From 29e38253b57823cc386c6b483439e6016730cdec Mon Sep 17 00:00:00 2001
From: Michael Hebert <mike@inkbit3d.com>
Date: Thu, 2 Jan 2025 10:29:09 -0500
Subject: [PATCH 1/2] Add test for binary STLs with 'solid' header and fix
 STLDocument

---
 src/STLDocument.cs                   |  31 ++++++++++++---------------
 tests/Data/BinaryWithSolidHeader.stl | Bin 0 -> 684 bytes
 tests/STLDocumentTests.cs            |  13 +++++++++++
 3 files changed, 27 insertions(+), 17 deletions(-)
 create mode 100644 tests/Data/BinaryWithSolidHeader.stl

diff --git a/src/STLDocument.cs b/src/STLDocument.cs
index db9d317..0db288b 100644
--- a/src/STLDocument.cs
+++ b/src/STLDocument.cs
@@ -125,22 +125,7 @@ public void AppendFacets(IEnumerable<Facet> facets)
         /// <returns>True if the <see cref="STLDocument"/> is text-based, otherwise false.</returns>
         public static bool IsText(Stream stream)
         {
-            if (stream == null) throw new NullReferenceException(nameof(stream));
-
-            const string solid = "solid";
-
-            byte[] buffer = new byte[5];
-            string header;
-
-            // Reset the stream to tbe beginning and read the first few bytes, then reset the stream to the beginning again.
-            stream.Seek(0, SeekOrigin.Begin);
-            stream.Read(buffer, 0, buffer.Length);
-            stream.Seek(0, SeekOrigin.Begin);
-
-            // Read the header as ASCII.
-            header = Encoding.ASCII.GetString(buffer);
-
-            return solid.Equals(header, StringComparison.InvariantCultureIgnoreCase);
+            return !IsBinary(stream);
         }
 
         /// <summary>Determines if the <see cref="STLDocument"/> contained within the <paramref name="stream"/> is binary-based.</summary>
@@ -149,7 +134,19 @@ public static bool IsText(Stream stream)
         /// <returns>True if the <see cref="STLDocument"/> is binary-based, otherwise false.</returns>
         public static bool IsBinary(Stream stream)
         {
-            return !IsText(stream);
+            if (stream == null) throw new NullReferenceException(nameof(stream));
+
+            using var reader = new BinaryReader(stream, Encoding.Default, true);
+
+            stream.Seek(80, SeekOrigin.Begin);
+
+            var numTriangles = reader.ReadUInt32();
+
+            var expectedSize = 84 + numTriangles * 50;
+
+            stream.Seek(0, SeekOrigin.Begin);
+
+            return stream.Length == expectedSize;
         }
 
         /// <summary>Reads the <see cref="STLDocument"/> contained within the <paramref name="stream"/> into a new <see cref="STLDocument"/>.</summary>
diff --git a/tests/Data/BinaryWithSolidHeader.stl b/tests/Data/BinaryWithSolidHeader.stl
new file mode 100644
index 0000000000000000000000000000000000000000..2b6574634474680940996aa6490b124d58fe1c97
GIT binary patch
literal 684
zcmb`BO$vih5Q9BH58+L`OKTT}LKmfbZ|2pUFZ1I=9@2$@ktCCh@B4Yb=JD~nKgUaO
z8(J)rsnth3baB(-Rq8e}#iitXBV7Fl7tMg&xr*<SZZ9=ih!K=bLAq@iuh&{bd^l}n
ziYvw)-V1?iTY15?fiuEsBU91Xv-Psojxd1Kf&bS~DlRn*?g2K&wZS`ZB97{I8cKu@
F-vBtiNx=XB

literal 0
HcmV?d00001

diff --git a/tests/STLDocumentTests.cs b/tests/STLDocumentTests.cs
index f6692d9..93e9e97 100644
--- a/tests/STLDocumentTests.cs
+++ b/tests/STLDocumentTests.cs
@@ -33,6 +33,19 @@ public void Read__FromBinaryStream()
             ValidateSTL(stlBinary);
         }
 
+        [Fact]
+        public void Read__FromBinaryStreamWithSolidHeader()
+        {
+            STLDocument stlBinary;
+
+            using (var stream = GetData("BinaryWithSolidHeader.stl"))
+            {
+                stlBinary = STLDocument.Read(stream);
+            }
+
+            ValidateSTL(stlBinary);
+        }
+
         [Fact]
         public void Read__FromTextReader()
         {

From 61a51b8fb3883e809c1a98bdfcdb1b727d140fc9 Mon Sep 17 00:00:00 2001
From: Josh McCullough <JoshMcCullough@users.noreply.github.com>
Date: Thu, 2 Jan 2025 15:30:22 -0500
Subject: [PATCH 2/2] rm line break

---
 src/STLDocument.cs | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/STLDocument.cs b/src/STLDocument.cs
index 0db288b..c5b729c 100644
--- a/src/STLDocument.cs
+++ b/src/STLDocument.cs
@@ -140,9 +140,8 @@ public static bool IsBinary(Stream stream)
 
             stream.Seek(80, SeekOrigin.Begin);
 
-            var numTriangles = reader.ReadUInt32();
-
-            var expectedSize = 84 + numTriangles * 50;
+            const numTriangles = reader.ReadUInt32();
+            const expectedSize = 84 + numTriangles * 50;
 
             stream.Seek(0, SeekOrigin.Begin);