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Refactor JSON serialization and escape handling #425

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273a6e4
Refactor JSON serialization and escape handling
networkfusion Oct 30, 2025
6c252f6
Merge branch 'main' into networkfusion-fix-1682
networkfusion Oct 30, 2025
a35f50f
Improve XML documentation for JsonConvert
networkfusion Oct 30, 2025
f0aa4bb
Update JsonSerializerOptionsTests.cs
networkfusion Nov 5, 2025
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26 changes: 26 additions & 0 deletions nanoFramework.Json.Test/JsonSerializerOptionsTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,32 @@ public void Can_serialize_and_deserialize_arrays_of_class_objects()
OutputHelper.WriteLine("");
}

[TestMethod]
public void Can_deserialize_string_starting_with_unicode_escape()
{

OutputHelper.WriteLine("Starting test...");

Console.WriteLine($"{TimeSpan.FromHours(1).TotalMilliseconds}");

JsonTestCompany test = new JsonTestCompany
{
CompanyID = 10,
CompanyName = "5 Guys"
};

var jsonString = "{\u0022CompanyID\u0022:10,\u0022CompanyName\u0022:\u00225 Guys\u0022}";


JsonTestCompany deserializedResult = (JsonTestCompany)JsonConvert.DeserializeObject(jsonString, typeof(JsonTestCompany));

Assert.NotNull(deserializedResult);
Assert.Equal("5 Guys", deserializedResult.CompanyName);
Assert.Equal(10, deserializedResult.CompanyID);

OutputHelper.WriteLine("Finished test...");
}

[TestMethod]
public void Can_serialize_and_deserialize_arrays_of_class_objects_when_array_items_may_be_null()
{
Expand Down
81 changes: 33 additions & 48 deletions nanoFramework.Json/JsonConvert.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,10 @@ private struct LexToken
/// <summary>
/// Convert an object to a JSON string.
/// </summary>
/// <param name="oSource">The value to convert. Supported types are: Boolean, String, Byte, (U)Int16, (U)Int32, Float, Double, Decimal, Array, IDictionary, IEnumerable, Guid, Datetime, DictionaryEntry, Object and null.</param>
/// <param name="oSource">
/// The value to convert. Supported types are: Boolean, String, Byte, (U)Int16, (U)Int32,
/// Float, Double, Decimal, Array, IDictionary, IEnumerable, Guid, Datetime, DictionaryEntry, Object and null.
/// </param>
/// <returns>The JSON object as a string or null when the value type is not supported.</returns>
/// <remarks>For objects, only public properties with getters are converted.</remarks>
public static string SerializeObject(object oSource)
Expand Down Expand Up @@ -1088,7 +1091,7 @@ private static LexToken GetNextTokenInternal(ref int jsonPos, ref byte[] jsonByt
return EndToken(sb);
}

//TODO: replace with a mapping array? This switch is really incomplete.
// handle escaped characters
switch (ch)
{
case 't':
Expand All @@ -1115,15 +1118,21 @@ private static LexToken GetNextTokenInternal(ref int jsonPos, ref byte[] jsonByt
ch = '\\';
break;

case 'u':
unicodeEncoded = true;
break;

case '"':
ch = '"';
break;

case '\'':
ch = '\'';
break;

case 'u':
// unicode escape \uXXXX - we'll handle below
unicodeEncoded = true;
break;

default:
// unknown escape sequence
throw new DeserializationException();
}
}
Expand All @@ -1132,56 +1141,32 @@ private static LexToken GetNextTokenInternal(ref int jsonPos, ref byte[] jsonByt
{
if (unicodeEncoded)
{
int numberCounter = 0;

// next 4 chars have to be numeric
StringBuilder encodedValue = new();

// advance position to next char
jsonPos++;
ch = (char)jsonBytes[jsonPos];

for (int i = 0; i < 4; i++)
// We must decode exactly 4 hex digits following the '\u'
// Ensure there are at least 4 bytes remaining
if (jsonPos + 4 > jsonBytes.Length)
{
if (IsNumberChar(ch))
{
numberCounter++;

encodedValue.Append(ch);

ch = (char)jsonBytes[jsonPos];

if (IsNumberChar(ch))
{
// We're still working on the number - advance jsonPos
jsonPos++;
}
}
throw new DeserializationException();
}

if (numberCounter == 4)
// Read 4 ASCII hex chars (they should be ASCII hex digits)
int val = 0;
for (int i = 0; i < 4; i++)
{
// we're good with the encoded data
// try parse number as an UTF-8 char
try
{
// NOTE: the encoded value has hexadecimal format
int unicodeChar = Convert.ToInt16(encodedValue.ToString(), 16);

_ = sb.Append((char)unicodeChar);
}
catch
char hc = (char)jsonBytes[jsonPos++];
int digit;
if (hc >= '0' && hc <= '9') digit = hc - '0';
else if (hc >= 'a' && hc <= 'f') digit = 10 + (hc - 'a');
else if (hc >= 'A' && hc <= 'F') digit = 10 + (hc - 'A');
else
{
// couldn't parse this number as a valid Unicode value
throw new DeserializationException();
}

val = (val << 4) + digit;
}
else
{
// anything else, we can't parse it properly
// throw exception
throw new DeserializationException();
}

// Append the decoded unicode character
sb.Append((char)val);
}
else
{
Expand Down
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