Commit 8a5e7aaecf7ce48dfab805debfc92458ab1112c5
2017-05-22T12:53:44
varint: fix computation for remaining buffer space When encoding varints to a buffer, we want to remain sure that the required buffer space does not exceed what is actually available. Our current check does not do the right thing, though, in that it does not honor that our `pos` variable counts the position down instead of up. As such, we will require too much memory for small varints and not enough memory for big varints. Fix the issue by correctly calculating the required size as `(sizeof(varint) - pos)`. Add a test which failed before.
diff --git a/src/varint.c b/src/varint.c
index 2f86860..beac8c7 100644
--- a/src/varint.c
+++ b/src/varint.c
@@ -36,7 +36,7 @@ int git_encode_varint(unsigned char *buf, size_t bufsize, uintmax_t value)
while (value >>= 7)
varint[--pos] = 128 | (--value & 127);
if (buf) {
- if (bufsize < pos)
+ if (bufsize < (sizeof(varint) - pos))
return -1;
memcpy(buf, varint + pos, sizeof(varint) - pos);
}
diff --git a/tests/core/encoding.c b/tests/core/encoding.c
index 7d91720..a677afe 100644
--- a/tests/core/encoding.c
+++ b/tests/core/encoding.c
@@ -29,6 +29,9 @@ void test_core_encoding__encode(void)
cl_assert(git_encode_varint(buf, 100, 65) == 1);
cl_assert(buf[0] == 'A');
+ cl_assert(git_encode_varint(buf, 1, 1) == 1);
+ cl_assert(!memcmp(buf, "\x01", 1));
+
cl_assert(git_encode_varint(buf, 100, 267869656) == 4);
cl_assert(!memcmp(buf, "\xfe\xdc\xbaX", 4));