/
slice.rb
91 lines (82 loc) · 2.16 KB
/
slice.rb
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
module JMESPath
# @api private
module Nodes
class Slice < Node
def initialize(start, stop, step)
@start = start
@stop = stop
@step = step
raise Errors::InvalidValueError.new('slice step cannot be 0') if @step == 0
end
def visit(value)
if (value = value.respond_to?(:to_str) ? value.to_str : value.respond_to?(:to_ary) ? value.to_ary : nil)
start, stop, step = adjust_slice(value.size, @start, @stop, @step)
result = []
if step > 0
i = start
while i < stop
result << value[i]
i += step
end
else
i = start
while i > stop
result << value[i]
i += step
end
end
value.respond_to?(:to_str) ? result.join : result
else
nil
end
end
def optimize
if (@step.nil? || @step == 1) && @start && @stop && @start > 0 && @stop > @start
SimpleSlice.new(@start, @stop)
else
self
end
end
private
def adjust_slice(length, start, stop, step)
if step.nil?
step = 1
end
if start.nil?
start = step < 0 ? length - 1 : 0
else
start = adjust_endpoint(length, start, step)
end
if stop.nil?
stop = step < 0 ? -1 : length
else
stop = adjust_endpoint(length, stop, step)
end
[start, stop, step]
end
def adjust_endpoint(length, endpoint, step)
if endpoint < 0
endpoint += length
endpoint = step < 0 ? -1 : 0 if endpoint < 0
endpoint
elsif endpoint >= length
step < 0 ? length - 1 : length
else
endpoint
end
end
end
class SimpleSlice < Slice
def initialize(start, stop)
super(start, stop, 1)
end
def visit(value)
if (value = value.respond_to?(:to_str) ? value.to_str : value.respond_to?(:to_ary) ? value.to_ary : nil)
value[@start, @stop - @start]
else
nil
end
end
end
end
end