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Prune unused nodes from trie

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topjohnwu
2021-10-09 02:15:03 -07:00
parent 2fef98a5af
commit 7f18616cc0
7 changed files with 54 additions and 15 deletions
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48
native/jni/external/systemproperties/prop_area.cpp vendored
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@ -380,7 +380,40 @@ bool prop_area::add(const char* name, unsigned int namelen, const char* value,
return find_property(root_node(), name, namelen, value, valuelen, true);
}
bool prop_area::rm(const char *name) {
bool prop_area::prune_node(prop_bt * const node) {
bool is_leaf = true;
if (atomic_load_explicit(&node->children, memory_order_relaxed) != 0) {
if (prune_node(to_prop_bt(&node->children))) {
atomic_store_explicit(&node->children, 0, memory_order_release);
} else {
is_leaf = false;
}
}
if (atomic_load_explicit(&node->left, memory_order_relaxed) != 0) {
if (prune_node(to_prop_bt(&node->left))) {
atomic_store_explicit(&node->left, 0, memory_order_release);
} else {
is_leaf = false;
}
}
if (atomic_load_explicit(&node->right, memory_order_relaxed) != 0) {
if (prune_node(to_prop_bt(&node->right))) {
atomic_store_explicit(&node->right, 0, memory_order_release);
} else {
is_leaf = false;
}
}
if (is_leaf && atomic_load_explicit(&node->prop, memory_order_relaxed) == 0) {
// Wipe out this node
memset(node->name, 0, node->namelen);
memset(node, 0, sizeof(*node));
return true;
}
return false;
}
bool prop_area::rm(const char *name, bool trim_node) {
prop_bt *node = find_prop_bt(root_node(), name, false);
if (!node)
return false;
@ -392,19 +425,22 @@ bool prop_area::rm(const char *name) {
}
// De-reference the existing property ASAP
uint_least32_t new_offset = 0;
atomic_store_explicit(&node->prop, new_offset, memory_order_release);
atomic_store_explicit(&node->prop, 0, memory_order_release);
if (info) {
// Directly wipe out the old info
// Wipe out the old info
if (info->is_long()) {
char *value = const_cast<char*>(info->long_value());
auto len = strlen(value);
memset(value, 0, len);
memset(value, 0, strlen(value));
}
memset(info->name, 0, strlen(info->name));
memset(info, 0, sizeof(*info));
}
if (trim_node) {
prune_node(root_node());
}
return true;
}