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Revision 1.35 by root, Fri Jun 17 21:38:31 2011 UTC vs.
Revision 1.41 by root, Mon May 28 08:40:25 2012 UTC

… …
53C<uint32_t>, then the corresponding function works only with that type. If 53C<uint32_t>, then the corresponding function works only with that type. If
54only a generic name is used (C<expr>, C<cond>, C<value> and so on), then 54only a generic name is used (C<expr>, C<cond>, C<value> and so on), then
55the corresponding function relies on C to implement the correct types, and 55the corresponding function relies on C to implement the correct types, and
56is usually implemented as a macro. Specifically, a "bool" in this manual 56is usually implemented as a macro. Specifically, a "bool" in this manual
57refers to any kind of boolean value, not a specific type. 57refers to any kind of boolean value, not a specific type.
58
59=head2 TYPES / TYPE SUPPORT
60
61ecb.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
67The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this
68platform (currently C<4> or C<8>).
58 69
59=head2 GCC ATTRIBUTES 70=head2 GCC ATTRIBUTES
60 71
61A major part of libecb deals with GCC attributes. These are additional 72A major part of libecb deals with GCC attributes. These are additional
62attributes that you can assign to functions, variables and sometimes even 73attributes that you can assign to functions, variables and sometimes even
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396After processing the node, (part of) the next node might already be in 407After processing the node, (part of) the next node might already be in
397cache. 408cache.
398 409
399=back 410=back
400 411
401=head2 BIT FIDDLING / BITSTUFFS 412=head2 BIT FIDDLING / BIT WIZARDRY
402 413
403=over 4 414=over 4
404 415
405=item bool ecb_big_endian () 416=item bool ecb_big_endian ()
406 417
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418 429
419Returns the index of the least significant bit set in C<x> (or 430Returns the index of the least significant bit set in C<x> (or
420equivalently the number of bits set to 0 before the least significant bit 431equivalently the number of bits set to 0 before the least significant bit
421set), starting from 0. If C<x> is 0 the result is undefined. 432set), starting from 0. If C<x> is 0 the result is undefined.
422 433
434For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>.
435
423For example: 436For example:
424 437
425 ecb_ctz32 (3) = 0 438 ecb_ctz32 (3) = 0
426 ecb_ctz32 (6) = 1 439 ecb_ctz32 (6) = 1
440
441=item bool ecb_is_pot32 (uint32_t x)
442
443=item bool ecb_is_pot64 (uint32_t x)
444
445Return true iff C<x> is a power of two or C<x == 0>.
446
447For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>.
427 448
428=item int ecb_ld32 (uint32_t x) 449=item int ecb_ld32 (uint32_t x)
429 450
430=item int ecb_ld64 (uint64_t x) 451=item int ecb_ld64 (uint64_t x)
431 452
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438This function is similar to the "count leading zero bits" function, except 459This function is similar to the "count leading zero bits" function, except
439that that one returns how many zero bits are "in front" of the number (in 460that that one returns how many zero bits are "in front" of the number (in
440the given data type), while C<ecb_ld> returns how many bits the number 461the given data type), while C<ecb_ld> returns how many bits the number
441itself requires. 462itself requires.
442 463
464For smaller types than C<uint32_t> you can safely use C<ecb_ld32>.
465
443=item int ecb_popcount32 (uint32_t x) 466=item int ecb_popcount32 (uint32_t x)
444 467
445=item int ecb_popcount64 (uint64_t x) 468=item int ecb_popcount64 (uint64_t x)
446 469
447Returns the number of bits set to 1 in C<x>. For example: 470Returns the number of bits set to 1 in C<x>.
471
472For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>.
473
474For example:
448 475
449 ecb_popcount32 (7) = 3 476 ecb_popcount32 (7) = 3
450 ecb_popcount32 (255) = 8 477 ecb_popcount32 (255) = 8
478
479=item uint8_t ecb_bitrev8 (uint8_t x)
480
481=item uint16_t ecb_bitrev16 (uint16_t x)
482
483=item uint32_t ecb_bitrev32 (uint32_t x)
484
485Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1
486and so on.
487
488Example:
489
490 ecb_bitrev8 (0xa7) = 0xea
491 ecb_bitrev32 (0xffcc4411) = 0x882233ff
451 492
452=item uint32_t ecb_bswap16 (uint32_t x) 493=item uint32_t ecb_bswap16 (uint32_t x)
453 494
454=item uint32_t ecb_bswap32 (uint32_t x) 495=item uint32_t ecb_bswap32 (uint32_t x)
455 496
… …
513change direction for negative values: 554change direction for negative values:
514 555
515 for (m = -100; m <= 100; ++m) 556 for (m = -100; m <= 100; ++m)
516 int elem = myarray [ecb_mod (m, ecb_array_length (myarray))]; 557 int elem = myarray [ecb_mod (m, ecb_array_length (myarray))];
517 558
559=item x = ecb_div_rd (val, div)
560
561=item x = ecb_div_ru (val, div)
562
563Returns C<val> divided by C<div> rounded down or up, respectively.
564C<val> and C<div> must have integer types and C<div> must be strictly
565positive. Note that these functions are implemented with macros in C
566and with function templates in C++.
567
518=back 568=back
519 569
520=head2 UTILITY 570=head2 UTILITY
521 571
522=over 4 572=over 4

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