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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.53 by root, Wed Dec 5 16:31:27 2012 UTC vs.
Revision 1.64 by root, Wed Feb 18 20:48:59 2015 UTC

…		…
68	platform (currently C<4> or C<8>) and can be used in preprocessor	68	platform (currently C<4> or C<8>) and can be used in preprocessor
69	expressions.	69	expressions.
70		70
71	For C<ptrdiff_t> and C<size_t> use C<stddef.h>.	71	For C<ptrdiff_t> and C<size_t> use C<stddef.h>.
72		72
73	=head2 LANGUAGE/COMPILER VERSIONS	73	=head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS
74		74
75	All the following symbols expand to an expression that can be tested in	75	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	76	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).	77	ensure it's either C<0> or C<1> if you need that).
78		78
79	=over 4	79	=over 4
80		80
81	=item ECB_C	81	=item ECB_C
82		82
83	True if the implementation defines the C<__STDC__> macro to a true value,	83	True if the implementation defines the C<__STDC__> macro to a true value,
84	which is typically true for both C and C++ compilers.	84	while not claiming to be C++.
85		85
86	=item ECB_C99	86	=item ECB_C99
87		87
88	True if the implementation claims to be compliant to C99 (ISO/IEC	88	True if the implementation claims to be compliant to C99 (ISO/IEC
89	9899:1999) or any later version.	89	9899:1999) or any later version, while not claiming to be C++.
90		90
91	Note that later versions (ECB_C11) remove core features again (for	91	Note that later versions (ECB_C11) remove core features again (for
92	example, variable length arrays).	92	example, variable length arrays).
93		93
94	=item ECB_C11	94	=item ECB_C11
95		95
96	True if the implementation claims to be compliant to C11 (ISO/IEC	96	True if the implementation claims to be compliant to C11 (ISO/IEC
97	9899:2011) or any later version.	97	9899:2011) or any later version, while not claiming to be C++.
98		98
99	=item ECB_CPP	99	=item ECB_CPP
100		100
101	True if the implementation defines the C<__cplusplus__> macro to a true	101	True if the implementation defines the C<__cplusplus__> macro to a true
102	value, which is typically true for C++ compilers.	102	value, which is typically true for C++ compilers.
…		…
104	=item ECB_CPP11	104	=item ECB_CPP11
105		105
106	True if the implementation claims to be compliant to ISO/IEC 14882:2011	106	True if the implementation claims to be compliant to ISO/IEC 14882:2011
107	(C++11) or any later version.	107	(C++11) or any later version.
108		108
109	=item ECB_GCC_VERSION(major,minor)	109	=item ECB_GCC_VERSION (major, minor)
110		110
111	Expands to a true value (suitable for testing in by the preprocessor)	111	Expands to a true value (suitable for testing in by the preprocessor)
112	if the compiler used is GNU C and the version is the given version, or	112	if the compiler used is GNU C and the version is the given version, or
113	higher.	113	higher.
114		114
…		…
150		150
151	This is true for basically all modern platforms, although F<ecb.h> might	151	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	152	not be able to deduce this correctly everywhere and might err on the safe
153	side.	153	side.
154		154
		155	=item ECB_AMD64, ECB_AMD64_X32
		156
		157	These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32
		158	ABI, respectively, and undefined elsewhere.
		159
		160	The designers of the new X32 ABI for some inexplicable reason decided to
		161	make it look exactly like amd64, even though it's completely incompatible
		162	to that ABI, breaking about every piece of software that assumed that
		163	C<__x86_64> stands for, well, the x86-64 ABI, making these macros
		164	necessary.
		165
155	=back	166	=back
156		167
		168	=head2 MACRO TRICKERY
		169
		170	=over 4
		171
		172	=item ECB_CONCAT (a, b)
		173
		174	Expands any macros in C<a> and C<b>, then concatenates the result to form
		175	a single token. This is mainly useful to form identifiers from components,
		176	e.g.:
		177
		178	#define S1 str
		179	#define S2 cpy
		180
		181	ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src);
		182
		183	=item ECB_STRINGIFY (arg)
		184
		185	Expands any macros in C<arg> and returns the stringified version of
		186	it. This is mainly useful to get the contents of a macro in string form,
		187	e.g.:
		188
		189	#define SQL_LIMIT 100
		190	sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT));
		191
		192	=item ECB_STRINGIFY_EXPR (expr)
		193
		194	Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it
		195	is a valid expression. This is useful to catch typos or cases where the
		196	macro isn't available:
		197
		198	#include <errno.h>
		199
		200	ECB_STRINGIFY (EDOM); // "33" (on my system at least)
		201	ECB_STRINGIFY_EXPR (EDOM); // "33"
		202
		203	// now imagine we had a typo:
		204
		205	ECB_STRINGIFY (EDAM); // "EDAM"
		206	ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined
		207
		208	=back
		209
157	=head2 GCC ATTRIBUTES	210	=head2 ATTRIBUTES
158		211
159	A major part of libecb deals with GCC attributes. These are additional	212	A major part of libecb deals with additional attributes that can be
160	attributes that you can assign to functions, variables and sometimes even	213	assigned to functions, variables and sometimes even types - much like
161	types - much like C<const> or C<volatile> in C.	214	C<const> or C<volatile> in C. They are implemented using either GCC
162		215	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:	216	declarations must be put before the whole declaration:
166		217
167	ecb_const int mysqrt (int a);	218	ecb_const int mysqrt (int a);
168	ecb_unused int i;	219	ecb_unused int i;
169		220
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	221	=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		222
187	=item ecb_unused	223	=item ecb_unused
188		224
189	Marks a function or a variable as "unused", which simply suppresses a	225	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.	226	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:	227	declare a variable but do not always use it:
192		228
193	{	229	{
194	int var ecb_unused;	230	ecb_unused int var;
195		231
196	#ifdef SOMECONDITION	232	#ifdef SOMECONDITION
197	var = ...;	233	var = ...;
198	return var;	234	return var;
199	#else	235	#else
200	return 0;	236	return 0;
201	#endif	237	#endif
202	}	238	}
203		239
		240	=item ecb_deprecated
		241
		242	Similar to C<ecb_unused>, but marks a function, variable or type as
		243	deprecated. This makes some compilers warn when the type is used.
		244
		245	=item ecb_deprecated_message (message)
		246
		247	Same as C<ecb_deprecated>, but if possible, supply a diagnostic that is
		248	used instead of a generic depreciation message when the object is being
		249	used.
		250
204	=item ecb_inline	251	=item ecb_inline
205		252
206	This is not actually an attribute, but you use it like one. It expands
207	either to C<static inline> or to just C<static>, if inline isn't	253	Expands either to C<static inline> or to just C<static>, if inline
208	supported. It should be used to declare functions that should be inlined,	254	isn't supported. It should be used to declare functions that should be
209	for code size or speed reasons.	255	inlined, for code size or speed reasons.
210		256
211	Example: inline this function, it surely will reduce codesize.	257	Example: inline this function, it surely will reduce codesize.
212		258
213	ecb_inline int	259	ecb_inline int
214	negmul (int a, int b)	260	negmul (int a, int b)
…		…
247		293
248	Example: multiply a vector, and allow the compiler to parallelise the	294	Example: multiply a vector, and allow the compiler to parallelise the
249	loop, because it knows it doesn't overwrite input values.	295	loop, because it knows it doesn't overwrite input values.
250		296
251	void	297	void
252	multiply (float *ecb_restrict src,	298	multiply (ecb_restrict float *src,
253	float *ecb_restrict dst,	299	ecb_restrict float *dst,
254	int len, float factor)	300	int len, float factor)
255	{	301	{
256	int i;	302	int i;
257		303
258	for (i = 0; i < len; ++i)	304	for (i = 0; i < len; ++i)
…		…
356		402
357	=head2 OPTIMISATION HINTS	403	=head2 OPTIMISATION HINTS
358		404
359	=over 4	405	=over 4
360		406
361	=item bool ecb_is_constant(expr)	407	=item bool ecb_is_constant (expr)
362		408
363	Returns true iff the expression can be deduced to be a compile-time	409	Returns true iff the expression can be deduced to be a compile-time
364	constant, and false otherwise.	410	constant, and false otherwise.
365		411
366	For example, when you have a C<rndm16> function that returns a 16 bit	412	For example, when you have a C<rndm16> function that returns a 16 bit
…		…
384	return is_constant (n) && !(n & (n - 1))	430	return is_constant (n) && !(n & (n - 1))
385	? rndm16 () & (num - 1)	431	? rndm16 () & (num - 1)
386	: (n * (uint32_t)rndm16 ()) >> 16;	432	: (n * (uint32_t)rndm16 ()) >> 16;
387	}	433	}
388		434
389	=item bool ecb_expect (expr, value)	435	=item ecb_expect (expr, value)
390		436
391	Evaluates C<expr> and returns it. In addition, it tells the compiler that	437	Evaluates C<expr> and returns it. In addition, it tells the compiler that
392	the C<expr> evaluates to C<value> a lot, which can be used for static	438	the C<expr> evaluates to C<value> a lot, which can be used for static
393	branch optimisations.	439	branch optimisations.
394		440
…		…
441	{	487	{
442	if (ecb_expect_false (current + size > end))	488	if (ecb_expect_false (current + size > end))
443	real_reserve_method (size); /* presumably noinline */	489	real_reserve_method (size); /* presumably noinline */
444	}	490	}
445		491
446	=item bool ecb_assume (cond)	492	=item ecb_assume (cond)
447		493
448	Try to tell the compiler that some condition is true, even if it's not	494	Try to tell the compiler that some condition is true, even if it's not
449	obvious.	495	obvious.
450		496
451	This can be used to teach the compiler about invariants or other	497	This can be used to teach the compiler about invariants or other
…		…
471		517
472	Then the compiler I<might> be able to optimise out the second call	518	Then the compiler I<might> be able to optimise out the second call
473	completely, as it knows that C<< current + 1 > end >> is false and the	519	completely, as it knows that C<< current + 1 > end >> is false and the
474	call will never be executed.	520	call will never be executed.
475		521
476	=item bool ecb_unreachable ()	522	=item ecb_unreachable ()
477		523
478	This function does nothing itself, except tell the compiler that it will	524	This function does nothing itself, except tell the compiler that it will
479	never be executed. Apart from suppressing a warning in some cases, this	525	never be executed. Apart from suppressing a warning in some cases, this
480	function can be used to implement C<ecb_assume> or similar functions.	526	function can be used to implement C<ecb_assume> or similar functions.
481		527
482	=item bool ecb_prefetch (addr, rw, locality)	528	=item ecb_prefetch (addr, rw, locality)
483		529
484	Tells the compiler to try to prefetch memory at the given C<addr>ess	530	Tells the compiler to try to prefetch memory at the given C<addr>ess
485	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of	531	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of
486	C<0> means that there will only be one access later, C<3> means that	532	C<0> means that there will only be one access later, C<3> means that
487	the data will likely be accessed very often, and values in between mean	533	the data will likely be accessed very often, and values in between mean
…		…
636		682
637	=head2 FLOATING POINT FIDDLING	683	=head2 FLOATING POINT FIDDLING
638		684
639	=over 4	685	=over 4
640		686
		687	=item ECB_INFINITY
		688
		689	Evaluates to positive infinity if supported by the platform, otherwise to
		690	a truly huge number.
		691
		692	=item ECB_NAN
		693
		694	Evaluates to a quiet NAN if supported by the platform, otherwise to
		695	C<ECB_INFINITY>.
		696
		697	=item float ecb_ldexpf (float x, int exp)
		698
		699	Same as C<ldexpf>, but always available.
		700
641	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]	701	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
642		702
643	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]	703	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
644		704
645	These functions each take an argument in the native C<float> or C<double>	705	These functions each take an argument in the native C<float> or C<double>
…		…
668	/* this results in a single add instruction to toggle the bit, and 4 extra */	728	/* this results in a single add instruction to toggle the bit, and 4 extra */
669	/* instructions to move the float value to an integer register and back. */	729	/* instructions to move the float value to an integer register and back. */
670		730
671	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)	731	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
672		732
		733	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		734
673	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]	735	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
674		736
675	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]	737	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]
676		738
677	The reverse operation of the previos function - takes the bit representation	739	The reverse operation of the previous function - takes the bit
678	of an IEEE binary32 or binary64 number and converts it to the native C<float>	740	representation of an IEEE binary16, binary32 or binary64 number and
679	or C<double> format.	741	converts it to the native C<float> or C<double> format.
680		742
681	This function should work even when the native floating point format isn't	743	This function should work even when the native floating point format isn't
682	IEEE compliant, of course at a speed and code size penalty, and of course	744	IEEE compliant, of course at a speed and code size penalty, and of course
683	also within reasonable limits (it tries to convert normals and denormals,	745	also within reasonable limits (it tries to convert normals and denormals,
684	and might be lucky for infinities, and with extraordinary luck, also for	746	and might be lucky for infinities, and with extraordinary luck, also for

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Comparing cvsroot/libecb/ecb.pod (file contents): Revision 1.53 by root, Wed Dec 5 16:31:27 2012 UTC vs. Revision 1.64 by root, Wed Feb 18 20:48:59 2015 UTC

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Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.53 by root, Wed Dec 5 16:31:27 2012 UTC vs.
Revision 1.64 by root, Wed Feb 18 20:48:59 2015 UTC