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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.46 by sf-exg, Tue May 29 14:57:24 2012 UTC vs.
Revision 1.62 by root, Wed Feb 18 20:29:27 2015 UTC

…		…
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_t int16_t uint16_t
64	int32_t uint32_t int64_t uint64_t	64	int32_t uint32_t int64_t uint64_t
65	intptr_t uintptr_t ptrdiff_t	65	intptr_t uintptr_t
66		66
67	The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this	67	The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this
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>.
		72
71	=head2 LANGUAGE/COMPILER VERSIONS	73	=head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS
72		74
73	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
74	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
75	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).
76		78
77	=over 4	79	=over 4
78		80
79	=item ECB_C	81	=item ECB_C
80		82
81	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,
82	which is typically true for both C and C++ compilers.	84	while not claiming to be C++.
83		85
84	=item ECB_C99	86	=item ECB_C99
85		87
86	True if the implementation claims to be C99 compliant.	88	True if the implementation claims to be compliant to C99 (ISO/IEC
		89	9899:1999) or any later version, while not claiming to be C++.
		90
		91	Note that later versions (ECB_C11) remove core features again (for
		92	example, variable length arrays).
87		93
88	=item ECB_C11	94	=item ECB_C11
89		95
90	True if the implementation claims to be C11 compliant.	96	True if the implementation claims to be compliant to C11 (ISO/IEC
		97	9899:2011) or any later version, while not claiming to be C++.
91		98
92	=item ECB_CPP	99	=item ECB_CPP
93		100
94	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
95	value, which is typically true for C++ compilers.	102	value, which is typically true for C++ compilers.
96		103
97	=item ECB_CPP98
98
99	True if the implementation claims to be compliant to ISO/IEC 14882:1998
100	(the first C++ ISO standard) or any later version. Typically true for all
101	C++ compilers.
102
103	=item ECB_CPP11	104	=item ECB_CPP11
104		105
105	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
106	(C++11) or any later version.	107	(C++11) or any later version.
107		108
108	=item ECB_GCC_VERSION(major,minor)	109	=item ECB_GCC_VERSION (major, minor)
109		110
110	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)
111	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
112	higher.	113	higher.
113		114
114	This macro tries to return false on compilers that claim to be GCC	115	This macro tries to return false on compilers that claim to be GCC
115	compatible but aren't.	116	compatible but aren't.
116		117
		118	=item ECB_EXTERN_C
		119
		120	Expands to C<extern "C"> in C++, and a simple C<extern> in C.
		121
		122	This can be used to declare a single external C function:
		123
		124	ECB_EXTERN_C int printf (const char *format, ...);
		125
		126	=item ECB_EXTERN_C_BEG / ECB_EXTERN_C_END
		127
		128	These two macros can be used to wrap multiple C<extern "C"> definitions -
		129	they expand to nothing in C.
		130
		131	They are most useful in header files:
		132
		133	ECB_EXTERN_C_BEG
		134
		135	int mycfun1 (int x);
		136	int mycfun2 (int x);
		137
		138	ECB_EXTERN_C_END
		139
		140	=item ECB_STDFP
		141
		142	If this evaluates to a true value (suitable for testing in by the
		143	preprocessor), then C<float> and C<double> use IEEE 754 single/binary32
		144	and double/binary64 representations internally I<and> the endianness of
		145	both types match the endianness of C<uint32_t> and C<uint64_t>.
		146
		147	This means you can just copy the bits of a C<float> (or C<double>) to an
		148	C<uint32_t> (or C<uint64_t>) and get the raw IEEE 754 bit representation
		149	without having to think about format or endianness.
		150
		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
		153	side.
		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
117	=back	166	=back
118		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	=back
		193
119	=head2 GCC ATTRIBUTES	194	=head2 ATTRIBUTES
120		195
121	A major part of libecb deals with GCC attributes. These are additional	196	A major part of libecb deals with additional attributes that can be
122	attributes that you can assign to functions, variables and sometimes even	197	assigned to functions, variables and sometimes even types - much like
123	types - much like C<const> or C<volatile> in C.	198	C<const> or C<volatile> in C. They are implemented using either GCC
124		199	attributes or other compiler/language specific features. Attributes
125	While GCC allows declarations to show up in many surprising places,
126	but not in many expected places, the safest way is to put attribute
127	declarations before the whole declaration:	200	declarations must be put before the whole declaration:
128		201
129	ecb_const int mysqrt (int a);	202	ecb_const int mysqrt (int a);
130	ecb_unused int i;	203	ecb_unused int i;
131		204
132	For variables, it is often nicer to put the attribute after the name, and
133	avoid multiple declarations using commas:
134
135	int i ecb_unused;
136
137	=over 4	205	=over 4
138
139	=item ecb_attribute ((attrs...))
140
141	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
142	nothing on other compilers, so the effect is that only GCC sees these.
143
144	Example: use the C<deprecated> attribute on a function.
145
146	ecb_attribute((__deprecated__)) void
147	do_not_use_me_anymore (void);
148		206
149	=item ecb_unused	207	=item ecb_unused
150		208
151	Marks a function or a variable as "unused", which simply suppresses a	209	Marks a function or a variable as "unused", which simply suppresses a
152	warning by GCC when it detects it as unused. This is useful when you e.g.	210	warning by GCC when it detects it as unused. This is useful when you e.g.
153	declare a variable but do not always use it:	211	declare a variable but do not always use it:
154		212
155	{	213	{
156	int var ecb_unused;	214	ecb_unused int var;
157		215
158	#ifdef SOMECONDITION	216	#ifdef SOMECONDITION
159	var = ...;	217	var = ...;
160	return var;	218	return var;
161	#else	219	#else
162	return 0;	220	return 0;
163	#endif	221	#endif
164	}	222	}
165		223
		224	=item ecb_deprecated
		225
		226	Similar to C<ecb_unused>, but marks a function, variable or type as
		227	deprecated. This makes some compilers warn when the type is used.
		228
		229	=item ecb_deprecated_message (message)
		230
		231	Same as C<ecb_deprecated>, but if possible, supply a diagnostic that is
		232	used instead of a generic depreciation message when the object is being
		233	used.
		234
166	=item ecb_inline	235	=item ecb_inline
167		236
168	This is not actually an attribute, but you use it like one. It expands
169	either to C<static inline> or to just C<static>, if inline isn't	237	Expands either to C<static inline> or to just C<static>, if inline
170	supported. It should be used to declare functions that should be inlined,	238	isn't supported. It should be used to declare functions that should be
171	for code size or speed reasons.	239	inlined, for code size or speed reasons.
172		240
173	Example: inline this function, it surely will reduce codesize.	241	Example: inline this function, it surely will reduce codesize.
174		242
175	ecb_inline int	243	ecb_inline int
176	negmul (int a, int b)	244	negmul (int a, int b)
…		…
198	}	266	}
199		267
200	In this case, the compiler would probably be smart enough to deduce it on	268	In this case, the compiler would probably be smart enough to deduce it on
201	its own, so this is mainly useful for declarations.	269	its own, so this is mainly useful for declarations.
202		270
		271	=item ecb_restrict
		272
		273	Expands to the C<restrict> keyword or equivalent on compilers that support
		274	them, and to nothing on others. Must be specified on a pointer type or
		275	an array index to indicate that the memory doesn't alias with any other
		276	restricted pointer in the same scope.
		277
		278	Example: multiply a vector, and allow the compiler to parallelise the
		279	loop, because it knows it doesn't overwrite input values.
		280
		281	void
		282	multiply (ecb_restrict float *src,
		283	ecb_restrict float *dst,
		284	int len, float factor)
		285	{
		286	int i;
		287
		288	for (i = 0; i < len; ++i)
		289	dst [i] = src [i] * factor;
		290	}
		291
203	=item ecb_const	292	=item ecb_const
204		293
205	Declares that the function only depends on the values of its arguments,	294	Declares that the function only depends on the values of its arguments,
206	much like a mathematical function. It specifically does not read or write	295	much like a mathematical function. It specifically does not read or write
207	any memory any arguments might point to, global variables, or call any	296	any memory any arguments might point to, global variables, or call any
…		…
267	functions only called in exceptional or rare cases.	356	functions only called in exceptional or rare cases.
268		357
269	=item ecb_artificial	358	=item ecb_artificial
270		359
271	Declares the function as "artificial", in this case meaning that this	360	Declares the function as "artificial", in this case meaning that this
272	function is not really mean to be a function, but more like an accessor	361	function is not really meant to be a function, but more like an accessor
273	- many methods in C++ classes are mere accessor functions, and having a	362	- many methods in C++ classes are mere accessor functions, and having a
274	crash reported in such a method, or single-stepping through them, is not	363	crash reported in such a method, or single-stepping through them, is not
275	usually so helpful, especially when it's inlined to just a few instructions.	364	usually so helpful, especially when it's inlined to just a few instructions.
276		365
277	Marking them as artificial will instruct the debugger about just this,	366	Marking them as artificial will instruct the debugger about just this,
…		…
297		386
298	=head2 OPTIMISATION HINTS	387	=head2 OPTIMISATION HINTS
299		388
300	=over 4	389	=over 4
301		390
302	=item bool ecb_is_constant(expr)	391	=item bool ecb_is_constant (expr)
303		392
304	Returns true iff the expression can be deduced to be a compile-time	393	Returns true iff the expression can be deduced to be a compile-time
305	constant, and false otherwise.	394	constant, and false otherwise.
306		395
307	For example, when you have a C<rndm16> function that returns a 16 bit	396	For example, when you have a C<rndm16> function that returns a 16 bit
…		…
325	return is_constant (n) && !(n & (n - 1))	414	return is_constant (n) && !(n & (n - 1))
326	? rndm16 () & (num - 1)	415	? rndm16 () & (num - 1)
327	: (n * (uint32_t)rndm16 ()) >> 16;	416	: (n * (uint32_t)rndm16 ()) >> 16;
328	}	417	}
329		418
330	=item bool ecb_expect (expr, value)	419	=item ecb_expect (expr, value)
331		420
332	Evaluates C<expr> and returns it. In addition, it tells the compiler that	421	Evaluates C<expr> and returns it. In addition, it tells the compiler that
333	the C<expr> evaluates to C<value> a lot, which can be used for static	422	the C<expr> evaluates to C<value> a lot, which can be used for static
334	branch optimisations.	423	branch optimisations.
335		424
…		…
382	{	471	{
383	if (ecb_expect_false (current + size > end))	472	if (ecb_expect_false (current + size > end))
384	real_reserve_method (size); /* presumably noinline */	473	real_reserve_method (size); /* presumably noinline */
385	}	474	}
386		475
387	=item bool ecb_assume (cond)	476	=item ecb_assume (cond)
388		477
389	Try to tell the compiler that some condition is true, even if it's not	478	Try to tell the compiler that some condition is true, even if it's not
390	obvious.	479	obvious.
391		480
392	This can be used to teach the compiler about invariants or other	481	This can be used to teach the compiler about invariants or other
…		…
412		501
413	Then the compiler I<might> be able to optimise out the second call	502	Then the compiler I<might> be able to optimise out the second call
414	completely, as it knows that C<< current + 1 > end >> is false and the	503	completely, as it knows that C<< current + 1 > end >> is false and the
415	call will never be executed.	504	call will never be executed.
416		505
417	=item bool ecb_unreachable ()	506	=item ecb_unreachable ()
418		507
419	This function does nothing itself, except tell the compiler that it will	508	This function does nothing itself, except tell the compiler that it will
420	never be executed. Apart from suppressing a warning in some cases, this	509	never be executed. Apart from suppressing a warning in some cases, this
421	function can be used to implement C<ecb_assume> or similar functions.	510	function can be used to implement C<ecb_assume> or similar functions.
422		511
423	=item bool ecb_prefetch (addr, rw, locality)	512	=item ecb_prefetch (addr, rw, locality)
424		513
425	Tells the compiler to try to prefetch memory at the given C<addr>ess	514	Tells the compiler to try to prefetch memory at the given C<addr>ess
426	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of	515	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of
427	C<0> means that there will only be one access later, C<3> means that	516	C<0> means that there will only be one access later, C<3> means that
428	the data will likely be accessed very often, and values in between mean	517	the data will likely be accessed very often, and values in between mean
…		…
573	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on	662	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
574	x86).	663	x86).
575		664
576	=back	665	=back
577		666
		667	=head2 FLOATING POINT FIDDLING
		668
		669	=over 4
		670
		671	=item ECB_INFINITY
		672
		673	Evaluates to positive infinity if supported by the platform, otherwise to
		674	a truly huge number.
		675
		676	=item ECB_NON
		677
		678	Evaluates to a quiet NAN if supported by the platform, otherwise to
		679	C<ECB_INFINITY>.
		680
		681	=item float ecb_ldexpf (float x, int exp)
		682
		683	Same as C<ldexpf>, but always available.
		684
		685	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
		686
		687	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
		688
		689	These functions each take an argument in the native C<float> or C<double>
		690	type and return the IEEE 754 bit representation of it.
		691
		692	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
		693	will be the most significant bit, followed by exponent and mantissa.
		694
		695	This function should work even when the native floating point format isn't
		696	IEEE compliant, of course at a speed and code size penalty, and of course
		697	also within reasonable limits (it tries to convert NaNs, infinities and
		698	denormals, but will likely convert negative zero to positive zero).
		699
		700	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		701	be able to optimise away this function completely.
		702
		703	These functions can be helpful when serialising floats to the network - you
		704	can serialise the return value like a normal uint32_t/uint64_t.
		705
		706	Another use for these functions is to manipulate floating point values
		707	directly.
		708
		709	Silly example: toggle the sign bit of a float.
		710
		711	/* On gcc-4.7 on amd64, */
		712	/* this results in a single add instruction to toggle the bit, and 4 extra */
		713	/* instructions to move the float value to an integer register and back. */
		714
		715	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
		716
		717	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		718
		719	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
		720
		721	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]
		722
		723	The reverse operation of the previous function - takes the bit
		724	representation of an IEEE binary16, binary32 or binary64 number and
		725	converts it to the native C<float> or C<double> format.
		726
		727	This function should work even when the native floating point format isn't
		728	IEEE compliant, of course at a speed and code size penalty, and of course
		729	also within reasonable limits (it tries to convert normals and denormals,
		730	and might be lucky for infinities, and with extraordinary luck, also for
		731	negative zero).
		732
		733	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		734	be able to optimise away this function completely.
		735
		736	=back
		737
578	=head2 ARITHMETIC	738	=head2 ARITHMETIC
579		739
580	=over 4	740	=over 4
581		741
582	=item x = ecb_mod (m, n)	742	=item x = ecb_mod (m, n)
…		…
636		796
637	These symbols need to be defined before including F<ecb.h> the first time.	797	These symbols need to be defined before including F<ecb.h> the first time.
638		798
639	=over 4	799	=over 4
640		800
641	=item ECB_NO_THRADS	801	=item ECB_NO_THREADS
642		802
643	If F<ecb.h> is never used from multiple threads, then this symbol can	803	If F<ecb.h> is never used from multiple threads, then this symbol can
644	be defined, in which case memory fences (and similar constructs) are	804	be defined, in which case memory fences (and similar constructs) are
645	completely removed, leading to more efficient code and fewer dependencies.	805	completely removed, leading to more efficient code and fewer dependencies.
646		806
…		…
652	multiple threads, but never concurrently (e.g. if the system the program	812	multiple threads, but never concurrently (e.g. if the system the program
653	runs on has only a single CPU with a single core, no hyperthreading and so	813	runs on has only a single CPU with a single core, no hyperthreading and so
654	on), then this symbol can be defined, leading to more efficient code and	814	on), then this symbol can be defined, leading to more efficient code and
655	fewer dependencies.	815	fewer dependencies.
656		816
		817	=item ECB_NO_LIBM
		818
		819	When defined to C<1>, do not export any functions that might introduce
		820	dependencies on the math library (usually called F<-lm>) - these are
		821	marked with [-UECB_NO_LIBM].
		822
657	=back	823	=back
658		824
659		825

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Comparing cvsroot/libecb/ecb.pod (file contents): Revision 1.46 by sf-exg, Tue May 29 14:57:24 2012 UTC vs. Revision 1.62 by root, Wed Feb 18 20:29:27 2015 UTC

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Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.46 by sf-exg, Tue May 29 14:57:24 2012 UTC vs.
Revision 1.62 by root, Wed Feb 18 20:29:27 2015 UTC