Commit aeb5ee5ab50a062aac02ca084b02582430669808
2016-05-17T15:40:46
varint: Add varint encoding/decoding This code is ported from git.git Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: David Turner <dturner@twopensource.com>
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diff --git a/src/varint.c b/src/varint.c
new file mode 100644
index 0000000..2f86860
--- /dev/null
+++ b/src/varint.c
@@ -0,0 +1,44 @@
+/*
+ * 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.
+ */
+
+#include "common.h"
+#include "varint.h"
+
+uintmax_t git_decode_varint(const unsigned char *bufp, size_t *varint_len)
+{
+ const unsigned char *buf = bufp;
+ unsigned char c = *buf++;
+ uintmax_t val = c & 127;
+ while (c & 128) {
+ val += 1;
+ if (!val || MSB(val, 7)) {
+ /* This is not a valid varint_len, so it signals
+ the error */
+ *varint_len = 0;
+ return 0; /* overflow */
+ }
+ c = *buf++;
+ val = (val << 7) + (c & 127);
+ }
+ *varint_len = buf - bufp;
+ return val;
+}
+
+int git_encode_varint(unsigned char *buf, size_t bufsize, uintmax_t value)
+{
+ unsigned char varint[16];
+ unsigned pos = sizeof(varint) - 1;
+ varint[pos] = value & 127;
+ while (value >>= 7)
+ varint[--pos] = 128 | (--value & 127);
+ if (buf) {
+ if (bufsize < pos)
+ return -1;
+ memcpy(buf, varint + pos, sizeof(varint) - pos);
+ }
+ return sizeof(varint) - pos;
+}
diff --git a/src/varint.h b/src/varint.h
new file mode 100644
index 0000000..650ec7d
--- /dev/null
+++ b/src/varint.h
@@ -0,0 +1,15 @@
+/*
+ * 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_varint_h__
+#define INCLUDE_varint_h__
+
+#include <stdint.h>
+
+extern int git_encode_varint(unsigned char *, size_t, uintmax_t);
+extern uintmax_t git_decode_varint(const unsigned char *, size_t *);
+
+#endif
diff --git a/tests/core/encoding.c b/tests/core/encoding.c
new file mode 100644
index 0000000..7d91720
--- /dev/null
+++ b/tests/core/encoding.c
@@ -0,0 +1,39 @@
+#include "clar_libgit2.h"
+#include "varint.h"
+
+void test_core_encoding__decode(void)
+{
+ const unsigned char *buf = (unsigned char *)"AB";
+ size_t size;
+
+ cl_assert(git_decode_varint(buf, &size) == 65);
+ cl_assert(size == 1);
+
+ buf = (unsigned char *)"\xfe\xdc\xbaXY";
+ cl_assert(git_decode_varint(buf, &size) == 267869656);
+ cl_assert(size == 4);
+
+ buf = (unsigned char *)"\xaa\xaa\xfe\xdc\xbaXY";
+ cl_assert(git_decode_varint(buf, &size) == 1489279344088ULL);
+ cl_assert(size == 6);
+
+ buf = (unsigned char *)"\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xfe\xdc\xbaXY";
+ cl_assert(git_decode_varint(buf, &size) == 0);
+ cl_assert(size == 0);
+
+}
+
+void test_core_encoding__encode(void)
+{
+ unsigned char buf[100];
+ cl_assert(git_encode_varint(buf, 100, 65) == 1);
+ cl_assert(buf[0] == 'A');
+
+ cl_assert(git_encode_varint(buf, 100, 267869656) == 4);
+ cl_assert(!memcmp(buf, "\xfe\xdc\xbaX", 4));
+
+ cl_assert(git_encode_varint(buf, 100, 1489279344088ULL) == 6);
+ cl_assert(!memcmp(buf, "\xaa\xaa\xfe\xdc\xbaX", 6));
+
+ cl_assert(git_encode_varint(buf, 1, 1489279344088ULL) == -1);
+}