contrib/fuzz/bdiff.cc

transaction: explain why some recovery failed

Right now we issue a message about failing to recover some file, but not why.
It seems useful to add some information about that.

(This is an opportunity improvement while looking at something next to that.)

Differential Revision: https://phab.mercurial-scm.org/D10842

/*
 * bdiff.cc - fuzzer harness for bdiff.c
 *
 * Copyright 2018, Google Inc.
 *
 * This software may be used and distributed according to the terms of
 * the GNU General Public License, incorporated herein by reference.
 */
#include <memory>
#include <stdlib.h>

#include "FuzzedDataProvider.h"

extern "C" {
#include "bdiff.h"

extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv)
{
	return 0;
}

int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
{
	FuzzedDataProvider provider(Data, Size);
	std::string left = provider.ConsumeRandomLengthString(Size);
	std::string right = provider.ConsumeRemainingBytesAsString();

	struct bdiff_line *a, *b;
	int an = bdiff_splitlines(left.c_str(), left.size(), &a);
	int bn = bdiff_splitlines(right.c_str(), right.size(), &b);
	struct bdiff_hunk l;
	bdiff_diff(a, an, b, bn, &l);
	free(a);
	free(b);
	bdiff_freehunks(l.next);
	return 0; // Non-zero return values are reserved for future use.
}

} // extern "C"