[RFC/PATCH 13/17] diff.c: convert word diffing to use emit_line_*

[Stefan Beller <sbeller@google.com>]

In a later patch, I want to propose an option to detect&color
moved lines in a diff, which cannot be done in a one-pass over
the diff. Instead we need to go over the whole diff twice,
because we cannot detect the first line of the two corresponding
lines (+ and -) that got moved.

So to prepare the diff machinery for two pass algorithms
(i.e. buffer it all up and then operate on the result),
move all emissions to places, such that the only emitting
function is emit_line_0.

This covers all code related to diffing words.

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 diff.c | 56 ++++++++++++++++++++++++++++----------------------------
 1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/diff.c b/diff.c
index 00a5a4e..3940f79 100644
--- a/diff.c
+++ b/diff.c
@@ -828,37 +828,38 @@ struct diff_words_data {
 	struct diff_words_style *style;
 };
 
-static int fn_out_diff_words_write_helper(FILE *fp,
+static int fn_out_diff_words_write_helper(struct diff_options *o,
 					  struct diff_words_style_elem *st_el,
 					  const char *newline,
 					  size_t count, const char *buf,
 					  const char *line_prefix)
 {
-	int print = 0;
+	struct strbuf sb = STRBUF_INIT;
 
 	while (count) {
 		char *p = memchr(buf, '\n', count);
-		if (print)
-			fputs(line_prefix, fp);
+
 		if (p != buf) {
-			if (st_el->color && fputs(st_el->color, fp) < 0)
-				return -1;
-			if (fputs(st_el->prefix, fp) < 0 ||
-			    fwrite(buf, p ? p - buf : count, 1, fp) != 1 ||
-			    fputs(st_el->suffix, fp) < 0)
-				return -1;
-			if (st_el->color && *st_el->color
-			    && fputs(GIT_COLOR_RESET, fp) < 0)
-				return -1;
+			if (st_el->color)
+				strbuf_addstr(&sb, st_el->color);
+			strbuf_addstr(&sb, st_el->prefix);
+			strbuf_add(&sb, buf, p ? p - buf : count);
+			strbuf_addstr(&sb, st_el->suffix);
+			if (st_el->color && *st_el->color)
+			    strbuf_addstr(&sb, GIT_COLOR_RESET);
 		}
 		if (!p)
-			return 0;
-		if (fputs(newline, fp) < 0)
-			return -1;
+			goto out;
+		strbuf_addstr(&sb, newline);
+		emit_line_0(o, 0, 0, 0, sb.buf, sb.len);
+		strbuf_reset(&sb);
 		count -= p + 1 - buf;
 		buf = p + 1;
-		print = 1;
 	}
+out:
+	if (sb.len)
+		emit_line_0(o, 0, 0, 0, sb.buf, sb.len);
+	strbuf_release(&sb);
 	return 0;
 }
 
@@ -936,25 +937,25 @@ static void fn_out_diff_words_aux(void *priv, char *line, unsigned long len)
 	} else
 		plus_begin = plus_end = diff_words->plus.orig[plus_first].end;
 
-	if (color_words_output_graph_prefix(diff_words)) {
-		fputs(line_prefix, diff_words->opt->file);
-	}
+	if (color_words_output_graph_prefix(diff_words))
+		emit_line_0(diff_words->opt, 0, 0, 0, "", 0);
+
 	if (diff_words->current_plus != plus_begin) {
-		fn_out_diff_words_write_helper(diff_words->opt->file,
+		fn_out_diff_words_write_helper(diff_words->opt,
 				&style->ctx, style->newline,
 				plus_begin - diff_words->current_plus,
 				diff_words->current_plus, line_prefix);
 		if (*(plus_begin - 1) == '\n')
-			fputs(line_prefix, diff_words->opt->file);
+			emit_line_0(diff_words->opt, 0, 0, 0, "", 0);
 	}
 	if (minus_begin != minus_end) {
-		fn_out_diff_words_write_helper(diff_words->opt->file,
+		fn_out_diff_words_write_helper(diff_words->opt,
 				&style->old, style->newline,
 				minus_end - minus_begin, minus_begin,
 				line_prefix);
 	}
 	if (plus_begin != plus_end) {
-		fn_out_diff_words_write_helper(diff_words->opt->file,
+		fn_out_diff_words_write_helper(diff_words->opt,
 				&style->new, style->newline,
 				plus_end - plus_begin, plus_begin,
 				line_prefix);
@@ -1050,8 +1051,7 @@ static void diff_words_show(struct diff_words_data *diff_words)
 
 	/* special case: only removal */
 	if (!diff_words->plus.text.size) {
-		fputs(line_prefix, diff_words->opt->file);
-		fn_out_diff_words_write_helper(diff_words->opt->file,
+		fn_out_diff_words_write_helper(diff_words->opt,
 			&style->old, style->newline,
 			diff_words->minus.text.size,
 			diff_words->minus.text.ptr, line_prefix);
@@ -1077,8 +1077,8 @@ static void diff_words_show(struct diff_words_data *diff_words)
 	if (diff_words->current_plus != diff_words->plus.text.ptr +
 			diff_words->plus.text.size) {
 		if (color_words_output_graph_prefix(diff_words))
-			fputs(line_prefix, diff_words->opt->file);
-		fn_out_diff_words_write_helper(diff_words->opt->file,
+			emit_line_0(diff_words->opt, 0, 0, 0, "", 0);
+		fn_out_diff_words_write_helper(diff_words->opt,
 			&style->ctx, style->newline,
 			diff_words->plus.text.ptr + diff_words->plus.text.size
 			- diff_words->current_plus, diff_words->current_plus,
-- 
2.10.0.21.g1da280f.dirty