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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.64 by root, Wed Feb 18 20:48:59 2015 UTC vs.
Revision 1.94 by root, Sat Jul 31 16:13:30 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.	517	obvious. This is not a function, but a statement: it cannot be used in
		518	another expression.
496		519
497	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
498	conditions that might improve code generation, but which are impossible to	521	conditions that might improve code generation, but which are impossible to
499	deduce form the code itself.	522	deduce form the code itself.
500		523
…		…
521		544
522	=item ecb_unreachable ()	545	=item ecb_unreachable ()
523		546
524	This function does nothing itself, except tell the compiler that it will	547	This function does nothing itself, except tell the compiler that it will
525	never be executed. Apart from suppressing a warning in some cases, this	548	never be executed. Apart from suppressing a warning in some cases, this
526	function can be used to implement C<ecb_assume> or similar functions.	549	function can be used to implement C<ecb_assume> or similar functionality.
527		550
528	=item ecb_prefetch (addr, rw, locality)	551	=item ecb_prefetch (addr, rw, locality)
529		552
530	Tells the compiler to try to prefetch memory at the given C<addr>ess	553	Tells the compiler to try to prefetch memory at the given C<addr>ess
531	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of	554	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of
…		…
533	the data will likely be accessed very often, and values in between mean	556	the data will likely be accessed very often, and values in between mean
534	something... in between. The memory pointed to by the address does not	557	something... in between. The memory pointed to by the address does not
535	need to be accessible (it could be a null pointer for example), but C<rw>	558	need to be accessible (it could be a null pointer for example), but C<rw>
536	and C<locality> must be compile-time constants.	559	and C<locality> must be compile-time constants.
537		560
		561	This is a statement, not a function: you cannot use it as part of an
		562	expression.
		563
538	An obvious way to use this is to prefetch some data far away, in a big	564	An obvious way to use this is to prefetch some data far away, in a big
539	array you loop over. This prefetches memory some 128 array elements later,	565	array you loop over. This prefetches memory some 128 array elements later,
540	in the hope that it will be ready when the CPU arrives at that location.	566	in the hope that it will be ready when the CPU arrives at that location.
541		567
542	int sum = 0;	568	int sum = 0;
…		…
563		589
564	=back	590	=back
565		591
566	=head2 BIT FIDDLING / BIT WIZARDRY	592	=head2 BIT FIDDLING / BIT WIZARDRY
567		593
568	=over 4	594	=over
569		595
570	=item bool ecb_big_endian ()	596	=item bool ecb_big_endian ()
571		597
572	=item bool ecb_little_endian ()	598	=item bool ecb_little_endian ()
573		599
…		…
579		605
580	=item int ecb_ctz32 (uint32_t x)	606	=item int ecb_ctz32 (uint32_t x)
581		607
582	=item int ecb_ctz64 (uint64_t x)	608	=item int ecb_ctz64 (uint64_t x)
583		609
		610	=item int ecb_ctz (T x) [C++]
		611
584	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
585	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
586	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.
587		615
588	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>.
589		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
590	For example:	621	For example:
591		622
592	ecb_ctz32 (3) = 0	623	ecb_ctz32 (3) = 0
593	ecb_ctz32 (6) = 1	624	ecb_ctz32 (6) = 1
594		625
595	=item bool ecb_is_pot32 (uint32_t x)	626	=item bool ecb_is_pot32 (uint32_t x)
596		627
597	=item bool ecb_is_pot64 (uint32_t x)	628	=item bool ecb_is_pot64 (uint32_t x)
598		629
		630	=item bool ecb_is_pot (T x) [C++]
		631
599	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>.
600		633
601	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.
602		638
603	=item int ecb_ld32 (uint32_t x)	639	=item int ecb_ld32 (uint32_t x)
604		640
605	=item int ecb_ld64 (uint64_t x)	641	=item int ecb_ld64 (uint64_t x)
		642
		643	=item int ecb_ld64 (T x) [C++]
606		644
607	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
608	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 <
609	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
610	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
…		…
615	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
616	itself requires.	654	itself requires.
617		655
618	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>.
619		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
620	=item int ecb_popcount32 (uint32_t x)	661	=item int ecb_popcount32 (uint32_t x)
621		662
622	=item int ecb_popcount64 (uint64_t x)	663	=item int ecb_popcount64 (uint64_t x)
623		664
		665	=item int ecb_popcount (T x) [C++]
		666
624	Returns the number of bits set to 1 in C<x>.	667	Returns the number of bits set to 1 in C<x>.
625		668
626	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.
627		673
628	For example:	674	For example:
629		675
630	ecb_popcount32 (7) = 3	676	ecb_popcount32 (7) = 3
631	ecb_popcount32 (255) = 8	677	ecb_popcount32 (255) = 8
…		…
634		680
635	=item uint16_t ecb_bitrev16 (uint16_t x)	681	=item uint16_t ecb_bitrev16 (uint16_t x)
636		682
637	=item uint32_t ecb_bitrev32 (uint32_t x)	683	=item uint32_t ecb_bitrev32 (uint32_t x)
638		684
		685	=item T ecb_bitrev (T x) [C++]
		686
639	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
640	and so on.	688	and so on.
641		689
		690	The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types.
		691
642	Example:	692	Example:
643		693
644	ecb_bitrev8 (0xa7) = 0xea	694	ecb_bitrev8 (0xa7) = 0xea
645	ecb_bitrev32 (0xffcc4411) = 0x882233ff	695	ecb_bitrev32 (0xffcc4411) = 0x882233ff
646		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
647	=item uint32_t ecb_bswap16 (uint32_t x)	703	=item uint32_t ecb_bswap16 (uint32_t x)
648		704
649	=item uint32_t ecb_bswap32 (uint32_t x)	705	=item uint32_t ecb_bswap32 (uint32_t x)
650		706
651	=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)
652		710
653	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
654	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
655	C<ecb_bswap32>).	713	C<ecb_bswap32>).
656		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
657	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)	718	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
658		719
659	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)	720	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
660		721
661	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	722	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
…		…
670		731
671	=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)	732	=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)
672		733
673	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
674	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
675	(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.
676		738
677	Current GCC versions understand these functions and usually compile them	739	Current GCC/clang versions understand these functions and usually compile
678	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>
679	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.
		748
		749	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		750
		751	=back
		752
		753	=head2 HOST ENDIANNESS CONVERSION
		754
		755	=over
		756
		757	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)
		758
		759	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)
		760
		761	=item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v)
		762
		763	=item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v)
		764
		765	=item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v)
		766
		767	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)
		768
		769	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.
		770
		771	The naming convention is C<ecb_>(C<be>\|C<le>)C<_u>C<16\|32\|64>C<_to_host>,
		772	where C<be> and C<le> stand for big endian and little endian, respectively.
		773
		774	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)
		775
		776	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)
		777
		778	=item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v)
		779
		780	=item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v)
		781
		782	=item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v)
		783
		784	=item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v)
		785
		786	Like above, but converts I<from> host byte order to the specified
		787	endianness.
		788
		789	=back
		790
		791	In C++ the following additional template functions are supported:
		792
		793	=over
		794
		795	=item T ecb_be_to_host (T v)
		796
		797	=item T ecb_le_to_host (T v)
		798
		799	=item T ecb_host_to_be (T v)
		800
		801	=item T ecb_host_to_le (T v)
		802
		803	=back
		804
		805	These functions work like their C counterparts, above, but use templates,
		806	which make them useful in generic code.
		807
		808	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>
		809	(so unlike their C counterparts, there is a version for C<uint8_t>, which
		810	again can be useful in generic code).
		811
		812	=head2 UNALIGNED LOAD/STORE
		813
		814	These function load or store unaligned multi-byte values.
		815
		816	=over
		817
		818	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)
		819
		820	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)
		821
		822	=item uint_fast64_t ecb_peek_u64_u (const void *ptr)
		823
		824	These functions load an unaligned, unsigned 16, 32 or 64 bit value from
		825	memory.
		826
		827	=item uint_fast16_t ecb_peek_be_u16_u (const void *ptr)
		828
		829	=item uint_fast32_t ecb_peek_be_u32_u (const void *ptr)
		830
		831	=item uint_fast64_t ecb_peek_be_u64_u (const void *ptr)
		832
		833	=item uint_fast16_t ecb_peek_le_u16_u (const void *ptr)
		834
		835	=item uint_fast32_t ecb_peek_le_u32_u (const void *ptr)
		836
		837	=item uint_fast64_t ecb_peek_le_u64_u (const void *ptr)
		838
		839	Like above, but additionally convert from big endian (C<be>) or little
		840	endian (C<le>) byte order to host byte order while doing so.
		841
		842	=item ecb_poke_u16_u (void *ptr, uint16_t v)
		843
		844	=item ecb_poke_u32_u (void *ptr, uint32_t v)
		845
		846	=item ecb_poke_u64_u (void *ptr, uint64_t v)
		847
		848	These functions store an unaligned, unsigned 16, 32 or 64 bit value to
		849	memory.
		850
		851	=item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v)
		852
		853	=item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v)
		854
		855	=item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v)
		856
		857	=item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v)
		858
		859	=item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v)
		860
		861	=item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v)
		862
		863	Like above, but additionally convert from host byte order to big endian
		864	(C<be>) or little endian (C<le>) byte order while doing so.
		865
		866	=back
		867
		868	In C++ the following additional template functions are supported:
		869
		870	=over
		871
		872	=item T ecb_peek<T> (const void *ptr)
		873
		874	=item T ecb_peek_be<T> (const void *ptr)
		875
		876	=item T ecb_peek_le<T> (const void *ptr)
		877
		878	=item T ecb_peek_u<T> (const void *ptr)
		879
		880	=item T ecb_peek_be_u<T> (const void *ptr)
		881
		882	=item T ecb_peek_le_u<T> (const void *ptr)
		883
		884	Similarly to their C counterparts, these functions load an unsigned 8, 16,
		885	32 or 64 bit value from memory, with optional conversion from big/little
		886	endian.
		887
		888	Since the type cannot be deduced, it has to be specified explicitly, e.g.
		889
		890	uint_fast16_t v = ecb_peek<uint16_t> (ptr);
		891
		892	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		893
		894	Unlike their C counterparts, these functions support 8 bit quantities
		895	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		896	all of which hopefully makes them more useful in generic code.
		897
		898	=item ecb_poke (void *ptr, T v)
		899
		900	=item ecb_poke_be (void *ptr, T v)
		901
		902	=item ecb_poke_le (void *ptr, T v)
		903
		904	=item ecb_poke_u (void *ptr, T v)
		905
		906	=item ecb_poke_be_u (void *ptr, T v)
		907
		908	=item ecb_poke_le_u (void *ptr, T v)
		909
		910	Again, similarly to their C counterparts, these functions store an
		911	unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to
		912	big/little endian.
		913
		914	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		915
		916	Unlike their C counterparts, these functions support 8 bit quantities
		917	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		918	all of which hopefully makes them more useful in generic code.
		919
		920	=back
		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.
680		1072
681	=back	1073	=back
682		1074
683	=head2 FLOATING POINT FIDDLING	1075	=head2 FLOATING POINT FIDDLING
684		1076
685	=over 4	1077	=over
686		1078
687	=item ECB_INFINITY	1079	=item ECB_INFINITY [-UECB_NO_LIBM]
688		1080
689	Evaluates to positive infinity if supported by the platform, otherwise to	1081	Evaluates to positive infinity if supported by the platform, otherwise to
690	a truly huge number.	1082	a truly huge number.
691		1083
692	=item ECB_NAN	1084	=item ECB_NAN [-UECB_NO_LIBM]
693		1085
694	Evaluates to a quiet NAN if supported by the platform, otherwise to	1086	Evaluates to a quiet NAN if supported by the platform, otherwise to
695	C<ECB_INFINITY>.	1087	C<ECB_INFINITY>.
696		1088
697	=item float ecb_ldexpf (float x, int exp)	1089	=item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM]
698		1090
699	Same as C<ldexpf>, but always available.	1091	Same as C<ldexpf>, but always available.
700		1092
		1093	=item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM]
		1094
701	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]	1095	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
702		1096
703	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]	1097	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
704		1098
705	These functions each take an argument in the native C<float> or C<double>	1099	These functions each take an argument in the native C<float> or C<double>
706	type and return the IEEE 754 bit representation of it.	1100	type and return the IEEE 754 bit representation of it (binary16/half,
		1101	binary32/single or binary64/double precision).
707		1102
708	The bit representation is just as IEEE 754 defines it, i.e. the sign bit	1103	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
709	will be the most significant bit, followed by exponent and mantissa.	1104	will be the most significant bit, followed by exponent and mantissa.
710		1105
711	This function should work even when the native floating point format isn't	1106	This function should work even when the native floating point format isn't
…		…
715		1110
716	On all modern platforms (where C<ECB_STDFP> is true), the compiler should	1111	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
717	be able to optimise away this function completely.	1112	be able to optimise away this function completely.
718		1113
719	These functions can be helpful when serialising floats to the network - you	1114	These functions can be helpful when serialising floats to the network - you
720	can serialise the return value like a normal uint32_t/uint64_t.	1115	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
721		1116
722	Another use for these functions is to manipulate floating point values	1117	Another use for these functions is to manipulate floating point values
723	directly.	1118	directly.
724		1119
725	Silly example: toggle the sign bit of a float.	1120	Silly example: toggle the sign bit of a float.
…		…
732		1127
733	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]	1128	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
734		1129
735	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]	1130	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
736		1131
737	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]	1132	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
738		1133
739	The reverse operation of the previous function - takes the bit	1134	The reverse operation of the previous function - takes the bit
740	representation of an IEEE binary16, binary32 or binary64 number and	1135	representation of an IEEE binary16, binary32 or binary64 number (half,
741	converts it to the native C<float> or C<double> format.	1136	single or double precision) and converts it to the native C<float> or
		1137	C<double> format.
742		1138
743	This function should work even when the native floating point format isn't	1139	This function should work even when the native floating point format isn't
744	IEEE compliant, of course at a speed and code size penalty, and of course	1140	IEEE compliant, of course at a speed and code size penalty, and of course
745	also within reasonable limits (it tries to convert normals and denormals,	1141	also within reasonable limits (it tries to convert normals and denormals,
746	and might be lucky for infinities, and with extraordinary luck, also for	1142	and might be lucky for infinities, and with extraordinary luck, also for
747	negative zero).	1143	negative zero).
748		1144
749	On all modern platforms (where C<ECB_STDFP> is true), the compiler should	1145	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
750	be able to optimise away this function completely.	1146	be able to optimise away this function completely.
751		1147
		1148	=item uint16_t ecb_binary32_to_binary16 (uint32_t x)
		1149
		1150	=item uint32_t ecb_binary16_to_binary32 (uint16_t x)
		1151
		1152	Convert a IEEE binary32/single precision to binary16/half format, and vice
		1153	versa, handling all details (round-to-nearest-even, subnormals, infinity
		1154	and NaNs) correctly.
		1155
		1156	These are functions are available under C<-DECB_NO_LIBM>, since
		1157	they do not rely on the platform floating point format. The
		1158	C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are
		1159	usually what you want.
		1160
752	=back	1161	=back
753		1162
754	=head2 ARITHMETIC	1163	=head2 ARITHMETIC
755		1164
756	=over 4	1165	=over
757		1166
758	=item x = ecb_mod (m, n)	1167	=item x = ecb_mod (m, n)
759		1168
760	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
761	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
…		…
768	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
769	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
770	type (this typically excludes the minimum signed integer value, the same	1179	type (this typically excludes the minimum signed integer value, the same
771	limitation as for C</> and C<%> in C).	1180	limitation as for C</> and C<%> in C).
772		1181
773	Current GCC versions compile this into an efficient branchless sequence on	1182	Current GCC/clang versions compile this into an efficient branchless
774	almost all CPUs.	1183	sequence on almost all CPUs.
775		1184
776	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
777	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
778	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
779	change direction for negative values:	1188	change direction for negative values:
…		…
792		1201
793	=back	1202	=back
794		1203
795	=head2 UTILITY	1204	=head2 UTILITY
796		1205
797	=over 4	1206	=over
798		1207
799	=item element_count = ecb_array_length (name)	1208	=item element_count = ecb_array_length (name)
800		1209
801	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:
802		1211
…		…
810		1219
811	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF	1220	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF
812		1221
813	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.
814		1223
815	=over 4	1224	=over
816		1225
817	=item ECB_NO_THREADS	1226	=item ECB_NO_THREADS
818		1227
819	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
820	be defined, in which case memory fences (and similar constructs) are	1229	be defined, in which case memory fences (and similar constructs) are
…		…
836	dependencies on the math library (usually called F<-lm>) - these are	1245	dependencies on the math library (usually called F<-lm>) - these are
837	marked with [-UECB_NO_LIBM].	1246	marked with [-UECB_NO_LIBM].
838		1247
839	=back	1248	=back
840		1249
		1250	=head1 UNDOCUMENTED FUNCTIONALITY
841		1251
		1252	F<ecb.h> is full of undocumented functionality as well, some of which is
		1253	intended to be internal-use only, some of which we forgot to document, and
		1254	some of which we hide because we are not sure we will keep the interface
		1255	stable.
		1256
		1257	While you are welcome to rummage around and use whatever you find useful
		1258	(we can't stop you), keep in mind that we will change undocumented
		1259	functionality in incompatible ways without thinking twice, while we are
		1260	considerably more conservative with documented things.
		1261
		1262	=head1 AUTHORS
		1263
		1264	C<libecb> is designed and maintained by:
		1265
		1266	Emanuele Giaquinta <e.giaquinta@glauco.it>
		1267	Marc Alexander Lehmann <schmorp@schmorp.de>
		1268
		1269

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Comparing cvsroot/libecb/ecb.pod (file contents): Revision 1.64 by root, Wed Feb 18 20:48:59 2015 UTC vs. Revision 1.94 by root, Sat Jul 31 16:13:30 2021 UTC

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Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.64 by root, Wed Feb 18 20:48:59 2015 UTC vs.
Revision 1.94 by root, Sat Jul 31 16:13:30 2021 UTC