FileInterface: Implement GetSize().

Implemented a method to get the size of the FileInterface object
directly.

Bug: 24478450
Change-Id: I9aab80b33cc554551ce79bfee52e94e8e04775db
Test: make all test && ./unittest

6 files changed, 56 insertions, 0 deletions

diff --git a/extents_file.cc b/extents_file.cc
index fc4a10d..2d2ea83 100644
--- a/extents_file.cc
+++ b/extents_file.cc
@@ -62,6 +62,11 @@ bool ExtentsFile::Close() {
   return file_->Close();
 }
 
+bool ExtentsFile::GetSize(uint64_t* size) {
+  *size = total_ex_len_;
+  return true;
+}
+
 void ExtentsFile::AdvancePos(uint64_t size) {
   curr_pos_ += size;
   for (; curr_ex_idx_ < extents_.size(); curr_ex_idx_++) {
diff --git a/extents_file.h b/extents_file.h
index a8007dd..865e2a2 100644
--- a/extents_file.h
+++ b/extents_file.h
@@ -53,6 +53,7 @@ class ExtentsFile : public FileInterface {
   bool Write(const void* buf, size_t count, size_t* bytes_written) override;
   bool Seek(off_t pos) override;
   bool Close() override;
+  bool GetSize(uint64_t* size) override;
 
  private:
   void AdvancePos(uint64_t size);
diff --git a/extents_file_unittest.cc b/extents_file_unittest.cc
index 206328c..fa9ed22 100644
--- a/extents_file_unittest.cc
+++ b/extents_file_unittest.cc
@@ -28,6 +28,7 @@ class MockFile : public FileInterface {
   MOCK_METHOD3(Write, bool(const void*, size_t, size_t*));
   MOCK_METHOD1(Seek, bool(off_t));
   MOCK_METHOD0(Close, bool());
+  MOCK_METHOD1(GetSize, bool(uint64_t*));
 };
 
 ACTION(SucceedIO) {
@@ -67,6 +68,14 @@ TEST_F(ExtentsFileTest, CloseIsForwarded) {
   EXPECT_CALL(*mock_file_, Close()).WillOnce(Return(false));
 }
 
+TEST_F(ExtentsFileTest, GetSizeSumExtents) {
+  ExtentsFile file(std::move(mock_file_ptr_),
+                   {ex_t{10, 5}, ex_t{20, 5}, {25, 2}});
+  uint64_t size;
+  EXPECT_TRUE(file.GetSize(&size));
+  EXPECT_EQ(12U, size);
+}
+
 TEST_F(ExtentsFileTest, SeekToRightOffsets) {
   ExtentsFile file(std::move(mock_file_ptr_),
                    {ex_t{10, 5}, ex_t{20, 5}, {25, 2}});
diff --git a/file.cc b/file.cc
index 972273a..2eebc4d 100644
--- a/file.cc
+++ b/file.cc
@@ -6,6 +6,9 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#ifdef __linux__
+#include <linux/fs.h>
+#endif  // __linux__
 #include <string.h>
 #include <sys/ioctl.h>
 #include <sys/stat.h>
@@ -88,6 +91,39 @@ bool File::Close() {
   return success;
 }
 
+bool File::GetSize(uint64_t* size) {
+  struct stat stbuf;
+  if (fstat(fd_, &stbuf) == -1)
+    return false;
+  if (S_ISREG(stbuf.st_mode)) {
+    return stbuf.st_size;
+  }
+  if (S_ISBLK(stbuf.st_mode)) {
+#if defined(BLKGETSIZE64)
+    return ioctl(fd_, BLKGETSIZE64, size);
+#elif defined(DKIOCGETBLOCKCOUNT)
+    uint64_t sectors = 0;
+    if (ioctl(fd_, DKIOCGETBLOCKCOUNT, &sectors) == 0) {
+      *size = sectors << 9;
+      return true;
+    }
+    return false;
+#else
+    // Fall back to doing seeks to know the EOF.
+    off_t pos = lseek(fd_, 0, SEEK_CUR);
+    if (pos == -1)
+      return false;
+    off_t end_pos = lseek(fd_, 0, SEEK_END);
+    if (end_pos == -1)
+      return false;
+    *size = end_pos;
+    lseek(fd_, 0, SEEK_END);
+    return true;
+#endif
+  }
+  return false;
+}
+
 File::File(int fd)
     : fd_(fd) {}
 
diff --git a/file.h b/file.h
index 00cd638..e9659c7 100644
--- a/file.h
+++ b/file.h
@@ -24,6 +24,7 @@ class File : public FileInterface {
   bool Write(const void* buf, size_t count, size_t* bytes_written) override;
   bool Seek(off_t pos) override;
   bool Close() override;
+  bool GetSize(uint64_t* size) override;
 
  private:
   // Creates the File instance for the |fd|. Takes ownership of the file
diff --git a/file_interface.h b/file_interface.h
index b32115a..a643f45 100644
--- a/file_interface.h
+++ b/file_interface.h
@@ -35,6 +35,10 @@ class FileInterface {
   // succeeded.
   virtual bool Close() = 0;
 
+  // Compute the size of the file and store it in |size|. Returns whether it
+  // computed the size successfully.
+  virtual bool GetSize(uint64_t* size) = 0;
+
  protected:
   FileInterface() = default;
 };