node.go

Documentation: golang.org/x/net/html

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package html
     6  
     7  import (
     8  	"golang.org/x/net/html/atom"
     9  )
    10  
    11  // A NodeType is the type of a Node.
    12  type NodeType uint32
    13  
    14  const (
    15  	ErrorNode NodeType = iota
    16  	TextNode
    17  	DocumentNode
    18  	ElementNode
    19  	CommentNode
    20  	DoctypeNode
    21  	// RawNode nodes are not returned by the parser, but can be part of the
    22  	// Node tree passed to func Render to insert raw HTML (without escaping).
    23  	// If so, this package makes no guarantee that the rendered HTML is secure
    24  	// (from e.g. Cross Site Scripting attacks) or well-formed.
    25  	RawNode
    26  	scopeMarkerNode
    27  )
    28  
    29  // Section 12.2.4.3 says "The markers are inserted when entering applet,
    30  // object, marquee, template, td, th, and caption elements, and are used
    31  // to prevent formatting from "leaking" into applet, object, marquee,
    32  // template, td, th, and caption elements".
    33  var scopeMarker = Node{Type: scopeMarkerNode}
    34  
    35  // A Node consists of a NodeType and some Data (tag name for element nodes,
    36  // content for text) and are part of a tree of Nodes. Element nodes may also
    37  // have a Namespace and contain a slice of Attributes. Data is unescaped, so
    38  // that it looks like "a<b" rather than "a&lt;b". For element nodes, DataAtom
    39  // is the atom for Data, or zero if Data is not a known tag name.
    40  //
    41  // An empty Namespace implies a "http://www.w3.org/1999/xhtml" namespace.
    42  // Similarly, "math" is short for "http://www.w3.org/1998/Math/MathML", and
    43  // "svg" is short for "http://www.w3.org/2000/svg".
    44  type Node struct {
    45  	Parent, FirstChild, LastChild, PrevSibling, NextSibling *Node
    46  
    47  	Type      NodeType
    48  	DataAtom  atom.Atom
    49  	Data      string
    50  	Namespace string
    51  	Attr      []Attribute
    52  }
    53  
    54  // InsertBefore inserts newChild as a child of n, immediately before oldChild
    55  // in the sequence of n's children. oldChild may be nil, in which case newChild
    56  // is appended to the end of n's children.
    57  //
    58  // It will panic if newChild already has a parent or siblings.
    59  func (n *Node) InsertBefore(newChild, oldChild *Node) {
    60  	if newChild.Parent != nil || newChild.PrevSibling != nil || newChild.NextSibling != nil {
    61  		panic("html: InsertBefore called for an attached child Node")
    62  	}
    63  	var prev, next *Node
    64  	if oldChild != nil {
    65  		prev, next = oldChild.PrevSibling, oldChild
    66  	} else {
    67  		prev = n.LastChild
    68  	}
    69  	if prev != nil {
    70  		prev.NextSibling = newChild
    71  	} else {
    72  		n.FirstChild = newChild
    73  	}
    74  	if next != nil {
    75  		next.PrevSibling = newChild
    76  	} else {
    77  		n.LastChild = newChild
    78  	}
    79  	newChild.Parent = n
    80  	newChild.PrevSibling = prev
    81  	newChild.NextSibling = next
    82  }
    83  
    84  // AppendChild adds a node c as a child of n.
    85  //
    86  // It will panic if c already has a parent or siblings.
    87  func (n *Node) AppendChild(c *Node) {
    88  	if c.Parent != nil || c.PrevSibling != nil || c.NextSibling != nil {
    89  		panic("html: AppendChild called for an attached child Node")
    90  	}
    91  	last := n.LastChild
    92  	if last != nil {
    93  		last.NextSibling = c
    94  	} else {
    95  		n.FirstChild = c
    96  	}
    97  	n.LastChild = c
    98  	c.Parent = n
    99  	c.PrevSibling = last
   100  }
   101  
   102  // RemoveChild removes a node c that is a child of n. Afterwards, c will have
   103  // no parent and no siblings.
   104  //
   105  // It will panic if c's parent is not n.
   106  func (n *Node) RemoveChild(c *Node) {
   107  	if c.Parent != n {
   108  		panic("html: RemoveChild called for a non-child Node")
   109  	}
   110  	if n.FirstChild == c {
   111  		n.FirstChild = c.NextSibling
   112  	}
   113  	if c.NextSibling != nil {
   114  		c.NextSibling.PrevSibling = c.PrevSibling
   115  	}
   116  	if n.LastChild == c {
   117  		n.LastChild = c.PrevSibling
   118  	}
   119  	if c.PrevSibling != nil {
   120  		c.PrevSibling.NextSibling = c.NextSibling
   121  	}
   122  	c.Parent = nil
   123  	c.PrevSibling = nil
   124  	c.NextSibling = nil
   125  }
   126  
   127  // reparentChildren reparents all of src's child nodes to dst.
   128  func reparentChildren(dst, src *Node) {
   129  	for {
   130  		child := src.FirstChild
   131  		if child == nil {
   132  			break
   133  		}
   134  		src.RemoveChild(child)
   135  		dst.AppendChild(child)
   136  	}
   137  }
   138  
   139  // clone returns a new node with the same type, data and attributes.
   140  // The clone has no parent, no siblings and no children.
   141  func (n *Node) clone() *Node {
   142  	m := &Node{
   143  		Type:     n.Type,
   144  		DataAtom: n.DataAtom,
   145  		Data:     n.Data,
   146  		Attr:     make([]Attribute, len(n.Attr)),
   147  	}
   148  	copy(m.Attr, n.Attr)
   149  	return m
   150  }
   151  
   152  // nodeStack is a stack of nodes.
   153  type nodeStack []*Node
   154  
   155  // pop pops the stack. It will panic if s is empty.
   156  func (s *nodeStack) pop() *Node {
   157  	i := len(*s)
   158  	n := (*s)[i-1]
   159  	*s = (*s)[:i-1]
   160  	return n
   161  }
   162  
   163  // top returns the most recently pushed node, or nil if s is empty.
   164  func (s *nodeStack) top() *Node {
   165  	if i := len(*s); i > 0 {
   166  		return (*s)[i-1]
   167  	}
   168  	return nil
   169  }
   170  
   171  // index returns the index of the top-most occurrence of n in the stack, or -1
   172  // if n is not present.
   173  func (s *nodeStack) index(n *Node) int {
   174  	for i := len(*s) - 1; i >= 0; i-- {
   175  		if (*s)[i] == n {
   176  			return i
   177  		}
   178  	}
   179  	return -1
   180  }
   181  
   182  // contains returns whether a is within s.
   183  func (s *nodeStack) contains(a atom.Atom) bool {
   184  	for _, n := range *s {
   185  		if n.DataAtom == a && n.Namespace == "" {
   186  			return true
   187  		}
   188  	}
   189  	return false
   190  }
   191  
   192  // insert inserts a node at the given index.
   193  func (s *nodeStack) insert(i int, n *Node) {
   194  	(*s) = append(*s, nil)
   195  	copy((*s)[i+1:], (*s)[i:])
   196  	(*s)[i] = n
   197  }
   198  
   199  // remove removes a node from the stack. It is a no-op if n is not present.
   200  func (s *nodeStack) remove(n *Node) {
   201  	i := s.index(n)
   202  	if i == -1 {
   203  		return
   204  	}
   205  	copy((*s)[i:], (*s)[i+1:])
   206  	j := len(*s) - 1
   207  	(*s)[j] = nil
   208  	*s = (*s)[:j]
   209  }
   210  
   211  type insertionModeStack []insertionMode
   212  
   213  func (s *insertionModeStack) pop() (im insertionMode) {
   214  	i := len(*s)
   215  	im = (*s)[i-1]
   216  	*s = (*s)[:i-1]
   217  	return im
   218  }
   219  
   220  func (s *insertionModeStack) top() insertionMode {
   221  	if i := len(*s); i > 0 {
   222  		return (*s)[i-1]
   223  	}
   224  	return nil
   225  }
   226
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