From 59abd82fe5c4b394677c98e168305d3cd42dc02c Mon Sep 17 00:00:00 2001
From: Devon Govett <devongovett@gmail.com>
Date: Wed, 13 Mar 2019 23:39:52 -0700
Subject: [PATCH] Brute force tree walking implementation for linux

---
 binding.gyp      | 14 +++++++-
 src/DirTree.hh   | 90 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/Event.hh     |  2 +-
 src/unix/nftw.cc | 36 +++++++++++++++++++
 4 files changed, 140 insertions(+), 2 deletions(-)
 create mode 100644 src/DirTree.hh
 create mode 100644 src/unix/nftw.cc

diff --git a/binding.gyp b/binding.gyp
index 6d615134..1212e454 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -8,10 +8,22 @@
       ],
       "conditions": [
         ['OS=="mac"', {
-          "sources": ["src/macos/FSEvents.cc"],
+          "variables": {
+            "use_nftw%": "false"
+          },
+          "conditions": [
+            ['use_nftw=="true"', {
+              "sources": ["src/unix/nftw.cc"]
+            }, {
+              "sources": ["src/macos/FSEvents.cc"],
+            }]
+          ],
           "link_settings": {
             "libraries": ["CoreServices.framework"]
           }
+        }],
+        ['OS=="linux"', {
+          "sources": ["src/unix/nftw.cc"]
         }]
       ]
     }
diff --git a/src/DirTree.hh b/src/DirTree.hh
new file mode 100644
index 00000000..d101f44a
--- /dev/null
+++ b/src/DirTree.hh
@@ -0,0 +1,90 @@
+#ifndef DIR_TREE_H
+#define DIR_TREE_H
+
+#include <string>
+#include <unordered_set>
+#include <ostream>
+#include <istream>
+#include "Event.hh"
+
+struct DirEntry {
+  std::string path;
+  time_t mtime;
+
+  DirEntry(const char *p, const struct stat *info) {
+    path.assign(p);
+    mtime = info->st_mtime;
+  }
+  
+  DirEntry(std::istream &stream) {
+    size_t size;
+
+    if (stream >> size) {
+      path.resize(size);
+      if (stream.read(&path[0], size)) {
+        stream >> mtime;
+      }
+    }
+  }
+
+  bool operator==(const DirEntry &other) const {
+    return path == other.path;
+  }
+
+  void write(std::ostream &stream) const {
+    stream << path.size() << path << mtime << "\n";
+  }
+};
+
+namespace std {
+  template <>
+  struct hash<DirEntry> {
+    std::size_t operator()(const DirEntry& k) const {
+      return hash<string>()(k.path);
+    }
+  };
+}
+
+struct DirTree {
+  std::unordered_set<DirEntry> entries;
+  DirTree() {}
+
+  DirTree(std::istream &stream) {
+    size_t size;
+    if (stream >> size) {
+      for (size_t i = 0; i < size; i++) {
+        entries.insert(DirEntry(stream));
+      }
+    }
+  }
+
+  void write(std::ostream &stream) {
+    stream << entries.size() << "\n";
+    for (auto it = entries.begin(); it != entries.end(); it++) {
+      it->write(stream);
+    }
+  }
+
+  EventList *getChanges(DirTree *snapshot) {
+    EventList *events = new EventList();
+    for (auto it = entries.begin(); it != entries.end(); it++) {
+      auto found = snapshot->entries.find(*it);
+      if (found == snapshot->entries.end()) {
+        events->push(it->path, "create");
+      } else if (found->mtime != it->mtime) {
+        events->push(it->path, "update");
+      }
+    }
+
+    for (auto it = snapshot->entries.begin(); it != snapshot->entries.end(); it++) {
+      size_t count = entries.count(*it);
+      if (count == 0) {
+        events->push(it->path, "delete");
+      }
+    }
+
+    return events;
+  }
+};
+
+#endif
diff --git a/src/Event.hh b/src/Event.hh
index d1a80ae7..a03da724 100644
--- a/src/Event.hh
+++ b/src/Event.hh
@@ -42,7 +42,7 @@ public:
       arr->Set(i, mEvents[i]->toJS());
     }
 
-     return scope.Escape(arr);
+    return scope.Escape(arr);
   }
 };
 
diff --git a/src/unix/nftw.cc b/src/unix/nftw.cc
new file mode 100644
index 00000000..1cf6aa9e
--- /dev/null
+++ b/src/unix/nftw.cc
@@ -0,0 +1,36 @@
+#include <string>
+#include <sstream>
+#include <ftw.h>
+#include "../DirTree.hh"
+#include "../Event.hh"
+
+static DirTree *tree;
+int addEntry(const char *path, const struct stat *info, const int flags, struct FTW *ftw) {
+  tree->entries.insert(DirEntry(path, info));
+  return 0;
+}
+
+DirTree *getDirTree(std::string *dir) {
+  tree = new DirTree();
+  int result = nftw(dir->c_str(), &addEntry, 15, FTW_PHYS);
+  if (result < 0) {
+    printf("error\n");
+  }
+
+  return tree;
+}
+
+std::string getCurrentTokenImpl(std::string *dir) {
+  auto tree = getDirTree(dir);
+  std::ostringstream os;
+  tree->write(os);
+  return os.str();
+}
+
+EventList *getEventsSinceImpl(std::string *dir, std::string *token) {
+  std::istringstream is(*token);
+  auto snapshot = new DirTree(is);
+  auto now = getDirTree(dir);
+
+  return now->getChanges(snapshot);
+}