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//
// Copyright 2016 gRPC authors.
//
// 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 "src/core/lib/slice/slice_hash_table.h"
#include <stdbool.h>
#include <string.h>
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include "src/core/lib/slice/slice_internal.h"
#include "src/core/lib/transport/metadata.h"
struct grpc_slice_hash_table {
gpr_refcount refs;
void (*destroy_value)(grpc_exec_ctx* exec_ctx, void* value);
int (*value_cmp)(void* a, void* b);
size_t size;
size_t max_num_probes;
grpc_slice_hash_table_entry* entries;
};
static bool is_empty(grpc_slice_hash_table_entry* entry) {
return entry->value == NULL;
}
static void grpc_slice_hash_table_add(grpc_slice_hash_table* table,
grpc_slice key, void* value) {
GPR_ASSERT(value != NULL);
const size_t hash = grpc_slice_hash(key);
for (size_t offset = 0; offset < table->size; ++offset) {
const size_t idx = (hash + offset) % table->size;
if (is_empty(&table->entries[idx])) {
table->entries[idx].key = key;
table->entries[idx].value = value;
// Keep track of the maximum number of probes needed, since this
// provides an upper bound for lookups.
if (offset > table->max_num_probes) table->max_num_probes = offset;
return;
}
}
GPR_ASSERT(false); // Table should never be full.
}
grpc_slice_hash_table* grpc_slice_hash_table_create(
size_t num_entries, grpc_slice_hash_table_entry* entries,
void (*destroy_value)(grpc_exec_ctx* exec_ctx, void* value),
int (*value_cmp)(void* a, void* b)) {
grpc_slice_hash_table* table =
(grpc_slice_hash_table*)gpr_zalloc(sizeof(*table));
gpr_ref_init(&table->refs, 1);
table->destroy_value = destroy_value;
table->value_cmp = value_cmp;
// Keep load factor low to improve performance of lookups.
table->size = num_entries * 2;
const size_t entry_size = sizeof(grpc_slice_hash_table_entry) * table->size;
table->entries = (grpc_slice_hash_table_entry*)gpr_zalloc(entry_size);
for (size_t i = 0; i < num_entries; ++i) {
grpc_slice_hash_table_entry* entry = &entries[i];
grpc_slice_hash_table_add(table, entry->key, entry->value);
}
return table;
}
grpc_slice_hash_table* grpc_slice_hash_table_ref(grpc_slice_hash_table* table) {
if (table != NULL) gpr_ref(&table->refs);
return table;
}
void grpc_slice_hash_table_unref(grpc_exec_ctx* exec_ctx,
grpc_slice_hash_table* table) {
if (table != NULL && gpr_unref(&table->refs)) {
for (size_t i = 0; i < table->size; ++i) {
grpc_slice_hash_table_entry* entry = &table->entries[i];
if (!is_empty(entry)) {
grpc_slice_unref_internal(exec_ctx, entry->key);
table->destroy_value(exec_ctx, entry->value);
}
}
gpr_free(table->entries);
gpr_free(table);
}
}
void* grpc_slice_hash_table_get(const grpc_slice_hash_table* table,
const grpc_slice key) {
const size_t hash = grpc_slice_hash(key);
// We cap the number of probes at the max number recorded when
// populating the table.
for (size_t offset = 0; offset <= table->max_num_probes; ++offset) {
const size_t idx = (hash + offset) % table->size;
if (is_empty(&table->entries[idx])) break;
if (grpc_slice_eq(table->entries[idx].key, key)) {
return table->entries[idx].value;
}
}
return NULL; // Not found.
}
static int pointer_cmp(void* a, void* b) { return GPR_ICMP(a, b); }
int grpc_slice_hash_table_cmp(const grpc_slice_hash_table* a,
const grpc_slice_hash_table* b) {
int (*const value_cmp_fn_a)(void* a, void* b) =
a->value_cmp != NULL ? a->value_cmp : pointer_cmp;
int (*const value_cmp_fn_b)(void* a, void* b) =
b->value_cmp != NULL ? b->value_cmp : pointer_cmp;
// Compare value_fns
const int value_fns_cmp =
GPR_ICMP((void*)value_cmp_fn_a, (void*)value_cmp_fn_b);
if (value_fns_cmp != 0) return value_fns_cmp;
// Compare sizes
if (a->size < b->size) return -1;
if (a->size > b->size) return 1;
// Compare rows.
for (size_t i = 0; i < a->size; ++i) {
if (is_empty(&a->entries[i])) {
if (!is_empty(&b->entries[i])) {
return -1; // a empty but b non-empty
}
continue; // both empty, no need to check key or value
} else if (is_empty(&b->entries[i])) {
return 1; // a non-empty but b empty
}
// neither entry is empty
const int key_cmp = grpc_slice_cmp(a->entries[i].key, b->entries[i].key);
if (key_cmp != 0) return key_cmp;
const int value_cmp =
value_cmp_fn_a(a->entries[i].value, b->entries[i].value);
if (value_cmp != 0) return value_cmp;
}
return 0;
}
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