1 files changed, 76 insertions, 0 deletions

diff --git a/cli/internal/cacheitem/cacheitem.go b/cli/internal/cacheitem/cacheitem.go
new file mode 100644
index 0000000..2fb2c3b
--- /dev/null
+++ b/cli/internal/cacheitem/cacheitem.go
@@ -0,0 +1,76 @@
+// Package cacheitem is an abstraction over the creation and restoration of a cache
+package cacheitem
+
+import (
+	"archive/tar"
+	"bufio"
+	"crypto/sha512"
+	"errors"
+	"io"
+	"os"
+
+	"github.com/vercel/turbo/cli/internal/turbopath"
+)
+
+var (
+	errMissingSymlinkTarget = errors.New("symlink restoration is delayed")
+	errCycleDetected        = errors.New("links in the cache are cyclic")
+	errTraversal            = errors.New("tar attempts to write outside of directory")
+	errNameMalformed        = errors.New("file name is malformed")
+	errNameWindowsUnsafe    = errors.New("file name is not Windows-safe")
+	errUnsupportedFileType  = errors.New("attempted to restore unsupported file type")
+)
+
+// CacheItem is a `tar` utility with a little bit extra.
+type CacheItem struct {
+	// Path is the location on disk for the CacheItem.
+	Path turbopath.AbsoluteSystemPath
+	// Anchor is the position on disk at which the CacheItem will be restored.
+	Anchor turbopath.AbsoluteSystemPath
+
+	// For creation.
+	tw         *tar.Writer
+	zw         io.WriteCloser
+	fileBuffer *bufio.Writer
+	handle     *os.File
+	compressed bool
+}
+
+// Close any open pipes
+func (ci *CacheItem) Close() error {
+	if ci.tw != nil {
+		if err := ci.tw.Close(); err != nil {
+			return err
+		}
+	}
+
+	if ci.zw != nil {
+		if err := ci.zw.Close(); err != nil {
+			return err
+		}
+	}
+
+	if ci.fileBuffer != nil {
+		if err := ci.fileBuffer.Flush(); err != nil {
+			return err
+		}
+	}
+
+	if ci.handle != nil {
+		if err := ci.handle.Close(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// GetSha returns the SHA-512 hash for the CacheItem.
+func (ci *CacheItem) GetSha() ([]byte, error) {
+	sha := sha512.New()
+	if _, err := io.Copy(sha, ci.handle); err != nil {
+		return nil, err
+	}
+
+	return sha.Sum(nil), nil
+}