From 1615359503505ca22dc3070d88325b0d47255019 Mon Sep 17 00:00:00 2001
From: Steve Lhomme <slhomme@matroska.org>
Date: Sat, 13 Jan 2024 17:06:50 +0100
Subject: [PATCH 1/3] implement EbmlMaster::ReadData

It's easier to use than Read().
---
 src/EbmlMaster.cpp | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/EbmlMaster.cpp b/src/EbmlMaster.cpp
index 91eaaff3..14084644 100644
--- a/src/EbmlMaster.cpp
+++ b/src/EbmlMaster.cpp
@@ -130,12 +130,16 @@ filepos_t EbmlMaster::WriteHead(IOCallback & output, int nSizeLength, ShouldWrit
   return RenderHead(output, false, writeFilter);
 }
 
-/*!
-  \todo this code is very suspicious !
-*/
-filepos_t EbmlMaster::ReadData(IOCallback & input, ScopeMode /* ReadFully */)
+filepos_t EbmlMaster::ReadData(IOCallback & input, ScopeMode scope)
 {
-  input.setFilePointer(GetSize(), seek_current);
+  int upper = 0;
+  EbmlStream aStream(input);
+  EbmlElement *Parent = nullptr;
+  Read(aStream, Context(), upper, Parent, false, scope);
+  assert(Parent == nullptr);
+  assert(upper == 0);
+
+  input.setFilePointer(GetEndPosition(), seek_beginning);
   return GetSize();
 }
 

From cca5c8ca6f12368f585b5fdb10477db5be8f7e91 Mon Sep 17 00:00:00 2001
From: Steve Lhomme <slhomme@matroska.org>
Date: Sat, 13 Jan 2024 17:09:56 +0100
Subject: [PATCH 2/3] add a test writing+verifying the checksum

---
 CMakeLists.txt    |  4 ++++
 test/test_crc.cxx | 61 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 test/test_crc.cxx

diff --git a/CMakeLists.txt b/CMakeLists.txt
index cb825519..49de3478 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -148,6 +148,10 @@ if (BUILD_TESTING)
   target_link_libraries(test_macros PUBLIC ebml)
   add_test(test_macros test_macros)
 
+  add_executable(test_crc test/test_crc.cxx)
+  target_link_libraries(test_crc PUBLIC ebml)
+  add_test(test_crc test_crc)
+
 endif(BUILD_TESTING)
 
 
diff --git a/test/test_crc.cxx b/test/test_crc.cxx
new file mode 100644
index 00000000..a42756f7
--- /dev/null
+++ b/test/test_crc.cxx
@@ -0,0 +1,61 @@
+// Copyright © 2024 Steve Lhomme.
+// SPDX-License-Identifier: ISC
+
+#include <ebml/EbmlHead.h>
+#include <ebml/EbmlSubHead.h>
+#include <ebml/EbmlMaster.h>
+#include <ebml/EbmlStream.h>
+#include <ebml/MemIOCallback.h>
+
+int main(int /*argc*/, char** /*argv*/)
+{
+    ///// Writing test
+    libebml::MemIOCallback Ebml_file;
+    libebml::EbmlHead TestHead;
+
+    TestHead.EnableChecksum();
+
+    libebml::EDocTypeVersion & MyDocTypeVer = libebml::GetChild<libebml::EDocTypeVersion>(TestHead);
+    MyDocTypeVer.SetValue(1);
+
+    libebml::GetChild<libebml::EMaxSizeLength>(TestHead).SetValue(7);
+
+    auto length = TestHead.Render(Ebml_file, libebml::EbmlElement::WriteAll);
+    if (length != 46)
+        return 1;
+
+    ///// Reading test
+    Ebml_file.setFilePointer(0);
+    libebml::EbmlStream aStream(Ebml_file);
+    libebml::EbmlElement * ElementLevel0;
+
+    // find the EBML head in the file
+    ElementLevel0 = aStream.FindNextID(EBML_INFO(libebml::EbmlHead), 0xFFFFFFFFL);
+    if (ElementLevel0 == nullptr)
+        return 1;
+
+    if (ElementLevel0->GetClassId() != libebml::EbmlHead::ClassId())
+        return 1;
+
+    libebml::EbmlHead &ReadHead = static_cast<libebml::EbmlHead &>(*ElementLevel0);
+
+    ReadHead.ReadData(aStream, libebml::SCOPE_ALL_DATA);
+
+    if (!ReadHead.VerifyChecksum())
+        return 1;
+
+    libebml::EDocType & ReadDocType = libebml::GetChild<libebml::EDocType>(ReadHead);
+    const std::string & DocTypeStr = static_cast<const std::string &>(ReadDocType);
+    if (DocTypeStr != "matroska")
+        return 1;
+
+    auto & ReadReadVersion = libebml::GetChild<const libebml::EDocTypeReadVersion>(ReadHead);
+    if (static_cast<std::uint64_t>(ReadReadVersion) != 1)
+        return 1;
+
+    auto & ReadMaxLength = libebml::GetChild<const libebml::EMaxSizeLength>(ReadHead);
+    if (static_cast<std::uint64_t>(ReadMaxLength) != 7)
+        return 1;
+
+    return 0;
+}

From afc410dfde06d53629d4aa1f736d9f8ebb616ff3 Mon Sep 17 00:00:00 2001
From: Steve Lhomme <slhomme@matroska.org>
Date: Sat, 13 Jan 2024 17:10:17 +0100
Subject: [PATCH 3/3] check the checksum API works when there is no checksum
 written

---
 test/test_header.cxx | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test/test_header.cxx b/test/test_header.cxx
index c8aa33d1..f52eb7b2 100644
--- a/test/test_header.cxx
+++ b/test/test_header.cxx
@@ -49,6 +49,9 @@ int main(int /*argc*/, char** /*argv*/)
     if (upper != 0)
         return 1;
 
+    if (!ReadHead.VerifyChecksum())
+        return 1;
+
     libebml::EDocType & ReadDocType = libebml::GetChild<libebml::EDocType>(ReadHead);
     const std::string & DocTypeStr = static_cast<const std::string &>(ReadDocType);
     if (DocTypeStr != "webm")