mv x/<tool> => xtool/<tool>

xtool/ar/writer.go

@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ar
+
+import (
+	"io"
+	"strconv"
+)
+
+// Writer provides sequential writing of an ar archive.
+// An ar archive is sequence of header file pairs
+// Call WriteHeader to begin writing a new file, then call Write to supply the file's data
+//
+// Example:
+// archive := ar.NewWriter(writer)
+// archive.WriteGlobalHeader()
+// header := new(ar.Header)
+// header.Size = 15 // bytes
+//
+//	if err := archive.WriteHeader(header); err != nil {
+//		return err
+//	}
+//
+// io.Copy(archive, data)
+type Writer struct {
+	w  io.Writer
+	nb int64 // number of unwritten bytes for the current file entry
+}
+
+// Create a new ar writer that writes to w
+func NewWriter(w io.Writer) *Writer { return &Writer{w: w} }
+
+func (aw *Writer) numeric(b []byte, x int64) {
+	s := strconv.FormatInt(x, 10)
+	for len(s) < len(b) {
+		s = s + " "
+	}
+	copy(b, []byte(s))
+}
+
+func (aw *Writer) octal(b []byte, x int64) {
+	s := "100" + strconv.FormatInt(x, 8)
+	for len(s) < len(b) {
+		s = s + " "
+	}
+	copy(b, []byte(s))
+}
+
+func (aw *Writer) string(b []byte, str string) {
+	s := str
+	for len(s) < len(b) {
+		s = s + " "
+	}
+	copy(b, []byte(s))
+}
+
+// Writes to the current entry in the ar archive
+// Returns ErrWriteTooLong if more than header.Size
+// bytes are written after a call to WriteHeader
+func (aw *Writer) Write(b []byte) (n int, err error) {
+	if int64(len(b)) > aw.nb {
+		b = b[0:aw.nb]
+		err = errWriteTooLong
+	}
+	n, werr := aw.w.Write(b)
+	aw.nb -= int64(n)
+	if werr != nil {
+		return n, werr
+	}
+
+	if len(b)%2 == 1 { // data size must be aligned to an even byte
+		n2, _ := aw.w.Write([]byte{'\n'})
+		return n + n2, err
+	}
+
+	return
+}
+
+func (aw *Writer) WriteGlobalHeader() error {
+	_, err := aw.w.Write([]byte(globalHeader))
+	return err
+}
+
+// Writes the header to the underlying writer and prepares
+// to receive the file payload
+func (aw *Writer) WriteHeader(hdr *Header) error {
+	aw.nb = int64(hdr.Size)
+	header := make([]byte, headerByteSize)
+	s := slicer(header)
+
+	aw.string(s.next(16), hdr.Name)
+	aw.numeric(s.next(12), hdr.ModTime.Unix())
+	aw.numeric(s.next(6), int64(hdr.Uid))
+	aw.numeric(s.next(6), int64(hdr.Gid))
+	aw.octal(s.next(8), hdr.Mode)
+	aw.numeric(s.next(10), hdr.Size)
+	aw.string(s.next(2), "`\n")
+
+	_, err := aw.w.Write(header)
+
+	return err
+}