1 files changed, 117 insertions, 0 deletions
diff --git a/merge-file.c b/merge-file.c
new file mode 100644
index 0000000000..748d15c0e0
--- /dev/null
+++ b/merge-file.c
@@ -0,0 +1,117 @@
+#include "cache.h"
+#include "run-command.h"
+#include "xdiff-interface.h"
+#include "blob.h"
+
+static int fill_mmfile_blob(mmfile_t *f, struct blob *obj)
+{
+	void *buf;
+	unsigned long size;
+	enum object_type type;
+
+	buf = read_sha1_file(obj->object.sha1, &type, &size);
+	if (!buf)
+		return -1;
+	if (type != OBJ_BLOB)
+		return -1;
+	f->ptr = buf;
+	f->size = size;
+	return 0;
+}
+
+static void free_mmfile(mmfile_t *f)
+{
+	free(f->ptr);
+}
+
+static void *three_way_filemerge(mmfile_t *base, mmfile_t *our, mmfile_t *their, unsigned long *size)
+{
+	mmbuffer_t res;
+	xpparam_t xpp;
+	int merge_status;
+
+	memset(&xpp, 0, sizeof(xpp));
+	merge_status = xdl_merge(base, our, ".our", their, ".their",
+		&xpp, XDL_MERGE_ZEALOUS, &res);
+
+	if (merge_status < 0)
+		return NULL;
+
+	*size = res.size;
+	return res.ptr;
+}
+
+static int common_outf(void *priv_, mmbuffer_t *mb, int nbuf)
+{
+	int i;
+	mmfile_t *dst = priv_;
+
+	for (i = 0; i < nbuf; i++) {
+		memcpy(dst->ptr + dst->size, mb[i].ptr, mb[i].size);
+		dst->size += mb[i].size;
+	}
+	return 0;
+}
+
+static int generate_common_file(mmfile_t *res, mmfile_t *f1, mmfile_t *f2)
+{
+	unsigned long size = f1->size < f2->size ? f1->size : f2->size;
+	void *ptr = xmalloc(size);
+	xpparam_t xpp;
+	xdemitconf_t xecfg;
+	xdemitcb_t ecb;
+
+	xpp.flags = XDF_NEED_MINIMAL;
+	xecfg.ctxlen = 3;
+	xecfg.flags = XDL_EMIT_COMMON;
+	ecb.outf = common_outf;
+
+	res->ptr = ptr;
+	res->size = 0;
+
+	ecb.priv = res;
+	return xdl_diff(f1, f2, &xpp, &xecfg, &ecb);
+}
+
+void *merge_file(struct blob *base, struct blob *our, struct blob *their, unsigned long *size)
+{
+	void *res = NULL;
+	mmfile_t f1, f2, common;
+
+	/*
+	 * Removed in either branch?
+	 *
+	 * NOTE! This depends on the caller having done the
+	 * proper warning about removing a file that got
+	 * modified in the other branch!
+	 */
+	if (!our || !their) {
+		enum object_type type;
+		if (base)
+			return NULL;
+		if (!our)
+			our = their;
+		return read_sha1_file(our->object.sha1, &type, size);
+	}
+
+	if (fill_mmfile_blob(&f1, our) < 0)
+		goto out_no_mmfile;
+	if (fill_mmfile_blob(&f2, their) < 0)
+		goto out_free_f1;
+
+	if (base) {
+		if (fill_mmfile_blob(&common, base) < 0)
+			goto out_free_f2_f1;
+	} else {
+		if (generate_common_file(&common, &f1, &f2) < 0)
+			goto out_free_f2_f1;
+	}
+	res = three_way_filemerge(&common, &f1, &f2, size);
+	free_mmfile(&common);
+out_free_f2_f1:
+	free_mmfile(&f2);
+out_free_f1:
+	free_mmfile(&f1);
+out_no_mmfile:
+	return res;
+}