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Comparing libecb/ecb.pod (file contents):
Revision 1.29 by root, Fri Jun 10 12:20:14 2011 UTC vs.
Revision 1.34 by root, Fri Jun 17 21:16:12 2011 UTC

… …
101 #else 101 #else
102 return 0; 102 return 0;
103 #endif 103 #endif
104 } 104 }
105 105
106=item ECB_INLINE 106=item ecb_inline
107 107
108This is not actually an attribute, but you use it like one. It expands 108This is not actually an attribute, but you use it like one. It expands
109either to C<static inline> or to just C<static>, if inline isn't 109either to C<static inline> or to just C<static>, if inline isn't
110supported. It should be used to declare functions that should be inlined, 110supported. It should be used to declare functions that should be inlined,
111for code size or speed reasons. 111for code size or speed reasons.
112 112
113Example: inline this function, it surely will reduce codesize. 113Example: inline this function, it surely will reduce codesize.
114 114
115 ECB_INLINE int 115 ecb_inline int
116 negmul (int a, int b) 116 negmul (int a, int b)
117 { 117 {
118 return - (a * b); 118 return - (a * b);
119 } 119 }
120 120
… …
414 414
415=item int ecb_ctz32 (uint32_t x) 415=item int ecb_ctz32 (uint32_t x)
416 416
417Returns the index of the least significant bit set in C<x> (or 417Returns the index of the least significant bit set in C<x> (or
418equivalently the number of bits set to 0 before the least significant bit 418equivalently the number of bits set to 0 before the least significant bit
419set), starting from 0. If C<x> is 0 the result is undefined. A common use 419set), starting from 0. If C<x> is 0 the result is undefined. For example:
420case is to compute the integer binary logarithm, i.e., C<floor (log2
421(n))>. For example:
422 420
423 ecb_ctz32 (3) = 0 421 ecb_ctz32 (3) = 0
424 ecb_ctz32 (6) = 1 422 ecb_ctz32 (6) = 1
425 423
426=item int ecb_popcount32 (uint32_t x) 424=item int ecb_popcount32 (uint32_t x)
… …
432 430
433=item uint32_t ecb_bswap16 (uint32_t x) 431=item uint32_t ecb_bswap16 (uint32_t x)
434 432
435=item uint32_t ecb_bswap32 (uint32_t x) 433=item uint32_t ecb_bswap32 (uint32_t x)
436 434
435=item uint64_t ecb_bswap64 (uint64_t x)
436
437These two functions return the value of the 16-bit (32-bit) value C<x> 437These functions return the value of the 16-bit (32-bit, 64-bit) value
438after reversing the order of bytes (0x11223344 becomes 0x44332211). 438C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in
439C<ecb_bswap32>).
440
441=item uint8_t ecb_rotl8 (uint8_t x, unsigned int count)
442
443=item uint16_t ecb_rotl16 (uint16_t x, unsigned int count)
444
445=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count)
446
447=item uint64_t ecb_rotl64 (uint64_t x, unsigned int count)
448
449=item uint8_t ecb_rotr8 (uint8_t x, unsigned int count)
450
451=item uint16_t ecb_rotr16 (uint16_t x, unsigned int count)
439 452
440=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count) 453=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count)
441 454
442=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) 455=item uint64_t ecb_rotr64 (uint64_t x, unsigned int count)
443 456
444These two functions return the value of C<x> after rotating all the bits 457These two families of functions return the value of C<x> after rotating
445by C<count> positions to the right or left respectively. 458all the bits by C<count> positions to the right (C<ecb_rotr>) or left
459(C<ecb_rotl>).
446 460
447Current GCC versions understand these functions and usually compile them 461Current GCC versions understand these functions and usually compile them
448to "optimal" code (e.g. a single C<roll> on x86). 462to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on
463x86).
449 464
450=back 465=back
451 466
452=head2 ARITHMETIC 467=head2 ARITHMETIC
453 468
… …
463C<ecb_mod> implements the mathematical modulo operation, which is missing 478C<ecb_mod> implements the mathematical modulo operation, which is missing
464in the language. 479in the language.
465 480
466C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be 481C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be
467negatable, that is, both C<m> and C<-m> must be representable in its 482negatable, that is, both C<m> and C<-m> must be representable in its
468type (this typically includes the minimum signed integer value, the same 483type (this typically excludes the minimum signed integer value, the same
469limitation as for C</> and C<%> in C). 484limitation as for C</> and C<%> in C).
470 485
471Current GCC versions compile this into an efficient branchless sequence on 486Current GCC versions compile this into an efficient branchless sequence on
472almost all CPUs. 487almost all CPUs.
473 488

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