From dd3b2d51a9612d132866df31125f474d3f83ce64 Mon Sep 17 00:00:00 2001
From: Jonas Isensee <jonas.isensee@web.de>
Date: Mon, 13 May 2024 08:45:53 +0200
Subject: [PATCH] avoid overflow in nfield loading

---
 CHANGELOG.md     |  3 +++
 Project.toml     |  2 +-
 src/datatypes.jl |  2 +-
 test/loadsave.jl | 15 +++++++++++++++
 4 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8271e426..57a60500 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+## 0.4.47
+ - fix loading structs with more than 256 fields (#558)
+
 ## 0.4.46
  - remove usage of `IOBuffer` internals
 
diff --git a/Project.toml b/Project.toml
index 21a93a92..2af0724f 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "JLD2"
 uuid = "033835bb-8acc-5ee8-8aae-3f567f8a3819"
-version = "0.4.46"
+version = "0.4.47"
 
 [deps]
 FileIO = "5789e2e9-d7fb-5bc7-8068-2c6fae9b9549"
diff --git a/src/datatypes.jl b/src/datatypes.jl
index ac1924be..0a65441d 100644
--- a/src/datatypes.jl
+++ b/src/datatypes.jl
@@ -243,7 +243,7 @@ end
 function jlread(io::IO, ::Type{CompoundDatatype})
     dt = jlread(io, BasicDatatype)
     version = dt.class >> 4
-    nfields = UInt16(dt.bitfield1) | UInt16(dt.bitfield2 << 8)
+    nfields = UInt16(dt.bitfield1) | UInt16(dt.bitfield2) << 8
     dt.bitfield3 == 0 || throw(UnsupportedFeatureException())
 
     names = Vector{Symbol}(undef, nfields)
diff --git a/test/loadsave.jl b/test/loadsave.jl
index 0ca9204b..4098fdc6 100644
--- a/test/loadsave.jl
+++ b/test/loadsave.jl
@@ -749,4 +749,19 @@ end
             @test x == f["x"]
         end
     end
+end
+
+@testset "Issue #558 a struct with 256 fields" begin
+    fields = [Symbol("field",i) for i in 1:256]
+    @eval struct Structwithmanyfields
+        $(fields...)
+    end
+    # Fill the struct
+    obj = Structwithmanyfields(ntuple(i -> i, 256)...)
+
+    cd(mktempdir()) do 
+        save_object("myStruct.jld2", obj)
+        loaded = load_object("myStruct.jld2")
+        @test loaded isa Structwithmanyfields
+    end
 end
\ No newline at end of file