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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.56 by root, Mon Jun 9 17:31:57 2014 UTC vs.
Revision 1.70 by root, Tue Sep 1 16:14:42 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
…		…
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
…		…
163	C<__x86_64> stands for, well, the x86-64 ABI, making these macros	163	C<__x86_64> stands for, well, the x86-64 ABI, making these macros
164	necessary.	164	necessary.
165		165
166	=back	166	=back
167		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
168	=head2 GCC ATTRIBUTES	210	=head2 ATTRIBUTES
169		211
170	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
171	attributes that you can assign to functions, variables and sometimes even	213	assigned to functions, variables and sometimes even types - much like
172	types - much like C<const> or C<volatile> in C.	214	C<const> or C<volatile> in C. They are implemented using either GCC
173		215	attributes or other compiler/language specific features. Attributes
174	While GCC allows declarations to show up in many surprising places,
175	but not in many expected places, the safest way is to put attribute
176	declarations before the whole declaration:	216	declarations must be put before the whole declaration:
177		217
178	ecb_const int mysqrt (int a);	218	ecb_const int mysqrt (int a);
179	ecb_unused int i;	219	ecb_unused int i;
180		220
181	For variables, it is often nicer to put the attribute after the name, and
182	avoid multiple declarations using commas:
183
184	int i ecb_unused;
185
186	=over 4	221	=over 4
187
188	=item ecb_attribute ((attrs...))
189
190	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
191	nothing on other compilers, so the effect is that only GCC sees these.
192
193	Example: use the C<deprecated> attribute on a function.
194
195	ecb_attribute((__deprecated__)) void
196	do_not_use_me_anymore (void);
197		222
198	=item ecb_unused	223	=item ecb_unused
199		224
200	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
201	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.
202	declare a variable but do not always use it:	227	declare a variable but do not always use it:
203		228
204	{	229	{
205	int var ecb_unused;	230	ecb_unused int var;
206		231
207	#ifdef SOMECONDITION	232	#ifdef SOMECONDITION
208	var = ...;	233	var = ...;
209	return var;	234	return var;
210	#else	235	#else
…		…
215	=item ecb_deprecated	240	=item ecb_deprecated
216		241
217	Similar to C<ecb_unused>, but marks a function, variable or type as	242	Similar to C<ecb_unused>, but marks a function, variable or type as
218	deprecated. This makes some compilers warn when the type is used.	243	deprecated. This makes some compilers warn when the type is used.
219		244
		245	=item ecb_deprecated_message (message)
		246
		247	Same as C<ecb_deprecated>, but if possible, the specified diagnostic is
		248	used instead of a generic depreciation message when the object is being
		249	used.
		250
220	=item ecb_inline	251	=item ecb_inline
221		252
222	This is not actually an attribute, but you use it like one. It expands
223	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
224	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
225	for code size or speed reasons.	255	inlined, for code size or speed reasons.
226		256
227	Example: inline this function, it surely will reduce codesize.	257	Example: inline this function, it surely will reduce codesize.
228		258
229	ecb_inline int	259	ecb_inline int
230	negmul (int a, int b)	260	negmul (int a, int b)
…		…
232	return - (a * b);	262	return - (a * b);
233	}	263	}
234		264
235	=item ecb_noinline	265	=item ecb_noinline
236		266
237	Prevent a function from being inlined - it might be optimised away, but	267	Prevents a function from being inlined - it might be optimised away, but
238	not inlined into other functions. This is useful if you know your function	268	not inlined into other functions. This is useful if you know your function
239	is rarely called and large enough for inlining not to be helpful.	269	is rarely called and large enough for inlining not to be helpful.
240		270
241	=item ecb_noreturn	271	=item ecb_noreturn
242		272
…		…
263		293
264	Example: multiply a vector, and allow the compiler to parallelise the	294	Example: multiply a vector, and allow the compiler to parallelise the
265	loop, because it knows it doesn't overwrite input values.	295	loop, because it knows it doesn't overwrite input values.
266		296
267	void	297	void
268	multiply (float *ecb_restrict src,	298	multiply (ecb_restrict float *src,
269	float *ecb_restrict dst,	299	ecb_restrict float *dst,
270	int len, float factor)	300	int len, float factor)
271	{	301	{
272	int i;	302	int i;
273		303
274	for (i = 0; i < len; ++i)	304	for (i = 0; i < len; ++i)
…		…
372		402
373	=head2 OPTIMISATION HINTS	403	=head2 OPTIMISATION HINTS
374		404
375	=over 4	405	=over 4
376		406
377	=item bool ecb_is_constant(expr)	407	=item bool ecb_is_constant (expr)
378		408
379	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
380	constant, and false otherwise.	410	constant, and false otherwise.
381		411
382	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
…		…
400	return is_constant (n) && !(n & (n - 1))	430	return is_constant (n) && !(n & (n - 1))
401	? rndm16 () & (num - 1)	431	? rndm16 () & (num - 1)
402	: (n * (uint32_t)rndm16 ()) >> 16;	432	: (n * (uint32_t)rndm16 ()) >> 16;
403	}	433	}
404		434
405	=item bool ecb_expect (expr, value)	435	=item ecb_expect (expr, value)
406		436
407	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
408	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
409	branch optimisations.	439	branch optimisations.
410		440
…		…
457	{	487	{
458	if (ecb_expect_false (current + size > end))	488	if (ecb_expect_false (current + size > end))
459	real_reserve_method (size); /* presumably noinline */	489	real_reserve_method (size); /* presumably noinline */
460	}	490	}
461		491
462	=item bool ecb_assume (cond)	492	=item ecb_assume (cond)
463		493
464	Try to tell the compiler that some condition is true, even if it's not	494	Tries to tell the compiler that some condition is true, even if it's not
465	obvious.	495	obvious. This is not a function, but a statement: it cannot be used in
		496	another expression.
466		497
467	This can be used to teach the compiler about invariants or other	498	This can be used to teach the compiler about invariants or other
468	conditions that might improve code generation, but which are impossible to	499	conditions that might improve code generation, but which are impossible to
469	deduce form the code itself.	500	deduce form the code itself.
470		501
…		…
487		518
488	Then the compiler I<might> be able to optimise out the second call	519	Then the compiler I<might> be able to optimise out the second call
489	completely, as it knows that C<< current + 1 > end >> is false and the	520	completely, as it knows that C<< current + 1 > end >> is false and the
490	call will never be executed.	521	call will never be executed.
491		522
492	=item bool ecb_unreachable ()	523	=item ecb_unreachable ()
493		524
494	This function does nothing itself, except tell the compiler that it will	525	This function does nothing itself, except tell the compiler that it will
495	never be executed. Apart from suppressing a warning in some cases, this	526	never be executed. Apart from suppressing a warning in some cases, this
496	function can be used to implement C<ecb_assume> or similar functions.	527	function can be used to implement C<ecb_assume> or similar functionality.
497		528
498	=item bool ecb_prefetch (addr, rw, locality)	529	=item ecb_prefetch (addr, rw, locality)
499		530
500	Tells the compiler to try to prefetch memory at the given C<addr>ess	531	Tells the compiler to try to prefetch memory at the given C<addr>ess
501	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of	532	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of
502	C<0> means that there will only be one access later, C<3> means that	533	C<0> means that there will only be one access later, C<3> means that
503	the data will likely be accessed very often, and values in between mean	534	the data will likely be accessed very often, and values in between mean
504	something... in between. The memory pointed to by the address does not	535	something... in between. The memory pointed to by the address does not
505	need to be accessible (it could be a null pointer for example), but C<rw>	536	need to be accessible (it could be a null pointer for example), but C<rw>
506	and C<locality> must be compile-time constants.	537	and C<locality> must be compile-time constants.
507		538
		539	This is a statement, not a function: you cannot use it as part of an
		540	expression.
		541
508	An obvious way to use this is to prefetch some data far away, in a big	542	An obvious way to use this is to prefetch some data far away, in a big
509	array you loop over. This prefetches memory some 128 array elements later,	543	array you loop over. This prefetches memory some 128 array elements later,
510	in the hope that it will be ready when the CPU arrives at that location.	544	in the hope that it will be ready when the CPU arrives at that location.
511		545
512	int sum = 0;	546	int sum = 0;
…		…
564		598
565	=item bool ecb_is_pot32 (uint32_t x)	599	=item bool ecb_is_pot32 (uint32_t x)
566		600
567	=item bool ecb_is_pot64 (uint32_t x)	601	=item bool ecb_is_pot64 (uint32_t x)
568		602
569	Return true iff C<x> is a power of two or C<x == 0>.	603	Returns true iff C<x> is a power of two or C<x == 0>.
570		604
571	For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>.	605	For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>.
572		606
573	=item int ecb_ld32 (uint32_t x)	607	=item int ecb_ld32 (uint32_t x)
574		608
575	=item int ecb_ld64 (uint64_t x)	609	=item int ecb_ld64 (uint64_t x)
576		610
…		…
652		686
653	=head2 FLOATING POINT FIDDLING	687	=head2 FLOATING POINT FIDDLING
654		688
655	=over 4	689	=over 4
656		690
		691	=item ECB_INFINITY
		692
		693	Evaluates to positive infinity if supported by the platform, otherwise to
		694	a truly huge number.
		695
		696	=item ECB_NAN
		697
		698	Evaluates to a quiet NAN if supported by the platform, otherwise to
		699	C<ECB_INFINITY>.
		700
		701	=item float ecb_ldexpf (float x, int exp)
		702
		703	Same as C<ldexpf>, but always available.
		704
657	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]	705	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
658		706
659	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]	707	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
660		708
661	These functions each take an argument in the native C<float> or C<double>	709	These functions each take an argument in the native C<float> or C<double>
…		…
684	/* this results in a single add instruction to toggle the bit, and 4 extra */	732	/* this results in a single add instruction to toggle the bit, and 4 extra */
685	/* instructions to move the float value to an integer register and back. */	733	/* instructions to move the float value to an integer register and back. */
686		734
687	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)	735	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
688		736
		737	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		738
689	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]	739	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
690		740
691	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]	741	=item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM]
692		742
693	The reverse operation of the previos function - takes the bit representation	743	The reverse operation of the previous function - takes the bit
694	of an IEEE binary32 or binary64 number and converts it to the native C<float>	744	representation of an IEEE binary16, binary32 or binary64 number and
695	or C<double> format.	745	converts it to the native C<float> or C<double> format.
696		746
697	This function should work even when the native floating point format isn't	747	This function should work even when the native floating point format isn't
698	IEEE compliant, of course at a speed and code size penalty, and of course	748	IEEE compliant, of course at a speed and code size penalty, and of course
699	also within reasonable limits (it tries to convert normals and denormals,	749	also within reasonable limits (it tries to convert normals and denormals,
700	and might be lucky for infinities, and with extraordinary luck, also for	750	and might be lucky for infinities, and with extraordinary luck, also for
…		…
790	dependencies on the math library (usually called F<-lm>) - these are	840	dependencies on the math library (usually called F<-lm>) - these are
791	marked with [-UECB_NO_LIBM].	841	marked with [-UECB_NO_LIBM].
792		842
793	=back	843	=back
794		844
		845	=head1 UNDOCUMENTED FUNCTIONALITY
795		846
		847	F<ecb.h> is full of undocumented functionality as well, some of which is
		848	intended to be internal-use only, some of which we forgot to document, and
		849	some of which we hide because we are not sure we will keep the interface
		850	stable.
		851
		852	While you are welcome to rummage around and use whatever you find useful
		853	(we can't stop you), keep in mind that we will change undocumented
		854	functionality in incompatible ways without thinking twice, while we are
		855	considerably more conservative with documented things.
		856
		857	=head1 AUTHORS
		858
		859	C<libecb> is designed and maintained by:
		860
		861	Emanuele Giaquinta <e.giaquinta@glauco.it>
		862	Marc Alexander Lehmann <schmorp@schmorp.de>
		863
		864

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Comparing cvsroot/libecb/ecb.pod (file contents): Revision 1.56 by root, Mon Jun 9 17:31:57 2014 UTC vs. Revision 1.70 by root, Tue Sep 1 16:14:42 2015 UTC

Diff Legend

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.56 by root, Mon Jun 9 17:31:57 2014 UTC vs.
Revision 1.70 by root, Tue Sep 1 16:14:42 2015 UTC