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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.50 by root, Thu Jun 28 20:20:27 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	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	which is typically true for both C and C++ compilers.	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.	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.	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.
108		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
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
…		…
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.
154		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
155	=back	180	=back
156		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
157	=head2 GCC ATTRIBUTES	224	=head2 ATTRIBUTES
158		225
159	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
160	attributes that you can assign to functions, variables and sometimes even	227	assigned to functions, variables and sometimes even types - much like
161	types - much like C<const> or C<volatile> in C.	228	C<const> or C<volatile> in C. They are implemented using either GCC
162		229	attributes or other compiler/language specific features. Attributes
163	While GCC allows declarations to show up in many surprising places,
164	but not in many expected places, the safest way is to put attribute
165	declarations before the whole declaration:	230	declarations must be put before the whole declaration:
166		231
167	ecb_const int mysqrt (int a);	232	ecb_const int mysqrt (int a);
168	ecb_unused int i;	233	ecb_unused int i;
169		234
170	For variables, it is often nicer to put the attribute after the name, and
171	avoid multiple declarations using commas:
172
173	int i ecb_unused;
174
175	=over 4	235	=over 4
176
177	=item ecb_attribute ((attrs...))
178
179	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
180	nothing on other compilers, so the effect is that only GCC sees these.
181
182	Example: use the C<deprecated> attribute on a function.
183
184	ecb_attribute((__deprecated__)) void
185	do_not_use_me_anymore (void);
186		236
187	=item ecb_unused	237	=item ecb_unused
188		238
189	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
190	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.
191	declare a variable but do not always use it:	241	declare a variable but do not always use it:
192		242
193	{	243	{
194	int var ecb_unused;	244	ecb_unused int var;
195		245
196	#ifdef SOMECONDITION	246	#ifdef SOMECONDITION
197	var = ...;	247	var = ...;
198	return var;	248	return var;
199	#else	249	#else
200	return 0;	250	return 0;
201	#endif	251	#endif
202	}	252	}
203		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
204	=item ecb_inline	265	=item ecb_inline
205		266
206	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
207	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
208	supported. It should be used to declare functions that should be inlined,	269	functions that should be inlined, for code size or speed reasons.
209	for code size or speed reasons.
210		270
211	Example: inline this function, it surely will reduce codesize.	271	Example: inline this function, it surely will reduce codesize.
212		272
213	ecb_inline int	273	ecb_inline int
214	negmul (int a, int b)	274	negmul (int a, int b)
…		…
216	return - (a * b);	276	return - (a * b);
217	}	277	}
218		278
219	=item ecb_noinline	279	=item ecb_noinline
220		280
221	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
222	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
223	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.
224		284
225	=item ecb_noreturn	285	=item ecb_noreturn
226		286
…		…
236	}	296	}
237		297
238	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
239	its own, so this is mainly useful for declarations.	299	its own, so this is mainly useful for declarations.
240		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
241	=item ecb_const	322	=item ecb_const
242		323
243	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,
244	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
245	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
…		…
305	functions only called in exceptional or rare cases.	386	functions only called in exceptional or rare cases.
306		387
307	=item ecb_artificial	388	=item ecb_artificial
308		389
309	Declares the function as "artificial", in this case meaning that this	390	Declares the function as "artificial", in this case meaning that this
310	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
311	- 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
312	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
313	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.
314		395
315	Marking them as artificial will instruct the debugger about just this,	396	Marking them as artificial will instruct the debugger about just this,
…		…
335		416
336	=head2 OPTIMISATION HINTS	417	=head2 OPTIMISATION HINTS
337		418
338	=over 4	419	=over 4
339		420
340	=item bool ecb_is_constant(expr)	421	=item bool ecb_is_constant (expr)
341		422
342	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
343	constant, and false otherwise.	424	constant, and false otherwise.
344		425
345	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
…		…
363	return is_constant (n) && !(n & (n - 1))	444	return is_constant (n) && !(n & (n - 1))
364	? rndm16 () & (num - 1)	445	? rndm16 () & (num - 1)
365	: (n * (uint32_t)rndm16 ()) >> 16;	446	: (n * (uint32_t)rndm16 ()) >> 16;
366	}	447	}
367		448
368	=item bool ecb_expect (expr, value)	449	=item ecb_expect (expr, value)
369		450
370	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
371	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
372	branch optimisations.	453	branch optimisations.
373		454
…		…
420	{	501	{
421	if (ecb_expect_false (current + size > end))	502	if (ecb_expect_false (current + size > end))
422	real_reserve_method (size); /* presumably noinline */	503	real_reserve_method (size); /* presumably noinline */
423	}	504	}
424		505
425	=item bool ecb_assume (cond)	506	=item ecb_assume (cond)
426		507
427	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
428	obvious.	509	obvious. This is not a function, but a statement: it cannot be used in
		510	another expression.
429		511
430	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
431	conditions that might improve code generation, but which are impossible to	513	conditions that might improve code generation, but which are impossible to
432	deduce form the code itself.	514	deduce form the code itself.
433		515
…		…
450		532
451	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
452	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
453	call will never be executed.	535	call will never be executed.
454		536
455	=item bool ecb_unreachable ()	537	=item ecb_unreachable ()
456		538
457	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
458	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
459	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.
460		542
461	=item bool ecb_prefetch (addr, rw, locality)	543	=item ecb_prefetch (addr, rw, locality)
462		544
463	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
464	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
465	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
466	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
467	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
468	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>
469	and C<locality> must be compile-time constants.	551	and C<locality> must be compile-time constants.
470		552
		553	This is a statement, not a function: you cannot use it as part of an
		554	expression.
		555
471	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
472	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,
473	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.
474		559
475	int sum = 0;	560	int sum = 0;
…		…
512		597
513	=item int ecb_ctz32 (uint32_t x)	598	=item int ecb_ctz32 (uint32_t x)
514		599
515	=item int ecb_ctz64 (uint64_t x)	600	=item int ecb_ctz64 (uint64_t x)
516		601
		602	=item int ecb_ctz (T x) [C++]
		603
517	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
518	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
519	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.
520		607
521	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>.
522		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
523	For example:	613	For example:
524		614
525	ecb_ctz32 (3) = 0	615	ecb_ctz32 (3) = 0
526	ecb_ctz32 (6) = 1	616	ecb_ctz32 (6) = 1
527		617
528	=item bool ecb_is_pot32 (uint32_t x)	618	=item bool ecb_is_pot32 (uint32_t x)
529		619
530	=item bool ecb_is_pot64 (uint32_t x)	620	=item bool ecb_is_pot64 (uint32_t x)
531		621
		622	=item bool ecb_is_pot (T x) [C++]
		623
532	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>.
533		625
534	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.
535		630
536	=item int ecb_ld32 (uint32_t x)	631	=item int ecb_ld32 (uint32_t x)
537		632
538	=item int ecb_ld64 (uint64_t x)	633	=item int ecb_ld64 (uint64_t x)
		634
		635	=item int ecb_ld64 (T x) [C++]
539		636
540	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
541	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 <
542	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
543	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
…		…
548	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
549	itself requires.	646	itself requires.
550		647
551	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>.
552		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
553	=item int ecb_popcount32 (uint32_t x)	653	=item int ecb_popcount32 (uint32_t x)
554		654
555	=item int ecb_popcount64 (uint64_t x)	655	=item int ecb_popcount64 (uint64_t x)
556		656
		657	=item int ecb_popcount (T x) [C++]
		658
557	Returns the number of bits set to 1 in C<x>.	659	Returns the number of bits set to 1 in C<x>.
558		660
559	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.
560		665
561	For example:	666	For example:
562		667
563	ecb_popcount32 (7) = 3	668	ecb_popcount32 (7) = 3
564	ecb_popcount32 (255) = 8	669	ecb_popcount32 (255) = 8
…		…
567		672
568	=item uint16_t ecb_bitrev16 (uint16_t x)	673	=item uint16_t ecb_bitrev16 (uint16_t x)
569		674
570	=item uint32_t ecb_bitrev32 (uint32_t x)	675	=item uint32_t ecb_bitrev32 (uint32_t x)
571		676
		677	=item T ecb_bitrev (T x) [C++]
		678
572	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
573	and so on.	680	and so on.
574		681
		682	The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types.
		683
575	Example:	684	Example:
576		685
577	ecb_bitrev8 (0xa7) = 0xea	686	ecb_bitrev8 (0xa7) = 0xea
578	ecb_bitrev32 (0xffcc4411) = 0x882233ff	687	ecb_bitrev32 (0xffcc4411) = 0x882233ff
579		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
580	=item uint32_t ecb_bswap16 (uint32_t x)	695	=item uint32_t ecb_bswap16 (uint32_t x)
581		696
582	=item uint32_t ecb_bswap32 (uint32_t x)	697	=item uint32_t ecb_bswap32 (uint32_t x)
583		698
584	=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)
585		702
586	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
587	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
588	C<ecb_bswap32>).	705	C<ecb_bswap32>).
589		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
590	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)	710	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
591		711
592	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)	712	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
593		713
594	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	714	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
…		…
609		729
610	Current GCC versions understand these functions and usually compile them	730	Current GCC versions understand these functions and usually compile them
611	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
612	x86).	732	x86).
613		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
614	=back	742	=back
615		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
616	=head2 FLOATING POINT FIDDLING	911	=head2 FLOATING POINT FIDDLING
617		912
618	=over 4	913	=over 4
619		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
620	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]	931	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
621		932
622	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]	933	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
623		934
624	These functions each take an argument in the native C<float> or C<double>	935	These functions each take an argument in the native C<float> or C<double>
625	type and return the IEEE 754 bit representation of it.	936	type and return the IEEE 754 bit representation of it (binary16/half,
		937	binary32/single or binary64/double precision).
626		938
627	The bit representation is just as IEEE 754 defines it, i.e. the sign bit	939	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
628	will be the most significant bit, followed by exponent and mantissa.	940	will be the most significant bit, followed by exponent and mantissa.
629		941
630	This function should work even when the native floating point format isn't	942	This function should work even when the native floating point format isn't
…		…
634		946
635	On all modern platforms (where C<ECB_STDFP> is true), the compiler should	947	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
636	be able to optimise away this function completely.	948	be able to optimise away this function completely.
637		949
638	These functions can be helpful when serialising floats to the network - you	950	These functions can be helpful when serialising floats to the network - you
639	can serialise the return value like a normal uint32_t/uint64_t.	951	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
640		952
641	Another use for these functions is to manipulate floating point values	953	Another use for these functions is to manipulate floating point values
642	directly.	954	directly.
643		955
644	Silly example: toggle the sign bit of a float.	956	Silly example: toggle the sign bit of a float.
…		…
647	/* this results in a single add instruction to toggle the bit, and 4 extra */	959	/* this results in a single add instruction to toggle the bit, and 4 extra */
648	/* instructions to move the float value to an integer register and back. */	960	/* instructions to move the float value to an integer register and back. */
649		961
650	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)	962	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
651		963
		964	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		965
652	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]	966	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
653		967
654	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]	968	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
655		969
656	The reverse operation of the previos function - takes the bit representation	970	The reverse operation of the previous function - takes the bit
657	of an IEEE binary32 or binary64 number and converts it to the native C<float>	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
658	or C<double> format.	973	C<double> format.
659		974
660	This function should work even when the native floating point format isn't	975	This function should work even when the native floating point format isn't
661	IEEE compliant, of course at a speed and code size penalty, and of course	976	IEEE compliant, of course at a speed and code size penalty, and of course
662	also within reasonable limits (it tries to convert normals and denormals,	977	also within reasonable limits (it tries to convert normals and denormals,
663	and might be lucky for infinities, and with extraordinary luck, also for	978	and might be lucky for infinities, and with extraordinary luck, also for
664	negative zero).	979	negative zero).
665		980
666	On all modern platforms (where C<ECB_STDFP> is true), the compiler should	981	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
667	be able to optimise away this function completely.	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.
668		996
669	=back	997	=back
670		998
671	=head2 ARITHMETIC	999	=head2 ARITHMETIC
672		1000
…		…
729		1057
730	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.
731		1059
732	=over 4	1060	=over 4
733		1061
734	=item ECB_NO_THRADS	1062	=item ECB_NO_THREADS
735		1063
736	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
737	be defined, in which case memory fences (and similar constructs) are	1065	be defined, in which case memory fences (and similar constructs) are
738	completely removed, leading to more efficient code and fewer dependencies.	1066	completely removed, leading to more efficient code and fewer dependencies.
739		1067
…		…
753	dependencies on the math library (usually called F<-lm>) - these are	1081	dependencies on the math library (usually called F<-lm>) - these are
754	marked with [-UECB_NO_LIBM].	1082	marked with [-UECB_NO_LIBM].
755		1083
756	=back	1084	=back
757		1085
		1086	=head1 UNDOCUMENTED FUNCTIONALITY
758		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 1.50 by root, Thu Jun 28 20:20:27 2012 UTC vs.
Revision 1.84 by root, Mon Jan 20 21:10:16 2020 UTC