mirror/ git
1
0
Fork 0
mirror of https://github.com/git/git.git synced 2024-05-06 01:46:12 +02:00
Code

hashmap: allow memihash computation to be continued 

Add variant of memihash() to allow the hash computation to
be continued.  There are times when we compute the hash on
a full path and then the hash on just the path to the parent
directory.  This can be expensive on large repositories.

With this, we can hash the parent directory first. And then
continue the computation to include the "/filename".

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff Hostetler 2017-03-22 17:14:21 +00:00 committed by Junio C Hamano
parent 16f9b4cdd3
commit f75619bd6d
2 changed files with 18 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
hashmap.c
View File

@ -50,6 +50,23 @@ unsigned int memihash(const void *buf, size_t len)
return hash;
}
/*
* Incoporate another chunk of data into a memihash
* computation.
*/
unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)
{
unsigned int hash = hash_seed;
unsigned char *ucbuf = (unsigned char *) buf;
while (len--) {
unsigned int c = *ucbuf++;
if (c >= 'a' && c <= 'z')
c -= 'a' - 'A';
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
#define HASHMAP_INITIAL_SIZE 64
/* grow / shrink by 2^2 */
#define HASHMAP_RESIZE_BITS 2

1
hashmap.h
View File

@ -12,6 +12,7 @@ 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 memihash(const void *buf, size_t len);
extern unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len);
static inline unsigned int sha1hash(const unsigned char *sha1)
{