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Added more general error handling (e.g. error, ignore, replace) for c…
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…alling toUtf8String.
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@ricmoo
ricmoo committed Jan 21, 2020
1 parent 2d72c85 commit a055edb
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Showing 3 changed files with 146 additions and 47 deletions.
6 changes: 5 additions & 1 deletion packages/strings/src.ts/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,14 +2,18 @@

import { formatBytes32String, parseBytes32String } from "./bytes32";
import { nameprep } from "./idna";
import { _toEscapedUtf8String, toUtf8Bytes, toUtf8CodePoints, toUtf8String, UnicodeNormalizationForm } from "./utf8";
import { _toEscapedUtf8String, toUtf8Bytes, toUtf8CodePoints, toUtf8String, UnicodeNormalizationForm, Utf8ErrorFunc, Utf8ErrorFuncs, Utf8ErrorReason } from "./utf8";

export {
_toEscapedUtf8String,
toUtf8Bytes,
toUtf8CodePoints,
toUtf8String,

Utf8ErrorFunc,
Utf8ErrorFuncs,
Utf8ErrorReason,

UnicodeNormalizationForm,

formatBytes32String,
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139 changes: 109 additions & 30 deletions packages/strings/src.ts/utf8.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -16,8 +16,94 @@ export enum UnicodeNormalizationForm {
NFKD = "NFKD"
};

export enum Utf8ErrorReason {
// A continuation byte was present where there was nothing to continue
// - offset = the index the codepoint began in
UNEXPECTED_CONTINUE = "unexpected continuation byte",

// An invalid (non-continuation) byte to start a UTF-8 codepoint was found
// - offset = the index the codepoint began in
BAD_PREFIX = "bad codepoint prefix",

// The string is too short to process the expected codepoint
// - offset = the index the codepoint began in
OVERRUN = "string overrun",

// A missing continuation byte was expected but not found
// - offset = the index the continuation byte was expected at
MISSING_CONTINUE = "missing continuation byte",

// The computed code point is outside the range for UTF-8
// - offset = start of this codepoint
// - badCodepoint = the computed codepoint; outside the UTF-8 range
OUT_OF_RANGE = "out of UTF-8 range",

// UTF-8 strings may not contain UTF-16 surrogate pairs
// - offset = start of this codepoint
// - badCodepoint = the computed codepoint; inside the UTF-16 surrogate range
UTF16_SURROGATE = "UTF-16 surrogate",

// The string is an overlong reperesentation
// - offset = start of this codepoint
// - badCodepoint = the computed codepoint; already bounds checked
OVERLONG = "overlong representation",
};


export type Utf8ErrorFunc = (reason: Utf8ErrorReason, offset: number, bytes: ArrayLike<number>, output: Array<number>, badCodepoint?: number) => number;

function errorFunc(reason: Utf8ErrorReason, offset: number, bytes: ArrayLike<number>, output: Array<number>, badCodepoint?: number): number {
return logger.throwArgumentError(`invalid codepoint at offset ${ offset }; ${ reason }`, "bytes", bytes);
}

function ignoreFunc(reason: Utf8ErrorReason, offset: number, bytes: ArrayLike<number>, output: Array<number>, badCodepoint?: number): number {

// If there is an invalid prefix (including stray continuation), skip any additional continuation bytes
if (reason === Utf8ErrorReason.BAD_PREFIX || reason === Utf8ErrorReason.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 === Utf8ErrorReason.OVERRUN) {
return bytes.length - offset - 1;
}

// Nothing to skip
return 0;
}

function replaceFunc(reason: Utf8ErrorReason, offset: number, bytes: ArrayLike<number>, output: Array<number>, badCodepoint?: number): number {

// Overlong representations are otherwise "valid" code points; just non-deistingtished
if (reason === Utf8ErrorReason.OVERLONG) {
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);
}

// Common error handing strategies
export const Utf8ErrorFuncs: { [ name: string ]: Utf8ErrorFunc } = Object.freeze({
error: errorFunc,
ignore: ignoreFunc,
replace: replaceFunc
});

// http://stackoverflow.com/questions/13356493/decode-utf-8-with-javascript#13691499
function getUtf8CodePoints(bytes: BytesLike, ignoreErrors?: boolean): Array<number> {
function getUtf8CodePoints(bytes: BytesLike, onError?: Utf8ErrorFunc): Array<number> {
if (onError == null) { onError = Utf8ErrorFuncs.error; }

bytes = arrayify(bytes);

const result: Array<number> = [];
Expand All @@ -27,6 +113,7 @@ function getUtf8CodePoints(bytes: BytesLike, ignoreErrors?: boolean): Array<numb
while(i < bytes.length) {

const c = bytes[i++];

// 0xxx xxxx
if (c >> 7 === 0) {
result.push(c);
Expand All @@ -53,24 +140,17 @@ function getUtf8CodePoints(bytes: BytesLike, ignoreErrors?: boolean): Array<numb
overlongMask = 0xffff;

} else {
if (!ignoreErrors) {
if ((c & 0xc0) === 0x80) {
throw new Error("invalid utf8 byte sequence; unexpected continuation byte");
}
throw new Error("invalid utf8 byte sequence; invalid prefix");
if ((c & 0xc0) === 0x80) {
i += onError(Utf8ErrorReason.UNEXPECTED_CONTINUE, i - 1, bytes, result);
} else {
i += onError(Utf8ErrorReason.BAD_PREFIX, i - 1, bytes, result);
}
continue;
}

// Do we have enough bytes in our data?
if (i + extraLength > bytes.length) {
if (!ignoreErrors) { throw new Error("invalid utf8 byte sequence; too short"); }

// If there is an invalid unprocessed byte, skip continuation bytes
for (; i < bytes.length; i++) {
if (bytes[i] >> 6 !== 0x02) { break; }
}

if (i - 1 + extraLength >= bytes.length) {
i += onError(Utf8ErrorReason.OVERRUN, i - 1, bytes, result);
continue;
}

Expand All @@ -82,6 +162,7 @@ function getUtf8CodePoints(bytes: BytesLike, ignoreErrors?: boolean): Array<numb

// Invalid continuation byte
if ((nextChar & 0xc0) != 0x80) {
i += onError(Utf8ErrorReason.MISSING_CONTINUE, i, bytes, result);
res = null;
break;
};
Expand All @@ -90,26 +171,24 @@ function getUtf8CodePoints(bytes: BytesLike, ignoreErrors?: boolean): Array<numb
i++;
}

if (res === null) {
if (!ignoreErrors) { throw new Error("invalid utf8 byte sequence; invalid continuation byte"); }
continue;
}

// Check for overlong seuences (more bytes than needed)
if (res <= overlongMask) {
if (!ignoreErrors) { throw new Error("invalid utf8 byte sequence; overlong"); }
continue;
}
// See above loop for invalid contimuation byte
if (res === null) { continue; }

// Maximum code point
if (res > 0x10ffff) {
if (!ignoreErrors) { throw new Error("invalid utf8 byte sequence; out-of-range"); }
i += onError(Utf8ErrorReason.OUT_OF_RANGE, i - 1 - extraLength, bytes, result, res);
continue;
}

// Reserved for UTF-16 surrogate halves
if (res >= 0xd800 && res <= 0xdfff) {
if (!ignoreErrors) { throw new Error("invalid utf8 byte sequence; utf-16 surrogate"); }
i += onError(Utf8ErrorReason.UTF16_SURROGATE, i - 1 - extraLength, bytes, result, res);
continue;
}

// Check for overlong sequences (more bytes than needed)
if (res <= overlongMask) {
i += onError(Utf8ErrorReason.OVERLONG, i - 1 - extraLength, bytes, result, res);
continue;
}

Expand Down Expand Up @@ -168,8 +247,8 @@ function escapeChar(value: number) {
return "\\u" + hex.substring(hex.length - 4);
}

export function _toEscapedUtf8String(bytes: BytesLike, ignoreErrors?: boolean): string {
return '"' + getUtf8CodePoints(bytes, ignoreErrors).map((codePoint) => {
export function _toEscapedUtf8String(bytes: BytesLike, onError?: Utf8ErrorFunc): string {
return '"' + getUtf8CodePoints(bytes, onError).map((codePoint) => {
if (codePoint < 256) {
switch (codePoint) {
case 8: return "\\b";
Expand Down Expand Up @@ -207,8 +286,8 @@ export function _toUtf8String(codePoints: Array<number>): string {
}).join("");
}

export function toUtf8String(bytes: BytesLike, ignoreErrors?: boolean): string {
return _toUtf8String(getUtf8CodePoints(bytes, ignoreErrors));
export function toUtf8String(bytes: BytesLike, onError?: Utf8ErrorFunc): string {
return _toUtf8String(getUtf8CodePoints(bytes, onError));
}

export function toUtf8CodePoints(str: string, form: UnicodeNormalizationForm = UnicodeNormalizationForm.current): Array<number> {
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48 changes: 32 additions & 16 deletions packages/tests/src.ts/test-utils.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -333,39 +333,55 @@ describe('Test Base64 coder', function() {
});

describe('Test UTF-8 coder', function() {
const overlong = ethers.utils.Utf8ErrorReason.OVERLONG;
const utf16Surrogate = ethers.utils.Utf8ErrorReason.UTF16_SURROGATE;
const overrun = ethers.utils.Utf8ErrorReason.OVERRUN;
const missingContinue = ethers.utils.Utf8ErrorReason.MISSING_CONTINUE;
const unexpectedContinue = ethers.utils.Utf8ErrorReason.UNEXPECTED_CONTINUE;
const outOfRange = ethers.utils.Utf8ErrorReason.OUT_OF_RANGE;

let BadUTF = [
// See: https://en.wikipedia.org/wiki/UTF-8#Overlong_encodings
{ bytes: [ 0xF0,0x82, 0x82, 0xAC ], reason: 'overlong', name: 'wikipedia overlong encoded Euro sign' },
{ bytes: [ 0xc0, 0x80 ], reason: 'overlong', name: '2-byte overlong - 0xc080' },
{ bytes: [ 0xc0, 0xbf ], reason: 'overlong', name: '2-byte overlong - 0xc0bf' },
{ bytes: [ 0xc1, 0x80 ], reason: 'overlong', name: '2-byte overlong - 0xc180' },
{ bytes: [ 0xc1, 0xbf ], reason: 'overlong', name: '2-byte overlong - 0xc1bf' },
{ bytes: [ 0xF0,0x82, 0x82, 0xAC ], reason: overlong, ignored: "", replaced: "\u20ac", name: 'wikipedia overlong encoded Euro sign' },
{ bytes: [ 0xc0, 0x80 ], reason: overlong, ignored: "", replaced: "\u0000", name: '2-byte overlong - 0xc080' },
{ bytes: [ 0xc0, 0xbf ], reason: overlong, ignored: "", replaced: "?", name: '2-byte overlong - 0xc0bf' },
{ bytes: [ 0xc1, 0x80 ], reason: overlong, ignored: "", replaced: "@", name: '2-byte overlong - 0xc180' },
{ bytes: [ 0xc1, 0xbf ], reason: overlong, ignored: "", replaced: "\u007f", name: '2-byte overlong - 0xc1bf' },

// Reserved UTF-16 Surrogate halves
{ bytes: [ 0xed, 0xa0, 0x80 ], reason: 'utf-16 surrogate', name: 'utf-16 surrogate - U+d800' },
{ bytes: [ 0xed, 0xbf, 0xbf ], reason: 'utf-16 surrogate', name: 'utf-16 surrogate - U+dfff' },
{ bytes: [ 0xed, 0xa0, 0x80 ], reason: utf16Surrogate, ignored: "", replaced: "\ufffd", name: 'utf-16 surrogate - U+d800' },
{ bytes: [ 0xed, 0xbf, 0xbf ], reason: utf16Surrogate, ignored: "", replaced: "\ufffd", name: 'utf-16 surrogate - U+dfff' },

// a leading byte not followed by enough continuation bytes
{ bytes: [ 0xdf ], reason: 'too short', name: 'too short - 2-bytes - 0x00' },
{ bytes: [ 0xe0 ], reason: 'too short', name: 'too short - 3-bytes' },
{ bytes: [ 0xe0, 0x80 ], reason: 'too short', name: 'too short - 3-bytes with 1' },
{ bytes: [ 0xdf ], reason: overrun, ignored: "", replaced: "\ufffd", name: 'too short - 2-bytes - 0x00' },
{ bytes: [ 0xe0 ], reason: overrun, ignored: "", replaced: "\ufffd", name: 'too short - 3-bytes' },
{ bytes: [ 0xe0, 0x80 ], reason: overrun, ignored: "", replaced: "\ufffd", name: 'too short - 3-bytes with 1' },

{ bytes: [ 0x80 ], reason: 'unexpected continuation byte', name: 'unexpected continuation byte' },
{ bytes: [ 0xc2, 0x00 ], reason: 'invalid continuation byte', name: 'invalid continuation byte - 0xc200' },
{ bytes: [ 0xc2, 0x40 ], reason: 'invalid continuation byte', name: 'invalid continuation byte - 0xc240' },
{ bytes: [ 0xc2, 0xc0 ], reason: 'invalid continuation byte', name: 'invalid continuation byte - 0xc2c0' },
{ bytes: [ 0x80 ], reason: unexpectedContinue, ignored: "", replaced: "\ufffd", name: 'unexpected continuation byte' },
{ bytes: [ 0xc2, 0x00 ], reason: missingContinue, ignored: "\u0000", replaced: "\ufffd\u0000", name: 'invalid continuation byte - 0xc200' },
{ bytes: [ 0xc2, 0x40 ], reason: missingContinue, ignored: "@", replaced: "\ufffd@", name: 'invalid continuation byte - 0xc240' },
{ bytes: [ 0xc2, 0xc0 ], reason: missingContinue, ignored: "", replaced: "\ufffd\ufffd", name: 'invalid continuation byte - 0xc2c0' },

// Out of range
{ bytes: [ 0xf4, 0x90, 0x80, 0x80 ], reason: 'out-of-range', name: 'out of range' },
{ bytes: [ 0xf4, 0x90, 0x80, 0x80 ], reason: outOfRange, ignored: "", replaced: "\ufffd", name: 'out of range' },
];

BadUTF.forEach(function(test) {
it('toUtf8String - ' + test.name, function() {
// Check the string using the ignoreErrors conversion
const ignored = ethers.utils.toUtf8String(test.bytes, ethers.utils.Utf8ErrorFuncs.ignore);
assert.equal(ignored, test.ignored, "ignoring errors matches");

// Check the string using the replaceErrors conversion
const replaced = ethers.utils.toUtf8String(test.bytes, ethers.utils.Utf8ErrorFuncs.replace);
assert.equal(replaced, test.replaced, "replaced errors matches");

// Check the string throws the correct error during conversion
assert.throws(function() {
let result = ethers.utils.toUtf8String(test.bytes);
console.log('Result', result);
}, function(error: Error) {
return (error.message.split(';').pop().trim() === test.reason)
return (error.message.split(";").pop().split("(")[0].trim() === test.reason)
}, test.name);
});
});
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