[PATCH v3 1/4] word diff: comments, preparations for regex customization

From

Thomas Rast <trast@student.ethz.ch>

Date

Jan 11, 2009, 10:27 UTC

Message-ID

<4aea85caafd38a058145c5769fe8a30ffdbd4d13.1231669012.git.trast@student.ethz.ch>

In-Reply-To

<cover.1231669012.git.trast@student.ethz.ch>

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
---
 diff.c |   86 +++++++++++++++++++++++++++++++++++++++++++++++++++------------
 1 files changed, 69 insertions(+), 17 deletions(-)

diff --git a/diff.c b/diff.c
index d235482..f274bf5 100644
--- a/diff.c
+++ b/diff.c
@@ -316,11 +316,21 @@ static int fill_mmfile(mmfile_t *mf, struct diff_filespec *one)
 	return 0;
 }
 
+/* unused right now */
+enum diff_word_boundaries {
+	DIFF_WORD_UNDEF,
+	DIFF_WORD_BODY,
+	DIFF_WORD_END,
+	DIFF_WORD_SPACE,
+	DIFF_WORD_SKIP
+};
+
 struct diff_words_buffer {
 	mmfile_t text;
 	long alloc;
 	long current; /* output pointer */
 	int suppressed_newline;
+	enum diff_word_boundaries *boundaries;
 };
 
 static void diff_words_append(char *line, unsigned long len,
@@ -339,16 +349,23 @@ static void diff_words_append(char *line, unsigned long len,
 struct diff_words_data {
 	struct diff_words_buffer minus, plus;
 	FILE *file;
+	regex_t *word_regex; /* currently unused */
 };
 
-static void print_word(FILE *file, struct diff_words_buffer *buffer, int len, int color,
+/*
+ * Print 'len' characters from the "real" diff data in 'buffer'.  Also
+ * returns how many characters were printed (currently always 'len').
+ * With 'suppress_newline', we remember a final newline instead of
+ * printing it.
+ */
+static int print_word(FILE *file, struct diff_words_buffer *buffer, int len, int color,
 		int suppress_newline)
 {
 	const char *ptr;
 	int eol = 0;
 
 	if (len == 0)
-		return;
+		return len;
 
 	ptr  = buffer->text.ptr + buffer->current;
 	buffer->current += len;
@@ -368,18 +385,30 @@ static void print_word(FILE *file, struct diff_words_buffer *buffer, int len, in
 		else
 			putc('\n', file);
 	}
+
+	/* we need to return how many chars to skip on the other side,
+	 * so account for the (held off) \n */
+	return len+eol;
 }
 
+/*
+ * Callback for word diff output
+ */
 static void fn_out_diff_words_aux(void *priv, char *line, unsigned long len)
 {
 	struct diff_words_data *diff_words = priv;
 
 	if (diff_words->minus.suppressed_newline) {
+		/* We completely drop a suppressed newline on the
+		 * minus side, if it is immediately followed by a plus
+		 * side output. This formats a word change right
+		 * before the end of line correctly */
 		if (line[0] != '+')
 			putc('\n', diff_words->file);
 		diff_words->minus.suppressed_newline = 0;
 	}
 
+	/* account for the [+- ] inserted by the line diff */
 	len--;
 	switch (line[0]) {
 		case '-':
@@ -391,8 +420,10 @@ static void fn_out_diff_words_aux(void *priv, char *line, unsigned long len)
 				   &diff_words->plus, len, DIFF_FILE_NEW, 0);
 			break;
 		case ' ':
-			print_word(diff_words->file,
-				   &diff_words->plus, len, DIFF_PLAIN, 0);
+			len = print_word(diff_words->file,
+					 &diff_words->plus, len, DIFF_PLAIN, 0);
+			/* skip the characters that were printed on
+			 * the other side, too */
 			diff_words->minus.current += len;
 			break;
 	}
@@ -409,22 +440,37 @@ static void diff_words_show(struct diff_words_data *diff_words)
 
 	memset(&xpp, 0, sizeof(xpp));
 	memset(&xecfg, 0, sizeof(xecfg));
-	minus.size = diff_words->minus.text.size;
-	minus.ptr = xmalloc(minus.size);
-	memcpy(minus.ptr, diff_words->minus.text.ptr, minus.size);
-	for (i = 0; i < minus.size; i++)
-		if (isspace(minus.ptr[i]))
-			minus.ptr[i] = '\n';
-	diff_words->minus.current = 0;
 
-	plus.size = diff_words->plus.text.size;
-	plus.ptr = xmalloc(plus.size);
-	memcpy(plus.ptr, diff_words->plus.text.ptr, plus.size);
-	for (i = 0; i < plus.size; i++)
-		if (isspace(plus.ptr[i]))
-			plus.ptr[i] = '\n';
+	/* currently always true */
+	if (!diff_words->word_regex) {
+		/*
+		 * "Simple" word diff: replace all space characters
+		 * with a newline.
+		 *
+		 * This groups together "words" of nonspaces on a line
+		 * each, which we then diff using the normal line-diff
+		 * mechanism.  It also has the nice property that
+		 * character counts/offsets stay the same.
+		 */
+		minus.size = diff_words->minus.text.size;
+		minus.ptr = xmalloc(minus.size);
+		memcpy(minus.ptr, diff_words->minus.text.ptr, minus.size);
+		for (i = 0; i < minus.size; i++)
+			if (isspace(minus.ptr[i]))
+				minus.ptr[i] = '\n';
+
+		plus.size = diff_words->plus.text.size;
+		plus.ptr = xmalloc(plus.size);
+		memcpy(plus.ptr, diff_words->plus.text.ptr, plus.size);
+		for (i = 0; i < plus.size; i++)
+			if (isspace(plus.ptr[i]))
+				plus.ptr[i] = '\n';
+	}
+	diff_words->minus.current = 0;
 	diff_words->plus.current = 0;
 
+	/* we want a minimal diff with enough context to run
+	 * everything into a single hunk */
 	xpp.flags = XDF_NEED_MINIMAL;
 	xecfg.ctxlen = diff_words->minus.alloc + diff_words->plus.alloc;
 	xdi_diff_outf(&minus, &plus, fn_out_diff_words_aux, diff_words,
@@ -432,7 +478,12 @@ static void diff_words_show(struct diff_words_data *diff_words)
 	free(minus.ptr);
 	free(plus.ptr);
 	diff_words->minus.text.size = diff_words->plus.text.size = 0;
+	/* these two are currently free(NULL) */
+	free(diff_words->minus.boundaries);
+	free(diff_words->plus.boundaries);
 
+	/* do not forget about a possible final newline that was held
+	 * back */
 	if (diff_words->minus.suppressed_newline) {
 		putc('\n', diff_words->file);
 		diff_words->minus.suppressed_newline = 0;
@@ -461,6 +512,7 @@ static void free_diff_words_data(struct emit_callback *ecbdata)
 
 		free (ecbdata->diff_words->minus.text.ptr);
 		free (ecbdata->diff_words->plus.text.ptr);
+		free(ecbdata->diff_words->word_regex);
 		free(ecbdata->diff_words);
 		ecbdata->diff_words = NULL;
 	}

-- 
1.6.1.269.g0769