1 files changed, 106 insertions, 0 deletions
diff --git a/include/git2/sys/hashsig.h b/include/git2/sys/hashsig.h
new file mode 100644
index 0000000..09c19ae
--- /dev/null
+++ b/include/git2/sys/hashsig.h
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_sys_hashsig_h__
+#define INCLUDE_sys_hashsig_h__
+
+#include "git2/common.h"
+
+GIT_BEGIN_DECL
+
+/**
+ * Similarity signature of arbitrary text content based on line hashes
+ */
+typedef struct git_hashsig git_hashsig;
+
+/**
+ * Options for hashsig computation
+ *
+ * The options GIT_HASHSIG_NORMAL, GIT_HASHSIG_IGNORE_WHITESPACE,
+ * GIT_HASHSIG_SMART_WHITESPACE are exclusive and should not be combined.
+ */
+typedef enum {
+	/**
+	 * Use all data
+	 */
+	GIT_HASHSIG_NORMAL = 0,
+
+	/**
+	 * Ignore whitespace
+	 */
+	GIT_HASHSIG_IGNORE_WHITESPACE = (1 << 0),
+
+	/**
+	 * Ignore \r and all space after \n
+	 */
+	GIT_HASHSIG_SMART_WHITESPACE = (1 << 1),
+
+	/**
+	 * Allow hashing of small files
+	 */
+	GIT_HASHSIG_ALLOW_SMALL_FILES = (1 << 2)
+} git_hashsig_option_t;
+
+/**
+ * Compute a similarity signature for a text buffer
+ *
+ * If you have passed the option GIT_HASHSIG_IGNORE_WHITESPACE, then the
+ * whitespace will be removed from the buffer while it is being processed,
+ * modifying the buffer in place. Sorry about that!
+ *
+ * @param out The computed similarity signature.
+ * @param buf The input buffer.
+ * @param buflen The input buffer size.
+ * @param opts The signature computation options (see above).
+ * @return 0 on success, GIT_EBUFS if the buffer doesn't contain enough data to
+ * compute a valid signature (unless GIT_HASHSIG_ALLOW_SMALL_FILES is set), or
+ * error code.
+ */
+GIT_EXTERN(int) git_hashsig_create(
+	git_hashsig **out,
+	const char *buf,
+	size_t buflen,
+	git_hashsig_option_t opts);
+
+/**
+ * Compute a similarity signature for a text file
+ *
+ * This walks through the file, only loading a maximum of 4K of file data at
+ * a time. Otherwise, it acts just like `git_hashsig_create`.
+ *
+ * @param out The computed similarity signature.
+ * @param path The path to the input file.
+ * @param opts The signature computation options (see above).
+ * @return 0 on success, GIT_EBUFS if the buffer doesn't contain enough data to
+ * compute a valid signature (unless GIT_HASHSIG_ALLOW_SMALL_FILES is set), or
+ * error code.
+ */
+GIT_EXTERN(int) git_hashsig_create_fromfile(
+	git_hashsig **out,
+	const char *path,
+	git_hashsig_option_t opts);
+
+/**
+ * Release memory for a content similarity signature
+ *
+ * @param sig The similarity signature to free.
+ */
+GIT_EXTERN(void) git_hashsig_free(git_hashsig *sig);
+
+/**
+ * Measure similarity score between two similarity signatures
+ *
+ * @param a The first similarity signature to compare.
+ * @param b The second similarity signature to compare.
+ * @return [0 to 100] on success as the similarity score, or error code.
+ */
+GIT_EXTERN(int) git_hashsig_compare(
+	const git_hashsig *a,
+	const git_hashsig *b);
+
+GIT_END_DECL
+
+#endif