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

Comparing libecb/ecb.pod (file contents):
Revision 1.48 by root, Wed May 30 16:56:06 2012 UTC vs.
Revision 1.81 by root, Mon Jan 20 21:01:29 2020 UTC

…		…
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 ptrdiff_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
		77	For C<ptrdiff_t> and C<size_t> use C<stddef.h>/C<cstddef>.
		78
71	=head2 LANGUAGE/COMPILER VERSIONS	79	=head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS
72		80
73	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
74	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
75	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).
76		84
77	=over 4	85	=over 4
78		86
79	=item ECB_C	87	=item ECB_C
80		88
81	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,
82	which is typically true for both C and C++ compilers.	90	while not claiming to be C++.
83		91
84	=item ECB_C99	92	=item ECB_C99
85		93
86	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
87	9899:1999) or any later version.	95	9899:1999) or any later version, while not claiming to be C++.
88		96
89	Note that later versions (ECB_C11) remove core features again (for	97	Note that later versions (ECB_C11) remove core features again (for
90	example, variable length arrays).	98	example, variable length arrays).
91		99
92	=item ECB_C11	100	=item ECB_C11, ECB_C17
93		101
94	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
95	9899:2011) or any later version.	103	9899:2011, :20187) or any later version, while not claiming to be C++.
96		104
97	=item ECB_CPP	105	=item ECB_CPP
98		106
99	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
100	value, which is typically true for C++ compilers.	108	value, which is typically true for C++ compilers.
101		109
102	=item ECB_CPP11	110	=item ECB_CPP11, ECB_CPP14, ECB_CPP17
103		111
104	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
105	(C++11) or any later version.	113	(ISO/IEC 14882:2011, :2014, :2017) or any later version.
106		114
		115	=item ECB_OPTIMIZE_SIZE
		116
		117	Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol
		118	can also be defined before including F<ecb.h>, in which case it will be
		119	unchanged.
		120
107	=item ECB_GCC_VERSION(major,minor)	121	=item ECB_GCC_VERSION (major, minor)
108		122
109	Expands to a true value (suitable for testing in by the preprocessor)	123	Expands to a true value (suitable for testing in by the preprocessor)
110	if the compiler used is GNU C and the version is the given version, or	124	if the compiler used is GNU C and the version is the given version, or
111	higher.	125	higher.
112		126
113	This macro tries to return false on compilers that claim to be GCC	127	This macro tries to return false on compilers that claim to be GCC
114	compatible but aren't.	128	compatible but aren't.
115		129
		130	=item ECB_EXTERN_C
		131
		132	Expands to C<extern "C"> in C++, and a simple C<extern> in C.
		133
		134	This can be used to declare a single external C function:
		135
		136	ECB_EXTERN_C int printf (const char *format, ...);
		137
		138	=item ECB_EXTERN_C_BEG / ECB_EXTERN_C_END
		139
		140	These two macros can be used to wrap multiple C<extern "C"> definitions -
		141	they expand to nothing in C.
		142
		143	They are most useful in header files:
		144
		145	ECB_EXTERN_C_BEG
		146
		147	int mycfun1 (int x);
		148	int mycfun2 (int x);
		149
		150	ECB_EXTERN_C_END
		151
		152	=item ECB_STDFP
		153
		154	If this evaluates to a true value (suitable for testing in by the
		155	preprocessor), then C<float> and C<double> use IEEE 754 single/binary32
		156	and double/binary64 representations internally I<and> the endianness of
		157	both types match the endianness of C<uint32_t> and C<uint64_t>.
		158
		159	This means you can just copy the bits of a C<float> (or C<double>) to an
		160	C<uint32_t> (or C<uint64_t>) and get the raw IEEE 754 bit representation
		161	without having to think about format or endianness.
		162
		163	This is true for basically all modern platforms, although F<ecb.h> might
		164	not be able to deduce this correctly everywhere and might err on the safe
		165	side.
		166
		167	=item ECB_AMD64, ECB_AMD64_X32
		168
		169	These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32
		170	ABI, respectively, and undefined elsewhere.
		171
		172	The designers of the new X32 ABI for some inexplicable reason decided to
		173	make it look exactly like amd64, even though it's completely incompatible
		174	to that ABI, breaking about every piece of software that assumed that
		175	C<__x86_64> stands for, well, the x86-64 ABI, making these macros
		176	necessary.
		177
116	=back	178	=back
117		179
		180	=head2 MACRO TRICKERY
		181
		182	=over 4
		183
		184	=item ECB_CONCAT (a, b)
		185
		186	Expands any macros in C<a> and C<b>, then concatenates the result to form
		187	a single token. This is mainly useful to form identifiers from components,
		188	e.g.:
		189
		190	#define S1 str
		191	#define S2 cpy
		192
		193	ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src);
		194
		195	=item ECB_STRINGIFY (arg)
		196
		197	Expands any macros in C<arg> and returns the stringified version of
		198	it. This is mainly useful to get the contents of a macro in string form,
		199	e.g.:
		200
		201	#define SQL_LIMIT 100
		202	sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT));
		203
		204	=item ECB_STRINGIFY_EXPR (expr)
		205
		206	Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it
		207	is a valid expression. This is useful to catch typos or cases where the
		208	macro isn't available:
		209
		210	#include <errno.h>
		211
		212	ECB_STRINGIFY (EDOM); // "33" (on my system at least)
		213	ECB_STRINGIFY_EXPR (EDOM); // "33"
		214
		215	// now imagine we had a typo:
		216
		217	ECB_STRINGIFY (EDAM); // "EDAM"
		218	ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined
		219
		220	=back
		221
118	=head2 GCC ATTRIBUTES	222	=head2 ATTRIBUTES
119		223
120	A major part of libecb deals with GCC attributes. These are additional	224	A major part of libecb deals with additional attributes that can be
121	attributes that you can assign to functions, variables and sometimes even	225	assigned to functions, variables and sometimes even types - much like
122	types - much like C<const> or C<volatile> in C.	226	C<const> or C<volatile> in C. They are implemented using either GCC
123		227	attributes or other compiler/language specific features. Attributes
124	While GCC allows declarations to show up in many surprising places,
125	but not in many expected places, the safest way is to put attribute
126	declarations before the whole declaration:	228	declarations must be put before the whole declaration:
127		229
128	ecb_const int mysqrt (int a);	230	ecb_const int mysqrt (int a);
129	ecb_unused int i;	231	ecb_unused int i;
130		232
131	For variables, it is often nicer to put the attribute after the name, and
132	avoid multiple declarations using commas:
133
134	int i ecb_unused;
135
136	=over 4	233	=over 4
137
138	=item ecb_attribute ((attrs...))
139
140	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
141	nothing on other compilers, so the effect is that only GCC sees these.
142
143	Example: use the C<deprecated> attribute on a function.
144
145	ecb_attribute((__deprecated__)) void
146	do_not_use_me_anymore (void);
147		234
148	=item ecb_unused	235	=item ecb_unused
149		236
150	Marks a function or a variable as "unused", which simply suppresses a	237	Marks a function or a variable as "unused", which simply suppresses a
151	warning by GCC when it detects it as unused. This is useful when you e.g.	238	warning by GCC when it detects it as unused. This is useful when you e.g.
152	declare a variable but do not always use it:	239	declare a variable but do not always use it:
153		240
154	{	241	{
155	int var ecb_unused;	242	ecb_unused int var;
156		243
157	#ifdef SOMECONDITION	244	#ifdef SOMECONDITION
158	var = ...;	245	var = ...;
159	return var;	246	return var;
160	#else	247	#else
161	return 0;	248	return 0;
162	#endif	249	#endif
163	}	250	}
164		251
		252	=item ecb_deprecated
		253
		254	Similar to C<ecb_unused>, but marks a function, variable or type as
		255	deprecated. This makes some compilers warn when the type is used.
		256
		257	=item ecb_deprecated_message (message)
		258
		259	Same as C<ecb_deprecated>, but if possible, the specified diagnostic is
		260	used instead of a generic depreciation message when the object is being
		261	used.
		262
165	=item ecb_inline	263	=item ecb_inline
166		264
167	This is not actually an attribute, but you use it like one. It expands	265	Expands either to (a compiler-specific equivalent of) C<static inline> or
168	either to C<static inline> or to just C<static>, if inline isn't	266	to just C<static>, if inline isn't supported. It should be used to declare
169	supported. It should be used to declare functions that should be inlined,	267	functions that should be inlined, for code size or speed reasons.
170	for code size or speed reasons.
171		268
172	Example: inline this function, it surely will reduce codesize.	269	Example: inline this function, it surely will reduce codesize.
173		270
174	ecb_inline int	271	ecb_inline int
175	negmul (int a, int b)	272	negmul (int a, int b)
…		…
177	return - (a * b);	274	return - (a * b);
178	}	275	}
179		276
180	=item ecb_noinline	277	=item ecb_noinline
181		278
182	Prevent a function from being inlined - it might be optimised away, but	279	Prevents a function from being inlined - it might be optimised away, but
183	not inlined into other functions. This is useful if you know your function	280	not inlined into other functions. This is useful if you know your function
184	is rarely called and large enough for inlining not to be helpful.	281	is rarely called and large enough for inlining not to be helpful.
185		282
186	=item ecb_noreturn	283	=item ecb_noreturn
187		284
…		…
197	}	294	}
198		295
199	In this case, the compiler would probably be smart enough to deduce it on	296	In this case, the compiler would probably be smart enough to deduce it on
200	its own, so this is mainly useful for declarations.	297	its own, so this is mainly useful for declarations.
201		298
		299	=item ecb_restrict
		300
		301	Expands to the C<restrict> keyword or equivalent on compilers that support
		302	them, and to nothing on others. Must be specified on a pointer type or
		303	an array index to indicate that the memory doesn't alias with any other
		304	restricted pointer in the same scope.
		305
		306	Example: multiply a vector, and allow the compiler to parallelise the
		307	loop, because it knows it doesn't overwrite input values.
		308
		309	void
		310	multiply (ecb_restrict float *src,
		311	ecb_restrict float *dst,
		312	int len, float factor)
		313	{
		314	int i;
		315
		316	for (i = 0; i < len; ++i)
		317	dst [i] = src [i] * factor;
		318	}
		319
202	=item ecb_const	320	=item ecb_const
203		321
204	Declares that the function only depends on the values of its arguments,	322	Declares that the function only depends on the values of its arguments,
205	much like a mathematical function. It specifically does not read or write	323	much like a mathematical function. It specifically does not read or write
206	any memory any arguments might point to, global variables, or call any	324	any memory any arguments might point to, global variables, or call any
…		…
266	functions only called in exceptional or rare cases.	384	functions only called in exceptional or rare cases.
267		385
268	=item ecb_artificial	386	=item ecb_artificial
269		387
270	Declares the function as "artificial", in this case meaning that this	388	Declares the function as "artificial", in this case meaning that this
271	function is not really mean to be a function, but more like an accessor	389	function is not really meant to be a function, but more like an accessor
272	- many methods in C++ classes are mere accessor functions, and having a	390	- many methods in C++ classes are mere accessor functions, and having a
273	crash reported in such a method, or single-stepping through them, is not	391	crash reported in such a method, or single-stepping through them, is not
274	usually so helpful, especially when it's inlined to just a few instructions.	392	usually so helpful, especially when it's inlined to just a few instructions.
275		393
276	Marking them as artificial will instruct the debugger about just this,	394	Marking them as artificial will instruct the debugger about just this,
…		…
296		414
297	=head2 OPTIMISATION HINTS	415	=head2 OPTIMISATION HINTS
298		416
299	=over 4	417	=over 4
300		418
301	=item bool ecb_is_constant(expr)	419	=item bool ecb_is_constant (expr)
302		420
303	Returns true iff the expression can be deduced to be a compile-time	421	Returns true iff the expression can be deduced to be a compile-time
304	constant, and false otherwise.	422	constant, and false otherwise.
305		423
306	For example, when you have a C<rndm16> function that returns a 16 bit	424	For example, when you have a C<rndm16> function that returns a 16 bit
…		…
324	return is_constant (n) && !(n & (n - 1))	442	return is_constant (n) && !(n & (n - 1))
325	? rndm16 () & (num - 1)	443	? rndm16 () & (num - 1)
326	: (n * (uint32_t)rndm16 ()) >> 16;	444	: (n * (uint32_t)rndm16 ()) >> 16;
327	}	445	}
328		446
329	=item bool ecb_expect (expr, value)	447	=item ecb_expect (expr, value)
330		448
331	Evaluates C<expr> and returns it. In addition, it tells the compiler that	449	Evaluates C<expr> and returns it. In addition, it tells the compiler that
332	the C<expr> evaluates to C<value> a lot, which can be used for static	450	the C<expr> evaluates to C<value> a lot, which can be used for static
333	branch optimisations.	451	branch optimisations.
334		452
…		…
381	{	499	{
382	if (ecb_expect_false (current + size > end))	500	if (ecb_expect_false (current + size > end))
383	real_reserve_method (size); /* presumably noinline */	501	real_reserve_method (size); /* presumably noinline */
384	}	502	}
385		503
386	=item bool ecb_assume (cond)	504	=item ecb_assume (cond)
387		505
388	Try to tell the compiler that some condition is true, even if it's not	506	Tries to tell the compiler that some condition is true, even if it's not
389	obvious.	507	obvious. This is not a function, but a statement: it cannot be used in
		508	another expression.
390		509
391	This can be used to teach the compiler about invariants or other	510	This can be used to teach the compiler about invariants or other
392	conditions that might improve code generation, but which are impossible to	511	conditions that might improve code generation, but which are impossible to
393	deduce form the code itself.	512	deduce form the code itself.
394		513
…		…
411		530
412	Then the compiler I<might> be able to optimise out the second call	531	Then the compiler I<might> be able to optimise out the second call
413	completely, as it knows that C<< current + 1 > end >> is false and the	532	completely, as it knows that C<< current + 1 > end >> is false and the
414	call will never be executed.	533	call will never be executed.
415		534
416	=item bool ecb_unreachable ()	535	=item ecb_unreachable ()
417		536
418	This function does nothing itself, except tell the compiler that it will	537	This function does nothing itself, except tell the compiler that it will
419	never be executed. Apart from suppressing a warning in some cases, this	538	never be executed. Apart from suppressing a warning in some cases, this
420	function can be used to implement C<ecb_assume> or similar functions.	539	function can be used to implement C<ecb_assume> or similar functionality.
421		540
422	=item bool ecb_prefetch (addr, rw, locality)	541	=item ecb_prefetch (addr, rw, locality)
423		542
424	Tells the compiler to try to prefetch memory at the given C<addr>ess	543	Tells the compiler to try to prefetch memory at the given C<addr>ess
425	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of	544	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of
426	C<0> means that there will only be one access later, C<3> means that	545	C<0> means that there will only be one access later, C<3> means that
427	the data will likely be accessed very often, and values in between mean	546	the data will likely be accessed very often, and values in between mean
428	something... in between. The memory pointed to by the address does not	547	something... in between. The memory pointed to by the address does not
429	need to be accessible (it could be a null pointer for example), but C<rw>	548	need to be accessible (it could be a null pointer for example), but C<rw>
430	and C<locality> must be compile-time constants.	549	and C<locality> must be compile-time constants.
431		550
		551	This is a statement, not a function: you cannot use it as part of an
		552	expression.
		553
432	An obvious way to use this is to prefetch some data far away, in a big	554	An obvious way to use this is to prefetch some data far away, in a big
433	array you loop over. This prefetches memory some 128 array elements later,	555	array you loop over. This prefetches memory some 128 array elements later,
434	in the hope that it will be ready when the CPU arrives at that location.	556	in the hope that it will be ready when the CPU arrives at that location.
435		557
436	int sum = 0;	558	int sum = 0;
…		…
473		595
474	=item int ecb_ctz32 (uint32_t x)	596	=item int ecb_ctz32 (uint32_t x)
475		597
476	=item int ecb_ctz64 (uint64_t x)	598	=item int ecb_ctz64 (uint64_t x)
477		599
		600	=item int ecb_ctz (T x) [C++]
		601
478	Returns the index of the least significant bit set in C<x> (or	602	Returns the index of the least significant bit set in C<x> (or
479	equivalently the number of bits set to 0 before the least significant bit	603	equivalently the number of bits set to 0 before the least significant bit
480	set), starting from 0. If C<x> is 0 the result is undefined.	604	set), starting from 0. If C<x> is 0 the result is undefined.
481		605
482	For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.	606	For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.
483		607
		608	The overloaded C++ C<ecb_ctz> function supports C<uint8_t>, C<uint16_t>,
		609	C<uint32_t> and C<uint64_t> types.
		610
484	For example:	611	For example:
485		612
486	ecb_ctz32 (3) = 0	613	ecb_ctz32 (3) = 0
487	ecb_ctz32 (6) = 1	614	ecb_ctz32 (6) = 1
488		615
489	=item bool ecb_is_pot32 (uint32_t x)	616	=item bool ecb_is_pot32 (uint32_t x)
490		617
491	=item bool ecb_is_pot64 (uint32_t x)	618	=item bool ecb_is_pot64 (uint32_t x)
492		619
		620	=item bool ecb_is_pot (T x) [C++]
		621
493	Return true iff C<x> is a power of two or C<x == 0>.	622	Returns true iff C<x> is a power of two or C<x == 0>.
494		623
495	For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>.	624	For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>.
		625
		626	The overloaded C++ C<ecb_is_pot> function supports C<uint8_t>, C<uint16_t>,
		627	C<uint32_t> and C<uint64_t> types.
496		628
497	=item int ecb_ld32 (uint32_t x)	629	=item int ecb_ld32 (uint32_t x)
498		630
499	=item int ecb_ld64 (uint64_t x)	631	=item int ecb_ld64 (uint64_t x)
		632
		633	=item int ecb_ld64 (T x) [C++]
500		634
501	Returns the index of the most significant bit set in C<x>, or the number	635	Returns the index of the most significant bit set in C<x>, or the number
502	of digits the number requires in binary (so that C<< 2**ld <= x <	636	of digits the number requires in binary (so that C<< 2**ld <= x <
503	2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is	637	2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is
504	to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for	638	to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for
…		…
509	the given data type), while C<ecb_ld> returns how many bits the number	643	the given data type), while C<ecb_ld> returns how many bits the number
510	itself requires.	644	itself requires.
511		645
512	For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.	646	For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.
513		647
		648	The overloaded C++ C<ecb_ld> function supports C<uint8_t>, C<uint16_t>,
		649	C<uint32_t> and C<uint64_t> types.
		650
514	=item int ecb_popcount32 (uint32_t x)	651	=item int ecb_popcount32 (uint32_t x)
515		652
516	=item int ecb_popcount64 (uint64_t x)	653	=item int ecb_popcount64 (uint64_t x)
517		654
		655	=item int ecb_popcount (T x) [C++]
		656
518	Returns the number of bits set to 1 in C<x>.	657	Returns the number of bits set to 1 in C<x>.
519		658
520	For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.	659	For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.
		660
		661	The overloaded C++ C<ecb_popcount> function supports C<uint8_t>, C<uint16_t>,
		662	C<uint32_t> and C<uint64_t> types.
521		663
522	For example:	664	For example:
523		665
524	ecb_popcount32 (7) = 3	666	ecb_popcount32 (7) = 3
525	ecb_popcount32 (255) = 8	667	ecb_popcount32 (255) = 8
…		…
528		670
529	=item uint16_t ecb_bitrev16 (uint16_t x)	671	=item uint16_t ecb_bitrev16 (uint16_t x)
530		672
531	=item uint32_t ecb_bitrev32 (uint32_t x)	673	=item uint32_t ecb_bitrev32 (uint32_t x)
532		674
		675	=item T ecb_bitrev (T x) [C++]
		676
533	Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1	677	Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1
534	and so on.	678	and so on.
535		679
		680	The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types.
		681
536	Example:	682	Example:
537		683
538	ecb_bitrev8 (0xa7) = 0xea	684	ecb_bitrev8 (0xa7) = 0xea
539	ecb_bitrev32 (0xffcc4411) = 0x882233ff	685	ecb_bitrev32 (0xffcc4411) = 0x882233ff
540		686
		687	=item T ecb_bitrev (T x) [C++]
		688
		689	Overloaded C++ bitrev function.
		690
		691	C<T> must be one of C<uint8_t>, C<uint16_t> or C<uint32_t>.
		692
541	=item uint32_t ecb_bswap16 (uint32_t x)	693	=item uint32_t ecb_bswap16 (uint32_t x)
542		694
543	=item uint32_t ecb_bswap32 (uint32_t x)	695	=item uint32_t ecb_bswap32 (uint32_t x)
544		696
545	=item uint64_t ecb_bswap64 (uint64_t x)	697	=item uint64_t ecb_bswap64 (uint64_t x)
		698
		699	=item T ecb_bswap (T x)
546		700
547	These functions return the value of the 16-bit (32-bit, 64-bit) value	701	These functions return the value of the 16-bit (32-bit, 64-bit) value
548	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in	702	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in
549	C<ecb_bswap32>).	703	C<ecb_bswap32>).
550		704
		705	The overloaded C++ C<ecb_bswap> function supports C<uint8_t>, C<uint16_t>,
		706	C<uint32_t> and C<uint64_t> types.
		707
551	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)	708	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
552		709
553	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)	710	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
554		711
555	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	712	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
…		…
569	(C<ecb_rotl>).	726	(C<ecb_rotl>).
570		727
571	Current GCC versions understand these functions and usually compile them	728	Current GCC versions understand these functions and usually compile them
572	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on	729	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
573	x86).	730	x86).
		731
		732	=item T ecb_rotl (T x, unsigned int count) [C++]
		733
		734	=item T ecb_rotr (T x, unsigned int count) [C++]
		735
		736	Overloaded C++ rotl/rotr functions.
		737
		738	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		739
		740	=back
		741
		742	=head2 HOST ENDIANNESS CONVERSION
		743
		744	=over 4
		745
		746	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)
		747
		748	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)
		749
		750	=item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v)
		751
		752	=item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v)
		753
		754	=item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v)
		755
		756	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)
		757
		758	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.
		759
		760	The naming convention is C<ecb_>(C<be>\|C<le>)C<_u>C<16\|32\|64>C<_to_host>,
		761	where C<be> and C<le> stand for big endian and little endian, respectively.
		762
		763	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)
		764
		765	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)
		766
		767	=item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v)
		768
		769	=item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v)
		770
		771	=item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v)
		772
		773	=item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v)
		774
		775	Like above, but converts I<from> host byte order to the specified
		776	endianness.
		777
		778	=back
		779
		780	In C++ the following additional template functions are supported:
		781
		782	=over 4
		783
		784	=item T ecb_be_to_host (T v)
		785
		786	=item T ecb_le_to_host (T v)
		787
		788	=item T ecb_host_to_be (T v)
		789
		790	=item T ecb_host_to_le (T v)
		791
		792	These functions work like their C counterparts, above, but use templates,
		793	which make them useful in generic code.
		794
		795	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>
		796	(so unlike their C counterparts, there is a version for C<uint8_t>, which
		797	again can be useful in generic code).
		798
		799	=head2 UNALIGNED LOAD/STORE
		800
		801	These function load or store unaligned multi-byte values.
		802
		803	=over 4
		804
		805	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)
		806
		807	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)
		808
		809	=item uint_fast64_t ecb_peek_u64_u (const void *ptr)
		810
		811	These functions load an unaligned, unsigned 16, 32 or 64 bit value from
		812	memory.
		813
		814	=item uint_fast16_t ecb_peek_be_u16_u (const void *ptr)
		815
		816	=item uint_fast32_t ecb_peek_be_u32_u (const void *ptr)
		817
		818	=item uint_fast64_t ecb_peek_be_u64_u (const void *ptr)
		819
		820	=item uint_fast16_t ecb_peek_le_u16_u (const void *ptr)
		821
		822	=item uint_fast32_t ecb_peek_le_u32_u (const void *ptr)
		823
		824	=item uint_fast64_t ecb_peek_le_u64_u (const void *ptr)
		825
		826	Like above, but additionally convert from big endian (C<be>) or little
		827	endian (C<le>) byte order to host byte order while doing so.
		828
		829	=item ecb_poke_u16_u (void *ptr, uint16_t v)
		830
		831	=item ecb_poke_u32_u (void *ptr, uint32_t v)
		832
		833	=item ecb_poke_u64_u (void *ptr, uint64_t v)
		834
		835	These functions store an unaligned, unsigned 16, 32 or 64 bit value to
		836	memory.
		837
		838	=item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v)
		839
		840	=item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v)
		841
		842	=item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v)
		843
		844	=item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v)
		845
		846	=item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v)
		847
		848	=item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v)
		849
		850	Like above, but additionally convert from host byte order to big endian
		851	(C<be>) or little endian (C<le>) byte order while doing so.
		852
		853	=back
		854
		855	In C++ the following additional template functions are supported:
		856
		857	=over 4
		858
		859	=item T ecb_peek<T> (const void *ptr)
		860
		861	=item T ecb_peek_be<T> (const void *ptr)
		862
		863	=item T ecb_peek_le<T> (const void *ptr)
		864
		865	=item T ecb_peek_u<T> (const void *ptr)
		866
		867	=item T ecb_peek_be_u<T> (const void *ptr)
		868
		869	=item T ecb_peek_le_u<T> (const void *ptr)
		870
		871	Similarly to their C counterparts, these functions load an unsigned 8, 16,
		872	32 or 64 bit value from memory, with optional conversion from big/little
		873	endian.
		874
		875	Since the type cannot be deduced, it has to be specified explicitly, e.g.
		876
		877	uint_fast16_t v = ecb_peek<uint16_t> (ptr);
		878
		879	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		880
		881	Unlike their C counterparts, these functions support 8 bit quantities
		882	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		883	all of which hopefully makes them more useful in generic code.
		884
		885	=item ecb_poke (void *ptr, T v)
		886
		887	=item ecb_poke_be (void *ptr, T v)
		888
		889	=item ecb_poke_le (void *ptr, T v)
		890
		891	=item ecb_poke_u (void *ptr, T v)
		892
		893	=item ecb_poke_be_u (void *ptr, T v)
		894
		895	=item ecb_poke_le_u (void *ptr, T v)
		896
		897	Again, similarly to their C counterparts, these functions store an
		898	unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to
		899	big/little endian.
		900
		901	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		902
		903	Unlike their C counterparts, these functions support 8 bit quantities
		904	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		905	all of which hopefully makes them more useful in generic code.
		906
		907	=back
		908
		909	=head2 FLOATING POINT FIDDLING
		910
		911	=over 4
		912
		913	=item ECB_INFINITY [-UECB_NO_LIBM]
		914
		915	Evaluates to positive infinity if supported by the platform, otherwise to
		916	a truly huge number.
		917
		918	=item ECB_NAN [-UECB_NO_LIBM]
		919
		920	Evaluates to a quiet NAN if supported by the platform, otherwise to
		921	C<ECB_INFINITY>.
		922
		923	=item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM]
		924
		925	Same as C<ldexpf>, but always available.
		926
		927	=item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM]
		928
		929	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
		930
		931	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
		932
		933	These functions each take an argument in the native C<float> or C<double>
		934	type and return the IEEE 754 bit representation of it (binary16/half,
		935	binary32/single or binary64/double precision).
		936
		937	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
		938	will be the most significant bit, followed by exponent and mantissa.
		939
		940	This function should work even when the native floating point format isn't
		941	IEEE compliant, of course at a speed and code size penalty, and of course
		942	also within reasonable limits (it tries to convert NaNs, infinities and
		943	denormals, but will likely convert negative zero to positive zero).
		944
		945	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		946	be able to optimise away this function completely.
		947
		948	These functions can be helpful when serialising floats to the network - you
		949	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
		950
		951	Another use for these functions is to manipulate floating point values
		952	directly.
		953
		954	Silly example: toggle the sign bit of a float.
		955
		956	/* On gcc-4.7 on amd64, */
		957	/* this results in a single add instruction to toggle the bit, and 4 extra */
		958	/* instructions to move the float value to an integer register and back. */
		959
		960	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
		961
		962	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		963
		964	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
		965
		966	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
		967
		968	The reverse operation of the previous function - takes the bit
		969	representation of an IEEE binary16, binary32 or binary64 number (half,
		970	single or double precision) and converts it to the native C<float> or
		971	C<double> format.
		972
		973	This function should work even when the native floating point format isn't
		974	IEEE compliant, of course at a speed and code size penalty, and of course
		975	also within reasonable limits (it tries to convert normals and denormals,
		976	and might be lucky for infinities, and with extraordinary luck, also for
		977	negative zero).
		978
		979	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		980	be able to optimise away this function completely.
		981
		982	=item uint16_t ecb_binary32_to_binary16 (uint32_t x)
		983
		984	=item uint32_t ecb_binary16_to_binary32 (uint16_t x)
		985
		986	Convert a IEEE binary32/single precision to binary16/half format, and vice
		987	versa, handling all details (round-to-nearest-even, subnormals, infinity
		988	and NaNs) correctly.
		989
		990	These are functions are available under C<-DECB_NO_LIBM>, since
		991	they do not rely on the platform floating point format. The
		992	C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are
		993	usually what you want.
574		994
575	=back	995	=back
576		996
577	=head2 ARITHMETIC	997	=head2 ARITHMETIC
578		998
…		…
635		1055
636	These symbols need to be defined before including F<ecb.h> the first time.	1056	These symbols need to be defined before including F<ecb.h> the first time.
637		1057
638	=over 4	1058	=over 4
639		1059
640	=item ECB_NO_THRADS	1060	=item ECB_NO_THREADS
641		1061
642	If F<ecb.h> is never used from multiple threads, then this symbol can	1062	If F<ecb.h> is never used from multiple threads, then this symbol can
643	be defined, in which case memory fences (and similar constructs) are	1063	be defined, in which case memory fences (and similar constructs) are
644	completely removed, leading to more efficient code and fewer dependencies.	1064	completely removed, leading to more efficient code and fewer dependencies.
645		1065
…		…
651	multiple threads, but never concurrently (e.g. if the system the program	1071	multiple threads, but never concurrently (e.g. if the system the program
652	runs on has only a single CPU with a single core, no hyperthreading and so	1072	runs on has only a single CPU with a single core, no hyperthreading and so
653	on), then this symbol can be defined, leading to more efficient code and	1073	on), then this symbol can be defined, leading to more efficient code and
654	fewer dependencies.	1074	fewer dependencies.
655		1075
		1076	=item ECB_NO_LIBM
		1077
		1078	When defined to C<1>, do not export any functions that might introduce
		1079	dependencies on the math library (usually called F<-lm>) - these are
		1080	marked with [-UECB_NO_LIBM].
		1081
656	=back	1082	=back
657		1083
		1084	=head1 UNDOCUMENTED FUNCTIONALITY
658		1085
		1086	F<ecb.h> is full of undocumented functionality as well, some of which is
		1087	intended to be internal-use only, some of which we forgot to document, and
		1088	some of which we hide because we are not sure we will keep the interface
		1089	stable.
		1090
		1091	While you are welcome to rummage around and use whatever you find useful
		1092	(we can't stop you), keep in mind that we will change undocumented
		1093	functionality in incompatible ways without thinking twice, while we are
		1094	considerably more conservative with documented things.
		1095
		1096	=head1 AUTHORS
		1097
		1098	C<libecb> is designed and maintained by:
		1099
		1100	Emanuele Giaquinta <e.giaquinta@glauco.it>
		1101	Marc Alexander Lehmann <schmorp@schmorp.de>
		1102
		1103

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Comparing libecb/ecb.pod (file contents): Revision 1.48 by root, Wed May 30 16:56:06 2012 UTC vs. Revision 1.81 by root, Mon Jan 20 21:01:29 2020 UTC

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Comparing libecb/ecb.pod (file contents):
Revision 1.48 by root, Wed May 30 16:56:06 2012 UTC vs.
Revision 1.81 by root, Mon Jan 20 21:01:29 2020 UTC