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/*
\funcref{lexer}{LEXER\_ lexer ()}
{}
{read token from the input}
{error(), directive(), getident()}
{}
{lexer.c}
{
Function {\em lexer()} processes the input file and depending on the
information returns a value from the {\em LEXER\_} enumerated type. The
semantic value of the input is stored in the lexical buffer {\em
lexbuf}.
The following types of input are handled within {\em lexer()}, i.e.,
without returning:
\begin{itemize}
\item Newlines lead to the updating of the line counter associated
with the current file.
\item Comments (// or /$*$ $*$/) are skipped.
\item `\#' characters activate function {\em directive()}, which
processes a preprocessor directive. After the processing of the
directive, the input is further processed.
\end{itemize}
The following types of input lead to termination of {\em lexer()} by
returning:
\begin{itemize}
\item End of file: value {\em l\_eof} is returned.
\item Spaces or tabs: value {\em l\_space} is returned, while the
read character is stored in {\em lexbuf[0]}.
\item Double quotes: {\em l\_string} is returned, while the string
is stored in {\em lexbuf}. Note that the double quotes are not
stored in {\em lexbuf}.
\item Identifiers (see {\em getident()} for a definition): {\em
l\_ident} is returned, while the identifier name is stored in {\em
lexbuf}. The identifier is read into the buffer by {\em
getident()}.
\item Numbers (series of [0-9]): {\em l\_other} is returned, while
the read `pseudo-identifier' is stored in {\em lexbuf}.
\item All other characters: {\em l\_single} is returned, while the
character is stored in {\em lexbuf[0]}.
\end{itemize}
}
*/
#include "icm-pp.h"
LEXER_ lexer ()
{
register int
state,
index,
ch;
while (1)
{
ch = fgetc (filestack [filesp].f);
switch (ch)
{
case EOF:
at_firstcol = 1;
return (l_eof);
case '\n':
at_firstcol = 1;
filestack [filesp].l++;
lexbuf [0] = '\n';
return (l_space);
case ' ':
case '\t':
at_firstcol = 0;
lexbuf [0] = ch;
return (l_space);
case '\"':
at_firstcol = 0;
if (nostrings)
{
lexbuf [0] = (char) ch;
return (l_single);
}
index = 0;
while (1)
{
if ( (ch = fgetc (filestack [filesp].f)) == '\n' )
error ("%s: %d: unterminated string, \" expected",
filestack [filesp].n, filestack [filesp].l);
else if (ch == '\\')
{
lexbuf [index++] = '\\';
if ( (lexbuf [index++] =
fgetc (filestack [filesp].f)) == (char) EOF
)
error ("%s: unterminated string at EOF",
filestack [filesp].n);
}
else if (ch == '\"')
{
lexbuf [index] = '\0';
return (l_string);
}
else
lexbuf [index++] = (char) ch;
}
case '/':
at_firstcol = 0;
lexbuf [0] = '/';
if (nocomment)
return (l_single);
if ( (ch = fgetc (filestack [filesp].f)) == '/' )
{
while ( (ch = fgetc (filestack [filesp].f)) != '\n' &&
ch != EOF
)
;
ungetc (ch, filestack [filesp].f);
break;
}
else if (ch == '*')
{
state = 0;
while (state != 2)
{
if ( (ch = fgetc (filestack [filesp].f)) == '\n')
{
filestack [filesp].l++;
fputc ('\n', outfile);
}
else if (ch == EOF)
error ("%s: %d: unterminated comment block",
filestack [filesp].n, filestack [filesp].l);
switch (state)
{
case 0:
if (ch == '*')
state = 1;
break;
case 1:
if (ch == '/')
state = 2;
else
state = 0;
break;
}
}
}
else
{
ungetc (ch, filestack [filesp].f);
return (l_single);
}
break;
case '#':
if (at_firstcol || !strict_directives)
{
at_firstcol = 0;
directive ();
at_firstcol = 1;
}
else
{
lexbuf [0] = '#';
return (l_single);
}
break;
default:
at_firstcol = 0;
if (ch == '_' || isalpha (ch))
{
ungetc (ch, filestack [filesp].f);
getident (lexbuf);
return (l_ident);
}
else if (isalnum (ch))
{
index = 0;
while (isalnum (ch) || ch == '_')
{
lexbuf [index++] = (char) ch;
ch = fgetc (filestack [filesp].f);
}
lexbuf [index] = '\0';
ungetc (ch, filestack [filesp].f);
return (l_other);
}
else
{
lexbuf [0] = (char) ch;
return (l_single);
}
}
}
}
|
