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fix(p2-shim): coerce browser file read bounds to numbers #1574

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Merged
vados-cosmonic merged 2 commits into from
Jun 1, 2026
+19 −1
Merged

fix(p2-shim): coerce browser file read bounds to numbers #1574

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6a0d7ac
fix(p2-shim): coerce browser file read bounds to numbers
May 29, 2026
03aac37
chore(p2-shim): add helper function for coercing read args
vados-cosmonic Jun 1, 2026
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20 changes: 19 additions & 1 deletion packages/preview2-shim/lib/browser/filesystem.js
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,22 @@ const timeZero = {
nanoseconds: 0,
};

/** Coerce the given object to a safe integer */
function coerceToSafeIntegerNumber(obj) {
let n;
if (typeof obj === "number") {
n = obj;
} else if (typeof obj == "bigint") {
n = Number(obj);
} else {
throw new TypeError(`unexpected non-numeric type: ${obj}`);
}
if (n > Number.MAX_SAFE_INTEGER) {
throw new TypeError(`excessively large number: ${n}`);
}
return n;
}

function getChildEntry(parentEntry, subpath, openFlags) {
if (subpath === "." && _rootPreopen && descriptorGetEntry(_rootPreopen[0]) === parentEntry) {
subpath = _getCwd();
Expand Down Expand Up @@ -188,7 +204,9 @@ class Descriptor {

read(length, offset) {
const source = getSource(this.#entry);
return [source.slice(offset, offset + length), offset + length >= source.byteLength];
const off = coerceToSafeIntegerNumber(offset);
const len = coerceToSafeIntegerNumber(length);
return [source.slice(off, off + len), off + len >= source.byteLength];
}

write(buffer, offset) {
Expand Down
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