When parsing capabilities for the pack protocol, there are times we'll
want to compare the value of a capability to a NUL-terminated string.
Since the data we're reading will be space-terminated, not
NUL-terminated, we need a function that compares the two strings, but
also checks that they're the same length. Otherwise, if we used strncmp
to compare these strings, we might accidentally accept a parameter that
was a prefix of the expected value.
Add a function, xstrncmpz, that takes a NUL-terminated string and a
non-NUL-terminated string, plus a length, and compares them, ensuring
that they are the same length.
Signed-off-by: brian m. carlson <sandals@xxxxxxxxxxxxxxxxxxxx>
---
git-compat-util.h | 2 ++
wrapper.c | 12 ++++++++++++
2 files changed, 14 insertions(+)
diff --git a/git-compat-util.h b/git-compat-util.h
index 8ba576e81e..6503deb171 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -868,6 +868,8 @@ char *xgetcwd(void);
FILE *fopen_for_writing(const char *path);
FILE *fopen_or_warn(const char *path, const char *mode);
+int xstrncmpz(const char *s, const char *t, size_t len);
+
/*
* FREE_AND_NULL(ptr) is like free(ptr) followed by ptr = NULL. Note
* that ptr is used twice, so don't pass e.g. ptr++.
diff --git a/wrapper.c b/wrapper.c
index 3a1c0e0526..15a09740e7 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -430,6 +430,18 @@ int xmkstemp(char *filename_template)
return fd;
}
+/*
+ * Like strncmp, but only return zero if s is NUL-terminated and exactly len
+ * characters long. If it is not, consider it greater than t.
+ */
+int xstrncmpz(const char *s, const char *t, size_t len)
+{
+ int res = strncmp(s, t, len);
+ if (res)
+ return res;
+ return s[len] == '\0' ? 0 : 1;
+}
+
/* Adapted from libiberty's mkstemp.c. */
#undef TMP_MAX
