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

Comparing libecb/ecb.pod (file contents):
Revision 1.41 by root, Mon May 28 08:40:25 2012 UTC vs.
Revision 1.76 by root, Mon Jan 20 13:13:56 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>).	74	platform (currently C<4> or C<8>) and can be used in preprocessor
		75	expressions.
69		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++.
		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	=item ECB_GCC_VERSION (major, minor)
		116
		117	Expands to a true value (suitable for testing in by the preprocessor)
		118	if the compiler used is GNU C and the version is the given version, or
		119	higher.
		120
		121	This macro tries to return false on compilers that claim to be GCC
		122	compatible but aren't.
		123
		124	=item ECB_EXTERN_C
		125
		126	Expands to C<extern "C"> in C++, and a simple C<extern> in C.
		127
		128	This can be used to declare a single external C function:
		129
		130	ECB_EXTERN_C int printf (const char *format, ...);
		131
		132	=item ECB_EXTERN_C_BEG / ECB_EXTERN_C_END
		133
		134	These two macros can be used to wrap multiple C<extern "C"> definitions -
		135	they expand to nothing in C.
		136
		137	They are most useful in header files:
		138
		139	ECB_EXTERN_C_BEG
		140
		141	int mycfun1 (int x);
		142	int mycfun2 (int x);
		143
		144	ECB_EXTERN_C_END
		145
		146	=item ECB_STDFP
		147
		148	If this evaluates to a true value (suitable for testing in by the
		149	preprocessor), then C<float> and C<double> use IEEE 754 single/binary32
		150	and double/binary64 representations internally I<and> the endianness of
		151	both types match the endianness of C<uint32_t> and C<uint64_t>.
		152
		153	This means you can just copy the bits of a C<float> (or C<double>) to an
		154	C<uint32_t> (or C<uint64_t>) and get the raw IEEE 754 bit representation
		155	without having to think about format or endianness.
		156
		157	This is true for basically all modern platforms, although F<ecb.h> might
		158	not be able to deduce this correctly everywhere and might err on the safe
		159	side.
		160
		161	=item ECB_AMD64, ECB_AMD64_X32
		162
		163	These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32
		164	ABI, respectively, and undefined elsewhere.
		165
		166	The designers of the new X32 ABI for some inexplicable reason decided to
		167	make it look exactly like amd64, even though it's completely incompatible
		168	to that ABI, breaking about every piece of software that assumed that
		169	C<__x86_64> stands for, well, the x86-64 ABI, making these macros
		170	necessary.
		171
		172	=back
		173
		174	=head2 MACRO TRICKERY
		175
		176	=over 4
		177
		178	=item ECB_CONCAT (a, b)
		179
		180	Expands any macros in C<a> and C<b>, then concatenates the result to form
		181	a single token. This is mainly useful to form identifiers from components,
		182	e.g.:
		183
		184	#define S1 str
		185	#define S2 cpy
		186
		187	ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src);
		188
		189	=item ECB_STRINGIFY (arg)
		190
		191	Expands any macros in C<arg> and returns the stringified version of
		192	it. This is mainly useful to get the contents of a macro in string form,
		193	e.g.:
		194
		195	#define SQL_LIMIT 100
		196	sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT));
		197
		198	=item ECB_STRINGIFY_EXPR (expr)
		199
		200	Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it
		201	is a valid expression. This is useful to catch typos or cases where the
		202	macro isn't available:
		203
		204	#include <errno.h>
		205
		206	ECB_STRINGIFY (EDOM); // "33" (on my system at least)
		207	ECB_STRINGIFY_EXPR (EDOM); // "33"
		208
		209	// now imagine we had a typo:
		210
		211	ECB_STRINGIFY (EDAM); // "EDAM"
		212	ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined
		213
		214	=back
		215
70	=head2 GCC ATTRIBUTES	216	=head2 ATTRIBUTES
71		217
72	A major part of libecb deals with GCC attributes. These are additional	218	A major part of libecb deals with additional attributes that can be
73	attributes that you can assign to functions, variables and sometimes even	219	assigned to functions, variables and sometimes even types - much like
74	types - much like C<const> or C<volatile> in C.	220	C<const> or C<volatile> in C. They are implemented using either GCC
75		221	attributes or other compiler/language specific features. Attributes
76	While GCC allows declarations to show up in many surprising places,
77	but not in many expected places, the safest way is to put attribute
78	declarations before the whole declaration:	222	declarations must be put before the whole declaration:
79		223
80	ecb_const int mysqrt (int a);	224	ecb_const int mysqrt (int a);
81	ecb_unused int i;	225	ecb_unused int i;
82		226
83	For variables, it is often nicer to put the attribute after the name, and
84	avoid multiple declarations using commas:
85
86	int i ecb_unused;
87
88	=over 4	227	=over 4
89
90	=item ecb_attribute ((attrs...))
91
92	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
93	nothing on other compilers, so the effect is that only GCC sees these.
94
95	Example: use the C<deprecated> attribute on a function.
96
97	ecb_attribute((__deprecated__)) void
98	do_not_use_me_anymore (void);
99		228
100	=item ecb_unused	229	=item ecb_unused
101		230
102	Marks a function or a variable as "unused", which simply suppresses a	231	Marks a function or a variable as "unused", which simply suppresses a
103	warning by GCC when it detects it as unused. This is useful when you e.g.	232	warning by GCC when it detects it as unused. This is useful when you e.g.
104	declare a variable but do not always use it:	233	declare a variable but do not always use it:
105		234
106	{	235	{
107	int var ecb_unused;	236	ecb_unused int var;
108		237
109	#ifdef SOMECONDITION	238	#ifdef SOMECONDITION
110	var = ...;	239	var = ...;
111	return var;	240	return var;
112	#else	241	#else
113	return 0;	242	return 0;
114	#endif	243	#endif
115	}	244	}
116		245
		246	=item ecb_deprecated
		247
		248	Similar to C<ecb_unused>, but marks a function, variable or type as
		249	deprecated. This makes some compilers warn when the type is used.
		250
		251	=item ecb_deprecated_message (message)
		252
		253	Same as C<ecb_deprecated>, but if possible, the specified diagnostic is
		254	used instead of a generic depreciation message when the object is being
		255	used.
		256
117	=item ecb_inline	257	=item ecb_inline
118		258
119	This is not actually an attribute, but you use it like one. It expands	259	Expands either to (a compiler-specific equivalent of) C<static inline> or
120	either to C<static inline> or to just C<static>, if inline isn't	260	to just C<static>, if inline isn't supported. It should be used to declare
121	supported. It should be used to declare functions that should be inlined,	261	functions that should be inlined, for code size or speed reasons.
122	for code size or speed reasons.
123		262
124	Example: inline this function, it surely will reduce codesize.	263	Example: inline this function, it surely will reduce codesize.
125		264
126	ecb_inline int	265	ecb_inline int
127	negmul (int a, int b)	266	negmul (int a, int b)
…		…
129	return - (a * b);	268	return - (a * b);
130	}	269	}
131		270
132	=item ecb_noinline	271	=item ecb_noinline
133		272
134	Prevent a function from being inlined - it might be optimised away, but	273	Prevents a function from being inlined - it might be optimised away, but
135	not inlined into other functions. This is useful if you know your function	274	not inlined into other functions. This is useful if you know your function
136	is rarely called and large enough for inlining not to be helpful.	275	is rarely called and large enough for inlining not to be helpful.
137		276
138	=item ecb_noreturn	277	=item ecb_noreturn
139		278
…		…
149	}	288	}
150		289
151	In this case, the compiler would probably be smart enough to deduce it on	290	In this case, the compiler would probably be smart enough to deduce it on
152	its own, so this is mainly useful for declarations.	291	its own, so this is mainly useful for declarations.
153		292
		293	=item ecb_restrict
		294
		295	Expands to the C<restrict> keyword or equivalent on compilers that support
		296	them, and to nothing on others. Must be specified on a pointer type or
		297	an array index to indicate that the memory doesn't alias with any other
		298	restricted pointer in the same scope.
		299
		300	Example: multiply a vector, and allow the compiler to parallelise the
		301	loop, because it knows it doesn't overwrite input values.
		302
		303	void
		304	multiply (ecb_restrict float *src,
		305	ecb_restrict float *dst,
		306	int len, float factor)
		307	{
		308	int i;
		309
		310	for (i = 0; i < len; ++i)
		311	dst [i] = src [i] * factor;
		312	}
		313
154	=item ecb_const	314	=item ecb_const
155		315
156	Declares that the function only depends on the values of its arguments,	316	Declares that the function only depends on the values of its arguments,
157	much like a mathematical function. It specifically does not read or write	317	much like a mathematical function. It specifically does not read or write
158	any memory any arguments might point to, global variables, or call any	318	any memory any arguments might point to, global variables, or call any
…		…
218	functions only called in exceptional or rare cases.	378	functions only called in exceptional or rare cases.
219		379
220	=item ecb_artificial	380	=item ecb_artificial
221		381
222	Declares the function as "artificial", in this case meaning that this	382	Declares the function as "artificial", in this case meaning that this
223	function is not really mean to be a function, but more like an accessor	383	function is not really meant to be a function, but more like an accessor
224	- many methods in C++ classes are mere accessor functions, and having a	384	- many methods in C++ classes are mere accessor functions, and having a
225	crash reported in such a method, or single-stepping through them, is not	385	crash reported in such a method, or single-stepping through them, is not
226	usually so helpful, especially when it's inlined to just a few instructions.	386	usually so helpful, especially when it's inlined to just a few instructions.
227		387
228	Marking them as artificial will instruct the debugger about just this,	388	Marking them as artificial will instruct the debugger about just this,
…		…
248		408
249	=head2 OPTIMISATION HINTS	409	=head2 OPTIMISATION HINTS
250		410
251	=over 4	411	=over 4
252		412
		413	=item ECB_OPTIMIZE_SIZE
		414
		415	Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol
		416	can also be defined before including F<ecb.h>, in which case it will be
		417	unchanged.
		418
253	=item bool ecb_is_constant(expr)	419	=item bool ecb_is_constant (expr)
254		420
255	Returns true iff the expression can be deduced to be a compile-time	421	Returns true iff the expression can be deduced to be a compile-time
256	constant, and false otherwise.	422	constant, and false otherwise.
257		423
258	For example, when you have a C<rndm16> function that returns a 16 bit	424	For example, when you have a C<rndm16> function that returns a 16 bit
…		…
276	return is_constant (n) && !(n & (n - 1))	442	return is_constant (n) && !(n & (n - 1))
277	? rndm16 () & (num - 1)	443	? rndm16 () & (num - 1)
278	: (n * (uint32_t)rndm16 ()) >> 16;	444	: (n * (uint32_t)rndm16 ()) >> 16;
279	}	445	}
280		446
281	=item bool ecb_expect (expr, value)	447	=item ecb_expect (expr, value)
282		448
283	Evaluates C<expr> and returns it. In addition, it tells the compiler that	449	Evaluates C<expr> and returns it. In addition, it tells the compiler that
284	the C<expr> evaluates to C<value> a lot, which can be used for static	450	the C<expr> evaluates to C<value> a lot, which can be used for static
285	branch optimisations.	451	branch optimisations.
286		452
…		…
333	{	499	{
334	if (ecb_expect_false (current + size > end))	500	if (ecb_expect_false (current + size > end))
335	real_reserve_method (size); /* presumably noinline */	501	real_reserve_method (size); /* presumably noinline */
336	}	502	}
337		503
338	=item bool ecb_assume (cond)	504	=item ecb_assume (cond)
339		505
340	Try to tell the compiler that some condition is true, even if it's not	506	Tries to tell the compiler that some condition is true, even if it's not
341	obvious.	507	obvious. This is not a function, but a statement: it cannot be used in
		508	another expression.
342		509
343	This can be used to teach the compiler about invariants or other	510	This can be used to teach the compiler about invariants or other
344	conditions that might improve code generation, but which are impossible to	511	conditions that might improve code generation, but which are impossible to
345	deduce form the code itself.	512	deduce form the code itself.
346		513
…		…
363		530
364	Then the compiler I<might> be able to optimise out the second call	531	Then the compiler I<might> be able to optimise out the second call
365	completely, as it knows that C<< current + 1 > end >> is false and the	532	completely, as it knows that C<< current + 1 > end >> is false and the
366	call will never be executed.	533	call will never be executed.
367		534
368	=item bool ecb_unreachable ()	535	=item ecb_unreachable ()
369		536
370	This function does nothing itself, except tell the compiler that it will	537	This function does nothing itself, except tell the compiler that it will
371	never be executed. Apart from suppressing a warning in some cases, this	538	never be executed. Apart from suppressing a warning in some cases, this
372	function can be used to implement C<ecb_assume> or similar functions.	539	function can be used to implement C<ecb_assume> or similar functionality.
373		540
374	=item bool ecb_prefetch (addr, rw, locality)	541	=item ecb_prefetch (addr, rw, locality)
375		542
376	Tells the compiler to try to prefetch memory at the given C<addr>ess	543	Tells the compiler to try to prefetch memory at the given C<addr>ess
377	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of	544	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of
378	C<0> means that there will only be one access later, C<3> means that	545	C<0> means that there will only be one access later, C<3> means that
379	the data will likely be accessed very often, and values in between mean	546	the data will likely be accessed very often, and values in between mean
380	something... in between. The memory pointed to by the address does not	547	something... in between. The memory pointed to by the address does not
381	need to be accessible (it could be a null pointer for example), but C<rw>	548	need to be accessible (it could be a null pointer for example), but C<rw>
382	and C<locality> must be compile-time constants.	549	and C<locality> must be compile-time constants.
383		550
		551	This is a statement, not a function: you cannot use it as part of an
		552	expression.
		553
384	An obvious way to use this is to prefetch some data far away, in a big	554	An obvious way to use this is to prefetch some data far away, in a big
385	array you loop over. This prefetches memory some 128 array elements later,	555	array you loop over. This prefetches memory some 128 array elements later,
386	in the hope that it will be ready when the CPU arrives at that location.	556	in the hope that it will be ready when the CPU arrives at that location.
387		557
388	int sum = 0;	558	int sum = 0;
…		…
440		610
441	=item bool ecb_is_pot32 (uint32_t x)	611	=item bool ecb_is_pot32 (uint32_t x)
442		612
443	=item bool ecb_is_pot64 (uint32_t x)	613	=item bool ecb_is_pot64 (uint32_t x)
444		614
445	Return true iff C<x> is a power of two or C<x == 0>.	615	Returns true iff C<x> is a power of two or C<x == 0>.
446		616
447	For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>.	617	For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>.
448		618
449	=item int ecb_ld32 (uint32_t x)	619	=item int ecb_ld32 (uint32_t x)
450		620
451	=item int ecb_ld64 (uint64_t x)	621	=item int ecb_ld64 (uint64_t x)
452		622
…		…
498		668
499	These functions return the value of the 16-bit (32-bit, 64-bit) value	669	These functions return the value of the 16-bit (32-bit, 64-bit) value
500	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in	670	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in
501	C<ecb_bswap32>).	671	C<ecb_bswap32>).
502		672
		673	=item T ecb_bswap (T x) [C++]
		674
		675	For C++, an additional generic bswap function is provided. It supports
		676	C<uint8_t>, C<uint16_t>, C<uint32_t> and C<uint64_t>.
		677
503	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)	678	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
504		679
505	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)	680	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
506		681
507	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	682	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
…		…
521	(C<ecb_rotl>).	696	(C<ecb_rotl>).
522		697
523	Current GCC versions understand these functions and usually compile them	698	Current GCC versions understand these functions and usually compile them
524	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on	699	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
525	x86).	700	x86).
		701
		702	=back
		703
		704	=head2 HOST ENDIANNESS CONVERSION
		705
		706	=over 4
		707
		708	=item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v)
		709
		710	=item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v)
		711
		712	=item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v)
		713
		714	=item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v)
		715
		716	=item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v)
		717
		718	=item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v)
		719
		720	Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order.
		721
		722	The naming convention is C<ecb_>(C<be>\|C<le>)C<_u>C<16\|32\|64>C<_to_host>,
		723	where be and le stand for big endian and little endian, respectively.
		724
		725	=item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v)
		726
		727	=item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v)
		728
		729	=item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v)
		730
		731	=item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v)
		732
		733	=item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v)
		734
		735	=item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v)
		736
		737	Like above, but converts I<from> host byte order to the specified
		738	endianness.
		739
		740	=back
		741
		742	In C++ the following additional functions are supported:
		743
		744	=over 4
		745
		746	=item T ecb_be_to_host (T v)
		747
		748	=item T ecb_le_to_host (T v)
		749
		750	=item T ecb_host_to_be (T v)
		751
		752	=item T ecb_host_to_le (T v)
		753
		754	These work like their C counterparts, above, but use templates for the
		755	type, which make them useful in generic code.
		756
		757	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>
		758	(so unlike their C counterparts, there is a version for C<uint8_t>, which
		759	again can be useful in generic code).
		760
		761	=head2 UNALIGNED LOAD/STORE
		762
		763	These function load or store unaligned multi-byte values.
		764
		765	=over 4
		766
		767	=item uint_fast16_t ecb_peek_u16_u (const void *ptr)
		768
		769	=item uint_fast32_t ecb_peek_u32_u (const void *ptr)
		770
		771	=item uint_fast64_t ecb_peek_u64_u (const void *ptr)
		772
		773	These functions load an unaligned, unsigned 16, 32 or 64 bit value from
		774	memory.
		775
		776	=item uint_fast16_t ecb_peek_be_u16_u (const void *ptr)
		777
		778	=item uint_fast32_t ecb_peek_be_u32_u (const void *ptr)
		779
		780	=item uint_fast64_t ecb_peek_be_u64_u (const void *ptr)
		781
		782	=item uint_fast16_t ecb_peek_le_u16_u (const void *ptr)
		783
		784	=item uint_fast32_t ecb_peek_le_u32_u (const void *ptr)
		785
		786	=item uint_fast64_t ecb_peek_le_u64_u (const void *ptr)
		787
		788	Like above, but additionally convert from big endian (C<be>) or little
		789	endian (C<le>) byte order to host byte order while doing so.
		790
		791	=item ecb_poke_u16_u (void *ptr, uint16_t v)
		792
		793	=item ecb_poke_u32_u (void *ptr, uint32_t v)
		794
		795	=item ecb_poke_u64_u (void *ptr, uint64_t v)
		796
		797	These functions store an unaligned, unsigned 16, 32 or 64 bit value to
		798	memory.
		799
		800	=item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v)
		801
		802	=item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v)
		803
		804	=item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v)
		805
		806	=item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v)
		807
		808	=item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v)
		809
		810	=item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v)
		811
		812	Like above, but additionally convert from host byte order to big endian
		813	(C<be>) or little endian (C<le>) byte order while doing so.
		814
		815	=back
		816
		817	In C++ the following additional functions are supported:
		818
		819	=over 4
		820
		821	=item T ecb_peek (const void *ptr)
		822
		823	=item T ecb_peek_be (const void *ptr)
		824
		825	=item T ecb_peek_le (const void *ptr)
		826
		827	=item T ecb_peek_u (const void *ptr)
		828
		829	=item T ecb_peek_be_u (const void *ptr)
		830
		831	=item T ecb_peek_le_u (const void *ptr)
		832
		833	Similarly to their C counterparts, these functions load an unsigned 8, 16,
		834	32 or 64 bit value from memory, with optional conversion from big/little
		835	endian.
		836
		837	Since the type cannot be deduced, it has top be specified explicitly, e.g.
		838
		839	uint_fast16_t v = ecb_peek<uint16_t> (ptr);
		840
		841	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		842
		843	Unlike their C counterparts, these functions support 8 bit quantities
		844	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		845	all of which hopefully makes them more useful in generic code.
		846
		847	=item ecb_poke (void *ptr, T v)
		848
		849	=item ecb_poke_be (void *ptr, T v)
		850
		851	=item ecb_poke_le (void *ptr, T v)
		852
		853	=item ecb_poke_u (void *ptr, T v)
		854
		855	=item ecb_poke_be_u (void *ptr, T v)
		856
		857	=item ecb_poke_le_u (void *ptr, T v)
		858
		859	Again, similarly to their C counterparts, these functions store an
		860	unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to
		861	big/little endian.
		862
		863	C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>.
		864
		865	Unlike their C counterparts, these functions support 8 bit quantities
		866	(C<uint8_t>) and also have an aligned version (without the C<_u> prefix),
		867	all of which hopefully makes them more useful in generic code.
		868
		869	=back
		870
		871	=head2 FLOATING POINT FIDDLING
		872
		873	=over 4
		874
		875	=item ECB_INFINITY [-UECB_NO_LIBM]
		876
		877	Evaluates to positive infinity if supported by the platform, otherwise to
		878	a truly huge number.
		879
		880	=item ECB_NAN [-UECB_NO_LIBM]
		881
		882	Evaluates to a quiet NAN if supported by the platform, otherwise to
		883	C<ECB_INFINITY>.
		884
		885	=item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM]
		886
		887	Same as C<ldexpf>, but always available.
		888
		889	=item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM]
		890
		891	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
		892
		893	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
		894
		895	These functions each take an argument in the native C<float> or C<double>
		896	type and return the IEEE 754 bit representation of it (binary16/half,
		897	binary32/single or binary64/double precision).
		898
		899	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
		900	will be the most significant bit, followed by exponent and mantissa.
		901
		902	This function should work even when the native floating point format isn't
		903	IEEE compliant, of course at a speed and code size penalty, and of course
		904	also within reasonable limits (it tries to convert NaNs, infinities and
		905	denormals, but will likely convert negative zero to positive zero).
		906
		907	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		908	be able to optimise away this function completely.
		909
		910	These functions can be helpful when serialising floats to the network - you
		911	can serialise the return value like a normal uint16_t/uint32_t/uint64_t.
		912
		913	Another use for these functions is to manipulate floating point values
		914	directly.
		915
		916	Silly example: toggle the sign bit of a float.
		917
		918	/* On gcc-4.7 on amd64, */
		919	/* this results in a single add instruction to toggle the bit, and 4 extra */
		920	/* instructions to move the float value to an integer register and back. */
		921
		922	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
		923
		924	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		925
		926	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
		927
		928	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
		929
		930	The reverse operation of the previous function - takes the bit
		931	representation of an IEEE binary16, binary32 or binary64 number (half,
		932	single or double precision) and converts it to the native C<float> or
		933	C<double> format.
		934
		935	This function should work even when the native floating point format isn't
		936	IEEE compliant, of course at a speed and code size penalty, and of course
		937	also within reasonable limits (it tries to convert normals and denormals,
		938	and might be lucky for infinities, and with extraordinary luck, also for
		939	negative zero).
		940
		941	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		942	be able to optimise away this function completely.
		943
		944	=item uint16_t ecb_binary32_to_binary16 (uint32_t x)
		945
		946	=item uint32_t ecb_binary16_to_binary32 (uint16_t x)
		947
		948	Convert a IEEE binary32/single precision to binary16/half format, and vice
		949	versa, handling all details (round-to-nearest-even, subnormals, infinity
		950	and NaNs) correctly.
		951
		952	These are functions are available under C<-DECB_NO_LIBM>, since
		953	they do not rely on the platform floating point format. The
		954	C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are
		955	usually what you want.
526		956
527	=back	957	=back
528		958
529	=head2 ARITHMETIC	959	=head2 ARITHMETIC
530		960
…		…
581	for (i = 0; i < ecb_array_length (primes); i++)	1011	for (i = 0; i < ecb_array_length (primes); i++)
582	sum += primes [i];	1012	sum += primes [i];
583		1013
584	=back	1014	=back
585		1015
		1016	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF
586		1017
		1018	These symbols need to be defined before including F<ecb.h> the first time.
		1019
		1020	=over 4
		1021
		1022	=item ECB_NO_THREADS
		1023
		1024	If F<ecb.h> is never used from multiple threads, then this symbol can
		1025	be defined, in which case memory fences (and similar constructs) are
		1026	completely removed, leading to more efficient code and fewer dependencies.
		1027
		1028	Setting this symbol to a true value implies C<ECB_NO_SMP>.
		1029
		1030	=item ECB_NO_SMP
		1031
		1032	The weaker version of C<ECB_NO_THREADS> - if F<ecb.h> is used from
		1033	multiple threads, but never concurrently (e.g. if the system the program
		1034	runs on has only a single CPU with a single core, no hyperthreading and so
		1035	on), then this symbol can be defined, leading to more efficient code and
		1036	fewer dependencies.
		1037
		1038	=item ECB_NO_LIBM
		1039
		1040	When defined to C<1>, do not export any functions that might introduce
		1041	dependencies on the math library (usually called F<-lm>) - these are
		1042	marked with [-UECB_NO_LIBM].
		1043
		1044	=back
		1045
		1046	=head1 UNDOCUMENTED FUNCTIONALITY
		1047
		1048	F<ecb.h> is full of undocumented functionality as well, some of which is
		1049	intended to be internal-use only, some of which we forgot to document, and
		1050	some of which we hide because we are not sure we will keep the interface
		1051	stable.
		1052
		1053	While you are welcome to rummage around and use whatever you find useful
		1054	(we can't stop you), keep in mind that we will change undocumented
		1055	functionality in incompatible ways without thinking twice, while we are
		1056	considerably more conservative with documented things.
		1057
		1058	=head1 AUTHORS
		1059
		1060	C<libecb> is designed and maintained by:
		1061
		1062	Emanuele Giaquinta <e.giaquinta@glauco.it>
		1063	Marc Alexander Lehmann <schmorp@schmorp.de>
		1064
		1065

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Comparing libecb/ecb.pod (file contents): Revision 1.41 by root, Mon May 28 08:40:25 2012 UTC vs. Revision 1.76 by root, Mon Jan 20 13:13:56 2020 UTC

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Comparing libecb/ecb.pod (file contents):
Revision 1.41 by root, Mon May 28 08:40:25 2012 UTC vs.
Revision 1.76 by root, Mon Jan 20 13:13:56 2020 UTC