github.com/egonelbre/exp@v0.0.0-20240430123955-ed1d3aa93911/niterator/unrollreverse/iterator.go (about)

     1  package unrollreverse
     2  
     3  import (
     4  	"io"
     5  
     6  	"github.com/egonelbre/exp/niterator/shape"
     7  )
     8  
     9  type Index struct {
    10  	Track  uint32
    11  	Shape  uint32
    12  	Stride uint32
    13  }
    14  
    15  type Iterator struct {
    16  	*shape.AP
    17  
    18  	Track     [4]Index
    19  	NextIndex uint32
    20  	Done      bool
    21  }
    22  
    23  func NewIterator(ap *shape.AP) *Iterator {
    24  	track := [4]Index{}
    25  	for i := range ap.Shape {
    26  		track[3-i].Shape = uint32(ap.Shape[i])
    27  		track[3-i].Stride = uint32(ap.Stride[i])
    28  	}
    29  
    30  	return &Iterator{
    31  		AP:    ap,
    32  		Track: track,
    33  	}
    34  }
    35  
    36  func (it *Iterator) IsDone() bool {
    37  	return it.Done
    38  }
    39  
    40  func (it *Iterator) Next() (int, error) {
    41  	if it.Done {
    42  		return 0, io.EOF
    43  	}
    44  
    45  	next := it.NextIndex
    46  	result := int(next)
    47  
    48  	x := &it.Track[0]
    49  	x.Track++
    50  	if x.Track < x.Shape {
    51  		next += x.Stride
    52  		it.NextIndex = next
    53  		return result, nil
    54  	}
    55  	x.Track = 0
    56  	next -= (x.Shape - 1) * x.Stride
    57  
    58  	x = &it.Track[1]
    59  	x.Track++
    60  	if x.Track < x.Shape {
    61  		next += x.Stride
    62  		it.NextIndex = next
    63  		return result, nil
    64  	}
    65  	x.Track = 0
    66  	next -= (x.Shape - 1) * x.Stride
    67  
    68  	x = &it.Track[2]
    69  	x.Track++
    70  	if x.Track < x.Shape {
    71  		next += x.Stride
    72  		it.NextIndex = next
    73  		return result, nil
    74  	}
    75  	x.Track = 0
    76  	next -= (x.Shape - 1) * x.Stride
    77  
    78  	x = &it.Track[3]
    79  	x.Track++
    80  	if x.Track < x.Shape {
    81  		next += x.Stride
    82  		it.NextIndex = next
    83  		return result, nil
    84  	}
    85  	it.Done = true
    86  	it.NextIndex = next
    87  
    88  	return result, nil
    89  }