3 files changed, 53 insertions, 0 deletions
diff --git a/base/platform_file.h b/base/platform_file.h
index 0dbf4e4..4ab1ace 100644
--- a/base/platform_file.h
+++ b/base/platform_file.h
@@ -12,6 +12,8 @@
 
 #include <string>
 
+#include "base/ref_counted.h"
+
 class FilePath;
 
 namespace base {
@@ -53,6 +55,41 @@ PlatformFile CreatePlatformFile(const std::wstring& name,
 // Closes a file handle
 bool ClosePlatformFile(PlatformFile file);
 
+// Get the length of an underlying file. Returns false on error. Otherwise
+// *size is set to the length of the file, in bytes.
+bool GetPlatformFileSize(PlatformFile file, uint64* size);
+
+// This is a reference counted PlatformFile. When the ref count drops to zero,
+// the file handle is closed. See the comments in base/ref_counted.h for
+// details on how to use it.
+class RefCountedPlatformFile :
+    public base::RefCountedThreadSafe<RefCountedPlatformFile> {
+ public:
+  RefCountedPlatformFile(PlatformFile f) : file_(f) { }
+
+  ~RefCountedPlatformFile() {
+    if (file_ != kInvalidPlatformFileValue) {
+      ClosePlatformFile(file_);
+      file_ = kInvalidPlatformFileValue;
+    }
+  }
+
+  PlatformFile get() const {
+    return file_;
+  }
+
+  PlatformFile release() {
+    PlatformFile f = file_;
+    file_ = kInvalidPlatformFileValue;
+    return f;
+  }
+
+ private:
+  PlatformFile file_;
+
+  DISALLOW_COPY_AND_ASSIGN(RefCountedPlatformFile);
+};
+
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_
diff --git a/base/platform_file_posix.cc b/base/platform_file_posix.cc
index 46039b9..bfd40e9 100644
--- a/base/platform_file_posix.cc
+++ b/base/platform_file_posix.cc
@@ -77,4 +77,12 @@ bool ClosePlatformFile(PlatformFile file) {
   return close(file);
 }
 
+bool GetPlatformFileSize(PlatformFile file, uint64* out_size) {
+  struct stat st;
+  if (fstat(file, &st))
+    return false;
+  *out_size = st.st_size;
+  return true;
+}
+
 }  // namespace base
diff --git a/base/platform_file_win.cc b/base/platform_file_win.cc
index 1143487..ccaee1e 100644
--- a/base/platform_file_win.cc
+++ b/base/platform_file_win.cc
@@ -75,4 +75,12 @@ bool ClosePlatformFile(PlatformFile file) {
   return (CloseHandle(file) == 0);
 }
 
+bool GetPlatformFileSize(PlatformFile file, uint64* out_size) {
+  LARGE_INTEGER size;
+  if (!GetFileSizeEx(file, &size))
+    return false;
+  *out_size = size.QuadPart;
+  return true;
+}
+
 }  // namespace disk_cache