Module: Mapi::RTF

Defined in:

lib/mapi/rtf.rb

Overview

Introduction

The RTF module contains a few helper functions for dealing with rtf in mapi messages: rtfdecompr, and rtf2html.

Both were ported from their original C versions for simplicity’s sake.

Defined Under Namespace

Classes: Converter, Tokenizer

Constant Summary

RTF_PREBUF =

"{\\rtf1\\ansi\\mac\\deff0\\deftab720{\\fonttbl;}" \
"{\\f0\\fnil \\froman \\fswiss \\fmodern \\fscript " \
"\\fdecor MS Sans SerifSymbolArialTimes New RomanCourier" \
"{\\colortbl\\red0\\green0\\blue0\n\r\\par " \
"\\pard\\plain\\f0\\fs20\\b\\i\\u\\tab\\tx"

Class Method Summary

• .rtf2html(rtf) ⇒ Object

  Note, this is a conversion of the original C code.

• .rtfdecompr(data) ⇒ Object

  Decompresses compressed rtf data, as found in the mapi property PR_RTF_COMPRESSED.

Class Method Details

.rtf2html(rtf) ⇒ Object

Note, this is a conversion of the original C code. Not great - needs tests and some refactoring, and an attempt to correct some inaccuracies. Hacky but works.

Returns nil if it doesn’t look like an rtf encapsulated rtf.

Some cases that the original didn’t deal with have been patched up, eg from this chunk, where there are tags outside of the htmlrtf ignore block.

“<br />\htmlrtf \line \htmlrtf0 \line {*\htmltag84 <a href…”

We take the approach of ignoring all rtf tags not explicitly handled. A proper parse tree would be nicer to work with. will need to look for ruby rtf library

Some of the original comment to the c code is excerpted here:

Sometimes in MAPI, the PR_BODY_HTML property contains the HTML of a message. But more usually, the HTML is encoded inside the RTF body (which you get in the PR_RTF_COMPRESSED property). These routines concern the decoding of the HTML from this RTF body.

An encoded htmlrtf file is a valid RTF document, but which contains additional html markup information in its comments, and sometimes contains the equivalent rtf markup outside the comments. Therefore, when it is displayed by a plain simple RTF reader, the html comments are ignored and only the rtf markup has effect. Typically, this rtf markup is not as rich as the html markup would have been. But for an html-aware reader (such as the code below), we can ignore all the rtf markup, and extract the html markup out of the comments, and get a valid html document.

There are actually two kinds of html markup in comments. Most of them are prefixed by “*htmltagNNN”, for some number NNN. But sometimes there’s one prefixed by “*mhtmltagNNN” followed by “*htmltagNNN”. In this case, the two are equivalent, but the m-tag is for a MIME Multipart/Mixed Message and contains tags that refer to content-ids (e.g. img src=“cid:072344a7”) while the normal tag just refers to a name (e.g. img src=“fred.jpg”) The code below keeps the m-tag and discards the normal tag. If there are any m-tags like this, then the message also contains an attachment with a PR_CONTENT_ID property e.g. “072344a7”. Actually, sometimes the m-tag is e.g. img src=“outlook/welcome.html” and the attachment has a PR_CONTENT_LOCATION “outlook/welcome.html” instead of a PR_CONTENT_ID.

# File 'lib/mapi/rtf.rb', line 229

def rtf2html rtf
	scan = StringScanner.new rtf
	# require \fromhtml. is this worth keeping? apparently you see \\fromtext if it
	# was converted from plain text. 
	return nil unless rtf["\\fromhtml"]
	html = ''
	ignore_tag = nil
	# skip up to the first htmltag. return nil if we don't ever find one
	return nil unless scan.scan_until /(?=\{\\\*\\htmltag)/
	until scan.empty?
		if scan.scan /\{/
		elsif scan.scan /\}/
		elsif scan.scan /\\\*\\htmltag(\d+) ?/
			#p scan[1]
			if ignore_tag == scan[1]
				scan.scan_until /\}/
				ignore_tag = nil
			end
		elsif scan.scan /\\\*\\mhtmltag(\d+) ?/
				ignore_tag = scan[1]
		elsif scan.scan /\\par ?/
			html << "\r\n"
		elsif scan.scan /\\tab ?/
			html << "\t"
		elsif scan.scan /\\'([0-9A-Za-z]{2})/
			html << scan[1].hex.chr
		elsif scan.scan /\\pntext/
			scan.scan_until /\}/
		elsif scan.scan /\\htmlrtf/
			scan.scan_until /\\htmlrtf0 ?/
		# a generic throw away unknown tags thing.
		# the above 2 however, are handled specially
		elsif scan.scan /\\[a-z-]+(\d+)? ?/
		#elsif scan.scan /\\li(\d+) ?/
		#elsif scan.scan /\\fi-(\d+) ?/
		elsif scan.scan /[\r\n]/
		elsif scan.scan /\\([{}\\])/
			html << scan[1]
		elsif scan.scan /(.)/
			html << scan[1]
		else
			p :wtf
		end
	end
	html.strip.empty? ? nil : html
end

.rtfdecompr(data) ⇒ Object

Decompresses compressed rtf data, as found in the mapi property PR_RTF_COMPRESSED. Code converted from my C version, which in turn I wrote from a Java source, in JTNEF I believe.

C version was modified to use circular buffer for back references, instead of the optimization of the Java version to index directly into output buffer. This was in preparation to support streaming in a read/write neutral fashion.

# File 'lib/mapi/rtf.rb', line 140

def rtfdecompr data
	io  = StringIO.new data
	buf = RTF_PREBUF + "\x00" * (4096 - RTF_PREBUF.length)
	wp  = RTF_PREBUF.length
	rtf = ''

	# get header fields (as defined in RTFLIB.H)
	compr_size, uncompr_size, magic, crc32 = io.read(16).unpack 'V*'
	#warn "compressed-RTF data size mismatch" unless io.size == data.compr_size + 4

	# process the data
	case magic
	when 0x414c454d # "MELA" magic number that identifies the stream as a uncompressed stream
		rtf = io.read uncompr_size
	when 0x75465a4c # "LZFu" magic number that identifies the stream as a compressed stream
		flag_count = -1
		flags = nil
		while rtf.length < uncompr_size and !io.eof?
			# each flag byte flags 8 literals/references, 1 per bit
			flags = ((flag_count += 1) % 8 == 0) ? io.getbyte : flags >> 1
			if 1 == (flags & 1) # each flag bit is 1 for reference, 0 for literal
				rp, l = io.getbyte, io.getbyte
				# offset is a 12 byte number. 2^12 is 4096, so thats fine
				rp = (rp << 4) | (l >> 4) # the offset relative to block start
				l = (l & 0xf) + 2 # the number of bytes to copy
				l.times do
					rtf << buf[wp] = buf[rp]
					wp = (wp + 1) % 4096
					rp = (rp + 1) % 4096
				end
			else
				rtf << buf[wp] = io.getbyte.chr
				wp = (wp + 1) % 4096
			end
		end
	else # unknown magic number
		raise "Unknown compression type (magic number 0x%08x)" % magic
	end
	
	# not sure if its due to a bug in the above code. doesn't seem to be
	# in my tests, but sometimes there's a trailing null. we chomp it here,
	# which actually makes the resultant rtf smaller than its advertised
	# size (+uncompr_size+).
	rtf.chomp! 0.chr
	rtf
end