[ViewVC] Diff of: cvs/libecb/ecb.pod

Comparing libecb/ecb.pod (file contents):
Revision 1.76 by root, Mon Jan 20 13:13:56 2020 UTC vs.
Revision 1.103 by root, Wed Mar 23 09:59:49 2022 UTC

…		…
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
		115	Note that many C++20 features will likely have their own feature test
		116	macros (see e.g. L<http://eel.is/c++draft/cpp.predefined#1.8>).
		117
		118	=item ECB_OPTIMIZE_SIZE
		119
		120	Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol
		121	can also be defined before including F<ecb.h>, in which case it will be
		122	unchanged.
		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.
		168
		169	=item ECB_64BIT_NATIVE
		170
		171	Evaluates to a true value (suitable for both preprocessor and C code
		172	testing) if 64 bit integer types on this architecture are evaluated
		173	"natively", that is, with similar speeds as 32 bit integers. While 64 bit
		174	integer support is very common (and in fact required by libecb), 32 bit
		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,
…		…
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
…		…
406		422
407	=back	423	=back
408		424
409	=head2 OPTIMISATION HINTS	425	=head2 OPTIMISATION HINTS
410		426
411	=over 4	427	=over
412
413	=item ECB_OPTIMIZE_SIZE
414
415	Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol
416	can also be defined before including F<ecb.h>, in which case it will be
417	unchanged.
418		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>,
		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
		697	=item T ecb_bitrev (T x) [C++]
		698
		699	Overloaded C++ bitrev function.
		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. Also,
		738	notwithstanding C<count> being unsigned, negative numbers work and shift
		739	to the opposite direction.
697		740
698	Current GCC versions understand these functions and usually compile them	741	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	742	them to "optimal" code (e.g. a single C<rol> or a combination of C<shld>
700	x86).	743	on x86).
		744
		745	=item T ecb_rotl (T x, unsigned int count) [C++]
		746
		747	=item T ecb_rotr (T x, unsigned int count) [C++]
		748
		749	Overloaded C++ rotl/rotr functions.
		750
		751	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		752
		753	=item uint_fast8_t ecb_gray8_encode (uint_fast8_t b)
		754
		755	=item uint_fast16_t ecb_gray16_encode (uint_fast16_t b)
		756
		757	=item uint_fast32_t ecb_gray32_encode (uint_fast32_t b)
		758
		759	=item uint_fast64_t ecb_gray64_encode (uint_fast64_t b)
		760
		761	Encode an unsigned into its corresponding (reflective) gray code - the
		762	kind of gray code meant when just talking about "gray code". These
		763	functions are very fast and all have identical implementation, so there is
		764	no need to use a smaller type, as long as your CPU can handle it natively.
		765
		766	=item T ecb_gray_encode (T b) [C++]
		767
		768	Overloaded C++ version of the above, for C<uint{8,16,32,64}_t>.
		769
		770	=item uint_fast8_t ecb_gray8_decode (uint_fast8_t b)
		771
		772	=item uint_fast16_t ecb_gray16_decode (uint_fast16_t b)
		773
		774	=item uint_fast32_t ecb_gray32_decode (uint_fast32_t b)
		775
		776	=item uint_fast64_t ecb_gray64_decode (uint_fast64_t b)
		777
		778	Decode a gray code back into linear index form (the reverse of
		779	C<ecb_gray*_encode>. Unlike the encode functions, the decode functions
		780	have higher time complexity for larger types, so it can pay off to use a
		781	smaller type here.
		782
		783	=item T ecb_gray_decode (T b) [C++]
		784
		785	Overloaded C++ version of the above, for C<uint{8,16,32,64}_t>.
		786
		787	=back
		788
		789	=head2 BIT MIXING, HASHING
		790
		791	Sometimes you have an integer and want to distribute its bits well, for
		792	example, to use it as a hash in a hashtable. A common example is pointer
		793	values, which often only have a limited range (e.g. low and high bits are
		794	often zero).
		795
		796	The following functions try to mix the bits to get a good bias-free
		797	distribution. They were mainly made for pointers, but the underlying
		798	integer functions are exposed as well.
		799
		800	As an added benefit, the functions are reversible, so if you find it
		801	convenient to store only the hash value, you can recover the original
		802	pointer from the hash ("unmix"), as long as your pinters are 32 or 64 bit
		803	(if this isn't the case on your platform, drop us a note and we will add
		804	functions for other bit widths).
		805
		806	The unmix functions are very slightly slower than the mix functions, so
		807	it is equally very slightly preferable to store the original values wehen
		808	convenient.
		809
		810	The underlying algorithm if subject to change, so currently these
		811	functions are not suitable for persistent hash tables, as their result
		812	value can change between diferent versions of libecb.
		813
		814	=over
		815
		816	=item uintptr_t ecb_ptrmix (void *ptr)
		817
		818	Mixes the bits of a pointer so the result is suitable for hash table
		819	lookups. In other words, this hashes the pointer value.
		820
		821	=item uintptr_t ecb_ptrmix (T *ptr) [C++]
		822
		823	Overload the C<ecb_ptrmix> function to work for any pointer in C++.
		824
		825	=item void *ecb_ptrunmix (uintptr_t v)
		826
		827	Unmix the hash value into the original pointer. This only works as long
		828	as the hash value is not truncated, i.e. you used C<uintptr_t> (or
		829	equivalent) throughout to store it.
		830
		831	=item T *ecb_ptrunmix<T> (uintptr_t v) [C++]
		832
		833	The somewhat less useful template version of C<ecb_ptrunmix> for
		834	C++. Example:
		835
		836	sometype *myptr;
		837	uintptr_t hash = ecb_ptrmix (myptr);
		838	sometype *orig = ecb_ptrunmix<sometype> (hash);
		839
		840	=item uint32_t ecb_mix32 (uint32_t v)
		841
		842	=item uint64_t ecb_mix64 (uint64_t v)
		843
		844	Sometimes you don't have a pointer but an integer whose values are very
		845	badly distributed. In this case you cna sue these integer versions of the
		846	mixing function. No C++ template is provided currently.
		847
		848	=item uint32_t ecb_unmix32 (uint32_t v)
		849
		850	=item uint64_t ecb_unmix64 (uint64_t v)
		851
		852	The reverse of the C<ecb_mix> functions - they take a mixed/hashed value
		853	and recover the original value.
701		854
702	=back	855	=back
703		856
704	=head2 HOST ENDIANNESS CONVERSION	857	=head2 HOST ENDIANNESS CONVERSION
705		858
706	=over 4	859	=over
707		860
708	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)	861	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)
709		862
710	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)	863	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)
711		864
…		…
718	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)	871	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)
719		872
720	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.	873	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.
721		874
722	The naming convention is C<ecb_>(C<be>\|C<le>)C<_u>C<16\|32\|64>C<_to_host>,	875	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.	876	where C<be> and C<le> stand for big endian and little endian, respectively.
724		877
725	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)	878	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)
726		879
727	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)	880	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)
728		881
…		…
737	Like above, but converts I<from> host byte order to the specified	890	Like above, but converts I<from> host byte order to the specified
738	endianness.	891	endianness.
739		892
740	=back	893	=back
741		894
742	In C++ the following additional functions are supported:	895	In C++ the following additional template functions are supported:
743		896
744	=over 4	897	=over
745		898
746	=item T ecb_be_to_host (T v)	899	=item T ecb_be_to_host (T v)
747		900
748	=item T ecb_le_to_host (T v)	901	=item T ecb_le_to_host (T v)
749		902
750	=item T ecb_host_to_be (T v)	903	=item T ecb_host_to_be (T v)
751		904
752	=item T ecb_host_to_le (T v)	905	=item T ecb_host_to_le (T v)
753		906
		907	=back
		908
754	These work like their C counterparts, above, but use templates for the	909	These functions work like their C counterparts, above, but use templates,
755	type, which make them useful in generic code.	910	which make them useful in generic code.
756		911
757	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>	912	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	913	(so unlike their C counterparts, there is a version for C<uint8_t>, which
759	again can be useful in generic code).	914	again can be useful in generic code).
760		915
761	=head2 UNALIGNED LOAD/STORE	916	=head2 UNALIGNED LOAD/STORE
762		917
763	These function load or store unaligned multi-byte values.	918	These function load or store unaligned multi-byte values.
764		919
765	=over 4	920	=over
766		921
767	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)	922	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)
768		923
769	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)	924	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)
770		925
…		…
812	Like above, but additionally convert from host byte order to big endian	967	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.	968	(C<be>) or little endian (C<le>) byte order while doing so.
814		969
815	=back	970	=back
816		971
817	In C++ the following additional functions are supported:	972	In C++ the following additional template functions are supported:
818		973
819	=over 4	974	=over
820		975
821	=item T ecb_peek (const void *ptr)	976	=item T ecb_peek<T> (const void *ptr)
822		977
823	=item T ecb_peek_be (const void *ptr)	978	=item T ecb_peek_be<T> (const void *ptr)
824		979
825	=item T ecb_peek_le (const void *ptr)	980	=item T ecb_peek_le<T> (const void *ptr)
826		981
827	=item T ecb_peek_u (const void *ptr)	982	=item T ecb_peek_u<T> (const void *ptr)
828		983
829	=item T ecb_peek_be_u (const void *ptr)	984	=item T ecb_peek_be_u<T> (const void *ptr)
830		985
831	=item T ecb_peek_le_u (const void *ptr)	986	=item T ecb_peek_le_u<T> (const void *ptr)
832		987
833	Similarly to their C counterparts, these functions load an unsigned 8, 16,	988	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	989	32 or 64 bit value from memory, with optional conversion from big/little
835	endian.	990	endian.
836		991
837	Since the type cannot be deduced, it has top be specified explicitly, e.g.	992	Since the type cannot be deduced, it has to be specified explicitly, e.g.
838		993
839	uint_fast16_t v = ecb_peek<uint16_t> (ptr);	994	uint_fast16_t v = ecb_peek<uint16_t> (ptr);
840		995
841	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.	996	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
842		997
…		…
866	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),	1021	(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.	1022	all of which hopefully makes them more useful in generic code.
868		1023
869	=back	1024	=back
870		1025
		1026	=head2 FAST INTEGER TO STRING
		1027
		1028	Libecb defines a set of very fast integer to decimal string (or integer
		1029	to ascii, short C<i2a>) functions. These work by converting the integer
		1030	to a fixed point representation and then successively multiplying out
		1031	the topmost digits. Unlike some other, also very fast, libraries, ecb's
		1032	algorithm should be completely branchless per digit, and does not rely on
		1033	the presence of special cpu functions (such as clz).
		1034
		1035	There is a high level API that takes an C<int32_t>, C<uint32_t>,
		1036	C<int64_t> or C<uint64_t> as argument, and a low-level API, which is
		1037	harder to use but supports slightly more formatting options.
		1038
		1039	=head3 HIGH LEVEL API
		1040
		1041	The high level API consists of four functions, one each for C<int32_t>,
		1042	C<uint32_t>, C<int64_t> and C<uint64_t>:
		1043
		1044	Example:
		1045
		1046	char buf[ECB_I2A_MAX_DIGITS + 1];
		1047	char *end = ecb_i2a_i32 (buf, 17262);
		1048	*end = 0;
		1049	// buf now contains "17262"
		1050
		1051	=over
		1052
		1053	=item ECB_I2A_I32_DIGITS (=11)
		1054
		1055	=item char ecb_i2a_u32 (char ptr, uint32_t value)
		1056
		1057	Takes an C<uint32_t> I<value> and formats it as a decimal number starting
		1058	at I<ptr>, using at most C<ECB_I2A_I32_DIGITS> characters. Returns a
		1059	pointer to just after the generated string, where you would normally put
		1060	the terminating C<0> character. This function outputs the minimum number
		1061	of digits.
		1062
		1063	=item ECB_I2A_U32_DIGITS (=10)
		1064
		1065	=item char ecb_i2a_i32 (char ptr, int32_t value)
		1066
		1067	Same as C<ecb_i2a_u32>, but formats a C<int32_t> value, including a minus
		1068	sign if needed.
		1069
		1070	=item ECB_I2A_I64_DIGITS (=20)
		1071
		1072	=item char ecb_i2a_u64 (char ptr, uint64_t value)
		1073
		1074	=item ECB_I2A_U64_DIGITS (=21)
		1075
		1076	=item char ecb_i2a_i64 (char ptr, int64_t value)
		1077
		1078	Similar to their 32 bit counterparts, these take a 64 bit argument.
		1079
		1080	=item ECB_I2A_MAX_DIGITS (=21)
		1081
		1082	Instead of using a type specific length macro, you can just use
		1083	C<ECB_I2A_MAX_DIGITS>, which is good enough for any C<ecb_i2a> function.
		1084
		1085	=back
		1086
		1087	=head3 LOW-LEVEL API
		1088
		1089	The functions above use a number of low-level APIs which have some strict
		1090	limitations, but can be used as building blocks (studying C<ecb_i2a_i32>
		1091	and related functions is recommended).
		1092
		1093	There are three families of functions: functions that convert a number
		1094	to a fixed number of digits with leading zeroes (C<ecb_i2a_0N>, C<0>
		1095	for "leading zeroes"), functions that generate up to N digits, skipping
		1096	leading zeroes (C<_N>), and functions that can generate more digits, but
		1097	the leading digit has limited range (C<_xN>).
		1098
		1099	None of the functions deal with negative numbers.
		1100
		1101	Example: convert an IP address in an u32 into dotted-quad:
		1102
		1103	uint32_t ip = 0x0a000164; // 10.0.1.100
		1104	char ips[3 * 4 + 3 + 1];
		1105	char *ptr = ips;
		1106	ptr = ecb_i2a_3 (ptr, ip >> 24 ); *ptr++ = '.';
		1107	ptr = ecb_i2a_3 (ptr, (ip >> 16) & 0xff); *ptr++ = '.';
		1108	ptr = ecb_i2a_3 (ptr, (ip >> 8) & 0xff); *ptr++ = '.';
		1109	ptr = ecb_i2a_3 (ptr, ip & 0xff); *ptr++ = 0;
		1110	printf ("ip: %s\n", ips); // prints "ip: 10.0.1.100"
		1111
		1112	=over
		1113
		1114	=item char ecb_i2a_02 (char ptr, uint32_t value) // 32 bit
		1115
		1116	=item char ecb_i2a_03 (char ptr, uint32_t value) // 32 bit
		1117
		1118	=item char ecb_i2a_04 (char ptr, uint32_t value) // 32 bit
		1119
		1120	=item char ecb_i2a_05 (char ptr, uint32_t value) // 64 bit
		1121
		1122	=item char ecb_i2a_06 (char ptr, uint32_t value) // 64 bit
		1123
		1124	=item char ecb_i2a_07 (char ptr, uint32_t value) // 64 bit
		1125
		1126	=item char ecb_i2a_08 (char ptr, uint32_t value) // 64 bit
		1127
		1128	=item char ecb_i2a_09 (char ptr, uint32_t value) // 64 bit
		1129
		1130	The C<< ecb_i2a_0I<N> >> functions take an unsigned I<value> and convert
		1131	them to exactly I<N> digits, returning a pointer to the first character
		1132	after the digits. The I<value> must be in range. The functions marked with
		1133	I<32 bit> do their calculations internally in 32 bit, the ones marked with
		1134	I<64 bit> internally use 64 bit integers, which might be slow on 32 bit
		1135	architectures (the high level API decides on 32 vs. 64 bit versions using
		1136	C<ECB_64BIT_NATIVE>).
		1137
		1138	=item char ecb_i2a_2 (char ptr, uint32_t value) // 32 bit
		1139
		1140	=item char ecb_i2a_3 (char ptr, uint32_t value) // 32 bit
		1141
		1142	=item char ecb_i2a_4 (char ptr, uint32_t value) // 32 bit
		1143
		1144	=item char ecb_i2a_5 (char ptr, uint32_t value) // 64 bit
		1145
		1146	=item char ecb_i2a_6 (char ptr, uint32_t value) // 64 bit
		1147
		1148	=item char ecb_i2a_7 (char ptr, uint32_t value) // 64 bit
		1149
		1150	=item char ecb_i2a_8 (char ptr, uint32_t value) // 64 bit
		1151
		1152	=item char ecb_i2a_9 (char ptr, uint32_t value) // 64 bit
		1153
		1154	Similarly, the C<< ecb_i2a_I<N> >> functions take an unsigned I<value>
		1155	and convert them to at most I<N> digits, suppressing leading zeroes, and
		1156	returning a pointer to the first character after the digits.
		1157
		1158	=item ECB_I2A_MAX_X5 (=59074)
		1159
		1160	=item char ecb_i2a_x5 (char ptr, uint32_t value) // 32 bit
		1161
		1162	=item ECB_I2A_MAX_X10 (=2932500665)
		1163
		1164	=item char ecb_i2a_x10 (char ptr, uint32_t value) // 64 bit
		1165
		1166	The C<< ecb_i2a_xI<N> >> functions are similar to the C<< ecb_i2a_I<N> >>
		1167	functions, but they can generate one digit more, as long as the number
		1168	is within range, which is given by the symbols C<ECB_I2A_MAX_X5> (almost
		1169	16 bit range) and C<ECB_I2A_MAX_X10> (a bit more than 31 bit range),
		1170	respectively.
		1171
		1172	For example, the digit part of a 32 bit signed integer just fits into the
		1173	C<ECB_I2A_MAX_X10> range, so while C<ecb_i2a_x10> cannot convert a 10
		1174	digit number, it can convert all 32 bit signed numbers. Sadly, it's not
		1175	good enough for 32 bit unsigned numbers.
		1176
		1177	=back
		1178
871	=head2 FLOATING POINT FIDDLING	1179	=head2 FLOATING POINT FIDDLING
872		1180
873	=over 4	1181	=over
874		1182
875	=item ECB_INFINITY [-UECB_NO_LIBM]	1183	=item ECB_INFINITY [-UECB_NO_LIBM]
876		1184
877	Evaluates to positive infinity if supported by the platform, otherwise to	1185	Evaluates to positive infinity if supported by the platform, otherwise to
878	a truly huge number.	1186	a truly huge number.
…		…
903	IEEE compliant, of course at a speed and code size penalty, and of course	1211	IEEE compliant, of course at a speed and code size penalty, and of course
904	also within reasonable limits (it tries to convert NaNs, infinities and	1212	also within reasonable limits (it tries to convert NaNs, infinities and
905	denormals, but will likely convert negative zero to positive zero).	1213	denormals, but will likely convert negative zero to positive zero).
906		1214
907	On all modern platforms (where C<ECB_STDFP> is true), the compiler should	1215	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
908	be able to optimise away this function completely.	1216	be able to completely optimise away the 32 and 64 bit functions.
909		1217
910	These functions can be helpful when serialising floats to the network - you	1218	These functions can be helpful when serialising floats to the network - you
911	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.	1219	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
912		1220
913	Another use for these functions is to manipulate floating point values	1221	Another use for these functions is to manipulate floating point values
…		…
956		1264
957	=back	1265	=back
958		1266
959	=head2 ARITHMETIC	1267	=head2 ARITHMETIC
960		1268
961	=over 4	1269	=over
962		1270
963	=item x = ecb_mod (m, n)	1271	=item x = ecb_mod (m, n)
964		1272
965	Returns C<m> modulo C<n>, which is the same as the positive remainder	1273	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	1274	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	1281	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	1282	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	1283	type (this typically excludes the minimum signed integer value, the same
976	limitation as for C</> and C<%> in C).	1284	limitation as for C</> and C<%> in C).
977		1285
978	Current GCC versions compile this into an efficient branchless sequence on	1286	Current GCC/clang versions compile this into an efficient branchless
979	almost all CPUs.	1287	sequence on almost all CPUs.
980		1288
981	For example, when you want to rotate forward through the members of an	1289	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	1290	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	1291	C<ecb_mod>, as the C<%> operator might give either negative results, or
984	change direction for negative values:	1292	change direction for negative values:
…		…
997		1305
998	=back	1306	=back
999		1307
1000	=head2 UTILITY	1308	=head2 UTILITY
1001		1309
1002	=over 4	1310	=over
1003		1311
1004	=item element_count = ecb_array_length (name)	1312	=item element_count = ecb_array_length (name)
1005		1313
1006	Returns the number of elements in the array C<name>. For example:	1314	Returns the number of elements in the array C<name>. For example:
1007		1315
…		…
1015		1323
1016	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF	1324	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF
1017		1325
1018	These symbols need to be defined before including F<ecb.h> the first time.	1326	These symbols need to be defined before including F<ecb.h> the first time.
1019		1327
1020	=over 4	1328	=over
1021		1329
1022	=item ECB_NO_THREADS	1330	=item ECB_NO_THREADS
1023		1331
1024	If F<ecb.h> is never used from multiple threads, then this symbol can	1332	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	1333	be defined, in which case memory fences (and similar constructs) are
…		…
1049	intended to be internal-use only, some of which we forgot to document, and	1357	intended to be internal-use only, some of which we forgot to document, and
1050	some of which we hide because we are not sure we will keep the interface	1358	some of which we hide because we are not sure we will keep the interface
1051	stable.	1359	stable.
1052		1360
1053	While you are welcome to rummage around and use whatever you find useful	1361	While you are welcome to rummage around and use whatever you find useful
1054	(we can't stop you), keep in mind that we will change undocumented	1362	(we don't want to stop you), keep in mind that we will change undocumented
1055	functionality in incompatible ways without thinking twice, while we are	1363	functionality in incompatible ways without thinking twice, while we are
1056	considerably more conservative with documented things.	1364	considerably more conservative with documented things.
1057		1365
1058	=head1 AUTHORS	1366	=head1 AUTHORS
1059		1367
1060	C<libecb> is designed and maintained by:	1368	C<libecb> is designed and maintained by:
1061		1369
1062	Emanuele Giaquinta <e.giaquinta@glauco.it>	1370	Emanuele Giaquinta <e.giaquinta@glauco.it>
1063	Marc Alexander Lehmann <schmorp@schmorp.de>	1371	Marc Alexander Lehmann <schmorp@schmorp.de>
1064
1065

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Comparing libecb/ecb.pod (file contents): Revision 1.76 by root, Mon Jan 20 13:13:56 2020 UTC vs. Revision 1.103 by root, Wed Mar 23 09:59:49 2022 UTC

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Comparing libecb/ecb.pod (file contents):
Revision 1.76 by root, Mon Jan 20 13:13:56 2020 UTC vs.
Revision 1.103 by root, Wed Mar 23 09:59:49 2022 UTC