ethers.js/lib.esm/utils/utf8.js
2023-02-12 22:14:26 -05:00

220 lines
7.5 KiB
JavaScript

/**
* Using strings in Ethereum (or any security-basd system) requires
* additional care. These utilities attempt to mitigate some of the
* safety issues as well as provide the ability to recover and analyse
* strings.
*
* @_subsection api/utils:Strings and UTF-8 [about-strings]
*/
import { getBytes } from "./data.js";
import { assertArgument, assertNormalize } from "./errors.js";
function errorFunc(reason, offset, bytes, output, badCodepoint) {
assertArgument(false, `invalid codepoint at offset ${offset}; ${reason}`, "bytes", bytes);
}
function ignoreFunc(reason, offset, bytes, output, badCodepoint) {
// If there is an invalid prefix (including stray continuation), skip any additional continuation bytes
if (reason === "BAD_PREFIX" || reason === "UNEXPECTED_CONTINUE") {
let i = 0;
for (let o = offset + 1; o < bytes.length; o++) {
if (bytes[o] >> 6 !== 0x02) {
break;
}
i++;
}
return i;
}
// This byte runs us past the end of the string, so just jump to the end
// (but the first byte was read already read and therefore skipped)
if (reason === "OVERRUN") {
return bytes.length - offset - 1;
}
// Nothing to skip
return 0;
}
function replaceFunc(reason, offset, bytes, output, badCodepoint) {
// Overlong representations are otherwise "valid" code points; just non-deistingtished
if (reason === "OVERLONG") {
assertArgument(typeof (badCodepoint) === "number", "invalid bad code point for replacement", "badCodepoint", badCodepoint);
output.push(badCodepoint);
return 0;
}
// Put the replacement character into the output
output.push(0xfffd);
// Otherwise, process as if ignoring errors
return ignoreFunc(reason, offset, bytes, output, badCodepoint);
}
/**
* A handful of popular, built-in UTF-8 error handling strategies.
*
* **``"error"``** - throws on ANY illegal UTF-8 sequence or
* non-canonical (overlong) codepoints (this is the default)
*
* **``"ignore"``** - silently drops any illegal UTF-8 sequence
* and accepts non-canonical (overlong) codepoints
*
* **``"replace"``** - replace any illegal UTF-8 sequence with the
* UTF-8 replacement character (i.e. `\ufffd`) and accepts
* non-canonical (overlong) codepoints
*
* @returns: Record<"error" | "ignore" | "replace", Utf8ErrorFunc>
*/
export const Utf8ErrorFuncs = Object.freeze({
error: errorFunc,
ignore: ignoreFunc,
replace: replaceFunc
});
// http://stackoverflow.com/questions/13356493/decode-utf-8-with-javascript#13691499
function getUtf8CodePoints(_bytes, onError) {
if (onError == null) {
onError = Utf8ErrorFuncs.error;
}
const bytes = getBytes(_bytes, "bytes");
const result = [];
let i = 0;
// Invalid bytes are ignored
while (i < bytes.length) {
const c = bytes[i++];
// 0xxx xxxx
if (c >> 7 === 0) {
result.push(c);
continue;
}
// Multibyte; how many bytes left for this character?
let extraLength = null;
let overlongMask = null;
// 110x xxxx 10xx xxxx
if ((c & 0xe0) === 0xc0) {
extraLength = 1;
overlongMask = 0x7f;
// 1110 xxxx 10xx xxxx 10xx xxxx
}
else if ((c & 0xf0) === 0xe0) {
extraLength = 2;
overlongMask = 0x7ff;
// 1111 0xxx 10xx xxxx 10xx xxxx 10xx xxxx
}
else if ((c & 0xf8) === 0xf0) {
extraLength = 3;
overlongMask = 0xffff;
}
else {
if ((c & 0xc0) === 0x80) {
i += onError("UNEXPECTED_CONTINUE", i - 1, bytes, result);
}
else {
i += onError("BAD_PREFIX", i - 1, bytes, result);
}
continue;
}
// Do we have enough bytes in our data?
if (i - 1 + extraLength >= bytes.length) {
i += onError("OVERRUN", i - 1, bytes, result);
continue;
}
// Remove the length prefix from the char
let res = c & ((1 << (8 - extraLength - 1)) - 1);
for (let j = 0; j < extraLength; j++) {
let nextChar = bytes[i];
// Invalid continuation byte
if ((nextChar & 0xc0) != 0x80) {
i += onError("MISSING_CONTINUE", i, bytes, result);
res = null;
break;
}
;
res = (res << 6) | (nextChar & 0x3f);
i++;
}
// See above loop for invalid continuation byte
if (res === null) {
continue;
}
// Maximum code point
if (res > 0x10ffff) {
i += onError("OUT_OF_RANGE", i - 1 - extraLength, bytes, result, res);
continue;
}
// Reserved for UTF-16 surrogate halves
if (res >= 0xd800 && res <= 0xdfff) {
i += onError("UTF16_SURROGATE", i - 1 - extraLength, bytes, result, res);
continue;
}
// Check for overlong sequences (more bytes than needed)
if (res <= overlongMask) {
i += onError("OVERLONG", i - 1 - extraLength, bytes, result, res);
continue;
}
result.push(res);
}
return result;
}
// http://stackoverflow.com/questions/18729405/how-to-convert-utf8-string-to-byte-array
/**
* Returns the UTF-8 byte representation of %%str%%.
*
* If %%form%% is specified, the string is normalized.
*/
export function toUtf8Bytes(str, form) {
if (form != null) {
assertNormalize(form);
str = str.normalize(form);
}
let result = [];
for (let i = 0; i < str.length; i++) {
const c = str.charCodeAt(i);
if (c < 0x80) {
result.push(c);
}
else if (c < 0x800) {
result.push((c >> 6) | 0xc0);
result.push((c & 0x3f) | 0x80);
}
else if ((c & 0xfc00) == 0xd800) {
i++;
const c2 = str.charCodeAt(i);
assertArgument(i < str.length && ((c2 & 0xfc00) === 0xdc00), "invalid surrogate pair", "str", str);
// Surrogate Pair
const pair = 0x10000 + ((c & 0x03ff) << 10) + (c2 & 0x03ff);
result.push((pair >> 18) | 0xf0);
result.push(((pair >> 12) & 0x3f) | 0x80);
result.push(((pair >> 6) & 0x3f) | 0x80);
result.push((pair & 0x3f) | 0x80);
}
else {
result.push((c >> 12) | 0xe0);
result.push(((c >> 6) & 0x3f) | 0x80);
result.push((c & 0x3f) | 0x80);
}
}
return new Uint8Array(result);
}
;
//export
function _toUtf8String(codePoints) {
return codePoints.map((codePoint) => {
if (codePoint <= 0xffff) {
return String.fromCharCode(codePoint);
}
codePoint -= 0x10000;
return String.fromCharCode((((codePoint >> 10) & 0x3ff) + 0xd800), ((codePoint & 0x3ff) + 0xdc00));
}).join("");
}
/**
* Returns the string represented by the UTF-8 data %%bytes%%.
*
* When %%onError%% function is specified, it is called on UTF-8
* errors allowing recovery using the [[Utf8ErrorFunc]] API.
* (default: [error](Utf8ErrorFuncs))
*/
export function toUtf8String(bytes, onError) {
return _toUtf8String(getUtf8CodePoints(bytes, onError));
}
/**
* Returns the UTF-8 code-points for %%str%%.
*
* If %%form%% is specified, the string is normalized.
*/
export function toUtf8CodePoints(str, form) {
return getUtf8CodePoints(toUtf8Bytes(str, form));
}
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