Move Stat() into LocalPackagePool

The contents of `os.Stat` are rather fitted towards local package pools,
but the method is in the generic PackagePool interface. This moves it to
LocalPackagePool, and the use case of simply finding a file's size is
delegated to a new, more generic PackagePool.Size() method.

Signed-off-by: Ryan Gonzalez <ryan.gonzalez@collabora.com>

aptly/interfaces.go

@@ -35,8 +35,8 @@ type PackagePool interface {
 	Import(srcPath, basename string, checksums *utils.ChecksumInfo, move bool, storage ChecksumStorage) (path string, err error)
 	// LegacyPath returns legacy (pre 1.1) path to package file (relative to root)
 	LegacyPath(filename string, checksums *utils.ChecksumInfo) (string, error)
-	// Stat returns Unix stat(2) info
-	Stat(path string) (os.FileInfo, error)
+	// Size returns the size of the given file in bytes.
+	Size(path string) (size int64, err error)
 	// Open returns ReadSeekerCloser to access the file
 	Open(path string) (ReadSeekerCloser, error)
 	// FilepathList returns file paths of all the files in the pool
@@ -47,6 +47,8 @@ type PackagePool interface {
 
 // LocalPackagePool is implemented by PackagePools residing on the same filesystem
 type LocalPackagePool interface {
+	// Stat returns Unix stat(2) info
+	Stat(path string) (os.FileInfo, error)
 	// GenerateTempPath generates temporary path for download (which is fast to import into package pool later on)
 	GenerateTempPath(filename string) (string, error)
 	// Link generates hardlink to destination path

files/package_pool.go

@@ -379,6 +379,15 @@ func (pool *PackagePool) Import(srcPath, basename string, checksums *utils.Check
 	return poolPath, err
 }
 
+func (pool *PackagePool) Size(path string) (size int64, err error) {
+	stat, err := pool.Stat(path)
+	if err != nil {
+		return 0, err
+	}
+
+	return stat.Size(), nil
+}
+
 // Open returns io.ReadCloser to access the file
 func (pool *PackagePool) Open(path string) (aptly.ReadSeekerCloser, error) {
 	return os.Open(filepath.Join(pool.rootPath, path))

files/package_pool_test.go

@@ -306,6 +306,18 @@ func (s *PackagePoolSuite) TestImportOverwrite(c *C) {
 	c.Check(err, ErrorMatches, "unable to import into pool.*")
 }
 
+func (s *PackagePoolSuite) TestSize(c *C) {
+	path, err := s.pool.Import(s.debFile, filepath.Base(s.debFile), &s.checksum, false, s.cs)
+	c.Check(err, IsNil)
+
+	size, err := s.pool.Size(path)
+	c.Assert(err, IsNil)
+	c.Check(size, Equals, int64(2738))
+
+	_, err = s.pool.Size("do/es/ntexist")
+	c.Assert(os.IsNotExist(err), Equals, true)
+}
+
 func (s *PackagePoolSuite) TestStat(c *C) {
 	path, err := s.pool.Import(s.debFile, filepath.Base(s.debFile), &s.checksum, false, s.cs)
 	c.Check(err, IsNil)