X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=blobdiff_plain;f=xdiff-interface.c;h=61dc5c547019776b971dc89d009f628bbac134fd;hb=fae09a8084c9b51632726523b477a78dd28d7d7e;hp=be866d12d38f6f1328f5fae8c7108176d4ecba70;hpb=a6954452ecf757523b31d6eaaf7e00c7a2d91e46;p=git.git

diff --git a/xdiff-interface.c b/xdiff-interface.c
index be866d12d..61dc5c547 100644
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -103,6 +103,44 @@ int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf)
 	return 0;
 }
 
+/*
+ * Trim down common substring at the end of the buffers,
+ * but leave at least ctx lines at the end.
+ */
+static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx)
+{
+	const int blk = 1024;
+	long trimmed = 0, recovered = 0;
+	char *ap = a->ptr + a->size;
+	char *bp = b->ptr + b->size;
+	long smaller = (a->size < b->size) ? a->size : b->size;
+
+	if (ctx)
+		return;
+
+	while (blk + trimmed <= smaller && !memcmp(ap - blk, bp - blk, blk)) {
+		trimmed += blk;
+		ap -= blk;
+		bp -= blk;
+	}
+
+	while (recovered < trimmed)
+		if (ap[recovered++] == '\n')
+			break;
+	a->size -= trimmed - recovered;
+	b->size -= trimmed - recovered;
+}
+
+int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *xecb)
+{
+	mmfile_t a = *mf1;
+	mmfile_t b = *mf2;
+
+	trim_common_tail(&a, &b, xecfg->ctxlen);
+
+	return xdl_diff(&a, &b, xpp, xecfg, xecb);
+}
+
 int read_mmfile(mmfile_t *ptr, const char *filename)
 {
 	struct stat st;
@@ -114,8 +152,8 @@ int read_mmfile(mmfile_t *ptr, const char *filename)
 	if ((f = fopen(filename, "rb")) == NULL)
 		return error("Could not open %s", filename);
 	sz = xsize_t(st.st_size);
-	ptr->ptr = xmalloc(sz);
-	if (fread(ptr->ptr, sz, 1, f) != 1)
+	ptr->ptr = xmalloc(sz ? sz : 1);
+	if (sz && fread(ptr->ptr, sz, 1, f) != 1)
 		return error("Could not read %s", filename);
 	fclose(f);
 	ptr->size = sz;
@@ -195,8 +233,7 @@ void xdiff_set_find_func(xdemitconf_t *xecfg, const char *value)
 			expression = value;
 		if (regcomp(&reg->re, expression, 0))
 			die("Invalid regexp to look for hunk header: %s", expression);
-		if (buffer)
-			free(buffer);
+		free(buffer);
 		value = ep + 1;
 	}
 }