use gix_error::ValidationError;use gix_error::bstr::ByteSlice;use std::ops::Range;use crate::{file, file::index};impl file::Index { /// Provided a mapped file at the beginning via `data`, starting at `toc_offset` decode all chunk information to return /// an index with `num_chunks` chunks. pub fn from_bytes(data: &[u8], toc_offset: usize, num_chunks: u32) -> Result<Self, ValidationError> { if num_chunks == 0 { return Err(ValidationError::new( "Empty chunk indices are not allowed as the point of chunked files is to have chunks.", )); } let data_len: u64 = data.len() as u64; let mut chunks = Vec::with_capacity(num_chunks as usize); let mut toc_entry = &data[toc_offset..]; let expected_min_size = (num_chunks as usize + 1) * file::Index::ENTRY_SIZE; if toc_entry.len() < expected_min_size { Err(format!( "The table of contents would be {expected_min_size} bytes, but got only {toc_entry_len}", toc_entry_len = toc_entry.len() ))?; } for chunk_idx in 0..num_chunks { let (kind, offset) = toc_entry.split_at(4); let kind = to_kind(kind); if kind == crate::SENTINEL { Err(format!( "Sentinel value encountered while processing chunks {chunk_idx} of {num_chunks}" ))?; } if chunks.iter().any(|c: &index::Entry| c.kind == kind) { Err(format!( "The chunk of kind '{}' was encountered more than once", kind.as_bstr() ))?; } let offset = be_u64(offset); if offset > data_len { Err(format!( "The chunk offset {offset} went past the file of length {data_len} - was it truncated?", ))?; } toc_entry = &toc_entry[file::Index::ENTRY_SIZE..]; let next_offset = be_u64(&toc_entry[4..]); if next_offset > data_len { Err(format!( "The chunk offset {next_offset} went past the file of length {data_len} - was it truncated?" ))?; } if next_offset <= offset { Err("All chunk offsets must be incrementing.")?; } chunks.push(index::Entry { kind, offset: Range { start: offset, end: next_offset, }, }); } let sentinel = to_kind(&toc_entry[..4]); if sentinel != crate::SENTINEL { Err(format!("Sentinel value wasn't found, saw '{}'", sentinel.as_bstr()))?; } Ok(file::Index { chunks, will_write: false, }) }}fn to_kind(data: &[u8]) -> crate::Id { data[..4].try_into().unwrap()}fn be_u64(data: &[u8]) -> u64 { u64::from_be_bytes(data[..8].try_into().unwrap())}
use gix_error::ValidationError;
use gix_error::bstr::ByteSlice;
use std::ops::Range;
use crate::{file, file::index};
impl file::Index {
/// Provided a mapped file at the beginning via `data`, starting at `toc_offset` decode all chunk information to return
/// an index with `num_chunks` chunks.
pub fn from_bytes(data: &[u8], toc_offset: usize, num_chunks: u32) -> Result<Self, ValidationError> {
if num_chunks == 0 {
return Err(ValidationError::new(
"Empty chunk indices are not allowed as the point of chunked files is to have chunks.",
));
}
let data_len: u64 = data.len() as u64;
let mut chunks = Vec::with_capacity(num_chunks as usize);
let mut toc_entry = &data[toc_offset..];
let expected_min_size = (num_chunks as usize + 1) * file::Index::ENTRY_SIZE;
if toc_entry.len() < expected_min_size {
Err(format!(
"The table of contents would be {expected_min_size} bytes, but got only {toc_entry_len}",
toc_entry_len = toc_entry.len()
))?;
}
for chunk_idx in 0..num_chunks {
let (kind, offset) = toc_entry.split_at(4);
let kind = to_kind(kind);
if kind == crate::SENTINEL {
Err(format!(
"Sentinel value encountered while processing chunks {chunk_idx} of {num_chunks}"
))?;
}
if chunks.iter().any(|c: &index::Entry| c.kind == kind) {
Err(format!(
"The chunk of kind '{}' was encountered more than once",
kind.as_bstr()
))?;
}
let offset = be_u64(offset);
if offset > data_len {
Err(format!(
"The chunk offset {offset} went past the file of length {data_len} - was it truncated?",
))?;
}
toc_entry = &toc_entry[file::Index::ENTRY_SIZE..];
let next_offset = be_u64(&toc_entry[4..]);
if next_offset > data_len {
Err(format!(
"The chunk offset {next_offset} went past the file of length {data_len} - was it truncated?"
))?;
}
if next_offset <= offset {
Err("All chunk offsets must be incrementing.")?;
}
chunks.push(index::Entry {
kind,
offset: Range {
start: offset,
end: next_offset,
},
});
}
let sentinel = to_kind(&toc_entry[..4]);
if sentinel != crate::SENTINEL {
Err(format!("Sentinel value wasn't found, saw '{}'", sentinel.as_bstr()))?;
}
Ok(file::Index {
chunks,
will_write: false,
})
}
}
fn to_kind(data: &[u8]) -> crate::Id {
data[..4].try_into().unwrap()
}
fn be_u64(data: &[u8]) -> u64 {
u64::from_be_bytes(data[..8].try_into().unwrap())
}