From 273ed4f9042fbdb8fc4f8335638b09058bb5def0 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@mit.edu>
Date: Sun, 21 Feb 2016 20:03:36 -0500
Subject: Implement write

---
 src/operations.cc   | 18 +++++++++++++++++-
 src/posix_extras.cc | 15 +++++++++++++++
 src/posix_extras.h  |  5 +++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/src/operations.cc b/src/operations.cc
index 4428632..b62fdf0 100644
--- a/src/operations.cc
+++ b/src/operations.cc
@@ -157,7 +157,22 @@ int Read(const char*, char* const buffer, const size_t bytes,
   }
 }
 
-int Utimens(const char* const path, const timespec times[2]) noexcept {
+int Write(const char*, const char* const buffer, const size_t bytes,
+          const off_t offset, fuse_file_info* const file_info) noexcept {
+  try {
+    auto* const file = reinterpret_cast<File*>(file_info->fh);
+    const std::vector<std::uint8_t> to_write(buffer, buffer + bytes);
+    file->Write(offset, to_write);
+    return static_cast<int>(bytes);
+  } catch (const std::system_error& e) {
+    return -e.code().value();
+  } catch (...) {
+    LOG(ERROR) << "read: caught unexpected value";
+    return -ENOTRECOVERABLE;
+  }
+}
+
+int Utimens(const char* const c_path, const timespec times[2]) noexcept {
   try {
     const std::string path(c_path);
     root_->UTimeNs(path == "/" ? "." : EncodePath(path).c_str(), times[0],
@@ -254,6 +269,7 @@ fuse_operations FuseOperations(File* const root) {
   result.mknod = &Mknod;
   result.open = &Open;
   result.read = &Read;
+  result.write = &Write;
   result.utimens = &Utimens;
   result.release = &Release;
   result.unlink = &Unlink;
diff --git a/src/posix_extras.cc b/src/posix_extras.cc
index ac6e3b2..7b82f0a 100644
--- a/src/posix_extras.cc
+++ b/src/posix_extras.cc
@@ -141,6 +141,21 @@ void File::UTimeNs(const char* const path, const timespec& access,
   }
 }
 
+size_t File::Write(const off_t offset,
+                   const std::vector<std::uint8_t>& to_write) {
+  size_t bytes_written = 0;
+  while (bytes_written < to_write.size()) {
+    const ssize_t pwrite_result = pwrite(
+        fd_, to_write.data() + bytes_written, to_write.size() - bytes_written,
+        offset + static_cast<off_t>(bytes_written));
+    if (pwrite_result == -1) {
+      throw SystemError();
+    }
+    bytes_written += static_cast<size_t>(pwrite_result);
+  }
+  return bytes_written;
+}
+
 int File::Duplicate() const {
   int result;
   if ((result = dup(fd_)) == -1) {
diff --git a/src/posix_extras.h b/src/posix_extras.h
index 5571da6..f92bff7 100644
--- a/src/posix_extras.h
+++ b/src/posix_extras.h
@@ -95,6 +95,11 @@ class File {
   void UTimeNs(const char* path, const timespec& access,
                const timespec& modification) const;
 
+  // Writes the specified byte vector to the file at the given offset.  Returns
+  // the number of bytes written, which will always be the number of bytes given
+  // as input.
+  size_t Write(off_t, const std::vector<std::uint8_t>&);
+
  private:
   File() {}
 
-- 
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