source: trip-planner-front/node_modules/pako/lib/utils/strings.js@ 6fe77af

Last change on this file since 6fe77af was 6a3a178, checked in by Ema <ema_spirova@…>, 3 years ago

initial commit

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1// String encode/decode helpers
2'use strict';
3
4
5var utils = require('./common');
6
7
8// Quick check if we can use fast array to bin string conversion
9//
10// - apply(Array) can fail on Android 2.2
11// - apply(Uint8Array) can fail on iOS 5.1 Safari
12//
13var STR_APPLY_OK = true;
14var STR_APPLY_UIA_OK = true;
15
16try { String.fromCharCode.apply(null, [ 0 ]); } catch (__) { STR_APPLY_OK = false; }
17try { String.fromCharCode.apply(null, new Uint8Array(1)); } catch (__) { STR_APPLY_UIA_OK = false; }
18
19
20// Table with utf8 lengths (calculated by first byte of sequence)
21// Note, that 5 & 6-byte values and some 4-byte values can not be represented in JS,
22// because max possible codepoint is 0x10ffff
23var _utf8len = new utils.Buf8(256);
24for (var q = 0; q < 256; q++) {
25 _utf8len[q] = (q >= 252 ? 6 : q >= 248 ? 5 : q >= 240 ? 4 : q >= 224 ? 3 : q >= 192 ? 2 : 1);
26}
27_utf8len[254] = _utf8len[254] = 1; // Invalid sequence start
28
29
30// convert string to array (typed, when possible)
31exports.string2buf = function (str) {
32 var buf, c, c2, m_pos, i, str_len = str.length, buf_len = 0;
33
34 // count binary size
35 for (m_pos = 0; m_pos < str_len; m_pos++) {
36 c = str.charCodeAt(m_pos);
37 if ((c & 0xfc00) === 0xd800 && (m_pos + 1 < str_len)) {
38 c2 = str.charCodeAt(m_pos + 1);
39 if ((c2 & 0xfc00) === 0xdc00) {
40 c = 0x10000 + ((c - 0xd800) << 10) + (c2 - 0xdc00);
41 m_pos++;
42 }
43 }
44 buf_len += c < 0x80 ? 1 : c < 0x800 ? 2 : c < 0x10000 ? 3 : 4;
45 }
46
47 // allocate buffer
48 buf = new utils.Buf8(buf_len);
49
50 // convert
51 for (i = 0, m_pos = 0; i < buf_len; m_pos++) {
52 c = str.charCodeAt(m_pos);
53 if ((c & 0xfc00) === 0xd800 && (m_pos + 1 < str_len)) {
54 c2 = str.charCodeAt(m_pos + 1);
55 if ((c2 & 0xfc00) === 0xdc00) {
56 c = 0x10000 + ((c - 0xd800) << 10) + (c2 - 0xdc00);
57 m_pos++;
58 }
59 }
60 if (c < 0x80) {
61 /* one byte */
62 buf[i++] = c;
63 } else if (c < 0x800) {
64 /* two bytes */
65 buf[i++] = 0xC0 | (c >>> 6);
66 buf[i++] = 0x80 | (c & 0x3f);
67 } else if (c < 0x10000) {
68 /* three bytes */
69 buf[i++] = 0xE0 | (c >>> 12);
70 buf[i++] = 0x80 | (c >>> 6 & 0x3f);
71 buf[i++] = 0x80 | (c & 0x3f);
72 } else {
73 /* four bytes */
74 buf[i++] = 0xf0 | (c >>> 18);
75 buf[i++] = 0x80 | (c >>> 12 & 0x3f);
76 buf[i++] = 0x80 | (c >>> 6 & 0x3f);
77 buf[i++] = 0x80 | (c & 0x3f);
78 }
79 }
80
81 return buf;
82};
83
84// Helper (used in 2 places)
85function buf2binstring(buf, len) {
86 // On Chrome, the arguments in a function call that are allowed is `65534`.
87 // If the length of the buffer is smaller than that, we can use this optimization,
88 // otherwise we will take a slower path.
89 if (len < 65534) {
90 if ((buf.subarray && STR_APPLY_UIA_OK) || (!buf.subarray && STR_APPLY_OK)) {
91 return String.fromCharCode.apply(null, utils.shrinkBuf(buf, len));
92 }
93 }
94
95 var result = '';
96 for (var i = 0; i < len; i++) {
97 result += String.fromCharCode(buf[i]);
98 }
99 return result;
100}
101
102
103// Convert byte array to binary string
104exports.buf2binstring = function (buf) {
105 return buf2binstring(buf, buf.length);
106};
107
108
109// Convert binary string (typed, when possible)
110exports.binstring2buf = function (str) {
111 var buf = new utils.Buf8(str.length);
112 for (var i = 0, len = buf.length; i < len; i++) {
113 buf[i] = str.charCodeAt(i);
114 }
115 return buf;
116};
117
118
119// convert array to string
120exports.buf2string = function (buf, max) {
121 var i, out, c, c_len;
122 var len = max || buf.length;
123
124 // Reserve max possible length (2 words per char)
125 // NB: by unknown reasons, Array is significantly faster for
126 // String.fromCharCode.apply than Uint16Array.
127 var utf16buf = new Array(len * 2);
128
129 for (out = 0, i = 0; i < len;) {
130 c = buf[i++];
131 // quick process ascii
132 if (c < 0x80) { utf16buf[out++] = c; continue; }
133
134 c_len = _utf8len[c];
135 // skip 5 & 6 byte codes
136 if (c_len > 4) { utf16buf[out++] = 0xfffd; i += c_len - 1; continue; }
137
138 // apply mask on first byte
139 c &= c_len === 2 ? 0x1f : c_len === 3 ? 0x0f : 0x07;
140 // join the rest
141 while (c_len > 1 && i < len) {
142 c = (c << 6) | (buf[i++] & 0x3f);
143 c_len--;
144 }
145
146 // terminated by end of string?
147 if (c_len > 1) { utf16buf[out++] = 0xfffd; continue; }
148
149 if (c < 0x10000) {
150 utf16buf[out++] = c;
151 } else {
152 c -= 0x10000;
153 utf16buf[out++] = 0xd800 | ((c >> 10) & 0x3ff);
154 utf16buf[out++] = 0xdc00 | (c & 0x3ff);
155 }
156 }
157
158 return buf2binstring(utf16buf, out);
159};
160
161
162// Calculate max possible position in utf8 buffer,
163// that will not break sequence. If that's not possible
164// - (very small limits) return max size as is.
165//
166// buf[] - utf8 bytes array
167// max - length limit (mandatory);
168exports.utf8border = function (buf, max) {
169 var pos;
170
171 max = max || buf.length;
172 if (max > buf.length) { max = buf.length; }
173
174 // go back from last position, until start of sequence found
175 pos = max - 1;
176 while (pos >= 0 && (buf[pos] & 0xC0) === 0x80) { pos--; }
177
178 // Very small and broken sequence,
179 // return max, because we should return something anyway.
180 if (pos < 0) { return max; }
181
182 // If we came to start of buffer - that means buffer is too small,
183 // return max too.
184 if (pos === 0) { return max; }
185
186 return (pos + _utf8len[buf[pos]] > max) ? pos : max;
187};
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