Add fuzz test

.gitignore

@@ -1,6 +1,7 @@
 nimcache
 *.exe
 nimble.develop
-nimble.paths
+nimble-win.paths
+nimble-linux.paths
 build/
 vendor/

config.nims

@@ -8,6 +8,14 @@
 # those terms.
 
 # begin Nimble config (version 1)
-when fileExists("nimble.paths"):
-  include "nimble.paths"
+when defined(windows):
+  when fileExists("nimble-win.paths"):
+    include "nimble-win.paths"
+  elif fileExists("nimble.paths"):
+    include "nimble.paths"
+elif defined(linux):
+  when fileExists("nimble-win.paths"):
+    include "nimble-linux.paths"
+  elif fileExists("nimble.paths"):
+    include "nimble.paths"
 # end Nimble config

fuzzer/fuzz_lexer.nim

@@ -0,0 +1,23 @@
+# json-serialization
+# Copyright (c) 2023 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+# at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
+import
+  testutils/fuzzing,
+  faststreams,
+  ../json_serialization/lexer
+
+template prepareLexer(T: type, payload: untyped) =
+  var stream = unsafeMemoryInput(payload)
+  var lex = init(JsonLexer, stream)
+  var value: JsonValueRef[T]
+  lex.scanValue(value)
+
+test:
+  prepareLexer(string, payload)
+  prepareLexer(uint64, payload)

fuzzer/fuzz_parser.nim

@@ -0,0 +1,29 @@
+# json-serialization
+# Copyright (c) 2023 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+# at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
+import
+  testutils/fuzzing,
+  faststreams,
+  ../json_serialization/parser
+
+func toReader(input: openArray[byte]): JsonReader[DefaultFlavor] =
+  var stream = unsafeMemoryInput(input)
+  JsonReader[DefaultFlavor].init(stream)
+
+proc executeParser(payload: openArray[byte]) =
+  try:
+    var r = toReader(payload)
+    let z = r.parseValue(uint64)
+    discard z
+  except JsonReaderError:
+    discard
+    
+test:  
+  executeParser(payload)
+  

fuzzer/readme.md

@@ -0,0 +1,36 @@
+## Fuzz test manual
+
+You need to install [testutils](https://github.com/status-im/nim-testutils) and
+[chronicles](https://github.com/status-im/nim-chronicles).
+Then read documentation over there to prepare your execution environment.
+
+### Compatibility
+
+These fuzzers can be compiled with Nim v1.6.16 or newer.
+
+### Available fuzz test
+
+* fuzz_lexer
+* fuzz_parser
+
+### Manually with libFuzzer/llvmFuzer
+#### Compiling
+```sh
+nim c -d:llvmFuzzer -d:release -d:chronicles_log_level=FATAL --noMain --cc=clang --passC="-fsanitize=fuzzer" --passL="-fsanitize=fuzzer" fuzzer/fuzz_lexer
+```
+
+#### Starting the Fuzzer
+Starting the fuzzer is as simple as running the compiled program:
+```sh
+./fuzz_lexer corpus_dir -runs=1000000
+```
+
+To see the available options:
+```sh
+./fuzz_lexer test=1
+```
+
+You can also use the application to verify a specific test case:
+```sh
+./fuzz_lexer input_file
+```

json_serialization.nimble

@@ -14,7 +14,7 @@ version       = "0.2.0"
 author        = "Status Research & Development GmbH"
 description   = "Flexible JSON serialization not relying on run-time type information"
 license       = "Apache License 2.0"
-skipDirs      = @["tests"]
+skipDirs      = @["tests", "fuzzer"]
 
 requires "nim >= 1.6.0",
          "serialization",