Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

3 files changed, 1436 insertions, 0 deletions

diff --git a/src/text/tabwriter/example_test.go b/src/text/tabwriter/example_test.go
new file mode 100644
index 0000000..422ec11
--- /dev/null
+++ b/src/text/tabwriter/example_test.go
@@ -0,0 +1,73 @@
+// Copyright 2012 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 tabwriter_test
+
+import (
+	"fmt"
+	"os"
+	"text/tabwriter"
+)
+
+func ExampleWriter_Init() {
+	w := new(tabwriter.Writer)
+
+	// Format in tab-separated columns with a tab stop of 8.
+	w.Init(os.Stdout, 0, 8, 0, '\t', 0)
+	fmt.Fprintln(w, "a\tb\tc\td\t.")
+	fmt.Fprintln(w, "123\t12345\t1234567\t123456789\t.")
+	fmt.Fprintln(w)
+	w.Flush()
+
+	// Format right-aligned in space-separated columns of minimal width 5
+	// and at least one blank of padding (so wider column entries do not
+	// touch each other).
+	w.Init(os.Stdout, 5, 0, 1, ' ', tabwriter.AlignRight)
+	fmt.Fprintln(w, "a\tb\tc\td\t.")
+	fmt.Fprintln(w, "123\t12345\t1234567\t123456789\t.")
+	fmt.Fprintln(w)
+	w.Flush()
+
+	// output:
+	// a	b	c	d		.
+	// 123	12345	1234567	123456789	.
+	//
+	//     a     b       c         d.
+	//   123 12345 1234567 123456789.
+}
+
+func Example_elastic() {
+	// Observe how the b's and the d's, despite appearing in the
+	// second cell of each line, belong to different columns.
+	w := tabwriter.NewWriter(os.Stdout, 0, 0, 1, '.', tabwriter.AlignRight|tabwriter.Debug)
+	fmt.Fprintln(w, "a\tb\tc")
+	fmt.Fprintln(w, "aa\tbb\tcc")
+	fmt.Fprintln(w, "aaa\t") // trailing tab
+	fmt.Fprintln(w, "aaaa\tdddd\teeee")
+	w.Flush()
+
+	// output:
+	// ....a|..b|c
+	// ...aa|.bb|cc
+	// ..aaa|
+	// .aaaa|.dddd|eeee
+}
+
+func Example_trailingTab() {
+	// Observe that the third line has no trailing tab,
+	// so its final cell is not part of an aligned column.
+	const padding = 3
+	w := tabwriter.NewWriter(os.Stdout, 0, 0, padding, '-', tabwriter.AlignRight|tabwriter.Debug)
+	fmt.Fprintln(w, "a\tb\taligned\t")
+	fmt.Fprintln(w, "aa\tbb\taligned\t")
+	fmt.Fprintln(w, "aaa\tbbb\tunaligned") // no trailing tab
+	fmt.Fprintln(w, "aaaa\tbbbb\taligned\t")
+	w.Flush()
+
+	// output:
+	// ------a|------b|---aligned|
+	// -----aa|-----bb|---aligned|
+	// ----aaa|----bbb|unaligned
+	// ---aaaa|---bbbb|---aligned|
+}
diff --git a/src/text/tabwriter/tabwriter.go b/src/text/tabwriter/tabwriter.go
new file mode 100644
index 0000000..76dec7b
--- /dev/null
+++ b/src/text/tabwriter/tabwriter.go
@@ -0,0 +1,609 @@
+// 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 tabwriter implements a write filter (tabwriter.Writer) that
+// translates tabbed columns in input into properly aligned text.
+//
+// The package is using the Elastic Tabstops algorithm described at
+// http://nickgravgaard.com/elastictabstops/index.html.
+//
+// The text/tabwriter package is frozen and is not accepting new features.
+package tabwriter
+
+import (
+	"io"
+	"unicode/utf8"
+)
+
+// ----------------------------------------------------------------------------
+// Filter implementation
+
+// A cell represents a segment of text terminated by tabs or line breaks.
+// The text itself is stored in a separate buffer; cell only describes the
+// segment's size in bytes, its width in runes, and whether it's an htab
+// ('\t') terminated cell.
+//
+type cell struct {
+	size  int  // cell size in bytes
+	width int  // cell width in runes
+	htab  bool // true if the cell is terminated by an htab ('\t')
+}
+
+// A Writer is a filter that inserts padding around tab-delimited
+// columns in its input to align them in the output.
+//
+// The Writer treats incoming bytes as UTF-8-encoded text consisting
+// of cells terminated by horizontal ('\t') or vertical ('\v') tabs,
+// and newline ('\n') or formfeed ('\f') characters; both newline and
+// formfeed act as line breaks.
+//
+// Tab-terminated cells in contiguous lines constitute a column. The
+// Writer inserts padding as needed to make all cells in a column have
+// the same width, effectively aligning the columns. It assumes that
+// all characters have the same width, except for tabs for which a
+// tabwidth must be specified. Column cells must be tab-terminated, not
+// tab-separated: non-tab terminated trailing text at the end of a line
+// forms a cell but that cell is not part of an aligned column.
+// For instance, in this example (where | stands for a horizontal tab):
+//
+//	aaaa|bbb|d
+//	aa  |b  |dd
+//	a   |
+//	aa  |cccc|eee
+//
+// the b and c are in distinct columns (the b column is not contiguous
+// all the way). The d and e are not in a column at all (there's no
+// terminating tab, nor would the column be contiguous).
+//
+// The Writer assumes that all Unicode code points have the same width;
+// this may not be true in some fonts or if the string contains combining
+// characters.
+//
+// If DiscardEmptyColumns is set, empty columns that are terminated
+// entirely by vertical (or "soft") tabs are discarded. Columns
+// terminated by horizontal (or "hard") tabs are not affected by
+// this flag.
+//
+// If a Writer is configured to filter HTML, HTML tags and entities
+// are passed through. The widths of tags and entities are
+// assumed to be zero (tags) and one (entities) for formatting purposes.
+//
+// A segment of text may be escaped by bracketing it with Escape
+// characters. The tabwriter passes escaped text segments through
+// unchanged. In particular, it does not interpret any tabs or line
+// breaks within the segment. If the StripEscape flag is set, the
+// Escape characters are stripped from the output; otherwise they
+// are passed through as well. For the purpose of formatting, the
+// width of the escaped text is always computed excluding the Escape
+// characters.
+//
+// The formfeed character acts like a newline but it also terminates
+// all columns in the current line (effectively calling Flush). Tab-
+// terminated cells in the next line start new columns. Unless found
+// inside an HTML tag or inside an escaped text segment, formfeed
+// characters appear as newlines in the output.
+//
+// The Writer must buffer input internally, because proper spacing
+// of one line may depend on the cells in future lines. Clients must
+// call Flush when done calling Write.
+//
+type Writer struct {
+	// configuration
+	output   io.Writer
+	minwidth int
+	tabwidth int
+	padding  int
+	padbytes [8]byte
+	flags    uint
+
+	// current state
+	buf     []byte   // collected text excluding tabs or line breaks
+	pos     int      // buffer position up to which cell.width of incomplete cell has been computed
+	cell    cell     // current incomplete cell; cell.width is up to buf[pos] excluding ignored sections
+	endChar byte     // terminating char of escaped sequence (Escape for escapes, '>', ';' for HTML tags/entities, or 0)
+	lines   [][]cell // list of lines; each line is a list of cells
+	widths  []int    // list of column widths in runes - re-used during formatting
+}
+
+// addLine adds a new line.
+// flushed is a hint indicating whether the underlying writer was just flushed.
+// If so, the previous line is not likely to be a good indicator of the new line's cells.
+func (b *Writer) addLine(flushed bool) {
+	// Grow slice instead of appending,
+	// as that gives us an opportunity
+	// to re-use an existing []cell.
+	if n := len(b.lines) + 1; n <= cap(b.lines) {
+		b.lines = b.lines[:n]
+		b.lines[n-1] = b.lines[n-1][:0]
+	} else {
+		b.lines = append(b.lines, nil)
+	}
+
+	if !flushed {
+		// The previous line is probably a good indicator
+		// of how many cells the current line will have.
+		// If the current line's capacity is smaller than that,
+		// abandon it and make a new one.
+		if n := len(b.lines); n >= 2 {
+			if prev := len(b.lines[n-2]); prev > cap(b.lines[n-1]) {
+				b.lines[n-1] = make([]cell, 0, prev)
+			}
+		}
+	}
+}
+
+// Reset the current state.
+func (b *Writer) reset() {
+	b.buf = b.buf[:0]
+	b.pos = 0
+	b.cell = cell{}
+	b.endChar = 0
+	b.lines = b.lines[0:0]
+	b.widths = b.widths[0:0]
+	b.addLine(true)
+}
+
+// Internal representation (current state):
+//
+// - all text written is appended to buf; tabs and line breaks are stripped away
+// - at any given time there is a (possibly empty) incomplete cell at the end
+//   (the cell starts after a tab or line break)
+// - cell.size is the number of bytes belonging to the cell so far
+// - cell.width is text width in runes of that cell from the start of the cell to
+//   position pos; html tags and entities are excluded from this width if html
+//   filtering is enabled
+// - the sizes and widths of processed text are kept in the lines list
+//   which contains a list of cells for each line
+// - the widths list is a temporary list with current widths used during
+//   formatting; it is kept in Writer because it's re-used
+//
+//                    |<---------- size ---------->|
+//                    |                            |
+//                    |<- width ->|<- ignored ->|  |
+//                    |           |             |  |
+// [---processed---tab------------<tag>...</tag>...]
+// ^                  ^                         ^
+// |                  |                         |
+// buf                start of incomplete cell  pos
+
+// Formatting can be controlled with these flags.
+const (
+	// Ignore html tags and treat entities (starting with '&'
+	// and ending in ';') as single characters (width = 1).
+	FilterHTML uint = 1 << iota
+
+	// Strip Escape characters bracketing escaped text segments
+	// instead of passing them through unchanged with the text.
+	StripEscape
+
+	// Force right-alignment of cell content.
+	// Default is left-alignment.
+	AlignRight
+
+	// Handle empty columns as if they were not present in
+	// the input in the first place.
+	DiscardEmptyColumns
+
+	// Always use tabs for indentation columns (i.e., padding of
+	// leading empty cells on the left) independent of padchar.
+	TabIndent
+
+	// Print a vertical bar ('|') between columns (after formatting).
+	// Discarded columns appear as zero-width columns ("||").
+	Debug
+)
+
+// A Writer must be initialized with a call to Init. The first parameter (output)
+// specifies the filter output. The remaining parameters control the formatting:
+//
+//	minwidth	minimal cell width including any padding
+//	tabwidth	width of tab characters (equivalent number of spaces)
+//	padding		padding added to a cell before computing its width
+//	padchar		ASCII char used for padding
+//			if padchar == '\t', the Writer will assume that the
+//			width of a '\t' in the formatted output is tabwidth,
+//			and cells are left-aligned independent of align_left
+//			(for correct-looking results, tabwidth must correspond
+//			to the tab width in the viewer displaying the result)
+//	flags		formatting control
+//
+func (b *Writer) Init(output io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *Writer {
+	if minwidth < 0 || tabwidth < 0 || padding < 0 {
+		panic("negative minwidth, tabwidth, or padding")
+	}
+	b.output = output
+	b.minwidth = minwidth
+	b.tabwidth = tabwidth
+	b.padding = padding
+	for i := range b.padbytes {
+		b.padbytes[i] = padchar
+	}
+	if padchar == '\t' {
+		// tab padding enforces left-alignment
+		flags &^= AlignRight
+	}
+	b.flags = flags
+
+	b.reset()
+
+	return b
+}
+
+// debugging support (keep code around)
+func (b *Writer) dump() {
+	pos := 0
+	for i, line := range b.lines {
+		print("(", i, ") ")
+		for _, c := range line {
+			print("[", string(b.buf[pos:pos+c.size]), "]")
+			pos += c.size
+		}
+		print("\n")
+	}
+	print("\n")
+}
+
+// local error wrapper so we can distinguish errors we want to return
+// as errors from genuine panics (which we don't want to return as errors)
+type osError struct {
+	err error
+}
+
+func (b *Writer) write0(buf []byte) {
+	n, err := b.output.Write(buf)
+	if n != len(buf) && err == nil {
+		err = io.ErrShortWrite
+	}
+	if err != nil {
+		panic(osError{err})
+	}
+}
+
+func (b *Writer) writeN(src []byte, n int) {
+	for n > len(src) {
+		b.write0(src)
+		n -= len(src)
+	}
+	b.write0(src[0:n])
+}
+
+var (
+	newline = []byte{'\n'}
+	tabs    = []byte("\t\t\t\t\t\t\t\t")
+)
+
+func (b *Writer) writePadding(textw, cellw int, useTabs bool) {
+	if b.padbytes[0] == '\t' || useTabs {
+		// padding is done with tabs
+		if b.tabwidth == 0 {
+			return // tabs have no width - can't do any padding
+		}
+		// make cellw the smallest multiple of b.tabwidth
+		cellw = (cellw + b.tabwidth - 1) / b.tabwidth * b.tabwidth
+		n := cellw - textw // amount of padding
+		if n < 0 {
+			panic("internal error")
+		}
+		b.writeN(tabs, (n+b.tabwidth-1)/b.tabwidth)
+		return
+	}
+
+	// padding is done with non-tab characters
+	b.writeN(b.padbytes[0:], cellw-textw)
+}
+
+var vbar = []byte{'|'}
+
+func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int) {
+	pos = pos0
+	for i := line0; i < line1; i++ {
+		line := b.lines[i]
+
+		// if TabIndent is set, use tabs to pad leading empty cells
+		useTabs := b.flags&TabIndent != 0
+
+		for j, c := range line {
+			if j > 0 && b.flags&Debug != 0 {
+				// indicate column break
+				b.write0(vbar)
+			}
+
+			if c.size == 0 {
+				// empty cell
+				if j < len(b.widths) {
+					b.writePadding(c.width, b.widths[j], useTabs)
+				}
+			} else {
+				// non-empty cell
+				useTabs = false
+				if b.flags&AlignRight == 0 { // align left
+					b.write0(b.buf[pos : pos+c.size])
+					pos += c.size
+					if j < len(b.widths) {
+						b.writePadding(c.width, b.widths[j], false)
+					}
+				} else { // align right
+					if j < len(b.widths) {
+						b.writePadding(c.width, b.widths[j], false)
+					}
+					b.write0(b.buf[pos : pos+c.size])
+					pos += c.size
+				}
+			}
+		}
+
+		if i+1 == len(b.lines) {
+			// last buffered line - we don't have a newline, so just write
+			// any outstanding buffered data
+			b.write0(b.buf[pos : pos+b.cell.size])
+			pos += b.cell.size
+		} else {
+			// not the last line - write newline
+			b.write0(newline)
+		}
+	}
+	return
+}
+
+// Format the text between line0 and line1 (excluding line1); pos
+// is the buffer position corresponding to the beginning of line0.
+// Returns the buffer position corresponding to the beginning of
+// line1 and an error, if any.
+//
+func (b *Writer) format(pos0 int, line0, line1 int) (pos int) {
+	pos = pos0
+	column := len(b.widths)
+	for this := line0; this < line1; this++ {
+		line := b.lines[this]
+
+		if column >= len(line)-1 {
+			continue
+		}
+		// cell exists in this column => this line
+		// has more cells than the previous line
+		// (the last cell per line is ignored because cells are
+		// tab-terminated; the last cell per line describes the
+		// text before the newline/formfeed and does not belong
+		// to a column)
+
+		// print unprinted lines until beginning of block
+		pos = b.writeLines(pos, line0, this)
+		line0 = this
+
+		// column block begin
+		width := b.minwidth // minimal column width
+		discardable := true // true if all cells in this column are empty and "soft"
+		for ; this < line1; this++ {
+			line = b.lines[this]
+			if column >= len(line)-1 {
+				break
+			}
+			// cell exists in this column
+			c := line[column]
+			// update width
+			if w := c.width + b.padding; w > width {
+				width = w
+			}
+			// update discardable
+			if c.width > 0 || c.htab {
+				discardable = false
+			}
+		}
+		// column block end
+
+		// discard empty columns if necessary
+		if discardable && b.flags&DiscardEmptyColumns != 0 {
+			width = 0
+		}
+
+		// format and print all columns to the right of this column
+		// (we know the widths of this column and all columns to the left)
+		b.widths = append(b.widths, width) // push width
+		pos = b.format(pos, line0, this)
+		b.widths = b.widths[0 : len(b.widths)-1] // pop width
+		line0 = this
+	}
+
+	// print unprinted lines until end
+	return b.writeLines(pos, line0, line1)
+}
+
+// Append text to current cell.
+func (b *Writer) append(text []byte) {
+	b.buf = append(b.buf, text...)
+	b.cell.size += len(text)
+}
+
+// Update the cell width.
+func (b *Writer) updateWidth() {
+	b.cell.width += utf8.RuneCount(b.buf[b.pos:])
+	b.pos = len(b.buf)
+}
+
+// To escape a text segment, bracket it with Escape characters.
+// For instance, the tab in this string "Ignore this tab: \xff\t\xff"
+// does not terminate a cell and constitutes a single character of
+// width one for formatting purposes.
+//
+// The value 0xff was chosen because it cannot appear in a valid UTF-8 sequence.
+//
+const Escape = '\xff'
+
+// Start escaped mode.
+func (b *Writer) startEscape(ch byte) {
+	switch ch {
+	case Escape:
+		b.endChar = Escape
+	case '<':
+		b.endChar = '>'
+	case '&':
+		b.endChar = ';'
+	}
+}
+
+// Terminate escaped mode. If the escaped text was an HTML tag, its width
+// is assumed to be zero for formatting purposes; if it was an HTML entity,
+// its width is assumed to be one. In all other cases, the width is the
+// unicode width of the text.
+//
+func (b *Writer) endEscape() {
+	switch b.endChar {
+	case Escape:
+		b.updateWidth()
+		if b.flags&StripEscape == 0 {
+			b.cell.width -= 2 // don't count the Escape chars
+		}
+	case '>': // tag of zero width
+	case ';':
+		b.cell.width++ // entity, count as one rune
+	}
+	b.pos = len(b.buf)
+	b.endChar = 0
+}
+
+// Terminate the current cell by adding it to the list of cells of the
+// current line. Returns the number of cells in that line.
+//
+func (b *Writer) terminateCell(htab bool) int {
+	b.cell.htab = htab
+	line := &b.lines[len(b.lines)-1]
+	*line = append(*line, b.cell)
+	b.cell = cell{}
+	return len(*line)
+}
+
+func (b *Writer) handlePanic(err *error, op string) {
+	if e := recover(); e != nil {
+		if op == "Flush" {
+			// If Flush ran into a panic, we still need to reset.
+			b.reset()
+		}
+		if nerr, ok := e.(osError); ok {
+			*err = nerr.err
+			return
+		}
+		panic("tabwriter: panic during " + op)
+	}
+}
+
+// Flush should be called after the last call to Write to ensure
+// that any data buffered in the Writer is written to output. Any
+// incomplete escape sequence at the end is considered
+// complete for formatting purposes.
+func (b *Writer) Flush() error {
+	return b.flush()
+}
+
+// flush is the internal version of Flush, with a named return value which we
+// don't want to expose.
+func (b *Writer) flush() (err error) {
+	defer b.handlePanic(&err, "Flush")
+	b.flushNoDefers()
+	return nil
+}
+
+// flushNoDefers is like flush, but without a deferred handlePanic call. This
+// can be called from other methods which already have their own deferred
+// handlePanic calls, such as Write, and avoid the extra defer work.
+func (b *Writer) flushNoDefers() {
+	// add current cell if not empty
+	if b.cell.size > 0 {
+		if b.endChar != 0 {
+			// inside escape - terminate it even if incomplete
+			b.endEscape()
+		}
+		b.terminateCell(false)
+	}
+
+	// format contents of buffer
+	b.format(0, 0, len(b.lines))
+	b.reset()
+}
+
+var hbar = []byte("---\n")
+
+// Write writes buf to the writer b.
+// The only errors returned are ones encountered
+// while writing to the underlying output stream.
+//
+func (b *Writer) Write(buf []byte) (n int, err error) {
+	defer b.handlePanic(&err, "Write")
+
+	// split text into cells
+	n = 0
+	for i, ch := range buf {
+		if b.endChar == 0 {
+			// outside escape
+			switch ch {
+			case '\t', '\v', '\n', '\f':
+				// end of cell
+				b.append(buf[n:i])
+				b.updateWidth()
+				n = i + 1 // ch consumed
+				ncells := b.terminateCell(ch == '\t')
+				if ch == '\n' || ch == '\f' {
+					// terminate line
+					b.addLine(ch == '\f')
+					if ch == '\f' || ncells == 1 {
+						// A '\f' always forces a flush. Otherwise, if the previous
+						// line has only one cell which does not have an impact on
+						// the formatting of the following lines (the last cell per
+						// line is ignored by format()), thus we can flush the
+						// Writer contents.
+						b.flushNoDefers()
+						if ch == '\f' && b.flags&Debug != 0 {
+							// indicate section break
+							b.write0(hbar)
+						}
+					}
+				}
+
+			case Escape:
+				// start of escaped sequence
+				b.append(buf[n:i])
+				b.updateWidth()
+				n = i
+				if b.flags&StripEscape != 0 {
+					n++ // strip Escape
+				}
+				b.startEscape(Escape)
+
+			case '<', '&':
+				// possibly an html tag/entity
+				if b.flags&FilterHTML != 0 {
+					// begin of tag/entity
+					b.append(buf[n:i])
+					b.updateWidth()
+					n = i
+					b.startEscape(ch)
+				}
+			}
+
+		} else {
+			// inside escape
+			if ch == b.endChar {
+				// end of tag/entity
+				j := i + 1
+				if ch == Escape && b.flags&StripEscape != 0 {
+					j = i // strip Escape
+				}
+				b.append(buf[n:j])
+				n = i + 1 // ch consumed
+				b.endEscape()
+			}
+		}
+	}
+
+	// append leftover text
+	b.append(buf[n:])
+	n = len(buf)
+	return
+}
+
+// NewWriter allocates and initializes a new tabwriter.Writer.
+// The parameters are the same as for the Init function.
+//
+func NewWriter(output io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *Writer {
+	return new(Writer).Init(output, minwidth, tabwidth, padding, padchar, flags)
+}
diff --git a/src/text/tabwriter/tabwriter_test.go b/src/text/tabwriter/tabwriter_test.go
new file mode 100644
index 0000000..a51358d
--- /dev/null
+++ b/src/text/tabwriter/tabwriter_test.go
@@ -0,0 +1,754 @@
+// 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 tabwriter_test
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"testing"
+	. "text/tabwriter"
+)
+
+type buffer struct {
+	a []byte
+}
+
+func (b *buffer) init(n int) { b.a = make([]byte, 0, n) }
+
+func (b *buffer) clear() { b.a = b.a[0:0] }
+
+func (b *buffer) Write(buf []byte) (written int, err error) {
+	n := len(b.a)
+	m := len(buf)
+	if n+m <= cap(b.a) {
+		b.a = b.a[0 : n+m]
+		for i := 0; i < m; i++ {
+			b.a[n+i] = buf[i]
+		}
+	} else {
+		panic("buffer.Write: buffer too small")
+	}
+	return len(buf), nil
+}
+
+func (b *buffer) String() string { return string(b.a) }
+
+func write(t *testing.T, testname string, w *Writer, src string) {
+	written, err := io.WriteString(w, src)
+	if err != nil {
+		t.Errorf("--- test: %s\n--- src:\n%q\n--- write error: %v\n", testname, src, err)
+	}
+	if written != len(src) {
+		t.Errorf("--- test: %s\n--- src:\n%q\n--- written = %d, len(src) = %d\n", testname, src, written, len(src))
+	}
+}
+
+func verify(t *testing.T, testname string, w *Writer, b *buffer, src, expected string) {
+	err := w.Flush()
+	if err != nil {
+		t.Errorf("--- test: %s\n--- src:\n%q\n--- flush error: %v\n", testname, src, err)
+	}
+
+	res := b.String()
+	if res != expected {
+		t.Errorf("--- test: %s\n--- src:\n%q\n--- found:\n%q\n--- expected:\n%q\n", testname, src, res, expected)
+	}
+}
+
+func check(t *testing.T, testname string, minwidth, tabwidth, padding int, padchar byte, flags uint, src, expected string) {
+	var b buffer
+	b.init(1000)
+
+	var w Writer
+	w.Init(&b, minwidth, tabwidth, padding, padchar, flags)
+
+	// write all at once
+	title := testname + " (written all at once)"
+	b.clear()
+	write(t, title, &w, src)
+	verify(t, title, &w, &b, src, expected)
+
+	// write byte-by-byte
+	title = testname + " (written byte-by-byte)"
+	b.clear()
+	for i := 0; i < len(src); i++ {
+		write(t, title, &w, src[i:i+1])
+	}
+	verify(t, title, &w, &b, src, expected)
+
+	// write using Fibonacci slice sizes
+	title = testname + " (written in fibonacci slices)"
+	b.clear()
+	for i, d := 0, 0; i < len(src); {
+		write(t, title, &w, src[i:i+d])
+		i, d = i+d, d+1
+		if i+d > len(src) {
+			d = len(src) - i
+		}
+	}
+	verify(t, title, &w, &b, src, expected)
+}
+
+var tests = []struct {
+	testname                    string
+	minwidth, tabwidth, padding int
+	padchar                     byte
+	flags                       uint
+	src, expected               string
+}{
+	{
+		"1a",
+		8, 0, 1, '.', 0,
+		"",
+		"",
+	},
+
+	{
+		"1a debug",
+		8, 0, 1, '.', Debug,
+		"",
+		"",
+	},
+
+	{
+		"1b esc stripped",
+		8, 0, 1, '.', StripEscape,
+		"\xff\xff",
+		"",
+	},
+
+	{
+		"1b esc",
+		8, 0, 1, '.', 0,
+		"\xff\xff",
+		"\xff\xff",
+	},
+
+	{
+		"1c esc stripped",
+		8, 0, 1, '.', StripEscape,
+		"\xff\t\xff",
+		"\t",
+	},
+
+	{
+		"1c esc",
+		8, 0, 1, '.', 0,
+		"\xff\t\xff",
+		"\xff\t\xff",
+	},
+
+	{
+		"1d esc stripped",
+		8, 0, 1, '.', StripEscape,
+		"\xff\"foo\t\n\tbar\"\xff",
+		"\"foo\t\n\tbar\"",
+	},
+
+	{
+		"1d esc",
+		8, 0, 1, '.', 0,
+		"\xff\"foo\t\n\tbar\"\xff",
+		"\xff\"foo\t\n\tbar\"\xff",
+	},
+
+	{
+		"1e esc stripped",
+		8, 0, 1, '.', StripEscape,
+		"abc\xff\tdef", // unterminated escape
+		"abc\tdef",
+	},
+
+	{
+		"1e esc",
+		8, 0, 1, '.', 0,
+		"abc\xff\tdef", // unterminated escape
+		"abc\xff\tdef",
+	},
+
+	{
+		"2",
+		8, 0, 1, '.', 0,
+		"\n\n\n",
+		"\n\n\n",
+	},
+
+	{
+		"3",
+		8, 0, 1, '.', 0,
+		"a\nb\nc",
+		"a\nb\nc",
+	},
+
+	{
+		"4a",
+		8, 0, 1, '.', 0,
+		"\t", // '\t' terminates an empty cell on last line - nothing to print
+		"",
+	},
+
+	{
+		"4b",
+		8, 0, 1, '.', AlignRight,
+		"\t", // '\t' terminates an empty cell on last line - nothing to print
+		"",
+	},
+
+	{
+		"5",
+		8, 0, 1, '.', 0,
+		"*\t*",
+		"*.......*",
+	},
+
+	{
+		"5b",
+		8, 0, 1, '.', 0,
+		"*\t*\n",
+		"*.......*\n",
+	},
+
+	{
+		"5c",
+		8, 0, 1, '.', 0,
+		"*\t*\t",
+		"*.......*",
+	},
+
+	{
+		"5c debug",
+		8, 0, 1, '.', Debug,
+		"*\t*\t",
+		"*.......|*",
+	},
+
+	{
+		"5d",
+		8, 0, 1, '.', AlignRight,
+		"*\t*\t",
+		".......**",
+	},
+
+	{
+		"6",
+		8, 0, 1, '.', 0,
+		"\t\n",
+		"........\n",
+	},
+
+	{
+		"7a",
+		8, 0, 1, '.', 0,
+		"a) foo",
+		"a) foo",
+	},
+
+	{
+		"7b",
+		8, 0, 1, ' ', 0,
+		"b) foo\tbar",
+		"b) foo  bar",
+	},
+
+	{
+		"7c",
+		8, 0, 1, '.', 0,
+		"c) foo\tbar\t",
+		"c) foo..bar",
+	},
+
+	{
+		"7d",
+		8, 0, 1, '.', 0,
+		"d) foo\tbar\n",
+		"d) foo..bar\n",
+	},
+
+	{
+		"7e",
+		8, 0, 1, '.', 0,
+		"e) foo\tbar\t\n",
+		"e) foo..bar.....\n",
+	},
+
+	{
+		"7f",
+		8, 0, 1, '.', FilterHTML,
+		"f) f&lt;o\t<b>bar</b>\t\n",
+		"f) f&lt;o..<b>bar</b>.....\n",
+	},
+
+	{
+		"7g",
+		8, 0, 1, '.', FilterHTML,
+		"g) f&lt;o\t<b>bar</b>\t non-terminated entity &amp",
+		"g) f&lt;o..<b>bar</b>..... non-terminated entity &amp",
+	},
+
+	{
+		"7g debug",
+		8, 0, 1, '.', FilterHTML | Debug,
+		"g) f&lt;o\t<b>bar</b>\t non-terminated entity &amp",
+		"g) f&lt;o..|<b>bar</b>.....| non-terminated entity &amp",
+	},
+
+	{
+		"8",
+		8, 0, 1, '*', 0,
+		"Hello, world!\n",
+		"Hello, world!\n",
+	},
+
+	{
+		"9a",
+		1, 0, 0, '.', 0,
+		"1\t2\t3\t4\n" +
+			"11\t222\t3333\t44444\n",
+
+		"1.2..3...4\n" +
+			"11222333344444\n",
+	},
+
+	{
+		"9b",
+		1, 0, 0, '.', FilterHTML,
+		"1\t2<!---\f--->\t3\t4\n" + // \f inside HTML is ignored
+			"11\t222\t3333\t44444\n",
+
+		"1.2<!---\f--->..3...4\n" +
+			"11222333344444\n",
+	},
+
+	{
+		"9c",
+		1, 0, 0, '.', 0,
+		"1\t2\t3\t4\f" + // \f causes a newline and flush
+			"11\t222\t3333\t44444\n",
+
+		"1234\n" +
+			"11222333344444\n",
+	},
+
+	{
+		"9c debug",
+		1, 0, 0, '.', Debug,
+		"1\t2\t3\t4\f" + // \f causes a newline and flush
+			"11\t222\t3333\t44444\n",
+
+		"1|2|3|4\n" +
+			"---\n" +
+			"11|222|3333|44444\n",
+	},
+
+	{
+		"10a",
+		5, 0, 0, '.', 0,
+		"1\t2\t3\t4\n",
+		"1....2....3....4\n",
+	},
+
+	{
+		"10b",
+		5, 0, 0, '.', 0,
+		"1\t2\t3\t4\t\n",
+		"1....2....3....4....\n",
+	},
+
+	{
+		"11",
+		8, 0, 1, '.', 0,
+		"本\tb\tc\n" +
+			"aa\t\u672c\u672c\u672c\tcccc\tddddd\n" +
+			"aaa\tbbbb\n",
+
+		"本.......b.......c\n" +
+			"aa......本本本.....cccc....ddddd\n" +
+			"aaa.....bbbb\n",
+	},
+
+	{
+		"12a",
+		8, 0, 1, ' ', AlignRight,
+		"a\tè\tc\t\n" +
+			"aa\tèèè\tcccc\tddddd\t\n" +
+			"aaa\tèèèè\t\n",
+
+		"       a       è       c\n" +
+			"      aa     èèè    cccc   ddddd\n" +
+			"     aaa    èèèè\n",
+	},
+
+	{
+		"12b",
+		2, 0, 0, ' ', 0,
+		"a\tb\tc\n" +
+			"aa\tbbb\tcccc\n" +
+			"aaa\tbbbb\n",
+
+		"a  b  c\n" +
+			"aa bbbcccc\n" +
+			"aaabbbb\n",
+	},
+
+	{
+		"12c",
+		8, 0, 1, '_', 0,
+		"a\tb\tc\n" +
+			"aa\tbbb\tcccc\n" +
+			"aaa\tbbbb\n",
+
+		"a_______b_______c\n" +
+			"aa______bbb_____cccc\n" +
+			"aaa_____bbbb\n",
+	},
+
+	{
+		"13a",
+		4, 0, 1, '-', 0,
+		"4444\t日本語\t22\t1\t333\n" +
+			"999999999\t22\n" +
+			"7\t22\n" +
+			"\t\t\t88888888\n" +
+			"\n" +
+			"666666\t666666\t666666\t4444\n" +
+			"1\t1\t999999999\t0000000000\n",
+
+		"4444------日本語-22--1---333\n" +
+			"999999999-22\n" +
+			"7---------22\n" +
+			"------------------88888888\n" +
+			"\n" +
+			"666666-666666-666666----4444\n" +
+			"1------1------999999999-0000000000\n",
+	},
+
+	{
+		"13b",
+		4, 0, 3, '.', 0,
+		"4444\t333\t22\t1\t333\n" +
+			"999999999\t22\n" +
+			"7\t22\n" +
+			"\t\t\t88888888\n" +
+			"\n" +
+			"666666\t666666\t666666\t4444\n" +
+			"1\t1\t999999999\t0000000000\n",
+
+		"4444........333...22...1...333\n" +
+			"999999999...22\n" +
+			"7...........22\n" +
+			"....................88888888\n" +
+			"\n" +
+			"666666...666666...666666......4444\n" +
+			"1........1........999999999...0000000000\n",
+	},
+
+	{
+		"13c",
+		8, 8, 1, '\t', FilterHTML,
+		"4444\t333\t22\t1\t333\n" +
+			"999999999\t22\n" +
+			"7\t22\n" +
+			"\t\t\t88888888\n" +
+			"\n" +
+			"666666\t666666\t666666\t4444\n" +
+			"1\t1\t<font color=red attr=日本語>999999999</font>\t0000000000\n",
+
+		"4444\t\t333\t22\t1\t333\n" +
+			"999999999\t22\n" +
+			"7\t\t22\n" +
+			"\t\t\t\t88888888\n" +
+			"\n" +
+			"666666\t666666\t666666\t\t4444\n" +
+			"1\t1\t<font color=red attr=日本語>999999999</font>\t0000000000\n",
+	},
+
+	{
+		"14",
+		1, 0, 2, ' ', AlignRight,
+		".0\t.3\t2.4\t-5.1\t\n" +
+			"23.0\t12345678.9\t2.4\t-989.4\t\n" +
+			"5.1\t12.0\t2.4\t-7.0\t\n" +
+			".0\t0.0\t332.0\t8908.0\t\n" +
+			".0\t-.3\t456.4\t22.1\t\n" +
+			".0\t1.2\t44.4\t-13.3\t\t",
+
+		"    .0          .3    2.4    -5.1\n" +
+			"  23.0  12345678.9    2.4  -989.4\n" +
+			"   5.1        12.0    2.4    -7.0\n" +
+			"    .0         0.0  332.0  8908.0\n" +
+			"    .0         -.3  456.4    22.1\n" +
+			"    .0         1.2   44.4   -13.3",
+	},
+
+	{
+		"14 debug",
+		1, 0, 2, ' ', AlignRight | Debug,
+		".0\t.3\t2.4\t-5.1\t\n" +
+			"23.0\t12345678.9\t2.4\t-989.4\t\n" +
+			"5.1\t12.0\t2.4\t-7.0\t\n" +
+			".0\t0.0\t332.0\t8908.0\t\n" +
+			".0\t-.3\t456.4\t22.1\t\n" +
+			".0\t1.2\t44.4\t-13.3\t\t",
+
+		"    .0|          .3|    2.4|    -5.1|\n" +
+			"  23.0|  12345678.9|    2.4|  -989.4|\n" +
+			"   5.1|        12.0|    2.4|    -7.0|\n" +
+			"    .0|         0.0|  332.0|  8908.0|\n" +
+			"    .0|         -.3|  456.4|    22.1|\n" +
+			"    .0|         1.2|   44.4|   -13.3|",
+	},
+
+	{
+		"15a",
+		4, 0, 0, '.', 0,
+		"a\t\tb",
+		"a.......b",
+	},
+
+	{
+		"15b",
+		4, 0, 0, '.', DiscardEmptyColumns,
+		"a\t\tb", // htabs - do not discard column
+		"a.......b",
+	},
+
+	{
+		"15c",
+		4, 0, 0, '.', DiscardEmptyColumns,
+		"a\v\vb",
+		"a...b",
+	},
+
+	{
+		"15d",
+		4, 0, 0, '.', AlignRight | DiscardEmptyColumns,
+		"a\v\vb",
+		"...ab",
+	},
+
+	{
+		"16a",
+		100, 100, 0, '\t', 0,
+		"a\tb\t\td\n" +
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+
+		"a\tb\t\td\n" +
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+	},
+
+	{
+		"16b",
+		100, 100, 0, '\t', DiscardEmptyColumns,
+		"a\vb\v\vd\n" +
+			"a\vb\v\vd\ve\n" +
+			"a\n" +
+			"a\vb\vc\vd\n" +
+			"a\vb\vc\vd\ve\n",
+
+		"a\tb\td\n" +
+			"a\tb\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+	},
+
+	{
+		"16b debug",
+		100, 100, 0, '\t', DiscardEmptyColumns | Debug,
+		"a\vb\v\vd\n" +
+			"a\vb\v\vd\ve\n" +
+			"a\n" +
+			"a\vb\vc\vd\n" +
+			"a\vb\vc\vd\ve\n",
+
+		"a\t|b\t||d\n" +
+			"a\t|b\t||d\t|e\n" +
+			"a\n" +
+			"a\t|b\t|c\t|d\n" +
+			"a\t|b\t|c\t|d\t|e\n",
+	},
+
+	{
+		"16c",
+		100, 100, 0, '\t', DiscardEmptyColumns,
+		"a\tb\t\td\n" + // hard tabs - do not discard column
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+
+		"a\tb\t\td\n" +
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+	},
+
+	{
+		"16c debug",
+		100, 100, 0, '\t', DiscardEmptyColumns | Debug,
+		"a\tb\t\td\n" + // hard tabs - do not discard column
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+
+		"a\t|b\t|\t|d\n" +
+			"a\t|b\t|\t|d\t|e\n" +
+			"a\n" +
+			"a\t|b\t|c\t|d\n" +
+			"a\t|b\t|c\t|d\t|e\n",
+	},
+}
+
+func Test(t *testing.T) {
+	for _, e := range tests {
+		check(t, e.testname, e.minwidth, e.tabwidth, e.padding, e.padchar, e.flags, e.src, e.expected)
+	}
+}
+
+type panicWriter struct{}
+
+func (panicWriter) Write([]byte) (int, error) {
+	panic("cannot write")
+}
+
+func wantPanicString(t *testing.T, want string) {
+	if e := recover(); e != nil {
+		got, ok := e.(string)
+		switch {
+		case !ok:
+			t.Errorf("got %v (%T), want panic string", e, e)
+		case got != want:
+			t.Errorf("wrong panic message: got %q, want %q", got, want)
+		}
+	}
+}
+
+func TestPanicDuringFlush(t *testing.T) {
+	defer wantPanicString(t, "tabwriter: panic during Flush")
+	var p panicWriter
+	w := new(Writer)
+	w.Init(p, 0, 0, 5, ' ', 0)
+	io.WriteString(w, "a")
+	w.Flush()
+	t.Errorf("failed to panic during Flush")
+}
+
+func TestPanicDuringWrite(t *testing.T) {
+	defer wantPanicString(t, "tabwriter: panic during Write")
+	var p panicWriter
+	w := new(Writer)
+	w.Init(p, 0, 0, 5, ' ', 0)
+	io.WriteString(w, "a\n\n") // the second \n triggers a call to w.Write and thus a panic
+	t.Errorf("failed to panic during Write")
+}
+
+func BenchmarkTable(b *testing.B) {
+	for _, w := range [...]int{1, 10, 100} {
+		// Build a line with w cells.
+		line := bytes.Repeat([]byte("a\t"), w)
+		line = append(line, '\n')
+		for _, h := range [...]int{10, 1000, 100000} {
+			b.Run(fmt.Sprintf("%dx%d", w, h), func(b *testing.B) {
+				b.Run("new", func(b *testing.B) {
+					b.ReportAllocs()
+					for i := 0; i < b.N; i++ {
+						w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+						// Write the line h times.
+						for j := 0; j < h; j++ {
+							w.Write(line)
+						}
+						w.Flush()
+					}
+				})
+
+				b.Run("reuse", func(b *testing.B) {
+					b.ReportAllocs()
+					w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+					for i := 0; i < b.N; i++ {
+						// Write the line h times.
+						for j := 0; j < h; j++ {
+							w.Write(line)
+						}
+						w.Flush()
+					}
+				})
+			})
+		}
+	}
+}
+
+func BenchmarkPyramid(b *testing.B) {
+	for _, x := range [...]int{10, 100, 1000} {
+		// Build a line with x cells.
+		line := bytes.Repeat([]byte("a\t"), x)
+		b.Run(fmt.Sprintf("%d", x), func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+				// Write increasing prefixes of that line.
+				for j := 0; j < x; j++ {
+					w.Write(line[:j*2])
+					w.Write([]byte{'\n'})
+				}
+				w.Flush()
+			}
+		})
+	}
+}
+
+func BenchmarkRagged(b *testing.B) {
+	var lines [8][]byte
+	for i, w := range [8]int{6, 2, 9, 5, 5, 7, 3, 8} {
+		// Build a line with w cells.
+		lines[i] = bytes.Repeat([]byte("a\t"), w)
+	}
+	for _, h := range [...]int{10, 100, 1000} {
+		b.Run(fmt.Sprintf("%d", h), func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+				// Write the lines in turn h times.
+				for j := 0; j < h; j++ {
+					w.Write(lines[j%len(lines)])
+					w.Write([]byte{'\n'})
+				}
+				w.Flush()
+			}
+		})
+	}
+}
+
+const codeSnippet = `
+some command
+
+foo	# aligned
+barbaz	# comments
+
+but
+mostly
+single
+cell
+lines
+`
+
+func BenchmarkCode(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+		// The code is small, so it's reasonable for the tabwriter user
+		// to write it all at once, or buffer the writes.
+		w.Write([]byte(codeSnippet))
+		w.Flush()
+	}
+}