tar-wasi 0.4.38

A Rust implementation of a TAR file reader and writer. This library does not currently handle compression, but it is abstract over all I/O readers and writers. Additionally, great lengths are taken to ensure that the entire contents are never required to be entirely resident in memory all at once. This fork includes full support for running the library with WebAssembly via the target wasm32-wasi.
Documentation 
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use std::io;
use std::slice;
use std::str;

use crate::other;

/// An iterator over the pax extensions in an archive entry.
///
/// This iterator yields structures which can themselves be parsed into
/// key/value pairs.
pub struct PaxExtensions<'entry> {
    data: slice::Split<'entry, u8, fn(&u8) -> bool>,
}

/// A key/value pair corresponding to a pax extension.
pub struct PaxExtension<'entry> {
    key: &'entry [u8],
    value: &'entry [u8],
}

pub fn pax_extensions(a: &[u8]) -> PaxExtensions {
    fn is_newline(a: &u8) -> bool {
        *a == b'\n'
    }
    PaxExtensions {
        data: a.split(is_newline),
    }
}

pub fn pax_extensions_size(a: &[u8]) -> Option<u64> {
    for extension in pax_extensions(a) {
        let current_extension = match extension {
            Ok(ext) => ext,
            Err(_) => return None,
        };
        if current_extension.key() != Ok("size") {
            continue;
        }

        let value = match current_extension.value() {
            Ok(value) => value,
            Err(_) => return None,
        };
        let size = match value.parse::<u64>() {
            Ok(size) => size,
            Err(_) => return None,
        };
        return Some(size);
    }
    None
}

impl<'entry> Iterator for PaxExtensions<'entry> {
    type Item = io::Result<PaxExtension<'entry>>;

    fn next(&mut self) -> Option<io::Result<PaxExtension<'entry>>> {
        let line = match self.data.next() {
            Some(line) if line.is_empty() => return None,
            Some(line) => line,
            None => return None,
        };

        Some(
            line.iter()
                .position(|b| *b == b' ')
                .and_then(|i| {
                    str::from_utf8(&line[..i])
                        .ok()
                        .and_then(|len| len.parse::<usize>().ok().map(|j| (i + 1, j)))
                })
                .and_then(|(kvstart, reported_len)| {
                    if line.len() + 1 == reported_len {
                        line[kvstart..]
                            .iter()
                            .position(|b| *b == b'=')
                            .map(|equals| (kvstart, equals))
                    } else {
                        None
                    }
                })
                .map(|(kvstart, equals)| PaxExtension {
                    key: &line[kvstart..kvstart + equals],
                    value: &line[kvstart + equals + 1..],
                })
                .ok_or_else(|| other("malformed pax extension")),
        )
    }
}

impl<'entry> PaxExtension<'entry> {
    /// Returns the key for this key/value pair parsed as a string.
    ///
    /// May fail if the key isn't actually utf-8.
    pub fn key(&self) -> Result<&'entry str, str::Utf8Error> {
        str::from_utf8(self.key)
    }

    /// Returns the underlying raw bytes for the key of this key/value pair.
    pub fn key_bytes(&self) -> &'entry [u8] {
        self.key
    }

    /// Returns the value for this key/value pair parsed as a string.
    ///
    /// May fail if the value isn't actually utf-8.
    pub fn value(&self) -> Result<&'entry str, str::Utf8Error> {
        str::from_utf8(self.value)
    }

    /// Returns the underlying raw bytes for this value of this key/value pair.
    pub fn value_bytes(&self) -> &'entry [u8] {
        self.value
    }
}