[PATCH 1/4] hashmap: introduce memhash_feed to access the internals of FNV-1 hash
This will be useful shortly.
Signed-off-by: Stefan Beller <sbeller@google.com>
---
hashmap.c | 7 ++++++-
hashmap.h | 3 +++
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/hashmap.c b/hashmap.c
index d42f01ff5a..d103eb1fd2 100644
--- a/hashmap.c
+++ b/hashmap.c
@@ -26,13 +26,18 @@ unsigned int strihash(const char *str)
return hash;
}
+unsigned int memhash_feed(unsigned int hash_seed, const unsigned char next)
+{
+ return (hash_seed * FNV32_PRIME) ^ next;
+}
+
unsigned int memhash(const void *buf, size_t len)
{
unsigned int hash = FNV32_BASE;
unsigned char *ucbuf = (unsigned char *) buf;
while (len--) {
unsigned int c = *ucbuf++;
- hash = (hash * FNV32_PRIME) ^ c;
+ hash = memhash_feed(hash, c);
}
return hash;
}
diff --git a/hashmap.h b/hashmap.h
index 7cb29a6aed..c2464385ed 100644
--- a/hashmap.h
+++ b/hashmap.h
@@ -105,10 +105,13 @@
* `strihash` and `memihash` are case insensitive versions.
* `memihash_cont` is a variant of `memihash` that allows a computation to be
* continued with another chunk of data.
+ * `memhash_feed` takes just one character and returns the hash based off
+ * a previous hash.
*/
extern unsigned int strhash(const char *buf);
extern unsigned int strihash(const char *buf);
extern unsigned int memhash(const void *buf, size_t len);
+extern unsigned int memhash_feed(unsigned int hash_seed, const unsigned char next);
extern unsigned int memihash(const void *buf, size_t len);
extern unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len);
--
2.15.0.rc2.6.g953226eb5f
Stefan Beller <sbeller@google.com>