From 9ba1bb3d2007b37e3392208ef027f88d78e51c3e Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Fri, 13 Aug 2021 11:36:31 +0200
Subject: cc: some work on the scanner, expression parser

---
 miniany/cc.c | 280 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 266 insertions(+), 14 deletions(-)

(limited to 'miniany/cc.c')

diff --git a/miniany/cc.c b/miniany/cc.c
index 1637627..ebdebdb 100644
--- a/miniany/cc.c
+++ b/miniany/cc.c
@@ -1,45 +1,297 @@
 int col;
 int row;
 
+int pushback;
+
+int token;
+
+int DEBUG_SCANNER;
+
+enum {
+	MAX_IDENT_LEN = 20,
+	TEST = -1
+};
+
+void pushBack( int c )
+{
+	pushback = c;
+}
+
 int getChar( )
 {	
 	int c;
 	
+	if( pushback ) {
+		c = pushback;
+		pushback = 0;
+		return c;
+	}
+	
 	c = getchar( );
 	if( c == EOF ) {
 		return c;
 	}
 	col++;
 	if( c == '\n' ) {
-		col = 1;
+		col = 0;
 		row++;
 	}
 	return c;
 }
 
-int main( int argc, char **argv )
+int skipWhite( )
 {
 	int c;
 	
-	col = 1;
-	row = 1;
+	c = getChar( );
+	while( isspace( c ) ) {
+		c = getChar( );
+	}
+	
+	return c;
+}
 
-	putstring( "Hello CC" );
-	putnl( );
+enum {
+	S_PLUS = 1,
+	S_MINUS,
+	S_STAR,
+	S_SLASH,
+	S_SEMICOLON,
+	S_EQUALS,
+	S_INT = 10,
+	S_IDENT,
+	S_NUM = 20,
+	S_ERR = 30,
+	S_EOI = 31
+};
 
-	c = getChar( );
+void printErrorHeader( )
+{
+	putstring( "Error line " );
 	putint( row );
+	putstring( ", pos " );
+	putint( col );
 	putstring( ": " );
-	while( c != EOF ) {
-		if( c == '\n' ) {
-			putchar( '$' );
-			putchar( c );
-			putint( row );
-			putstring( ": " );
+}
+
+int num;
+
+void scanNumber( int c )
+{
+	num = c - '0';
+	c = getChar( );
+	while( isdigit( c ) ) {
+		num = 10 * num + ( c - '0' );
+		c = getChar( );
+	}
+	pushBack( c );
+}
+
+/* c4: no data segment allocation in char array decleration */
+char *ident;
+/*char ident[20];
+  char ident[MAX_IDENT_LEN];
+*/
+
+void scanIdent( int c )
+{
+	int n;
+	
+	n = 0;
+	while( isalnum( c ) || ( c == '_' ) ) {
+		ident[n] = c;
+		n++;
+		if( n >= MAX_IDENT_LEN - 1 ) {
+			printErrorHeader( );
+			putstring( "too long identifier" );
+			putnl( );
+			exit( EXIT_FAILURE );
+		}
+		c = getChar( );
+	}
+	ident[n] = 0; /* c4 doesn't handle '\0' */
+	pushBack( c );
+}
+
+int keyword( char *ident )
+{
+	if( *ident == 'i' ) {
+		if( strcmp( ident, "int" ) == 0 ) {
+			return S_INT;
 		} else {
-			putchar( c );
+			return 0;
 		}
+	}
+	
+	return 0;
+}
+
+int getToken( )
+{
+	int t;
+	int c;
+	
+	c = skipWhite( );
+	
+	if( c == EOF ) {
+		t = S_EOI;
+	} else if( c == '+' ) {
+		t = S_PLUS;
+	} else if( c == '-' ) {
+		t = S_MINUS;
+	} else if( c == '*' ) {
+		t = S_STAR;
+	} else if ( c == '/' ) {
 		c = getChar( );
+		if( c == '/' ) {
+			while( c != '\n' ) {
+				c = getChar( );
+			}
+			t = getToken( );
+		} else if( c == '*' ) {
+			do {
+				while( c != '*' ) {
+					c = getChar( );
+				}
+				c = getChar( );
+			} while( c != '/' );
+			c = getChar( );
+			t = getToken( );
+		} else {
+			pushBack( c );
+			t = S_SLASH;
+		}
+	} else if( c == ';' ) {
+		t = S_SEMICOLON;
+	} else if( c == '=' ) {
+		t = S_EQUALS;
+	} else if( isdigit( c ) ) {
+		scanNumber( c );
+		t = S_NUM;
+	} else if( c >= 'a' && c <= 'z' ) {
+		scanIdent( c );
+		if( ( t = keyword( ident ) ) ) {
+		} else {
+			t = S_IDENT;
+		}
+	} else {
+		t = S_ERR;
+		printErrorHeader( );
+		putstring( "unknown token '" );
+		putchar( c );
+		putstring( "'" );
+		putnl( );
+		exit( EXIT_FAILURE );
+	}
+
+	if( DEBUG_SCANNER ) {
+		putint( row );
+		putchar( '/' );
+		putint( col );
+		putstring( ": " );
+		putint( t );
+		if( t == S_NUM ) {
+			putchar( '(' );
+			putint( num );
+			putchar( ')' );
+		}
+		putnl( );
+	}
+		
+	return t;
+}
+
+void expect( int must, char *what )
+{
+	if( token == must ) {
+		token = getToken( );
+	} else {
+		printErrorHeader( );
+		putstring( what );
+		putstring( " expected" );
+		putnl( );
+		exit( EXIT_FAILURE );
+	}
+}
+
+void parseExpression( )
+{
+	if( token == S_EOI ) {
+		printErrorHeader( );
+		putstring( "unexpected eof in expression" );
+		putnl( );
+		exit( EXIT_FAILURE );
+	}
+	
+	if( token == S_NUM ) {
+		putstring( "immediate int " );
+		putint( num );
+		putnl( );
+	}
+	
+	token = getToken( );
+	if( token == S_PLUS ) {
+		token = getToken( );
+		parseExpression( );
+	} else if( token == S_MINUS ) {
+		token = getToken( );
+		parseExpression( );
+	} else if( token == S_STAR ) {
+		token = getToken( );
+		parseExpression( );
+	} else if( token == S_SLASH ) {
+		token = getToken( );
+		parseExpression( );
+	} else if( token == S_EOI || token == S_SEMICOLON ) {
+		return;
+	} else {
+		printErrorHeader( );
+		putstring( "unexpected token '" );
+		putint( token );
+		putstring( "' in expression" );
+		putnl( );
+		exit( EXIT_FAILURE );
+	}
+}
+
+void parseDeclaration( )
+{
+	expect( S_INT, "int" );	
+	expect( S_IDENT, "identifier" );
+	putstring( "Adding glob: " ); putstring( ident ); putnl( );
+	expect( S_SEMICOLON, ";" );
+}
+
+void parseAssignment( )
+{
+	token = getToken( );
+	expect( S_EQUALS, "=" );
+	parseExpression( );
+	expect( S_SEMICOLON, ";" );
+}
+
+void parseStatement( )
+{
+	if( token == S_INT ) {
+		parseDeclaration( );
+	} else if( token == S_IDENT ) {
+		parseAssignment( );
+	} else if( token == S_EOI ) {
+		return;
+	}
+}
+
+int main( int argc, char **argv )
+{	
+	col = 0;
+	row = 1;
+	pushback = 0;
+	DEBUG_SCANNER = 1;
+	ident = "12345678901234567890";
+
+	token = getToken( );
+	while( token != S_EOI ) {
+		parseStatement( );
 	}
 
 	exit( EXIT_SUCCESS );
-- 
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