wrapper: add function to compare strings with different NUL termination

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@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

brian m. carlson committed May 25, 2020 at 19:58 UTC 14570dc67d2a500dfb9f33a7445bdbd6133af4ac

2 files changed +14

git-compat-util.h

@@ -868,6 +868,12 @@ char *xgetcwd(void);

868 FILE *fopen_for_writing(const char *path);

869 FILE *fopen_or_warn(const char *path, const char *mode);

870

871 +/*

872 + * Like strncmp, but only return zero if s is NUL-terminated and exactly len

873 + * characters long. If it is not, consider it greater than t.

874 + */

875 +int xstrncmpz(const char *s, const char *t, size_t len);

876 +

877 /*

878 * FREE_AND_NULL(ptr) is like free(ptr) followed by ptr = NULL. Note

879 * that ptr is used twice, so don't pass e.g. ptr++.

wrapper.c

@@ -105,6 +105,14 @@ char *xstrndup(const char *str, size_t len)

105 return xmemdupz(str, p ? p - str : len);

106 }

107

108 +int xstrncmpz(const char *s, const char *t, size_t len)

109 +{

110 + int res = strncmp(s, t, len);

111 + if (res)

112 + return res;

113 + return s[len] == '\0' ? 0 : 1;

114 +}

115 +

116 void *xrealloc(void *ptr, size_t size)

117 {

118 void *ret;