UNPKG

string-byte-slice

Version:

Like `string.slice()` but bytewise

www.github.com/ehmicky/string-byte-slice

ehmicky/string-byte-slice

46 lines (37 loc) • 1 kB
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
import{ FIRST_HIGH_SURROGATE, FIRST_LOW_SURROGATE, LAST_HIGH_SURROGATE, LAST_LOW_SURROGATE}from "../codepoints.js"; import{findCharIndex}from"./indices.js"; export const byteToChar=(input,byteIndex,isStart)=> byteIndex<0||Object.is(byteIndex,-0)? byteToCharBackward(input,byteIndex,isStart): byteToCharForward(input,byteIndex,isStart); const byteToCharForward=(input,byteIndex,isEnd)=> findCharIndex({ input, targetByteCount:byteIndex, firstStartSurrogate:FIRST_HIGH_SURROGATE, lastStartSurrogate:LAST_HIGH_SURROGATE, firstEndSurrogate:FIRST_LOW_SURROGATE, lastEndSurrogate:LAST_LOW_SURROGATE, increment:1, canBacktrack:isEnd, shift:0, charIndexInit:0 }); const byteToCharBackward=(input,byteIndex,isEnd)=> findCharIndex({ input, targetByteCount:-byteIndex, firstStartSurrogate:FIRST_LOW_SURROGATE, lastStartSurrogate:LAST_LOW_SURROGATE, firstEndSurrogate:FIRST_HIGH_SURROGATE, lastEndSurrogate:LAST_HIGH_SURROGATE, increment:-1, canBacktrack:!isEnd, shift:1, charIndexInit:input.length-1 });