mingo
Version:
MongoDB query language for in-memory objects
63 lines (62 loc) • 2.03 kB
JavaScript
import { computeValue } from "../../../core/_internal";
import { assert, isArray, isInteger, isNil, isString } from "../../../util";
import {
errExpectNumber,
errExpectString,
errInvalidArgs,
INT_OPTS
} from "../_internal";
const OP = "$substrBytes";
const $substrBytes = (obj, expr, options) => {
assert(isArray(expr) && expr.length === 3, `${OP} expects array(3)`);
const [s, index, count] = computeValue(obj, expr, null, options);
const foe = options.failOnError;
const nil = isNil(s);
if (!nil && !isString(s)) return errExpectString(foe, `${OP} arg1 <string>`);
if (!isInteger(index) || index < 0)
return errExpectNumber(foe, `${OP} arg2 <index>`, INT_OPTS.index);
if (!isInteger(count) || count < 0)
return errExpectNumber(foe, `${OP} arg3 <count>`, INT_OPTS.index);
if (nil) return "";
let utf8Pos = 0;
let start16 = null;
let end16 = null;
const err = `${OP} UTF-8 boundary falls inside a continuation byte`;
for (let i = 0; i < s.length; ) {
const cp = s.codePointAt(i);
const utf8Len = cp < 128 ? 1 : cp < 2048 ? 2 : cp < 65536 ? 3 : 4;
const utf16Len = cp > 65535 ? 2 : 1;
if (start16 === null) {
if (index > utf8Pos && index < utf8Pos + utf8Len)
return errInvalidArgs(foe, err);
if (utf8Pos === index) {
start16 = i;
}
}
const endByte = index + count;
if (start16 !== null && end16 === null) {
if (endByte > utf8Pos && endByte < utf8Pos + utf8Len)
return errInvalidArgs(foe, err);
if (utf8Pos === endByte) {
end16 = i;
break;
}
}
utf8Pos += utf8Len;
i += utf16Len;
}
if (start16 === null) {
if (index === utf8Pos) return "";
return errInvalidArgs(foe, `${OP} byte index out of range`);
}
if (end16 === null) {
const endByte = index + count;
if (endByte !== utf8Pos)
return errInvalidArgs(foe, `${OP} count extends beyond UTF-8 length`);
end16 = s.length;
}
return s.slice(start16, end16);
};
export {
$substrBytes
};