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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.48 by root, Wed May 30 16:56:06 2012 UTC vs.
Revision 1.84 by root, Mon Jan 20 21:10:16 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++, i..e C, but not 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	Note that many C++20 features will likely have their own feature test
		116	macros (see e.g. L<http://eel.is/c++draft/cpp.predefined#1.8>).
		117
		118	=item ECB_OPTIMIZE_SIZE
		119
		120	Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol
		121	can also be defined before including F<ecb.h>, in which case it will be
		122	unchanged.
		123
107	=item ECB_GCC_VERSION(major,minor)	124	=item ECB_GCC_VERSION (major, minor)
108		125
109	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
110	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.
111	higher.
112		128
113	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
114	compatible but aren't.	130	compatible but aren't.
115		131
		132	=item ECB_EXTERN_C
		133
		134	Expands to C<extern "C"> in C++, and a simple C<extern> in C.
		135
		136	This can be used to declare a single external C function:
		137
		138	ECB_EXTERN_C int printf (const char *format, ...);
		139
		140	=item ECB_EXTERN_C_BEG / ECB_EXTERN_C_END
		141
		142	These two macros can be used to wrap multiple C<extern "C"> definitions -
		143	they expand to nothing in C.
		144
		145	They are most useful in header files:
		146
		147	ECB_EXTERN_C_BEG
		148
		149	int mycfun1 (int x);
		150	int mycfun2 (int x);
		151
		152	ECB_EXTERN_C_END
		153
		154	=item ECB_STDFP
		155
		156	If this evaluates to a true value (suitable for testing by the
		157	preprocessor), then C<float> and C<double> use IEEE 754 single/binary32
		158	and double/binary64 representations internally I<and> the endianness of
		159	both types match the endianness of C<uint32_t> and C<uint64_t>.
		160
		161	This means you can just copy the bits of a C<float> (or C<double>) to an
		162	C<uint32_t> (or C<uint64_t>) and get the raw IEEE 754 bit representation
		163	without having to think about format or endianness.
		164
		165	This is true for basically all modern platforms, although F<ecb.h> might
		166	not be able to deduce this correctly everywhere and might err on the safe
		167	side.
		168
		169	=item ECB_AMD64, ECB_AMD64_X32
		170
		171	These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32
		172	ABI, respectively, and undefined elsewhere.
		173
		174	The designers of the new X32 ABI for some inexplicable reason decided to
		175	make it look exactly like amd64, even though it's completely incompatible
		176	to that ABI, breaking about every piece of software that assumed that
		177	C<__x86_64> stands for, well, the x86-64 ABI, making these macros
		178	necessary.
		179
116	=back	180	=back
117		181
		182	=head2 MACRO TRICKERY
		183
		184	=over 4
		185
		186	=item ECB_CONCAT (a, b)
		187
		188	Expands any macros in C<a> and C<b>, then concatenates the result to form
		189	a single token. This is mainly useful to form identifiers from components,
		190	e.g.:
		191
		192	#define S1 str
		193	#define S2 cpy
		194
		195	ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src);
		196
		197	=item ECB_STRINGIFY (arg)
		198
		199	Expands any macros in C<arg> and returns the stringified version of
		200	it. This is mainly useful to get the contents of a macro in string form,
		201	e.g.:
		202
		203	#define SQL_LIMIT 100
		204	sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT));
		205
		206	=item ECB_STRINGIFY_EXPR (expr)
		207
		208	Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it
		209	is a valid expression. This is useful to catch typos or cases where the
		210	macro isn't available:
		211
		212	#include <errno.h>
		213
		214	ECB_STRINGIFY (EDOM); // "33" (on my system at least)
		215	ECB_STRINGIFY_EXPR (EDOM); // "33"
		216
		217	// now imagine we had a typo:
		218
		219	ECB_STRINGIFY (EDAM); // "EDAM"
		220	ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined
		221
		222	=back
		223
118	=head2 GCC ATTRIBUTES	224	=head2 ATTRIBUTES
119		225
120	A major part of libecb deals with GCC attributes. These are additional	226	A major part of libecb deals with additional attributes that can be
121	attributes that you can assign to functions, variables and sometimes even	227	assigned to functions, variables and sometimes even types - much like
122	types - much like C<const> or C<volatile> in C.	228	C<const> or C<volatile> in C. They are implemented using either GCC
123		229	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:	230	declarations must be put before the whole declaration:
127		231
128	ecb_const int mysqrt (int a);	232	ecb_const int mysqrt (int a);
129	ecb_unused int i;	233	ecb_unused int i;
130		234
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	235	=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		236
148	=item ecb_unused	237	=item ecb_unused
149		238
150	Marks a function or a variable as "unused", which simply suppresses a	239	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.	240	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:	241	declare a variable but do not always use it:
153		242
154	{	243	{
155	int var ecb_unused;	244	ecb_unused int var;
156		245
157	#ifdef SOMECONDITION	246	#ifdef SOMECONDITION
158	var = ...;	247	var = ...;
159	return var;	248	return var;
160	#else	249	#else
161	return 0;	250	return 0;
162	#endif	251	#endif
163	}	252	}
164		253
		254	=item ecb_deprecated
		255
		256	Similar to C<ecb_unused>, but marks a function, variable or type as
		257	deprecated. This makes some compilers warn when the type is used.
		258
		259	=item ecb_deprecated_message (message)
		260
		261	Same as C<ecb_deprecated>, but if possible, the specified diagnostic is
		262	used instead of a generic depreciation message when the object is being
		263	used.
		264
165	=item ecb_inline	265	=item ecb_inline
166		266
167	This is not actually an attribute, but you use it like one. It expands	267	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	268	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,	269	functions that should be inlined, for code size or speed reasons.
170	for code size or speed reasons.
171		270
172	Example: inline this function, it surely will reduce codesize.	271	Example: inline this function, it surely will reduce codesize.
173		272
174	ecb_inline int	273	ecb_inline int
175	negmul (int a, int b)	274	negmul (int a, int b)
…		…
177	return - (a * b);	276	return - (a * b);
178	}	277	}
179		278
180	=item ecb_noinline	279	=item ecb_noinline
181		280
182	Prevent a function from being inlined - it might be optimised away, but	281	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	282	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.	283	is rarely called and large enough for inlining not to be helpful.
185		284
186	=item ecb_noreturn	285	=item ecb_noreturn
187		286
…		…
197	}	296	}
198		297
199	In this case, the compiler would probably be smart enough to deduce it on	298	In this case, the compiler would probably be smart enough to deduce it on
200	its own, so this is mainly useful for declarations.	299	its own, so this is mainly useful for declarations.
201		300
		301	=item ecb_restrict
		302
		303	Expands to the C<restrict> keyword or equivalent on compilers that support
		304	them, and to nothing on others. Must be specified on a pointer type or
		305	an array index to indicate that the memory doesn't alias with any other
		306	restricted pointer in the same scope.
		307
		308	Example: multiply a vector, and allow the compiler to parallelise the
		309	loop, because it knows it doesn't overwrite input values.
		310
		311	void
		312	multiply (ecb_restrict float *src,
		313	ecb_restrict float *dst,
		314	int len, float factor)
		315	{
		316	int i;
		317
		318	for (i = 0; i < len; ++i)
		319	dst [i] = src [i] * factor;
		320	}
		321
202	=item ecb_const	322	=item ecb_const
203		323
204	Declares that the function only depends on the values of its arguments,	324	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	325	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	326	any memory any arguments might point to, global variables, or call any
…		…
266	functions only called in exceptional or rare cases.	386	functions only called in exceptional or rare cases.
267		387
268	=item ecb_artificial	388	=item ecb_artificial
269		389
270	Declares the function as "artificial", in this case meaning that this	390	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	391	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	392	- 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	393	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.	394	usually so helpful, especially when it's inlined to just a few instructions.
275		395
276	Marking them as artificial will instruct the debugger about just this,	396	Marking them as artificial will instruct the debugger about just this,
…		…
296		416
297	=head2 OPTIMISATION HINTS	417	=head2 OPTIMISATION HINTS
298		418
299	=over 4	419	=over 4
300		420
301	=item bool ecb_is_constant(expr)	421	=item bool ecb_is_constant (expr)
302		422
303	Returns true iff the expression can be deduced to be a compile-time	423	Returns true iff the expression can be deduced to be a compile-time
304	constant, and false otherwise.	424	constant, and false otherwise.
305		425
306	For example, when you have a C<rndm16> function that returns a 16 bit	426	For example, when you have a C<rndm16> function that returns a 16 bit
…		…
324	return is_constant (n) && !(n & (n - 1))	444	return is_constant (n) && !(n & (n - 1))
325	? rndm16 () & (num - 1)	445	? rndm16 () & (num - 1)
326	: (n * (uint32_t)rndm16 ()) >> 16;	446	: (n * (uint32_t)rndm16 ()) >> 16;
327	}	447	}
328		448
329	=item bool ecb_expect (expr, value)	449	=item ecb_expect (expr, value)
330		450
331	Evaluates C<expr> and returns it. In addition, it tells the compiler that	451	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	452	the C<expr> evaluates to C<value> a lot, which can be used for static
333	branch optimisations.	453	branch optimisations.
334		454
…		…
381	{	501	{
382	if (ecb_expect_false (current + size > end))	502	if (ecb_expect_false (current + size > end))
383	real_reserve_method (size); /* presumably noinline */	503	real_reserve_method (size); /* presumably noinline */
384	}	504	}
385		505
386	=item bool ecb_assume (cond)	506	=item ecb_assume (cond)
387		507
388	Try to tell the compiler that some condition is true, even if it's not	508	Tries to tell the compiler that some condition is true, even if it's not
389	obvious.	509	obvious. This is not a function, but a statement: it cannot be used in
		510	another expression.
390		511
391	This can be used to teach the compiler about invariants or other	512	This can be used to teach the compiler about invariants or other
392	conditions that might improve code generation, but which are impossible to	513	conditions that might improve code generation, but which are impossible to
393	deduce form the code itself.	514	deduce form the code itself.
394		515
…		…
411		532
412	Then the compiler I<might> be able to optimise out the second call	533	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	534	completely, as it knows that C<< current + 1 > end >> is false and the
414	call will never be executed.	535	call will never be executed.
415		536
416	=item bool ecb_unreachable ()	537	=item ecb_unreachable ()
417		538
418	This function does nothing itself, except tell the compiler that it will	539	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	540	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.	541	function can be used to implement C<ecb_assume> or similar functionality.
421		542
422	=item bool ecb_prefetch (addr, rw, locality)	543	=item ecb_prefetch (addr, rw, locality)
423		544
424	Tells the compiler to try to prefetch memory at the given C<addr>ess	545	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	546	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	547	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	548	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	549	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>	550	need to be accessible (it could be a null pointer for example), but C<rw>
430	and C<locality> must be compile-time constants.	551	and C<locality> must be compile-time constants.
431		552
		553	This is a statement, not a function: you cannot use it as part of an
		554	expression.
		555
432	An obvious way to use this is to prefetch some data far away, in a big	556	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,	557	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.	558	in the hope that it will be ready when the CPU arrives at that location.
435		559
436	int sum = 0;	560	int sum = 0;
…		…
473		597
474	=item int ecb_ctz32 (uint32_t x)	598	=item int ecb_ctz32 (uint32_t x)
475		599
476	=item int ecb_ctz64 (uint64_t x)	600	=item int ecb_ctz64 (uint64_t x)
477		601
		602	=item int ecb_ctz (T x) [C++]
		603
478	Returns the index of the least significant bit set in C<x> (or	604	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	605	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.	606	set), starting from 0. If C<x> is 0 the result is undefined.
481		607
482	For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.	608	For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.
483		609
		610	The overloaded C++ C<ecb_ctz> function supports C<uint8_t>, C<uint16_t>,
		611	C<uint32_t> and C<uint64_t> types.
		612
484	For example:	613	For example:
485		614
486	ecb_ctz32 (3) = 0	615	ecb_ctz32 (3) = 0
487	ecb_ctz32 (6) = 1	616	ecb_ctz32 (6) = 1
488		617
489	=item bool ecb_is_pot32 (uint32_t x)	618	=item bool ecb_is_pot32 (uint32_t x)
490		619
491	=item bool ecb_is_pot64 (uint32_t x)	620	=item bool ecb_is_pot64 (uint32_t x)
492		621
		622	=item bool ecb_is_pot (T x) [C++]
		623
493	Return true iff C<x> is a power of two or C<x == 0>.	624	Returns true iff C<x> is a power of two or C<x == 0>.
494		625
495	For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>.	626	For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>.
		627
		628	The overloaded C++ C<ecb_is_pot> function supports C<uint8_t>, C<uint16_t>,
		629	C<uint32_t> and C<uint64_t> types.
496		630
497	=item int ecb_ld32 (uint32_t x)	631	=item int ecb_ld32 (uint32_t x)
498		632
499	=item int ecb_ld64 (uint64_t x)	633	=item int ecb_ld64 (uint64_t x)
		634
		635	=item int ecb_ld64 (T x) [C++]
500		636
501	Returns the index of the most significant bit set in C<x>, or the number	637	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 <	638	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	639	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	640	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	645	the given data type), while C<ecb_ld> returns how many bits the number
510	itself requires.	646	itself requires.
511		647
512	For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.	648	For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.
513		649
		650	The overloaded C++ C<ecb_ld> function supports C<uint8_t>, C<uint16_t>,
		651	C<uint32_t> and C<uint64_t> types.
		652
514	=item int ecb_popcount32 (uint32_t x)	653	=item int ecb_popcount32 (uint32_t x)
515		654
516	=item int ecb_popcount64 (uint64_t x)	655	=item int ecb_popcount64 (uint64_t x)
517		656
		657	=item int ecb_popcount (T x) [C++]
		658
518	Returns the number of bits set to 1 in C<x>.	659	Returns the number of bits set to 1 in C<x>.
519		660
520	For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.	661	For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.
		662
		663	The overloaded C++ C<ecb_popcount> function supports C<uint8_t>, C<uint16_t>,
		664	C<uint32_t> and C<uint64_t> types.
521		665
522	For example:	666	For example:
523		667
524	ecb_popcount32 (7) = 3	668	ecb_popcount32 (7) = 3
525	ecb_popcount32 (255) = 8	669	ecb_popcount32 (255) = 8
…		…
528		672
529	=item uint16_t ecb_bitrev16 (uint16_t x)	673	=item uint16_t ecb_bitrev16 (uint16_t x)
530		674
531	=item uint32_t ecb_bitrev32 (uint32_t x)	675	=item uint32_t ecb_bitrev32 (uint32_t x)
532		676
		677	=item T ecb_bitrev (T x) [C++]
		678
533	Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1	679	Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1
534	and so on.	680	and so on.
535		681
		682	The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types.
		683
536	Example:	684	Example:
537		685
538	ecb_bitrev8 (0xa7) = 0xea	686	ecb_bitrev8 (0xa7) = 0xea
539	ecb_bitrev32 (0xffcc4411) = 0x882233ff	687	ecb_bitrev32 (0xffcc4411) = 0x882233ff
540		688
		689	=item T ecb_bitrev (T x) [C++]
		690
		691	Overloaded C++ bitrev function.
		692
		693	C<T> must be one of C<uint8_t>, C<uint16_t> or C<uint32_t>.
		694
541	=item uint32_t ecb_bswap16 (uint32_t x)	695	=item uint32_t ecb_bswap16 (uint32_t x)
542		696
543	=item uint32_t ecb_bswap32 (uint32_t x)	697	=item uint32_t ecb_bswap32 (uint32_t x)
544		698
545	=item uint64_t ecb_bswap64 (uint64_t x)	699	=item uint64_t ecb_bswap64 (uint64_t x)
		700
		701	=item T ecb_bswap (T x)
546		702
547	These functions return the value of the 16-bit (32-bit, 64-bit) value	703	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	704	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in
549	C<ecb_bswap32>).	705	C<ecb_bswap32>).
550		706
		707	The overloaded C++ C<ecb_bswap> function supports C<uint8_t>, C<uint16_t>,
		708	C<uint32_t> and C<uint64_t> types.
		709
551	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)	710	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
552		711
553	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)	712	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
554		713
555	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	714	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
…		…
569	(C<ecb_rotl>).	728	(C<ecb_rotl>).
570		729
571	Current GCC versions understand these functions and usually compile them	730	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	731	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
573	x86).	732	x86).
		733
		734	=item T ecb_rotl (T x, unsigned int count) [C++]
		735
		736	=item T ecb_rotr (T x, unsigned int count) [C++]
		737
		738	Overloaded C++ rotl/rotr functions.
		739
		740	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		741
		742	=back
		743
		744	=head2 HOST ENDIANNESS CONVERSION
		745
		746	=over 4
		747
		748	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)
		749
		750	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)
		751
		752	=item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v)
		753
		754	=item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v)
		755
		756	=item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v)
		757
		758	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)
		759
		760	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.
		761
		762	The naming convention is C<ecb_>(C<be>\|C<le>)C<_u>C<16\|32\|64>C<_to_host>,
		763	where C<be> and C<le> stand for big endian and little endian, respectively.
		764
		765	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)
		766
		767	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)
		768
		769	=item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v)
		770
		771	=item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v)
		772
		773	=item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v)
		774
		775	=item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v)
		776
		777	Like above, but converts I<from> host byte order to the specified
		778	endianness.
		779
		780	=back
		781
		782	In C++ the following additional template functions are supported:
		783
		784	=over 4
		785
		786	=item T ecb_be_to_host (T v)
		787
		788	=item T ecb_le_to_host (T v)
		789
		790	=item T ecb_host_to_be (T v)
		791
		792	=item T ecb_host_to_le (T v)
		793
		794	These functions work like their C counterparts, above, but use templates,
		795	which make them useful in generic code.
		796
		797	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>
		798	(so unlike their C counterparts, there is a version for C<uint8_t>, which
		799	again can be useful in generic code).
		800
		801	=head2 UNALIGNED LOAD/STORE
		802
		803	These function load or store unaligned multi-byte values.
		804
		805	=over 4
		806
		807	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)
		808
		809	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)
		810
		811	=item uint_fast64_t ecb_peek_u64_u (const void *ptr)
		812
		813	These functions load an unaligned, unsigned 16, 32 or 64 bit value from
		814	memory.
		815
		816	=item uint_fast16_t ecb_peek_be_u16_u (const void *ptr)
		817
		818	=item uint_fast32_t ecb_peek_be_u32_u (const void *ptr)
		819
		820	=item uint_fast64_t ecb_peek_be_u64_u (const void *ptr)
		821
		822	=item uint_fast16_t ecb_peek_le_u16_u (const void *ptr)
		823
		824	=item uint_fast32_t ecb_peek_le_u32_u (const void *ptr)
		825
		826	=item uint_fast64_t ecb_peek_le_u64_u (const void *ptr)
		827
		828	Like above, but additionally convert from big endian (C<be>) or little
		829	endian (C<le>) byte order to host byte order while doing so.
		830
		831	=item ecb_poke_u16_u (void *ptr, uint16_t v)
		832
		833	=item ecb_poke_u32_u (void *ptr, uint32_t v)
		834
		835	=item ecb_poke_u64_u (void *ptr, uint64_t v)
		836
		837	These functions store an unaligned, unsigned 16, 32 or 64 bit value to
		838	memory.
		839
		840	=item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v)
		841
		842	=item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v)
		843
		844	=item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v)
		845
		846	=item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v)
		847
		848	=item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v)
		849
		850	=item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v)
		851
		852	Like above, but additionally convert from host byte order to big endian
		853	(C<be>) or little endian (C<le>) byte order while doing so.
		854
		855	=back
		856
		857	In C++ the following additional template functions are supported:
		858
		859	=over 4
		860
		861	=item T ecb_peek<T> (const void *ptr)
		862
		863	=item T ecb_peek_be<T> (const void *ptr)
		864
		865	=item T ecb_peek_le<T> (const void *ptr)
		866
		867	=item T ecb_peek_u<T> (const void *ptr)
		868
		869	=item T ecb_peek_be_u<T> (const void *ptr)
		870
		871	=item T ecb_peek_le_u<T> (const void *ptr)
		872
		873	Similarly to their C counterparts, these functions load an unsigned 8, 16,
		874	32 or 64 bit value from memory, with optional conversion from big/little
		875	endian.
		876
		877	Since the type cannot be deduced, it has to be specified explicitly, e.g.
		878
		879	uint_fast16_t v = ecb_peek<uint16_t> (ptr);
		880
		881	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		882
		883	Unlike their C counterparts, these functions support 8 bit quantities
		884	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		885	all of which hopefully makes them more useful in generic code.
		886
		887	=item ecb_poke (void *ptr, T v)
		888
		889	=item ecb_poke_be (void *ptr, T v)
		890
		891	=item ecb_poke_le (void *ptr, T v)
		892
		893	=item ecb_poke_u (void *ptr, T v)
		894
		895	=item ecb_poke_be_u (void *ptr, T v)
		896
		897	=item ecb_poke_le_u (void *ptr, T v)
		898
		899	Again, similarly to their C counterparts, these functions store an
		900	unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to
		901	big/little endian.
		902
		903	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		904
		905	Unlike their C counterparts, these functions support 8 bit quantities
		906	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		907	all of which hopefully makes them more useful in generic code.
		908
		909	=back
		910
		911	=head2 FLOATING POINT FIDDLING
		912
		913	=over 4
		914
		915	=item ECB_INFINITY [-UECB_NO_LIBM]
		916
		917	Evaluates to positive infinity if supported by the platform, otherwise to
		918	a truly huge number.
		919
		920	=item ECB_NAN [-UECB_NO_LIBM]
		921
		922	Evaluates to a quiet NAN if supported by the platform, otherwise to
		923	C<ECB_INFINITY>.
		924
		925	=item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM]
		926
		927	Same as C<ldexpf>, but always available.
		928
		929	=item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM]
		930
		931	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
		932
		933	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
		934
		935	These functions each take an argument in the native C<float> or C<double>
		936	type and return the IEEE 754 bit representation of it (binary16/half,
		937	binary32/single or binary64/double precision).
		938
		939	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
		940	will be the most significant bit, followed by exponent and mantissa.
		941
		942	This function should work even when the native floating point format isn't
		943	IEEE compliant, of course at a speed and code size penalty, and of course
		944	also within reasonable limits (it tries to convert NaNs, infinities and
		945	denormals, but will likely convert negative zero to positive zero).
		946
		947	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		948	be able to optimise away this function completely.
		949
		950	These functions can be helpful when serialising floats to the network - you
		951	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
		952
		953	Another use for these functions is to manipulate floating point values
		954	directly.
		955
		956	Silly example: toggle the sign bit of a float.
		957
		958	/* On gcc-4.7 on amd64, */
		959	/* this results in a single add instruction to toggle the bit, and 4 extra */
		960	/* instructions to move the float value to an integer register and back. */
		961
		962	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
		963
		964	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		965
		966	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
		967
		968	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
		969
		970	The reverse operation of the previous function - takes the bit
		971	representation of an IEEE binary16, binary32 or binary64 number (half,
		972	single or double precision) and converts it to the native C<float> or
		973	C<double> format.
		974
		975	This function should work even when the native floating point format isn't
		976	IEEE compliant, of course at a speed and code size penalty, and of course
		977	also within reasonable limits (it tries to convert normals and denormals,
		978	and might be lucky for infinities, and with extraordinary luck, also for
		979	negative zero).
		980
		981	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		982	be able to optimise away this function completely.
		983
		984	=item uint16_t ecb_binary32_to_binary16 (uint32_t x)
		985
		986	=item uint32_t ecb_binary16_to_binary32 (uint16_t x)
		987
		988	Convert a IEEE binary32/single precision to binary16/half format, and vice
		989	versa, handling all details (round-to-nearest-even, subnormals, infinity
		990	and NaNs) correctly.
		991
		992	These are functions are available under C<-DECB_NO_LIBM>, since
		993	they do not rely on the platform floating point format. The
		994	C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are
		995	usually what you want.
574		996
575	=back	997	=back
576		998
577	=head2 ARITHMETIC	999	=head2 ARITHMETIC
578		1000
…		…
635		1057
636	These symbols need to be defined before including F<ecb.h> the first time.	1058	These symbols need to be defined before including F<ecb.h> the first time.
637		1059
638	=over 4	1060	=over 4
639		1061
640	=item ECB_NO_THRADS	1062	=item ECB_NO_THREADS
641		1063
642	If F<ecb.h> is never used from multiple threads, then this symbol can	1064	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	1065	be defined, in which case memory fences (and similar constructs) are
644	completely removed, leading to more efficient code and fewer dependencies.	1066	completely removed, leading to more efficient code and fewer dependencies.
645		1067
…		…
651	multiple threads, but never concurrently (e.g. if the system the program	1073	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	1074	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	1075	on), then this symbol can be defined, leading to more efficient code and
654	fewer dependencies.	1076	fewer dependencies.
655		1077
		1078	=item ECB_NO_LIBM
		1079
		1080	When defined to C<1>, do not export any functions that might introduce
		1081	dependencies on the math library (usually called F<-lm>) - these are
		1082	marked with [-UECB_NO_LIBM].
		1083
656	=back	1084	=back
657		1085
		1086	=head1 UNDOCUMENTED FUNCTIONALITY
658		1087
		1088	F<ecb.h> is full of undocumented functionality as well, some of which is
		1089	intended to be internal-use only, some of which we forgot to document, and
		1090	some of which we hide because we are not sure we will keep the interface
		1091	stable.
		1092
		1093	While you are welcome to rummage around and use whatever you find useful
		1094	(we can't stop you), keep in mind that we will change undocumented
		1095	functionality in incompatible ways without thinking twice, while we are
		1096	considerably more conservative with documented things.
		1097
		1098	=head1 AUTHORS
		1099
		1100	C<libecb> is designed and maintained by:
		1101
		1102	Emanuele Giaquinta <e.giaquinta@glauco.it>
		1103	Marc Alexander Lehmann <schmorp@schmorp.de>
		1104
		1105

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Comparing cvsroot/libecb/ecb.pod (file contents): Revision 1.48 by root, Wed May 30 16:56:06 2012 UTC vs. Revision 1.84 by root, Mon Jan 20 21:10:16 2020 UTC

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Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.48 by root, Wed May 30 16:56:06 2012 UTC vs.
Revision 1.84 by root, Mon Jan 20 21:10:16 2020 UTC