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

Comparing libecb/ecb.pod (file contents):
Revision 1.59 by sf-exg, Mon Jan 26 12:04:56 2015 UTC vs.
Revision 1.87 by root, Mon Jun 21 21:26:48 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/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 4
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 integerss. While 64 bit
		174	integer support is very common (and in fatc 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.
…		…
163	C<__x86_64> stands for, well, the x86-64 ABI, making these macros	185	C<__x86_64> stands for, well, the x86-64 ABI, making these macros
164	necessary.	186	necessary.
165		187
166	=back	188	=back
167		189
		190	=head2 MACRO TRICKERY
		191
		192	=over 4
		193
		194	=item ECB_CONCAT (a, b)
		195
		196	Expands any macros in C<a> and C<b>, then concatenates the result to form
		197	a single token. This is mainly useful to form identifiers from components,
		198	e.g.:
		199
		200	#define S1 str
		201	#define S2 cpy
		202
		203	ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src);
		204
		205	=item ECB_STRINGIFY (arg)
		206
		207	Expands any macros in C<arg> and returns the stringified version of
		208	it. This is mainly useful to get the contents of a macro in string form,
		209	e.g.:
		210
		211	#define SQL_LIMIT 100
		212	sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT));
		213
		214	=item ECB_STRINGIFY_EXPR (expr)
		215
		216	Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it
		217	is a valid expression. This is useful to catch typos or cases where the
		218	macro isn't available:
		219
		220	#include <errno.h>
		221
		222	ECB_STRINGIFY (EDOM); // "33" (on my system at least)
		223	ECB_STRINGIFY_EXPR (EDOM); // "33"
		224
		225	// now imagine we had a typo:
		226
		227	ECB_STRINGIFY (EDAM); // "EDAM"
		228	ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined
		229
		230	=back
		231
168	=head2 GCC ATTRIBUTES	232	=head2 ATTRIBUTES
169		233
170	A major part of libecb deals with GCC attributes. These are additional	234	A major part of libecb deals with additional attributes that can be
171	attributes that you can assign to functions, variables and sometimes even	235	assigned to functions, variables and sometimes even types - much like
172	types - much like C<const> or C<volatile> in C.	236	C<const> or C<volatile> in C. They are implemented using either GCC
173		237	attributes or other compiler/language specific features. Attributes
174	While GCC allows declarations to show up in many surprising places,
175	but not in many expected places, the safest way is to put attribute
176	declarations before the whole declaration:	238	declarations must be put before the whole declaration:
177		239
178	ecb_const int mysqrt (int a);	240	ecb_const int mysqrt (int a);
179	ecb_unused int i;	241	ecb_unused int i;
180		242
181	For variables, it is often nicer to put the attribute after the name, and
182	avoid multiple declarations using commas:
183
184	int i ecb_unused;
185
186	=over 4	243	=over 4
187
188	=item ecb_attribute ((attrs...))
189
190	A simple wrapper that expands to C<__attribute__((attrs))> on GCC 3.1+ and
191	Clang 2.8+, and to nothing on other compilers, so the effect is that only
192	GCC and Clang see these.
193
194	Example: use the C<deprecated> attribute on a function.
195
196	ecb_attribute((__deprecated__)) void
197	do_not_use_me_anymore (void);
198		244
199	=item ecb_unused	245	=item ecb_unused
200		246
201	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
202	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
203	declare a variable but do not always use it:	249	you e.g. declare a variable but do not always use it:
204		250
205	{	251	{
206	int var ecb_unused;	252	ecb_unused int var;
207		253
208	#ifdef SOMECONDITION	254	#ifdef SOMECONDITION
209	var = ...;	255	var = ...;
210	return var;	256	return var;
211	#else	257	#else
…		…
216	=item ecb_deprecated	262	=item ecb_deprecated
217		263
218	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
219	deprecated. This makes some compilers warn when the type is used.	265	deprecated. This makes some compilers warn when the type is used.
220		266
		267	=item ecb_deprecated_message (message)
		268
		269	Same as C<ecb_deprecated>, but if possible, the specified diagnostic is
		270	used instead of a generic depreciation message when the object is being
		271	used.
		272
221	=item ecb_inline	273	=item ecb_inline
222		274
223	This is not actually an attribute, but you use it like one. It expands	275	Expands either to (a compiler-specific equivalent of) C<static inline> or
224	either to C<static inline> or to just C<static>, if inline isn't	276	to just C<static>, if inline isn't supported. It should be used to declare
225	supported. It should be used to declare functions that should be inlined,	277	functions that should be inlined, for code size or speed reasons.
226	for code size or speed reasons.
227		278
228	Example: inline this function, it surely will reduce codesize.	279	Example: inline this function, it surely will reduce codesize.
229		280
230	ecb_inline int	281	ecb_inline int
231	negmul (int a, int b)	282	negmul (int a, int b)
…		…
233	return - (a * b);	284	return - (a * b);
234	}	285	}
235		286
236	=item ecb_noinline	287	=item ecb_noinline
237		288
238	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
239	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
240	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.
241		292
242	=item ecb_noreturn	293	=item ecb_noreturn
243		294
…		…
264		315
265	Example: multiply a vector, and allow the compiler to parallelise the	316	Example: multiply a vector, and allow the compiler to parallelise the
266	loop, because it knows it doesn't overwrite input values.	317	loop, because it knows it doesn't overwrite input values.
267		318
268	void	319	void
269	multiply (float *ecb_restrict src,	320	multiply (ecb_restrict float *src,
270	float *ecb_restrict dst,	321	ecb_restrict float *dst,
271	int len, float factor)	322	int len, float factor)
272	{	323	{
273	int i;	324	int i;
274		325
275	for (i = 0; i < len; ++i)	326	for (i = 0; i < len; ++i)
…		…
401	return is_constant (n) && !(n & (n - 1))	452	return is_constant (n) && !(n & (n - 1))
402	? rndm16 () & (num - 1)	453	? rndm16 () & (num - 1)
403	: (n * (uint32_t)rndm16 ()) >> 16;	454	: (n * (uint32_t)rndm16 ()) >> 16;
404	}	455	}
405		456
406	=item bool ecb_expect (expr, value)	457	=item ecb_expect (expr, value)
407		458
408	Evaluates C<expr> and returns it. In addition, it tells the compiler that	459	Evaluates C<expr> and returns it. In addition, it tells the compiler that
409	the C<expr> evaluates to C<value> a lot, which can be used for static	460	the C<expr> evaluates to C<value> a lot, which can be used for static
410	branch optimisations.	461	branch optimisations.
411		462
…		…
458	{	509	{
459	if (ecb_expect_false (current + size > end))	510	if (ecb_expect_false (current + size > end))
460	real_reserve_method (size); /* presumably noinline */	511	real_reserve_method (size); /* presumably noinline */
461	}	512	}
462		513
463	=item bool ecb_assume (cond)	514	=item ecb_assume (cond)
464		515
465	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
466	obvious.	517	obvious. This is not a function, but a statement: it cannot be used in
		518	another expression.
467		519
468	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
469	conditions that might improve code generation, but which are impossible to	521	conditions that might improve code generation, but which are impossible to
470	deduce form the code itself.	522	deduce form the code itself.
471		523
…		…
488		540
489	Then the compiler I<might> be able to optimise out the second call	541	Then the compiler I<might> be able to optimise out the second call
490	completely, as it knows that C<< current + 1 > end >> is false and the	542	completely, as it knows that C<< current + 1 > end >> is false and the
491	call will never be executed.	543	call will never be executed.
492		544
493	=item bool ecb_unreachable ()	545	=item ecb_unreachable ()
494		546
495	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
496	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
497	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.
498		550
499	=item bool ecb_prefetch (addr, rw, locality)	551	=item ecb_prefetch (addr, rw, locality)
500		552
501	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
502	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
503	C<0> means that there will only be one access later, C<3> means that	555	C<0> means that there will only be one access later, C<3> means that
504	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
505	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
506	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>
507	and C<locality> must be compile-time constants.	559	and C<locality> must be compile-time constants.
508		560
		561	This is a statement, not a function: you cannot use it as part of an
		562	expression.
		563
509	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
510	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,
511	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.
512		567
513	int sum = 0;	568	int sum = 0;
…		…
550		605
551	=item int ecb_ctz32 (uint32_t x)	606	=item int ecb_ctz32 (uint32_t x)
552		607
553	=item int ecb_ctz64 (uint64_t x)	608	=item int ecb_ctz64 (uint64_t x)
554		609
		610	=item int ecb_ctz (T x) [C++]
		611
555	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
556	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
557	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.
558		615
559	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>.
560		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
561	For example:	621	For example:
562		622
563	ecb_ctz32 (3) = 0	623	ecb_ctz32 (3) = 0
564	ecb_ctz32 (6) = 1	624	ecb_ctz32 (6) = 1
565		625
566	=item bool ecb_is_pot32 (uint32_t x)	626	=item bool ecb_is_pot32 (uint32_t x)
567		627
568	=item bool ecb_is_pot64 (uint32_t x)	628	=item bool ecb_is_pot64 (uint32_t x)
569		629
		630	=item bool ecb_is_pot (T x) [C++]
		631
570	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>.
571		633
572	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.
573		638
574	=item int ecb_ld32 (uint32_t x)	639	=item int ecb_ld32 (uint32_t x)
575		640
576	=item int ecb_ld64 (uint64_t x)	641	=item int ecb_ld64 (uint64_t x)
		642
		643	=item int ecb_ld64 (T x) [C++]
577		644
578	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
579	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 <
580	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
581	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
…		…
586	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
587	itself requires.	654	itself requires.
588		655
589	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>.
590		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
591	=item int ecb_popcount32 (uint32_t x)	661	=item int ecb_popcount32 (uint32_t x)
592		662
593	=item int ecb_popcount64 (uint64_t x)	663	=item int ecb_popcount64 (uint64_t x)
594		664
		665	=item int ecb_popcount (T x) [C++]
		666
595	Returns the number of bits set to 1 in C<x>.	667	Returns the number of bits set to 1 in C<x>.
596		668
597	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.
598		673
599	For example:	674	For example:
600		675
601	ecb_popcount32 (7) = 3	676	ecb_popcount32 (7) = 3
602	ecb_popcount32 (255) = 8	677	ecb_popcount32 (255) = 8
…		…
605		680
606	=item uint16_t ecb_bitrev16 (uint16_t x)	681	=item uint16_t ecb_bitrev16 (uint16_t x)
607		682
608	=item uint32_t ecb_bitrev32 (uint32_t x)	683	=item uint32_t ecb_bitrev32 (uint32_t x)
609		684
		685	=item T ecb_bitrev (T x) [C++]
		686
610	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
611	and so on.	688	and so on.
612		689
		690	The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types.
		691
613	Example:	692	Example:
614		693
615	ecb_bitrev8 (0xa7) = 0xea	694	ecb_bitrev8 (0xa7) = 0xea
616	ecb_bitrev32 (0xffcc4411) = 0x882233ff	695	ecb_bitrev32 (0xffcc4411) = 0x882233ff
617		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
618	=item uint32_t ecb_bswap16 (uint32_t x)	703	=item uint32_t ecb_bswap16 (uint32_t x)
619		704
620	=item uint32_t ecb_bswap32 (uint32_t x)	705	=item uint32_t ecb_bswap32 (uint32_t x)
621		706
622	=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)
623		710
624	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
625	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
626	C<ecb_bswap32>).	713	C<ecb_bswap32>).
627		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
628	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)	718	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
629		719
630	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)	720	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
631		721
632	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	722	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
…		…
643		733
644	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
645	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
646	(C<ecb_rotl>).	736	(C<ecb_rotl>).
647		737
648	Current GCC versions understand these functions and usually compile them	738	Current GCC/clang versions understand these functions and usually compile
649	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on	739	them to "optimal" code (e.g. a single C<rol> or a combination of C<shld>
650	x86).	740	on x86).
		741
		742	=item T ecb_rotl (T x, unsigned int count) [C++]
		743
		744	=item T ecb_rotr (T x, unsigned int count) [C++]
		745
		746	Overloaded C++ rotl/rotr functions.
		747
		748	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		749
		750	=back
		751
		752	=head2 HOST ENDIANNESS CONVERSION
		753
		754	=over 4
		755
		756	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)
		757
		758	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)
		759
		760	=item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v)
		761
		762	=item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v)
		763
		764	=item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v)
		765
		766	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)
		767
		768	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.
		769
		770	The naming convention is C<ecb_>(C<be>\|C<le>)C<_u>C<16\|32\|64>C<_to_host>,
		771	where C<be> and C<le> stand for big endian and little endian, respectively.
		772
		773	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)
		774
		775	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)
		776
		777	=item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v)
		778
		779	=item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v)
		780
		781	=item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v)
		782
		783	=item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v)
		784
		785	Like above, but converts I<from> host byte order to the specified
		786	endianness.
		787
		788	=back
		789
		790	In C++ the following additional template functions are supported:
		791
		792	=over 4
		793
		794	=item T ecb_be_to_host (T v)
		795
		796	=item T ecb_le_to_host (T v)
		797
		798	=item T ecb_host_to_be (T v)
		799
		800	=item T ecb_host_to_le (T v)
		801
		802	=back
		803
		804	These functions work like their C counterparts, above, but use templates,
		805	which make them useful in generic code.
		806
		807	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>
		808	(so unlike their C counterparts, there is a version for C<uint8_t>, which
		809	again can be useful in generic code).
		810
		811	=head2 UNALIGNED LOAD/STORE
		812
		813	These function load or store unaligned multi-byte values.
		814
		815	=over 4
		816
		817	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)
		818
		819	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)
		820
		821	=item uint_fast64_t ecb_peek_u64_u (const void *ptr)
		822
		823	These functions load an unaligned, unsigned 16, 32 or 64 bit value from
		824	memory.
		825
		826	=item uint_fast16_t ecb_peek_be_u16_u (const void *ptr)
		827
		828	=item uint_fast32_t ecb_peek_be_u32_u (const void *ptr)
		829
		830	=item uint_fast64_t ecb_peek_be_u64_u (const void *ptr)
		831
		832	=item uint_fast16_t ecb_peek_le_u16_u (const void *ptr)
		833
		834	=item uint_fast32_t ecb_peek_le_u32_u (const void *ptr)
		835
		836	=item uint_fast64_t ecb_peek_le_u64_u (const void *ptr)
		837
		838	Like above, but additionally convert from big endian (C<be>) or little
		839	endian (C<le>) byte order to host byte order while doing so.
		840
		841	=item ecb_poke_u16_u (void *ptr, uint16_t v)
		842
		843	=item ecb_poke_u32_u (void *ptr, uint32_t v)
		844
		845	=item ecb_poke_u64_u (void *ptr, uint64_t v)
		846
		847	These functions store an unaligned, unsigned 16, 32 or 64 bit value to
		848	memory.
		849
		850	=item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v)
		851
		852	=item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v)
		853
		854	=item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v)
		855
		856	=item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v)
		857
		858	=item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v)
		859
		860	=item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v)
		861
		862	Like above, but additionally convert from host byte order to big endian
		863	(C<be>) or little endian (C<le>) byte order while doing so.
		864
		865	=back
		866
		867	In C++ the following additional template functions are supported:
		868
		869	=over 4
		870
		871	=item T ecb_peek<T> (const void *ptr)
		872
		873	=item T ecb_peek_be<T> (const void *ptr)
		874
		875	=item T ecb_peek_le<T> (const void *ptr)
		876
		877	=item T ecb_peek_u<T> (const void *ptr)
		878
		879	=item T ecb_peek_be_u<T> (const void *ptr)
		880
		881	=item T ecb_peek_le_u<T> (const void *ptr)
		882
		883	Similarly to their C counterparts, these functions load an unsigned 8, 16,
		884	32 or 64 bit value from memory, with optional conversion from big/little
		885	endian.
		886
		887	Since the type cannot be deduced, it has to be specified explicitly, e.g.
		888
		889	uint_fast16_t v = ecb_peek<uint16_t> (ptr);
		890
		891	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		892
		893	Unlike their C counterparts, these functions support 8 bit quantities
		894	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		895	all of which hopefully makes them more useful in generic code.
		896
		897	=item ecb_poke (void *ptr, T v)
		898
		899	=item ecb_poke_be (void *ptr, T v)
		900
		901	=item ecb_poke_le (void *ptr, T v)
		902
		903	=item ecb_poke_u (void *ptr, T v)
		904
		905	=item ecb_poke_be_u (void *ptr, T v)
		906
		907	=item ecb_poke_le_u (void *ptr, T v)
		908
		909	Again, similarly to their C counterparts, these functions store an
		910	unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to
		911	big/little endian.
		912
		913	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		914
		915	Unlike their C counterparts, these functions support 8 bit quantities
		916	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		917	all of which hopefully makes them more useful in generic code.
651		918
652	=back	919	=back
653		920
654	=head2 FLOATING POINT FIDDLING	921	=head2 FLOATING POINT FIDDLING
655		922
656	=over 4	923	=over 4
657		924
		925	=item ECB_INFINITY [-UECB_NO_LIBM]
		926
		927	Evaluates to positive infinity if supported by the platform, otherwise to
		928	a truly huge number.
		929
		930	=item ECB_NAN [-UECB_NO_LIBM]
		931
		932	Evaluates to a quiet NAN if supported by the platform, otherwise to
		933	C<ECB_INFINITY>.
		934
		935	=item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM]
		936
		937	Same as C<ldexpf>, but always available.
		938
		939	=item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM]
		940
658	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]	941	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
659		942
660	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]	943	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
661		944
662	These functions each take an argument in the native C<float> or C<double>	945	These functions each take an argument in the native C<float> or C<double>
663	type and return the IEEE 754 bit representation of it.	946	type and return the IEEE 754 bit representation of it (binary16/half,
		947	binary32/single or binary64/double precision).
664		948
665	The bit representation is just as IEEE 754 defines it, i.e. the sign bit	949	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
666	will be the most significant bit, followed by exponent and mantissa.	950	will be the most significant bit, followed by exponent and mantissa.
667		951
668	This function should work even when the native floating point format isn't	952	This function should work even when the native floating point format isn't
…		…
672		956
673	On all modern platforms (where C<ECB_STDFP> is true), the compiler should	957	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
674	be able to optimise away this function completely.	958	be able to optimise away this function completely.
675		959
676	These functions can be helpful when serialising floats to the network - you	960	These functions can be helpful when serialising floats to the network - you
677	can serialise the return value like a normal uint32_t/uint64_t.	961	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
678		962
679	Another use for these functions is to manipulate floating point values	963	Another use for these functions is to manipulate floating point values
680	directly.	964	directly.
681		965
682	Silly example: toggle the sign bit of a float.	966	Silly example: toggle the sign bit of a float.
…		…
689		973
690	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]	974	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
691		975
692	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]	976	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
693		977
694	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]	978	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
695		979
696	The reverse operation of the previous function - takes the bit	980	The reverse operation of the previous function - takes the bit
697	representation of an IEEE binary16, binary32 or binary64 number and	981	representation of an IEEE binary16, binary32 or binary64 number (half,
698	converts it to the native C<float> or C<double> format.	982	single or double precision) and converts it to the native C<float> or
		983	C<double> format.
699		984
700	This function should work even when the native floating point format isn't	985	This function should work even when the native floating point format isn't
701	IEEE compliant, of course at a speed and code size penalty, and of course	986	IEEE compliant, of course at a speed and code size penalty, and of course
702	also within reasonable limits (it tries to convert normals and denormals,	987	also within reasonable limits (it tries to convert normals and denormals,
703	and might be lucky for infinities, and with extraordinary luck, also for	988	and might be lucky for infinities, and with extraordinary luck, also for
704	negative zero).	989	negative zero).
705		990
706	On all modern platforms (where C<ECB_STDFP> is true), the compiler should	991	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
707	be able to optimise away this function completely.	992	be able to optimise away this function completely.
		993
		994	=item uint16_t ecb_binary32_to_binary16 (uint32_t x)
		995
		996	=item uint32_t ecb_binary16_to_binary32 (uint16_t x)
		997
		998	Convert a IEEE binary32/single precision to binary16/half format, and vice
		999	versa, handling all details (round-to-nearest-even, subnormals, infinity
		1000	and NaNs) correctly.
		1001
		1002	These are functions are available under C<-DECB_NO_LIBM>, since
		1003	they do not rely on the platform floating point format. The
		1004	C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are
		1005	usually what you want.
708		1006
709	=back	1007	=back
710		1008
711	=head2 ARITHMETIC	1009	=head2 ARITHMETIC
712		1010
…		…
725	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be	1023	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be
726	negatable, that is, both C<m> and C<-m> must be representable in its	1024	negatable, that is, both C<m> and C<-m> must be representable in its
727	type (this typically excludes the minimum signed integer value, the same	1025	type (this typically excludes the minimum signed integer value, the same
728	limitation as for C</> and C<%> in C).	1026	limitation as for C</> and C<%> in C).
729		1027
730	Current GCC versions compile this into an efficient branchless sequence on	1028	Current GCC/clang versions compile this into an efficient branchless
731	almost all CPUs.	1029	sequence on almost all CPUs.
732		1030
733	For example, when you want to rotate forward through the members of an	1031	For example, when you want to rotate forward through the members of an
734	array for increasing C<m> (which might be negative), then you should use	1032	array for increasing C<m> (which might be negative), then you should use
735	C<ecb_mod>, as the C<%> operator might give either negative results, or	1033	C<ecb_mod>, as the C<%> operator might give either negative results, or
736	change direction for negative values:	1034	change direction for negative values:
…		…
793	dependencies on the math library (usually called F<-lm>) - these are	1091	dependencies on the math library (usually called F<-lm>) - these are
794	marked with [-UECB_NO_LIBM].	1092	marked with [-UECB_NO_LIBM].
795		1093
796	=back	1094	=back
797		1095
		1096	=head1 UNDOCUMENTED FUNCTIONALITY
798		1097
		1098	F<ecb.h> is full of undocumented functionality as well, some of which is
		1099	intended to be internal-use only, some of which we forgot to document, and
		1100	some of which we hide because we are not sure we will keep the interface
		1101	stable.
		1102
		1103	While you are welcome to rummage around and use whatever you find useful
		1104	(we can't stop you), keep in mind that we will change undocumented
		1105	functionality in incompatible ways without thinking twice, while we are
		1106	considerably more conservative with documented things.
		1107
		1108	=head1 AUTHORS
		1109
		1110	C<libecb> is designed and maintained by:
		1111
		1112	Emanuele Giaquinta <e.giaquinta@glauco.it>
		1113	Marc Alexander Lehmann <schmorp@schmorp.de>
		1114
		1115

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing libecb/ecb.pod (file contents): Revision 1.59 by sf-exg, Mon Jan 26 12:04:56 2015 UTC vs. Revision 1.87 by root, Mon Jun 21 21:26:48 2021 UTC

Diff Legend

Comparing libecb/ecb.pod (file contents):
Revision 1.59 by sf-exg, Mon Jan 26 12:04:56 2015 UTC vs.
Revision 1.87 by root, Mon Jun 21 21:26:48 2021 UTC