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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.27 by root, Wed Jun 1 01:29:36 2011 UTC vs.
Revision 1.83 by root, Mon Jan 20 21:08:19 2020 UTC

…		…
54	only a generic name is used (C<expr>, C<cond>, C<value> and so on), then	54	only a generic name is used (C<expr>, C<cond>, C<value> and so on), then
55	the corresponding function relies on C to implement the correct types, and	55	the corresponding function relies on C to implement the correct types, and
56	is usually implemented as a macro. Specifically, a "bool" in this manual	56	is usually implemented as a macro. Specifically, a "bool" in this manual
57	refers to any kind of boolean value, not a specific type.	57	refers to any kind of boolean value, not a specific type.
58		58
		59	=head2 TYPES / TYPE SUPPORT
		60
		61	ecb.h makes sure that the following types are defined (in the expected way):
		62
		63	int8_t uint8_
		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
		71	intptr_t uintptr_t
		72
		73	The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this
		74	platform (currently C<4> or C<8>) and can be used in preprocessor
		75	expressions.
		76
		77	For C<ptrdiff_t> and C<size_t> use C<stddef.h>/C<cstddef>.
		78
		79	=head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS
		80
		81	All the following symbols expand to an expression that can be tested in
		82	preprocessor instructions as well as treated as a boolean (use C<!!> to
		83	ensure it's either C<0> or C<1> if you need that).
		84
		85	=over 4
		86
		87	=item ECB_C
		88
		89	True if the implementation defines the C<__STDC__> macro to a true value,
		90	while not claiming to be C++, i..e C, but not C++.
		91
		92	=item ECB_C99
		93
		94	True if the implementation claims to be compliant to C99 (ISO/IEC
		95	9899:1999) or any later version, while not claiming to be C++.
		96
		97	Note that later versions (ECB_C11) remove core features again (for
		98	example, variable length arrays).
		99
		100	=item ECB_C11, ECB_C17
		101
		102	True if the implementation claims to be compliant to C11/C17 (ISO/IEC
		103	9899:2011, :20187) or any later version, while not claiming to be C++.
		104
		105	=item ECB_CPP
		106
		107	True if the implementation defines the C<__cplusplus__> macro to a true
		108	value, which is typically true for C++ compilers.
		109
		110	=item ECB_CPP11, ECB_CPP14, ECB_CPP17
		111
		112	True if the implementation claims to be compliant to C++11/C++14/C++17
		113	(ISO/IEC 14882:2011, :2014, :2017) or any later version.
		114
		115	Note that many C++20 features will likely have their own feature test
		116	macros (see e.g. L<http://eel.is/c++draft/cpp.predefined#1.8>).
		117
		118	=item ECB_OPTIMIZE_SIZE
		119
		120	Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol
		121	can also be defined before including F<ecb.h>, in which case it will be
		122	unchanged.
		123
		124	=item ECB_GCC_VERSION (major, minor)
		125
		126	Expands to a true value (suitable for testing in by the preprocessor)
		127	if the compiler used is GNU C and the version is the given version, or
		128	higher.
		129
		130	This macro tries to return false on compilers that claim to be GCC
		131	compatible but aren't.
		132
		133	=item ECB_EXTERN_C
		134
		135	Expands to C<extern "C"> in C++, and a simple C<extern> in C.
		136
		137	This can be used to declare a single external C function:
		138
		139	ECB_EXTERN_C int printf (const char *format, ...);
		140
		141	=item ECB_EXTERN_C_BEG / ECB_EXTERN_C_END
		142
		143	These two macros can be used to wrap multiple C<extern "C"> definitions -
		144	they expand to nothing in C.
		145
		146	They are most useful in header files:
		147
		148	ECB_EXTERN_C_BEG
		149
		150	int mycfun1 (int x);
		151	int mycfun2 (int x);
		152
		153	ECB_EXTERN_C_END
		154
		155	=item ECB_STDFP
		156
		157	If this evaluates to a true value (suitable for testing in by the
		158	preprocessor), then C<float> and C<double> use IEEE 754 single/binary32
		159	and double/binary64 representations internally I<and> the endianness of
		160	both types match the endianness of C<uint32_t> and C<uint64_t>.
		161
		162	This means you can just copy the bits of a C<float> (or C<double>) to an
		163	C<uint32_t> (or C<uint64_t>) and get the raw IEEE 754 bit representation
		164	without having to think about format or endianness.
		165
		166	This is true for basically all modern platforms, although F<ecb.h> might
		167	not be able to deduce this correctly everywhere and might err on the safe
		168	side.
		169
		170	=item ECB_AMD64, ECB_AMD64_X32
		171
		172	These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32
		173	ABI, respectively, and undefined elsewhere.
		174
		175	The designers of the new X32 ABI for some inexplicable reason decided to
		176	make it look exactly like amd64, even though it's completely incompatible
		177	to that ABI, breaking about every piece of software that assumed that
		178	C<__x86_64> stands for, well, the x86-64 ABI, making these macros
		179	necessary.
		180
		181	=back
		182
		183	=head2 MACRO TRICKERY
		184
		185	=over 4
		186
		187	=item ECB_CONCAT (a, b)
		188
		189	Expands any macros in C<a> and C<b>, then concatenates the result to form
		190	a single token. This is mainly useful to form identifiers from components,
		191	e.g.:
		192
		193	#define S1 str
		194	#define S2 cpy
		195
		196	ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src);
		197
		198	=item ECB_STRINGIFY (arg)
		199
		200	Expands any macros in C<arg> and returns the stringified version of
		201	it. This is mainly useful to get the contents of a macro in string form,
		202	e.g.:
		203
		204	#define SQL_LIMIT 100
		205	sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT));
		206
		207	=item ECB_STRINGIFY_EXPR (expr)
		208
		209	Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it
		210	is a valid expression. This is useful to catch typos or cases where the
		211	macro isn't available:
		212
		213	#include <errno.h>
		214
		215	ECB_STRINGIFY (EDOM); // "33" (on my system at least)
		216	ECB_STRINGIFY_EXPR (EDOM); // "33"
		217
		218	// now imagine we had a typo:
		219
		220	ECB_STRINGIFY (EDAM); // "EDAM"
		221	ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined
		222
		223	=back
		224
59	=head2 GCC ATTRIBUTES	225	=head2 ATTRIBUTES
60		226
61	A major part of libecb deals with GCC attributes. These are additional	227	A major part of libecb deals with additional attributes that can be
62	attributes that you can assign to functions, variables and sometimes even	228	assigned to functions, variables and sometimes even types - much like
63	types - much like C<const> or C<volatile> in C.	229	C<const> or C<volatile> in C. They are implemented using either GCC
64		230	attributes or other compiler/language specific features. Attributes
65	While GCC allows declarations to show up in many surprising places,
66	but not in many expected places, the safest way is to put attribute
67	declarations before the whole declaration:	231	declarations must be put before the whole declaration:
68		232
69	ecb_const int mysqrt (int a);	233	ecb_const int mysqrt (int a);
70	ecb_unused int i;	234	ecb_unused int i;
71		235
72	For variables, it is often nicer to put the attribute after the name, and
73	avoid multiple declarations using commas:
74
75	int i ecb_unused;
76
77	=over 4	236	=over 4
78
79	=item ecb_attribute ((attrs...))
80
81	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
82	nothing on other compilers, so the effect is that only GCC sees these.
83
84	Example: use the C<deprecated> attribute on a function.
85
86	ecb_attribute((__deprecated__)) void
87	do_not_use_me_anymore (void);
88		237
89	=item ecb_unused	238	=item ecb_unused
90		239
91	Marks a function or a variable as "unused", which simply suppresses a	240	Marks a function or a variable as "unused", which simply suppresses a
92	warning by GCC when it detects it as unused. This is useful when you e.g.	241	warning by GCC when it detects it as unused. This is useful when you e.g.
93	declare a variable but do not always use it:	242	declare a variable but do not always use it:
94		243
95	{	244	{
96	int var ecb_unused;	245	ecb_unused int var;
97		246
98	#ifdef SOMECONDITION	247	#ifdef SOMECONDITION
99	var = ...;	248	var = ...;
100	return var;	249	return var;
101	#else	250	#else
102	return 0;	251	return 0;
103	#endif	252	#endif
104	}	253	}
105		254
		255	=item ecb_deprecated
		256
		257	Similar to C<ecb_unused>, but marks a function, variable or type as
		258	deprecated. This makes some compilers warn when the type is used.
		259
		260	=item ecb_deprecated_message (message)
		261
		262	Same as C<ecb_deprecated>, but if possible, the specified diagnostic is
		263	used instead of a generic depreciation message when the object is being
		264	used.
		265
		266	=item ecb_inline
		267
		268	Expands either to (a compiler-specific equivalent of) C<static inline> or
		269	to just C<static>, if inline isn't supported. It should be used to declare
		270	functions that should be inlined, for code size or speed reasons.
		271
		272	Example: inline this function, it surely will reduce codesize.
		273
		274	ecb_inline int
		275	negmul (int a, int b)
		276	{
		277	return - (a * b);
		278	}
		279
106	=item ecb_noinline	280	=item ecb_noinline
107		281
108	Prevent a function from being inlined - it might be optimised away, but	282	Prevents a function from being inlined - it might be optimised away, but
109	not inlined into other functions. This is useful if you know your function	283	not inlined into other functions. This is useful if you know your function
110	is rarely called and large enough for inlining not to be helpful.	284	is rarely called and large enough for inlining not to be helpful.
111		285
112	=item ecb_noreturn	286	=item ecb_noreturn
113		287
…		…
123	}	297	}
124		298
125	In this case, the compiler would probably be smart enough to deduce it on	299	In this case, the compiler would probably be smart enough to deduce it on
126	its own, so this is mainly useful for declarations.	300	its own, so this is mainly useful for declarations.
127		301
		302	=item ecb_restrict
		303
		304	Expands to the C<restrict> keyword or equivalent on compilers that support
		305	them, and to nothing on others. Must be specified on a pointer type or
		306	an array index to indicate that the memory doesn't alias with any other
		307	restricted pointer in the same scope.
		308
		309	Example: multiply a vector, and allow the compiler to parallelise the
		310	loop, because it knows it doesn't overwrite input values.
		311
		312	void
		313	multiply (ecb_restrict float *src,
		314	ecb_restrict float *dst,
		315	int len, float factor)
		316	{
		317	int i;
		318
		319	for (i = 0; i < len; ++i)
		320	dst [i] = src [i] * factor;
		321	}
		322
128	=item ecb_const	323	=item ecb_const
129		324
130	Declares that the function only depends on the values of its arguments,	325	Declares that the function only depends on the values of its arguments,
131	much like a mathematical function. It specifically does not read or write	326	much like a mathematical function. It specifically does not read or write
132	any memory any arguments might point to, global variables, or call any	327	any memory any arguments might point to, global variables, or call any
…		…
192	functions only called in exceptional or rare cases.	387	functions only called in exceptional or rare cases.
193		388
194	=item ecb_artificial	389	=item ecb_artificial
195		390
196	Declares the function as "artificial", in this case meaning that this	391	Declares the function as "artificial", in this case meaning that this
197	function is not really mean to be a function, but more like an accessor	392	function is not really meant to be a function, but more like an accessor
198	- many methods in C++ classes are mere accessor functions, and having a	393	- many methods in C++ classes are mere accessor functions, and having a
199	crash reported in such a method, or single-stepping through them, is not	394	crash reported in such a method, or single-stepping through them, is not
200	usually so helpful, especially when it's inlined to just a few instructions.	395	usually so helpful, especially when it's inlined to just a few instructions.
201		396
202	Marking them as artificial will instruct the debugger about just this,	397	Marking them as artificial will instruct the debugger about just this,
…		…
222		417
223	=head2 OPTIMISATION HINTS	418	=head2 OPTIMISATION HINTS
224		419
225	=over 4	420	=over 4
226		421
227	=item bool ecb_is_constant(expr)	422	=item bool ecb_is_constant (expr)
228		423
229	Returns true iff the expression can be deduced to be a compile-time	424	Returns true iff the expression can be deduced to be a compile-time
230	constant, and false otherwise.	425	constant, and false otherwise.
231		426
232	For example, when you have a C<rndm16> function that returns a 16 bit	427	For example, when you have a C<rndm16> function that returns a 16 bit
…		…
250	return is_constant (n) && !(n & (n - 1))	445	return is_constant (n) && !(n & (n - 1))
251	? rndm16 () & (num - 1)	446	? rndm16 () & (num - 1)
252	: (n * (uint32_t)rndm16 ()) >> 16;	447	: (n * (uint32_t)rndm16 ()) >> 16;
253	}	448	}
254		449
255	=item bool ecb_expect (expr, value)	450	=item ecb_expect (expr, value)
256		451
257	Evaluates C<expr> and returns it. In addition, it tells the compiler that	452	Evaluates C<expr> and returns it. In addition, it tells the compiler that
258	the C<expr> evaluates to C<value> a lot, which can be used for static	453	the C<expr> evaluates to C<value> a lot, which can be used for static
259	branch optimisations.	454	branch optimisations.
260		455
…		…
307	{	502	{
308	if (ecb_expect_false (current + size > end))	503	if (ecb_expect_false (current + size > end))
309	real_reserve_method (size); /* presumably noinline */	504	real_reserve_method (size); /* presumably noinline */
310	}	505	}
311		506
312	=item bool ecb_assume (cond)	507	=item ecb_assume (cond)
313		508
314	Try to tell the compiler that some condition is true, even if it's not	509	Tries to tell the compiler that some condition is true, even if it's not
315	obvious.	510	obvious. This is not a function, but a statement: it cannot be used in
		511	another expression.
316		512
317	This can be used to teach the compiler about invariants or other	513	This can be used to teach the compiler about invariants or other
318	conditions that might improve code generation, but which are impossible to	514	conditions that might improve code generation, but which are impossible to
319	deduce form the code itself.	515	deduce form the code itself.
320		516
…		…
337		533
338	Then the compiler I<might> be able to optimise out the second call	534	Then the compiler I<might> be able to optimise out the second call
339	completely, as it knows that C<< current + 1 > end >> is false and the	535	completely, as it knows that C<< current + 1 > end >> is false and the
340	call will never be executed.	536	call will never be executed.
341		537
342	=item bool ecb_unreachable ()	538	=item ecb_unreachable ()
343		539
344	This function does nothing itself, except tell the compiler that it will	540	This function does nothing itself, except tell the compiler that it will
345	never be executed. Apart from suppressing a warning in some cases, this	541	never be executed. Apart from suppressing a warning in some cases, this
346	function can be used to implement C<ecb_assume> or similar functions.	542	function can be used to implement C<ecb_assume> or similar functionality.
347		543
348	=item bool ecb_prefetch (addr, rw, locality)	544	=item ecb_prefetch (addr, rw, locality)
349		545
350	Tells the compiler to try to prefetch memory at the given C<addr>ess	546	Tells the compiler to try to prefetch memory at the given C<addr>ess
351	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of	547	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of
352	C<0> means that there will only be one access later, C<3> means that	548	C<0> means that there will only be one access later, C<3> means that
353	the data will likely be accessed very often, and values in between mean	549	the data will likely be accessed very often, and values in between mean
354	something... in between. The memory pointed to by the address does not	550	something... in between. The memory pointed to by the address does not
355	need to be accessible (it could be a null pointer for example), but C<rw>	551	need to be accessible (it could be a null pointer for example), but C<rw>
356	and C<locality> must be compile-time constants.	552	and C<locality> must be compile-time constants.
357		553
		554	This is a statement, not a function: you cannot use it as part of an
		555	expression.
		556
358	An obvious way to use this is to prefetch some data far away, in a big	557	An obvious way to use this is to prefetch some data far away, in a big
359	array you loop over. This prefetches memory some 128 array elements later,	558	array you loop over. This prefetches memory some 128 array elements later,
360	in the hope that it will be ready when the CPU arrives at that location.	559	in the hope that it will be ready when the CPU arrives at that location.
361		560
362	int sum = 0;	561	int sum = 0;
…		…
381	After processing the node, (part of) the next node might already be in	580	After processing the node, (part of) the next node might already be in
382	cache.	581	cache.
383		582
384	=back	583	=back
385		584
386	=head2 BIT FIDDLING / BITSTUFFS	585	=head2 BIT FIDDLING / BIT WIZARDRY
387		586
388	=over 4	587	=over 4
389		588
390	=item bool ecb_big_endian ()	589	=item bool ecb_big_endian ()
391		590
…		…
397		596
398	On systems that are neither, their return values are unspecified.	597	On systems that are neither, their return values are unspecified.
399		598
400	=item int ecb_ctz32 (uint32_t x)	599	=item int ecb_ctz32 (uint32_t x)
401		600
		601	=item int ecb_ctz64 (uint64_t x)
		602
		603	=item int ecb_ctz (T x) [C++]
		604
402	Returns the index of the least significant bit set in C<x> (or	605	Returns the index of the least significant bit set in C<x> (or
403	equivalently the number of bits set to 0 before the least significant bit	606	equivalently the number of bits set to 0 before the least significant bit
404	set), starting from 0. If C<x> is 0 the result is undefined. A common use	607	set), starting from 0. If C<x> is 0 the result is undefined.
405	case is to compute the integer binary logarithm, i.e., C<floor (log2	608
		609	For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.
		610
		611	The overloaded C++ C<ecb_ctz> function supports C<uint8_t>, C<uint16_t>,
		612	C<uint32_t> and C<uint64_t> types.
		613
406	(n))>. For example:	614	For example:
407		615
408	ecb_ctz32 (3) = 0	616	ecb_ctz32 (3) = 0
409	ecb_ctz32 (6) = 1	617	ecb_ctz32 (6) = 1
410		618
		619	=item bool ecb_is_pot32 (uint32_t x)
		620
		621	=item bool ecb_is_pot64 (uint32_t x)
		622
		623	=item bool ecb_is_pot (T x) [C++]
		624
		625	Returns true iff C<x> is a power of two or C<x == 0>.
		626
		627	For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>.
		628
		629	The overloaded C++ C<ecb_is_pot> function supports C<uint8_t>, C<uint16_t>,
		630	C<uint32_t> and C<uint64_t> types.
		631
		632	=item int ecb_ld32 (uint32_t x)
		633
		634	=item int ecb_ld64 (uint64_t x)
		635
		636	=item int ecb_ld64 (T x) [C++]
		637
		638	Returns the index of the most significant bit set in C<x>, or the number
		639	of digits the number requires in binary (so that C<< 2**ld <= x <
		640	2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is
		641	to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for
		642	example to see how many bits a certain number requires to be encoded.
		643
		644	This function is similar to the "count leading zero bits" function, except
		645	that that one returns how many zero bits are "in front" of the number (in
		646	the given data type), while C<ecb_ld> returns how many bits the number
		647	itself requires.
		648
		649	For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.
		650
		651	The overloaded C++ C<ecb_ld> function supports C<uint8_t>, C<uint16_t>,
		652	C<uint32_t> and C<uint64_t> types.
		653
411	=item int ecb_popcount32 (uint32_t x)	654	=item int ecb_popcount32 (uint32_t x)
412		655
		656	=item int ecb_popcount64 (uint64_t x)
		657
		658	=item int ecb_popcount (T x) [C++]
		659
413	Returns the number of bits set to 1 in C<x>. For example:	660	Returns the number of bits set to 1 in C<x>.
		661
		662	For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.
		663
		664	The overloaded C++ C<ecb_popcount> function supports C<uint8_t>, C<uint16_t>,
		665	C<uint32_t> and C<uint64_t> types.
		666
		667	For example:
414		668
415	ecb_popcount32 (7) = 3	669	ecb_popcount32 (7) = 3
416	ecb_popcount32 (255) = 8	670	ecb_popcount32 (255) = 8
417		671
		672	=item uint8_t ecb_bitrev8 (uint8_t x)
		673
		674	=item uint16_t ecb_bitrev16 (uint16_t x)
		675
		676	=item uint32_t ecb_bitrev32 (uint32_t x)
		677
		678	=item T ecb_bitrev (T x) [C++]
		679
		680	Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1
		681	and so on.
		682
		683	The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types.
		684
		685	Example:
		686
		687	ecb_bitrev8 (0xa7) = 0xea
		688	ecb_bitrev32 (0xffcc4411) = 0x882233ff
		689
		690	=item T ecb_bitrev (T x) [C++]
		691
		692	Overloaded C++ bitrev function.
		693
		694	C<T> must be one of C<uint8_t>, C<uint16_t> or C<uint32_t>.
		695
418	=item uint32_t ecb_bswap16 (uint32_t x)	696	=item uint32_t ecb_bswap16 (uint32_t x)
419		697
420	=item uint32_t ecb_bswap32 (uint32_t x)	698	=item uint32_t ecb_bswap32 (uint32_t x)
421		699
		700	=item uint64_t ecb_bswap64 (uint64_t x)
		701
		702	=item T ecb_bswap (T x)
		703
422	These two functions return the value of the 16-bit (32-bit) value C<x>	704	These functions return the value of the 16-bit (32-bit, 64-bit) value
423	after reversing the order of bytes (0x11223344 becomes 0x44332211).	705	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in
		706	C<ecb_bswap32>).
		707
		708	The overloaded C++ C<ecb_bswap> function supports C<uint8_t>, C<uint16_t>,
		709	C<uint32_t> and C<uint64_t> types.
		710
		711	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
		712
		713	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
		714
		715	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
		716
		717	=item uint64_t ecb_rotl64 (uint64_t x, unsigned int count)
		718
		719	=item uint8_t ecb_rotr8 (uint8_t x, unsigned int count)
		720
		721	=item uint16_t ecb_rotr16 (uint16_t x, unsigned int count)
424		722
425	=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)	723	=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)
426		724
427	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	725	=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)
428		726
429	These two functions return the value of C<x> after rotating all the bits	727	These two families of functions return the value of C<x> after rotating
430	by C<count> positions to the right or left respectively.	728	all the bits by C<count> positions to the right (C<ecb_rotr>) or left
		729	(C<ecb_rotl>).
431		730
432	Current GCC versions understand these functions and usually compile them	731	Current GCC versions understand these functions and usually compile them
433	to "optimal" code (e.g. a single C<roll> on x86).	732	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
		733	x86).
		734
		735	=item T ecb_rotl (T x, unsigned int count) [C++]
		736
		737	=item T ecb_rotr (T x, unsigned int count) [C++]
		738
		739	Overloaded C++ rotl/rotr functions.
		740
		741	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		742
		743	=back
		744
		745	=head2 HOST ENDIANNESS CONVERSION
		746
		747	=over 4
		748
		749	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)
		750
		751	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)
		752
		753	=item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v)
		754
		755	=item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v)
		756
		757	=item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v)
		758
		759	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)
		760
		761	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.
		762
		763	The naming convention is C<ecb_>(C<be>\|C<le>)C<_u>C<16\|32\|64>C<_to_host>,
		764	where C<be> and C<le> stand for big endian and little endian, respectively.
		765
		766	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)
		767
		768	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)
		769
		770	=item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v)
		771
		772	=item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v)
		773
		774	=item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v)
		775
		776	=item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v)
		777
		778	Like above, but converts I<from> host byte order to the specified
		779	endianness.
		780
		781	=back
		782
		783	In C++ the following additional template functions are supported:
		784
		785	=over 4
		786
		787	=item T ecb_be_to_host (T v)
		788
		789	=item T ecb_le_to_host (T v)
		790
		791	=item T ecb_host_to_be (T v)
		792
		793	=item T ecb_host_to_le (T v)
		794
		795	These functions work like their C counterparts, above, but use templates,
		796	which make them useful in generic code.
		797
		798	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>
		799	(so unlike their C counterparts, there is a version for C<uint8_t>, which
		800	again can be useful in generic code).
		801
		802	=head2 UNALIGNED LOAD/STORE
		803
		804	These function load or store unaligned multi-byte values.
		805
		806	=over 4
		807
		808	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)
		809
		810	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)
		811
		812	=item uint_fast64_t ecb_peek_u64_u (const void *ptr)
		813
		814	These functions load an unaligned, unsigned 16, 32 or 64 bit value from
		815	memory.
		816
		817	=item uint_fast16_t ecb_peek_be_u16_u (const void *ptr)
		818
		819	=item uint_fast32_t ecb_peek_be_u32_u (const void *ptr)
		820
		821	=item uint_fast64_t ecb_peek_be_u64_u (const void *ptr)
		822
		823	=item uint_fast16_t ecb_peek_le_u16_u (const void *ptr)
		824
		825	=item uint_fast32_t ecb_peek_le_u32_u (const void *ptr)
		826
		827	=item uint_fast64_t ecb_peek_le_u64_u (const void *ptr)
		828
		829	Like above, but additionally convert from big endian (C<be>) or little
		830	endian (C<le>) byte order to host byte order while doing so.
		831
		832	=item ecb_poke_u16_u (void *ptr, uint16_t v)
		833
		834	=item ecb_poke_u32_u (void *ptr, uint32_t v)
		835
		836	=item ecb_poke_u64_u (void *ptr, uint64_t v)
		837
		838	These functions store an unaligned, unsigned 16, 32 or 64 bit value to
		839	memory.
		840
		841	=item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v)
		842
		843	=item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v)
		844
		845	=item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v)
		846
		847	=item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v)
		848
		849	=item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v)
		850
		851	=item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v)
		852
		853	Like above, but additionally convert from host byte order to big endian
		854	(C<be>) or little endian (C<le>) byte order while doing so.
		855
		856	=back
		857
		858	In C++ the following additional template functions are supported:
		859
		860	=over 4
		861
		862	=item T ecb_peek<T> (const void *ptr)
		863
		864	=item T ecb_peek_be<T> (const void *ptr)
		865
		866	=item T ecb_peek_le<T> (const void *ptr)
		867
		868	=item T ecb_peek_u<T> (const void *ptr)
		869
		870	=item T ecb_peek_be_u<T> (const void *ptr)
		871
		872	=item T ecb_peek_le_u<T> (const void *ptr)
		873
		874	Similarly to their C counterparts, these functions load an unsigned 8, 16,
		875	32 or 64 bit value from memory, with optional conversion from big/little
		876	endian.
		877
		878	Since the type cannot be deduced, it has to be specified explicitly, e.g.
		879
		880	uint_fast16_t v = ecb_peek<uint16_t> (ptr);
		881
		882	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		883
		884	Unlike their C counterparts, these functions support 8 bit quantities
		885	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		886	all of which hopefully makes them more useful in generic code.
		887
		888	=item ecb_poke (void *ptr, T v)
		889
		890	=item ecb_poke_be (void *ptr, T v)
		891
		892	=item ecb_poke_le (void *ptr, T v)
		893
		894	=item ecb_poke_u (void *ptr, T v)
		895
		896	=item ecb_poke_be_u (void *ptr, T v)
		897
		898	=item ecb_poke_le_u (void *ptr, T v)
		899
		900	Again, similarly to their C counterparts, these functions store an
		901	unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to
		902	big/little endian.
		903
		904	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		905
		906	Unlike their C counterparts, these functions support 8 bit quantities
		907	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		908	all of which hopefully makes them more useful in generic code.
		909
		910	=back
		911
		912	=head2 FLOATING POINT FIDDLING
		913
		914	=over 4
		915
		916	=item ECB_INFINITY [-UECB_NO_LIBM]
		917
		918	Evaluates to positive infinity if supported by the platform, otherwise to
		919	a truly huge number.
		920
		921	=item ECB_NAN [-UECB_NO_LIBM]
		922
		923	Evaluates to a quiet NAN if supported by the platform, otherwise to
		924	C<ECB_INFINITY>.
		925
		926	=item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM]
		927
		928	Same as C<ldexpf>, but always available.
		929
		930	=item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM]
		931
		932	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
		933
		934	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
		935
		936	These functions each take an argument in the native C<float> or C<double>
		937	type and return the IEEE 754 bit representation of it (binary16/half,
		938	binary32/single or binary64/double precision).
		939
		940	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
		941	will be the most significant bit, followed by exponent and mantissa.
		942
		943	This function should work even when the native floating point format isn't
		944	IEEE compliant, of course at a speed and code size penalty, and of course
		945	also within reasonable limits (it tries to convert NaNs, infinities and
		946	denormals, but will likely convert negative zero to positive zero).
		947
		948	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		949	be able to optimise away this function completely.
		950
		951	These functions can be helpful when serialising floats to the network - you
		952	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
		953
		954	Another use for these functions is to manipulate floating point values
		955	directly.
		956
		957	Silly example: toggle the sign bit of a float.
		958
		959	/* On gcc-4.7 on amd64, */
		960	/* this results in a single add instruction to toggle the bit, and 4 extra */
		961	/* instructions to move the float value to an integer register and back. */
		962
		963	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
		964
		965	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		966
		967	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
		968
		969	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
		970
		971	The reverse operation of the previous function - takes the bit
		972	representation of an IEEE binary16, binary32 or binary64 number (half,
		973	single or double precision) and converts it to the native C<float> or
		974	C<double> format.
		975
		976	This function should work even when the native floating point format isn't
		977	IEEE compliant, of course at a speed and code size penalty, and of course
		978	also within reasonable limits (it tries to convert normals and denormals,
		979	and might be lucky for infinities, and with extraordinary luck, also for
		980	negative zero).
		981
		982	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		983	be able to optimise away this function completely.
		984
		985	=item uint16_t ecb_binary32_to_binary16 (uint32_t x)
		986
		987	=item uint32_t ecb_binary16_to_binary32 (uint16_t x)
		988
		989	Convert a IEEE binary32/single precision to binary16/half format, and vice
		990	versa, handling all details (round-to-nearest-even, subnormals, infinity
		991	and NaNs) correctly.
		992
		993	These are functions are available under C<-DECB_NO_LIBM>, since
		994	they do not rely on the platform floating point format. The
		995	C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are
		996	usually what you want.
434		997
435	=back	998	=back
436		999
437	=head2 ARITHMETIC	1000	=head2 ARITHMETIC
438		1001
…		…
448	C<ecb_mod> implements the mathematical modulo operation, which is missing	1011	C<ecb_mod> implements the mathematical modulo operation, which is missing
449	in the language.	1012	in the language.
450		1013
451	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be	1014	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be
452	negatable, that is, both C<m> and C<-m> must be representable in its	1015	negatable, that is, both C<m> and C<-m> must be representable in its
453	type (this typically includes the minimum signed integer value, the same	1016	type (this typically excludes the minimum signed integer value, the same
454	limitation as for C</> and C<%> in C).	1017	limitation as for C</> and C<%> in C).
455		1018
456	Current GCC versions compile this into an efficient branchless sequence on	1019	Current GCC versions compile this into an efficient branchless sequence on
457	many systems.	1020	almost all CPUs.
458		1021
459	For example, when you want to rotate forward through the members of an	1022	For example, when you want to rotate forward through the members of an
460	array for increasing C<m> (which might be negative), then you should use	1023	array for increasing C<m> (which might be negative), then you should use
461	C<ecb_mod>, as the C<%> operator might give either negative results, or	1024	C<ecb_mod>, as the C<%> operator might give either negative results, or
462	change direction for negative values:	1025	change direction for negative values:
463		1026
464	for (m = -100; m <= 100; ++m)	1027	for (m = -100; m <= 100; ++m)
465	int elem = myarray [ecb_mod (m, ecb_array_length (myarray))];	1028	int elem = myarray [ecb_mod (m, ecb_array_length (myarray))];
466		1029
		1030	=item x = ecb_div_rd (val, div)
		1031
		1032	=item x = ecb_div_ru (val, div)
		1033
		1034	Returns C<val> divided by C<div> rounded down or up, respectively.
		1035	C<val> and C<div> must have integer types and C<div> must be strictly
		1036	positive. Note that these functions are implemented with macros in C
		1037	and with function templates in C++.
		1038
467	=back	1039	=back
468		1040
469	=head2 UTILITY	1041	=head2 UTILITY
470		1042
471	=over 4	1043	=over 4
…		…
480	for (i = 0; i < ecb_array_length (primes); i++)	1052	for (i = 0; i < ecb_array_length (primes); i++)
481	sum += primes [i];	1053	sum += primes [i];
482		1054
483	=back	1055	=back
484		1056
		1057	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF
485		1058
		1059	These symbols need to be defined before including F<ecb.h> the first time.
		1060
		1061	=over 4
		1062
		1063	=item ECB_NO_THREADS
		1064
		1065	If F<ecb.h> is never used from multiple threads, then this symbol can
		1066	be defined, in which case memory fences (and similar constructs) are
		1067	completely removed, leading to more efficient code and fewer dependencies.
		1068
		1069	Setting this symbol to a true value implies C<ECB_NO_SMP>.
		1070
		1071	=item ECB_NO_SMP
		1072
		1073	The weaker version of C<ECB_NO_THREADS> - if F<ecb.h> is used from
		1074	multiple threads, but never concurrently (e.g. if the system the program
		1075	runs on has only a single CPU with a single core, no hyperthreading and so
		1076	on), then this symbol can be defined, leading to more efficient code and
		1077	fewer dependencies.
		1078
		1079	=item ECB_NO_LIBM
		1080
		1081	When defined to C<1>, do not export any functions that might introduce
		1082	dependencies on the math library (usually called F<-lm>) - these are
		1083	marked with [-UECB_NO_LIBM].
		1084
		1085	=back
		1086
		1087	=head1 UNDOCUMENTED FUNCTIONALITY
		1088
		1089	F<ecb.h> is full of undocumented functionality as well, some of which is
		1090	intended to be internal-use only, some of which we forgot to document, and
		1091	some of which we hide because we are not sure we will keep the interface
		1092	stable.
		1093
		1094	While you are welcome to rummage around and use whatever you find useful
		1095	(we can't stop you), keep in mind that we will change undocumented
		1096	functionality in incompatible ways without thinking twice, while we are
		1097	considerably more conservative with documented things.
		1098
		1099	=head1 AUTHORS
		1100
		1101	C<libecb> is designed and maintained by:
		1102
		1103	Emanuele Giaquinta <e.giaquinta@glauco.it>
		1104	Marc Alexander Lehmann <schmorp@schmorp.de>
		1105
		1106

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Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.27 by root, Wed Jun 1 01:29:36 2011 UTC vs.
Revision 1.83 by root, Mon Jan 20 21:08:19 2020 UTC