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10 | |
10 | |
11 | Its homepage can be found here: |
11 | Its homepage can be found here: |
12 | |
12 | |
13 | http://software.schmorp.de/pkg/libecb |
13 | http://software.schmorp.de/pkg/libecb |
14 | |
14 | |
15 | It mainly provides a number of wrappers around GCC built-ins, together |
15 | It mainly provides a number of wrappers around many compiler built-ins, |
16 | with replacement functions for other compilers. In addition to this, |
16 | together with replacement functions for other compilers. In addition |
17 | it provides a number of other lowlevel C utilities, such as endianness |
17 | to this, it provides a number of other lowlevel C utilities, such as |
18 | detection, byte swapping or bit rotations. |
18 | endianness detection, byte swapping or bit rotations. |
19 | |
19 | |
20 | Or in other words, things that should be built into any standard C system, |
20 | Or in other words, things that should be built into any standard C |
21 | but aren't, implemented as efficient as possible with GCC, and still |
21 | system, but aren't, implemented as efficient as possible with GCC (clang, |
22 | correct with other compilers. |
22 | msvc...), and still correct with other compilers. |
23 | |
23 | |
24 | More might come. |
24 | More might come. |
25 | |
25 | |
26 | =head2 ABOUT THE HEADER |
26 | =head2 ABOUT THE HEADER |
27 | |
27 | |
… | |
… | |
80 | |
80 | |
81 | 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 |
82 | 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 |
83 | 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). |
84 | |
84 | |
85 | =over 4 |
85 | =over |
86 | |
86 | |
87 | =item ECB_C |
87 | =item ECB_C |
88 | |
88 | |
89 | 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, |
90 | while not claiming to be C++. |
90 | while not claiming to be C++, i..e C, but not C++. |
91 | |
91 | |
92 | =item ECB_C99 |
92 | =item ECB_C99 |
93 | |
93 | |
94 | True if the implementation claims to be compliant to C99 (ISO/IEC |
94 | True if the implementation claims to be compliant to C99 (ISO/IEC |
95 | 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++. |
… | |
… | |
110 | =item ECB_CPP11, ECB_CPP14, ECB_CPP17 |
110 | =item ECB_CPP11, ECB_CPP14, ECB_CPP17 |
111 | |
111 | |
112 | True if the implementation claims to be compliant to C++11/C++14/C++17 |
112 | True if the implementation claims to be compliant to C++11/C++14/C++17 |
113 | (ISO/IEC 14882:2011, :2014, :2017) or any later version. |
113 | (ISO/IEC 14882:2011, :2014, :2017) or any later version. |
114 | |
114 | |
|
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115 | Note that many C++20 features will likely have their own feature test |
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116 | macros (see e.g. L<http://eel.is/c++draft/cpp.predefined#1.8>). |
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117 | |
|
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118 | =item ECB_OPTIMIZE_SIZE |
|
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119 | |
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120 | Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol |
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121 | can also be defined before including F<ecb.h>, in which case it will be |
|
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122 | unchanged. |
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123 | |
115 | =item ECB_GCC_VERSION (major, minor) |
124 | =item ECB_GCC_VERSION (major, minor) |
116 | |
125 | |
117 | Expands to a true value (suitable for testing in by the preprocessor) |
126 | Expands to a true value (suitable for testing by the preprocessor) if the |
118 | if the compiler used is GNU C and the version is the given version, or |
127 | compiler used is GNU C and the version is the given version, or higher. |
119 | higher. |
|
|
120 | |
128 | |
121 | This macro tries to return false on compilers that claim to be GCC |
129 | This macro tries to return false on compilers that claim to be GCC |
122 | compatible but aren't. |
130 | compatible but aren't. |
123 | |
131 | |
124 | =item ECB_EXTERN_C |
132 | =item ECB_EXTERN_C |
… | |
… | |
143 | |
151 | |
144 | ECB_EXTERN_C_END |
152 | ECB_EXTERN_C_END |
145 | |
153 | |
146 | =item ECB_STDFP |
154 | =item ECB_STDFP |
147 | |
155 | |
148 | If this evaluates to a true value (suitable for testing in by the |
156 | If this evaluates to a true value (suitable for testing by the |
149 | preprocessor), then C<float> and C<double> use IEEE 754 single/binary32 |
157 | preprocessor), then C<float> and C<double> use IEEE 754 single/binary32 |
150 | and double/binary64 representations internally I<and> the endianness of |
158 | and double/binary64 representations internally I<and> the endianness of |
151 | both types match the endianness of C<uint32_t> and C<uint64_t>. |
159 | both types match the endianness of C<uint32_t> and C<uint64_t>. |
152 | |
160 | |
153 | This means you can just copy the bits of a C<float> (or C<double>) to an |
161 | This means you can just copy the bits of a C<float> (or C<double>) to an |
… | |
… | |
155 | without having to think about format or endianness. |
163 | without having to think about format or endianness. |
156 | |
164 | |
157 | This is true for basically all modern platforms, although F<ecb.h> might |
165 | This is true for basically all modern platforms, although F<ecb.h> might |
158 | not be able to deduce this correctly everywhere and might err on the safe |
166 | not be able to deduce this correctly everywhere and might err on the safe |
159 | side. |
167 | side. |
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168 | |
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169 | =item ECB_64BIT_NATIVE |
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170 | |
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171 | Evaluates to a true value (suitable for both preprocessor and C code |
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172 | testing) if 64 bit integer types on this architecture are evaluated |
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173 | "natively", that is, with similar speeds as 32 bit integers. While 64 bit |
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174 | integer support is very common (and in fact required by libecb), 32 bit |
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175 | cpus have to emulate operations on them, so you might want to avoid them. |
160 | |
176 | |
161 | =item ECB_AMD64, ECB_AMD64_X32 |
177 | =item ECB_AMD64, ECB_AMD64_X32 |
162 | |
178 | |
163 | These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32 |
179 | These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32 |
164 | ABI, respectively, and undefined elsewhere. |
180 | ABI, respectively, and undefined elsewhere. |
… | |
… | |
171 | |
187 | |
172 | =back |
188 | =back |
173 | |
189 | |
174 | =head2 MACRO TRICKERY |
190 | =head2 MACRO TRICKERY |
175 | |
191 | |
176 | =over 4 |
192 | =over |
177 | |
193 | |
178 | =item ECB_CONCAT (a, b) |
194 | =item ECB_CONCAT (a, b) |
179 | |
195 | |
180 | Expands any macros in C<a> and C<b>, then concatenates the result to form |
196 | Expands any macros in C<a> and C<b>, then concatenates the result to form |
181 | a single token. This is mainly useful to form identifiers from components, |
197 | a single token. This is mainly useful to form identifiers from components, |
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222 | declarations must be put before the whole declaration: |
238 | declarations must be put before the whole declaration: |
223 | |
239 | |
224 | ecb_const int mysqrt (int a); |
240 | ecb_const int mysqrt (int a); |
225 | ecb_unused int i; |
241 | ecb_unused int i; |
226 | |
242 | |
227 | =over 4 |
243 | =over |
228 | |
244 | |
229 | =item ecb_unused |
245 | =item ecb_unused |
230 | |
246 | |
231 | Marks a function or a variable as "unused", which simply suppresses a |
247 | Marks a function or a variable as "unused", which simply suppresses a |
232 | warning by GCC when it detects it as unused. This is useful when you e.g. |
248 | warning by the compiler when it detects it as unused. This is useful when |
233 | declare a variable but do not always use it: |
249 | you e.g. declare a variable but do not always use it: |
234 | |
250 | |
235 | { |
251 | { |
236 | ecb_unused int var; |
252 | ecb_unused int var; |
237 | |
253 | |
238 | #ifdef SOMECONDITION |
254 | #ifdef SOMECONDITION |
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406 | |
422 | |
407 | =back |
423 | =back |
408 | |
424 | |
409 | =head2 OPTIMISATION HINTS |
425 | =head2 OPTIMISATION HINTS |
410 | |
426 | |
411 | =over 4 |
427 | =over |
412 | |
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413 | =item ECB_OPTIMIZE_SIZE |
|
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414 | |
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|
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 |
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|
417 | unchanged. |
|
|
418 | |
428 | |
419 | =item bool ecb_is_constant (expr) |
429 | =item bool ecb_is_constant (expr) |
420 | |
430 | |
421 | Returns true iff the expression can be deduced to be a compile-time |
431 | Returns true iff the expression can be deduced to be a compile-time |
422 | constant, and false otherwise. |
432 | constant, and false otherwise. |
… | |
… | |
579 | |
589 | |
580 | =back |
590 | =back |
581 | |
591 | |
582 | =head2 BIT FIDDLING / BIT WIZARDRY |
592 | =head2 BIT FIDDLING / BIT WIZARDRY |
583 | |
593 | |
584 | =over 4 |
594 | =over |
585 | |
595 | |
586 | =item bool ecb_big_endian () |
596 | =item bool ecb_big_endian () |
587 | |
597 | |
588 | =item bool ecb_little_endian () |
598 | =item bool ecb_little_endian () |
589 | |
599 | |
… | |
… | |
595 | |
605 | |
596 | =item int ecb_ctz32 (uint32_t x) |
606 | =item int ecb_ctz32 (uint32_t x) |
597 | |
607 | |
598 | =item int ecb_ctz64 (uint64_t x) |
608 | =item int ecb_ctz64 (uint64_t x) |
599 | |
609 | |
|
|
610 | =item int ecb_ctz (T x) [C++] |
|
|
611 | |
600 | Returns the index of the least significant bit set in C<x> (or |
612 | Returns the index of the least significant bit set in C<x> (or |
601 | equivalently the number of bits set to 0 before the least significant bit |
613 | equivalently the number of bits set to 0 before the least significant bit |
602 | set), starting from 0. If C<x> is 0 the result is undefined. |
614 | set), starting from 0. If C<x> is 0 the result is undefined. |
603 | |
615 | |
604 | For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>. |
616 | For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>. |
605 | |
617 | |
|
|
618 | The overloaded C++ C<ecb_ctz> function supports C<uint8_t>, C<uint16_t>, |
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|
619 | C<uint32_t> and C<uint64_t> types. |
|
|
620 | |
606 | For example: |
621 | For example: |
607 | |
622 | |
608 | ecb_ctz32 (3) = 0 |
623 | ecb_ctz32 (3) = 0 |
609 | ecb_ctz32 (6) = 1 |
624 | ecb_ctz32 (6) = 1 |
610 | |
625 | |
611 | =item bool ecb_is_pot32 (uint32_t x) |
626 | =item bool ecb_is_pot32 (uint32_t x) |
612 | |
627 | |
613 | =item bool ecb_is_pot64 (uint32_t x) |
628 | =item bool ecb_is_pot64 (uint32_t x) |
614 | |
629 | |
|
|
630 | =item bool ecb_is_pot (T x) [C++] |
|
|
631 | |
615 | Returns true iff C<x> is a power of two or C<x == 0>. |
632 | Returns true iff C<x> is a power of two or C<x == 0>. |
616 | |
633 | |
617 | For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>. |
634 | For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>. |
618 | |
635 | |
|
|
636 | The overloaded C++ C<ecb_is_pot> function supports C<uint8_t>, C<uint16_t>, |
|
|
637 | C<uint32_t> and C<uint64_t> types. |
|
|
638 | |
619 | =item int ecb_ld32 (uint32_t x) |
639 | =item int ecb_ld32 (uint32_t x) |
620 | |
640 | |
621 | =item int ecb_ld64 (uint64_t x) |
641 | =item int ecb_ld64 (uint64_t x) |
|
|
642 | |
|
|
643 | =item int ecb_ld64 (T x) [C++] |
622 | |
644 | |
623 | Returns the index of the most significant bit set in C<x>, or the number |
645 | Returns the index of the most significant bit set in C<x>, or the number |
624 | of digits the number requires in binary (so that C<< 2**ld <= x < |
646 | of digits the number requires in binary (so that C<< 2**ld <= x < |
625 | 2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is |
647 | 2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is |
626 | to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for |
648 | to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for |
… | |
… | |
631 | the given data type), while C<ecb_ld> returns how many bits the number |
653 | the given data type), while C<ecb_ld> returns how many bits the number |
632 | itself requires. |
654 | itself requires. |
633 | |
655 | |
634 | For smaller types than C<uint32_t> you can safely use C<ecb_ld32>. |
656 | For smaller types than C<uint32_t> you can safely use C<ecb_ld32>. |
635 | |
657 | |
|
|
658 | The overloaded C++ C<ecb_ld> function supports C<uint8_t>, C<uint16_t>, |
|
|
659 | C<uint32_t> and C<uint64_t> types. |
|
|
660 | |
636 | =item int ecb_popcount32 (uint32_t x) |
661 | =item int ecb_popcount32 (uint32_t x) |
637 | |
662 | |
638 | =item int ecb_popcount64 (uint64_t x) |
663 | =item int ecb_popcount64 (uint64_t x) |
639 | |
664 | |
|
|
665 | =item int ecb_popcount (T x) [C++] |
|
|
666 | |
640 | Returns the number of bits set to 1 in C<x>. |
667 | Returns the number of bits set to 1 in C<x>. |
641 | |
668 | |
642 | For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>. |
669 | For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>. |
|
|
670 | |
|
|
671 | The overloaded C++ C<ecb_popcount> function supports C<uint8_t>, C<uint16_t>, |
|
|
672 | C<uint32_t> and C<uint64_t> types. |
643 | |
673 | |
644 | For example: |
674 | For example: |
645 | |
675 | |
646 | ecb_popcount32 (7) = 3 |
676 | ecb_popcount32 (7) = 3 |
647 | ecb_popcount32 (255) = 8 |
677 | ecb_popcount32 (255) = 8 |
… | |
… | |
650 | |
680 | |
651 | =item uint16_t ecb_bitrev16 (uint16_t x) |
681 | =item uint16_t ecb_bitrev16 (uint16_t x) |
652 | |
682 | |
653 | =item uint32_t ecb_bitrev32 (uint32_t x) |
683 | =item uint32_t ecb_bitrev32 (uint32_t x) |
654 | |
684 | |
|
|
685 | =item T ecb_bitrev (T x) [C++] |
|
|
686 | |
655 | Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1 |
687 | Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1 |
656 | and so on. |
688 | and so on. |
657 | |
689 | |
|
|
690 | The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types. |
|
|
691 | |
658 | Example: |
692 | Example: |
659 | |
693 | |
660 | ecb_bitrev8 (0xa7) = 0xea |
694 | ecb_bitrev8 (0xa7) = 0xea |
661 | ecb_bitrev32 (0xffcc4411) = 0x882233ff |
695 | ecb_bitrev32 (0xffcc4411) = 0x882233ff |
662 | |
696 | |
|
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697 | =item T ecb_bitrev (T x) [C++] |
|
|
698 | |
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|
699 | Overloaded C++ bitrev function. |
|
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700 | |
|
|
701 | C<T> must be one of C<uint8_t>, C<uint16_t> or C<uint32_t>. |
|
|
702 | |
663 | =item uint32_t ecb_bswap16 (uint32_t x) |
703 | =item uint32_t ecb_bswap16 (uint32_t x) |
664 | |
704 | |
665 | =item uint32_t ecb_bswap32 (uint32_t x) |
705 | =item uint32_t ecb_bswap32 (uint32_t x) |
666 | |
706 | |
667 | =item uint64_t ecb_bswap64 (uint64_t x) |
707 | =item uint64_t ecb_bswap64 (uint64_t x) |
|
|
708 | |
|
|
709 | =item T ecb_bswap (T x) |
668 | |
710 | |
669 | These functions return the value of the 16-bit (32-bit, 64-bit) value |
711 | These functions return the value of the 16-bit (32-bit, 64-bit) value |
670 | C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in |
712 | C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in |
671 | C<ecb_bswap32>). |
713 | C<ecb_bswap32>). |
672 | |
714 | |
673 | =item T ecb_bswap (T x) [C++] |
715 | The overloaded C++ C<ecb_bswap> function supports C<uint8_t>, C<uint16_t>, |
674 | |
716 | C<uint32_t> and C<uint64_t> types. |
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 | |
717 | |
678 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
718 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
679 | |
719 | |
680 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
720 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
681 | |
721 | |
… | |
… | |
691 | |
731 | |
692 | =item uint64_t ecb_rotr64 (uint64_t x, unsigned int count) |
732 | =item uint64_t ecb_rotr64 (uint64_t x, unsigned int count) |
693 | |
733 | |
694 | These two families of functions return the value of C<x> after rotating |
734 | These two families of functions return the value of C<x> after rotating |
695 | all the bits by C<count> positions to the right (C<ecb_rotr>) or left |
735 | all the bits by C<count> positions to the right (C<ecb_rotr>) or left |
696 | (C<ecb_rotl>). |
736 | (C<ecb_rotl>). There are no restrictions on the value C<count>, i.e. both |
|
|
737 | zero and values equal or larger than the word width work correctly. |
697 | |
738 | |
698 | Current GCC versions understand these functions and usually compile them |
739 | Current GCC/clang versions understand these functions and usually compile |
699 | to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on |
740 | them to "optimal" code (e.g. a single C<rol> or a combination of C<shld> |
700 | x86). |
741 | on x86). |
|
|
742 | |
|
|
743 | =item T ecb_rotl (T x, unsigned int count) [C++] |
|
|
744 | |
|
|
745 | =item T ecb_rotr (T x, unsigned int count) [C++] |
|
|
746 | |
|
|
747 | Overloaded C++ rotl/rotr functions. |
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|
748 | |
|
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749 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
701 | |
750 | |
702 | =back |
751 | =back |
703 | |
752 | |
704 | =head2 HOST ENDIANNESS CONVERSION |
753 | =head2 HOST ENDIANNESS CONVERSION |
705 | |
754 | |
706 | =over 4 |
755 | =over |
707 | |
756 | |
708 | =item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v) |
757 | =item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v) |
709 | |
758 | |
710 | =item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v) |
759 | =item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v) |
711 | |
760 | |
… | |
… | |
718 | =item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v) |
767 | =item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v) |
719 | |
768 | |
720 | Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order. |
769 | Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order. |
721 | |
770 | |
722 | The naming convention is C<ecb_>(C<be>|C<le>)C<_u>C<16|32|64>C<_to_host>, |
771 | 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. |
772 | where C<be> and C<le> stand for big endian and little endian, respectively. |
724 | |
773 | |
725 | =item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v) |
774 | =item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v) |
726 | |
775 | |
727 | =item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v) |
776 | =item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v) |
728 | |
777 | |
… | |
… | |
737 | Like above, but converts I<from> host byte order to the specified |
786 | Like above, but converts I<from> host byte order to the specified |
738 | endianness. |
787 | endianness. |
739 | |
788 | |
740 | =back |
789 | =back |
741 | |
790 | |
742 | In C++ the following additional functions are supported: |
791 | In C++ the following additional template functions are supported: |
743 | |
792 | |
744 | =over 4 |
793 | =over |
745 | |
794 | |
746 | =item T ecb_be_to_host (T v) |
795 | =item T ecb_be_to_host (T v) |
747 | |
796 | |
748 | =item T ecb_le_to_host (T v) |
797 | =item T ecb_le_to_host (T v) |
749 | |
798 | |
750 | =item T ecb_host_to_be (T v) |
799 | =item T ecb_host_to_be (T v) |
751 | |
800 | |
752 | =item T ecb_host_to_le (T v) |
801 | =item T ecb_host_to_le (T v) |
753 | |
802 | |
|
|
803 | =back |
|
|
804 | |
754 | These work like their C counterparts, above, but use templates for the |
805 | These functions work like their C counterparts, above, but use templates, |
755 | type, which make them useful in generic code. |
806 | which make them useful in generic code. |
756 | |
807 | |
757 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t> |
808 | 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 |
809 | (so unlike their C counterparts, there is a version for C<uint8_t>, which |
759 | again can be useful in generic code). |
810 | again can be useful in generic code). |
760 | |
811 | |
761 | =head2 UNALIGNED LOAD/STORE |
812 | =head2 UNALIGNED LOAD/STORE |
762 | |
813 | |
763 | These function load or store unaligned multi-byte values. |
814 | These function load or store unaligned multi-byte values. |
764 | |
815 | |
765 | =over 4 |
816 | =over |
766 | |
817 | |
767 | =item uint_fast16_t ecb_peek_u16_u (const void *ptr) |
818 | =item uint_fast16_t ecb_peek_u16_u (const void *ptr) |
768 | |
819 | |
769 | =item uint_fast32_t ecb_peek_u32_u (const void *ptr) |
820 | =item uint_fast32_t ecb_peek_u32_u (const void *ptr) |
770 | |
821 | |
… | |
… | |
812 | Like above, but additionally convert from host byte order to big endian |
863 | 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. |
864 | (C<be>) or little endian (C<le>) byte order while doing so. |
814 | |
865 | |
815 | =back |
866 | =back |
816 | |
867 | |
817 | In C++ the following additional functions are supported: |
868 | In C++ the following additional template functions are supported: |
818 | |
869 | |
819 | =over 4 |
870 | =over |
820 | |
871 | |
821 | =item T ecb_peek (const void *ptr) |
872 | =item T ecb_peek<T> (const void *ptr) |
822 | |
873 | |
823 | =item T ecb_peek_be (const void *ptr) |
874 | =item T ecb_peek_be<T> (const void *ptr) |
824 | |
875 | |
825 | =item T ecb_peek_le (const void *ptr) |
876 | =item T ecb_peek_le<T> (const void *ptr) |
826 | |
877 | |
827 | =item T ecb_peek_u (const void *ptr) |
878 | =item T ecb_peek_u<T> (const void *ptr) |
828 | |
879 | |
829 | =item T ecb_peek_be_u (const void *ptr) |
880 | =item T ecb_peek_be_u<T> (const void *ptr) |
830 | |
881 | |
831 | =item T ecb_peek_le_u (const void *ptr) |
882 | =item T ecb_peek_le_u<T> (const void *ptr) |
832 | |
883 | |
833 | Similarly to their C counterparts, these functions load an unsigned 8, 16, |
884 | 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 |
885 | 32 or 64 bit value from memory, with optional conversion from big/little |
835 | endian. |
886 | endian. |
836 | |
887 | |
837 | Since the type cannot be deduced, it has top be specified explicitly, e.g. |
888 | Since the type cannot be deduced, it has to be specified explicitly, e.g. |
838 | |
889 | |
839 | uint_fast16_t v = ecb_peek<uint16_t> (ptr); |
890 | uint_fast16_t v = ecb_peek<uint16_t> (ptr); |
840 | |
891 | |
841 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
892 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
842 | |
893 | |
… | |
… | |
866 | (C<uint8_t>) and also have an aligned version (without the C<_u> prefix), |
917 | (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. |
918 | all of which hopefully makes them more useful in generic code. |
868 | |
919 | |
869 | =back |
920 | =back |
870 | |
921 | |
|
|
922 | =head2 FAST INTEGER TO STRING |
|
|
923 | |
|
|
924 | Libecb defines a set of very fast integer to decimal string (or integer |
|
|
925 | to ascii, short C<i2a>) functions. These work by converting the integer |
|
|
926 | to a fixed point representation and then successively multiplying out |
|
|
927 | the topmost digits. Unlike some other, also very fast, libraries, ecb's |
|
|
928 | algorithm should be completely branchless per digit, and does not rely on |
|
|
929 | the presence of special cpu functions (such as clz). |
|
|
930 | |
|
|
931 | There is a high level API that takes an C<int32_t>, C<uint32_t>, |
|
|
932 | C<int64_t> or C<uint64_t> as argument, and a low-level API, which is |
|
|
933 | harder to use but supports slightly more formatting options. |
|
|
934 | |
|
|
935 | =head3 HIGH LEVEL API |
|
|
936 | |
|
|
937 | The high level API consists of four functions, one each for C<int32_t>, |
|
|
938 | C<uint32_t>, C<int64_t> and C<uint64_t>: |
|
|
939 | |
|
|
940 | Example: |
|
|
941 | |
|
|
942 | char buf[ECB_I2A_MAX_DIGITS + 1]; |
|
|
943 | char *end = ecb_i2a_i32 (buf, 17262); |
|
|
944 | *end = 0; |
|
|
945 | // buf now contains "17262" |
|
|
946 | |
|
|
947 | =over |
|
|
948 | |
|
|
949 | =item ECB_I2A_I32_DIGITS (=11) |
|
|
950 | |
|
|
951 | =item char *ecb_i2a_u32 (char *ptr, uint32_t value) |
|
|
952 | |
|
|
953 | Takes an C<uint32_t> I<value> and formats it as a decimal number starting |
|
|
954 | at I<ptr>, using at most C<ECB_I2A_I32_DIGITS> characters. Returns a |
|
|
955 | pointer to just after the generated string, where you would normally put |
|
|
956 | the terminating C<0> character. This function outputs the minimum number |
|
|
957 | of digits. |
|
|
958 | |
|
|
959 | =item ECB_I2A_U32_DIGITS (=10) |
|
|
960 | |
|
|
961 | =item char *ecb_i2a_i32 (char *ptr, int32_t value) |
|
|
962 | |
|
|
963 | Same as C<ecb_i2a_u32>, but formats a C<int32_t> value, including a minus |
|
|
964 | sign if needed. |
|
|
965 | |
|
|
966 | =item ECB_I2A_I64_DIGITS (=20) |
|
|
967 | |
|
|
968 | =item char *ecb_i2a_u64 (char *ptr, uint64_t value) |
|
|
969 | |
|
|
970 | =item ECB_I2A_U64_DIGITS (=21) |
|
|
971 | |
|
|
972 | =item char *ecb_i2a_i64 (char *ptr, int64_t value) |
|
|
973 | |
|
|
974 | Similar to their 32 bit counterparts, these take a 64 bit argument. |
|
|
975 | |
|
|
976 | =item ECB_I2A_MAX_DIGITS (=21) |
|
|
977 | |
|
|
978 | Instead of using a type specific length macro, youi can just use |
|
|
979 | C<ECB_I2A_MAX_DIGITS>, which is good enough for any C<ecb_i2a> function. |
|
|
980 | |
|
|
981 | =back |
|
|
982 | |
|
|
983 | =head3 LOW-LEVEL API |
|
|
984 | |
|
|
985 | The functions above use a number of low-level APIs which have some strict |
|
|
986 | limitations, but can be used as building blocks (study of C<ecb_i2a_i32> |
|
|
987 | and related functions is recommended). |
|
|
988 | |
|
|
989 | There are three families of functions: functions that convert a number |
|
|
990 | to a fixed number of digits with leading zeroes (C<ecb_i2a_0N>, C<0> |
|
|
991 | for "leading zeroes"), functions that generate up to N digits, skipping |
|
|
992 | leading zeroes (C<_N>), and functions that can generate more digits, but |
|
|
993 | the leading digit has limited range (C<_xN>). |
|
|
994 | |
|
|
995 | None of the functions deal with negative numbers. |
|
|
996 | |
|
|
997 | Example: convert an IP address in an u32 into dotted-quad: |
|
|
998 | |
|
|
999 | uint32_t ip = 0x0a000164; // 10.0.1.100 |
|
|
1000 | char ips[3 * 4 + 3 + 1]; |
|
|
1001 | char *ptr = ips; |
|
|
1002 | ptr = ecb_i2a_3 (ptr, ip >> 24 ); *ptr++ = '.'; |
|
|
1003 | ptr = ecb_i2a_3 (ptr, (ip >> 16) & 0xff); *ptr++ = '.'; |
|
|
1004 | ptr = ecb_i2a_3 (ptr, (ip >> 8) & 0xff); *ptr++ = '.'; |
|
|
1005 | ptr = ecb_i2a_3 (ptr, ip & 0xff); *ptr++ = 0; |
|
|
1006 | printf ("ip: %s\n", ips); // prints "ip: 10.0.1.100" |
|
|
1007 | |
|
|
1008 | =over |
|
|
1009 | |
|
|
1010 | =item char *ecb_i2a_02 (char *ptr, uint32_t value) // 32 bit |
|
|
1011 | |
|
|
1012 | =item char *ecb_i2a_03 (char *ptr, uint32_t value) // 32 bit |
|
|
1013 | |
|
|
1014 | =item char *ecb_i2a_04 (char *ptr, uint32_t value) // 32 bit |
|
|
1015 | |
|
|
1016 | =item char *ecb_i2a_05 (char *ptr, uint32_t value) // 64 bit |
|
|
1017 | |
|
|
1018 | =item char *ecb_i2a_06 (char *ptr, uint32_t value) // 64 bit |
|
|
1019 | |
|
|
1020 | =item char *ecb_i2a_07 (char *ptr, uint32_t value) // 64 bit |
|
|
1021 | |
|
|
1022 | =item char *ecb_i2a_08 (char *ptr, uint32_t value) // 64 bit |
|
|
1023 | |
|
|
1024 | =item char *ecb_i2a_09 (char *ptr, uint32_t value) // 64 bit |
|
|
1025 | |
|
|
1026 | The C<< ecb_i2a_0I<N> > functions take an unsigned I<value> and convert |
|
|
1027 | them to exactly I<N> digits, returning a pointer to the first character |
|
|
1028 | after the digits. The I<value> must be in range. The functions marked with |
|
|
1029 | I<32 bit> do their calculations internally in 32 bit, the ones marked with |
|
|
1030 | I<64 bit> internally use 64 bit integers, which might be slow on 32 bit |
|
|
1031 | architectures (the high level API decides on 32 vs. 64 bit versions using |
|
|
1032 | C<ECB_64BIT_NATIVE>). |
|
|
1033 | |
|
|
1034 | =item char *ecb_i2a_2 (char *ptr, uint32_t value) // 32 bit |
|
|
1035 | |
|
|
1036 | =item char *ecb_i2a_3 (char *ptr, uint32_t value) // 32 bit |
|
|
1037 | |
|
|
1038 | =item char *ecb_i2a_4 (char *ptr, uint32_t value) // 32 bit |
|
|
1039 | |
|
|
1040 | =item char *ecb_i2a_5 (char *ptr, uint32_t value) // 64 bit |
|
|
1041 | |
|
|
1042 | =item char *ecb_i2a_6 (char *ptr, uint32_t value) // 64 bit |
|
|
1043 | |
|
|
1044 | =item char *ecb_i2a_7 (char *ptr, uint32_t value) // 64 bit |
|
|
1045 | |
|
|
1046 | =item char *ecb_i2a_8 (char *ptr, uint32_t value) // 64 bit |
|
|
1047 | |
|
|
1048 | =item char *ecb_i2a_9 (char *ptr, uint32_t value) // 64 bit |
|
|
1049 | |
|
|
1050 | Similarly, the C<< ecb_i2a_I<N> > functions take an unsigned I<value> |
|
|
1051 | and convert them to at most I<N> digits, suppressing leading zeroes, and |
|
|
1052 | returning a pointer to the first character after the digits. |
|
|
1053 | |
|
|
1054 | =item ECB_I2A_MAX_X5 (=59074) |
|
|
1055 | |
|
|
1056 | =item char *ecb_i2a_x5 (char *ptr, uint32_t value) // 32 bit |
|
|
1057 | |
|
|
1058 | =item ECB_I2A_MAX_X10 (=2932500665) |
|
|
1059 | |
|
|
1060 | =item char *ecb_i2a_x10 (char *ptr, uint32_t value) // 64 bit |
|
|
1061 | |
|
|
1062 | The C<< ecb_i2a_xI<N> >> functions are similar to the C<< ecb_i2a_I<N> > |
|
|
1063 | functions, but they can generate one digit more, as long as the number |
|
|
1064 | is within range, which is given by the symbols C<ECB_I2A_MAX_X5> (almost |
|
|
1065 | 16 bit range) and C<ECB_I2A_MAX_X10> (a bit more than 31 bit range), |
|
|
1066 | respectively. |
|
|
1067 | |
|
|
1068 | For example, the digit part of a 32 bit signed integer just fits into the |
|
|
1069 | C<ECB_I2A_MAX_X10> range, so while C<ecb_i2a_x10> cannot convert a 10 |
|
|
1070 | digit number, it can convert all 32 bit signed numbers. Sadly, it's not |
|
|
1071 | good enough for 32 bit unsigned numbers. |
|
|
1072 | |
|
|
1073 | =back |
|
|
1074 | |
871 | =head2 FLOATING POINT FIDDLING |
1075 | =head2 FLOATING POINT FIDDLING |
872 | |
1076 | |
873 | =over 4 |
1077 | =over |
874 | |
1078 | |
875 | =item ECB_INFINITY [-UECB_NO_LIBM] |
1079 | =item ECB_INFINITY [-UECB_NO_LIBM] |
876 | |
1080 | |
877 | Evaluates to positive infinity if supported by the platform, otherwise to |
1081 | Evaluates to positive infinity if supported by the platform, otherwise to |
878 | a truly huge number. |
1082 | a truly huge number. |
… | |
… | |
956 | |
1160 | |
957 | =back |
1161 | =back |
958 | |
1162 | |
959 | =head2 ARITHMETIC |
1163 | =head2 ARITHMETIC |
960 | |
1164 | |
961 | =over 4 |
1165 | =over |
962 | |
1166 | |
963 | =item x = ecb_mod (m, n) |
1167 | =item x = ecb_mod (m, n) |
964 | |
1168 | |
965 | Returns C<m> modulo C<n>, which is the same as the positive remainder |
1169 | Returns C<m> modulo C<n>, which is the same as the positive remainder |
966 | of the division operation between C<m> and C<n>, using floored |
1170 | of the division operation between C<m> and C<n>, using floored |
… | |
… | |
973 | C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be |
1177 | C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be |
974 | negatable, that is, both C<m> and C<-m> must be representable in its |
1178 | negatable, that is, both C<m> and C<-m> must be representable in its |
975 | type (this typically excludes the minimum signed integer value, the same |
1179 | type (this typically excludes the minimum signed integer value, the same |
976 | limitation as for C</> and C<%> in C). |
1180 | limitation as for C</> and C<%> in C). |
977 | |
1181 | |
978 | Current GCC versions compile this into an efficient branchless sequence on |
1182 | Current GCC/clang versions compile this into an efficient branchless |
979 | almost all CPUs. |
1183 | sequence on almost all CPUs. |
980 | |
1184 | |
981 | For example, when you want to rotate forward through the members of an |
1185 | For example, when you want to rotate forward through the members of an |
982 | array for increasing C<m> (which might be negative), then you should use |
1186 | array for increasing C<m> (which might be negative), then you should use |
983 | C<ecb_mod>, as the C<%> operator might give either negative results, or |
1187 | C<ecb_mod>, as the C<%> operator might give either negative results, or |
984 | change direction for negative values: |
1188 | change direction for negative values: |
… | |
… | |
997 | |
1201 | |
998 | =back |
1202 | =back |
999 | |
1203 | |
1000 | =head2 UTILITY |
1204 | =head2 UTILITY |
1001 | |
1205 | |
1002 | =over 4 |
1206 | =over |
1003 | |
1207 | |
1004 | =item element_count = ecb_array_length (name) |
1208 | =item element_count = ecb_array_length (name) |
1005 | |
1209 | |
1006 | Returns the number of elements in the array C<name>. For example: |
1210 | Returns the number of elements in the array C<name>. For example: |
1007 | |
1211 | |
… | |
… | |
1015 | |
1219 | |
1016 | =head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF |
1220 | =head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF |
1017 | |
1221 | |
1018 | These symbols need to be defined before including F<ecb.h> the first time. |
1222 | These symbols need to be defined before including F<ecb.h> the first time. |
1019 | |
1223 | |
1020 | =over 4 |
1224 | =over |
1021 | |
1225 | |
1022 | =item ECB_NO_THREADS |
1226 | =item ECB_NO_THREADS |
1023 | |
1227 | |
1024 | If F<ecb.h> is never used from multiple threads, then this symbol can |
1228 | If F<ecb.h> is never used from multiple threads, then this symbol can |
1025 | be defined, in which case memory fences (and similar constructs) are |
1229 | be defined, in which case memory fences (and similar constructs) are |