//! # Fast ELF editing library.
//!
//! ELF is the main format of library and executable files on most
//! Unix systems, with the notable exceptions of Apple's various
//! platforms.
//!
//! This library does the same as the existing `patchelf` tool, but
//! with a time and space complexity that do not depend on the file
//! size.
//!
//! # Use of CStr in this crate
//!
//! This library tries to avoid doing things more than once. In
//! particular, ELF files comprise many strings represented as a Rust
//! `CStr`, i.e. a string ended with a 0 byte. We usually convert
//! these to the more efficient `&[u8]` type as soon as
//! possible. Moreover, we keep the zero byte itself in the `&[u8]`
//! while doing so in order to make our code smaller (and avoid some
//! edge cases) when writing the strings.
//!
//! This has the advantage of speed, but the inconvenience that you
//! have to provide the 0 byte in your slices when interacting with
//! this crate. See the example below for examples.
//!
//! # Example
//!
//! In this example, we modify the binary from the GNU Hello package
//! from Ubuntu "Noble Numbat" (24.04). Note that this makes our tests
//! GPL 3, since the binary of GNU Hello is included in the test
//! binary.
//!
//! ```
//! use std::io::Write;
//! use elfedit::*;
//! let mut p = tempfile::tempfile().unwrap();
//! p.write_all(include_bytes!("hello")).unwrap();
//! let mut elf = Elf::open(&p).unwrap();
//!
//! let new_interp = b"/nix/store/maxa3xhmxggrc5v2vc0c3pjb79hjlkp9-glibc-2.40-66/lib/ld-linux-x86-64.so.2\0";
//!
//! let new_needed = b"ma.bibliotheque.so.19\0";
//! let new_needed2 = b"ma.bibliotheque.so.24\0";
//! let runpath = b"a:b:c\0";
//! elf.set_runpath(runpath)
//!     .set_interpreter(new_interp)
//!     .add_needed(new_needed).unwrap()
//!     .add_needed(new_needed2).unwrap();
//! elf.update().unwrap();
//!
//! let elf = Elf::open(&p).unwrap();
//! let p = elf.parse().unwrap();
//! assert_eq!(p.interpreter().unwrap().to_bytes_with_nul(), new_interp);
//! assert_eq!(p.runpath().unwrap().unwrap().to_bytes_with_nul(), runpath);
//! let needed: Result<Vec<_>, _> = p.needed().map(|x| x.map(|x| x.to_bytes_with_nul())).collect();
//! let needed = needed.unwrap();
//! assert_eq!(
//!     needed,
//!     &[
//!         &b"libc.so.6\0"[..],
//!         &b"ma.bibliotheque.so.19\0"[..],
//!         &b"ma.bibliotheque.so.24\0"[..]
//!     ]
//! );
//! ```
use std::collections::HashMap;
use std::ffi::CStr;
use thiserror::*;
#[derive(Debug, Error)]
pub enum Error {
    #[error(transparent)]
    IO(#[from] std::io::Error),
    #[error(transparent)]
    FromBytesWithNul(#[from] std::ffi::FromBytesWithNulError),
    #[error(transparent)]
    FromBytesUntilNul(#[from] std::ffi::FromBytesUntilNulError),
    #[error("Section not found: {name:?}")]
    SectionNotFound { name: Vec<u8> },
}
#[derive(Debug, Copy, Clone, PartialEq)]
struct Bits(u8);
impl Bits {
    const B32: Self = Bits(1);
    const B64: Self = Bits(2);
}
#[derive(Debug, Copy, Clone, PartialEq)]
struct Endianness(u8);
impl Endianness {
    const LITTLE: Self = Endianness(1);
    const BIG: Self = Endianness(2);
}
#[allow(dead_code)]
#[derive(Debug, Copy, Clone)]
struct ABI(u8);
fn align_next(x: usize, mul: usize) -> usize {
    (x + mul - 1) & !(mul - 1)
}
#[allow(dead_code)]
impl ABI {
    const SYSTEM_V: Self = ABI(0);
    const HPUX: Self = ABI(1);
    const NET_BSD: Self = ABI(2);
    const LINUX: Self = ABI(3);
    const GNU_HURD: Self = ABI(4);
    const SOLARIS: Self = ABI(6);
    const AIX: Self = ABI(7);
    const IRIX: Self = ABI(8);
    const FREE_BSD: Self = ABI(9);
    const TRU64: Self = ABI(10);
    const NOVELL_MODESTO: Self = ABI(11);
    const OPEN_BSD: Self = ABI(12);
    const OPEN_VMS: Self = ABI(13);
    const NON_STOP_KERNEL: Self = ABI(14);
    const AROS: Self = ABI(15);
    const FENIX_OS: Self = ABI(16);
    const NUXI_CLOUD_ABI: Self = ABI(17);
    const OPEN_VOS: Self = ABI(18);
}
#[allow(dead_code)]
#[derive(Debug, Copy, Clone)]
struct Type(u8);
#[allow(dead_code)]
impl Type {
    const NONE: Self = Type(0);
    const REPOSITIONABLE: Self = Type(1);
    const EXECUTABLE: Self = Type(2);
    const SHARED_OBJECT: Self = Type(3);
    const CORE: Self = Type(4);
}
#[derive(Debug, Copy, Clone)]
#[repr(C)]
struct Id {
    magic: [u8; 4],
    class: Bits,
    data: Endianness,
    version: u8,
    osabi: ABI,
    abi_version: u8,
    padding: [u8; 7],
}
#[derive(Debug, Copy, Clone)]
struct Endian<U>(U);
trait EndianT: Sized {
    fn endian(e: Endian<Self>, id: Endianness) -> Self;
}
impl EndianT for u16 {
    fn endian(e: Endian<Self>, id: Endianness) -> Self {
        if id == Endianness::LITTLE {
            u16::from_le(e.0)
        } else if id == Endianness::BIG {
            u16::from_be(e.0)
        } else {
            panic!()
        }
    }
}
impl EndianT for u32 {
    fn endian(e: Endian<Self>, id: Endianness) -> Self {
        if id == Endianness::LITTLE {
            u32::from_le(e.0)
        } else if id == Endianness::BIG {
            u32::from_be(e.0)
        } else {
            panic!()
        }
    }
}
impl EndianT for u64 {
    fn endian(e: Endian<Self>, id: Endianness) -> Self {
        if id == Endianness::LITTLE {
            u64::from_le(e.0)
        } else if id == Endianness::BIG {
            u64::from_be(e.0)
        } else {
            panic!()
        }
    }
}
impl EndianT for Sht {
    fn endian(e: Endian<Self>, id: Endianness) -> Sht {
        if id == Endianness::LITTLE {
            Sht(u32::from_le(e.0 .0))
        } else if id == Endianness::BIG {
            Sht(u32::from_be(e.0 .0))
        } else {
            panic!()
        }
    }
}
impl Endian<u32> {
    fn from(id: Endianness, u: u32) -> Self {
        if id == Endianness::LITTLE {
            Endian(u.to_le())
        } else if id == Endianness::BIG {
            Endian(u.to_be())
        } else {
            panic!()
        }
    }
}
impl Endian<u64> {
    fn from(id: Endianness, u: u64) -> Self {
        if id == Endianness::LITTLE {
            Endian(u.to_le())
        } else if id == Endianness::BIG {
            Endian(u.to_be())
        } else {
            panic!()
        }
    }
}
#[derive(Debug, Copy, Clone)]
#[repr(C)]
struct Header<Offset> {
    type_: Endian<u16>,
    machine: Endian<u16>,
    version: Endian<u32>,
    entry: Endian<Offset>,
    phoff: Endian<Offset>,
    shoff: Endian<Offset>,
    flags: Endian<u32>,
    ehsize: Endian<u16>,
    phentsize: Endian<u16>,
    phnum: Endian<u16>,
    shentsize: Endian<u16>,
    shnum: Endian<u16>,
    shstrndx: Endian<u16>,
}
#[derive(Debug, Copy, Clone)]
#[repr(C)]
struct SectionHeader<Offset> {
    name: Endian<u32>,
    type_: Endian<Sht>,
    flags: Endian<Offset>,
    addr: Endian<Offset>,
    offset: Endian<Offset>,
    size: Endian<Offset>,
    link: Endian<u32>,
    info: Endian<u32>,
    addralign: Endian<Offset>,
    entsize: Endian<Offset>,
}
#[derive(Debug)]
enum SectionHeader_<'a> {
    B32(&'a SectionHeader<u32>),
    B64(&'a SectionHeader<u64>),
}
#[derive(Debug)]
enum SectionHeaderMut_<'a> {
    B32(&'a mut SectionHeader<u32>),
    B64(&'a mut SectionHeader<u64>),
}
#[derive(Debug)]
enum ProgramHeaderMut_<'a> {
    B32(&'a mut ProgramHeader<u32>),
    B64(&'a mut ProgramHeader<u64>),
}
impl<'a> SectionHeaderMut_<'a> {
    fn set_size(&mut self, h: Endianness, u: usize) {
        match self {
            SectionHeaderMut_::B32(s) => s.size = <Endian<u32>>::from(h, u as u32),
            SectionHeaderMut_::B64(s) => s.size = <Endian<u64>>::from(h, u as u64),
        }
    }
    fn set_offset(&mut self, h: Endianness, u: usize) {
        match self {
            SectionHeaderMut_::B32(s) => s.offset = <Endian<u32>>::from(h, u as u32),
            SectionHeaderMut_::B64(s) => s.offset = <Endian<u64>>::from(h, u as u64),
        }
    }
}
impl<'a> ProgramHeaderMut_<'a> {
    fn offset(&self, h: Endianness) -> u64 {
        match self {
            ProgramHeaderMut_::B32(s) => EndianT::endian(s.offset, h) as u64,
            ProgramHeaderMut_::B64(s) => EndianT::endian(s.offset, h),
        }
    }
    fn set_filesz(&mut self, h: Endianness, u: usize) {
        match self {
            ProgramHeaderMut_::B32(s) => s.filesz = <Endian<u32>>::from(h, u as u32),
            ProgramHeaderMut_::B64(s) => s.filesz = <Endian<u64>>::from(h, u as u64),
        }
    }
    fn set_memsz(&mut self, h: Endianness, u: usize) {
        match self {
            ProgramHeaderMut_::B32(s) => s.memsz = <Endian<u32>>::from(h, u as u32),
            ProgramHeaderMut_::B64(s) => s.memsz = <Endian<u64>>::from(h, u as u64),
        }
    }
    fn set_offset(&mut self, h: Endianness, u: usize) {
        match self {
            ProgramHeaderMut_::B32(s) => s.offset = <Endian<u32>>::from(h, u as u32),
            ProgramHeaderMut_::B64(s) => s.offset = <Endian<u64>>::from(h, u as u64),
        }
    }
}
impl<'a> SectionHeader_<'a> {
    fn offset(&self, h: Endianness) -> u64 {
        match self {
            SectionHeader_::B32(s) => EndianT::endian(s.offset, h) as u64,
            SectionHeader_::B64(s) => EndianT::endian(s.offset, h),
        }
    }
    fn size(&self, h: Endianness) -> u64 {
        match self {
            SectionHeader_::B32(s) => EndianT::endian(s.size, h) as u64,
            SectionHeader_::B64(s) => EndianT::endian(s.size, h),
        }
    }
    fn name(&self, id: Endianness) -> u32 {
        match self {
            SectionHeader_::B32(h) => EndianT::endian(h.name, id),
            SectionHeader_::B64(h) => EndianT::endian(h.name, id),
        }
    }
    fn type_(&self, id: Endianness) -> Sht {
        match self {
            SectionHeader_::B32(h) => EndianT::endian(h.type_, id),
            SectionHeader_::B64(h) => EndianT::endian(h.type_, id),
        }
    }
}
#[derive(Debug, Copy, Clone, PartialEq)]
struct Pht(u32);
#[allow(dead_code)]
impl Pht {
    const NULL: Self = Pht(0);
    const LOAD: Self = Pht(1);
    const DYNAMIC: Self = Pht(2);
    const INTERP: Self = Pht(3);
    const NOTE: Self = Pht(4);
    const SHLIB: Self = Pht(5);
    const PHDR: Self = Pht(6);
    const TLS: Self = Pht(7);
    const LOOS: Self = Pht(0x60000000);
    const HIOS: Self = Pht(0x6fffffff);
    const LOPROC: Self = Pht(0x70000000);
    const HIPROC: Self = Pht(0x7fffffff);
}
#[derive(Debug, Copy, Clone)]
#[repr(C)]
struct ProgramHeader<Offset: Flags> {
    type_: Endian<Pht>,
    flags64: Endian<Offset::F64>,
    offset: Endian<Offset>,
    vaddr: Endian<Offset>,
    paddr: Endian<Offset>,
    filesz: Endian<Offset>,
    memsz: Endian<Offset>,
    flags32: Endian<Offset::F32>,
    align: Endian<Offset>,
}
/// An open ELF file.
///
/// Most operations on this type follow a "builder pattern", meaning
/// that they don't actually update the underlying file until the
/// `.update()` method is called.
pub struct Elf<'a> {
    map: memmap::MmapMut,
    f: Option<&'a std::fs::File>,
    new_needed: Option<Vec<Vec<u8>>>,
    new_runpath: Vec<u8>,
    new_interp: Vec<u8>,
}
impl<'f> Elf<'f> {
    /// Create a builder around the provided file. Maps `file` in memory.
    pub fn open(file: &'f std::fs::File) -> Result<Self, std::io::Error> {
        let map = unsafe { memmap::MmapOptions::new().map_mut(&file).unwrap() };
        Ok(Elf {
            map,
            f: Some(file),
            new_needed: None,
            new_runpath: Vec::new(),
            new_interp: Vec::new(),
        })
    }
    fn section<'a>(&'a self, n: usize) -> SectionHeader_<'a> {
        let h = self.header();
        let id = self.id().data;
        assert!(n < h.shnum(id) as usize);
        let ph = h.shoff(id) as usize + n * h.shentsize(id) as usize;
        match h {
            Header_::B32(_) => {
                assert!(ph + std::mem::size_of::<SectionHeader<u32>>() <= self.map.len());
                assert_eq!(ph % std::mem::align_of::<SectionHeader<u32>>(), 0);
                SectionHeader_::B32(unsafe {
                    &*((self.map.as_ptr()).add(ph) as *const u8 as *const SectionHeader<u32>)
                })
            }
            Header_::B64(_) => {
                assert!(ph + std::mem::size_of::<SectionHeader<u64>>() <= self.map.len());
                assert_eq!(ph % std::mem::align_of::<SectionHeader<u64>>(), 0);
                SectionHeader_::B64(unsafe {
                    &*((self.map.as_ptr()).add(ph) as *const u8 as *const SectionHeader<u64>)
                })
            }
        }
    }
    fn sections<U>(&self) -> &[SectionHeader<U>] {
        let h = self.header();
        let id = self.id().data;
        if self.id().class == Bits::B64 {
            assert_eq!(std::mem::size_of::<U>(), 8)
        } else {
            assert_eq!(std::mem::size_of::<U>(), 4)
        }
        let ph = h.shoff(id) as usize;
        let shnum = h.shnum(id) as usize;
        assert!(ph + std::mem::size_of::<SectionHeader<U>>() <= self.map.len());
        assert_eq!(ph % std::mem::align_of::<SectionHeader<U>>(), 0);
        unsafe {
            std::slice::from_raw_parts(
                self.map.as_ptr().add(ph) as *const u8 as *const SectionHeader<U>,
                shnum,
            )
        }
    }
    fn program_mut<'a>(&'a mut self, n: usize) -> ProgramHeaderMut_<'a> {
        let h = self.header();
        let id = self.id().data;
        assert!(n < h.phnum(id) as usize);
        let ph = h.phoff(id) as usize + n * h.phentsize(id) as usize;
        match h {
            Header_::B32(_) => {
                assert!(ph + std::mem::size_of::<ProgramHeader<u32>>() <= self.map.len());
                assert_eq!(ph % std::mem::align_of::<ProgramHeader<u32>>(), 0);
                ProgramHeaderMut_::B32(unsafe {
                    &mut *((self.map.as_mut_ptr()).add(ph) as *mut u8 as *mut ProgramHeader<u32>)
                })
            }
            Header_::B64(_) => {
                assert!(ph + std::mem::size_of::<ProgramHeader<u64>>() <= self.map.len());
                assert_eq!(ph % std::mem::align_of::<ProgramHeader<u32>>(), 0);
                ProgramHeaderMut_::B64(unsafe {
                    &mut *((self.map.as_mut_ptr()).add(ph) as *mut u8 as *mut ProgramHeader<u64>)
                })
            }
        }
    }
    fn section_mut<'a>(&'a mut self, n: usize) -> SectionHeaderMut_<'a> {
        let h = self.header();
        let id = self.id().data;
        assert!(n < h.shnum(id) as usize);
        let ph = h.shoff(id) as usize + n * h.shentsize(id) as usize;
        match h {
            Header_::B32(_) => {
                assert!(ph + std::mem::size_of::<SectionHeader<u32>>() <= self.map.len());
                assert_eq!(ph % std::mem::align_of::<SectionHeader<u32>>(), 0);
                SectionHeaderMut_::B32(unsafe {
                    &mut *((self.map.as_mut_ptr()).add(ph) as *mut u8 as *mut SectionHeader<u32>)
                })
            }
            Header_::B64(_) => {
                assert!(ph + std::mem::size_of::<SectionHeader<u64>>() <= self.map.len());
                assert_eq!(ph % std::mem::align_of::<SectionHeader<u64>>(), 0);
                SectionHeaderMut_::B64(unsafe {
                    &mut *((self.map.as_mut_ptr()).add(ph) as *mut u8 as *mut SectionHeader<u64>)
                })
            }
        }
    }
    fn names<'a>(&'a self, id: Endianness, header: &Header_) -> Names<'a> {
        let s = self.section(header.shstrndx(id) as usize);
        let offset = s.offset(id) as usize;
        let size = s.size(id) as usize;
        Names(&self.map[offset..offset + size])
    }
    fn id(&self) -> &Id {
        assert!(self.map.len() >= std::mem::size_of::<Header<u32>>());
        unsafe { &*(self.map.as_ptr() as *const u8 as *const Id) }
    }
    fn header(&self) -> Header_ {
        let id = self.id();
        // The aligment is guaranteed here by design of the
        // ELF file. The size isn't, however.
        match id.class {
            Bits::B32 => {
                assert!(
                    std::mem::size_of::<Id>() + std::mem::size_of::<Header<u32>>()
                        <= self.map.len()
                );
                let header_: &Header<u32> = unsafe {
                    &*(self.map.as_ptr().add(std::mem::size_of::<Id>()) as *const u8
                        as *const Header<u32>)
                };
                Header_::B32(header_)
            }
            Bits::B64 => {
                assert!(
                    std::mem::size_of::<Id>() + std::mem::size_of::<Header<u64>>()
                        <= self.map.len()
                );
                let header_: &Header<u64> = unsafe {
                    &*(self.map.as_ptr().add(std::mem::size_of::<Id>()) as *const u8
                        as *const Header<u64>)
                };
                Header_::B64(header_)
            }
            _ => panic!(),
        }
    }
    fn header_mut(&mut self) -> HeaderMut_ {
        let id = self.id();
        match id.class {
            Bits::B32 => {
                assert!(
                    std::mem::size_of::<Id>() + std::mem::size_of::<Header<u32>>()
                        <= self.map.len()
                );
                let header_: &mut Header<u32> = unsafe {
                    &mut *(self.map.as_mut_ptr().add(std::mem::size_of::<Id>()) as *mut u8
                        as *mut Header<u32>)
                };
                HeaderMut_::B32(header_)
            }
            Bits::B64 => {
                assert!(
                    std::mem::size_of::<Id>() + std::mem::size_of::<Header<u64>>()
                        <= self.map.len()
                );
                let header_: &mut Header<u64> = unsafe {
                    &mut *(self.map.as_mut_ptr().add(std::mem::size_of::<Id>()) as *mut u8
                        as *mut Header<u64>)
                };
                HeaderMut_::B64(header_)
            }
            _ => panic!(),
        }
    }
    /// Paress the sections relevant for linking (.interp, .dynstr, .dynamic).
    ///
    /// The sections are stored in an unordered array in the ELF file,
    /// so this avoids going through the array for each query.
    pub fn parse(&self) -> Result<Parsed, Error> {
        let id = self.id();
        let header = self.header();
        let names = self.names(id.data, &header);
        let mut dynstr = Names(&[][..]);
        let mut dynamic = Dynamic::B32(&[]);
        let mut interp = &[][..];
        for i in 0..header.shnum(id.data) {
            let s = self.section(i as usize);
            let name = names.name(s.name(id.data) as usize)?;
            if name.to_bytes() == b".interp" {
                let offset = s.offset(id.data) as usize;
                let size = s.size(id.data) as usize;
                interp = &self.map[offset..offset + size];
            }
            if name.to_bytes() == b".dynstr" {
                let offset = s.offset(id.data) as usize;
                let size = s.size(id.data) as usize;
                dynstr = Names(&self.map[offset..offset + size]);
            }
            if s.type_(id.data) == Sht::DYNAMIC {
                let offset = s.offset(id.data) as usize;
                let size = s.size(id.data) as usize;
                dynamic = match id.class {
                    Bits::B32 => {
                        assert_eq!(offset % std::mem::align_of::<Elf32Dyn>(), 0);
                        assert!(offset + size <= self.map.len());
                        Dynamic::B32(unsafe {
                        std::slice::from_raw_parts(
                            self.map.as_ptr().add(offset) as *const u8 as *const Elf32Dyn,
                            size / std::mem::size_of::<Elf32Dyn>(),
                        )
                        })
                    },
                    Bits::B64 => {Dynamic::B64(unsafe {
                        assert_eq!(offset % std::mem::align_of::<Elf64Dyn>(), 0);
                        assert!(offset + size <= self.map.len());
                        std::slice::from_raw_parts(
                            self.map.as_ptr().add(offset) as *const u8 as *const Elf64Dyn,
                            size / std::mem::size_of::<Elf64Dyn>(),
                        )
                    })
                    },
                    _ => panic!(),
                };
            }
        }
        Ok(Parsed {
            dynstr,
            dynamic,
            interp,
        })
    }
    fn find_section<U>(&self, name: &[u8]) -> Result<Option<usize>, Error> {
        let id = self.id().data;
        let header = self.header();
        let names = self.names(id, &header);
        for (i, sec) in self.sections::<U>().into_iter().enumerate() {
            if names
                .name(EndianT::endian(sec.name, id) as usize)?
                .to_bytes()
                == name
            {
                return Ok(Some(i));
            }
        }
        Ok(None)
    }
    fn find_next_off<U: EndianT + Copy + Into<u64>>(&self, off: u64) -> u64 {
        let id = self.id().data;
        let header = self.header();
        let mut next_off = header.shoff(id);
        for sec in self.sections::<U>() {
            let s: u64 = EndianT::endian(sec.offset, id).into();
            if s > off && s < next_off {
                next_off = s;
            }
        }
        next_off
    }
    /// Updates a section. This is a low-level function and doesn't
    /// normally need to be called.
    pub fn update_section(&mut self, name: &[u8], new: &[u8]) -> Result<usize, Error> {
        let id = self.id().data;
        let class = self.id().class;
        let interp_i = if class == Bits::B64 {
            self.find_section::<u64>(name)?
        } else {
            self.find_section::<u64>(name)?
        };
        let Some(interp_i) = interp_i else {
            return Err(Error::SectionNotFound {
                name: name.to_vec(),
            });
        };
        let off = self.section(interp_i as usize).offset(id);
        let next_off = if class == Bits::B64 {
            self.find_next_off::<u64>(off) as u64
        } else {
            self.find_next_off::<u32>(off) as u64
        };
        let new_len = new.len();
        if new_len <= (next_off - off) as usize {
            // Easy
            let off = self.section(interp_i as usize).offset(id);
            assert!(off as usize + new.len() <= self.map.len());
            unsafe {
                self.map
                    .as_mut_ptr()
                    .add(off as usize)
                    .write_bytes(0, (next_off - off) as usize);
                std::ptr::copy(
                    new.as_ptr() as *const i8,
                    self.map.as_mut_ptr().add(off as usize) as *mut i8,
                    new.len(),
                );
            }
            self.section_mut(interp_i as usize).set_size(id, new_len);
            Ok(0)
        } else {
            Ok(self.update_section_allocate(id, new, interp_i, off as u64))
        }
    }
    fn update_section_allocate(
        &mut self,
        id: Endianness,
        new: &[u8],
        interp_i: usize,
        off: u64,
    ) -> usize {
        let new_len = new.len();
        let h = self.header();
        let shnum = h.shnum(id);
        let class = self.id().class;
        // First find a large enough deleted section = gap
        // between sections.
        let mut sections: Vec<_> = if class == Bits::B32 {
            self.sections::<u32>()
                .iter()
                .map(|s| {
                    (
                        EndianT::endian(s.offset, id) as usize,
                        EndianT::endian(s.size, id) as usize,
                    )
                })
                .collect()
        } else {
            self.sections::<u64>()
                .iter()
                .map(|s| {
                    (
                        EndianT::endian(s.offset, id) as usize,
                        EndianT::endian(s.size, id) as usize,
                    )
                })
                .collect()
        };
        sections.sort();
        let extra_size = new_len;
        let extra_size = match class {
            Bits::B32 => (extra_size + 3) & !3,
            Bits::B64 => (extra_size + 7) & !7,
            _ => panic!(),
        };
        let mut end = 0;
        let mut new_offset = h.shoff(id) as usize;
        let mut gap = usize::MAX;
        for (off, len) in sections.iter() {
            if end > 0 && *off >= end + extra_size && *off - (end + extra_size) < gap {
                new_offset = end;
                gap = *off - (end + extra_size)
            }
            end = align_next(*off + len, 8)
        }
        let shentsize = h.shentsize(id);
        let section_table_len = shnum as usize * shentsize as usize;
        let shoff = h.shoff(id) as usize;
        let total = shoff + section_table_len;
        assert!(extra_size + total <= self.map.len());
        if new_offset == shoff {
            // No space was found.
            assert!(shoff as usize + extra_size + section_table_len <= self.map.len());
            unsafe {
                // Moving just the section header table
                std::ptr::copy(
                    self.map.as_ptr().add(shoff as usize),
                    self.map.as_mut_ptr().add(shoff as usize + extra_size),
                    section_table_len,
                );
                self.header_mut().set_shoff(id, shoff as usize + extra_size);
            }
        }
        assert!(new_offset as usize + new.len() <= self.map.len());
        unsafe {
            // Write the new value
            self.map
                .as_mut_ptr()
                .add(new_offset as usize)
                .write_bytes(0, extra_size);
            std::ptr::copy(
                new.as_ptr() as *const i8,
                self.map.as_mut_ptr().add(new_offset as usize) as *mut i8,
                new.len(),
            );
        }
        // Update the section
        let mut s = self.section_mut(interp_i as usize);
        s.set_offset(id, new_offset);
        s.set_size(id, new_len);
        // Do the same in the program header table
        let phnum = self.header().phnum(id);
        for i in 0..phnum {
            let mut p = self.program_mut(i as usize);
            let p_off = p.offset(id);
            if p_off == off {
                // the new offset is the old shoff
                p.set_offset(id, new_offset as usize);
                p.set_filesz(id, new_len);
                p.set_memsz(id, new_len);
            }
        }
        extra_size
    }
    /// Sets the runpath. Note that this doesn't modify the underlying
    /// file yet, and can be changed at any later time.
    pub fn set_runpath(&mut self, runpath: &[u8]) -> &mut Self {
        self.new_runpath.clear();
        self.new_runpath.extend(runpath);
        self
    }
    /// Add a needed library. This is useful for example for dynamic
    /// libraries loaded using `dlopen`.
    pub fn add_needed(&mut self, needed: &[u8]) -> Result<&mut Self, Error> {
        if self.new_needed.is_none() {
            let parsed = self.parse()?;
            let owned = parsed.current_needed_owned()?;
            self.new_needed = Some(owned)
        }
        if let Some(ref mut n) = self.new_needed {
            if n.iter().all(|x| x != needed) {
                n.push(needed.to_vec().into());
            }
        }
        Ok(self)
    }
    /// Remove multiple needed libraries in a single pass. This
    /// function works like `Vec::retain`: the `retain` function is
    /// passed nedeed library names in order, and these items are kept
    /// if and only if `retain` returns `true`.
    pub fn retain_needed<F: FnMut(&[u8]) -> bool>(
        &mut self,
        mut retain: F,
    ) -> Result<&mut Self, Error> {
        if self.new_needed.is_none() {
            let parsed = self.parse()?;
            let owned = parsed.current_needed_owned()?;
            self.new_needed = Some(owned);
        }
        if let Some(ref mut n) = self.new_needed {
            n.retain(|x| retain(&*x));
        }
        Ok(self)
    }
    fn update_sections(
        &mut self,
        dynstr: &mut Vec<u8>,
        dynamic: &mut OwnedDynamic,
    ) -> Result<(), Error> {
        // Start by saving the current runpath
        let parsed = self.parse()?;
        let runpath = parsed.runpath()?.map(|x| x.to_bytes_with_nul().to_vec());
        remove_trailing_needed_runpath(dynstr, dynamic);
        if self.new_runpath.is_empty() {
            if let Some(runpath) = runpath {
                set_runpath(dynstr, dynamic, &runpath)
            }
        } else {
            set_runpath(dynstr, dynamic, &self.new_runpath)
        }
        if let Some(ref mut needed) = self.new_needed {
            retain_needed(dynstr, dynamic, needed);
        }
        Ok(())
    }
    pub fn update(mut self) -> Result<(), Error> {
        let p = self.parse()?;
        let mut dynstr_owned = p.dynstr.0.to_vec();
        let mut dynamic_owned = p.dynamic.to_owned();
        self.update_sections(&mut dynstr_owned, &mut dynamic_owned)?;
        let extra_room = ((self.new_interp.len() + 7) & !7)
            + dynstr_owned.len()
            + dynamic_owned.as_bytes().len();
        let f = self.f.take().unwrap();
        let new_interp = std::mem::replace(&mut self.new_interp, Vec::new());
        let new_runpath = std::mem::replace(&mut self.new_runpath, Vec::new());
        let new_needed = std::mem::replace(&mut self.new_needed, None);
        std::mem::drop(self);
        let current_len = f.metadata()?.len();
        f.set_len(current_len + extra_room as u64)?;
        let mut elf = Elf::open(f)?;
        let mut extra = 0;
        if !new_interp.is_empty() {
            extra += elf.update_section(b".interp", &new_interp).unwrap()
        }
        if !new_runpath.is_empty() {
            set_runpath(&mut dynstr_owned, &mut dynamic_owned, &new_runpath)
        }
        if new_needed.is_some() || !new_runpath.is_empty() {
            extra += elf.update_section(b".dynstr", &dynstr_owned).unwrap()
                + elf
                    .update_section(b".dynamic", dynamic_owned.as_bytes())
                    .unwrap();
        }
        f.set_len(current_len + extra as u64)?;
        Ok(())
    }
    pub fn set_interpreter(&mut self, new: &[u8]) -> &mut Self {
        self.new_interp = new.to_vec();
        self
    }
}
/// An index to some of the sections of the file.
///
/// This is used to avoid going through the list of sections for each
/// request. There are rarely many sections, but since the underlying
/// ELF file is memory-mapped, merely loading the list could incur
/// unnecessary IO.
#[derive(Debug)]
pub struct Parsed<'a> {
    dynamic: Dynamic<'a>,
    dynstr: Names<'a>,
    interp: &'a [u8],
}
#[derive(Debug, Clone)]
enum OwnedDynamic {
    B32(Vec<Elf32Dyn>),
    B64(Vec<Elf64Dyn>),
}
impl OwnedDynamic {
    fn as_bytes(&self) -> &[u8] {
        // The `unsafe` here are always satisfied since the inputs to
        // `from_raw_parts` are taken from valid `Vec`s.
        match self {
            OwnedDynamic::B32(x) => unsafe {
                std::slice::from_raw_parts(
                    x.as_ptr() as *const u8,
                    x.len() * std::mem::size_of::<Elf32Dyn>(),
                )
            },
            OwnedDynamic::B64(x) => unsafe {
                std::slice::from_raw_parts(
                    x.as_ptr() as *const u8,
                    x.len() * std::mem::size_of::<Elf64Dyn>(),
                )
            },
        }
    }
}
impl<'a> Dynamic<'a> {
    fn to_owned(&self) -> OwnedDynamic {
        match self {
            Dynamic::B32(x) => OwnedDynamic::B32(x.to_vec()),
            Dynamic::B64(x) => OwnedDynamic::B64(x.to_vec()),
        }
    }
}
fn remove_trailing_needed_runpath_<F: Flags>(dynstr: &mut Vec<u8>, dynamic: &mut Vec<F::Dyn>) {
    // Put the tags last
    let mut off: Vec<F::Dyn> = dynamic
        .iter()
        .filter_map(|x| {
            if F::tag(*x) == F::dt_needed() || F::tag(*x) == F::dt_runpath() {
                Some(*x)
            } else {
                None
            }
        })
        .collect();
    off.sort_by_key(|x| F::d_un(*x));
    let mut removed = std::collections::HashSet::new();
    while let Some(p) = off.pop() {
        let c = CStr::from_bytes_until_nul(&dynstr[F::d_un(p) as usize..]).unwrap();
        let len = c.count_bytes() + 1;
        if F::d_un(p) as usize + len >= dynstr.len() {
            dynstr.truncate(F::d_un(p) as usize);
            removed.insert(p);
        } else {
            off.push(p);
            break;
        }
    }
    dynamic.retain(|x| !removed.contains(x))
}
fn remove_trailing_needed_runpath(dynstr: &mut Vec<u8>, dynamic: &mut OwnedDynamic) {
    match dynamic {
        OwnedDynamic::B32(b) => remove_trailing_needed_runpath_::<u32>(dynstr, b),
        OwnedDynamic::B64(b) => remove_trailing_needed_runpath_::<u64>(dynstr, b),
    }
}
fn set_runpath_<F: Flags>(dynstr: &mut Vec<u8>, dynamic: &mut Vec<F::Dyn>, rpath: &[u8]) {
    let mut n = 0;
    for (i, x) in dynamic.iter_mut().enumerate() {
        if F::tag(*x) == F::dt_runpath() {
            // Test for rpath size
            let current = &mut dynstr[F::d_un(*x)..];
            let pos = current.iter().position(|x| *x == 0).unwrap();
            if pos + 1 >= rpath.len() {
                // If the current CStr representing the rpath is at least
                // as long as the new rpath, replace
                let current = &mut current[..rpath.len()];
                current.clone_from_slice(rpath);
            } else {
                // Else, insert at the end.
                let offset = dynstr.len();
                dynstr.extend(rpath);
                F::set_d_un(x, offset);
            }
            return;
        } else if F::tag(*x) != F::tag_nul() {
            n = i
        }
    }
    let offset = dynstr.len();
    dynstr.extend(rpath);
    dynamic.insert(n, F::dyn_(F::dt_runpath(), offset))
}
fn retain_needed(dynstr: &mut Vec<u8>, dynamic: &mut OwnedDynamic, needed: &mut Vec<Vec<u8>>) {
    match dynamic {
        OwnedDynamic::B32(b) => retain_needed_::<u32>(dynstr, b, needed),
        OwnedDynamic::B64(b) => retain_needed_::<u64>(dynstr, b, needed),
    }
}
fn retain_needed_<F: Flags>(dynstr: &mut Vec<u8>, dynamic: &mut Vec<F::Dyn>, needed: &[Vec<u8>]) {
    // Try to reuse existing strings from needed libs.
    let mut offsets = HashMap::new();
    for d in dynamic.iter() {
        if F::tag(*d) == F::dt_needed() {
            let off = F::d_un(*d);
            if off < dynstr.len() {
                if let Ok(c) = CStr::from_bytes_with_nul(&dynstr[off..]) {
                    offsets.insert(c.to_bytes_with_nul(), off);
                }
            }
        }
    }
    let mut new_dynamic = Vec::with_capacity(dynamic.len() + needed.len());
    let mut needed_it = needed.iter();
    let mut extra_dynstr = Vec::with_capacity(needed.len() * 20);
    for mut d in dynamic.drain(..) {
        if F::tag(d) == F::tag_nul() {
            break;
        } else if F::tag(d) != F::dt_needed() {
            new_dynamic.push(d);
        } else if let Some(needed) = needed_it.next() {
            if let Some(off) = offsets.get(needed.as_slice()) {
                F::set_d_un(&mut d, *off);
                new_dynamic.push(d)
            } else {
                F::set_d_un(&mut d, dynstr.len() + extra_dynstr.len());
                extra_dynstr.extend(needed.as_slice());
                new_dynamic.push(d)
            }
        }
    }
    for needed in needed_it {
        if let Some(off) = offsets.get(needed.as_slice()) {
            new_dynamic.push(F::dyn_(F::dt_needed(), *off))
        } else {
            new_dynamic.push(F::dyn_(F::dt_needed(), dynstr.len() + extra_dynstr.len()));
            extra_dynstr.extend(needed.as_slice());
        }
    }
    dynstr.extend(&extra_dynstr);
    new_dynamic.push(F::dyn_(F::tag_nul(), 0));
    if new_dynamic.len() % 1 == 1 {
        // Make the length even. I couldn't find it in the spec, but
        // ld seems to do that.
        new_dynamic.push(F::dyn_(F::tag_nul(), 0));
    }
    *dynamic = new_dynamic;
}
fn set_runpath(dynstr: &mut Vec<u8>, dynamic: &mut OwnedDynamic, rpath: &[u8]) {
    match dynamic {
        OwnedDynamic::B32(b) => set_runpath_::<u32>(dynstr, b, rpath),
        OwnedDynamic::B64(b) => set_runpath_::<u64>(dynstr, b, rpath),
    }
}
enum Either<I, A: Iterator<Item = I>, B: Iterator<Item = I>> {
    A(A),
    B(B),
}
impl<I, A: Iterator<Item = I>, B: Iterator<Item = I>> Iterator for Either<I, A, B> {
    type Item = I;
    fn next(&mut self) -> Option<I> {
        match self {
            Either::A(a) => a.next(),
            Either::B(b) => b.next(),
        }
    }
}
impl<'a> Parsed<'a> {
    /// Return the runpath of the ELF file.
    ///
    /// Note that we actually mean "runpath" and not "rpath", which
    /// was used in the past with a more complex and less flexible
    /// semantics. This crate doesn't handle the rpath field at the
    /// moment. More information <a
    /// href="https://en.wikipedia.org/wiki/Rpath">on Wikipedia</a>.
    ///
    /// The error case of this function comes from invalid ELF file.
    pub fn runpath(&self) -> Result<Option<&'a CStr>, Error> {
        let mut rpath = None;
        match self.dynamic {
            Dynamic::B64(dyn_) => {
                for d in dyn_ {
                    if d.tag == <u64 as Flags>::dt_runpath() {
                        rpath = Some(self.dynstr.name(d.d_un as usize)?);
                    }
                }
            }
            Dynamic::B32(dyn_) => {
                for d in dyn_ {
                    if d.tag == <u32 as Flags>::dt_runpath() {
                        rpath = Some(self.dynstr.name(d.d_un as usize)?);
                    }
                }
            }
        }
        Ok(rpath)
    }
    /// Iterator on the needed libraries.
    ///
    /// When launching a binary, the "interpreter" will typically
    /// resolve these from the runpath and load them in memory before
    /// start.
    ///
    /// The error case of this function comes from invalid ELF file.
    pub fn needed(&self) -> impl Iterator<Item = Result<&'a CStr, Error>> {
        match self.dynamic {
            Dynamic::B64(dyn_) => Either::A(dyn_.iter().filter_map(|d| {
                if d.tag == <u64 as Flags>::dt_needed() {
                    Some(self.dynstr.name(d.d_un as usize))
                } else {
                    None
                }
            })),
            Dynamic::B32(dyn_) => Either::B(dyn_.iter().filter_map(|d| {
                if d.tag == <u32 as Flags>::dt_needed() {
                    Some(self.dynstr.name(d.d_un as usize))
                } else {
                    None
                }
            })),
        }
    }
    fn current_needed_owned(&self) -> Result<Vec<Vec<u8>>, Error> {
        self.needed()
            .map(|x| x.map(|x| x.to_bytes_with_nul().to_vec()))
            .collect()
    }
    /// Intepreter of the ELF file.
    ///
    /// The interpreter (often found at `/lib/ld.so`) is the program
    /// that resolves the dynamic libraries "needed" by the ELF, using
    /// the runpath variable.
    ///
    /// The error case of this function comes from invalid ELF file.
    pub fn interpreter(&self) -> Result<&'a CStr, Error> {
        Ok(CStr::from_bytes_until_nul(self.interp).unwrap())
    }
}
#[derive(Debug)]
enum Dynamic<'a> {
    B32(&'a [Elf32Dyn]),
    B64(&'a [Elf64Dyn]),
}
impl<'a> Iterator for Dynamic<'a> {
    type Item = Elf64Dyn;
    fn next(&mut self) -> Option<Self::Item> {
        match self {
            Dynamic::B32(x) => {
                if x.is_empty() {
                    None
                } else {
                    let (a, b) = x.split_at(1);
                    *x = b;
                    let a = a[0];
                    Some(Elf64Dyn {
                        tag: DynTag64(a.tag.0 as u64),
                        d_un: a.d_un as u64,
                    })
                }
            }
            Dynamic::B64(x) => {
                if x.is_empty() {
                    None
                } else {
                    let (a, b) = x.split_at(1);
                    *x = b;
                    Some(a[0])
                }
            }
        }
    }
}
#[derive(Debug)]
struct Names<'a>(&'a [u8]);
impl<'a> Names<'a> {
    fn name(&self, n: usize) -> Result<&'a CStr, Error> {
        Ok(CStr::from_bytes_until_nul(&self.0[n..])?)
    }
}
trait Flags {
    type F32: std::fmt::Debug;
    type F64: std::fmt::Debug;
    type DynTag: std::fmt::Debug + std::convert::From<u64> + PartialEq;
    type Dyn: Copy + std::fmt::Debug + PartialEq + Eq + std::hash::Hash;
    fn dyn_(tag: Self::DynTag, d_un: usize) -> Self::Dyn;
    fn d_un(_: Self::Dyn) -> usize;
    fn set_d_un(_: &mut Self::Dyn, _: usize);
    fn tag(_: Self::Dyn) -> Self::DynTag;
    fn tag_nul() -> Self::DynTag;
    fn dt_needed() -> Self::DynTag {
        Self::DynTag::from(1)
    }
    fn dt_runpath() -> Self::DynTag {
        Self::DynTag::from(29)
    }
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
struct DynTag32(u32);
impl std::convert::From<u64> for DynTag32 {
    fn from(e: u64) -> Self {
        Self(e as u32)
    }
}
impl std::convert::From<u64> for DynTag64 {
    fn from(e: u64) -> Self {
        Self(e)
    }
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
struct DynTag64(u64);
impl Flags for u32 {
    type F32 = u32;
    type F64 = ();
    type DynTag = DynTag32;
    type Dyn = Elf32Dyn;
    fn dyn_(tag: Self::DynTag, d_un: usize) -> Self::Dyn {
        Elf32Dyn {
            tag,
            d_un: d_un as u32,
        }
    }
    fn set_d_un(x: &mut Self::Dyn, val: usize) {
        x.d_un = val as u32
    }
    fn tag_nul() -> Self::DynTag {
        DynTag32(0)
    }
    fn d_un(x: Self::Dyn) -> usize {
        x.d_un as usize
    }
    fn tag(x: Self::Dyn) -> Self::DynTag {
        x.tag
    }
}
impl Flags for u64 {
    type F32 = ();
    type F64 = u32;
    type DynTag = DynTag64;
    type Dyn = Elf64Dyn;
    fn dyn_(tag: Self::DynTag, d_un: usize) -> Self::Dyn {
        Elf64Dyn {
            tag,
            d_un: d_un as u64,
        }
    }
    fn set_d_un(x: &mut Self::Dyn, val: usize) {
        x.d_un = val as u64
    }
    fn tag_nul() -> Self::DynTag {
        DynTag64(0)
    }
    fn d_un(x: Self::Dyn) -> usize {
        x.d_un as usize
    }
    fn tag(x: Self::Dyn) -> Self::DynTag {
        x.tag
    }
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
struct Elf32Dyn {
    tag: DynTag32,
    d_un: u32,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
struct Elf64Dyn {
    tag: DynTag64,
    d_un: u64,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Sht(u32);
#[allow(dead_code)]
impl Sht {
    const NULL: Self = Sht(0);
    const PROGBITS: Self = Sht(1);
    const SYMTAB: Self = Sht(2);
    const STRTAB: Self = Sht(3);
    const RELA: Self = Sht(4);
    const HASH: Self = Sht(5);
    const DYNAMIC: Self = Sht(6);
    const NOTE: Self = Sht(7);
}
#[derive(Debug, Clone, Copy)]
enum Header_<'a> {
    B32(&'a Header<u32>),
    B64(&'a Header<u64>),
}
#[derive(Debug)]
enum HeaderMut_<'a> {
    B32(&'a mut Header<u32>),
    B64(&'a mut Header<u64>),
}
impl<'a> HeaderMut_<'a> {
    fn set_shoff(&mut self, id: Endianness, off: usize) {
        match self {
            HeaderMut_::B32(h) => h.shoff = <Endian<u32>>::from(id, off as u32),
            HeaderMut_::B64(h) => h.shoff = <Endian<u64>>::from(id, off as u64),
        }
    }
}
impl<'a> Header_<'a> {
    fn shstrndx(&self, id: Endianness) -> u16 {
        match self {
            Header_::B32(h) => EndianT::endian(h.shstrndx, id),
            Header_::B64(h) => EndianT::endian(h.shstrndx, id),
        }
    }
    fn shnum(&self, id: Endianness) -> u16 {
        match self {
            Header_::B32(h) => EndianT::endian(h.shnum, id),
            Header_::B64(h) => EndianT::endian(h.shnum, id),
        }
    }
    fn shoff(&self, id: Endianness) -> u64 {
        match self {
            Header_::B32(h) => EndianT::endian(h.shoff, id) as u64,
            Header_::B64(h) => EndianT::endian(h.shoff, id),
        }
    }
    fn shentsize(&self, id: Endianness) -> u16 {
        match self {
            Header_::B32(h) => EndianT::endian(h.shentsize, id),
            Header_::B64(h) => EndianT::endian(h.shentsize, id),
        }
    }
    fn phentsize(&self, id: Endianness) -> u16 {
        match self {
            Header_::B32(h) => EndianT::endian(h.phentsize, id),
            Header_::B64(h) => EndianT::endian(h.phentsize, id),
        }
    }
    fn phnum(&self, id: Endianness) -> u16 {
        match self {
            Header_::B32(h) => EndianT::endian(h.phnum, id),
            Header_::B64(h) => EndianT::endian(h.phnum, id),
        }
    }
    fn phoff(&self, id: Endianness) -> u64 {
        match self {
            Header_::B32(h) => EndianT::endian(h.phoff, id) as u64,
            Header_::B64(h) => EndianT::endian(h.phoff, id),
        }
    }
}

# Elfedit, a fast library for editing ELF files
Feel free to contribute to this project, the license is GPL 3.0 or
later.
## Use of unsafe
For performance reasons, this crate maps the ELF files in memory and
reads various fields directly from that memory. This is typically a
highly unsafe thing to do, especially when the offsets in the file are
given by the file itself.
In particular, the memory alignment of various fields and structs in
the ELF format is carefully designed to make reading extremely
efficient.
In order to mitigate our use of `unsafe`, we assert the preconditions
on each use, without assuming any further hypothesis.
## Security
Patching ELF files has major security implications. This project
acknowledges that and tries to be as careful as possible. However, it
is possible that bugs slip through.
If that happens and causes security issues, this project follows a
responsible disclosure policy. Please contact `pe@pijul.org` if you
suspect you may have found a bug ith security implications.

[package]
name = "elfedit"
version = "0.1.0"
edition = "2024"
include = [
  "Cargo.toml",
  "src/lib.rs",
  "src/hello",
  "COPYING",
  "README.md",
]
[dependencies]
memmap = "0.7.0"
tempfile = "3.19.1"
thiserror = "2.0.12"
[dev-dependencies]
tempfile = "3.19.1"

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GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.
  17. Interpretation of Sections 15 and 16.
  If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.
                     END OF TERMS AND CONDITIONS
            How to Apply These Terms to Your New Programs
  If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
  To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
    <one line to give the program's name and a brief idea of what it does.>
    Copyright (C) <year>  <name of author>
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
  If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
    <program>  Copyright (C) <year>  <name of author>
    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
    This is free software, and you are welcome to redistribute it
    under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License.  Of course, your program's commands
might be different; for a GUI interface, you would use an "about box".
  You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
<https://www.gnu.org/licenses/>.
  The GNU General Public License does not permit incorporating your program
into proprietary programs.  If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications with
the library.  If this is what you want to do, use the GNU Lesser General
Public License instead of this License.  But first, please read
<https://www.gnu.org/licenses/why-not-lgpl.html>.