proka-exec 0.4.3

//! # `proka-exec`
//!
//! [![Rust Nightly](https://img.shields.io/badge/rust-nightly-orange?style=flat-square&logo=rust)](https://www.rust-lang.org/)
//! [![License: GPLv3](https://img.shields.io/badge/License-GPLv3-yellow.svg?style=flat-square)](https://opensource.org/license/gpl-3.0)
//! [![GitHub Stars](https://img.shields.io/github/stars/RainSTR-Studio/proka-exec?style=flat-square)](https://github.com/RainSTR-Studio/proka-exec/stargazers)
//! [![GitHub Issues](https://img.shields.io/github/issues/RainSTR-Studio/proka-exec?style=flat-square)](https://github.com/RainSTR-Studio/proka-exec/issues)
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//! [![Documentation](https://img.shields.io/badge/docs-prokadoc-brightgreen?style=flat-square)](https://prokadoc.pages.dev/)
//!
//! Copyright (C) 2026 RainSTR Studio. Licensed under GNU GPLv3.
//!
//! ---
//!
//! ## Introduction
//! This crate provides the definitions of headers, section
//! entrys, and some utils to help you parse the executable
//! easily.
//!
//! ## Steps to use this crate
//! Before you parse it, you should do these steps:
//!
//! - Read the executable file content;
//! - Make this file's content to a slice (`&'static [u8]`)
//! - Use [`Parser`] to parse the executable.
//!
//! After this, you can do further operations through this parser by
//! calling its functions.
//!
//! ### Note
//! If you want to do minimal reading, you can just read the header and
//! section table, other content can be read later;
//!
//! Make sure you have read the header and each sections, and they are **NOT** optional!!!
//!
//! # LICENSE
//! This crate is under license [GPL-v3](https://github.com/RainSTR-Studio/proka-exec/blob/main/LICENSE),
//! and you must follow its rules.
//!
//! See [LICENSE](https://github.com/RainSTR-Studio/proka-exec/blob/main/LICENSE) file for more details.
//!
//! ## MSRV
//! This crate's MSRV is `1.85.0` stable.
#![no_std]

// Alloc features...
#[cfg(feature = "alloc")]
extern crate alloc;

pub mod header;
pub mod sections;
pub mod utils;

#[cfg(feature = "alloc")]
use alloc::{
    string::{String, ToString},
    vec::Vec,
};
use header::{ExecMode, Header};
use sections::{Section, SectionIter};
pub use utils::*;

/// The header size.
pub const HEADER_SIZE: usize = core::mem::size_of::<Header>();

/// The section entry size
pub const SECTION_SIZE: usize = core::mem::size_of::<Section>();

/// The parser of the proka executable.
///
/// # Usage
/// To use this parser, you must put an slice into the initializations.
///
/// If the content of the proka executable is in memory, the best way
/// is to use `core::slice::from_raw_parts`.
#[derive(Debug, Clone, Copy)]
pub struct Parser<'a> {
    buf: &'a [u8],
    header: Header,
    total_sections: u16,
}

impl<'a> Parser<'a> {
    /// Initialize the parser by passing a slice.
    ///
    /// This is the recommended way to initialize this parser, because it will
    /// help you do all checks and return error if something wrong, so you can
    /// leave everything about parsing to us :)
    ///
    /// # Note
    /// If this crate is used on the kernel-side, you must first map the memory
    /// that the slice points to before invoking this function.
    pub fn init(buf: &'a [u8]) -> Result<Self, Error> {
        let header_raw = &buf[0..HEADER_SIZE]; // Header length
        let header = unsafe { *(header_raw.as_ptr() as *const Header) };

        // Check: Validate is this correct executable
        if !header.validate() {
            return Err(Error::NotValidExecutable);
        }

        // Check: Is the buffer contains all sections
        let len = HEADER_SIZE + header.sections as usize * SECTION_SIZE;
        if buf.len() < len {
            return Err(Error::ExecutableCorrupted);
        }

        // SAFETY: Already check all staff and able to do initialization
        unsafe { Ok(Self::init_unchecked(buf)) }
    }

    /// Initialize the parser by passing a slice without checking.
    ///
    /// # Safety
    /// You must ensure these if you invoke this function:
    ///
    ///  - The slice's content is a valid proka executable (match the magic);
    ///  - The slice must contain the header and all section tables.
    ///
    /// # Note
    /// Use this function to initialize is **NOT** recommended, because it might
    /// cause some problems while parsing this header.
    pub unsafe fn init_unchecked(buf: &'a [u8]) -> Self {
        let header_raw = &buf[0..HEADER_SIZE];
        let header = unsafe { *(header_raw.as_ptr() as *const Header) };

        Self {
            buf,
            header,
            total_sections: header.sections,
        }
    }

    /// Do more validation after initialization.
    ///
    /// # Content
    /// This will validates:
    ///
    ///  - Is the header min >= max;
    ///  - Is each section's base correct;
    ///  - Is the section's length not zeroed;
    ///  - Is section base out of length;
    ///  - Is entry_off is over than section length.
    pub fn validate(&self) -> bool {
        // Check: Is header's min > max
        let minimal = self.header.min;
        let maximum = self.header.max;
        for (&min, &max) in minimal.iter().zip(maximum.iter()) {
            if min > max {
                return false;
            }
        }

        // Check: Is each section's base and length correct
        let min_base = HEADER_SIZE + self.header.sections as usize * SECTION_SIZE;
        for (index, section) in self.sections().enumerate() {
            let base_off = section.base as usize;
            let len = section.length as usize;
            let entry_sec = self.header.entry_sec as usize;

            if base_off < min_base
                || base_off + len > self.buf.len()
                || len == 0
                || !section.validate()
            {
                return false;
            }

            // Also at here, we'd like to check the entry_off
            // overflow or not.
            if index == entry_sec {
                let entry_off = self.header.entry_off as usize;
                if entry_off > len {
                    return false;
                }
            }
        }

        // All's fine :)
        true
    }

    /// Get the content from specified sections.
    ///
    /// # Arguments
    ///  - `secname`: The name of the section
    ///
    /// # Returns
    /// `Option<&'static [u8]>`: The content of this section, return `None` if this section not exist.
    pub fn get_section_content(&self, secname: &str) -> Option<&'a [u8]> {
        // Iterate all sections...
        for section in self.sections() {
            let name = section.name;
            if str_to_array(secname) == name {
                // Get its base and length
                let base = section.base as usize;
                let length = section.length as usize;
                let content = &self.buf[base..base + length];
                return Some(content);
            }
        }

        None
    }

    /// Get the header in this buffer.
    #[inline]
    pub fn header(&self) -> Header {
        self.header
    }

    /// Get each section table.
    pub fn sections(&self) -> SectionIter<'_> {
        SectionIter::new(self.buf, self.total_sections, 0)
    }
}

/// The builder of the proka executable.
#[derive(Debug, Clone)]
#[cfg(feature = "alloc")]
pub struct Builder<'a> {
    min: [u16; 3],
    max: [u16; 3],
    entry: (u32, usize), // (offset, index)
    author: String,
    name: String,
    mode: ExecMode,
    sections: Vec<InnerSections<'a>>,
}

#[cfg(feature = "alloc")]
impl Default for Builder<'_> {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(feature = "alloc")]
impl<'a> Builder<'a> {
    /// Create up a empty builder.
    pub fn new() -> Self {
        Self {
            min: [0; 3],
            max: [0; 3],
            entry: (0, 0),
            author: String::new(),
            name: String::new(),
            mode: ExecMode::UserApp,
            sections: Vec::new(),
        }
    }

    /// Set up the author.
    ///
    /// # Note
    /// If the author that you provide is longer than 32,
    /// it may truncated.
    pub fn set_author(&mut self, author: &str) {
        self.author = author.to_string();
    }

    /// Set up the program name.
    ///
    /// # Note
    /// If the author that you provide is longer than 32,
    /// it may truncated.
    pub fn set_name(&mut self, name: &str) {
        self.name = name.to_string();
    }

    /// Set the mode of this program.
    pub fn set_mode(&mut self, mode: ExecMode) {
        self.mode = mode;
    }

    /// Set the min version.
    pub fn set_min(&mut self, min: [u16; 3]) {
        self.min = min;
    }

    /// Set the max version.
    pub fn set_max(&mut self, max: [u16; 3]) {
        self.max = max;
    }

    /// Append a section and specify its name.
    ///
    /// # Arguments
    ///  - `data`: The data that you want to append;
    ///  - `name`: The section name;
    ///  - `is_loadable`: Assign is this loadable section or not;
    ///  - `is_execable`: Assign is this executable section or not;
    ///  - `entry`: The offset of the entry point, pass `None` if no entry point.
    ///
    /// # Errors
    /// This will return error once these happened:
    ///  - Provide an entry address which is unloadable or unexecable;
    ///
    /// # Note
    ///  - If you try to provide a name which is over than 16 bytes, it may truncated;
    ///  - If you provide the entry offset for multiple times, once you invoke `build()`, it will
    ///    use that latest set one.
    pub fn append(
        &mut self,
        data: &'a [u8],
        name: &str,
        is_loadable: bool,
        is_execable: bool,
        entry: Option<u32>,
    ) -> Result<(), Error> {
        // Check: Is entry is Some(...) within unloadable & unexecable
        if entry.is_some() && !(is_execable && is_loadable) {
            return Err(Error::ExecutableCorrupted);
        }

        let section = InnerSections {
            secinfo: Section {
                name: str_to_array(name),
                is_loadable,
                is_execable,
                base: 0,    // Will replace during building...
                length: data.len() as u32,
                _reserved: [0; 6],
            },
            data,
        };
        self.sections.push(section);

        // Set entry if Some(...)...
        if let Some(ent_offset) = entry {
            let sec_index = self.sections.len() - 1;
            self.entry = (ent_offset, sec_index);
        }
        Ok(())
    }

    /// Build the whole file to a valid exec format.
    ///
    /// Will return error if no section was appended.
    pub fn build(self) -> Result<Vec<u8>, Error> {
        // Check: Is section list empty
        if self.sections.is_empty() {
            return Err(Error::NoSections);
        }

        // Create up a data...
        let mut data: Vec<u8> = Vec::new();

        // Then create up a header and push into data...
        {
            let header = Header {
                min: self.min,
                max: self.max,
                entry_off: self.entry.0,
                entry_sec: self.entry.1 as u16,
                mode: self.mode,
                author: str_to_array(self.author.as_str()),
                name: str_to_array(self.name.as_str()),
                sections: self.sections.len() as u16,
                ..Default::default()
            }
            .to_array();
            data.extend_from_slice(&header);
        }

        // And each section info...
        let mut cnt = 0;
        for section in &self.sections {
            let mut secinfo = section.secinfo;

            // Update base...
            secinfo.base = (HEADER_SIZE + self.sections.len() * SECTION_SIZE + cnt) as u32;

            // Push...
            data.extend_from_slice(&secinfo.to_array());
            cnt += section.data.len();
        }

        // And each section's data...
        for section in &self.sections {
            data.extend_from_slice(section.data);
        }

        // Return
        Ok(data)
    }
}

/// Internal section form.
#[derive(Debug, Clone, Copy)]
struct InnerSections<'a> {
    pub secinfo: Section,
    pub data: &'a [u8],
}

/// The error type of parsing header.
#[repr(C)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Error {
    /// The executable is not valid
    ///
    /// Will appear if magic is not correct.
    NotValidExecutable,

    /// The section which is corrupted.
    ///
    /// Will appear if:  
    ///  - The buffer size is lower than specified length;
    ///  - Append an unexecable and unloadable section within an entry address (`Builder` only).
    ExecutableCorrupted,

    /// An unknown character in UTF-8 was found in
    /// parsing arrays
    ///
    /// May appear in converting slice to `&str`.
    UnknownCharacter,

    /// The argument which gives is too long.
    ///
    /// For example, if a field, which require at most 16 bytes, but you gave
    /// 17 bytes, it will return this error.
    ArgsTooLong,

    /// No sections in the current executable.
    ///
    /// Will appear if you try to build without any appending.
    NoSections,
}