textio

Go package providing tools for advanced text manipulations

Motivation

This package aims to provide a sutie of tools to deal with text parsing and formatting. It is intended to extend what the standard library already offers, and make it easy to integrate with it.

Examples

This sections presents a couple of examples about how to use this package.

Indenting

Indentation is often a complex problem to solve when dealing with stream of text that may be composed of multiple lines. To address this problem, this package provides the textio.PrefixWriter type, which implements the io.Writer interface and automatically prepends every line of output with a predefined prefix.

Here is an example:

func copyIndent(w io.Writer, r io.Reader) error {
    p := textio.NewPrefixWriter(w, "\t")

    // Copy data from an input stream into the PrefixWriter, all lines will
    // be prefixed with a '\t' character.
    if _, err := io.Copy(p, r); err != nil {
        return err
    }

    // Flushes any data buffered in the PrefixWriter, this is important in
    // case the last line was not terminated by a '\n' character.
    return p.Flush()
}

Tree Formatting

A common way to represent tree-like structures is the formatting used by the tree(1) unix command. The textio.TreeWriter type is an implementation of an io.Writer which supports this kind of output. It works in a recursive fashion where nodes created from a parent tree writer are formatted as part of that tree structure.

Here is an example:

func ls(w io.Writer, path string) {
	tree := NewTreeWriter(w)
	tree.WriteString(filepath.Base(path))
	defer tree.Close()

	files, _ := ioutil.ReadDir(path)

	for _, f := range files {
		if f.Mode().IsDir() {
			ls(tree, filepath.Join(path, f.Name()))
		}
	}

	for _, f := range files {
		if !f.Mode().IsDir() {
			io.WriteString(NewTreeWriter(tree), f.Name())
		}
	}
}

...

ls(os.Stdout, "examples")

Which gives this output:

examples
├── A
│   ├── 1
│   └── 2
└── message