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1.1 root 1: % run this through LaTeX with the appropriate wrapper
2:
3: \chapter {Pepsy}\label{pepsy}
4: The \man pepsy(1) program is a table-driven replacement for \pgm{pepy} and
5: \pgm{posy}.
6: At present,
7: all three compilers are available as a part of the standard distribution.
8: In the next major release,
9: \pgm{pepy} and \pgm{posy} will remain,
10: but most likely will not be installed by default.
11:
12: The remainder of this chapter describes how to use \pgm{pepsy}.
13: By virtue of having presented the preceeding two chapters,
14: only a terse discussion is needed!
15:
16: \section {Abstract Syntax Module}
17: As with \pgm{posy},
18: the \pgm{pepsy} program reads a description of an {\em abstract syntax
19: module\/}
20: and produces the corresponding {\em C\/} structures along with several tables
21: that define the mapping between the ASN.1 objects in the module and the
22: {\em C\/} structures.
23: This tables replaces the work done by the \pgm{pepy} program.
24:
25: Note that unlike \pgm{posy},
26: \pgm{pepsy} does not accept annotations in the abstract syntax module.
27: It should be raw ASN.1,
28: either entered by hand,
29: or produced by the \pgm{rosy} program.
30: Note that you must tell \pgm{rosy} when \pgm{pepsy} will be used.
31: This is accomplished with the \switch"pepsy" option,
32: e.g.,
33: \begin{quote}\small\begin{verbatim}
34: .ry.py:; rosy -pepsy $(RYFLAGS) $<
35: \end{verbatim}\end{quote}
36:
37: \section {PEPSY Environment}
38: The \pgm{pepsy} program will produce two files after reading its abstract
39: syntax module.
40:
41: \subsection {C Language Structures}
42: For each type in the abstract syntax module,
43: \pgm{pepy} will define a corresponding {\em C\/} language structure
44: (\verb"struct"),
45: using the same rules as \pgm{posy}
46: (see Section~\ref{posy:c-struct} on page~\pageref{posy:c-struct}).
47:
48: \subsection {Mapping tables}
49: In addition to the definition of {\em C\/} language structures,
50: \pgm{pepsy} will generate a {\em C\/} file containing several tables that
51: define the mapping between the structures and the corresponding ASN.1 objects.
52: As this is entirely an automatic process,
53: the contents of the tables are relatively unimportant.
54:
55: \section {Known Deficiences}
56: \pgm{pepsy} uses essentially the same front-end as the \man posy(1) program,
57: so it has some limitations in the ASN.1 syntax it can accept.
58: Consult Section~\ref{posy:deficiencies} on page~\pageref{posy:deficiencies}
59: for the details.
60:
61: \section {Running PEPSY}
62: Here are a few things to know when running \pgm{pepsy}.
63:
64: \subsection {Options}
65: The \pgm{pepsy} program has a few options to modify its behavior.
66:
67: The \switch"A" switch directs \pgm{pepsy} to produce mapping tables for
68: encoding, decoding, and printing.
69:
70: The \switch"a" switch directs \pgm{pepy} to augment the \verb"#include" file
71: it generates with commentary text.
72:
73: The \switch"d" switch is a no-op with \pgm{pepsy},
74: as it always ignores all \pgm{pepy}-style augmentations,
75: including the
76: ``verbatim'' actions occuring at the very beginning and end of the module.
77:
78: The \switch"f" switch directs \pgm{posy} to generate {\em C\/} macros to
79: deallocate the structures it defines
80: (e.g., for type \verb"type_MODULE_type",
81: a macro called \verb"free_MODULE_type" is defined).
82:
83: As with \pgm{posy},
84: the \switch"h" switch enables additional heuristics when \pgm{pepsy} generates
85: a {\em C\/} language structure definition.
86: See Section~\ref{posy:options} on page~\pageref{posy:options}.
87:
88: Normally, \pgm{posy} prints the name of each type as it works.
89: The \switch"s" switch disables this behavior.
90:
91: \subsection {Makefiles}
92: By convention,
93: input files to \pgm{pepsy} have the extension \verb".py".
94: In order to remain consistent with the naming scheme used by \pgm{posy},
95: rather than starting with file \verb"module.py",
96: we assume we are starting with file \verb"MODULE-asn.py".
97: Let us arbitrarily select the file named \verb"MODULE-types.py" for the
98: augmented abstract syntax module produced by \pgm{posy}.
99: Hence
100: \begin{quote}\begin{verbatim}
101: pepsy MODULE-asn.py
102: \end{verbatim}\end{quote}
103: will produce:
104: \begin{describe}
105: \item[\verb"MODULE-types.h":] the {\em C\/} language structures;
106: and,
107:
108: \item[\verb"MODULE_tables.c":] the mapping tables.
109: \end{describe}
110:
111: Our \man make(1) rules are:
112: \begin{quote}\small\begin{verbatim}
113: MODULE_tables.o: MODULE_tables.c MODULE-types.h
114:
115: MODULE_tables.c MODULE_tables.h: MODULE-asn.py
116: pepsy -A -f -h MODULE-asn.py
117: \end{verbatim}\end{quote}
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