nroff: Add support for 'diagram' XML element for protocol headers.

This will be used in documentation for an upcoming change, to document
how Geneve OVN options are encoded.

The code in this change is from a series (not yet submitted) that makes
much more extensive use of it for documenting protocol headers.

Signed-off-by: Ben Pfaff <blp@nicira.com>

python/build/nroff.py

@@ -105,6 +105,101 @@ def pre_to_nroff(nodes, para, font):
     s += '.fi\n'
     return s
 
+def diagram_header_to_nroff(header_node):
+    header_fields = []
+    i = 0
+    for node in header_node.childNodes:
+        if node.nodeType == node.ELEMENT_NODE and node.tagName == 'bits':
+            name = node.attributes['name'].nodeValue
+            width = node.attributes['width'].nodeValue
+            above = node.getAttribute('above')
+            below = node.getAttribute('below')
+            fill = node.getAttribute('fill')
+            header_fields += [{"name": name,
+                              "tag": "B%d" % i,
+                              "width": width,
+                              "above": above,
+                              "below": below,
+                              "fill": fill}]
+            i += 1
+        elif node.nodeType == node.COMMENT_NODE:
+            pass
+        elif node.nodeType == node.TEXT_NODE and node.data.isspace():
+            pass
+        else:
+            fatal("unknown node %s in diagram <header> element" % node)
+
+    pic_s = ""
+    for f in header_fields:
+        pic_s += "  %s: box \"%s\" width %s" % (f['tag'], f['name'], f['width'])
+        if f['fill'] == 'yes':
+            pic_s += " fill"
+        pic_s += '\n'
+    for f in header_fields:
+        pic_s += "  \"%s\" at %s.n above\n" % (f['above'], f['tag'])
+        pic_s += "  \"%s\" at %s.s below\n" % (f['below'], f['tag'])
+    name = header_node.getAttribute('name')
+    if name == "":
+        visible = " invis"
+    else:
+        visible = ""
+    pic_s += "line <->%s \"%s\" above " % (visible, name)
+    pic_s += "from %s.nw + (0,textht) " % header_fields[0]['tag']
+    pic_s += "to %s.ne + (0,textht)\n" % header_fields[-1]['tag']
+
+    text_s = ""
+    for f in header_fields:
+        text_s += """.IP \\(bu
+%s bits""" % (f['above'])
+        if f['name']:
+            text_s += ": %s" % f['name']
+        if f['below']:
+            text_s += " (%s)" % f['below']
+        text_s += "\n"
+    return pic_s, text_s
+
+def diagram_to_nroff(nodes, para):
+    pic_s = ''
+    text_s = ''
+    move = False
+    for node in nodes:
+        if node.nodeType == node.ELEMENT_NODE and node.tagName == 'header':
+            if move:
+                pic_s += "move .1\n"
+                text_s += ".sp\n"
+            pic_header, text_header = diagram_header_to_nroff(node)
+            pic_s += "[\n" + pic_header + "]\n"
+            text_s += text_header
+            move = True
+        elif node.nodeType == node.ELEMENT_NODE and node.tagName == 'nospace':
+            move = False
+        elif node.nodeType == node.ELEMENT_NODE and node.tagName == 'dots':
+            pic_s += "move .1\n"
+            pic_s += '". . ." ljust\n'
+            text_s += ".sp\n"
+        elif node.nodeType == node.COMMENT_NODE:
+            pass
+        elif node.nodeType == node.TEXT_NODE and node.data.isspace():
+            pass
+        else:
+            fatal("unknown node %s in diagram <header> element" % node)
+    return para + """
+.\\" check if in troff mode (TTY)
+.if t \{
+.PS
+boxht = .2
+textht = 1/6
+fillval = .2
+""" + pic_s + """\
+.PE
+\\}
+.\\" check if in nroff mode:
+.if n \{
+.RS
+""" + text_s + """\
+.RE
+\\}"""
+
 def block_xml_to_nroff(nodes, para='.PP'):
     s = ''
     for node in nodes:
@@ -176,6 +271,8 @@ def block_xml_to_nroff(nodes, para='.PP'):
                 else:
                     font = r'\fB'
                 s += pre_to_nroff(node.childNodes, para, font)
+            elif node.tagName == 'diagram':
+                s += diagram_to_nroff(node.childNodes, para)
             else:
                 s += inline_xml_to_nroff(node, r'\fR')
         elif node.nodeType == node.COMMENT_NODE: