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//! Type definitions for 32-bit ELF binaries.

use crate::*;
use serde::{Deserialize, Serialize};

/// Symbol32 is a entry of symbol table section.
///
/// Symbol32 はシンボルテーブルセクションのエントリである．
/// ELF32で用いることを想定している．
///
///
/// Defaultトレイトを実装しているので，
/// `Default::default()` を呼び出すことで簡単にNULLシンボルを作成できる．
///
/// # Examples
///
/// ```
/// use elf_utilities::symbol::Symbol32;
/// let null_sym : Symbol32 = Default::default();
///
/// // Symbol32::new_null_symbol() のエイリアスでも作成可能．
/// let null_sym2 : Symbol32 = Symbol32::new_null_symbol();
///
/// assert_eq!(null_sym, null_sym2);
///
/// ```
///
/// ELFファイルを生成する用途でこのライブラリを使用できるように，
/// バイト列への変換もサポートしている．
///
/// # Examples
///
/// ```
/// use elf_utilities::symbol::Symbol32;
/// let null_sym : Symbol32 = Default::default();
///
/// // to_le_bytes() を利用してバイト列に変換できる．
/// let sym_bytes = null_sym.to_le_bytes();
/// assert_eq!(Symbol32::SIZE as usize, sym_bytes.len())
/// ```
#[derive(Default, Debug, Clone, Hash, PartialOrd, Ord, PartialEq, Eq, Serialize, Deserialize)]
#[repr(C)]
pub struct Symbol32 {
    /// Symbol name index.
    pub st_name: Elf32Word,

    /// Symbol's value.
    pub st_value: Elf32Addr,

    /// Symbol's size.
    pub st_size: Elf32Word,

    /// Information that includes [symbol binds and symbol types](https://docs.rs/elf-utilities/latest/elf_utilities/symbol/elf32/index.html#constants).
    pub st_info: u8,

    /// Symbol's visibility.
    /// See [symbol::VISIBILITY](https://docs.rs/elf-utilities/latest/elf_utilities/symbol/symbol_visibility/enum.VISIBILITY.html).
    pub st_other: u8,

    /// A section table index that includes the symbol.
    pub st_shndx: Elf32Section,

    /// option member for utilities.
    #[serde(skip_serializing)]
    #[serde(skip_deserializing)]
    pub symbol_name: String,
}

#[allow(dead_code)]
impl Symbol32 {
    /// SIZE provides Symbol32's size used by Shdr32.sh_entsize or else.
    pub const SIZE: usize = 0x10;
    pub fn new_null_symbol() -> Self {
        Default::default()
    }

    /// for utilities
    pub fn compare_by<P>(&self, predicate: P) -> bool
    where
        P: Fn(&Self) -> bool,
    {
        predicate(self)
    }

    pub fn get_type(&self) -> symbol::Type {
        symbol::Type::from(self.st_info & 0x0f)
    }

    pub fn get_bind(&self) -> symbol::Bind {
        symbol::Bind::from(self.st_info >> 4)
    }
    pub fn get_visibility(&self) -> symbol::Visibility {
        symbol::Visibility::from(self.st_other & 0x03)
    }

    /// Set symbol's information to Symbol32
    /// # Examples
    ///
    /// ```
    /// use elf_utilities::symbol;
    /// let mut null_sym = symbol::Symbol32::new_null_symbol();
    ///
    /// null_sym.set_info(symbol::Type::Func, symbol::Bind::Global);
    ///
    /// assert_eq!((1 << 4) | 2, null_sym.st_info);
    /// ```
    pub fn set_info(&mut self, sym_type: symbol::Type, bind: symbol::Bind) {
        self.st_info = bind.to_byte() << 4 | sym_type.to_byte();
    }

    /// Create Vec<u8> from Symbol32's each fields.
    ///
    /// # Examples
    ///
    /// ```
    /// use elf_utilities::symbol::Symbol32;
    /// let null_sym : Symbol32 = Default::default();
    ///
    /// assert_eq!([0].repeat(Symbol32::SIZE as usize), null_sym.to_le_bytes());
    /// ```
    pub fn to_le_bytes(&self) -> Vec<u8> {
        bincode::serialize(self).unwrap()
    }

    pub fn deserialize(buf: &[u8], start: usize) -> Result<Self, Box<dyn std::error::Error>> {
        // bincode::ErrorKindをトレイトオブジェクトとするため,この冗長な書き方が必要
        match bincode::deserialize(&buf[start..]) {
            Ok(header) => Ok(header),
            Err(e) => Err(e),
        }
    }
}