From f4b0c2e93a2f45b548465dba84b257bcb3b41446 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@mit.edu>
Date: Sat, 20 Feb 2016 15:22:17 -0500
Subject: Implement unlink

---
 src/operations.cc   | 19 +++++++++++++++++++
 src/posix_extras.cc | 10 ++++++++++
 src/posix_extras.h  |  4 ++++
 3 files changed, 33 insertions(+)

diff --git a/src/operations.cc b/src/operations.cc
index 375a039..ad9f8f3 100644
--- a/src/operations.cc
+++ b/src/operations.cc
@@ -134,6 +134,24 @@ int Release(const char*, fuse_file_info* const file_info) noexcept {
   return ReleaseResource<File>(file_info->fh);
 }
 
+int Unlink(const char* c_path) noexcept {
+  try {
+    if (std::strcmp(path, "/") == 0) {
+      // Removing the root is probably a bad idea.
+      return -EPERM;
+    }
+
+    // Trim the leading slash so UnlinkAt will treat it relative to root_.
+    root_->UnlinkAt(path + 1);
+    return 0;
+  } catch (const std::system_error& e) {
+    return -e.code().value();
+  } catch (...) {
+    LOG(ERROR) << "unlink: caught unexpected value";
+    return -ENOTRECOVERABLE;
+  }
+}
+
 int Opendir(const char* const path, fuse_file_info* const file_info) noexcept {
   return OpenResource<Directory>(path, O_DIRECTORY, 0777, &file_info->fh);
 }
@@ -193,6 +211,7 @@ fuse_operations FuseOperations(File* const root) {
   result.open = &Open;
   result.create = &Create;
   result.release = &Release;
+  result.unlink = &Unlink;
 
   result.opendir = &Opendir;
   result.readdir = &Readdir;
diff --git a/src/posix_extras.cc b/src/posix_extras.cc
index 4093cc0..6844785 100644
--- a/src/posix_extras.cc
+++ b/src/posix_extras.cc
@@ -102,6 +102,16 @@ File File::OpenAt(const char* const path, const int flags,
   return result;
 }
 
+void File::UnlinkAt(const char* const path) const {
+  if (path[0] == '/') {
+    throw std::invalid_argument("absolute path");
+  }
+
+  if (unlinkat(fd_, path, 0) == -1) {
+    throw SystemError();
+  }
+}
+
 int File::Duplicate() const {
   int result;
   if ((result = dup(fd_)) == -1) {
diff --git a/src/posix_extras.h b/src/posix_extras.h
index b6dbdfd..f4e7c69 100644
--- a/src/posix_extras.h
+++ b/src/posix_extras.h
@@ -71,6 +71,10 @@ class File {
   File OpenAt(const char* path, int flags) const;
   File OpenAt(const char* path, int flags, mode_t mode) const;
 
+  // Removes the file at the path relative to the file descriptor.  The path
+  // must indeed be relative (i.e., it must not start with '/').
+  void UnlinkAt(const char* path) const;
+
  private:
   File() {}
 
-- 
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