Merge pull request #37 from emilycares/feature/LocalVariableTable

Implement LocalVariableTable

Author: Palmr

README.md

@@ -108,6 +108,6 @@ fn main() {
       - [x] SourceFile
       - [ ] SourceDebugExtension
       - [ ] LineNumberTable
-      - [ ] LocalVariableTable
+      - [x] LocalVariableTable
       - [ ] LocalVariableTypeTable
       - [ ] Deprecated

java-assets/compile.sh

@@ -26,6 +26,7 @@ javac -d java-assets/compiled-classes/ java-assets/src/Instructions.java
 javac -d java-assets/compiled-classes/ java-assets/src/UnicodeStrings.java
 javac -d java-assets/compiled-classes/ java-assets/src/DeprecatedAnnotation.java
 
+javac -g -d java-assets/compiled-classes/ java-assets/src/LocalVariableTable.java
 javac -d java-assets/compiled-classes/ java-assets/src/HelloWorld.java
 printf '\xde\xad\xbe\xef' > java-assets/compiled-classes/malformed.class
 tail -c+5 java-assets/compiled-classes/HelloWorld.class >> java-assets/compiled-classes/malformed.class

java-assets/compiled-classes/LocalVariableTable.class

@@ -0,0 +1,8 @@
+import java.util.*;
+public class LocalVariableTable {
+  public void hereIsCode() {
+    HashMap<Integer, String> a = new HashMap<>();
+    a.put(1, "");
+    int number = 0;
+  }
+}

java-assets/src/LocalVariableTable.java

@@ -5,3 +5,4 @@ pub use self::types::*;
 
 pub use self::parser::code_parser;
 pub use self::parser::instruction_parser;
+pub use self::parser::local_variable_table_parser;

src/code_attribute/mod.rs

@@ -2,12 +2,16 @@ use crate::code_attribute::types::Instruction;
 use nom::{
     bytes::complete::{tag, take},
     combinator::{complete, fail, map, success},
+    error::Error,
     multi::{count, many0},
     number::complete::{be_i16, be_i32, be_i8, be_u16, be_u32, be_u8},
     sequence::{pair, preceded, tuple},
-    IResult, Offset,
+    Err as BaseErr, IResult, Offset,
 };
 
+use super::{LocalVariableTableAttribute, LocalVariableTableItem};
+type Err<E> = BaseErr<Error<E>>;
+
 fn offset<'a>(remaining: &'a [u8], input: &[u8]) -> IResult<&'a [u8], usize> {
     Ok((remaining, input.offset(remaining)))
 }
@@ -290,3 +294,40 @@ pub fn instruction_parser(input: &[u8], address: usize) -> IResult<&[u8], Instru
     };
     Ok((input, instruction))
 }
+
+pub fn local_variable_table_parser(
+    input: &[u8],
+) -> Result<(&[u8], LocalVariableTableAttribute), Err<&[u8]>> {
+    let (input, local_variable_table_length) = be_u16(input)?;
+    let (input, items) = count(
+        variable_table_item_parser,
+        local_variable_table_length as usize,
+    )(input)?;
+    Ok((
+        input,
+        LocalVariableTableAttribute {
+            local_variable_table_length,
+            items,
+        },
+    ))
+}
+
+pub fn variable_table_item_parser(
+    input: &[u8],
+) -> Result<(&[u8], LocalVariableTableItem), Err<&[u8]>> {
+    let (input, start_pc) = be_u16(input)?;
+    let (input, length) = be_u16(input)?;
+    let (input, name_index) = be_u16(input)?;
+    let (input, descriptor_index) = be_u16(input)?;
+    let (input, index) = be_u16(input)?;
+    Ok((
+        input,
+        LocalVariableTableItem {
+            start_pc,
+            length,
+            name_index,
+            descriptor_index,
+            index,
+        },
+    ))
+}

src/code_attribute/parser.rs

@@ -234,3 +234,18 @@ pub enum Instruction {
         offsets: Vec<i32>,
     },
 }
+
+#[derive(Clone, Debug)]
+pub struct LocalVariableTableAttribute {
+    pub local_variable_table_length: u16,
+    pub items: Vec<LocalVariableTableItem>,
+}
+
+#[derive(Clone, Debug)]
+pub struct LocalVariableTableItem {
+    pub start_pc: u16,
+    pub length: u16,
+    pub name_index: u16,
+    pub descriptor_index: u16,
+    pub index: u16,
+}

src/code_attribute/types.rs

@@ -2,7 +2,9 @@ extern crate classfile_parser;
 
 use classfile_parser::attribute_info::{code_attribute_parser, method_parameters_attribute_parser};
 use classfile_parser::class_parser;
-use classfile_parser::code_attribute::{code_parser, instruction_parser, Instruction};
+use classfile_parser::code_attribute::{
+    code_parser, instruction_parser, Instruction, LocalVariableTableAttribute,
+};
 use classfile_parser::method_info::MethodAccessFlags;
 
 #[test]
@@ -115,3 +117,59 @@ fn method_parameters() {
         Some("b".to_string())
     );
 }
+
+#[test]
+fn local_variable_table() {
+    // The class was not compiled with "javac -g"
+    let class_bytes = include_bytes!("../java-assets/compiled-classes/LocalVariableTable.class");
+    let (_, class) = class_parser(class_bytes).unwrap();
+    let method_info = &class.methods.iter().last().unwrap();
+
+    let code_attribute = method_info
+        .attributes
+        .iter()
+        .find_map(|attribute_info| {
+            match lookup_string(&class, attribute_info.attribute_name_index)?.as_str() {
+                "Code" => {
+                    classfile_parser::attribute_info::code_attribute_parser(&attribute_info.info)
+                        .ok()
+                }
+                _ => None,
+            }
+        })
+        .map(|i| i.1)
+        .unwrap();
+
+    let local_variable_table_attribute: LocalVariableTableAttribute = code_attribute
+        .attributes
+        .iter()
+        .find_map(|attribute_info| {
+            match lookup_string(&class, attribute_info.attribute_name_index)?.as_str() {
+                "LocalVariableTable" => {
+                    classfile_parser::code_attribute::local_variable_table_parser(
+                        &attribute_info.info,
+                    )
+                    .ok()
+                }
+                _ => None,
+            }
+        })
+        .map(|a| a.1)
+        .unwrap();
+
+    let types: Vec<String> = local_variable_table_attribute
+        .items
+        .iter()
+        .filter_map(|i| lookup_string(&class, i.descriptor_index))
+        .collect();
+
+    // All used types in method code block of last method
+    assert_eq!(
+        types,
+        vec![
+            "LLocalVariableTable;".to_string(),
+            "Ljava/util/HashMap;".to_string(),
+            "I".to_string()
+        ]
+    );
+}