From 7ccbb9d40cf1cbdbcf96bbc06da2d1614ee6f5f1 Mon Sep 17 00:00:00 2001
From: Vincent Batts <vbatts@hashbangbash.com>
Date: Tue, 24 Feb 2015 17:07:00 -0500
Subject: [PATCH] tar/asm: initial assmebly of tar stream

---
 tar/asm/README.md   | 18 +++++++++++++++
 tar/asm/assemble.go | 53 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)
 create mode 100644 tar/asm/README.md
 create mode 100644 tar/asm/assemble.go

diff --git a/tar/asm/README.md b/tar/asm/README.md
new file mode 100644
index 0000000..dd9d1e8
--- /dev/null
+++ b/tar/asm/README.md
@@ -0,0 +1,18 @@
+asm
+===
+
+This library for assembly and disassembly of tar archives, facilitated by
+`github.com/vbatts/tar-split/tar/storage`.
+
+
+
+Thoughts
+--------
+
+While the initial implementation is based on a relative path, I'm thinking the
+next step is to have something like a FileGetter interface, of which a path
+based getter is just one type.
+
+Then you could pass a path based Getter and an Unpacker, and receive a
+io.Reader that is your tar stream.
+
diff --git a/tar/asm/assemble.go b/tar/asm/assemble.go
new file mode 100644
index 0000000..7f87bc3
--- /dev/null
+++ b/tar/asm/assemble.go
@@ -0,0 +1,53 @@
+package asm
+
+import (
+	"io"
+	"os"
+	"path"
+
+	"github.com/vbatts/tar-split/tar/storage"
+)
+
+func NewTarStream(relpath string, up storage.Unpacker) io.ReadCloser {
+	pr, pw := io.Pipe()
+	go func() {
+		for {
+			entry, err := up.Next()
+			if err != nil {
+				pw.CloseWithError(err)
+				break
+			}
+			switch entry.Type {
+			case storage.SegmentType:
+				if _, err := pw.Write(entry.Payload); err != nil {
+					pw.CloseWithError(err)
+					break
+				}
+			case storage.FileType:
+				if err := writeEntryFromRelPath(pw, relpath, entry); err != nil {
+					pw.CloseWithError(err)
+					break
+				}
+			}
+		}
+	}()
+	return pr
+}
+
+func writeEntryFromRelPath(w io.Writer, root string, entry *storage.Entry) error {
+	if entry.Size == 0 {
+		return nil
+	}
+
+	// FIXME might should have a check for '../../../../etc/passwd' attempts?
+	fh, err := os.Open(path.Join(root, entry.Name))
+	if err != nil {
+		return err
+	}
+	defer fh.Close()
+	if _, err := io.Copy(w, fh); err != nil {
+		return err
+	}
+
+	return nil
+}