diff options
author | Lennart Poettering <lennart@poettering.net> | 2018-02-08 18:31:15 +0100 |
---|---|---|
committer | Sven Eden <yamakuzure@gmx.net> | 2018-05-30 07:54:00 +0200 |
commit | 743ac495b83a83e7336f55321d38a4ebe7389e58 (patch) | |
tree | 1b07c10fb3fd417601406084d5dacc6b3f7b476a /src/basic/hash-funcs.c | |
parent | 0c8cd4e223e968d446136379f6563d1a0aa82956 (diff) |
hash-func: add generic hash_ops implementation for hashing paths
This is similar to string_hash_ops but operates one file system paths
specifically. It will ensure that "/foo//bar" and "///foo/bar" are
considered to be the same path for hashmap purposes.
This makes use of the existing path_compare() API, and adds a matching
hashing function for it.
Note that relative and absolute paths will hash to different values,
however whether the path is suffixed with a slash or not is not
detected. This matches the existing path_compare() behaviour, and
follows the logic that on Linux there can't be two different objects at
path /foo/bar and /foo/bar/ either.
(cherry picked from commit 46e16b347f83d809ed3d34f26286f580dfd086ce)
Diffstat (limited to 'src/basic/hash-funcs.c')
-rw-r--r-- | src/basic/hash-funcs.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/src/basic/hash-funcs.c b/src/basic/hash-funcs.c index 1716401d1..763c1f61d 100644 --- a/src/basic/hash-funcs.c +++ b/src/basic/hash-funcs.c @@ -22,6 +22,7 @@ //#include <string.h> #include "hash-funcs.h" +//#include "path-util.h" void string_hash_func(const void *p, struct siphash *state) { siphash24_compress(p, strlen(p) + 1, state); @@ -36,6 +37,55 @@ const struct hash_ops string_hash_ops = { .compare = string_compare_func }; + +void path_hash_func(const void *p, struct siphash *state) { + const char *q = p; + size_t n; + + assert(q); + assert(state); + + /* Calculates a hash for a path in a way this duplicate inner slashes don't make a differences, and also + * whether there's a trailing slash or not. This fits well with the semantics of path_compare(), which does + * similar checks and also doesn't care for trailing slashes. Note that relative and absolute paths (i.e. those + * which begin in a slash or not) will hash differently though. */ + + n = strspn(q, "/"); + if (n > 0) { /* Eat up initial slashes, and add one "/" to the hash for all of them */ + siphash24_compress(q, 1, state); + q += n; + } + + for (;;) { + /* Determine length of next component */ + n = strcspn(q, "/"); + if (n == 0) /* Reached the end? */ + break; + + /* Add this component to the hash and skip over it */ + siphash24_compress(q, n, state); + q += n; + + /* How many slashes follow this component? */ + n = strspn(q, "/"); + if (q[n] == 0) /* Is this a trailing slash? If so, we are at the end, and don't care about the slashes anymore */ + break; + + /* We are not add the end yet. Hash exactly one slash for all of the ones we just encountered. */ + siphash24_compress(q, 1, state); + q += n; + } +} + +int path_compare_func(const void *a, const void *b) { + return path_compare(a, b); +} + +const struct hash_ops path_hash_ops = { + .hash = path_hash_func, + .compare = path_compare_func +}; + void trivial_hash_func(const void *p, struct siphash *state) { siphash24_compress(&p, sizeof(p), state); } |