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

Comparing libecb/ecb.pod (file contents):
Revision 1.32 by sf-exg, Fri Jun 17 15:55:41 2011 UTC vs.
Revision 1.56 by root, Mon Jun 9 17:31:57 2014 UTC

…		…
53	C<uint32_t>, then the corresponding function works only with that type. If	53	C<uint32_t>, then the corresponding function works only with that type. If
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
		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
58		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
…		…
101	#else	210	#else
102	return 0;	211	return 0;
103	#endif	212	#endif
104	}	213	}
105		214
		215	=item ecb_deprecated
		216
		217	Similar to C<ecb_unused>, but marks a function, variable or type as
		218	deprecated. This makes some compilers warn when the type is used.
		219
106	=item ecb_inline	220	=item ecb_inline
107		221
108	This is not actually an attribute, but you use it like one. It expands	222	This is not actually an attribute, but you use it like one. It expands
109	either to C<static inline> or to just C<static>, if inline isn't	223	either to C<static inline> or to just C<static>, if inline isn't
110	supported. It should be used to declare functions that should be inlined,	224	supported. It should be used to declare functions that should be inlined,
…		…
138	}	252	}
139		253
140	In this case, the compiler would probably be smart enough to deduce it on	254	In this case, the compiler would probably be smart enough to deduce it on
141	its own, so this is mainly useful for declarations.	255	its own, so this is mainly useful for declarations.
142		256
		257	=item ecb_restrict
		258
		259	Expands to the C<restrict> keyword or equivalent on compilers that support
		260	them, and to nothing on others. Must be specified on a pointer type or
		261	an array index to indicate that the memory doesn't alias with any other
		262	restricted pointer in the same scope.
		263
		264	Example: multiply a vector, and allow the compiler to parallelise the
		265	loop, because it knows it doesn't overwrite input values.
		266
		267	void
		268	multiply (float *ecb_restrict src,
		269	float *ecb_restrict dst,
		270	int len, float factor)
		271	{
		272	int i;
		273
		274	for (i = 0; i < len; ++i)
		275	dst [i] = src [i] * factor;
		276	}
		277
143	=item ecb_const	278	=item ecb_const
144		279
145	Declares that the function only depends on the values of its arguments,	280	Declares that the function only depends on the values of its arguments,
146	much like a mathematical function. It specifically does not read or write	281	much like a mathematical function. It specifically does not read or write
147	any memory any arguments might point to, global variables, or call any	282	any memory any arguments might point to, global variables, or call any
…		…
207	functions only called in exceptional or rare cases.	342	functions only called in exceptional or rare cases.
208		343
209	=item ecb_artificial	344	=item ecb_artificial
210		345
211	Declares the function as "artificial", in this case meaning that this	346	Declares the function as "artificial", in this case meaning that this
212	function is not really mean to be a function, but more like an accessor	347	function is not really meant to be a function, but more like an accessor
213	- many methods in C++ classes are mere accessor functions, and having a	348	- many methods in C++ classes are mere accessor functions, and having a
214	crash reported in such a method, or single-stepping through them, is not	349	crash reported in such a method, or single-stepping through them, is not
215	usually so helpful, especially when it's inlined to just a few instructions.	350	usually so helpful, especially when it's inlined to just a few instructions.
216		351
217	Marking them as artificial will instruct the debugger about just this,	352	Marking them as artificial will instruct the debugger about just this,
…		…
396	After processing the node, (part of) the next node might already be in	531	After processing the node, (part of) the next node might already be in
397	cache.	532	cache.
398		533
399	=back	534	=back
400		535
401	=head2 BIT FIDDLING / BITSTUFFS	536	=head2 BIT FIDDLING / BIT WIZARDRY
402		537
403	=over 4	538	=over 4
404		539
405	=item bool ecb_big_endian ()	540	=item bool ecb_big_endian ()
406		541
…		…
412		547
413	On systems that are neither, their return values are unspecified.	548	On systems that are neither, their return values are unspecified.
414		549
415	=item int ecb_ctz32 (uint32_t x)	550	=item int ecb_ctz32 (uint32_t x)
416		551
		552	=item int ecb_ctz64 (uint64_t x)
		553
417	Returns the index of the least significant bit set in C<x> (or	554	Returns the index of the least significant bit set in C<x> (or
418	equivalently the number of bits set to 0 before the least significant bit	555	equivalently the number of bits set to 0 before the least significant bit
419	set), starting from 0. If C<x> is 0 the result is undefined. For example:	556	set), starting from 0. If C<x> is 0 the result is undefined.
		557
		558	For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.
		559
		560	For example:
420		561
421	ecb_ctz32 (3) = 0	562	ecb_ctz32 (3) = 0
422	ecb_ctz32 (6) = 1	563	ecb_ctz32 (6) = 1
423		564
		565	=item bool ecb_is_pot32 (uint32_t x)
		566
		567	=item bool ecb_is_pot64 (uint32_t x)
		568
		569	Return true iff C<x> is a power of two or C<x == 0>.
		570
		571	For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>.
		572
		573	=item int ecb_ld32 (uint32_t x)
		574
		575	=item int ecb_ld64 (uint64_t x)
		576
		577	Returns the index of the most significant bit set in C<x>, or the number
		578	of digits the number requires in binary (so that C<< 2**ld <= x <
		579	2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is
		580	to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for
		581	example to see how many bits a certain number requires to be encoded.
		582
		583	This function is similar to the "count leading zero bits" function, except
		584	that that one returns how many zero bits are "in front" of the number (in
		585	the given data type), while C<ecb_ld> returns how many bits the number
		586	itself requires.
		587
		588	For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.
		589
424	=item int ecb_popcount32 (uint32_t x)	590	=item int ecb_popcount32 (uint32_t x)
425		591
		592	=item int ecb_popcount64 (uint64_t x)
		593
426	Returns the number of bits set to 1 in C<x>. For example:	594	Returns the number of bits set to 1 in C<x>.
		595
		596	For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.
		597
		598	For example:
427		599
428	ecb_popcount32 (7) = 3	600	ecb_popcount32 (7) = 3
429	ecb_popcount32 (255) = 8	601	ecb_popcount32 (255) = 8
430		602
		603	=item uint8_t ecb_bitrev8 (uint8_t x)
		604
		605	=item uint16_t ecb_bitrev16 (uint16_t x)
		606
		607	=item uint32_t ecb_bitrev32 (uint32_t x)
		608
		609	Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1
		610	and so on.
		611
		612	Example:
		613
		614	ecb_bitrev8 (0xa7) = 0xea
		615	ecb_bitrev32 (0xffcc4411) = 0x882233ff
		616
431	=item uint32_t ecb_bswap16 (uint32_t x)	617	=item uint32_t ecb_bswap16 (uint32_t x)
432		618
433	=item uint32_t ecb_bswap32 (uint32_t x)	619	=item uint32_t ecb_bswap32 (uint32_t x)
434		620
		621	=item uint64_t ecb_bswap64 (uint64_t x)
		622
435	These two functions return the value of the 16-bit (32-bit) value C<x>	623	These functions return the value of the 16-bit (32-bit, 64-bit) value
436	after reversing the order of bytes (0x11223344 becomes 0x44332211).	624	C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in
		625	C<ecb_bswap32>).
		626
		627	=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
		628
		629	=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
		630
		631	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
		632
		633	=item uint64_t ecb_rotl64 (uint64_t x, unsigned int count)
		634
		635	=item uint8_t ecb_rotr8 (uint8_t x, unsigned int count)
		636
		637	=item uint16_t ecb_rotr16 (uint16_t x, unsigned int count)
437		638
438	=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)	639	=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)
439		640
440	=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)	641	=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)
441		642
442	These two functions return the value of C<x> after rotating all the bits	643	These two families of functions return the value of C<x> after rotating
443	by C<count> positions to the right or left respectively.	644	all the bits by C<count> positions to the right (C<ecb_rotr>) or left
		645	(C<ecb_rotl>).
444		646
445	Current GCC versions understand these functions and usually compile them	647	Current GCC versions understand these functions and usually compile them
446	to "optimal" code (e.g. a single C<roll> on x86).	648	to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
		649	x86).
		650
		651	=back
		652
		653	=head2 FLOATING POINT FIDDLING
		654
		655	=over 4
		656
		657	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
		658
		659	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
		660
		661	These functions each take an argument in the native C<float> or C<double>
		662	type and return the IEEE 754 bit representation of it.
		663
		664	The bit representation is just as IEEE 754 defines it, i.e. the sign bit
		665	will be the most significant bit, followed by exponent and mantissa.
		666
		667	This function should work even when the native floating point format isn't
		668	IEEE compliant, of course at a speed and code size penalty, and of course
		669	also within reasonable limits (it tries to convert NaNs, infinities and
		670	denormals, but will likely convert negative zero to positive zero).
		671
		672	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		673	be able to optimise away this function completely.
		674
		675	These functions can be helpful when serialising floats to the network - you
		676	can serialise the return value like a normal uint32_t/uint64_t.
		677
		678	Another use for these functions is to manipulate floating point values
		679	directly.
		680
		681	Silly example: toggle the sign bit of a float.
		682
		683	/* On gcc-4.7 on amd64, */
		684	/* this results in a single add instruction to toggle the bit, and 4 extra */
		685	/* instructions to move the float value to an integer register and back. */
		686
		687	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
		688
		689	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
		690
		691	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]
		692
		693	The reverse operation of the previos function - takes the bit representation
		694	of an IEEE binary32 or binary64 number and converts it to the native C<float>
		695	or C<double> format.
		696
		697	This function should work even when the native floating point format isn't
		698	IEEE compliant, of course at a speed and code size penalty, and of course
		699	also within reasonable limits (it tries to convert normals and denormals,
		700	and might be lucky for infinities, and with extraordinary luck, also for
		701	negative zero).
		702
		703	On all modern platforms (where C<ECB_STDFP> is true), the compiler should
		704	be able to optimise away this function completely.
447		705
448	=back	706	=back
449		707
450	=head2 ARITHMETIC	708	=head2 ARITHMETIC
451		709
…		…
475	change direction for negative values:	733	change direction for negative values:
476		734
477	for (m = -100; m <= 100; ++m)	735	for (m = -100; m <= 100; ++m)
478	int elem = myarray [ecb_mod (m, ecb_array_length (myarray))];	736	int elem = myarray [ecb_mod (m, ecb_array_length (myarray))];
479		737
		738	=item x = ecb_div_rd (val, div)
		739
		740	=item x = ecb_div_ru (val, div)
		741
		742	Returns C<val> divided by C<div> rounded down or up, respectively.
		743	C<val> and C<div> must have integer types and C<div> must be strictly
		744	positive. Note that these functions are implemented with macros in C
		745	and with function templates in C++.
		746
480	=back	747	=back
481		748
482	=head2 UTILITY	749	=head2 UTILITY
483		750
484	=over 4	751	=over 4
…		…
493	for (i = 0; i < ecb_array_length (primes); i++)	760	for (i = 0; i < ecb_array_length (primes); i++)
494	sum += primes [i];	761	sum += primes [i];
495		762
496	=back	763	=back
497		764
		765	=head2 SYMBOLS GOVERNING COMPILATION OF ECB.H ITSELF
498		766
		767	These symbols need to be defined before including F<ecb.h> the first time.
		768
		769	=over 4
		770
		771	=item ECB_NO_THREADS
		772
		773	If F<ecb.h> is never used from multiple threads, then this symbol can
		774	be defined, in which case memory fences (and similar constructs) are
		775	completely removed, leading to more efficient code and fewer dependencies.
		776
		777	Setting this symbol to a true value implies C<ECB_NO_SMP>.
		778
		779	=item ECB_NO_SMP
		780
		781	The weaker version of C<ECB_NO_THREADS> - if F<ecb.h> is used from
		782	multiple threads, but never concurrently (e.g. if the system the program
		783	runs on has only a single CPU with a single core, no hyperthreading and so
		784	on), then this symbol can be defined, leading to more efficient code and
		785	fewer dependencies.
		786
		787	=item ECB_NO_LIBM
		788
		789	When defined to C<1>, do not export any functions that might introduce
		790	dependencies on the math library (usually called F<-lm>) - these are
		791	marked with [-UECB_NO_LIBM].
		792
		793	=back
		794
		795

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Comparing libecb/ecb.pod (file contents): Revision 1.32 by sf-exg, Fri Jun 17 15:55:41 2011 UTC vs. Revision 1.56 by root, Mon Jun 9 17:31:57 2014 UTC

Diff Legend

Comparing libecb/ecb.pod (file contents):
Revision 1.32 by sf-exg, Fri Jun 17 15:55:41 2011 UTC vs.
Revision 1.56 by root, Mon Jun 9 17:31:57 2014 UTC