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/*
* Copyright 2016 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "wasm-binding-hash.h"
#define INITIAL_HASH_CAPACITY 8
static size_t hash_name(const WasmStringSlice* name) {
// FNV-1a hash
const uint32_t fnv_prime = 0x01000193;
const uint8_t* bp = (const uint8_t*)name->start;
const uint8_t* be = bp + name->length;
uint32_t hval = 0x811c9dc5;
while (bp < be) {
hval ^= (uint32_t)*bp++;
hval *= fnv_prime;
}
return hval;
}
static WasmBindingHashEntry* hash_main_entry(const WasmBindingHash* hash,
const WasmStringSlice* name) {
return &hash->entries.data[hash_name(name) % hash->entries.capacity];
}
WasmBool wasm_hash_entry_is_free(const WasmBindingHashEntry* entry) {
return !entry->binding.name.start;
}
static WasmBindingHashEntry* hash_new_entry(WasmBindingHash* hash,
const WasmStringSlice* name) {
WasmBindingHashEntry* entry = hash_main_entry(hash, name);
if (!wasm_hash_entry_is_free(entry)) {
assert(hash->free_head);
WasmBindingHashEntry* free_entry = hash->free_head;
hash->free_head = free_entry->next;
if (free_entry->next)
free_entry->next->prev = NULL;
/* our main position is already claimed. Check to see if the entry in that
* position is in its main position */
WasmBindingHashEntry* other_entry =
hash_main_entry(hash, &entry->binding.name);
if (other_entry == entry) {
/* yes, so add this new entry to the chain, even if it is already there */
/* add as the second entry in the chain */
free_entry->next = entry->next;
entry->next = free_entry;
entry = free_entry;
} else {
/* no, move the entry to the free entry */
assert(!wasm_hash_entry_is_free(other_entry));
while (other_entry->next != entry)
other_entry = other_entry->next;
other_entry->next = free_entry;
*free_entry = *entry;
entry->next = NULL;
}
} else {
/* remove from the free list */
if (entry->next)
entry->next->prev = entry->prev;
if (entry->prev)
entry->prev->next = entry->next;
else
hash->free_head = entry->next;
entry->next = NULL;
}
WASM_ZERO_MEMORY(entry->binding);
entry->binding.name = *name;
entry->prev = NULL;
/* entry->next is set above */
return entry;
}
static void hash_resize(WasmAllocator* allocator,
WasmBindingHash* hash,
size_t desired_capacity) {
WasmBindingHash new_hash;
WASM_ZERO_MEMORY(new_hash);
/* TODO(binji): better plural */
wasm_reserve_binding_hash_entrys(allocator, &new_hash.entries,
desired_capacity);
/* update the free list */
size_t i;
for (i = 0; i < new_hash.entries.capacity; ++i) {
WasmBindingHashEntry* entry = &new_hash.entries.data[i];
if (new_hash.free_head)
new_hash.free_head->prev = entry;
WASM_ZERO_MEMORY(entry->binding.name);
entry->next = new_hash.free_head;
new_hash.free_head = entry;
}
new_hash.free_head->prev = NULL;
/* copy from the old hash to the new hash */
for (i = 0; i < hash->entries.capacity; ++i) {
WasmBindingHashEntry* old_entry = &hash->entries.data[i];
if (wasm_hash_entry_is_free(old_entry))
continue;
WasmStringSlice* name = &old_entry->binding.name;
WasmBindingHashEntry* new_entry = hash_new_entry(&new_hash, name);
new_entry->binding = old_entry->binding;
}
/* we are sharing the WasmStringSlices, so we only need to destroy the old
* binding vector */
wasm_destroy_binding_hash_entry_vector(allocator, &hash->entries);
*hash = new_hash;
}
WasmBinding* wasm_insert_binding(WasmAllocator* allocator,
WasmBindingHash* hash,
const WasmStringSlice* name) {
if (hash->entries.size == 0)
hash_resize(allocator, hash, INITIAL_HASH_CAPACITY);
if (!hash->free_head) {
/* no more free space, allocate more */
hash_resize(allocator, hash, hash->entries.capacity * 2);
}
WasmBindingHashEntry* entry = hash_new_entry(hash, name);
assert(entry);
hash->entries.size++;
return &entry->binding;
}
int wasm_find_binding_index_by_name(const WasmBindingHash* hash,
const WasmStringSlice* name) {
if (hash->entries.capacity == 0)
return -1;
WasmBindingHashEntry* entry = hash_main_entry(hash, name);
do {
if (wasm_string_slices_are_equal(&entry->binding.name, name))
return entry->binding.index;
entry = entry->next;
} while (entry && !wasm_hash_entry_is_free(entry));
return -1;
}
static void destroy_binding_hash_entry(WasmAllocator* allocator,
WasmBindingHashEntry* entry) {
wasm_destroy_string_slice(allocator, &entry->binding.name);
}
void wasm_destroy_binding_hash(WasmAllocator* allocator,
WasmBindingHash* hash) {
/* Can't use WASM_DESTROY_VECTOR_AND_ELEMENTS, because it loops over size, not
* capacity. */
size_t i;
for (i = 0; i < hash->entries.capacity; ++i)
destroy_binding_hash_entry(allocator, &hash->entries.data[i]);
wasm_destroy_binding_hash_entry_vector(allocator, &hash->entries);
}
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