1 files changed, 77 insertions, 34 deletions

diff --git a/xdiff/xemit.c b/xdiff/xemit.c
index c4bedf0d1c..d11dbf9f13 100644
--- a/xdiff/xemit.c
+++ b/xdiff/xemit.c
@@ -85,30 +85,9 @@ static long def_ff(const char *rec, long len, char *buf, long sz, void *priv)
 	return -1;
 }
 
-static void xdl_find_func(xdfile_t *xf, long i, char *buf, long sz, long *ll,
-		find_func_t ff, void *ff_priv) {
-
-	/*
-	 * Be quite stupid about this for now.  Find a line in the old file
-	 * before the start of the hunk (and context) which starts with a
-	 * plausible character.
-	 */
-
-	const char *rec;
-	long len;
-
-	while (i-- > 0) {
-		len = xdl_get_rec(xf, i, &rec);
-		if ((*ll = ff(rec, len, buf, sz, ff_priv)) >= 0)
-			return;
-	}
-	*ll = 0;
-}
-
-
 static int xdl_emit_common(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
                            xdemitconf_t const *xecfg) {
-	xdfile_t *xdf = &xe->xdf1;
+	xdfile_t *xdf = &xe->xdf2;
 	const char *rchg = xdf->rchg;
 	long ix;
 
@@ -121,13 +100,40 @@ static int xdl_emit_common(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 	return 0;
 }
 
+struct func_line {
+	long len;
+	char buf[80];
+};
+
+static long get_func_line(xdfenv_t *xe, xdemitconf_t const *xecfg,
+			  struct func_line *func_line, long start, long limit)
+{
+	find_func_t ff = xecfg->find_func ? xecfg->find_func : def_ff;
+	long l, size, step = (start > limit) ? -1 : 1;
+	char *buf, dummy[1];
+
+	buf = func_line ? func_line->buf : dummy;
+	size = func_line ? sizeof(func_line->buf) : sizeof(dummy);
+
+	for (l = start; l != limit && 0 <= l && l < xe->xdf1.nrec; l += step) {
+		const char *rec;
+		long reclen = xdl_get_rec(&xe->xdf1, l, &rec);
+		long len = ff(rec, reclen, buf, size, xecfg->find_func_priv);
+		if (len >= 0) {
+			if (func_line)
+				func_line->len = len;
+			return l;
+		}
+	}
+	return -1;
+}
+
 int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		  xdemitconf_t const *xecfg) {
 	long s1, s2, e1, e2, lctx;
 	xdchange_t *xch, *xche;
-	char funcbuf[80];
-	long funclen = 0;
-	find_func_t ff = xecfg->find_func ?  xecfg->find_func : def_ff;
+	long funclineprev = -1;
+	struct func_line func_line = { 0 };
 
 	if (xecfg->flags & XDL_EMIT_COMMON)
 		return xdl_emit_common(xe, xscr, ecb, xecfg);
@@ -138,6 +144,17 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		s1 = XDL_MAX(xch->i1 - xecfg->ctxlen, 0);
 		s2 = XDL_MAX(xch->i2 - xecfg->ctxlen, 0);
 
+		if (xecfg->flags & XDL_EMIT_FUNCCONTEXT) {
+			long fs1 = get_func_line(xe, xecfg, NULL, xch->i1, -1);
+			if (fs1 < 0)
+				fs1 = 0;
+			if (fs1 < s1) {
+				s2 -= s1 - fs1;
+				s1 = fs1;
+			}
+		}
+
+ again:
 		lctx = xecfg->ctxlen;
 		lctx = XDL_MIN(lctx, xe->xdf1.nrec - (xche->i1 + xche->chg1));
 		lctx = XDL_MIN(lctx, xe->xdf2.nrec - (xche->i2 + xche->chg2));
@@ -145,24 +162,50 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		e1 = xche->i1 + xche->chg1 + lctx;
 		e2 = xche->i2 + xche->chg2 + lctx;
 
+		if (xecfg->flags & XDL_EMIT_FUNCCONTEXT) {
+			long fe1 = get_func_line(xe, xecfg, NULL,
+						 xche->i1 + xche->chg1,
+						 xe->xdf1.nrec);
+			if (fe1 < 0)
+				fe1 = xe->xdf1.nrec;
+			if (fe1 > e1) {
+				e2 += fe1 - e1;
+				e1 = fe1;
+			}
+
+			/*
+			 * Overlap with next change?  Then include it
+			 * in the current hunk and start over to find
+			 * its new end.
+			 */
+			if (xche->next) {
+				long l = xche->next->i1;
+				if (l <= e1 ||
+				    get_func_line(xe, xecfg, NULL, l, e1) < 0) {
+					xche = xche->next;
+					goto again;
+				}
+			}
+		}
+
 		/*
 		 * Emit current hunk header.
 		 */
 
 		if (xecfg->flags & XDL_EMIT_FUNCNAMES) {
-			xdl_find_func(&xe->xdf1, s1, funcbuf,
-				      sizeof(funcbuf), &funclen,
-				      ff, xecfg->find_func_priv);
+			get_func_line(xe, xecfg, &func_line,
+				      s1 - 1, funclineprev);
+			funclineprev = s1 - 1;
 		}
 		if (xdl_emit_hunk_hdr(s1 + 1, e1 - s1, s2 + 1, e2 - s2,
-				      funcbuf, funclen, ecb) < 0)
+				      func_line.buf, func_line.len, ecb) < 0)
 			return -1;
 
 		/*
 		 * Emit pre-context.
 		 */
-		for (; s1 < xch->i1; s1++)
-			if (xdl_emit_record(&xe->xdf1, s1, " ", ecb) < 0)
+		for (; s2 < xch->i2; s2++)
+			if (xdl_emit_record(&xe->xdf2, s2, " ", ecb) < 0)
 				return -1;
 
 		for (s1 = xch->i1, s2 = xch->i2;; xch = xch->next) {
@@ -170,7 +213,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 			 * Merge previous with current change atom.
 			 */
 			for (; s1 < xch->i1 && s2 < xch->i2; s1++, s2++)
-				if (xdl_emit_record(&xe->xdf1, s1, " ", ecb) < 0)
+				if (xdl_emit_record(&xe->xdf2, s2, " ", ecb) < 0)
 					return -1;
 
 			/*
@@ -196,8 +239,8 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		/*
 		 * Emit post-context.
 		 */
-		for (s1 = xche->i1 + xche->chg1; s1 < e1; s1++)
-			if (xdl_emit_record(&xe->xdf1, s1, " ", ecb) < 0)
+		for (s2 = xche->i2 + xche->chg2; s2 < e2; s2++)
+			if (xdl_emit_record(&xe->xdf2, s2, " ", ecb) < 0)
 				return -1;
 	}