1 files changed, 205 insertions, 0 deletions
diff --git a/libgo/go/archive/tar/writer.go b/libgo/go/archive/tar/writer.go
new file mode 100644
index 000000000..8673bad31
--- /dev/null
+++ b/libgo/go/archive/tar/writer.go
@@ -0,0 +1,205 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tar
+
+// TODO(dsymonds):
+// - catch more errors (no first header, write after close, etc.)
+
+import (
+	"io"
+	"os"
+	"strconv"
+)
+
+var (
+	ErrWriteTooLong    = os.NewError("write too long")
+	ErrFieldTooLong    = os.NewError("header field too long")
+	ErrWriteAfterClose = os.NewError("write after close")
+)
+
+// A Writer provides sequential writing of a tar archive in POSIX.1 format.
+// A tar archive consists of a sequence of files.
+// Call WriteHeader to begin a new file, and then call Write to supply that file's data,
+// writing at most hdr.Size bytes in total.
+//
+// Example:
+//	tw := tar.NewWriter(w)
+//	hdr := new(Header)
+//	hdr.Size = length of data in bytes
+//	// populate other hdr fields as desired
+//	if err := tw.WriteHeader(hdr); err != nil {
+//		// handle error
+//	}
+//	io.Copy(tw, data)
+//	tw.Close()
+type Writer struct {
+	w          io.Writer
+	err        os.Error
+	nb         int64 // number of unwritten bytes for current file entry
+	pad        int64 // amount of padding to write after current file entry
+	closed     bool
+	usedBinary bool // whether the binary numeric field extension was used
+}
+
+// NewWriter creates a new Writer writing to w.
+func NewWriter(w io.Writer) *Writer { return &Writer{w: w} }
+
+// Flush finishes writing the current file (optional).
+func (tw *Writer) Flush() os.Error {
+	n := tw.nb + tw.pad
+	for n > 0 && tw.err == nil {
+		nr := n
+		if nr > blockSize {
+			nr = blockSize
+		}
+		var nw int
+		nw, tw.err = tw.w.Write(zeroBlock[0:nr])
+		n -= int64(nw)
+	}
+	tw.nb = 0
+	tw.pad = 0
+	return tw.err
+}
+
+// Write s into b, terminating it with a NUL if there is room.
+func (tw *Writer) cString(b []byte, s string) {
+	if len(s) > len(b) {
+		if tw.err == nil {
+			tw.err = ErrFieldTooLong
+		}
+		return
+	}
+	copy(b, s)
+	if len(s) < len(b) {
+		b[len(s)] = 0
+	}
+}
+
+// Encode x as an octal ASCII string and write it into b with leading zeros.
+func (tw *Writer) octal(b []byte, x int64) {
+	s := strconv.Itob64(x, 8)
+	// leading zeros, but leave room for a NUL.
+	for len(s)+1 < len(b) {
+		s = "0" + s
+	}
+	tw.cString(b, s)
+}
+
+// Write x into b, either as octal or as binary (GNUtar/star extension).
+func (tw *Writer) numeric(b []byte, x int64) {
+	// Try octal first.
+	s := strconv.Itob64(x, 8)
+	if len(s) < len(b) {
+		tw.octal(b, x)
+		return
+	}
+	// Too big: use binary (big-endian).
+	tw.usedBinary = true
+	for i := len(b) - 1; x > 0 && i >= 0; i-- {
+		b[i] = byte(x)
+		x >>= 8
+	}
+	b[0] |= 0x80 // highest bit indicates binary format
+}
+
+// WriteHeader writes hdr and prepares to accept the file's contents.
+// WriteHeader calls Flush if it is not the first header.
+// Calling after a Close will return ErrWriteAfterClose.
+func (tw *Writer) WriteHeader(hdr *Header) os.Error {
+	if tw.closed {
+		return ErrWriteAfterClose
+	}
+	if tw.err == nil {
+		tw.Flush()
+	}
+	if tw.err != nil {
+		return tw.err
+	}
+
+	tw.nb = int64(hdr.Size)
+	tw.pad = -tw.nb & (blockSize - 1) // blockSize is a power of two
+
+	header := make([]byte, blockSize)
+	s := slicer(header)
+
+	// TODO(dsymonds): handle names longer than 100 chars
+	copy(s.next(100), []byte(hdr.Name))
+
+	tw.octal(s.next(8), hdr.Mode)          // 100:108
+	tw.numeric(s.next(8), int64(hdr.Uid))  // 108:116
+	tw.numeric(s.next(8), int64(hdr.Gid))  // 116:124
+	tw.numeric(s.next(12), hdr.Size)       // 124:136
+	tw.numeric(s.next(12), hdr.Mtime)      // 136:148
+	s.next(8)                              // chksum (148:156)
+	s.next(1)[0] = hdr.Typeflag            // 156:157
+	s.next(100)                            // linkname (157:257)
+	copy(s.next(8), []byte("ustar\x0000")) // 257:265
+	tw.cString(s.next(32), hdr.Uname)      // 265:297
+	tw.cString(s.next(32), hdr.Gname)      // 297:329
+	tw.numeric(s.next(8), hdr.Devmajor)    // 329:337
+	tw.numeric(s.next(8), hdr.Devminor)    // 337:345
+
+	// Use the GNU magic instead of POSIX magic if we used any GNU extensions.
+	if tw.usedBinary {
+		copy(header[257:265], []byte("ustar  \x00"))
+	}
+
+	// The chksum field is terminated by a NUL and a space.
+	// This is different from the other octal fields.
+	chksum, _ := checksum(header)
+	tw.octal(header[148:155], chksum)
+	header[155] = ' '
+
+	if tw.err != nil {
+		// problem with header; probably integer too big for a field.
+		return tw.err
+	}
+
+	_, tw.err = tw.w.Write(header)
+
+	return tw.err
+}
+
+// Write writes to the current entry in the tar archive.
+// Write returns the error ErrWriteTooLong if more than
+// hdr.Size bytes are written after WriteHeader.
+func (tw *Writer) Write(b []byte) (n int, err os.Error) {
+	if tw.closed {
+		err = ErrWriteTooLong
+		return
+	}
+	overwrite := false
+	if int64(len(b)) > tw.nb {
+		b = b[0:tw.nb]
+		overwrite = true
+	}
+	n, err = tw.w.Write(b)
+	tw.nb -= int64(n)
+	if err == nil && overwrite {
+		err = ErrWriteTooLong
+		return
+	}
+	tw.err = err
+	return
+}
+
+// Close closes the tar archive, flushing any unwritten
+// data to the underlying writer.
+func (tw *Writer) Close() os.Error {
+	if tw.err != nil || tw.closed {
+		return tw.err
+	}
+	tw.Flush()
+	tw.closed = true
+
+	// trailer: two zero blocks
+	for i := 0; i < 2; i++ {
+		_, tw.err = tw.w.Write(zeroBlock)
+		if tw.err != nil {
+			break
+		}
+	}
+	return tw.err
+}