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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.47 by root, Tue May 29 16:51:24 2012 UTC vs.
Revision 1.64 by root, Wed Feb 18 20:48:59 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 compliant to C99 (ISO/IEC	88	True if the implementation claims to be compliant to C99 (ISO/IEC
87	9899:1999) or any later version.	89	9899:1999) or any later version, while not claiming to be C++.
88		90
89	Note that later versions (ECB_C11) remove core features again (for	91	Note that later versions (ECB_C11) remove core features again (for
90	example, variable length arrays).	92	example, variable length arrays).
91		93
92	=item ECB_C11	94	=item ECB_C11
93		95
94	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
95	9899:2011) or any later version.	97	9899:2011) or any later version, while not claiming to be C++.
96		98
97	=item ECB_CPP	99	=item ECB_CPP
98		100
99	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
100	value, which is typically true for C++ compilers.	102	value, which is typically true for C++ compilers.
101		103
102	=item ECB_CPP98
103
104	True if the implementation claims to be compliant to ISO/IEC 14882:1998
105	(the first C++ ISO standard) or any later version. Typically true for all
106	C++ compilers.
107
108	=item ECB_CPP11	104	=item ECB_CPP11
109		105
110	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
111	(C++11) or any later version.	107	(C++11) or any later version.
112		108
113	=item ECB_GCC_VERSION(major,minor)	109	=item ECB_GCC_VERSION (major, minor)
114		110
115	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)
116	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
117	higher.	113	higher.
118		114
119	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
120	compatible but aren't.	116	compatible but aren't.
121		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
122	=back	166	=back
123		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
124	=head2 GCC ATTRIBUTES	210	=head2 ATTRIBUTES
125		211
126	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
127	attributes that you can assign to functions, variables and sometimes even	213	assigned to functions, variables and sometimes even types - much like
128	types - much like C<const> or C<volatile> in C.	214	C<const> or C<volatile> in C. They are implemented using either GCC
129		215	attributes or other compiler/language specific features. Attributes
130	While GCC allows declarations to show up in many surprising places,
131	but not in many expected places, the safest way is to put attribute
132	declarations before the whole declaration:	216	declarations must be put before the whole declaration:
133		217
134	ecb_const int mysqrt (int a);	218	ecb_const int mysqrt (int a);
135	ecb_unused int i;	219	ecb_unused int i;
136		220
137	For variables, it is often nicer to put the attribute after the name, and
138	avoid multiple declarations using commas:
139
140	int i ecb_unused;
141
142	=over 4	221	=over 4
143
144	=item ecb_attribute ((attrs...))
145
146	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
147	nothing on other compilers, so the effect is that only GCC sees these.
148
149	Example: use the C<deprecated> attribute on a function.
150
151	ecb_attribute((__deprecated__)) void
152	do_not_use_me_anymore (void);
153		222
154	=item ecb_unused	223	=item ecb_unused
155		224
156	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
157	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.
158	declare a variable but do not always use it:	227	declare a variable but do not always use it:
159		228
160	{	229	{
161	int var ecb_unused;	230	ecb_unused int var;
162		231
163	#ifdef SOMECONDITION	232	#ifdef SOMECONDITION
164	var = ...;	233	var = ...;
165	return var;	234	return var;
166	#else	235	#else
167	return 0;	236	return 0;
168	#endif	237	#endif
169	}	238	}
170		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
171	=item ecb_inline	251	=item ecb_inline
172		252
173	This is not actually an attribute, but you use it like one. It expands
174	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
175	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
176	for code size or speed reasons.	255	inlined, for code size or speed reasons.
177		256
178	Example: inline this function, it surely will reduce codesize.	257	Example: inline this function, it surely will reduce codesize.
179		258
180	ecb_inline int	259	ecb_inline int
181	negmul (int a, int b)	260	negmul (int a, int b)
…		…
203	}	282	}
204		283
205	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
206	its own, so this is mainly useful for declarations.	285	its own, so this is mainly useful for declarations.
207		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
208	=item ecb_const	308	=item ecb_const
209		309
210	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,
211	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
212	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
…		…
272	functions only called in exceptional or rare cases.	372	functions only called in exceptional or rare cases.
273		373
274	=item ecb_artificial	374	=item ecb_artificial
275		375
276	Declares the function as "artificial", in this case meaning that this	376	Declares the function as "artificial", in this case meaning that this
277	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
278	- 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
279	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
280	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.
281		381
282	Marking them as artificial will instruct the debugger about just this,	382	Marking them as artificial will instruct the debugger about just this,
…		…
302		402
303	=head2 OPTIMISATION HINTS	403	=head2 OPTIMISATION HINTS
304		404
305	=over 4	405	=over 4
306		406
307	=item bool ecb_is_constant(expr)	407	=item bool ecb_is_constant (expr)
308		408
309	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
310	constant, and false otherwise.	410	constant, and false otherwise.
311		411
312	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
…		…
330	return is_constant (n) && !(n & (n - 1))	430	return is_constant (n) && !(n & (n - 1))
331	? rndm16 () & (num - 1)	431	? rndm16 () & (num - 1)
332	: (n * (uint32_t)rndm16 ()) >> 16;	432	: (n * (uint32_t)rndm16 ()) >> 16;
333	}	433	}
334		434
335	=item bool ecb_expect (expr, value)	435	=item ecb_expect (expr, value)
336		436
337	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
338	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
339	branch optimisations.	439	branch optimisations.
340		440
…		…
387	{	487	{
388	if (ecb_expect_false (current + size > end))	488	if (ecb_expect_false (current + size > end))
389	real_reserve_method (size); /* presumably noinline */	489	real_reserve_method (size); /* presumably noinline */
390	}	490	}
391		491
392	=item bool ecb_assume (cond)	492	=item ecb_assume (cond)
393		493
394	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
395	obvious.	495	obvious.
396		496
397	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
…		…
417		517
418	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
419	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
420	call will never be executed.	520	call will never be executed.
421		521
422	=item bool ecb_unreachable ()	522	=item ecb_unreachable ()
423		523
424	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
425	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
426	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.
427		527
428	=item bool ecb_prefetch (addr, rw, locality)	528	=item ecb_prefetch (addr, rw, locality)
429		529
430	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
431	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
432	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
433	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
…		…
578	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on	678	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
579	x86).	679	x86).
580		680
581	=back	681	=back
582		682
		683	=head2 FLOATING POINT FIDDLING
		684
		685	=over 4
		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
		701	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
		702
		703	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
		704
		705	These functions each take an argument in the native C<float> or C<double>
		706	type and return the IEEE 754 bit representation of it.
		707
		708	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
		709	will be the most significant bit, followed by exponent and mantissa.
		710
		711	This function should work even when the native floating point format isn't
		712	IEEE compliant, of course at a speed and code size penalty, and of course
		713	also within reasonable limits (it tries to convert NaNs, infinities and
		714	denormals, but will likely convert negative zero to positive zero).
		715
		716	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		717	be able to optimise away this function completely.
		718
		719	These functions can be helpful when serialising floats to the network - you
		720	can serialise the return value like a normal uint32_t/uint64_t.
		721
		722	Another use for these functions is to manipulate floating point values
		723	directly.
		724
		725	Silly example: toggle the sign bit of a float.
		726
		727	/* On gcc-4.7 on amd64, */
		728	/* this results in a single add instruction to toggle the bit, and 4 extra */
		729	/* instructions to move the float value to an integer register and back. */
		730
		731	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
		732
		733	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		734
		735	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
		736
		737	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]
		738
		739	The reverse operation of the previous function - takes the bit
		740	representation of an IEEE binary16, binary32 or binary64 number and
		741	converts it to the native C<float> or C<double> format.
		742
		743	This function should work even when the native floating point format isn't
		744	IEEE compliant, of course at a speed and code size penalty, and of course
		745	also within reasonable limits (it tries to convert normals and denormals,
		746	and might be lucky for infinities, and with extraordinary luck, also for
		747	negative zero).
		748
		749	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		750	be able to optimise away this function completely.
		751
		752	=back
		753
583	=head2 ARITHMETIC	754	=head2 ARITHMETIC
584		755
585	=over 4	756	=over 4
586		757
587	=item x = ecb_mod (m, n)	758	=item x = ecb_mod (m, n)
…		…
641		812
642	These symbols need to be defined before including F<ecb.h> the first time.	813	These symbols need to be defined before including F<ecb.h> the first time.
643		814
644	=over 4	815	=over 4
645		816
646	=item ECB_NO_THRADS	817	=item ECB_NO_THREADS
647		818
648	If F<ecb.h> is never used from multiple threads, then this symbol can	819	If F<ecb.h> is never used from multiple threads, then this symbol can
649	be defined, in which case memory fences (and similar constructs) are	820	be defined, in which case memory fences (and similar constructs) are
650	completely removed, leading to more efficient code and fewer dependencies.	821	completely removed, leading to more efficient code and fewer dependencies.
651		822
…		…
657	multiple threads, but never concurrently (e.g. if the system the program	828	multiple threads, but never concurrently (e.g. if the system the program
658	runs on has only a single CPU with a single core, no hyperthreading and so	829	runs on has only a single CPU with a single core, no hyperthreading and so
659	on), then this symbol can be defined, leading to more efficient code and	830	on), then this symbol can be defined, leading to more efficient code and
660	fewer dependencies.	831	fewer dependencies.
661		832
		833	=item ECB_NO_LIBM
		834
		835	When defined to C<1>, do not export any functions that might introduce
		836	dependencies on the math library (usually called F<-lm>) - these are
		837	marked with [-UECB_NO_LIBM].
		838
662	=back	839	=back
663		840
664		841

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Comparing cvsroot/libecb/ecb.pod (file contents): Revision 1.47 by root, Tue May 29 16:51:24 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 1.47 by root, Tue May 29 16:51:24 2012 UTC vs.
Revision 1.64 by root, Wed Feb 18 20:48:59 2015 UTC