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Length: 3681 (0xe61)
Types: TextFile
Names: »dviclass.tex«
└─⟦060c9c824⟧ Bits:30007080 DKUUG TeX 2/12/89
└─⟦this⟧ »./DVIware/laser-setters/umd-dvi/lib/MAN/dviclass.tex«
\manual DVICLASS(3){}
\name
DVI\_DT, DVI\_OpLen---DVI opcode classification tables
\synopsis
DVI\_DT(code)
int code;
DVI\_OpLen(code)
int code;
\endsyn
\description
These macros compress DVI code values according to `classification'
and `opcode length'. \i{DVI\_DT} returns one of the following values:
\beginlist{5em}
\listentry{\lit{DT\_CHAR}}
A literal character code ($0 \le code \le 127$).
\listentry{\lit{DT\_SET}}
A \lit{set} code (set a character and advance).
\listentry{\lit{DT\_SETRULE}}
A \lit{set\_rule} code.
\listentry{\lit{DT\_PUT}}
A \lit{put} code (set a character but do not advance).
\listentry{\lit{DT\_PUTRULE}}
A \lit{put\_rule} code (set a rule but do not advance).
\listentry{\lit{DT\_NOP}}
A \lit{nop} code.
\listentry{\lit{DT\_BOP}}
A \lit{bop} code.
\listentry{\lit{DT\_EOP}}
An \lit{eop} code.
\listentry{\lit{DT\_PUSH}}
A \lit{push}.
\listentry{\lit{DT\_POP}}
A \lit{pop}.
\listentry{\lit{DT\_RIGHT}}
Any of the several \lit{right} codes.
\listentry{\lit{DT\_W0}}
A \lit{w0}.
\listentry{\lit{DT\_W}}
One of the \lit{w}s.
\listentry{\lit{DT\_X0}}
An \lit{x0}.
\listentry{\lit{DT\_X}}
One of the \lit{x}s.
\listentry{\lit{DT\_DOWN}}
A \lit{down}.
\listentry{\lit{DT\_Y0}}
A \lit{y0}.
\listentry{\lit{DT\_Y}}
A \lit{y}.
\listentry{\lit{DT\_Z0}}
A \lit{z0}.
\listentry{\lit{DT\_Z}}
A \lit{z}.
\listentry{\lit{DT\_FNTNUM}}
A parameterless font selector (\lit{fntnum0}, \lit{fntnum1}, \dots,
\lit{fntnum63}).
\listentry{\lit{DT\_FNT}}
A parameterised font selector (\lit{fnt1}, \dots, \lit{fnt4}).
\listentry{\lit{DT\_XXX}}
A \lit{xxx}: a special.
\listentry{\lit{DT\_FNTDEF}}
A \lit{fntdef}.
\listentry{\lit{DT\_PRE}}
A \lit{pre}.
\listentry{\lit{DT\_POST}}
A \lit{post}.
\listentry{\lit{DT\_POSTPOST}}
A \lit{postpost}.
\listentry{\lit{DT\_UNDEF}}
An undefined DVI opcode (in $[250..255]$).
\endlist
\i{DVI\_OpLen} returns the length of the first parameter, as one
of the following values:
\beginlist{5em}
\listentry{\lit{DPL\_NONE}}
No (or implicit) parameter, or it cannot be determined so simply, e.g.,
\lit{bop}, or \lit{post}.
\listentry{\lit{DPL\_SGN1}}
A signed one-byte parameter $-128 \le p \le 127$.
\listentry{\lit{DPL\_SGN2}}
A signed two-byte parameter $-32768 \le p \le 32767$.
\listentry{\lit{DPL\_SGN3}}
A signed three-byte parameter $-8388608 \le p \le 8388607$.
\listentry{\lit{DPL\_SGN4}}
A signed four-byte parameter $-2147483648 \le p \le 2147483647$.
\listentry{\lit{DPL\_UNS1}}
An unsigned one-byte parameter $0 \le p \le 255$.
\listentry{\lit{DPL\_UNS2}}
An unsigned two-byte parameter $0 \le p \le 65535$.
\listentry{\lit{DPL\_UNS3}}
An unsigned three-byte parameter $0 \le p \le 16777215$.
\endlist
These values are intended to be used to simplify \lit{switch} statements
that decode DVI files. A program that must interpret the opcodes can
use code similar to the following:
\vskip 0pt plus1fil
\begincode \vbox{
op = getc(dvi\_file);
switch (DVI\_OpLen(op)) {
case DPL\_NONE: {\it /* do nothing */}
break;
case DPL\_SGN1: {\it /* get a one byte signed parameter */}
param = Sign8(getc(dvi\_file));
break;
case DPL\_SGN2: {\it /* get a two byte signed parameter */}
fGetWord(dvi\_file, param);
param = Sign16(param);
break;
{\rm$\vdots$}
case DPL\_UNS3: {\it /* get a three byte unsigned parameter */}
fGet3Byte(dvi\_file, param);
break;
}
switch (DVI\_DT(op)) {
case DT\_CHAR:
set\_char\_and\_advance(op);
break;
case DT\_SET:
set\_char\_and\_advance(param);
break;
{\rm$\vdots$}
}
} \endcode
In other words, ## other words ##