1 files changed, 85 insertions, 0 deletions
diff --git a/Source/cmFilePathChecksum.cxx b/Source/cmFilePathChecksum.cxx
new file mode 100644
index 0000000..47a223a
--- /dev/null
+++ b/Source/cmFilePathChecksum.cxx
@@ -0,0 +1,85 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#include "cmFilePathChecksum.h"
+
+#include "cmBase32.h"
+#include "cmCryptoHash.h"
+#include "cmMakefile.h"
+#include "cmSystemTools.h"
+
+#include <vector>
+
+cmFilePathChecksum::cmFilePathChecksum() = default;
+
+cmFilePathChecksum::cmFilePathChecksum(std::string const& currentSrcDir,
+                                       std::string const& currentBinDir,
+                                       std::string const& projectSrcDir,
+                                       std::string const& projectBinDir)
+{
+  setupParentDirs(currentSrcDir, currentBinDir, projectSrcDir, projectBinDir);
+}
+
+cmFilePathChecksum::cmFilePathChecksum(cmMakefile* makefile)
+{
+  setupParentDirs(makefile->GetCurrentSourceDirectory(),
+                  makefile->GetCurrentBinaryDirectory(),
+                  makefile->GetHomeDirectory(),
+                  makefile->GetHomeOutputDirectory());
+}
+
+void cmFilePathChecksum::setupParentDirs(std::string const& currentSrcDir,
+                                         std::string const& currentBinDir,
+                                         std::string const& projectSrcDir,
+                                         std::string const& projectBinDir)
+{
+  this->parentDirs[0].first = cmSystemTools::GetRealPath(currentSrcDir);
+  this->parentDirs[1].first = cmSystemTools::GetRealPath(currentBinDir);
+  this->parentDirs[2].first = cmSystemTools::GetRealPath(projectSrcDir);
+  this->parentDirs[3].first = cmSystemTools::GetRealPath(projectBinDir);
+
+  this->parentDirs[0].second = "CurrentSource";
+  this->parentDirs[1].second = "CurrentBinary";
+  this->parentDirs[2].second = "ProjectSource";
+  this->parentDirs[3].second = "ProjectBinary";
+}
+
+std::string cmFilePathChecksum::get(std::string const& filePath) const
+{
+  std::string relPath;
+  std::string relSeed;
+  {
+    std::string const fileReal = cmSystemTools::GetRealPath(filePath);
+    std::string parentDir;
+    // Find closest project parent directory
+    for (auto const& pDir : this->parentDirs) {
+      if (!pDir.first.empty() &&
+          cmsys::SystemTools::IsSubDirectory(fileReal, pDir.first)) {
+        parentDir = pDir.first;
+        relSeed = pDir.second;
+        break;
+      }
+    }
+    // Use file system root as fallback parent directory
+    if (parentDir.empty()) {
+      relSeed = "FileSystemRoot";
+      cmsys::SystemTools::SplitPathRootComponent(fileReal, &parentDir);
+    }
+    // Calculate relative path from project parent directory
+    relPath = cmsys::SystemTools::RelativePath(
+      parentDir, cmsys::SystemTools::GetParentDirectory(fileReal));
+  }
+
+  // Calculate the file ( seed + relative path ) binary checksum
+  std::vector<unsigned char> hashBytes =
+    cmCryptoHash(cmCryptoHash::AlgoSHA256).ByteHashString(relSeed + relPath);
+
+  // Convert binary checksum to string
+  return cmBase32Encoder().encodeString(hashBytes.data(), hashBytes.size(),
+                                        false);
+}
+
+std::string cmFilePathChecksum::getPart(std::string const& filePath,
+                                        size_t length) const
+{
+  return get(filePath).substr(0, length);
+}