feat: handle JSON decoding of large integers as BigInt

For numbers that have a decimal point, always return as a plain `number` type. Otherwise, for integers that are larger than Number.MAX_SAFE_INTEGER or smaller than Number.MIN_SAFE_INTEGER, return them as a `BigInt`.
rvagg · Aug 5, 2021 · dc87eb4 · dc87eb4
1 parent ed03df7
commit dc87eb4
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Showing 3 changed files with 45 additions and 4 deletions.
diff --git a/lib/json/decode.js b/lib/json/decode.js
@@ -71,6 +71,7 @@ class Tokenizer {
   parseNumber () {
     const startPos = this.pos
     let negative = false
+    let float = false
 
     /**
      * @param {number[]} chars
@@ -95,6 +96,7 @@ class Tokenizer {
       this.pos++
       if (this.ch() === 46) { // '.'
         this.pos++
+        float = true
       } else {
         return new Token(Type.uint, 0, this.pos - startPos)
       }
@@ -104,20 +106,31 @@ class Tokenizer {
       throw new Error(`${decodeErrPrefix} unexpected token at position ${this.pos}`)
     }
     if (!this.done() && this.ch() === 46) { // '.'
+      if (float) {
+        throw new Error(`${decodeErrPrefix} unexpected token at position ${this.pos}`)
+      }
+      float = true
       this.pos++
       swallow([48, 49, 50, 51, 52, 53, 54, 55, 56, 57]) // DIGIT
     }
     if (!this.done() && (this.ch() === 101 || this.ch() === 69)) { // '[eE]'
+      float = true
       this.pos++
       if (!this.done() && (this.ch() === 43 || this.ch() === 45)) { // '+', '-'
         this.pos++
       }
       swallow([48, 49, 50, 51, 52, 53, 54, 55, 56, 57]) // DIGIT
     }
-    // TODO: check canonical form of this number?
     // @ts-ignore
-    const float = parseFloat(String.fromCharCode.apply(null, this.data.subarray(startPos, this.pos)))
-    return new Token(Number.isInteger(float) ? float >= 0 ? Type.uint : Type.negint : Type.float, float, this.pos - startPos)
+    const numStr = String.fromCharCode.apply(null, this.data.subarray(startPos, this.pos))
+    const num = parseFloat(numStr)
+    if (float) {
+      return new Token(Type.float, num, this.pos - startPos)
+    }
+    if (Number.isSafeInteger(num)) {
+      return new Token(num >= 0 ? Type.uint : Type.negint, num, this.pos - startPos)
+    }
+    return new Token(num >= 0 ? Type.uint : Type.negint, BigInt(numStr), this.pos - startPos)
   }
 
   /**

diff --git a/test/test-1negint.js b/test/test-1negint.js
@@ -24,7 +24,8 @@ const fixtures = [
   // kind of hard to assert on these (TODO: improve bignum handling)
   { data: '3b001fffffffffffff', expected: BigInt('-9007199254740992') /* Number.MIN_SAFE_INTEGER - 1 */, type: 'negint64' },
   { data: '3b0020000000000000', expected: BigInt('-9007199254740993') /* Number.MIN_SAFE_INTEGER - 2 */, type: 'negint64' },
-  { data: '3ba5f702b3a5f702b3', expected: BigInt('-11959030306112471732'), type: 'negint64' }
+  { data: '3ba5f702b3a5f702b3', expected: BigInt('-11959030306112471732'), type: 'negint64' },
+  { data: '3bffffffffffffffff', expected: BigInt('-18446744073709551616'), type: 'negint64' }
 ]
 
 describe('negint', () => {

diff --git a/test/test-json.js b/test/test-json.js
@@ -58,6 +58,32 @@ describe('json basics', () => {
     verifyRoundTrip(1.0011111e-18)
   })
 
+  it('handles large integers as BigInt', () => {
+    const verify = (inp, str) => {
+      if (str === undefined) {
+        str = String(inp)
+      }
+      assert.strictEqual(decode(toBytes(str)), inp)
+    }
+    verify(Number.MAX_SAFE_INTEGER)
+    verify(-Number.MAX_SAFE_INTEGER)
+    verify(BigInt('9007199254740992')) // Number.MAX_SAFE_INTEGER+1
+    verify(BigInt('9007199254740993'))
+    verify(BigInt('11959030306112471731'))
+    verify(BigInt('18446744073709551615')) // max uint64
+    verify(BigInt('9223372036854775807')) // max int64
+    verify(BigInt('-9007199254740992'))
+    verify(BigInt('-9007199254740993'))
+    verify(BigInt('-9223372036854776000')) // min int64
+    verify(BigInt('-11959030306112471732'))
+    verify(BigInt('-18446744073709551616')) // min -uint64
+
+    // these are "floats", distinct from "ints" which wouldn't have the `.` in them
+    verify(-9007199254740992, '-9007199254740992.0')
+    verify(-9223372036854776000, '-9223372036854776000.0')
+    verify(-18446744073709551616, '-18446744073709551616.0')
+  })
+
   it('can round-trip string literals', () => {
     const testCases = [
       JSON.stringify(''),
@@ -154,5 +180,6 @@ describe('json basics', () => {
     assert.throws(() => decode(toBytes('[tr]')), 'CBOR decode error: unexpected end of input at position 1')
     assert.throws(() => decode(toBytes('{"v":flase}')), 'CBOR decode error: unexpected token at position 7, expected to find \'false\'')
     assert.throws(() => decode(toBytes('[fa]')), 'CBOR decode error: unexpected end of input at position 1')
+    assert.throws(() => decode(toBytes('-0..1')), 'CBOR decode error: unexpected token at position 3')
   })
 })