BTNode* BTree_search(const BTree tree, int key, int* pos)
{
if (!tree) {
return NULL;
}
int i = 0;
while (i < tree->keynum && key > tree->key[i]) {
++i;
}
// Find the key.
if (i < tree->keynum && tree->key[i] == key) {
if (pos) {
*pos = i;
}
return tree;
}
// tree 为叶子节点，找不到 key，查找失败返回
if (tree->isLeaf) {
return NULL;
}
// 节点内查找失败，但 tree->key[i - 1]< key < tree->key[i]，
// 下一个查找的结点应为 child[i]
// 从磁盘读取第 i 个孩子的数据
disk_read(&tree->child[i]);
// 递归地继续查找于树 tree->child[i]
return BTree_search(tree->child[i], key, pos);
}
//==================================================================
// 测试 B 树
//==================================================================
void test_BTree_search(BTree tree, int key)
{
int pos = -1;
BTNode* node = BTree_search(tree, key, &pos);
if (node) {
printf("在%s节点（包含 %d 个关键字）中找到关键字 %c，其索引为 %d\n",
node->isLeaf ? "叶子" : "非叶子",
node->keynum, key, pos);
}
else {
printf("在树中找不到关键字 %c\n", key);
}
}