ℹ️ New Book: Build Your Own Database
redis/13/zset.cpp
#include <assert.h>
#include <string.h>
#include <stdlib.h>
// proj
#include "zset.h"
#include "common.h"
static ZNode *znode_new(const char *name, size_t len, double score) {
ZNode *node = (ZNode *)malloc(sizeof(ZNode) + len);
assert(node); // not a good idea in real projects
avl_init(&node->tree);
node->hmap.next = NULL;
node->hmap.hcode = str_hash((uint8_t *)name, len);
node->score = score;
node->len = len;
memcpy(&node->name[0], name, len);
return node;
}
static uint32_t min(size_t lhs, size_t rhs) {
return lhs < rhs ? lhs : rhs;
}
// compare by the (score, name) tuple
static bool zless(
AVLNode *lhs, double score, const char *name, size_t len)
{
ZNode *zl = container_of(lhs, ZNode, tree);
if (zl->score != score) {
return zl->score < score;
}
int rv = memcmp(zl->name, name, min(zl->len, len));
if (rv != 0) {
return rv < 0;
}
return zl->len < len;
}
static bool zless(AVLNode *lhs, AVLNode *rhs) {
ZNode *zr = container_of(rhs, ZNode, tree);
return zless(lhs, zr->score, zr->name, zr->len);
}
// insert into the AVL tree
static void tree_add(ZSet *zset, ZNode *node) {
if (!zset->tree) {
zset->tree = &node->tree;
return;
}
AVLNode *cur = zset->tree;
while (true) {
AVLNode **from = zless(&node->tree, cur) ? &cur->left : &cur->right;
if (!*from) {
*from = &node->tree;
node->tree.parent = cur;
zset->tree = avl_fix(&node->tree);
break;
}
cur = *from;
}
}
// update the score of an existing node (AVL tree reinsertion)
static void zset_update(ZSet *zset, ZNode *node, double score) {
if (node->score == score) {
return;
}
zset->tree = avl_del(&node->tree);
node->score = score;
avl_init(&node->tree);
tree_add(zset, node);
}
// add a new (score, name) tuple, or update the score of the existing tuple
bool zset_add(ZSet *zset, const char *name, size_t len, double score) {
ZNode *node = zset_lookup(zset, name, len);
if (node) {
zset_update(zset, node, score);
return false;
} else {
node = znode_new(name, len, score);
hm_insert(&zset->hmap, &node->hmap);
tree_add(zset, node);
return true;
}
}
// a helper structure for the hashtable lookup
struct HKey {
HNode node;
const char *name = NULL;
size_t len = 0;
};
static bool hcmp(HNode *node, HNode *key) {
if (node->hcode != key->hcode) {
return false;
}
ZNode *znode = container_of(node, ZNode, hmap);
HKey *hkey = container_of(key, HKey, node);
if (znode->len != hkey->len) {
return false;
}
return 0 == memcmp(znode->name, hkey->name, znode->len);
}
// lookup by name
ZNode *zset_lookup(ZSet *zset, const char *name, size_t len) {
if (!zset->tree) {
return NULL;
}
HKey key;
key.node.hcode = str_hash((uint8_t *)name, len);
key.name = name;
key.len = len;
HNode *found = hm_lookup(&zset->hmap, &key.node, &hcmp);
if (!found) {
return NULL;
}
return container_of(found, ZNode, hmap);
}
// deletion by name
ZNode *zset_pop(ZSet *zset, const char *name, size_t len) {
if (!zset->tree) {
return NULL;
}
HKey key;
key.node.hcode = str_hash((uint8_t *)name, len);
key.name = name;
key.len = len;
HNode *found = hm_pop(&zset->hmap, &key.node, &hcmp);
if (!found) {
return NULL;
}
ZNode *node = container_of(found, ZNode, hmap);
zset->tree = avl_del(&node->tree);
return node;
}
// find the (score, name) tuple that is greater or equal to the argument,
// then offset relative to it.
ZNode *zset_query(
ZSet *zset, double score, const char *name, size_t len, int64_t offset)
{
AVLNode *found = NULL;
AVLNode *cur = zset->tree;
while (cur) {
if (zless(cur, score, name, len)) {
cur = cur->right;
} else {
found = cur; // candidate
cur = cur->left;
}
}
if (found) {
found = avl_offset(found, offset);
}
return found ? container_of(found, ZNode, tree) : NULL;
}
void znode_del(ZNode *node) {
free(node);
}
static void tree_dispose(AVLNode *node) {
if (!node) {
return;
}
tree_dispose(node->left);
tree_dispose(node->right);
znode_del(container_of(node, ZNode, tree));
}
// destroy the zset
void zset_dispose(ZSet *zset) {
tree_dispose(zset->tree);
hm_destroy(&zset->hmap);
}
See also:
codecrafters.io offers “Build Your Own X” courses in many programming languages.
Including Redis, Git, SQLite, Docker, and more.
Check it out
codecrafters.io offers “Build Your Own X” courses in many programming languages.
Including Redis, Git, SQLite, Docker, and more.