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

Comparing libecb/ecb.pod (file contents):
Revision 1.51 by root, Thu Jul 19 18:08:58 2012 UTC vs.
Revision 1.66 by sf-exg, Fri Feb 20 11:28:08 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, supplies 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)
…		…
216	return - (a * b);	262	return - (a * b);
217	}	263	}
218		264
219	=item ecb_noinline	265	=item ecb_noinline
220		266
221	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
222	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
223	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.
224		270
225	=item ecb_noreturn	271	=item ecb_noreturn
226		272
…		…
236	}	282	}
237		283
238	In this case, the compiler would probably be smart enough to deduce it on	284	In this case, the compiler would probably be smart enough to deduce it on
239	its own, so this is mainly useful for declarations.	285	its own, so this is mainly useful for declarations.
240		286
		287	=item ecb_restrict
		288
		289	Expands to the C<restrict> keyword or equivalent on compilers that support
		290	them, and to nothing on others. Must be specified on a pointer type or
		291	an array index to indicate that the memory doesn't alias with any other
		292	restricted pointer in the same scope.
		293
		294	Example: multiply a vector, and allow the compiler to parallelise the
		295	loop, because it knows it doesn't overwrite input values.
		296
		297	void
		298	multiply (ecb_restrict float *src,
		299	ecb_restrict float *dst,
		300	int len, float factor)
		301	{
		302	int i;
		303
		304	for (i = 0; i < len; ++i)
		305	dst [i] = src [i] * factor;
		306	}
		307
241	=item ecb_const	308	=item ecb_const
242		309
243	Declares that the function only depends on the values of its arguments,	310	Declares that the function only depends on the values of its arguments,
244	much like a mathematical function. It specifically does not read or write	311	much like a mathematical function. It specifically does not read or write
245	any memory any arguments might point to, global variables, or call any	312	any memory any arguments might point to, global variables, or call any
…		…
305	functions only called in exceptional or rare cases.	372	functions only called in exceptional or rare cases.
306		373
307	=item ecb_artificial	374	=item ecb_artificial
308		375
309	Declares the function as "artificial", in this case meaning that this	376	Declares the function as "artificial", in this case meaning that this
310	function is not really mean to be a function, but more like an accessor	377	function is not really meant to be a function, but more like an accessor
311	- many methods in C++ classes are mere accessor functions, and having a	378	- many methods in C++ classes are mere accessor functions, and having a
312	crash reported in such a method, or single-stepping through them, is not	379	crash reported in such a method, or single-stepping through them, is not
313	usually so helpful, especially when it's inlined to just a few instructions.	380	usually so helpful, especially when it's inlined to just a few instructions.
314		381
315	Marking them as artificial will instruct the debugger about just this,	382	Marking them as artificial will instruct the debugger about just this,
…		…
335		402
336	=head2 OPTIMISATION HINTS	403	=head2 OPTIMISATION HINTS
337		404
338	=over 4	405	=over 4
339		406
340	=item bool ecb_is_constant(expr)	407	=item bool ecb_is_constant (expr)
341		408
342	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
343	constant, and false otherwise.	410	constant, and false otherwise.
344		411
345	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
…		…
363	return is_constant (n) && !(n & (n - 1))	430	return is_constant (n) && !(n & (n - 1))
364	? rndm16 () & (num - 1)	431	? rndm16 () & (num - 1)
365	: (n * (uint32_t)rndm16 ()) >> 16;	432	: (n * (uint32_t)rndm16 ()) >> 16;
366	}	433	}
367		434
368	=item bool ecb_expect (expr, value)	435	=item ecb_expect (expr, value)
369		436
370	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
371	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
372	branch optimisations.	439	branch optimisations.
373		440
…		…
420	{	487	{
421	if (ecb_expect_false (current + size > end))	488	if (ecb_expect_false (current + size > end))
422	real_reserve_method (size); /* presumably noinline */	489	real_reserve_method (size); /* presumably noinline */
423	}	490	}
424		491
425	=item bool ecb_assume (cond)	492	=item ecb_assume (cond)
426		493
427	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
428	obvious.	495	obvious. This is not a function, but a statement: it cannot be used in
		496	another expression.
429		497
430	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
431	conditions that might improve code generation, but which are impossible to	499	conditions that might improve code generation, but which are impossible to
432	deduce form the code itself.	500	deduce form the code itself.
433		501
…		…
450		518
451	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
452	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
453	call will never be executed.	521	call will never be executed.
454		522
455	=item bool ecb_unreachable ()	523	=item ecb_unreachable ()
456		524
457	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
458	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
459	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.
460		528
461	=item bool ecb_prefetch (addr, rw, locality)	529	=item ecb_prefetch (addr, rw, locality)
462		530
463	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
464	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
465	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
466	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
467	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
468	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>
469	and C<locality> must be compile-time constants.	537	and C<locality> must be compile-time constants.
470		538
		539	This is a statement, not a function: you cannot use it as part of an
		540	expression.
		541
471	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
472	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,
473	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.
474		545
475	int sum = 0;	546	int sum = 0;
…		…
527		598
528	=item bool ecb_is_pot32 (uint32_t x)	599	=item bool ecb_is_pot32 (uint32_t x)
529		600
530	=item bool ecb_is_pot64 (uint32_t x)	601	=item bool ecb_is_pot64 (uint32_t x)
531		602
532	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>.
533		604
534	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>.
535		606
536	=item int ecb_ld32 (uint32_t x)	607	=item int ecb_ld32 (uint32_t x)
537		608
538	=item int ecb_ld64 (uint64_t x)	609	=item int ecb_ld64 (uint64_t x)
539		610
…		…
615		686
616	=head2 FLOATING POINT FIDDLING	687	=head2 FLOATING POINT FIDDLING
617		688
618	=over 4	689	=over 4
619		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
620	=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]
621		706
622	=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]
623		708
624	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>
…		…
647	/* 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 */
648	/* 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. */
649		734
650	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)	735	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
651		736
		737	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		738
652	=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]
653		740
654	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]	741	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]
655		742
656	The reverse operation of the previos function - takes the bit representation	743	The reverse operation of the previous function - takes the bit
657	of an IEEE binary32 or binary64 number and converts it to the native C<float>	744	representation of an IEEE binary16, binary32 or binary64 number and
658	or C<double> format.	745	converts it to the native C<float> or C<double> format.
659		746
660	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
661	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
662	also within reasonable limits (it tries to convert normals and denormals,	749	also within reasonable limits (it tries to convert normals and denormals,
663	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

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Comparing libecb/ecb.pod (file contents): Revision 1.51 by root, Thu Jul 19 18:08:58 2012 UTC vs. Revision 1.66 by sf-exg, Fri Feb 20 11:28:08 2015 UTC

Diff Legend

Comparing libecb/ecb.pod (file contents):
Revision 1.51 by root, Thu Jul 19 18:08:58 2012 UTC vs.
Revision 1.66 by sf-exg, Fri Feb 20 11:28:08 2015 UTC