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

Comparing libecb/ecb.pod (file contents):
Revision 1.65 by root, Thu Feb 19 15:45:29 2015 UTC vs.
Revision 1.101 by root, Mon Nov 22 17:15:50 2021 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
…		…
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
77	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).
78		84
79	=over 4	85	=over
80		86
81	=item ECB_C	87	=item ECB_C
82		88
83	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,
84	while not claiming to be C++.	90	while not claiming to be C++, i..e C, but not C++.
85		91
86	=item ECB_C99	92	=item ECB_C99
87		93
88	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
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.
		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.
108		123
109	=item ECB_GCC_VERSION (major, minor)	124	=item ECB_GCC_VERSION (major, minor)
110		125
111	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
112	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.
113	higher.
114		128
115	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
116	compatible but aren't.	130	compatible but aren't.
117		131
118	=item ECB_EXTERN_C	132	=item ECB_EXTERN_C
…		…
137		151
138	ECB_EXTERN_C_END	152	ECB_EXTERN_C_END
139		153
140	=item ECB_STDFP	154	=item ECB_STDFP
141		155
142	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
143	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
144	and double/binary64 representations internally I<and> the endianness of	158	and double/binary64 representations internally I<and> the endianness of
145	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>.
146		160
147	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
…		…
149	without having to think about format or endianness.	163	without having to think about format or endianness.
150		164
151	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
152	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
153	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.
154		176
155	=item ECB_AMD64, ECB_AMD64_X32	177	=item ECB_AMD64, ECB_AMD64_X32
156		178
157	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
158	ABI, respectively, and undefined elsewhere.	180	ABI, respectively, and undefined elsewhere.
…		…
165		187
166	=back	188	=back
167		189
168	=head2 MACRO TRICKERY	190	=head2 MACRO TRICKERY
169		191
170	=over 4	192	=over
171		193
172	=item ECB_CONCAT (a, b)	194	=item ECB_CONCAT (a, b)
173		195
174	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
175	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,
…		…
216	declarations must be put before the whole declaration:	238	declarations must be put before the whole declaration:
217		239
218	ecb_const int mysqrt (int a);	240	ecb_const int mysqrt (int a);
219	ecb_unused int i;	241	ecb_unused int i;
220		242
221	=over 4	243	=over
222		244
223	=item ecb_unused	245	=item ecb_unused
224		246
225	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
226	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
227	declare a variable but do not always use it:	249	you e.g. declare a variable but do not always use it:
228		250
229	{	251	{
230	ecb_unused int var;	252	ecb_unused int var;
231		253
232	#ifdef SOMECONDITION	254	#ifdef SOMECONDITION
…		…
242	Similar to C<ecb_unused>, but marks a function, variable or type as	264	Similar to C<ecb_unused>, but marks a function, variable or type as
243	deprecated. This makes some compilers warn when the type is used.	265	deprecated. This makes some compilers warn when the type is used.
244		266
245	=item ecb_deprecated_message (message)	267	=item ecb_deprecated_message (message)
246		268
247	Same as C<ecb_deprecated>, but if possible, supply a diagnostic that is	269	Same as C<ecb_deprecated>, but if possible, the specified diagnostic is
248	used instead of a generic depreciation message when the object is being	270	used instead of a generic depreciation message when the object is being
249	used.	271	used.
250		272
251	=item ecb_inline	273	=item ecb_inline
252		274
253	Expands either to C<static inline> or to just C<static>, if inline	275	Expands either to (a compiler-specific equivalent of) C<static inline> or
254	isn't supported. It should be used to declare functions that should be	276	to just C<static>, if inline isn't supported. It should be used to declare
255	inlined, for code size or speed reasons.	277	functions that should be inlined, for code size or speed reasons.
256		278
257	Example: inline this function, it surely will reduce codesize.	279	Example: inline this function, it surely will reduce codesize.
258		280
259	ecb_inline int	281	ecb_inline int
260	negmul (int a, int b)	282	negmul (int a, int b)
…		…
262	return - (a * b);	284	return - (a * b);
263	}	285	}
264		286
265	=item ecb_noinline	287	=item ecb_noinline
266		288
267	Prevent a function from being inlined - it might be optimised away, but	289	Prevents a function from being inlined - it might be optimised away, but
268	not inlined into other functions. This is useful if you know your function	290	not inlined into other functions. This is useful if you know your function
269	is rarely called and large enough for inlining not to be helpful.	291	is rarely called and large enough for inlining not to be helpful.
270		292
271	=item ecb_noreturn	293	=item ecb_noreturn
272		294
…		…
400		422
401	=back	423	=back
402		424
403	=head2 OPTIMISATION HINTS	425	=head2 OPTIMISATION HINTS
404		426
405	=over 4	427	=over
406		428
407	=item bool ecb_is_constant (expr)	429	=item bool ecb_is_constant (expr)
408		430
409	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
410	constant, and false otherwise.	432	constant, and false otherwise.
…		…
489	real_reserve_method (size); /* presumably noinline */	511	real_reserve_method (size); /* presumably noinline */
490	}	512	}
491		513
492	=item ecb_assume (cond)	514	=item ecb_assume (cond)
493		515
494	Try to tell the compiler that some condition is true, even if it's not	516	Tries to tell the compiler that some condition is true, even if it's not
495	obvious. This is not a function, but a statement: it cannot be used in	517	obvious. This is not a function, but a statement: it cannot be used in
496	another expression.	518	another expression.
497		519
498	This can be used to teach the compiler about invariants or other	520	This can be used to teach the compiler about invariants or other
499	conditions that might improve code generation, but which are impossible to	521	conditions that might improve code generation, but which are impossible to
…		…
567		589
568	=back	590	=back
569		591
570	=head2 BIT FIDDLING / BIT WIZARDRY	592	=head2 BIT FIDDLING / BIT WIZARDRY
571		593
572	=over 4	594	=over
573		595
574	=item bool ecb_big_endian ()	596	=item bool ecb_big_endian ()
575		597
576	=item bool ecb_little_endian ()	598	=item bool ecb_little_endian ()
577		599
…		…
583		605
584	=item int ecb_ctz32 (uint32_t x)	606	=item int ecb_ctz32 (uint32_t x)
585		607
586	=item int ecb_ctz64 (uint64_t x)	608	=item int ecb_ctz64 (uint64_t x)
587		609
		610	=item int ecb_ctz (T x) [C++]
		611
588	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
589	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
590	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.
591		615
592	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>.
593		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
594	For example:	621	For example:
595		622
596	ecb_ctz32 (3) = 0	623	ecb_ctz32 (3) = 0
597	ecb_ctz32 (6) = 1	624	ecb_ctz32 (6) = 1
598		625
599	=item bool ecb_is_pot32 (uint32_t x)	626	=item bool ecb_is_pot32 (uint32_t x)
600		627
601	=item bool ecb_is_pot64 (uint32_t x)	628	=item bool ecb_is_pot64 (uint32_t x)
602		629
		630	=item bool ecb_is_pot (T x) [C++]
		631
603	Return 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>.
604		633
605	For smaller types then 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>.
		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.
606		638
607	=item int ecb_ld32 (uint32_t x)	639	=item int ecb_ld32 (uint32_t x)
608		640
609	=item int ecb_ld64 (uint64_t x)	641	=item int ecb_ld64 (uint64_t x)
		642
		643	=item int ecb_ld64 (T x) [C++]
610		644
611	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
612	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 <
613	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
614	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
…		…
619	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
620	itself requires.	654	itself requires.
621		655
622	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>.
623		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
624	=item int ecb_popcount32 (uint32_t x)	661	=item int ecb_popcount32 (uint32_t x)
625		662
626	=item int ecb_popcount64 (uint64_t x)	663	=item int ecb_popcount64 (uint64_t x)
627		664
		665	=item int ecb_popcount (T x) [C++]
		666
628	Returns the number of bits set to 1 in C<x>.	667	Returns the number of bits set to 1 in C<x>.
629		668
630	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.
631		673
632	For example:	674	For example:
633		675
634	ecb_popcount32 (7) = 3	676	ecb_popcount32 (7) = 3
635	ecb_popcount32 (255) = 8	677	ecb_popcount32 (255) = 8
…		…
638		680
639	=item uint16_t ecb_bitrev16 (uint16_t x)	681	=item uint16_t ecb_bitrev16 (uint16_t x)
640		682
641	=item uint32_t ecb_bitrev32 (uint32_t x)	683	=item uint32_t ecb_bitrev32 (uint32_t x)
642		684
		685	=item T ecb_bitrev (T x) [C++]
		686
643	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
644	and so on.	688	and so on.
645		689
		690	The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types.
		691
646	Example:	692	Example:
647		693
648	ecb_bitrev8 (0xa7) = 0xea	694	ecb_bitrev8 (0xa7) = 0xea
649	ecb_bitrev32 (0xffcc4411) = 0x882233ff	695	ecb_bitrev32 (0xffcc4411) = 0x882233ff
650		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
651	=item uint32_t ecb_bswap16 (uint32_t x)	703	=item uint32_t ecb_bswap16 (uint32_t x)
652		704
653	=item uint32_t ecb_bswap32 (uint32_t x)	705	=item uint32_t ecb_bswap32 (uint32_t x)
654		706
655	=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)
656		710
657	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
658	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
659	C<ecb_bswap32>).	713	C<ecb_bswap32>).
660		714
		715	The overloaded C++ C<ecb_bswap> function supports C<uint8_t>, C<uint16_t>,
		716	C<uint32_t> and C<uint64_t> types.
		717
661	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)	718	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
662		719
663	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)	720	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
664		721
665	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	722	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
…		…
674		731
675	=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)	732	=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)
676		733
677	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
678	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
679	(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.
680		740
681	Current GCC versions understand these functions and usually compile them	741	Current GCC/clang versions understand these functions and usually compile
682	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>
683	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	=back
		754
		755	=head2 BIT MIXING, HASHING
		756
		757	Sometimes you have an integer and want to distribute its bits well, for
		758	example, to use it as a hash in a hashtable. A common example is pointer
		759	values, which often only have a limited range (e.g. low and high bits are
		760	often zero).
		761
		762	The following functions try to mix the bits to get a good bias-free
		763	distribution. They were mainly made for pointers, but the underlying
		764	integer functions are exposed as well.
		765
		766	As an added benefit, the functions are reversible, so if you find it
		767	convenient to store only the hash value, you can recover the original
		768	pointer from the hash ("unmix"), as long as your pinters are 32 or 64 bit
		769	(if this isn't the case on your platform, drop us a note and we will add
		770	functions for other bit widths).
		771
		772	The unmix functions are very slightly slower than the mix functions, so
		773	it is equally very slightly preferable to store the original values wehen
		774	convenient.
		775
		776	The underlying algorithm if subject to change, so currently these
		777	functions are not suitable for persistent hash tables, as their result
		778	value can change between diferent versions of libecb.
		779
		780	=over
		781
		782	=item uintptr_t ecb_ptrmix (void *ptr)
		783
		784	Mixes the bits of a pointer so the result is suitable for hash table
		785	lookups. In other words, this hashes the pointer value.
		786
		787	=item uintptr_t ecb_ptrmix (T *ptr) [C++]
		788
		789	Overload the C<ecb_ptrmix> function to work for any pointer in C++.
		790
		791	=item void *ecb_ptrunmix (uintptr_t v)
		792
		793	Unmix the hash value into the original pointer. This only works as long
		794	as the hash value is not truncated, i.e. you used C<uintptr_t> (or
		795	equivalent) throughout to store it.
		796
		797	=item T *ecb_ptrunmix<T> (uintptr_t v) [C++]
		798
		799	The somewhat less useful template version of C<ecb_ptrunmix> for
		800	C++. Example:
		801
		802	sometype *myptr;
		803	uintptr_t hash = ecb_ptrmix (myptr);
		804	sometype *orig = ecb_ptrunmix<sometype> (hash);
		805
		806	=item uint32_t ecb_mix32 (uint32_t v)
		807
		808	=item uint64_t ecb_mix64 (uint64_t v)
		809
		810	Sometimes you don't have a pointer but an integer whose values are very
		811	badly distributed. In this case you cna sue these integer versions of the
		812	mixing function. No C++ template is provided currently.
		813
		814	=item uint32_t ecb_unmix32 (uint32_t v)
		815
		816	=item uint64_t ecb_unmix64 (uint64_t v)
		817
		818	The reverse of the C<ecb_mix> functions - they take a mixed/hashed value
		819	and recover the original value.
		820
		821	=back
		822
		823	=head2 HOST ENDIANNESS CONVERSION
		824
		825	=over
		826
		827	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)
		828
		829	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)
		830
		831	=item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v)
		832
		833	=item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v)
		834
		835	=item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v)
		836
		837	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)
		838
		839	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.
		840
		841	The naming convention is C<ecb_>(C<be>\|C<le>)C<_u>C<16\|32\|64>C<_to_host>,
		842	where C<be> and C<le> stand for big endian and little endian, respectively.
		843
		844	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)
		845
		846	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)
		847
		848	=item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v)
		849
		850	=item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v)
		851
		852	=item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v)
		853
		854	=item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v)
		855
		856	Like above, but converts I<from> host byte order to the specified
		857	endianness.
		858
		859	=back
		860
		861	In C++ the following additional template functions are supported:
		862
		863	=over
		864
		865	=item T ecb_be_to_host (T v)
		866
		867	=item T ecb_le_to_host (T v)
		868
		869	=item T ecb_host_to_be (T v)
		870
		871	=item T ecb_host_to_le (T v)
		872
		873	=back
		874
		875	These functions work like their C counterparts, above, but use templates,
		876	which make them useful in generic code.
		877
		878	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>
		879	(so unlike their C counterparts, there is a version for C<uint8_t>, which
		880	again can be useful in generic code).
		881
		882	=head2 UNALIGNED LOAD/STORE
		883
		884	These function load or store unaligned multi-byte values.
		885
		886	=over
		887
		888	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)
		889
		890	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)
		891
		892	=item uint_fast64_t ecb_peek_u64_u (const void *ptr)
		893
		894	These functions load an unaligned, unsigned 16, 32 or 64 bit value from
		895	memory.
		896
		897	=item uint_fast16_t ecb_peek_be_u16_u (const void *ptr)
		898
		899	=item uint_fast32_t ecb_peek_be_u32_u (const void *ptr)
		900
		901	=item uint_fast64_t ecb_peek_be_u64_u (const void *ptr)
		902
		903	=item uint_fast16_t ecb_peek_le_u16_u (const void *ptr)
		904
		905	=item uint_fast32_t ecb_peek_le_u32_u (const void *ptr)
		906
		907	=item uint_fast64_t ecb_peek_le_u64_u (const void *ptr)
		908
		909	Like above, but additionally convert from big endian (C<be>) or little
		910	endian (C<le>) byte order to host byte order while doing so.
		911
		912	=item ecb_poke_u16_u (void *ptr, uint16_t v)
		913
		914	=item ecb_poke_u32_u (void *ptr, uint32_t v)
		915
		916	=item ecb_poke_u64_u (void *ptr, uint64_t v)
		917
		918	These functions store an unaligned, unsigned 16, 32 or 64 bit value to
		919	memory.
		920
		921	=item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v)
		922
		923	=item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v)
		924
		925	=item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v)
		926
		927	=item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v)
		928
		929	=item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v)
		930
		931	=item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v)
		932
		933	Like above, but additionally convert from host byte order to big endian
		934	(C<be>) or little endian (C<le>) byte order while doing so.
		935
		936	=back
		937
		938	In C++ the following additional template functions are supported:
		939
		940	=over
		941
		942	=item T ecb_peek<T> (const void *ptr)
		943
		944	=item T ecb_peek_be<T> (const void *ptr)
		945
		946	=item T ecb_peek_le<T> (const void *ptr)
		947
		948	=item T ecb_peek_u<T> (const void *ptr)
		949
		950	=item T ecb_peek_be_u<T> (const void *ptr)
		951
		952	=item T ecb_peek_le_u<T> (const void *ptr)
		953
		954	Similarly to their C counterparts, these functions load an unsigned 8, 16,
		955	32 or 64 bit value from memory, with optional conversion from big/little
		956	endian.
		957
		958	Since the type cannot be deduced, it has to be specified explicitly, e.g.
		959
		960	uint_fast16_t v = ecb_peek<uint16_t> (ptr);
		961
		962	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		963
		964	Unlike their C counterparts, these functions support 8 bit quantities
		965	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		966	all of which hopefully makes them more useful in generic code.
		967
		968	=item ecb_poke (void *ptr, T v)
		969
		970	=item ecb_poke_be (void *ptr, T v)
		971
		972	=item ecb_poke_le (void *ptr, T v)
		973
		974	=item ecb_poke_u (void *ptr, T v)
		975
		976	=item ecb_poke_be_u (void *ptr, T v)
		977
		978	=item ecb_poke_le_u (void *ptr, T v)
		979
		980	Again, similarly to their C counterparts, these functions store an
		981	unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to
		982	big/little endian.
		983
		984	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		985
		986	Unlike their C counterparts, these functions support 8 bit quantities
		987	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		988	all of which hopefully makes them more useful in generic code.
		989
		990	=back
		991
		992	=head2 FAST INTEGER TO STRING
		993
		994	Libecb defines a set of very fast integer to decimal string (or integer
		995	to ascii, short C<i2a>) functions. These work by converting the integer
		996	to a fixed point representation and then successively multiplying out
		997	the topmost digits. Unlike some other, also very fast, libraries, ecb's
		998	algorithm should be completely branchless per digit, and does not rely on
		999	the presence of special cpu functions (such as clz).
		1000
		1001	There is a high level API that takes an C<int32_t>, C<uint32_t>,
		1002	C<int64_t> or C<uint64_t> as argument, and a low-level API, which is
		1003	harder to use but supports slightly more formatting options.
		1004
		1005	=head3 HIGH LEVEL API
		1006
		1007	The high level API consists of four functions, one each for C<int32_t>,
		1008	C<uint32_t>, C<int64_t> and C<uint64_t>:
		1009
		1010	Example:
		1011
		1012	char buf[ECB_I2A_MAX_DIGITS + 1];
		1013	char *end = ecb_i2a_i32 (buf, 17262);
		1014	*end = 0;
		1015	// buf now contains "17262"
		1016
		1017	=over
		1018
		1019	=item ECB_I2A_I32_DIGITS (=11)
		1020
		1021	=item char ecb_i2a_u32 (char ptr, uint32_t value)
		1022
		1023	Takes an C<uint32_t> I<value> and formats it as a decimal number starting
		1024	at I<ptr>, using at most C<ECB_I2A_I32_DIGITS> characters. Returns a
		1025	pointer to just after the generated string, where you would normally put
		1026	the terminating C<0> character. This function outputs the minimum number
		1027	of digits.
		1028
		1029	=item ECB_I2A_U32_DIGITS (=10)
		1030
		1031	=item char ecb_i2a_i32 (char ptr, int32_t value)
		1032
		1033	Same as C<ecb_i2a_u32>, but formats a C<int32_t> value, including a minus
		1034	sign if needed.
		1035
		1036	=item ECB_I2A_I64_DIGITS (=20)
		1037
		1038	=item char ecb_i2a_u64 (char ptr, uint64_t value)
		1039
		1040	=item ECB_I2A_U64_DIGITS (=21)
		1041
		1042	=item char ecb_i2a_i64 (char ptr, int64_t value)
		1043
		1044	Similar to their 32 bit counterparts, these take a 64 bit argument.
		1045
		1046	=item ECB_I2A_MAX_DIGITS (=21)
		1047
		1048	Instead of using a type specific length macro, you can just use
		1049	C<ECB_I2A_MAX_DIGITS>, which is good enough for any C<ecb_i2a> function.
		1050
		1051	=back
		1052
		1053	=head3 LOW-LEVEL API
		1054
		1055	The functions above use a number of low-level APIs which have some strict
		1056	limitations, but can be used as building blocks (studying C<ecb_i2a_i32>
		1057	and related functions is recommended).
		1058
		1059	There are three families of functions: functions that convert a number
		1060	to a fixed number of digits with leading zeroes (C<ecb_i2a_0N>, C<0>
		1061	for "leading zeroes"), functions that generate up to N digits, skipping
		1062	leading zeroes (C<_N>), and functions that can generate more digits, but
		1063	the leading digit has limited range (C<_xN>).
		1064
		1065	None of the functions deal with negative numbers.
		1066
		1067	Example: convert an IP address in an u32 into dotted-quad:
		1068
		1069	uint32_t ip = 0x0a000164; // 10.0.1.100
		1070	char ips[3 * 4 + 3 + 1];
		1071	char *ptr = ips;
		1072	ptr = ecb_i2a_3 (ptr, ip >> 24 ); *ptr++ = '.';
		1073	ptr = ecb_i2a_3 (ptr, (ip >> 16) & 0xff); *ptr++ = '.';
		1074	ptr = ecb_i2a_3 (ptr, (ip >> 8) & 0xff); *ptr++ = '.';
		1075	ptr = ecb_i2a_3 (ptr, ip & 0xff); *ptr++ = 0;
		1076	printf ("ip: %s\n", ips); // prints "ip: 10.0.1.100"
		1077
		1078	=over
		1079
		1080	=item char ecb_i2a_02 (char ptr, uint32_t value) // 32 bit
		1081
		1082	=item char ecb_i2a_03 (char ptr, uint32_t value) // 32 bit
		1083
		1084	=item char ecb_i2a_04 (char ptr, uint32_t value) // 32 bit
		1085
		1086	=item char ecb_i2a_05 (char ptr, uint32_t value) // 64 bit
		1087
		1088	=item char ecb_i2a_06 (char ptr, uint32_t value) // 64 bit
		1089
		1090	=item char ecb_i2a_07 (char ptr, uint32_t value) // 64 bit
		1091
		1092	=item char ecb_i2a_08 (char ptr, uint32_t value) // 64 bit
		1093
		1094	=item char ecb_i2a_09 (char ptr, uint32_t value) // 64 bit
		1095
		1096	The C<< ecb_i2a_0I<N> >> functions take an unsigned I<value> and convert
		1097	them to exactly I<N> digits, returning a pointer to the first character
		1098	after the digits. The I<value> must be in range. The functions marked with
		1099	I<32 bit> do their calculations internally in 32 bit, the ones marked with
		1100	I<64 bit> internally use 64 bit integers, which might be slow on 32 bit
		1101	architectures (the high level API decides on 32 vs. 64 bit versions using
		1102	C<ECB_64BIT_NATIVE>).
		1103
		1104	=item char ecb_i2a_2 (char ptr, uint32_t value) // 32 bit
		1105
		1106	=item char ecb_i2a_3 (char ptr, uint32_t value) // 32 bit
		1107
		1108	=item char ecb_i2a_4 (char ptr, uint32_t value) // 32 bit
		1109
		1110	=item char ecb_i2a_5 (char ptr, uint32_t value) // 64 bit
		1111
		1112	=item char ecb_i2a_6 (char ptr, uint32_t value) // 64 bit
		1113
		1114	=item char ecb_i2a_7 (char ptr, uint32_t value) // 64 bit
		1115
		1116	=item char ecb_i2a_8 (char ptr, uint32_t value) // 64 bit
		1117
		1118	=item char ecb_i2a_9 (char ptr, uint32_t value) // 64 bit
		1119
		1120	Similarly, the C<< ecb_i2a_I<N> >> functions take an unsigned I<value>
		1121	and convert them to at most I<N> digits, suppressing leading zeroes, and
		1122	returning a pointer to the first character after the digits.
		1123
		1124	=item ECB_I2A_MAX_X5 (=59074)
		1125
		1126	=item char ecb_i2a_x5 (char ptr, uint32_t value) // 32 bit
		1127
		1128	=item ECB_I2A_MAX_X10 (=2932500665)
		1129
		1130	=item char ecb_i2a_x10 (char ptr, uint32_t value) // 64 bit
		1131
		1132	The C<< ecb_i2a_xI<N> >> functions are similar to the C<< ecb_i2a_I<N> >>
		1133	functions, but they can generate one digit more, as long as the number
		1134	is within range, which is given by the symbols C<ECB_I2A_MAX_X5> (almost
		1135	16 bit range) and C<ECB_I2A_MAX_X10> (a bit more than 31 bit range),
		1136	respectively.
		1137
		1138	For example, the digit part of a 32 bit signed integer just fits into the
		1139	C<ECB_I2A_MAX_X10> range, so while C<ecb_i2a_x10> cannot convert a 10
		1140	digit number, it can convert all 32 bit signed numbers. Sadly, it's not
		1141	good enough for 32 bit unsigned numbers.
684		1142
685	=back	1143	=back
686		1144
687	=head2 FLOATING POINT FIDDLING	1145	=head2 FLOATING POINT FIDDLING
688		1146
689	=over 4	1147	=over
690		1148
691	=item ECB_INFINITY	1149	=item ECB_INFINITY [-UECB_NO_LIBM]
692		1150
693	Evaluates to positive infinity if supported by the platform, otherwise to	1151	Evaluates to positive infinity if supported by the platform, otherwise to
694	a truly huge number.	1152	a truly huge number.
695		1153
696	=item ECB_NAN	1154	=item ECB_NAN [-UECB_NO_LIBM]
697		1155
698	Evaluates to a quiet NAN if supported by the platform, otherwise to	1156	Evaluates to a quiet NAN if supported by the platform, otherwise to
699	C<ECB_INFINITY>.	1157	C<ECB_INFINITY>.
700		1158
701	=item float ecb_ldexpf (float x, int exp)	1159	=item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM]
702		1160
703	Same as C<ldexpf>, but always available.	1161	Same as C<ldexpf>, but always available.
704		1162
		1163	=item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM]
		1164
705	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]	1165	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
706		1166
707	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]	1167	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
708		1168
709	These functions each take an argument in the native C<float> or C<double>	1169	These functions each take an argument in the native C<float> or C<double>
710	type and return the IEEE 754 bit representation of it.	1170	type and return the IEEE 754 bit representation of it (binary16/half,
		1171	binary32/single or binary64/double precision).
711		1172
712	The bit representation is just as IEEE 754 defines it, i.e. the sign bit	1173	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
713	will be the most significant bit, followed by exponent and mantissa.	1174	will be the most significant bit, followed by exponent and mantissa.
714		1175
715	This function should work even when the native floating point format isn't	1176	This function should work even when the native floating point format isn't
716	IEEE compliant, of course at a speed and code size penalty, and of course	1177	IEEE compliant, of course at a speed and code size penalty, and of course
717	also within reasonable limits (it tries to convert NaNs, infinities and	1178	also within reasonable limits (it tries to convert NaNs, infinities and
718	denormals, but will likely convert negative zero to positive zero).	1179	denormals, but will likely convert negative zero to positive zero).
719		1180
720	On all modern platforms (where C<ECB_STDFP> is true), the compiler should	1181	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
721	be able to optimise away this function completely.	1182	be able to completely optimise away the 32 and 64 bit functions.
722		1183
723	These functions can be helpful when serialising floats to the network - you	1184	These functions can be helpful when serialising floats to the network - you
724	can serialise the return value like a normal uint32_t/uint64_t.	1185	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
725		1186
726	Another use for these functions is to manipulate floating point values	1187	Another use for these functions is to manipulate floating point values
727	directly.	1188	directly.
728		1189
729	Silly example: toggle the sign bit of a float.	1190	Silly example: toggle the sign bit of a float.
…		…
736		1197
737	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]	1198	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
738		1199
739	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]	1200	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
740		1201
741	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]	1202	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
742		1203
743	The reverse operation of the previous function - takes the bit	1204	The reverse operation of the previous function - takes the bit
744	representation of an IEEE binary16, binary32 or binary64 number and	1205	representation of an IEEE binary16, binary32 or binary64 number (half,
745	converts it to the native C<float> or C<double> format.	1206	single or double precision) and converts it to the native C<float> or
		1207	C<double> format.
746		1208
747	This function should work even when the native floating point format isn't	1209	This function should work even when the native floating point format isn't
748	IEEE compliant, of course at a speed and code size penalty, and of course	1210	IEEE compliant, of course at a speed and code size penalty, and of course
749	also within reasonable limits (it tries to convert normals and denormals,	1211	also within reasonable limits (it tries to convert normals and denormals,
750	and might be lucky for infinities, and with extraordinary luck, also for	1212	and might be lucky for infinities, and with extraordinary luck, also for
751	negative zero).	1213	negative zero).
752		1214
753	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
754	be able to optimise away this function completely.	1216	be able to optimise away this function completely.
755		1217
		1218	=item uint16_t ecb_binary32_to_binary16 (uint32_t x)
		1219
		1220	=item uint32_t ecb_binary16_to_binary32 (uint16_t x)
		1221
		1222	Convert a IEEE binary32/single precision to binary16/half format, and vice
		1223	versa, handling all details (round-to-nearest-even, subnormals, infinity
		1224	and NaNs) correctly.
		1225
		1226	These are functions are available under C<-DECB_NO_LIBM>, since
		1227	they do not rely on the platform floating point format. The
		1228	C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are
		1229	usually what you want.
		1230
756	=back	1231	=back
757		1232
758	=head2 ARITHMETIC	1233	=head2 ARITHMETIC
759		1234
760	=over 4	1235	=over
761		1236
762	=item x = ecb_mod (m, n)	1237	=item x = ecb_mod (m, n)
763		1238
764	Returns C<m> modulo C<n>, which is the same as the positive remainder	1239	Returns C<m> modulo C<n>, which is the same as the positive remainder
765	of the division operation between C<m> and C<n>, using floored	1240	of the division operation between C<m> and C<n>, using floored
…		…
772	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be	1247	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be
773	negatable, that is, both C<m> and C<-m> must be representable in its	1248	negatable, that is, both C<m> and C<-m> must be representable in its
774	type (this typically excludes the minimum signed integer value, the same	1249	type (this typically excludes the minimum signed integer value, the same
775	limitation as for C</> and C<%> in C).	1250	limitation as for C</> and C<%> in C).
776		1251
777	Current GCC versions compile this into an efficient branchless sequence on	1252	Current GCC/clang versions compile this into an efficient branchless
778	almost all CPUs.	1253	sequence on almost all CPUs.
779		1254
780	For example, when you want to rotate forward through the members of an	1255	For example, when you want to rotate forward through the members of an
781	array for increasing C<m> (which might be negative), then you should use	1256	array for increasing C<m> (which might be negative), then you should use
782	C<ecb_mod>, as the C<%> operator might give either negative results, or	1257	C<ecb_mod>, as the C<%> operator might give either negative results, or
783	change direction for negative values:	1258	change direction for negative values:
…		…
796		1271
797	=back	1272	=back
798		1273
799	=head2 UTILITY	1274	=head2 UTILITY
800		1275
801	=over 4	1276	=over
802		1277
803	=item element_count = ecb_array_length (name)	1278	=item element_count = ecb_array_length (name)
804		1279
805	Returns the number of elements in the array C<name>. For example:	1280	Returns the number of elements in the array C<name>. For example:
806		1281
…		…
814		1289
815	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF	1290	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF
816		1291
817	These symbols need to be defined before including F<ecb.h> the first time.	1292	These symbols need to be defined before including F<ecb.h> the first time.
818		1293
819	=over 4	1294	=over
820		1295
821	=item ECB_NO_THREADS	1296	=item ECB_NO_THREADS
822		1297
823	If F<ecb.h> is never used from multiple threads, then this symbol can	1298	If F<ecb.h> is never used from multiple threads, then this symbol can
824	be defined, in which case memory fences (and similar constructs) are	1299	be defined, in which case memory fences (and similar constructs) are
…		…
840	dependencies on the math library (usually called F<-lm>) - these are	1315	dependencies on the math library (usually called F<-lm>) - these are
841	marked with [-UECB_NO_LIBM].	1316	marked with [-UECB_NO_LIBM].
842		1317
843	=back	1318	=back
844		1319
		1320	=head1 UNDOCUMENTED FUNCTIONALITY
845		1321
		1322	F<ecb.h> is full of undocumented functionality as well, some of which is
		1323	intended to be internal-use only, some of which we forgot to document, and
		1324	some of which we hide because we are not sure we will keep the interface
		1325	stable.
		1326
		1327	While you are welcome to rummage around and use whatever you find useful
		1328	(we don't want to stop you), keep in mind that we will change undocumented
		1329	functionality in incompatible ways without thinking twice, while we are
		1330	considerably more conservative with documented things.
		1331
		1332	=head1 AUTHORS
		1333
		1334	C<libecb> is designed and maintained by:
		1335
		1336	Emanuele Giaquinta <e.giaquinta@glauco.it>
		1337	Marc Alexander Lehmann <schmorp@schmorp.de>

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Comparing libecb/ecb.pod (file contents): Revision 1.65 by root, Thu Feb 19 15:45:29 2015 UTC vs. Revision 1.101 by root, Mon Nov 22 17:15:50 2021 UTC

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Comparing libecb/ecb.pod (file contents):
Revision 1.65 by root, Thu Feb 19 15:45:29 2015 UTC vs.
Revision 1.101 by root, Mon Nov 22 17:15:50 2021 UTC