status-go/vendor/github.com/anacrolix/go-libutp/utp_hash.cpp

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2022-03-10 09:44:48 +00:00
/*
* Copyright (c) 2010-2013 BitTorrent, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "utp_hash.h"
#include "utp_types.h"
#define LIBUTP_HASH_UNUSED ((utp_link_t)-1)
#ifdef STRICT_ALIGN
inline uint32 Read32(const void *p)
{
uint32 tmp;
memcpy(&tmp, p, sizeof tmp);
return tmp;
}
#else
inline uint32 Read32(const void *p) { return *(uint32*)p; }
#endif
// Get the amount of memory required for the hash parameters and the bucket set
// Waste a space for an unused bucket in order to ensure the following managed memory have 32-bit aligned addresses
// TODO: make this 64-bit clean
#define BASE_SIZE(bc) (sizeof(utp_hash_t) + sizeof(utp_link_t) * ((bc) + 1))
// Get a pointer to the base of the structure array managed by the hash table
#define get_bep(h) ((byte*)(h)) + BASE_SIZE((h)->N)
// Get the address of the information associated with a specific structure in the array,
// given the address of the base of the structure.
// This assumes a utp_link_t link member is at the end of the structure.
// Given compilers filling out the memory to a 32-bit clean value, this may mean that
// the location named in the structure may not be the location actually used by the hash table,
// since the compiler may have padded the end of the structure with 2 bytes after the utp_link_t member.
// TODO: this macro should not require that the variable pointing at the hash table be named 'hash'
#define ptr_to_link(p) (utp_link_t *) (((byte *) (p)) + hash->E - sizeof(utp_link_t))
// Calculate how much to allocate for a hash table with bucket count, total size, and structure count
// TODO: make this 64-bit clean
#define ALLOCATION_SIZE(bc, ts, sc) (BASE_SIZE((bc)) + (ts) * (sc))
utp_hash_t *utp_hash_create(int N, int key_size, int total_size, int initial, utp_hash_compute_t hashfun, utp_hash_equal_t compfun)
{
// Must have odd number of hash buckets (prime number is best)
assert(N % 2);
// Ensure structures will be at aligned memory addresses
// TODO: make this 64-bit clean
assert(0 == (total_size % 4));
int size = ALLOCATION_SIZE(N, total_size, initial);
utp_hash_t *hash = (utp_hash_t *) malloc( size );
memset( hash, 0, size );
for (int i = 0; i < N + 1; ++i)
hash->inits[i] = LIBUTP_HASH_UNUSED;
hash->N = N;
hash->K = key_size;
hash->E = total_size;
hash->hash_compute = hashfun;
hash->hash_equal = compfun;
hash->allocated = initial;
hash->count = 0;
hash->used = 0;
hash->free = LIBUTP_HASH_UNUSED;
return hash;
}
uint utp_hash_mem(const void *keyp, size_t keysize)
{
uint hash = 0;
uint n = keysize;
while (n >= 4) {
hash ^= Read32(keyp);
keyp = (byte*)keyp + sizeof(uint32);
hash = (hash << 13) | (hash >> 19);
n -= 4;
}
while (n != 0) {
hash ^= *(byte*)keyp;
keyp = (byte*)keyp + sizeof(byte);
hash = (hash << 8) | (hash >> 24);
n--;
}
return hash;
}
uint utp_hash_mkidx(utp_hash_t *hash, const void *keyp)
{
// Generate a key from the hash
return hash->hash_compute(keyp, hash->K) % hash->N;
}
static inline bool compare(byte *a, byte *b,int n)
{
assert(n >= 4);
if (Read32(a) != Read32(b)) return false;
return memcmp(a+4, b+4, n-4) == 0;
}
#define COMPARE(h,k1,k2,ks) (((h)->hash_equal) ? (h)->hash_equal((void*)k1,(void*)k2,ks) : compare(k1,k2,ks))
// Look-up a key in the hash table.
// Returns NULL if not found
void *utp_hash_lookup(utp_hash_t *hash, const void *key)
{
utp_link_t idx = utp_hash_mkidx(hash, key);
// base pointer
byte *bep = get_bep(hash);
utp_link_t cur = hash->inits[idx];
while (cur != LIBUTP_HASH_UNUSED) {
byte *key2 = bep + (cur * hash->E);
if (COMPARE(hash, (byte*)key, key2, hash->K))
return key2;
cur = *ptr_to_link(key2);
}
return NULL;
}
// Add a new element to the hash table.
// Returns a pointer to the new element.
// This assumes the element is not already present!
void *utp_hash_add(utp_hash_t **hashp, const void *key)
{
//Allocate a new entry
byte *elemp;
utp_link_t elem;
utp_hash_t *hash = *hashp;
utp_link_t idx = utp_hash_mkidx(hash, key);
if ((elem=hash->free) == LIBUTP_HASH_UNUSED) {
utp_link_t all = hash->allocated;
if (hash->used == all) {
utp_hash_t *nhash;
if (all <= (LIBUTP_HASH_UNUSED/2)) {
all *= 2;
} else if (all != LIBUTP_HASH_UNUSED) {
all = LIBUTP_HASH_UNUSED;
} else {
// too many items! can't grow!
assert(0);
return NULL;
}
// otherwise need to allocate.
nhash = (utp_hash_t*)realloc(hash, ALLOCATION_SIZE(hash->N, hash->E, all));
if (!nhash) {
// out of memory (or too big to allocate)
assert(nhash);
return NULL;
}
hash = *hashp = nhash;
hash->allocated = all;
}
elem = hash->used++;
elemp = get_bep(hash) + elem * hash->E;
} else {
elemp = get_bep(hash) + elem * hash->E;
hash->free = *ptr_to_link(elemp);
}
*ptr_to_link(elemp) = hash->inits[idx];
hash->inits[idx] = elem;
hash->count++;
// copy key into it
memcpy(elemp, key, hash->K);
return elemp;
}
// Delete an element from the utp_hash_t
// Returns a pointer to the already deleted element.
void *utp_hash_del(utp_hash_t *hash, const void *key)
{
utp_link_t idx = utp_hash_mkidx(hash, key);
// base pointer
byte *bep = get_bep(hash);
utp_link_t *curp = &hash->inits[idx];
utp_link_t cur;
while ((cur=*curp) != LIBUTP_HASH_UNUSED) {
byte *key2 = bep + (cur * hash->E);
if (COMPARE(hash,(byte*)key,(byte*)key2, hash->K )) {
// found an item that matched. unlink it
*curp = *ptr_to_link(key2);
// Insert into freelist
*ptr_to_link(key2) = hash->free;
hash->free = cur;
hash->count--;
return key2;
}
curp = ptr_to_link(key2);
}
return NULL;
}
void *utp_hash_iterate(utp_hash_t *hash, utp_hash_iterator_t *iter)
{
utp_link_t elem;
if ((elem=iter->elem) == LIBUTP_HASH_UNUSED) {
// Find a bucket with an element
utp_link_t buck = iter->bucket + 1;
for(;;) {
if (buck >= hash->N)
return NULL;
if ((elem = hash->inits[buck]) != LIBUTP_HASH_UNUSED)
break;
buck++;
}
iter->bucket = buck;
}
byte *elemp = get_bep(hash) + (elem * hash->E);
iter->elem = *ptr_to_link(elemp);
return elemp;
}
void utp_hash_free_mem(utp_hash_t* hash)
{
free(hash);
}