rewrite code

Implemented using getchar instead of getLine, which dramatically
simplified the code and reduced its size.

Author: fsaadatmand

chapter01/1-23.c

@@ -2,192 +2,53 @@
  * Exercise 1-23. Write a program to remove all comments from a C program.
  * Don't forget to handle quoted strings and character constants properly. C
  * comments don't nest.
- * Known issue: when more than full comment is present in a single line, only
- * the last one is removed.
+ *
  * By Faisal Saadatmand
  */
 
-#include <stdio.h>
-
-#define MAXLINE              1000
-#define YES                     1
-#define NO                      0
-#define SLASH_ASTERISK          1
-#define ASTERISK_SLASH          0
-
-/* functions */
-int  getLine(char [], int);
-int  findComment(char [], int );
-int  delComment(char [], char [], int , int);
-int  delBlankLine(char []);
-
-/* getLine function: read a line into s, return length */
-int getLine(char s[], int lim)
-{
-	int c, i;
-
-	for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != '\n'; ++i)
-		s[i] = c;
-
-	if (c == '\n') {
-		s[i] = c;
-		++i;
-	}
-
-	s[i] = '\0';
-
-	return i;
-}
-
-/* findComment function: searches line[] for the first occurrence of the first
- * character of a C comment notation and returns the location on finding a single
- * line comment or -1 on failure */
-int findComment(char line[], int notation)
-{
-	int i, j;
-	int quoteStart;           /* location of the start of the quotation mark */
-	int quoteEnd;             /* location of the end of quotation mark */
-	int location;             /* location of C comment notation */
-	int comment[2];           /* notation type: start or end */
-	int lookForQuote;         /* flag variable */
-
-	location = quoteStart = quoteEnd = -1;
-	/* set the appropriate notation */
-	if (notation == SLASH_ASTERISK) {
-		comment[0] = '/'; 
-		comment[1] = '*';
-	} else if (notation == ASTERISK_SLASH) {
-		comment[0] = '*';
-		comment[1] = '/';
-	}
-
-	lookForQuote  = YES;
-	/* line[x - 1] check handles escape sequences. It is unnecessary for the
-	 * start of the quote but is added for the sake of correctness. */
-	for (i = 0; line[i] != '\0'; ++i) {
-		if (line[i] == comment[0] && line[i + 1] == comment[1]) {
-			if (notation == ASTERISK_SLASH)
-				location = i + 1;      /* end of comment including notation */
-			else
-				location = i;          /* start of comment including notation */
-		}
-		if (line[i] == '\"' && line[i - 1] != '\\' && lookForQuote == YES) {
-			quoteStart = i;
-			for (j = i + 1; line[j] != '\0'; ++j)
-				if (line[j] == '\"' && line[j - 1] != '\\')
-					quoteEnd = j;
-			lookForQuote = NO;
-		}
-	}
-			
-	/* check if notation is inside a double quotation marks */
-	if (location >= 0 && quoteStart >= 0)
-		if (location > quoteStart && location < quoteEnd)
-			location = -1;       /* not a C comment */
-
-	/* check if notation is inside a multi-line double quotation marks */
-	if (location >= 0 && quoteStart >= 0 && quoteEnd < 0)
-//		if (location < quoteStart)
-			location = -1;       /* not a C comment */
-
-	return location;
-}
-
-/* delComment function: deletes C comments from line string stores result in
- * modLine */
-int delComment(char line[], char modLine[], int start, int end)
-{
-	int i, j;
-	int status;
-
-	i = j = 0;
-
-	/* no notation - delete entire line */
-	if (start < 0 && end < 0)
-		for (i = 0; line[i] != '\0'; ++i)
-			modLine[i] = '\0';
-	/* start but no end - delete rest of line */
-	else if (start >= 0 && end < 0)
-		for (i = 0; i < start; ++i)
-			modLine[i] = line[i];
-	/* end but no start - move text after comment to the beginning  of line */
-	else if (start < 0 && end >= 0)
-		for (j = end + 1; line[j] != '\0'; ++j)  {
-			modLine[i] = line[j];
-			++i;
-		}
-	/* full comment embedded - move text after comment to start location */
-	else if (start >= 0 && end >= 0) {
-		for (i = 0; i < start; ++i)
-			modLine[i] = line[i];
-		for (j = end + 1; line[j] != '\0'; ++j) {
-			modLine[i] = line[j];
-			++i;
-		}
-	}
+/* 
+ * NOTE: In keeping with the C standard the book follows, this program does not
+ * delete single-line comments, i.e. lines beginning with //, because their
+ * addition into the language came after ANSI C (C89).
+ */
 
-	/* end of line formatting */
-	if (start < 0 && end < 0)
-		modLine[0] = '\n';
-	else if (start >= 0 && end < 0) {
-		modLine[i] = '\n';
-		modLine[i + 1] = '\0';
-	} else 
-		modLine[i] = '\0';
+#include <stdio.h>
 
-	/* status of the current deleted comment: single or multi-line */
-	status = 0;
-	if ((start >= 0 && end < 0) || (start < 0 && end < 0))
-		status = 1;
-	else if (start < 0 && end >= 0)
-		status = 0;
+#define IN 1
+#define OUT 0
 
-	return status;
-}
-
-/* delBlanklin function: deletes a line if it's blank. Returns 1 on success
- * and 0 on failure */
-int delBlankLine(char s[])
+/* isQuotationMark: return true if c is a valid beginning (or end) of a string
+ * literal, otherwise return 0 */
+int isQuotationMark(char prev, char c)
 {
-	int i, notBlankLine;
-
-	i = notBlankLine = 0;
-	while (notBlankLine != 1 && s[i] != '\0') {
-		if (s[i] != ' ' && s[i] != '\t' && s[i] != '\n')
-			notBlankLine = 1;
-		++i;
-	}
-
-	if (notBlankLine != 1)
-		for (i = 0; s[i] != '\0'; ++i)
-			s[i] = '\0';
-
-	return notBlankLine;
+	return prev != '\\' && prev != '\'' && c == '\"';
 }
 
 int main(void)
 {
-	int  len;                              /* current line length */
-	int  start;                            /* comment's beginning */
-	int  end;                              /* comment's end */
-	char line[MAXLINE];                    /* current input line */
-	char modLine[MAXLINE];                 /* modified output line */
-	int  status;                           /* multi-line comments flag */
-
-	status = 0;
-
-	while ((len = getLine(line, MAXLINE)) > 0) {
-
-		start = findComment(line, SLASH_ASTERISK);
-		end   = findComment(line, ASTERISK_SLASH);
-
-		if (start < 0 && end < 0 && status == 0)    /* no comment found */
-			printf("%s", line);
-		else {
-			status = delComment(line, modLine, start, end);
-			delBlankLine(modLine);                  /* optional */
-			printf("%s", modLine);
+	int prevC; /* previously read character from input */
+	int c; /* currently read character from input */
+	int comment, quote; /* flag variables */
+
+	comment = quote = OUT;
+	prevC = getchar(); /* get the first character */
+	while ((c = getchar()) != EOF) { /* get the next character */
+		if (isQuotationMark(prevC, c)) {
+			if (quote == IN)
+				quote = OUT; /* the end of quote */
+			else if (comment == OUT)
+				quote = IN; /* the beginning of a quote */
+		}
+		if (quote == OUT && prevC == '/' && c == '*')
+			comment = IN; /* the beginning of a comment */
+		if (comment == OUT)
+			putchar(prevC); /* print previously read character */
+		if (comment == IN && prevC == '*' && c == '/') {
+			c = getchar(); /* skip '/' character */
+			comment = OUT; /* the end of a comment */
 		}
+		prevC = c; /* store c */
 	}
+	putchar(prevC); /* print the last previously read character */
 	return 0;
 }