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// String encode/decode helpers
'use strict';
var utils = require('./common');
// Quick check if we can use fast array to bin string conversion
//
// - apply(Array) can fail on Android 2.2
// - apply(Uint8Array) can fail on iOS 5.1 Safari
//
var STR_APPLY_OK = true; var STR_APPLY_UIA_OK = true;
try { String.fromCharCode.apply(null, [ 0 ]); } catch (__) { STR_APPLY_OK = false; } try { String.fromCharCode.apply(null, new Uint8Array(1)); } catch (__) { STR_APPLY_UIA_OK = false; }
// Table with utf8 lengths (calculated by first byte of sequence)
// Note, that 5 & 6-byte values and some 4-byte values can not be represented in JS,
// because max possible codepoint is 0x10ffff
var _utf8len = new utils.Buf8(256); for (var q = 0; q < 256; q++) { _utf8len[q] = (q >= 252 ? 6 : q >= 248 ? 5 : q >= 240 ? 4 : q >= 224 ? 3 : q >= 192 ? 2 : 1); } _utf8len[254] = _utf8len[254] = 1; // Invalid sequence start
// convert string to array (typed, when possible)
exports.string2buf = function (str) { var buf, c, c2, m_pos, i, str_len = str.length, buf_len = 0;
// count binary size
for (m_pos = 0; m_pos < str_len; m_pos++) { c = str.charCodeAt(m_pos); if ((c & 0xfc00) === 0xd800 && (m_pos + 1 < str_len)) { c2 = str.charCodeAt(m_pos + 1); if ((c2 & 0xfc00) === 0xdc00) { c = 0x10000 + ((c - 0xd800) << 10) + (c2 - 0xdc00); m_pos++; } } buf_len += c < 0x80 ? 1 : c < 0x800 ? 2 : c < 0x10000 ? 3 : 4; }
// allocate buffer
buf = new utils.Buf8(buf_len);
// convert
for (i = 0, m_pos = 0; i < buf_len; m_pos++) { c = str.charCodeAt(m_pos); if ((c & 0xfc00) === 0xd800 && (m_pos + 1 < str_len)) { c2 = str.charCodeAt(m_pos + 1); if ((c2 & 0xfc00) === 0xdc00) { c = 0x10000 + ((c - 0xd800) << 10) + (c2 - 0xdc00); m_pos++; } } if (c < 0x80) { /* one byte */ buf[i++] = c; } else if (c < 0x800) { /* two bytes */ buf[i++] = 0xC0 | (c >>> 6); buf[i++] = 0x80 | (c & 0x3f); } else if (c < 0x10000) { /* three bytes */ buf[i++] = 0xE0 | (c >>> 12); buf[i++] = 0x80 | (c >>> 6 & 0x3f); buf[i++] = 0x80 | (c & 0x3f); } else { /* four bytes */ buf[i++] = 0xf0 | (c >>> 18); buf[i++] = 0x80 | (c >>> 12 & 0x3f); buf[i++] = 0x80 | (c >>> 6 & 0x3f); buf[i++] = 0x80 | (c & 0x3f); } }
return buf; };
// Helper (used in 2 places)
function buf2binstring(buf, len) { // On Chrome, the arguments in a function call that are allowed is `65534`.
// If the length of the buffer is smaller than that, we can use this optimization,
// otherwise we will take a slower path.
if (len < 65534) { if ((buf.subarray && STR_APPLY_UIA_OK) || (!buf.subarray && STR_APPLY_OK)) { return String.fromCharCode.apply(null, utils.shrinkBuf(buf, len)); } }
var result = ''; for (var i = 0; i < len; i++) { result += String.fromCharCode(buf[i]); } return result; }
// Convert byte array to binary string
exports.buf2binstring = function (buf) { return buf2binstring(buf, buf.length); };
// Convert binary string (typed, when possible)
exports.binstring2buf = function (str) { var buf = new utils.Buf8(str.length); for (var i = 0, len = buf.length; i < len; i++) { buf[i] = str.charCodeAt(i); } return buf; };
// convert array to string
exports.buf2string = function (buf, max) { var i, out, c, c_len; var len = max || buf.length;
// Reserve max possible length (2 words per char)
// NB: by unknown reasons, Array is significantly faster for
// String.fromCharCode.apply than Uint16Array.
var utf16buf = new Array(len * 2);
for (out = 0, i = 0; i < len;) { c = buf[i++]; // quick process ascii
if (c < 0x80) { utf16buf[out++] = c; continue; }
c_len = _utf8len[c]; // skip 5 & 6 byte codes
if (c_len > 4) { utf16buf[out++] = 0xfffd; i += c_len - 1; continue; }
// apply mask on first byte
c &= c_len === 2 ? 0x1f : c_len === 3 ? 0x0f : 0x07; // join the rest
while (c_len > 1 && i < len) { c = (c << 6) | (buf[i++] & 0x3f); c_len--; }
// terminated by end of string?
if (c_len > 1) { utf16buf[out++] = 0xfffd; continue; }
if (c < 0x10000) { utf16buf[out++] = c; } else { c -= 0x10000; utf16buf[out++] = 0xd800 | ((c >> 10) & 0x3ff); utf16buf[out++] = 0xdc00 | (c & 0x3ff); } }
return buf2binstring(utf16buf, out); };
// Calculate max possible position in utf8 buffer,
// that will not break sequence. If that's not possible
// - (very small limits) return max size as is.
//
// buf[] - utf8 bytes array
// max - length limit (mandatory);
exports.utf8border = function (buf, max) { var pos;
max = max || buf.length; if (max > buf.length) { max = buf.length; }
// go back from last position, until start of sequence found
pos = max - 1; while (pos >= 0 && (buf[pos] & 0xC0) === 0x80) { pos--; }
// Very small and broken sequence,
// return max, because we should return something anyway.
if (pos < 0) { return max; }
// If we came to start of buffer - that means buffer is too small,
// return max too.
if (pos === 0) { return max; }
return (pos + _utf8len[buf[pos]] > max) ? pos : max; };
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