| // Copyright (C) 2016 The Android Open Source Project |
| // |
| // 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. |
| |
| package annotate |
| |
| // Glossary: |
| // |
| // Snippet - this is static information collected from the semantic tree |
| // Location - this is a place which snippets will be associated with |
| // Nested - a snippet with hierarchical composition |
| // |
| // container - a Nested for container objects: map, array, slice, pointer |
| // entity - a Nested for field objects: class |
| // |
| // SymbolCategory - Global, Local, Parameter |
| // SymbolTable - maps names in a particular category to minions |
| // ScopedSymbolTable - allows scoping with variable hiding |
| // SymbolSpace - maps category to ScopedSymbolTable |
| |
| // Approach: |
| // |
| // Traverse the semantic tree of the API program. Generate snippets for |
| // expressions as required for the particular analysis. Let assignment |
| // statements and comparison expressions create information flow. When |
| // information flows from a snippet to a location, the snippet is attached |
| // to the location. Generate nested structures automatically as required |
| // for snippets to be attached at the appropriate location. |
| // |
| // When information flows from a location to a location the two locations |
| // become aliases and snippets are merged. Aliasing is achieved by picking |
| // a leader and a minion. All minions have a parent which is either a |
| // minion or a leader. A leader does not have a parent. All mutations |
| // operations on a minion are forwarded to its leader. Whenever the leader |
| // of a minion is computed, the path to the leader is shortened for all |
| // minions in the chain. This approach called union-find gives complexity |
| // of O(A^-1(n,n)) ~ the inverse Ackermann function, which is typically |
| // regarded as being as good as constant time: |
| // |
| // https://en.wikipedia.org/wiki/Disjoint-set_data_structure |
