add skip_prefix_mem helper
The skip_prefix function has been very useful for simplifying pointer arithmetic and avoiding repeated magic numbers, but we have no equivalent for length-limited buffers. So we're stuck with: if (3 <= len && skip_prefix(buf, "foo", &buf)) len -= 3; That's not that complicated, but it needs to use magic numbers for the length of the prefix (or else write out strlen("foo"), repeating the string). By using a helper, we can get the string length behind the scenes (and often at compile time for string literals). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff King committed
Jun 23, 2016 at 13:33 UTC
ae989a61dad98debe9899823ca987305f8e8020d
1 file changed
+17
git-compat-util.h
+17
@@ -463,6 +463,23 @@ static inline int skip_prefix(const char *str, const char *prefix,
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return 0;
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}
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+/*
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+ * Like skip_prefix, but promises never to read past "len" bytes of the input
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+ * buffer, and returns the remaining number of bytes in "out" via "outlen".
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+ */
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+static inline int skip_prefix_mem(const char *buf, size_t len,
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+ const char *prefix,
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+ const char **out, size_t *outlen)
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+{
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+ size_t prefix_len = strlen(prefix);
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+ if (prefix_len <= len && !memcmp(buf, prefix, prefix_len)) {
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+ *out = buf + prefix_len;
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+ *outlen = len - prefix_len;
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+ return 1;
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+ }
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+ return 0;
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+}
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+
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/*
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* If buf ends with suffix, return 1 and subtract the length of the suffix
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* from *len. Otherwise, return 0 and leave *len untouched.