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
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
|
"use strict";
var Zmodem = module.exports;
const HEX_DIGITS = [ 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 97, 98, 99, 100, 101, 102 ];
const HEX_OCTET_VALUE = {};
for (var hd=0; hd<HEX_DIGITS.length; hd++) {
HEX_OCTET_VALUE[ HEX_DIGITS[hd] ] = hd;
}
/**
* General, non-ZMODEM-specific encoding logic.
*
* @exports ENCODELIB
*/
Zmodem.ENCODELIB = {
/**
* Return an array with the given number as 2 big-endian bytes.
*
* @param {number} number - The number to encode.
*
* @returns {number[]} The octet values.
*/
pack_u16_be: function pack_u16_be(number) {
if (number > 0xffff) throw( "Number cannot exceed 16 bits: " + number )
return [ number >> 8, number & 0xff ];
},
/**
* Return an array with the given number as 4 little-endian bytes.
*
* @param {number} number - The number to encode.
*
* @returns {number[]} The octet values.
*/
pack_u32_le: function pack_u32_le(number) {
//Can’t bit-shift because that runs into JS’s bit-shift problem.
//(See _updcrc32() for an example.)
var high_bytes = number / 65536; //fraction is ok
//a little-endian 4-byte sequence
return [
number & 0xff,
(number & 65535) >> 8,
high_bytes & 0xff,
high_bytes >> 8,
];
},
/**
* The inverse of pack_u16_be() - i.e., take in 2 octet values
* and parse them as an unsigned, 2-byte big-endian number.
*
* @param {number[]} octets - The octet values (2 of them).
*
* @returns {number} The decoded number.
*/
unpack_u16_be: function unpack_u16_be(bytes_arr) {
return (bytes_arr[0] << 8) + bytes_arr[1];
},
/**
* The inverse of pack_u32_le() - i.e., take in a 4-byte sequence
* and parse it as an unsigned, 4-byte little-endian number.
*
* @param {number[]} octets - The octet values (4 of them).
*
* @returns {number} The decoded number.
*/
unpack_u32_le: function unpack_u32_le(octets) {
//<sigh> … (254 << 24 is -33554432, according to JavaScript)
return octets[0] + (octets[1] << 8) + (octets[2] << 16) + (octets[3] * 16777216);
},
/**
* Encode a series of octet values to be the octet values that
* correspond to the ASCII hex characters for each octet. The
* returned array is suitable for use as binary data.
*
* For example:
*
* Original Hex Returned
* 254 fe 102, 101
* 12 0c 48, 99
* 129 81 56, 49
*
* @param {number[]} octets - The original octet values.
*
* @returns {number[]} The octet values that correspond to an ASCII
* representation of the given octets.
*/
octets_to_hex: function octets_to_hex(octets) {
var hex = [];
for (var o=0; o<octets.length; o++) {
hex.push(
HEX_DIGITS[ octets[o] >> 4 ],
HEX_DIGITS[ octets[o] & 0x0f ]
);
}
return hex;
},
/**
* The inverse of octets_to_hex(): takes an array
* of hex octet pairs and returns their octet values.
*
* @param {number[]} hex_octets - The hex octet values.
*
* @returns {number[]} The parsed octet values.
*/
parse_hex_octets: function parse_hex_octets(hex_octets) {
var octets = new Array(hex_octets.length / 2);
for (var i=0; i<octets.length; i++) {
octets[i] = (HEX_OCTET_VALUE[ hex_octets[2 * i] ] << 4) + HEX_OCTET_VALUE[ hex_octets[1 + 2 * i] ];
}
return octets;
},
};
|
