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

Comparing libecb/ecb.pod (file contents):
Revision 1.14 by root, Thu May 26 23:23:08 2011 UTC vs.
Revision 1.45 by root, Tue May 29 14:35:43 2012 UTC

…		…
3	=head2 ABOUT LIBECB	3	=head2 ABOUT LIBECB
4		4
5	Libecb is currently a simple header file that doesn't require any	5	Libecb is currently a simple header file that doesn't require any
6	configuration to use or include in your project.	6	configuration to use or include in your project.
7		7
8	It's part of the e-suite of libraries, other memembers of which include	8	It's part of the e-suite of libraries, other members of which include
9	libev and libeio.	9	libev and libeio.
10		10
11	Its homepage can be found here:	11	Its homepage can be found here:
12		12
13	http://software.schmorp.de/pkg/libecb	13	http://software.schmorp.de/pkg/libecb
14		14
15	It mainly provides a number of wrappers around GCC built-ins, together	15	It mainly provides a number of wrappers around GCC built-ins, together
16	with replacement functions for other compilers. In addition to this,	16	with replacement functions for other compilers. In addition to this,
17	it provides a number of other lowlevel C utilities, such endienness	17	it provides a number of other lowlevel C utilities, such as endianness
18	detection, byte swapping or bit rotations.	18	detection, byte swapping or bit rotations.
		19
		20	Or in other words, things that should be built into any standard C system,
		21	but aren't, implemented as efficient as possible with GCC, and still
		22	correct with other compilers.
19		23
20	More might come.	24	More might come.
21		25
22	=head2 ABOUT THE HEADER	26	=head2 ABOUT THE HEADER
23		27
…		…
27	#include <ecb.h>	31	#include <ecb.h>
28		32
29	The header should work fine for both C and C++ compilation, and gives you	33	The header should work fine for both C and C++ compilation, and gives you
30	all of F<inttypes.h> in addition to the ECB symbols.	34	all of F<inttypes.h> in addition to the ECB symbols.
31		35
32	There are currently no objetc files to link to - future versions might	36	There are currently no object files to link to - future versions might
33	come with an (optional) object code library to link against, to reduce	37	come with an (optional) object code library to link against, to reduce
34	code size or gain access to additional features.	38	code size or gain access to additional features.
35		39
36	It also currently includes everything from F<inttypes.h>.	40	It also currently includes everything from F<inttypes.h>.
37		41
…		…
50	only a generic name is used (C<expr>, C<cond>, C<value> and so on), then	54	only a generic name is used (C<expr>, C<cond>, C<value> and so on), then
51	the corresponding function relies on C to implement the correct types, and	55	the corresponding function relies on C to implement the correct types, and
52	is usually implemented as a macro. Specifically, a "bool" in this manual	56	is usually implemented as a macro. Specifically, a "bool" in this manual
53	refers to any kind of boolean value, not a specific type.	57	refers to any kind of boolean value, not a specific type.
54		58
		59	=head2 TYPES / TYPE SUPPORT
		60
		61	ecb.h makes sure that the following types are defined (in the expected way):
		62
		63	int8_t uint8_t int16_t uint16_t
		64	int32_t uint32_t int64_t uint64_t
		65	intptr_t uintptr_t ptrdiff_t
		66
		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
		69	expressions.
		70
		71	=head2 LANGUAGE/COMPILER VERSIONS
		72
		73	All the following symbols expand to an expressionb that cna be tested in
		74	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).
		76
		77	=over 4
		78
		79	=item ECB_C
		80
		81	True if the implementation defines the C<__STDC__> macro to a true value,
		82	which is typically true for both C and C++ compilers.
		83
		84	=item ECB_C99
		85
		86	True if the implementation claims to be C99 compliant.
		87
		88	=item ECB_C11
		89
		90	True if the implementation claims to be C11 compliant.
		91
		92	=item ECB_CPP
		93
		94	True if the implementation defines the C<__cplusplus__> macro to a true
		95	value, which is typically true for C++ compilers.
		96
		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 vwersion. Typically true for all
		101	C++ compilers.
		102
		103	=item ECB_CPP11
		104
		105	True if the implementation claims to be compliant to ISO/IEC 14882:2011
		106	(C++11) or any later vwersion.
		107
		108	=item ECB_GCC_VERSION(major,minor)
		109
		110	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 givne version, or
		112	higher.
		113
		114	This macro tries to return false on compilers that claim to be GCC
		115	compatible but aren't.
		116
		117	=back
		118
55	=head2 GCC ATTRIBUTES	119	=head2 GCC ATTRIBUTES
56		120
57	blabla where to put, what others	121	A major part of libecb deals with GCC attributes. These are additional
		122	attributes that you can assign to functions, variables and sometimes even
		123	types - much like C<const> or C<volatile> in C.
		124
		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:
		128
		129	ecb_const int mysqrt (int a);
		130	ecb_unused int i;
		131
		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;
58		136
59	=over 4	137	=over 4
60		138
61	=item ecb_attribute ((attrs...))	139	=item ecb_attribute ((attrs...))
62		140
63	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and	141	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
64	to nothing on other compilers, so the effect is that only GCC sees these.	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);
65		148
66	=item ecb_unused	149	=item ecb_unused
67		150
68	Marks a function or a variable as "unused", which simply suppresses a	151	Marks a function or a variable as "unused", which simply suppresses a
69	warning by GCC when it detects it as unused. This is useful when you e.g.	152	warning by GCC when it detects it as unused. This is useful when you e.g.
70	declare a variable but do not always use it:	153	declare a variable but do not always use it:
71		154
		155	{
		156	int var ecb_unused;
		157
		158	#ifdef SOMECONDITION
		159	var = ...;
		160	return var;
		161	#else
		162	return 0;
		163	#endif
		164	}
		165
		166	=item ecb_inline
		167
		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
		170	supported. It should be used to declare functions that should be inlined,
		171	for code size or speed reasons.
		172
		173	Example: inline this function, it surely will reduce codesize.
		174
		175	ecb_inline int
		176	negmul (int a, int b)
72	{	177	{
73	int var ecb_unused;	178	return - (a * b);
74
75	#ifdef SOMECONDITION
76	var = ...;
77	return var;
78	#else
79	return 0;
80	#endif
81	}	179	}
82		180
83	=item ecb_noinline	181	=item ecb_noinline
84		182
85	Prevent a function from being inlined - it might be optimised away, but	183	Prevent a function from being inlined - it might be optimised away, but
86	not inlined into other functions. This is useful if you know your function	184	not inlined into other functions. This is useful if you know your function
87	is rarely called and large enough for inlining not to be helpful.	185	is rarely called and large enough for inlining not to be helpful.
88		186
89	=item ecb_noreturn	187	=item ecb_noreturn
90		188
		189	Marks a function as "not returning, ever". Some typical functions that
		190	don't return are C<exit> or C<abort> (which really works hard to not
		191	return), and now you can make your own:
		192
		193	ecb_noreturn void
		194	my_abort (const char *errline)
		195	{
		196	puts (errline);
		197	abort ();
		198	}
		199
		200	In this case, the compiler would probably be smart enough to deduce it on
		201	its own, so this is mainly useful for declarations.
		202
91	=item ecb_const	203	=item ecb_const
92		204
		205	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
		207	any memory any arguments might point to, global variables, or call any
		208	non-const functions. It also must not have any side effects.
		209
		210	Such a function can be optimised much more aggressively by the compiler -
		211	for example, multiple calls with the same arguments can be optimised into
		212	a single call, which wouldn't be possible if the compiler would have to
		213	expect any side effects.
		214
		215	It is best suited for functions in the sense of mathematical functions,
		216	such as a function returning the square root of its input argument.
		217
		218	Not suited would be a function that calculates the hash of some memory
		219	area you pass in, prints some messages or looks at a global variable to
		220	decide on rounding.
		221
		222	See C<ecb_pure> for a slightly less restrictive class of functions.
		223
93	=item ecb_pure	224	=item ecb_pure
94		225
		226	Similar to C<ecb_const>, declares a function that has no side
		227	effects. Unlike C<ecb_const>, the function is allowed to examine global
		228	variables and any other memory areas (such as the ones passed to it via
		229	pointers).
		230
		231	While these functions cannot be optimised as aggressively as C<ecb_const>
		232	functions, they can still be optimised away in many occasions, and the
		233	compiler has more freedom in moving calls to them around.
		234
		235	Typical examples for such functions would be C<strlen> or C<memcmp>. A
		236	function that calculates the MD5 sum of some input and updates some MD5
		237	state passed as argument would I<NOT> be pure, however, as it would modify
		238	some memory area that is not the return value.
		239
95	=item ecb_hot	240	=item ecb_hot
96		241
		242	This declares a function as "hot" with regards to the cache - the function
		243	is used so often, that it is very beneficial to keep it in the cache if
		244	possible.
		245
		246	The compiler reacts by trying to place hot functions near to each other in
		247	memory.
		248
		249	Whether a function is hot or not often depends on the whole program,
		250	and less on the function itself. C<ecb_cold> is likely more useful in
		251	practise.
		252
97	=item ecb_cold	253	=item ecb_cold
98		254
		255	The opposite of C<ecb_hot> - declares a function as "cold" with regards to
		256	the cache, or in other words, this function is not called often, or not at
		257	speed-critical times, and keeping it in the cache might be a waste of said
		258	cache.
		259
		260	In addition to placing cold functions together (or at least away from hot
		261	functions), this knowledge can be used in other ways, for example, the
		262	function will be optimised for size, as opposed to speed, and codepaths
		263	leading to calls to those functions can automatically be marked as if
		264	C<ecb_expect_false> had been used to reach them.
		265
		266	Good examples for such functions would be error reporting functions, or
		267	functions only called in exceptional or rare cases.
		268
99	=item ecb_artificial	269	=item ecb_artificial
		270
		271	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
		273	- 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
		275	usually so helpful, especially when it's inlined to just a few instructions.
		276
		277	Marking them as artificial will instruct the debugger about just this,
		278	leading to happier debugging and thus happier lives.
		279
		280	Example: in some kind of smart-pointer class, mark the pointer accessor as
		281	artificial, so that the whole class acts more like a pointer and less like
		282	some C++ abstraction monster.
		283
		284	template<typename T>
		285	struct my_smart_ptr
		286	{
		287	T *value;
		288
		289	ecb_artificial
		290	operator T *()
		291	{
		292	return value;
		293	}
		294	};
100		295
101	=back	296	=back
102		297
103	=head2 OPTIMISATION HINTS	298	=head2 OPTIMISATION HINTS
104		299
…		…
136		331
137	Evaluates C<expr> and returns it. In addition, it tells the compiler that	332	Evaluates C<expr> and returns it. In addition, it tells the compiler that
138	the C<expr> evaluates to C<value> a lot, which can be used for static	333	the C<expr> evaluates to C<value> a lot, which can be used for static
139	branch optimisations.	334	branch optimisations.
140		335
141	Usually, you want to use the more intuitive C<ecb_likely> and	336	Usually, you want to use the more intuitive C<ecb_expect_true> and
142	C<ecb_unlikely> functions instead.	337	C<ecb_expect_false> functions instead.
143		338
144	=item bool ecb_likely (bool)	339	=item bool ecb_expect_true (cond)
145		340
146	=item bool ecb_unlikely (bool)	341	=item bool ecb_expect_false (cond)
147		342
148	These two functions expect a expression that is true or false and return	343	These two functions expect a expression that is true or false and return
149	C<1> or C<0>, respectively, so when used in the condition of an C<if> or	344	C<1> or C<0>, respectively, so when used in the condition of an C<if> or
150	other conditional statement, it will not change the program:	345	other conditional statement, it will not change the program:
151		346
152	/* these two do the same thing */	347	/* these two do the same thing */
153	if (some_condition) ...;	348	if (some_condition) ...;
154	if (ecb_likely (some_condition)) ...;	349	if (ecb_expect_true (some_condition)) ...;
155		350
156	However, by using C<ecb_likely>, you tell the compiler that the condition	351	However, by using C<ecb_expect_true>, you tell the compiler that the
157	is likely to be true (and for C<ecb_unlikely>, that it is unlikely to be	352	condition is likely to be true (and for C<ecb_expect_false>, that it is
158	true).	353	unlikely to be true).
159		354
160	For example, when you check for a null pointer and expect this to be a	355	For example, when you check for a null pointer and expect this to be a
161	rare, exceptional, case, then use C<ecb_unlikely>:	356	rare, exceptional, case, then use C<ecb_expect_false>:
162		357
163	void my_free (void *ptr)	358	void my_free (void *ptr)
164	{	359	{
165	if (ecb_unlikely (ptr == 0))	360	if (ecb_expect_false (ptr == 0))
166	return;	361	return;
167	}	362	}
168		363
169	Consequent use of these functions to mark away exceptional cases or to	364	Consequent use of these functions to mark away exceptional cases or to
170	tell the compiler what the hot path through a function is can increase	365	tell the compiler what the hot path through a function is can increase
171	performance considerably.	366	performance considerably.
		367
		368	You might know these functions under the name C<likely> and C<unlikely>
		369	- while these are common aliases, we find that the expect name is easier
		370	to understand when quickly skimming code. If you wish, you can use
		371	C<ecb_likely> instead of C<ecb_expect_true> and C<ecb_unlikely> instead of
		372	C<ecb_expect_false> - these are simply aliases.
172		373
173	A very good example is in a function that reserves more space for some	374	A very good example is in a function that reserves more space for some
174	memory block (for example, inside an implementation of a string stream) -	375	memory block (for example, inside an implementation of a string stream) -
175	each time something is added, you have to check for a buffer overrun, but	376	each time something is added, you have to check for a buffer overrun, but
176	you expect that most checks will turn out to be false:	377	you expect that most checks will turn out to be false:
177		378
178	/* make sure we have "size" extra room in our buffer */	379	/* make sure we have "size" extra room in our buffer */
179	ecb_inline void	380	ecb_inline void
180	reserve (int size)	381	reserve (int size)
181	{	382	{
182	if (ecb_unlikely (current + size > end))	383	if (ecb_expect_false (current + size > end))
183	real_reserve_method (size); /* presumably noinline */	384	real_reserve_method (size); /* presumably noinline */
184	}	385	}
185		386
186	=item bool ecb_assume (cond)	387	=item bool ecb_assume (cond)
187		388
…		…
190		391
191	This can be used to teach the compiler about invariants or other	392	This can be used to teach the compiler about invariants or other
192	conditions that might improve code generation, but which are impossible to	393	conditions that might improve code generation, but which are impossible to
193	deduce form the code itself.	394	deduce form the code itself.
194		395
195	For example, the example reservation function from the C<ecb_unlikely>	396	For example, the example reservation function from the C<ecb_expect_false>
196	description could be written thus (only C<ecb_assume> was added):	397	description could be written thus (only C<ecb_assume> was added):
197		398
198	ecb_inline void	399	ecb_inline void
199	reserve (int size)	400	reserve (int size)
200	{	401	{
201	if (ecb_unlikely (current + size > end))	402	if (ecb_expect_false (current + size > end))
202	real_reserve_method (size); /* presumably noinline */	403	real_reserve_method (size); /* presumably noinline */
203		404
204	ecb_assume (current + size <= end);	405	ecb_assume (current + size <= end);
205	}	406	}
206		407
…		…
255	After processing the node, (part of) the next node might already be in	456	After processing the node, (part of) the next node might already be in
256	cache.	457	cache.
257		458
258	=back	459	=back
259		460
260	=head2 BIT FIDDLING / BITSTUFFS	461	=head2 BIT FIDDLING / BIT WIZARDRY
261		462
262	=over 4	463	=over 4
263		464
264	=item bool ecb_big_endian ()	465	=item bool ecb_big_endian ()
265		466
…		…
267		468
268	These two functions return true if the byte order is big endian	469	These two functions return true if the byte order is big endian
269	(most-significant byte first) or little endian (least-significant byte	470	(most-significant byte first) or little endian (least-significant byte
270	first) respectively.	471	first) respectively.
271		472
		473	On systems that are neither, their return values are unspecified.
		474
272	=item int ecb_ctz32 (uint32_t x)	475	=item int ecb_ctz32 (uint32_t x)
273		476
		477	=item int ecb_ctz64 (uint64_t x)
		478
274	Returns the index of the least significant bit set in C<x> (or	479	Returns the index of the least significant bit set in C<x> (or
275	equivalently the number of bits set to 0 before the least significant	480	equivalently the number of bits set to 0 before the least significant bit
276	bit set), starting from 0. If C<x> is 0 the result is undefined. A	481	set), starting from 0. If C<x> is 0 the result is undefined.
277	common use case is to compute the integer binary logarithm, i.e.,
278	floor(log2(n)). For example:
279		482
		483	For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.
		484
		485	For example:
		486
280	ecb_ctz32(3) = 0	487	ecb_ctz32 (3) = 0
281	ecb_ctz32(6) = 1	488	ecb_ctz32 (6) = 1
		489
		490	=item bool ecb_is_pot32 (uint32_t x)
		491
		492	=item bool ecb_is_pot64 (uint32_t x)
		493
		494	Return true iff C<x> is a power of two or C<x == 0>.
		495
		496	For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>.
		497
		498	=item int ecb_ld32 (uint32_t x)
		499
		500	=item int ecb_ld64 (uint64_t x)
		501
		502	Returns the index of the most significant bit set in C<x>, or the number
		503	of digits the number requires in binary (so that C<< 2**ld <= x <
		504	2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is
		505	to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for
		506	example to see how many bits a certain number requires to be encoded.
		507
		508	This function is similar to the "count leading zero bits" function, except
		509	that that one returns how many zero bits are "in front" of the number (in
		510	the given data type), while C<ecb_ld> returns how many bits the number
		511	itself requires.
		512
		513	For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.
282		514
283	=item int ecb_popcount32 (uint32_t x)	515	=item int ecb_popcount32 (uint32_t x)
284		516
		517	=item int ecb_popcount64 (uint64_t x)
		518
285	Returns the number of bits set to 1 in C<x>. For example:	519	Returns the number of bits set to 1 in C<x>.
286		520
		521	For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.
		522
		523	For example:
		524
287	ecb_popcount32(7) = 3	525	ecb_popcount32 (7) = 3
288	ecb_popcount32(255) = 8	526	ecb_popcount32 (255) = 8
		527
		528	=item uint8_t ecb_bitrev8 (uint8_t x)
		529
		530	=item uint16_t ecb_bitrev16 (uint16_t x)
		531
		532	=item uint32_t ecb_bitrev32 (uint32_t x)
		533
		534	Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1
		535	and so on.
		536
		537	Example:
		538
		539	ecb_bitrev8 (0xa7) = 0xea
		540	ecb_bitrev32 (0xffcc4411) = 0x882233ff
289		541
290	=item uint32_t ecb_bswap16 (uint32_t x)	542	=item uint32_t ecb_bswap16 (uint32_t x)
291		543
292	=item uint32_t ecb_bswap32 (uint32_t x)	544	=item uint32_t ecb_bswap32 (uint32_t x)
293		545
		546	=item uint64_t ecb_bswap64 (uint64_t x)
		547
294	These two functions return the value of the 16-bit (32-bit) variable	548	These functions return the value of the 16-bit (32-bit, 64-bit) value
295	C<x> after reversing the order of bytes.	549	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in
		550	C<ecb_bswap32>).
		551
		552	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
		553
		554	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
		555
		556	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
		557
		558	=item uint64_t ecb_rotl64 (uint64_t x, unsigned int count)
		559
		560	=item uint8_t ecb_rotr8 (uint8_t x, unsigned int count)
		561
		562	=item uint16_t ecb_rotr16 (uint16_t x, unsigned int count)
296		563
297	=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)	564	=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)
298		565
299	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	566	=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)
300		567
301	These two functions return the value of C<x> after shifting all the bits	568	These two families of functions return the value of C<x> after rotating
302	by C<count> positions to the right or left respectively.	569	all the bits by C<count> positions to the right (C<ecb_rotr>) or left
		570	(C<ecb_rotl>).
		571
		572	Current GCC versions understand these functions and usually compile them
		573	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
		574	x86).
303		575
304	=back	576	=back
305		577
306	=head2 ARITHMETIC	578	=head2 ARITHMETIC
307		579
308	=over 4	580	=over 4
309		581
310	=item x = ecb_mod (m, n)	582	=item x = ecb_mod (m, n)
311		583
312	Returns the positive remainder of the modulo operation between C<m> and	584	Returns C<m> modulo C<n>, which is the same as the positive remainder
		585	of the division operation between C<m> and C<n>, using floored
313	C<n>. Unlike the C moduloe operator C<%>, this function ensures that the	586	division. Unlike the C remainder operator C<%>, this function ensures that
314	return value is always positive).	587	the return value is always positive and that the two numbers I<m> and
		588	I<m' = m + i * n> result in the same value modulo I<n> - in other words,
		589	C<ecb_mod> implements the mathematical modulo operation, which is missing
		590	in the language.
315		591
316	C<n> must be strictly positive (i.e. C<< >1 >>), while C<m> must be	592	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be
317	negatable, that is, both C<m> and C<-m> must be representable in its	593	negatable, that is, both C<m> and C<-m> must be representable in its
318	type.	594	type (this typically excludes the minimum signed integer value, the same
		595	limitation as for C</> and C<%> in C).
		596
		597	Current GCC versions compile this into an efficient branchless sequence on
		598	almost all CPUs.
		599
		600	For example, when you want to rotate forward through the members of an
		601	array for increasing C<m> (which might be negative), then you should use
		602	C<ecb_mod>, as the C<%> operator might give either negative results, or
		603	change direction for negative values:
		604
		605	for (m = -100; m <= 100; ++m)
		606	int elem = myarray [ecb_mod (m, ecb_array_length (myarray))];
		607
		608	=item x = ecb_div_rd (val, div)
		609
		610	=item x = ecb_div_ru (val, div)
		611
		612	Returns C<val> divided by C<div> rounded down or up, respectively.
		613	C<val> and C<div> must have integer types and C<div> must be strictly
		614	positive. Note that these functions are implemented with macros in C
		615	and with function templates in C++.
319		616
320	=back	617	=back
321		618
322	=head2 UTILITY	619	=head2 UTILITY
323		620
324	=over 4	621	=over 4
325		622
326	=item element_count = ecb_array_length (name) [MACRO]	623	=item element_count = ecb_array_length (name)
327		624
328	Returns the number of elements in the array C<name>. For example:	625	Returns the number of elements in the array C<name>. For example:
329		626
330	int primes[] = { 2, 3, 5, 7, 11 };	627	int primes[] = { 2, 3, 5, 7, 11 };
331	int sum = 0;	628	int sum = 0;
…		…
333	for (i = 0; i < ecb_array_length (primes); i++)	630	for (i = 0; i < ecb_array_length (primes); i++)
334	sum += primes [i];	631	sum += primes [i];
335		632
336	=back	633	=back
337		634
		635	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF
338		636
		637	These symbols need to be defined before including F<ecb.h> the first time.
		638
		639	=over 4
		640
		641	=item ECB_NO_THRADS
		642
		643	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
		645	completely removed, leading to more efficient code and fewer dependencies.
		646
		647	Setting this symbol to a true value implies C<ECB_NO_SMP>.
		648
		649	=item ECB_NO_SMP
		650
		651	The weaker version of C<ECB_NO_THREADS> - if F<ecb.h> is used from
		652	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
		654	on), then this symbol can be defined, leading to more efficient code and
		655	fewer dependencies.
		656
		657	=back
		658
		659

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Comparing libecb/ecb.pod (file contents): Revision 1.14 by root, Thu May 26 23:23:08 2011 UTC vs. Revision 1.45 by root, Tue May 29 14:35:43 2012 UTC

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Comparing libecb/ecb.pod (file contents):
Revision 1.14 by root, Thu May 26 23:23:08 2011 UTC vs.
Revision 1.45 by root, Tue May 29 14:35:43 2012 UTC