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

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.27 by root, Wed Jun 1 01:29:36 2011 UTC vs.
Revision 1.57 by root, Thu Oct 16 14:47:20 2014 UTC

…		…
54	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
55	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
56	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
57	refers to any kind of boolean value, not a specific type.	57	refers to any kind of boolean value, not a specific type.
58		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
		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	For C<ptrdiff_t> and C<size_t> use C<stddef.h>.
		72
		73	=head2 LANGUAGE/COMPILER VERSIONS
		74
		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
		77	ensure it's either C<0> or C<1> if you need that).
		78
		79	=over 4
		80
		81	=item ECB_C
		82
		83	True if the implementation defines the C<__STDC__> macro to a true value,
		84	while not claiming to be C++.
		85
		86	=item ECB_C99
		87
		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).
		93
		94	=item ECB_C11
		95
		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++.
		98
		99	=item ECB_CPP
		100
		101	True if the implementation defines the C<__cplusplus__> macro to a true
		102	value, which is typically true for C++ compilers.
		103
		104	=item ECB_CPP11
		105
		106	True if the implementation claims to be compliant to ISO/IEC 14882:2011
		107	(C++11) or any later version.
		108
		109	=item ECB_GCC_VERSION (major, minor)
		110
		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
		113	higher.
		114
		115	This macro tries to return false on compilers that claim to be GCC
		116	compatible but aren't.
		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
		166	=back
		167
59	=head2 GCC ATTRIBUTES	168	=head2 GCC ATTRIBUTES
60		169
61	A major part of libecb deals with GCC attributes. These are additional	170	A major part of libecb deals with GCC attributes. These are additional
62	attributes that you can assign to functions, variables and sometimes even	171	attributes that you can assign to functions, variables and sometimes even
63	types - much like C<const> or C<volatile> in C.	172	types - much like C<const> or C<volatile> in C.
…		…
76		185
77	=over 4	186	=over 4
78		187
79	=item ecb_attribute ((attrs...))	188	=item ecb_attribute ((attrs...))
80		189
81	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to	190	A simple wrapper that expands to C<__attribute__((attrs))> on GCC 3.1+ and
82	nothing on other compilers, so the effect is that only GCC sees these.	191	Clang 2.8+, and to nothing on other compilers, so the effect is that only
		192	GCC and Clang see these.
83		193
84	Example: use the C<deprecated> attribute on a function.	194	Example: use the C<deprecated> attribute on a function.
85		195
86	ecb_attribute((__deprecated__)) void	196	ecb_attribute((__deprecated__)) void
87	do_not_use_me_anymore (void);	197	do_not_use_me_anymore (void);
…		…
101	#else	211	#else
102	return 0;	212	return 0;
103	#endif	213	#endif
104	}	214	}
105		215
		216	=item ecb_deprecated
		217
		218	Similar to C<ecb_unused>, but marks a function, variable or type as
		219	deprecated. This makes some compilers warn when the type is used.
		220
		221	=item ecb_inline
		222
		223	This is not actually an attribute, but you use it like one. It expands
		224	either to C<static inline> or to just C<static>, if inline isn't
		225	supported. It should be used to declare functions that should be inlined,
		226	for code size or speed reasons.
		227
		228	Example: inline this function, it surely will reduce codesize.
		229
		230	ecb_inline int
		231	negmul (int a, int b)
		232	{
		233	return - (a * b);
		234	}
		235
106	=item ecb_noinline	236	=item ecb_noinline
107		237
108	Prevent a function from being inlined - it might be optimised away, but	238	Prevent a function from being inlined - it might be optimised away, but
109	not inlined into other functions. This is useful if you know your function	239	not inlined into other functions. This is useful if you know your function
110	is rarely called and large enough for inlining not to be helpful.	240	is rarely called and large enough for inlining not to be helpful.
…		…
123	}	253	}
124		254
125	In this case, the compiler would probably be smart enough to deduce it on	255	In this case, the compiler would probably be smart enough to deduce it on
126	its own, so this is mainly useful for declarations.	256	its own, so this is mainly useful for declarations.
127		257
		258	=item ecb_restrict
		259
		260	Expands to the C<restrict> keyword or equivalent on compilers that support
		261	them, and to nothing on others. Must be specified on a pointer type or
		262	an array index to indicate that the memory doesn't alias with any other
		263	restricted pointer in the same scope.
		264
		265	Example: multiply a vector, and allow the compiler to parallelise the
		266	loop, because it knows it doesn't overwrite input values.
		267
		268	void
		269	multiply (float *ecb_restrict src,
		270	float *ecb_restrict dst,
		271	int len, float factor)
		272	{
		273	int i;
		274
		275	for (i = 0; i < len; ++i)
		276	dst [i] = src [i] * factor;
		277	}
		278
128	=item ecb_const	279	=item ecb_const
129		280
130	Declares that the function only depends on the values of its arguments,	281	Declares that the function only depends on the values of its arguments,
131	much like a mathematical function. It specifically does not read or write	282	much like a mathematical function. It specifically does not read or write
132	any memory any arguments might point to, global variables, or call any	283	any memory any arguments might point to, global variables, or call any
…		…
192	functions only called in exceptional or rare cases.	343	functions only called in exceptional or rare cases.
193		344
194	=item ecb_artificial	345	=item ecb_artificial
195		346
196	Declares the function as "artificial", in this case meaning that this	347	Declares the function as "artificial", in this case meaning that this
197	function is not really mean to be a function, but more like an accessor	348	function is not really meant to be a function, but more like an accessor
198	- many methods in C++ classes are mere accessor functions, and having a	349	- many methods in C++ classes are mere accessor functions, and having a
199	crash reported in such a method, or single-stepping through them, is not	350	crash reported in such a method, or single-stepping through them, is not
200	usually so helpful, especially when it's inlined to just a few instructions.	351	usually so helpful, especially when it's inlined to just a few instructions.
201		352
202	Marking them as artificial will instruct the debugger about just this,	353	Marking them as artificial will instruct the debugger about just this,
…		…
381	After processing the node, (part of) the next node might already be in	532	After processing the node, (part of) the next node might already be in
382	cache.	533	cache.
383		534
384	=back	535	=back
385		536
386	=head2 BIT FIDDLING / BITSTUFFS	537	=head2 BIT FIDDLING / BIT WIZARDRY
387		538
388	=over 4	539	=over 4
389		540
390	=item bool ecb_big_endian ()	541	=item bool ecb_big_endian ()
391		542
…		…
397		548
398	On systems that are neither, their return values are unspecified.	549	On systems that are neither, their return values are unspecified.
399		550
400	=item int ecb_ctz32 (uint32_t x)	551	=item int ecb_ctz32 (uint32_t x)
401		552
		553	=item int ecb_ctz64 (uint64_t x)
		554
402	Returns the index of the least significant bit set in C<x> (or	555	Returns the index of the least significant bit set in C<x> (or
403	equivalently the number of bits set to 0 before the least significant bit	556	equivalently the number of bits set to 0 before the least significant bit
404	set), starting from 0. If C<x> is 0 the result is undefined. A common use	557	set), starting from 0. If C<x> is 0 the result is undefined.
405	case is to compute the integer binary logarithm, i.e., C<floor (log2	558
		559	For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.
		560
406	(n))>. For example:	561	For example:
407		562
408	ecb_ctz32 (3) = 0	563	ecb_ctz32 (3) = 0
409	ecb_ctz32 (6) = 1	564	ecb_ctz32 (6) = 1
410		565
		566	=item bool ecb_is_pot32 (uint32_t x)
		567
		568	=item bool ecb_is_pot64 (uint32_t x)
		569
		570	Return true iff C<x> is a power of two or C<x == 0>.
		571
		572	For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>.
		573
		574	=item int ecb_ld32 (uint32_t x)
		575
		576	=item int ecb_ld64 (uint64_t x)
		577
		578	Returns the index of the most significant bit set in C<x>, or the number
		579	of digits the number requires in binary (so that C<< 2**ld <= x <
		580	2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is
		581	to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for
		582	example to see how many bits a certain number requires to be encoded.
		583
		584	This function is similar to the "count leading zero bits" function, except
		585	that that one returns how many zero bits are "in front" of the number (in
		586	the given data type), while C<ecb_ld> returns how many bits the number
		587	itself requires.
		588
		589	For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.
		590
411	=item int ecb_popcount32 (uint32_t x)	591	=item int ecb_popcount32 (uint32_t x)
412		592
		593	=item int ecb_popcount64 (uint64_t x)
		594
413	Returns the number of bits set to 1 in C<x>. For example:	595	Returns the number of bits set to 1 in C<x>.
		596
		597	For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.
		598
		599	For example:
414		600
415	ecb_popcount32 (7) = 3	601	ecb_popcount32 (7) = 3
416	ecb_popcount32 (255) = 8	602	ecb_popcount32 (255) = 8
417		603
		604	=item uint8_t ecb_bitrev8 (uint8_t x)
		605
		606	=item uint16_t ecb_bitrev16 (uint16_t x)
		607
		608	=item uint32_t ecb_bitrev32 (uint32_t x)
		609
		610	Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1
		611	and so on.
		612
		613	Example:
		614
		615	ecb_bitrev8 (0xa7) = 0xea
		616	ecb_bitrev32 (0xffcc4411) = 0x882233ff
		617
418	=item uint32_t ecb_bswap16 (uint32_t x)	618	=item uint32_t ecb_bswap16 (uint32_t x)
419		619
420	=item uint32_t ecb_bswap32 (uint32_t x)	620	=item uint32_t ecb_bswap32 (uint32_t x)
421		621
		622	=item uint64_t ecb_bswap64 (uint64_t x)
		623
422	These two functions return the value of the 16-bit (32-bit) value C<x>	624	These functions return the value of the 16-bit (32-bit, 64-bit) value
423	after reversing the order of bytes (0x11223344 becomes 0x44332211).	625	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in
		626	C<ecb_bswap32>).
		627
		628	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
		629
		630	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
		631
		632	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
		633
		634	=item uint64_t ecb_rotl64 (uint64_t x, unsigned int count)
		635
		636	=item uint8_t ecb_rotr8 (uint8_t x, unsigned int count)
		637
		638	=item uint16_t ecb_rotr16 (uint16_t x, unsigned int count)
424		639
425	=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)	640	=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)
426		641
427	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	642	=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)
428		643
429	These two functions return the value of C<x> after rotating all the bits	644	These two families of functions return the value of C<x> after rotating
430	by C<count> positions to the right or left respectively.	645	all the bits by C<count> positions to the right (C<ecb_rotr>) or left
		646	(C<ecb_rotl>).
431		647
432	Current GCC versions understand these functions and usually compile them	648	Current GCC versions understand these functions and usually compile them
433	to "optimal" code (e.g. a single C<roll> on x86).	649	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
		650	x86).
		651
		652	=back
		653
		654	=head2 FLOATING POINT FIDDLING
		655
		656	=over 4
		657
		658	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
		659
		660	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
		661
		662	These functions each take an argument in the native C<float> or C<double>
		663	type and return the IEEE 754 bit representation of it.
		664
		665	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
		666	will be the most significant bit, followed by exponent and mantissa.
		667
		668	This function should work even when the native floating point format isn't
		669	IEEE compliant, of course at a speed and code size penalty, and of course
		670	also within reasonable limits (it tries to convert NaNs, infinities and
		671	denormals, but will likely convert negative zero to positive zero).
		672
		673	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		674	be able to optimise away this function completely.
		675
		676	These functions can be helpful when serialising floats to the network - you
		677	can serialise the return value like a normal uint32_t/uint64_t.
		678
		679	Another use for these functions is to manipulate floating point values
		680	directly.
		681
		682	Silly example: toggle the sign bit of a float.
		683
		684	/* On gcc-4.7 on amd64, */
		685	/* this results in a single add instruction to toggle the bit, and 4 extra */
		686	/* instructions to move the float value to an integer register and back. */
		687
		688	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
		689
		690	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
		691
		692	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]
		693
		694	The reverse operation of the previos function - takes the bit representation
		695	of an IEEE binary32 or binary64 number and converts it to the native C<float>
		696	or C<double> format.
		697
		698	This function should work even when the native floating point format isn't
		699	IEEE compliant, of course at a speed and code size penalty, and of course
		700	also within reasonable limits (it tries to convert normals and denormals,
		701	and might be lucky for infinities, and with extraordinary luck, also for
		702	negative zero).
		703
		704	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		705	be able to optimise away this function completely.
434		706
435	=back	707	=back
436		708
437	=head2 ARITHMETIC	709	=head2 ARITHMETIC
438		710
…		…
448	C<ecb_mod> implements the mathematical modulo operation, which is missing	720	C<ecb_mod> implements the mathematical modulo operation, which is missing
449	in the language.	721	in the language.
450		722
451	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be	723	C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be
452	negatable, that is, both C<m> and C<-m> must be representable in its	724	negatable, that is, both C<m> and C<-m> must be representable in its
453	type (this typically includes the minimum signed integer value, the same	725	type (this typically excludes the minimum signed integer value, the same
454	limitation as for C</> and C<%> in C).	726	limitation as for C</> and C<%> in C).
455		727
456	Current GCC versions compile this into an efficient branchless sequence on	728	Current GCC versions compile this into an efficient branchless sequence on
457	many systems.	729	almost all CPUs.
458		730
459	For example, when you want to rotate forward through the members of an	731	For example, when you want to rotate forward through the members of an
460	array for increasing C<m> (which might be negative), then you should use	732	array for increasing C<m> (which might be negative), then you should use
461	C<ecb_mod>, as the C<%> operator might give either negative results, or	733	C<ecb_mod>, as the C<%> operator might give either negative results, or
462	change direction for negative values:	734	change direction for negative values:
463		735
464	for (m = -100; m <= 100; ++m)	736	for (m = -100; m <= 100; ++m)
465	int elem = myarray [ecb_mod (m, ecb_array_length (myarray))];	737	int elem = myarray [ecb_mod (m, ecb_array_length (myarray))];
466		738
		739	=item x = ecb_div_rd (val, div)
		740
		741	=item x = ecb_div_ru (val, div)
		742
		743	Returns C<val> divided by C<div> rounded down or up, respectively.
		744	C<val> and C<div> must have integer types and C<div> must be strictly
		745	positive. Note that these functions are implemented with macros in C
		746	and with function templates in C++.
		747
467	=back	748	=back
468		749
469	=head2 UTILITY	750	=head2 UTILITY
470		751
471	=over 4	752	=over 4
…		…
480	for (i = 0; i < ecb_array_length (primes); i++)	761	for (i = 0; i < ecb_array_length (primes); i++)
481	sum += primes [i];	762	sum += primes [i];
482		763
483	=back	764	=back
484		765
		766	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF
485		767
		768	These symbols need to be defined before including F<ecb.h> the first time.
		769
		770	=over 4
		771
		772	=item ECB_NO_THREADS
		773
		774	If F<ecb.h> is never used from multiple threads, then this symbol can
		775	be defined, in which case memory fences (and similar constructs) are
		776	completely removed, leading to more efficient code and fewer dependencies.
		777
		778	Setting this symbol to a true value implies C<ECB_NO_SMP>.
		779
		780	=item ECB_NO_SMP
		781
		782	The weaker version of C<ECB_NO_THREADS> - if F<ecb.h> is used from
		783	multiple threads, but never concurrently (e.g. if the system the program
		784	runs on has only a single CPU with a single core, no hyperthreading and so
		785	on), then this symbol can be defined, leading to more efficient code and
		786	fewer dependencies.
		787
		788	=item ECB_NO_LIBM
		789
		790	When defined to C<1>, do not export any functions that might introduce
		791	dependencies on the math library (usually called F<-lm>) - these are
		792	marked with [-UECB_NO_LIBM].
		793
		794	=back
		795
		796

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Comparing cvsroot/libecb/ecb.pod (file contents): Revision 1.27 by root, Wed Jun 1 01:29:36 2011 UTC vs. Revision 1.57 by root, Thu Oct 16 14:47:20 2014 UTC

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Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.27 by root, Wed Jun 1 01:29:36 2011 UTC vs.
Revision 1.57 by root, Thu Oct 16 14:47:20 2014 UTC