Merge pull request #5 from jbalint/WIP

Many improvements

Author: ExcaliburZero

Cargo.lock

@@ -4,3 +4,10 @@ version = "0.1.0"
 authors = ["Christopher Wells <[email protected]>"]
 
 [dependencies]
+
+[dev-dependencies]
+insta = "1.3.0"
+
+[[bin]]
+name = "javap"
+path = "src/main.rs"

Cargo.toml

@@ -1,61 +1,87 @@
-use std::io;
+use std::{convert::TryInto, io};
 
 use bytecode::*;
-use ::{parsing, ConstantPoolIndex};
+
+use crate::ClassFile;
+use {parsing, ConstantPoolIndex};
 
 const EXCEPTION_ENTRY_LENGTH: usize = 8;
 
-#[derive(Debug)]
-#[derive(Eq)]
-#[derive(PartialEq)]
+#[derive(Debug, Eq, PartialEq, Clone)]
 pub struct Attribute {
     pub attribute_name_index: ConstantPoolIndex,
     pub info: Vec<u8>,
 }
 
-#[derive(Debug)]
-#[derive(PartialEq)]
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub struct AttributeSet {
+    pub attributes: Vec<Attribute>,
+}
+
+impl AttributeSet {
+    /// Find an attribute with the specified name
+    pub fn find_attribute<T: AsRef<str>>(
+        &self,
+        class_file: &ClassFile,
+        attribute_name: T,
+    ) -> Option<&Attribute> {
+        // we can index this more efficiently
+        self.attributes.iter().find(|attr| {
+            class_file.get_constant_utf8(attr.attribute_name_index) == attribute_name.as_ref()
+        })
+    }
+
+    pub fn get_signature(&self, class_file: &ClassFile) -> Option<String> {
+        self.find_attribute(class_file, "Signature").map(|attr| {
+            // why is this such a PITA
+            let boxed_slice = attr.info.clone().into_boxed_slice();
+            let boxed_array: Box<[u8; 2]> = match boxed_slice.try_into() {
+                Ok(ba) => ba,
+                Err(o) => panic!("Expected a Vec of length {} but it was {}", 2, o.len()),
+            };
+            let index = u16::from_be_bytes(*boxed_array);
+
+            class_file.get_constant_utf8(index as usize).to_string()
+        })
+    }
+}
+
+#[derive(Debug, PartialEq)]
 pub struct Code {
     pub max_stack: u16,
     pub max_locals: u16,
     pub code: Vec<(usize, Bytecode)>,
     pub exception_table: Vec<ExceptionTableEntry>,
-    pub attributes: Vec<Attribute>,
+    pub attributes: AttributeSet,
 }
 
 impl Code {
     pub fn from_bytes(bytes: &[u8]) -> io::Result<Code> {
         let max_stack = u16::from_be_bytes([bytes[0], bytes[1]]);
         let max_locals = u16::from_be_bytes([bytes[2], bytes[3]]);
 
-        let code_length = u32::from_be_bytes(
-            [bytes[4], bytes[5], bytes[6], bytes[7]]
-        ) as usize;
+        let code_length = u32::from_be_bytes([bytes[4], bytes[5], bytes[6], bytes[7]]) as usize;
 
         let code_start = 8;
         let code_end = code_start + code_length;
         let code_bytes = &bytes[code_start..code_end];
 
         let code = Bytecode::from_bytes(code_bytes);
 
-        let exception_table_length = u16::from_be_bytes(
-            [bytes[code_end], bytes[code_end + 1]]
-        ) as usize;
+        let exception_table_length =
+            u16::from_be_bytes([bytes[code_end], bytes[code_end + 1]]) as usize;
 
         let mut exception_table = Vec::with_capacity(exception_table_length);
         for i in 0..exception_table_length {
             let entry_start = (code_end + 2) + i * EXCEPTION_ENTRY_LENGTH;
             let entry_end = entry_start + EXCEPTION_ENTRY_LENGTH;
 
-            let entry = ExceptionTableEntry::from_bytes(
-                &bytes[entry_start..entry_end]
-            );
+            let entry = ExceptionTableEntry::from_bytes(&bytes[entry_start..entry_end]);
 
             exception_table.push(entry);
         }
 
-        let attributes_start = (code_end + 2) +
-            exception_table_length * EXCEPTION_ENTRY_LENGTH;
+        let attributes_start = (code_end + 2) + exception_table_length * EXCEPTION_ENTRY_LENGTH;
 
         let mut attribute_bytes = &bytes[attributes_start..];
         let attributes = parsing::read_attributes(&mut attribute_bytes)?;
@@ -70,8 +96,7 @@ impl Code {
     }
 }
 
-#[derive(Debug)]
-#[derive(PartialEq)]
+#[derive(Debug, PartialEq)]
 pub struct ExceptionTableEntry {
     pub start_pc: u16,
     pub end_pc: u16,