fmt: improved version using less memory

functional identical, but uses different data structure.
instead of reading all words into memory, we read and
tokenize on demand keeping a simple linked list of words
to conume by further calls of getword(). once the list
is empty we read the next line, tokenize it and fill the
list up again. so we only need as mutch memory to hold
all the words of the longest line.

1 files changed, 79 insertions, 80 deletions

diff --git a/sys/src/cmd/fmt.c b/sys/src/cmd/fmt.c
index a072c8ba2..eec29283d 100644
--- a/sys/src/cmd/fmt.c
+++ b/sys/src/cmd/fmt.c
@@ -12,14 +12,19 @@ int indent = 0;			/* current value of indent, before extra indent */
 int length = 70;		/* how many columns per output line */
 int join = 1;			/* can lines be joined? */
 int maxtab = 8;
+
 Biobuf bin;
 Biobuf bout;
 
 typedef struct Word Word;
-struct Word{
-	int	bol;
+struct Word
+{
+	Word	*next;
+
 	int	indent;
-	char	text[1];
+	int	length;
+	char	bol;
+	char	text[];
 };
 
 void	fmt(void);
@@ -84,17 +89,14 @@ main(int argc, char **argv)
 }
 
 int
-indentof(char **linep)
+indentof(char *s)
 {
-	int i, ind;
-	char *line;
+	int ind;
 
 	ind = 0;
-	line = *linep;
-	for(i=0; line[i]; i++)
-		switch(line[i]){
+	for(; *s != '\0'; s++)
+		switch(*s){
 		default:
-			*linep = line;
 			return ind;
 		case ' ':
 			ind++;
@@ -104,53 +106,65 @@ indentof(char **linep)
 			ind -= ind%maxtab;
 			break;
 		}
-			
+
 	/* plain white space doesn't change the indent */
-	*linep = "";
 	return indent;
 }
 
-Word**
-addword(Word **words, int *nwordp, char *s, int l, int indent, int bol)
+Word*
+newword(char *s, int n, int ind, int bol)
 {
 	Word *w;
 
-	w = malloc(sizeof(Word)+l+1);
-	memmove(w->text, s, l);
-	w->text[l] = '\0';
-	w->indent = indent;
+	w = malloc(sizeof(Word) + n+1);
+	w->next = nil;
+	w->indent = ind;
 	w->bol = bol;
-	words = realloc(words, (*nwordp+1)*sizeof(Word*));
-	words[(*nwordp)++] = w;
-	return words;
+	memmove(w->text, s, n);
+	w->text[n] = 0;
+	w->length = utflen(w->text);
+	return w;
 }
 
-Word**
-parseline(char *line, Word **words, int *nwordp)
+Word*
+getword(void)
 {
-	int ind, l, bol;
-
-	ind = indentof(&line);
-	indent = ind;
-	bol = 1;
+	static Word *head, *tail;
+	char *line, *s;
+	Word *w;
+	
+	w = head;
+	if(w != nil){
+		head = w->next;
+		return w;
+	}
+	line = Brdstr(&bin, '\n', 1);
+	if(line == nil)
+		return nil;
+	tail = nil;
+	indent = indentof(line);
 	for(;;){
-		/* find next word */
-		while(*line==' ' || *line=='\t')
+		while(*line == ' ' || *line == '\t')
 			line++;
 		if(*line == '\0'){
-			if(bol)
-				return addword(words, nwordp, "", 0, -1, bol);
+			if(head == nil)
+				return newword("", 0, -1, 1);
 			break;
 		}
 		/* how long is this word? */
-		for(l=0; line[l]; l++)
-			if(line[l]==' ' || line[l]=='\t')
+		for(s=line++; *line != '\0'; line++)
+			if(*line==' ' || *line=='\t')
 				break;
-		words = addword(words, nwordp, line, l, indent, bol);
-		bol = 0;
-		line += l;
+		w = newword(s, line-s, indent, head==nil);
+		if(head == nil)
+			head = w;
+		else
+			tail->next = w;
+		tail = w;
 	}
-	return words;
+	w = head;
+	head = w->next;
+	return w;
 }
 
 void
@@ -181,61 +195,46 @@ nspaceafter(char *s)
 		return 2;
 	return 1;
 }
-	
 
 void
-printwords(Word **w, int nw)
+fmt(void)
 {
-	int i, j, n, col, nsp;
+	Word *w, *o;
+	int col, nsp;
 
-	/* one output line per loop */
-	for(i=0; i<nw; ){
-		/* if it's a blank line, print it */
-		if(w[i]->indent == -1){
+	w = getword();
+	while(w != nil){
+		if(w->indent == -1){
 			Bputc(&bout, '\n');
-			if(++i == nw)	/* out of words */
+			free(w);
+			w = getword();
+			if(w == nil)
 				break;
 		}
-		/* emit leading indent */
-		col = extraindent+w[i]->indent;
-		printindent(col);
+		col = w->indent;
+		printindent(extraindent+col);
 		/* emit words until overflow; always emit at least one word */
-		for(n=0;; n++){
-			Bprint(&bout, "%s", w[i]->text);
-			col += utflen(w[i]->text);
-			if(++i == nw)
-				break;	/* out of words */
-			if(w[i]->indent != w[i-1]->indent)
+		for(;;){
+			Bprint(&bout, "%s", w->text);
+			col += w->length;
+			o = w;
+			w = getword();
+			if(w == nil)
+				break;
+			if(w->indent != o->indent)
 				break;	/* indent change */
-			nsp = nspaceafter(w[i-1]->text);
-			if(col+nsp+utflen(w[i]->text) > extraindent+length)
+			nsp = nspaceafter(o->text);
+			if(col+nsp+w->length > length)
 				break;	/* fold line */
-			if(!join && w[i]->bol)
+			if(!join && w->bol)
 				break;
-			for(j=0; j<nsp; j++)
+			while(--nsp >= 0){
 				Bputc(&bout, ' ');	/* emit space; another word will follow */
-			col += nsp;
+				col++;
+			}
+			free(o);
 		}
-		/* emit newline */
+		free(o);
 		Bputc(&bout, '\n');
 	}
 }
-
-void
-fmt(void)
-{
-	char *s;
-	int i, nw;
-	Word **w;
-
-	nw = 0;
-	w = nil;
-	while((s = Brdstr(&bin, '\n', 1)) != nil){
-		w = parseline(s, w, &nw);
-		free(s);
-	}
-	printwords(w, nw);
-	for(i=0; i<nw; i++)
-		free(w[i]);
-	free(w);
-}