[FIX] web support

lib/src/decoder/pretty_print.dart

@@ -7,8 +7,7 @@
 
 import 'dart:convert';
 
-import 'package:ieee754/ieee754.dart';
-
+import '../utils/float_utils.dart' as float_utils;
 import 'stage1.dart';
 import '../constants.dart';
 import '../value/value.dart';
@@ -140,17 +139,17 @@ class _PrettyPrint implements Sink<RawValue> {
             break;
           case CborAdditionalInfo.halfPrecisionFloat:
             writer.write(
-              '(${FloatParts.fromFloat16Bytes(x.header.dataBytes).toDouble()})',
+              '(${float_utils.fromFloat16Bytes(x.header.dataBytes)})',
             );
             break;
           case CborAdditionalInfo.singlePrecisionFloat:
             writer.write(
-              '(${FloatParts.fromFloat32Bytes(x.header.dataBytes).toDouble()})',
+              '(${float_utils.fromFloat32Bytes(x.header.dataBytes)})',
             );
             break;
           case CborAdditionalInfo.doublePrecisionFloat:
             writer.write(
-              '(${FloatParts.fromFloat64Bytes(x.header.dataBytes).toDouble()})',
+              '(${float_utils.fromFloat64Bytes(x.header.dataBytes)})',
             );
             break;
           case CborAdditionalInfo.breakStop:

lib/src/decoder/stage3.dart

@@ -8,8 +8,8 @@
 import 'package:cbor/cbor.dart';
 import 'package:cbor/src/value/internal.dart';
 import 'package:collection/collection.dart';
-import 'package:ieee754/ieee754.dart';
 
+import '../utils/float_utils.dart' as float_utils;
 import '../utils/utils.dart';
 import '../constants.dart';
 import 'stage2.dart';
@@ -257,13 +257,13 @@ CborFloat _createFloat(RawValueTagged raw) {
   final double value;
   switch (raw.header.additionalInfo) {
     case CborAdditionalInfo.halfPrecisionFloat:
-      value = FloatParts.fromFloat16Bytes(raw.header.dataBytes).toDouble();
+      value = float_utils.fromFloat16Bytes(raw.header.dataBytes);
       break;
     case CborAdditionalInfo.singlePrecisionFloat:
-      value = FloatParts.fromFloat32Bytes(raw.header.dataBytes).toDouble();
+      value = float_utils.fromFloat32Bytes(raw.header.dataBytes);
       break;
     case CborAdditionalInfo.doublePrecisionFloat:
-      value = FloatParts.fromFloat64Bytes(raw.header.dataBytes).toDouble();
+      value = float_utils.fromFloat64Bytes(raw.header.dataBytes);
       break;
 
     default:

lib/src/simple.dart

@@ -109,6 +109,32 @@ class CborSimpleDecoder extends Converter<List<int>, Object?> {
 ///
 /// To see how CBOR values are transformed from and into objects, verify the
 /// documentation of both [CborValue.CborValue] and [CborValue.toObject].
+///
+/// ## JavaScript (dart2js) Limitations
+///
+/// On JavaScript (dart2js), there is no distinction between integer and
+/// floating-point numbers at the type level. All numbers are IEEE 754 doubles.
+/// This means:
+///
+/// - `0.0 is int` returns `true` on JS but `false` on native/WASM platforms
+/// - Integer-valued doubles like `1.0`, `-4.0`, `65504.0` are encoded as
+///   CBOR integers instead of CBOR floats
+/// - Very large doubles (e.g., `1.0e+300`) may lose precision when treated
+///   as integers
+///
+/// Note: This limitation does **not** apply to dart2wasm, which correctly
+/// distinguishes between integers and floats.
+///
+/// **Workaround:** To ensure consistent float encoding across all platforms,
+/// use the advanced API with explicit types:
+///
+/// ```dart
+/// // Instead of:
+/// cbor.encode(1.0);  // Encoded as int on JS, float on native/WASM
+///
+/// // Use:
+/// cborEncode(CborFloat(1.0));  // Always encoded as float
+/// ```
 class CborSimpleCodec extends Codec<Object?, List<int>> {
   final bool _encodeDateTimeEpoch;
   final bool _decodeBase64;

lib/src/utils/arg.dart

@@ -5,8 +5,6 @@
  * Copyright :  S.Hamblett
  */
 
-import '../constants.dart';
-
 /// The information encoded by additional Arg and the following bytes.
 abstract class Arg {
   static const Arg indefiniteLength = _ArgIndefiniteLength();
@@ -55,9 +53,15 @@ class _ArgInt implements Arg {
   const _ArgInt(this.value);
 
   @override
-  _ArgInt operator ~() => _ArgInt(
-    (~BigInt.from(value)).toSigned(CborConstants.bigIntSlice).toInt(),
-  );
+  Arg operator ~() {
+    final result = ~BigInt.from(value);
+    // Check if result fits in JS safe integer range (2^53-1)
+    // Use bitLength <= 53 as a conservative check
+    if (result.bitLength <= 53 && result.isValidInt) {
+      return _ArgInt(result.toInt());
+    }
+    return _ArgBigInt(result);
+  }
 
   @override
   int toInt() => value;

lib/src/utils/float_utils.dart

@@ -0,0 +1,234 @@
+/*
+ * Package : Cbor
+ * Author : S. Hamblett <steve.hamblett@linux.com>
+ * Date   : 21/01/2026
+ * Copyright :  S.Hamblett
+ */
+
+import 'dart:typed_data';
+
+/// Custom half-precision (float16) encoding/decoding that works correctly on all platforms.
+///
+/// ## Why custom implementation?
+///
+/// The ieee754 package has issues on JavaScript platforms:
+///
+/// ### Encoding (`toFloat16Bytes`)
+/// The ieee754 package uses `ByteData.setInt16()` which behaves incorrectly on JS
+/// where bitwise operators are limited to 32-bit signed integers. When the sign bit
+/// is set (negative numbers, negative zero), the value gets sign-extended incorrectly.
+///
+/// ### Decoding (`fromFloat16Bytes`)
+/// The ieee754 package uses `ByteData.getInt16()` to read the 16-bit value, which
+/// on JS interprets the bytes as a signed integer. For values with the high bit set
+/// (negative numbers, large positive exponents), this produces incorrect results.
+/// For example, -4.0 (bytes 0xC400) gets decoded as -33554428 instead of -4.0.
+///
+/// This implementation avoids these issues by:
+/// - Constructing bytes directly without using setInt16/getInt16
+/// - Using only unsigned byte operations that work consistently across platforms
+/// - Building the 16-bit value from individual bytes using shifts and OR operations
+
+/// Converts a double to IEEE 754 half-precision (16-bit) bytes in big-endian order.
+///
+/// Returns a list of 2 bytes `[highByte, lowByte]`.
+List<int> toFloat16Bytes(double value) {
+  // Handle special cases
+  if (value.isNaN) {
+    // Canonical NaN: 0x7e00
+    return [0x7e, 0x00];
+  }
+
+  if (value.isInfinite) {
+    // +Infinity: 0x7c00, -Infinity: 0xfc00
+    return value.isNegative ? [0xfc, 0x00] : [0x7c, 0x00];
+  }
+
+  // Handle zero (including signed zero)
+  if (value == 0.0) {
+    // Check for negative zero
+    final bytes = Uint8List(8);
+    ByteData.view(bytes.buffer).setFloat64(0, value, Endian.big);
+    final isNegativeZero = bytes[0] == 0x80;
+    return isNegativeZero ? [0x80, 0x00] : [0x00, 0x00];
+  }
+
+  // Extract components from double using ByteData
+  final doubleBytes = Uint8List(8);
+  ByteData.view(doubleBytes.buffer).setFloat64(0, value, Endian.big);
+
+  // Extract sign, exponent, and mantissa from IEEE 754 double (64-bit)
+  // Double format: 1 sign + 11 exponent + 52 mantissa
+  final sign = (doubleBytes[0] >> 7) & 1;
+  final exponent =
+      ((doubleBytes[0] & 0x7F) << 4) | ((doubleBytes[1] >> 4) & 0x0F);
+  // We only need the top 10 bits of the mantissa for half-precision
+  final mantissaHigh =
+      ((doubleBytes[1] & 0x0F) << 6) | ((doubleBytes[2] >> 2) & 0x3F);
+
+  // Double exponent bias is 1023, half-precision bias is 15
+  // Adjust exponent: half_exp = double_exp - 1023 + 15 = double_exp - 1008
+  final adjustedExponent = exponent - 1023 + 15;
+
+  int halfSign = sign;
+  int halfExponent;
+  int halfMantissa;
+
+  if (adjustedExponent <= 0) {
+    // Subnormal or zero in half-precision
+    if (adjustedExponent < -10) {
+      // Too small, round to zero
+      halfExponent = 0;
+      halfMantissa = 0;
+    } else {
+      // Subnormal: shift mantissa right and add implicit leading 1
+      halfExponent = 0;
+      final shift = 1 - adjustedExponent;
+      // Add implicit leading bit and shift
+      halfMantissa = (0x400 | mantissaHigh) >> shift;
+    }
+  } else if (adjustedExponent >= 31) {
+    // Overflow to infinity
+    halfExponent = 31;
+    halfMantissa = 0;
+  } else {
+    // Normal number
+    halfExponent = adjustedExponent;
+    halfMantissa = mantissaHigh;
+  }
+
+  // Construct the 16-bit half-precision value
+  // Format: 1 sign + 5 exponent + 10 mantissa
+  final halfValue = (halfSign << 15) | (halfExponent << 10) | halfMantissa;
+
+  // Return as big-endian bytes
+  return [(halfValue >> 8) & 0xFF, halfValue & 0xFF];
+}
+
+/// Check if a double can be represented losslessly as a half-precision float.
+///
+/// This is a cross-platform implementation that doesn't rely on platform-specific
+/// behavior.
+bool isFloat16Lossless(double value) {
+  // Special values are always lossless
+  if (value.isNaN || value.isInfinite || value == 0.0) {
+    return true;
+  }
+
+  // Convert to float16 and back, check if value is preserved
+  final halfBytes = toFloat16Bytes(value);
+  final reconstructed = fromFloat16Bytes(halfBytes);
+
+  return reconstructed == value;
+}
+
+/// Converts IEEE 754 half-precision (16-bit) bytes to a double.
+///
+/// Expects 2 bytes in big-endian order `[highByte, lowByte]`.
+///
+/// This is a cross-platform implementation that avoids `ByteData.getInt16()`
+/// which behaves incorrectly on JS for values with the high bit set.
+double fromFloat16Bytes(List<int> bytes) {
+  final halfValue = (bytes[0] << 8) | bytes[1];
+
+  final sign = (halfValue >> 15) & 1;
+  final exponent = (halfValue >> 10) & 0x1F;
+  final mantissa = halfValue & 0x3FF;
+
+  double result;
+
+  if (exponent == 0) {
+    if (mantissa == 0) {
+      // Zero
+      result = 0.0;
+    } else {
+      // Subnormal
+      result = mantissa / 1024.0 * (1.0 / 16384.0); // 2^-14
+    }
+  } else if (exponent == 31) {
+    if (mantissa == 0) {
+      result = double.infinity;
+    } else {
+      result = double.nan;
+    }
+  } else {
+    // Normal number
+    result = (1.0 + mantissa / 1024.0) * _pow2(exponent - 15);
+  }
+
+  return sign == 1 ? -result : result;
+}
+
+/// Power of 2 helper that avoids dart:math dependency.
+double _pow2(int exp) {
+  if (exp >= 0) {
+    double result = 1.0;
+    for (var i = 0; i < exp; i++) {
+      result *= 2.0;
+    }
+    return result;
+  } else {
+    double result = 1.0;
+    for (var i = 0; i > exp; i--) {
+      result /= 2.0;
+    }
+    return result;
+  }
+}
+
+/// Check if a double can be represented losslessly as a single-precision (32-bit) float.
+///
+/// This is a cross-platform implementation.
+bool isFloat32Lossless(double value) {
+  // Special values are always lossless
+  if (value.isNaN || value.isInfinite || value == 0.0) {
+    return true;
+  }
+
+  // Convert to float32 and back, check if value is preserved
+  final bytes = toFloat32Bytes(value);
+  final reconstructed = fromFloat32Bytes(bytes);
+
+  return reconstructed == value;
+}
+
+/// Check if a double can be represented losslessly as a double-precision (64-bit) float.
+///
+/// This always returns true since Dart doubles are already 64-bit IEEE 754 floats.
+bool isFloat64Lossless(double value) {
+  return true;
+}
+
+/// Converts a double to IEEE 754 single-precision (32-bit) bytes in big-endian order.
+///
+/// Returns a list of 4 bytes.
+List<int> toFloat32Bytes(double value) {
+  final bytes = Uint8List(4);
+  ByteData.view(bytes.buffer).setFloat32(0, value, Endian.big);
+  return bytes;
+}
+
+/// Converts IEEE 754 single-precision (32-bit) bytes to a double.
+///
+/// Expects 4 bytes in big-endian order.
+double fromFloat32Bytes(List<int> bytes) {
+  final data = ByteData.view(Uint8List.fromList(bytes).buffer);
+  return data.getFloat32(0, Endian.big);
+}
+
+/// Converts a double to IEEE 754 double-precision (64-bit) bytes in big-endian order.
+///
+/// Returns a list of 8 bytes.
+List<int> toFloat64Bytes(double value) {
+  final bytes = Uint8List(8);
+  ByteData.view(bytes.buffer).setFloat64(0, value, Endian.big);
+  return bytes;
+}
+
+/// Converts IEEE 754 double-precision (64-bit) bytes to a double.
+///
+/// Expects 8 bytes in big-endian order.
+double fromFloat64Bytes(List<int> bytes) {
+  final data = ByteData.view(Uint8List.fromList(bytes).buffer);
+  return data.getFloat64(0, Endian.big);
+}