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fix: utf8 -> utf16 decoding bug on surrogate pairs #1486

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merged 4 commits into from
Oct 9, 2020
Merged

fix: utf8 -> utf16 decoding bug on surrogate pairs #1486

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e798c43
fix utf8 -> utf16 decoding bug on surrogate pairs
turbio Sep 10, 2020
696acac
fix lint
turbio Sep 10, 2020
de742f2
add test case for surrogate pair bug
turbio Sep 22, 2020
8b58788
Merge branch 'master' into patch-1
alexander-fenster Oct 9, 2020
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45 changes: 18 additions & 27 deletions lib/utf8/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -38,36 +38,27 @@ utf8.length = function utf8_length(string) {
* @returns {string} String read
*/
utf8.read = function utf8_read(buffer, start, end) {
var len = end - start;
if (len < 1)
if (end - start < 1) {
return "";
var parts = null,
chunk = [],
i = 0, // char offset
t; // temporary
while (start < end) {
t = buffer[start++];
if (t < 128)
chunk[i++] = t;
else if (t > 191 && t < 224)
chunk[i++] = (t & 31) << 6 | buffer[start++] & 63;
else if (t > 239 && t < 365) {
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My understanding of this function is that the passed in buffer is always an array of uint8s, each byte being a utf8 code unit. The condition t < 365 is a bit odd under this assumption, from profiling it actually forces v8 to deopt when t is compared to a non uint8 value. Alternatively I may have grossly misunderstood how this is expected to work.

t = ((t & 7) << 18 | (buffer[start++] & 63) << 12 | (buffer[start++] & 63) << 6 | buffer[start++] & 63) - 0x10000;
chunk[i++] = 0xD800 + (t >> 10);
chunk[i++] = 0xDC00 + (t & 1023);
} else
chunk[i++] = (t & 15) << 12 | (buffer[start++] & 63) << 6 | buffer[start++] & 63;
if (i > 8191) {
(parts || (parts = [])).push(String.fromCharCode.apply(String, chunk));
i = 0;
}
}
if (parts) {
if (i)
parts.push(String.fromCharCode.apply(String, chunk.slice(0, i)));
return parts.join("");

var str = "";
for (var i = start; i < end;) {
var t = buffer[i++];
if (t <= 0x7F) {
str += String.fromCharCode(t);
} else if (t >= 0xC0 && t < 0xE0) {
str += String.fromCharCode((t & 0x1F) << 6 | buffer[i++] & 0x3F);
} else if (t >= 0xE0 && t < 0xF0) {
str += String.fromCharCode((t & 0xF) << 12 | (buffer[i++] & 0x3F) << 6 | buffer[i++] & 0x3F);
} else if (t >= 0xF0) {
var t2 = ((t & 7) << 18 | (buffer[i++] & 0x3F) << 12 | (buffer[i++] & 0x3F) << 6 | buffer[i++] & 0x3F) - 0x10000;
str += String.fromCharCode(0xD800 + (t2 >> 10));
str += String.fromCharCode(0xDC00 + (t2 & 0x3FF));
}
}
return String.fromCharCode.apply(String, chunk.slice(0, i));

return str;
};

/**
Expand Down