mirror of
https://github.com/strongdm/comply
synced 2024-11-14 03:44:55 +00:00
588 lines
17 KiB
Go
588 lines
17 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file is mostly a copy of the go standard library text/tabwriter. With
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// the additional stripping of ansi control characters for width calculations.
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// Package tabwriter implements a write filter (tabwriter.Writer) that
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// translates tabbed columns in input into properly aligned text.
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//
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// The package is using the Elastic Tabstops algorithm described at
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// http://nickgravgaard.com/elastictabstops/index.html.
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//
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package tabwriter
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import (
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"bytes"
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"io"
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"unicode/utf8"
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"github.com/lunixbochs/vtclean"
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)
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// ----------------------------------------------------------------------------
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// Filter implementation
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// A cell represents a segment of text terminated by tabs or line breaks.
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// The text itself is stored in a separate buffer; cell only describes the
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// segment's size in bytes, its width in runes, and whether it's an htab
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// ('\t') terminated cell.
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//
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type cell struct {
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size int // cell size in bytes
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width int // cell width in runes
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htab bool // true if the cell is terminated by an htab ('\t')
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}
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// A Writer is a filter that inserts padding around tab-delimited
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// columns in its input to align them in the output.
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//
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// The Writer treats incoming bytes as UTF-8 encoded text consisting
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// of cells terminated by (horizontal or vertical) tabs or line
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// breaks (newline or formfeed characters). Cells in adjacent lines
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// constitute a column. The Writer inserts padding as needed to
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// make all cells in a column have the same width, effectively
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// aligning the columns. It assumes that all characters have the
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// same width except for tabs for which a tabwidth must be specified.
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// Note that cells are tab-terminated, not tab-separated: trailing
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// non-tab text at the end of a line does not form a column cell.
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//
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// The Writer assumes that all Unicode code points have the same width;
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// this may not be true in some fonts.
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//
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// If DiscardEmptyColumns is set, empty columns that are terminated
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// entirely by vertical (or "soft") tabs are discarded. Columns
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// terminated by horizontal (or "hard") tabs are not affected by
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// this flag.
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//
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// If a Writer is configured to filter HTML, HTML tags and entities
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// are passed through. The widths of tags and entities are
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// assumed to be zero (tags) and one (entities) for formatting purposes.
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//
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// A segment of text may be escaped by bracketing it with Escape
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// characters. The tabwriter passes escaped text segments through
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// unchanged. In particular, it does not interpret any tabs or line
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// breaks within the segment. If the StripEscape flag is set, the
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// Escape characters are stripped from the output; otherwise they
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// are passed through as well. For the purpose of formatting, the
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// width of the escaped text is always computed excluding the Escape
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// characters.
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//
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// The formfeed character ('\f') acts like a newline but it also
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// terminates all columns in the current line (effectively calling
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// Flush). Cells in the next line start new columns. Unless found
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// inside an HTML tag or inside an escaped text segment, formfeed
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// characters appear as newlines in the output.
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//
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// The Writer must buffer input internally, because proper spacing
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// of one line may depend on the cells in future lines. Clients must
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// call Flush when done calling Write.
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//
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type Writer struct {
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// configuration
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output io.Writer
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minwidth int
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tabwidth int
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padding int
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padbytes [8]byte
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flags uint
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// current state
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buf bytes.Buffer // collected text excluding tabs or line breaks
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pos int // buffer position up to which cell.width of incomplete cell has been computed
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cell cell // current incomplete cell; cell.width is up to buf[pos] excluding ignored sections
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endChar byte // terminating char of escaped sequence (Escape for escapes, '>', ';' for HTML tags/entities, or 0)
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lines [][]cell // list of lines; each line is a list of cells
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widths []int // list of column widths in runes - re-used during formatting
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alignment map[int]uint // column alignment
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}
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func (b *Writer) addLine() { b.lines = append(b.lines, []cell{}) }
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// Reset the current state.
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func (b *Writer) reset() {
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b.buf.Reset()
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b.pos = 0
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b.cell = cell{}
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b.endChar = 0
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b.lines = b.lines[0:0]
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b.widths = b.widths[0:0]
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b.alignment = make(map[int]uint)
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b.addLine()
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}
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// Internal representation (current state):
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//
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// - all text written is appended to buf; tabs and line breaks are stripped away
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// - at any given time there is a (possibly empty) incomplete cell at the end
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// (the cell starts after a tab or line break)
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// - cell.size is the number of bytes belonging to the cell so far
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// - cell.width is text width in runes of that cell from the start of the cell to
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// position pos; html tags and entities are excluded from this width if html
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// filtering is enabled
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// - the sizes and widths of processed text are kept in the lines list
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// which contains a list of cells for each line
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// - the widths list is a temporary list with current widths used during
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// formatting; it is kept in Writer because it's re-used
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//
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// |<---------- size ---------->|
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// | |
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// |<- width ->|<- ignored ->| |
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// | | | |
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// [---processed---tab------------<tag>...</tag>...]
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// ^ ^ ^
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// | | |
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// buf start of incomplete cell pos
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// Formatting can be controlled with these flags.
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const (
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// Ignore html tags and treat entities (starting with '&'
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// and ending in ';') as single characters (width = 1).
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FilterHTML uint = 1 << iota
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// Strip Escape characters bracketing escaped text segments
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// instead of passing them through unchanged with the text.
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StripEscape
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// Force right-alignment of cell content.
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// Default is left-alignment.
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AlignRight
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// Handle empty columns as if they were not present in
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// the input in the first place.
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DiscardEmptyColumns
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// Always use tabs for indentation columns (i.e., padding of
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// leading empty cells on the left) independent of padchar.
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TabIndent
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// Print a vertical bar ('|') between columns (after formatting).
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// Discarded columns appear as zero-width columns ("||").
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Debug
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)
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// A Writer must be initialized with a call to Init. The first parameter (output)
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// specifies the filter output. The remaining parameters control the formatting:
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//
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// minwidth minimal cell width including any padding
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// tabwidth width of tab characters (equivalent number of spaces)
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// padding padding added to a cell before computing its width
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// padchar ASCII char used for padding
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// if padchar == '\t', the Writer will assume that the
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// width of a '\t' in the formatted output is tabwidth,
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// and cells are left-aligned independent of align_left
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// (for correct-looking results, tabwidth must correspond
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// to the tab width in the viewer displaying the result)
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// flags formatting control
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//
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func (b *Writer) Init(output io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *Writer {
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if minwidth < 0 || tabwidth < 0 || padding < 0 {
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panic("negative minwidth, tabwidth, or padding")
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}
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b.output = output
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b.minwidth = minwidth
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b.tabwidth = tabwidth
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b.padding = padding
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for i := range b.padbytes {
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b.padbytes[i] = padchar
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}
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if padchar == '\t' {
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// tab padding enforces left-alignment
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flags &^= AlignRight
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}
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b.flags = flags
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b.reset()
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return b
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}
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// debugging support (keep code around)
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func (b *Writer) dump() {
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pos := 0
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for i, line := range b.lines {
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print("(", i, ") ")
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for _, c := range line {
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print("[", string(b.buf.Bytes()[pos:pos+c.size]), "]")
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pos += c.size
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}
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print("\n")
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}
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print("\n")
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}
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// local error wrapper so we can distinguish errors we want to return
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// as errors from genuine panics (which we don't want to return as errors)
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type osError struct {
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err error
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}
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func (b *Writer) write0(buf []byte) {
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n, err := b.output.Write(buf)
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if n != len(buf) && err == nil {
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err = io.ErrShortWrite
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}
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if err != nil {
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panic(osError{err})
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}
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}
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func (b *Writer) writeN(src []byte, n int) {
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for n > len(src) {
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b.write0(src)
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n -= len(src)
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}
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b.write0(src[0:n])
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}
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var (
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newline = []byte{'\n'}
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tabs = []byte("\t\t\t\t\t\t\t\t")
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)
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func (b *Writer) writePadding(textw, cellw int, useTabs bool) {
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if b.padbytes[0] == '\t' || useTabs {
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// padding is done with tabs
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if b.tabwidth == 0 {
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return // tabs have no width - can't do any padding
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}
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// make cellw the smallest multiple of b.tabwidth
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cellw = (cellw + b.tabwidth - 1) / b.tabwidth * b.tabwidth
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n := cellw - textw // amount of padding
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if n < 0 {
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panic("internal error")
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}
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b.writeN(tabs, (n+b.tabwidth-1)/b.tabwidth)
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return
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}
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// padding is done with non-tab characters
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b.writeN(b.padbytes[0:], cellw-textw)
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}
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var vbar = []byte{'|'}
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func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int) {
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pos = pos0
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for i := line0; i < line1; i++ {
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line := b.lines[i]
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// if TabIndent is set, use tabs to pad leading empty cells
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useTabs := b.flags&TabIndent != 0
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for j, c := range line {
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if j > 0 && b.flags&Debug != 0 {
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// indicate column break
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b.write0(vbar)
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}
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if c.size == 0 {
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// empty cell
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if j < len(b.widths) {
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b.writePadding(c.width, b.widths[j], useTabs)
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}
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} else {
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// non-empty cell
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useTabs = false
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alignColumnRight := b.alignment[j] == AlignRight
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if (b.flags&AlignRight == 0) && !alignColumnRight { // align left
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b.write0(b.buf.Bytes()[pos : pos+c.size])
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pos += c.size
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if j < len(b.widths) {
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b.writePadding(c.width, b.widths[j], false)
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}
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} else if alignColumnRight && j < len(b.widths) {
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// just this column
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internalSize := b.widths[j] - b.padding
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if j < len(b.widths) {
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b.writePadding(c.width, internalSize, false)
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}
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b.write0(b.buf.Bytes()[pos : pos+c.size])
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if b.padding > 0 {
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b.writePadding(0, b.padding, false)
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}
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pos += c.size
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} else { // align right
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if j < len(b.widths) {
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b.writePadding(c.width, b.widths[j], false)
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}
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b.write0(b.buf.Bytes()[pos : pos+c.size])
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pos += c.size
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}
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}
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}
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if i+1 == len(b.lines) {
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// last buffered line - we don't have a newline, so just write
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// any outstanding buffered data
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b.write0(b.buf.Bytes()[pos : pos+b.cell.size])
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pos += b.cell.size
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} else {
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// not the last line - write newline
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b.write0(newline)
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}
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}
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return
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}
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// Format the text between line0 and line1 (excluding line1); pos
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// is the buffer position corresponding to the beginning of line0.
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// Returns the buffer position corresponding to the beginning of
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// line1 and an error, if any.
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//
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func (b *Writer) format(pos0 int, line0, line1 int) (pos int) {
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pos = pos0
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column := len(b.widths)
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for this := line0; this < line1; this++ {
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line := b.lines[this]
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if column < len(line)-1 {
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// cell exists in this column => this line
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// has more cells than the previous line
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// (the last cell per line is ignored because cells are
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// tab-terminated; the last cell per line describes the
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// text before the newline/formfeed and does not belong
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// to a column)
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// print unprinted lines until beginning of block
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pos = b.writeLines(pos, line0, this)
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line0 = this
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// column block begin
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width := b.minwidth // minimal column width
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discardable := true // true if all cells in this column are empty and "soft"
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for ; this < line1; this++ {
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line = b.lines[this]
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if column < len(line)-1 {
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// cell exists in this column
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c := line[column]
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// update width
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if w := c.width + b.padding; w > width {
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width = w
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}
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// update discardable
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if c.width > 0 || c.htab {
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discardable = false
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}
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} else {
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break
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}
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}
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// column block end
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// discard empty columns if necessary
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if discardable && b.flags&DiscardEmptyColumns != 0 {
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width = 0
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}
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// format and print all columns to the right of this column
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// (we know the widths of this column and all columns to the left)
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b.widths = append(b.widths, width) // push width
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pos = b.format(pos, line0, this)
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b.widths = b.widths[0 : len(b.widths)-1] // pop width
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line0 = this
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}
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}
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// print unprinted lines until end
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return b.writeLines(pos, line0, line1)
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}
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// Append text to current cell.
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func (b *Writer) append(text []byte) {
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b.buf.Write(text)
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b.cell.size += len(text)
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}
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// Update the cell width.
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func (b *Writer) updateWidth() {
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// ---- Changes here -----
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newChars := b.buf.Bytes()[b.pos:b.buf.Len()]
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cleaned := vtclean.Clean(string(newChars), false) // false to strip colors
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b.cell.width += utf8.RuneCount([]byte(cleaned))
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// --- end of changes ----
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b.pos = b.buf.Len()
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}
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// To escape a text segment, bracket it with Escape characters.
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// For instance, the tab in this string "Ignore this tab: \xff\t\xff"
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// does not terminate a cell and constitutes a single character of
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// width one for formatting purposes.
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//
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// The value 0xff was chosen because it cannot appear in a valid UTF-8 sequence.
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//
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const Escape = '\xff'
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// Start escaped mode.
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func (b *Writer) startEscape(ch byte) {
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switch ch {
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case Escape:
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b.endChar = Escape
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case '<':
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b.endChar = '>'
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case '&':
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b.endChar = ';'
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}
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}
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// Terminate escaped mode. If the escaped text was an HTML tag, its width
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// is assumed to be zero for formatting purposes; if it was an HTML entity,
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// its width is assumed to be one. In all other cases, the width is the
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// unicode width of the text.
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//
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func (b *Writer) endEscape() {
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switch b.endChar {
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case Escape:
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b.updateWidth()
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if b.flags&StripEscape == 0 {
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b.cell.width -= 2 // don't count the Escape chars
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}
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case '>': // tag of zero width
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case ';':
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b.cell.width++ // entity, count as one rune
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}
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b.pos = b.buf.Len()
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b.endChar = 0
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}
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// Terminate the current cell by adding it to the list of cells of the
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// current line. Returns the number of cells in that line.
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//
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func (b *Writer) terminateCell(htab bool) int {
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b.cell.htab = htab
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line := &b.lines[len(b.lines)-1]
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*line = append(*line, b.cell)
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b.cell = cell{}
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return len(*line)
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}
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func handlePanic(err *error, op string) {
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if e := recover(); e != nil {
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if nerr, ok := e.(osError); ok {
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*err = nerr.err
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return
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}
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panic("tabwriter: panic during " + op)
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}
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}
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// Flush should be called after the last call to Write to ensure
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// that any data buffered in the Writer is written to output. Any
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// incomplete escape sequence at the end is considered
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// complete for formatting purposes.
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//
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func (b *Writer) Flush() (err error) {
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defer b.reset() // even in the presence of errors
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defer handlePanic(&err, "Flush")
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// add current cell if not empty
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if b.cell.size > 0 {
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if b.endChar != 0 {
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// inside escape - terminate it even if incomplete
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b.endEscape()
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}
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b.terminateCell(false)
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}
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// format contents of buffer
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b.format(0, 0, len(b.lines))
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return
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}
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var hbar = []byte("---\n")
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// SetColumnAlignRight will mark a particular column as align right.
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// This is reset on the next flush.
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func (b *Writer) SetColumnAlignRight(column int) {
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b.alignment[column] = AlignRight
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}
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// Write writes buf to the writer b.
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// The only errors returned are ones encountered
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// while writing to the underlying output stream.
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//
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func (b *Writer) Write(buf []byte) (n int, err error) {
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defer handlePanic(&err, "Write")
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// split text into cells
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n = 0
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for i, ch := range buf {
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if b.endChar == 0 {
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// outside escape
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switch ch {
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case '\t', '\v', '\n', '\f':
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// end of cell
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b.append(buf[n:i])
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b.updateWidth()
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n = i + 1 // ch consumed
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ncells := b.terminateCell(ch == '\t')
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if ch == '\n' || ch == '\f' {
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// terminate line
|
|
b.addLine()
|
|
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.
|
|
if err = b.Flush(); err != nil {
|
|
return
|
|
}
|
|
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)
|
|
}
|