mimetex.c

完美的在线教育系统

/****************************************************************************
 *
 * Copyright(c) 2002-2006, John Forkosh Associates, Inc. All rights reserved.
 * --------------------------------------------------------------------------
 * This file is part of mimeTeX, which is free software. You may redistribute
 * and/or modify it under the terms of the GNU General Public License,
 * version 2 or later, as published by the Free Software Foundation.
 *      MimeTeX is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY, not even the implied warranty of MERCHANTABILITY.
 * See the GNU General Public License for specific details.
 *      By using mimeTeX, you warrant that you have read, understood and
 * agreed to these terms and conditions, and that you possess the legal
 * right and ability to enter into this agreement and to use mimeTeX
 * in accordance with it.
 *      Your mimeTeX distribution should contain a copy of the GNU General
 * Public License.  If not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA,
 * or point your browser to  http://www.gnu.org/licenses/gpl.html
 * --------------------------------------------------------------------------
 *
 * Purpose:   o	MimeTeX, licensed under the gpl, lets you easily embed
 *		LaTeX math in your html pages.  It parses a LaTeX math
 *		expression and immediately emits the corresponding gif
 *		image, rather than the usual TeX dvi.  And mimeTeX is an
 *		entirely separate little program that doesn't use TeX or
 *		its fonts in any way.  It's just one cgi that you put in
 *		your site's cgi-bin/ directory, with no other dependencies.
 *		So mimeTeX is very easy to install.  And it's equally easy
 *		to use.  Just place an html <img> tag in your document
 *		wherever you want to see the corresponding LaTeX expression.
 *		For example,
 *		 <img src="../cgi-bin/mimetex.cgi?\int_{-\infty}^xe^{-t^2}dt"
 *		  alt="" border=0 align=middle>
 *		immediately generates the corresponding gif image on-the-fly,
 *		displaying the rendered expression wherever you put that
 *		<img> tag.  MimeTeX doesn't need intermediate dvi-to-gif
 *		conversion, and it doesn't clutter up your filesystem with
 *		separate little gif files for each converted expression.
 *		There's also no inherent need to repeatedly write the
 *		cumbersome <img> tag illustrated above.  You can write
 *		your own custom tags, or write a wrapper script around
 *		mimeTeX to simplify the necessary notation.
 *
 * Functions:	===================== Raster Functions ======================
 *	PART2	--- raster constructor functions ---
 *		new_raster(width,height,pixsz)   allocation (and constructor)
 *		new_subraster(width,height,pixsz)allocation (and constructor)
 *		new_chardef()                         allocate chardef struct
 *		delete_raster(rp)        deallocate raster (rp =  raster ptr)
 *		delete_subraster(sp)  deallocate subraster (sp=subraster ptr)
 *		delete_chardef(cp)      deallocate chardef (cp = chardef ptr)
 *		--- primitive (sub)raster functions ---
 *		rastcpy(rp)                           allocate new copy of rp
 *		subrastcpy(sp)                        allocate new copy of sp
 *		rastrot(rp)         new raster rotated right 90 degrees to rp
 *		rastput(target,source,top,left,isopaque)  overlay src on trgt
 *		rastcompose(sp1,sp2,offset2,isalign,isfree) sp2 on top of sp1
 *		rastcat(sp1,sp2,isfree)                  concatanate sp1||sp2
 *		rastack(sp1,sp2,base,space,iscenter,isfree)stack sp2 atop sp1
 *		rastile(tiles,ntiles)      create composite raster from tiles
 *		rastsmash(sp1,sp2,xmin,ymin)      calc #smash pixels sp1||sp2
 *		--- raster "drawing" functions ---
 *		accent_subraster(accent,width,height)       draw \hat\vec\etc
 *		arrow_subraster(width,height,drctn,isBig)    left/right arrow
 *		uparrow_subraster(width,height,drctn,isBig)     up/down arrow
 *		rule_raster(rp,top,left,width,height,type)    draw rule in rp
 *		line_raster(rp,row0,col0,row1,col1,thickness) draw line in rp
 *		line_recurse(rp,row0,col0,row1,col1,thickness)   recurse line
 *		circle_raster(rp,row0,col0,row1,col1,thickness,quads) ellipse
 *		circle_recurse(rp,row0,col0,row1,col1,thickness,theta0,theta1)
 *		bezier_raster(rp,r0,c0,r1,c1,rt,ct)   draw bezier recursively
 *		border_raster(rp,ntop,nbot,isline,isfree)put border around rp
 *		--- raster (and chardef) output functions ---
 *		type_raster(rp,fp)       emit ascii dump of rp on file ptr fp
 *		type_bytemap(bp,grayscale,width,height,fp) dump bytemap on fp
 *		xbitmap_raster(rp,fp)           emit mime xbitmap of rp on fp
 *		type_pbmpgm(rp,ptype,file)     pbm or pgm image of rp to file
 *		cstruct_chardef(cp,fp,col1)         emit C struct of cp on fp
 *		cstruct_raster(rp,fp,col1)          emit C struct of rp on fp
 *		hex_bitmap(rp,fp,col1,isstr)emit hex dump of rp->pixmap on fp
 *		--- ancillary output functions ---
 *		emit_string(fp,col1,string,comment) emit string and C comment
 *		gftobitmap(rp)        convert .gf-like pixmap to bitmap image
 *		====================== Font Functions =======================
 *		--- font lookup functions ---
 *		get_symdef(symbol)             returns mathchardef for symbol
 *		get_chardef(symdef,size)      returns chardef for symdef,size
 *		get_charsubraster(symdef,size)  wrap subraster around chardef
 *		get_symsubraster(symbol,size)    returns subraster for symbol
 *		--- ancillary font functions ---
 *		get_baseline(gfdata)       determine baseline (in our coords)
 *		get_delim(symbol,height,family) delim just larger than height
 *		make_delim(symbol,height) construct delim exactly height size
 *		================= Tokenize/Parse Functions ==================
 *		texchar(expression,chartoken)  retruns next char or \sequence
 *		texsubexpr(expr,subexpr,maxsubsz,left,right,isescape,isdelim)
 *		texleft(expr,subexpr,maxsubsz,ldelim,rdelim)   \left...\right
 *		texscripts(expression,subscript,superscript,which)get scripts
 *		--- ancillary parse functions ---
 *		isbrace(expression,braces,isescape)   check for leading brace
 *		preamble(expression,size,subexpr)              parse preamble
 *		mimeprep(expression) preprocessor converts \left( to \(, etc.
 *		strchange(nfirst,from,to)   change nfirst chars of from to to
 *		strreplace(string,from,to,nreplace)  change from to to in str
 *		strtexchr(string,texchr)                find texchr in string
 *		findbraces(expression,command)    find opening { or closing }
 *	PART3	=========== Rasterize an Expression (recursively) ===========
 *		--- here's the primary entry point for all of mimeTeX ---
 *		rasterize(expression,size)     parse and rasterize expression
 *		--- explicitly called handlers that rasterize... ---
 *		rastparen(subexpr,size,basesp)          parenthesized subexpr
 *		rastlimits(expression,size,basesp)    dispatch super/sub call
 *		rastscripts(expression,size,basesp) super/subscripted exprssn
 *		rastdispmath(expression,size,sp)      scripts for displaymath
 *		--- table-driven handlers that rasterize... ---
 *		rastleft(expression,size,basesp,ildelim,arg2,arg3)\left\right
 *		rastright(expression,size,basesp,ildelim,arg2,arg3) ...\right
 *		rastmiddle(expression,size,basesp,arg1,arg2,arg3)     \middle
 *		rastflags(expression,size,basesp,flag,value,arg3)    set flag
 *		rastspace(expression,size,basesp,width,isfill,isheight)\,\:\;
 *		rastnewline(expression,size,basesp,arg1,arg2,arg3)         \\
 *		rastarrow(expression,size,basesp,width,height,drctn) \longarr
 *		rastuparrow(expression,size,basesp,width,height,drctn)up/down
 *		rastoverlay(expression,size,basesp,overlay,arg2,arg3)    \not
 *		rastfrac(expression,size,basesp,isfrac,arg2,arg3) \frac \atop
 *		rastackrel(expression,size,basesp,base,arg2,arg3)   \stackrel
 *		rastmathfunc(expression,size,basesp,base,arg2,arg3) \lim,\etc
 *		rastsqrt(expression,size,basesp,arg1,arg2,arg3)         \sqrt
 *		rastaccent(expression,size,basesp,accent,isabove,isscript)
 *		rastfont(expression,size,basesp,font,arg2,arg3) \cal{},\scr{}
 *		rastbegin(expression,size,basesp,arg1,arg2,arg3)     \begin{}
 *		rastarray(expression,size,basesp,arg1,arg2,arg3)       \array
 *		rastpicture(expression,size,basesp,arg1,arg2,arg3)   \picture
 *		rastline(expression,size,basesp,arg1,arg2,arg3)         \line
 *		rastcircle(expression,size,basesp,arg1,arg2,arg3)     \circle
 *		rastbezier(expression,size,basesp,arg1,arg2,arg3)     \bezier
 *		rastraise(expression,size,basesp,arg1,arg2,arg3)    \raisebox
 *		rastrotate(expression,size,basesp,arg1,arg2,arg3)  \rotatebox
 *		rastfbox(expression,size,basesp,arg1,arg2,arg3)         \fbox
 *		rastinput(expression,size,basesp,arg1,arg2,arg3)       \input
 *		rastcounter(expression,size,basesp,arg1,arg2,arg3)   \counter
 *		rasttoday(expression,size,basesp,arg1,arg2,arg3)       \today
 *		rastcalendar(expression,size,basesp,arg1,arg2,arg3) \calendar
 *		rastnoop(expression,size,basesp,arg1,arg2,arg3) flush \escape
 *		--- helper functions for handlers ---
 *		rastopenfile(filename,mode)      opens filename[.tex] in mode
 *		rasteditfilename(filename)       edit filename (for security)
 *		rastreadfile(filename,islock,tag,value)   read <tag>...</tag>
 *		rastwritefile(filename,tag,value,isstrict)write<tag>...</tag>
 *		calendar(year,month,day)    formats one-month calendar string
 *		timestamp(tzdelta,ifmt)              formats timestamp string
 *		tzadjust(tzdelta,year,month,day,hour)        adjust date/time
 *		daynumber(year,month,day)     #days since Monday, Jan 1, 1973
 *		dbltoa(d,npts)                double to comma-separated ascii
 *		=== Anti-alias completed raster (lowpass) or symbols (ss) ===
 *		aalowpass(rp,bytemap,grayscale)     lowpass grayscale bytemap
 *		aapnm(rp,bytemap,grayscale)       lowpass based on pnmalias.c
 *		aasupsamp(rp,aa,sf,grayscale)             or by supersampling
 *		aacolormap(bytemap,nbytes,colors,colormap)make colors,colormap
 *		aaweights(width,height)      builds "canonical" weight matrix
 *		aawtpixel(image,ipixel,weights,rotate) weight image at ipixel
 *	PART1	========================== Driver ===========================
 *		main(argc,argv) parses math expression and emits mime xbitmap
 *		CreateGifFromEq(expression,gifFileName)  entry pt for win dll
 *		isstrstr(string,snippets,iscase)  are any snippets in string?
 *		ismonth(month)          is month current month ("jan"-"dec")?
 *		unescape_url(url,isescape), x2c(what)   xlate %xx url-encoded
 *		logger(fp,msglevel,logvars)        logs environment variables
 *		emitcache(cachefile,maxage,isbuffer) emit cachefile to stdout
 *		readcachefile(cachefile,buffer)    read cachefile into buffer
 *		md5str(instr)                      md5 hash library functions
 *		GetPixel(x,y)           callback function for gifsave library
 *
 * Source:	mimetex.c  (needs mimetex.h and texfonts.h to compile,
 *		and also needs gifsave.c if compiled with -DAA or -DGIF)
 *
 * --------------------------------------------------------------------------
 * Notes      o	See bottom of file for main() driver (and "friends"),
 *		and compile as
 *		   cc -DAA mimetex.c gifsave.c -lm -o mimetex.cgi
 *		to produce an executable that emits gif images with
 *		anti-aliasing (see Notes below).  You may also compile
 *		   cc -DGIF mimetex.c gifsave.c -lm -o mimetex.cgi
 *		to produce an executable that emits gif images without
 *		anti-aliasing.  Alternatively, compile mimeTeX as
 *		   cc -DXBITMAP mimetex.c -lm -o mimetex.cgi
 *		to produce an executable that just emits mime xbitmaps.
 *		In either case you'll need mimetex.h and texfonts.h,
 *		and with -DAA or -DGIF you'll also need gifsave.c
 *	      o	For gif images, the gifsave.c library by Sverre H. Huseby
 *		<http://shh.thathost.com> slightly modified by me to allow
 *		(a)sending output to stdout and (b)specifying a transparent
 *		background color index, is included with mimeTeX,
 *		and it's documented in mimetex.html#gifsave .
 *	      o	Optional compile-line -D defined symbols are documented
 *		in mimetex.html#options .  They include...
 *		-DAA
 *		    Turns on gif anti-aliasing with default values
 *		    (CENTERWT=32, ADJACENTWT=3, CORNERWT=1)
 *		    for the following anti-aliasing parameters...
 *		-DCENTERWT=n
 *		-DADJACENTWT=j
 *		-DCORNERWT=k
 *		    MimeTeX currently provides a lowpass filtering
 *		    algorithm for anti-aliasing, which is applied to the
 *		    existing set of bitmap fonts.  This lowpass filter
 *		    applies default weights
 *				1   3   1
 *				3  32   3
 *				1   3   1
 *		    to neighboring pixels. The defaults weights are
 *		    CENTERWT=32, ADJACENTWT=3 and CORNERWT=1,
 *		    which you can adjust to control anti-aliasing.
 *		    Lower CENTERWT values will blur/spread out lines
 *		    while higher values will tend to sharpen lines.
 *		    Experimentation is recommended to determine
 *		    what value works best for you.
 *		-DCACHEPATH=\"path/\"
 *		    This option saves each rendered image to a file
 *		    in directory  path/  which mimeTeX reads rather than
 *		    re-rendering the same image every time it's given
 *		    the same LaTeX expression.  Sometimes mimeTeX disables
 *		    caching, e.g., expressions containing \input{ } are
 *		    re-rendered since the contents of the inputted file
 *		    may have changed.  If compiled without -DCACHEPATH
 *		    mimeTeX always re-renders expressions.  This usually
 *		    isn't too cpu intensive, but if you have unusually
 *		    high hit rates then image caching may be helpful.
 *			The  path/  is relative to mimetex.cgi, and must
 *		    be writable by it.  Files created under  path/  are
 *		    named filename.gif, where filename is the 32-character
 *		    MD5 hash of the LaTeX expression.
 *		-DDISPLAYSIZE=n
 *		    By default, operator limits like \int_a^b are rendered
 *		    \textstyle at font sizes \normalsize and smaller,
 *		    and rendered \displaystyle at font sizes \large and
 *		    larger.  This default corresponds to -DDISPLAYSIZE=3,
 *		    which you can adjust; e.g., -DDISPLAYSIZE=0 always
 *		    defaults to \displaystyle, and 99 (or any large number)
 *		    always defaults to \textstyle.  Note that explicit
 *		    \textstyle, \displaystyle, \limits or \nolimits
 *		    directives in an expression always override
 *		    the DISPLAYSIZE default.
 *		-NORMALSIZE=n
 *		    MimeTeX currently has six font sizes numbered 0-5,
 *		    and always starts in NORMALSIZE whose default value
 *		    is 2.  Specify -DNORMALSIZE=3 on the compile line if
 *		    you prefer mimeTeX to start in default size 3, etc.
 *		-DREFERER=\"domain\"   -or-
 *		-DREFERER=\"domain1,domain2,etc\"
 *		    Blocks mimeTeX requests from unauthorized domains that
 *		    may be using your server's mimetex.cgi without permission.
 *		    If REFERER is defined, mimeTeX checks for the environment
 *		    variable HTTP_REFERER and, if it exists, performs a