chore: rename to getNonnegativeInt32LE

src/parser/on_demand/parse_to_elements.ts

@@ -45,13 +45,13 @@ export type BSONElement = [
   length: number
 ];
 
-const getSize = (source: Uint8Array, offset: number) => {
+function getSize(source: Uint8Array, offset: number) {
   try {
-    return NumberUtils.getSize(source, offset);
+    return NumberUtils.getNonnegativeInt32LE(source, offset);
   } catch (cause) {
     throw new BSONOffsetError('BSON size cannot be negative', offset, { cause });
   }
-};
+}
 
 /**
  * Searches for null terminator of a BSON element's value (Never the document null terminator)

src/utils/number_utils.ts

@@ -14,10 +14,9 @@ const isBigEndian = FLOAT_BYTES[7] === 0;
  */
 export type NumberUtils = {
   /**
-   * Parses a int32 little-endian at offset, throws if it is negative.
-   * - size as in `size_t`
+   * Parses a signed int32 at offset. Throws a `RangeError` if value is negative.
    */
-  getSize: (source: Uint8Array, offset: number) => number;
+  getNonnegativeInt32LE: (source: Uint8Array, offset: number) => number;
   getInt32LE: (source: Uint8Array, offset: number) => number;
   getUint32LE: (source: Uint8Array, offset: number) => number;
   getUint32BE: (source: Uint8Array, offset: number) => number;
@@ -36,7 +35,7 @@ export type NumberUtils = {
  * @public
  */
 export const NumberUtils: NumberUtils = {
-  getSize(source: Uint8Array, offset: number): number {
+  getNonnegativeInt32LE(source: Uint8Array, offset: number): number {
     if (source[offset + 3] > 127) {
       throw new RangeError(`Size cannot be negative at offset: ${offset}`);
     }

test/node/utils/number_utils.test.ts

@@ -30,6 +30,24 @@ describe('NumberUtils', () => {
   /** Make a Uint8Array in a less verbose way */
   const b = (...values) => new Uint8Array(values);
 
+  context('getNonnegativeInt32LE()', () => {
+    it('parses an int32 little endian', () => {
+      expect(NumberUtils.getNonnegativeInt32LE(b(0, 0, 0, 1), 0)).to.equal(1 << 24);
+    });
+
+    it('throws if int32 is negative', () => {
+      expect(() => NumberUtils.getNonnegativeInt32LE(b(0, 0, 0, 128), 0)).to.throw(RangeError);
+    });
+
+    it('parses an int32 little endian at offset', () => {
+      expect(NumberUtils.getNonnegativeInt32LE(b(0, 0, 0, 0, 0, 1), 2)).to.equal(1 << 24);
+    });
+
+    it('does not check bounds of offset', () => {
+      expect(NumberUtils.getNonnegativeInt32LE(b(0, 0, 0, 1), 4)).to.be.NaN;
+    });
+  });
+
   context('getInt32LE()', () => {
     it('parses an int32 little endian', () => {
       expect(NumberUtils.getInt32LE(b(0, 0, 0, 1), 0)).to.equal(1 << 24);