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Copy pathwrite.rs
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Copy pathwrite.rs
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341 lines (319 loc) · 13.5 KB
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//! Writing compound files ([MS-CFB] §2.2–2.6).
//!
//! Layout written by [`Writer::finish`] (sector numbers ascending): the sectors of every stream of
//! 4096 bytes or more, the mini stream, the mini FAT, the directory, the FAT, then DIFAT sectors
//! when the FAT needs more than the 109 header slots. Every chain is contiguous. Sibling trees are
//! balanced binary search trees coloured as valid red-black trees (§2.6.4).
use crate::{DIFSECT, ENDOFCHAIN, FATSECT, FREESECT, MINI_SECTOR_SIZE, MINI_STREAM_CUTOFF, NOSTREAM, Result, SIGNATURE, compare_names, validate_name};
/// File format version.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum Version {
/// Version 3: 512-byte sectors.
V3,
/// Version 4: 4096-byte sectors (AAF's "4K" files).
#[default]
V4,
}
impl Version {
fn sector_size(self) -> usize {
match self {
Version::V3 => 512,
Version::V4 => 4096,
}
}
}
/// A storage or stream added to a [`Writer`].
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct NodeId(pub usize);
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum Kind {
Root,
Storage,
Stream,
}
#[derive(Clone, Debug)]
struct Node {
name: String,
kind: Kind,
clsid: [u8; 16],
data: Vec<u8>,
children: Vec<usize>,
}
/// Builds a compound file in memory.
#[derive(Clone, Debug)]
pub struct Writer {
version: Version,
nodes: Vec<Node>,
}
impl Default for Writer {
fn default() -> Self {
Writer::new(Version::default())
}
}
impl Writer {
/// The root storage.
pub const ROOT: NodeId = NodeId(0);
pub fn new(version: Version) -> Self {
Writer { version, nodes: vec![Node { name: "Root Entry".into(), kind: Kind::Root, clsid: [0; 16], data: Vec::new(), children: Vec::new() }] }
}
fn add(&mut self, parent: NodeId, name: &str, kind: Kind, clsid: [u8; 16], data: Vec<u8>) -> Result<NodeId> {
validate_name(name)?;
let p = self.nodes.get(parent.0).ok_or_else(|| crate::Error::NotFound(format!("node {}", parent.0)))?;
if p.kind == Kind::Stream {
return Err(crate::Error::Invalid(format!("{:?} is a stream, not a storage", p.name)));
}
if p.children.iter().any(|&c| compare_names(&self.nodes[c].name, name).is_eq()) {
return Err(crate::Error::BadName(format!("duplicate name {name}")));
}
let id = self.nodes.len();
self.nodes.push(Node { name: name.to_string(), kind, clsid, data, children: Vec::new() });
self.nodes[parent.0].children.push(id);
Ok(NodeId(id))
}
/// Add a storage below `parent`.
pub fn storage(&mut self, parent: NodeId, name: &str, clsid: [u8; 16]) -> Result<NodeId> {
self.add(parent, name, Kind::Storage, clsid, Vec::new())
}
/// Add a stream below `parent`.
pub fn stream(&mut self, parent: NodeId, name: &str, data: Vec<u8>) -> Result<NodeId> {
self.add(parent, name, Kind::Stream, [0; 16], data)
}
/// Set the class id of a storage (or the root).
pub fn set_clsid(&mut self, node: NodeId, clsid: [u8; 16]) {
if let Some(n) = self.nodes.get_mut(node.0) {
n.clsid = clsid;
}
}
/// Lay the file out and return its bytes.
pub fn finish(self) -> Vec<u8> {
let ss = self.version.sector_size();
let per_sector = ss / 4;
// Directory order: depth-first pre-order from the root.
let mut order = Vec::with_capacity(self.nodes.len());
let mut stack = vec![0usize];
while let Some(n) = stack.pop() {
order.push(n);
for &c in self.nodes[n].children.iter().rev() {
stack.push(c);
}
}
let mut dir_index = vec![0u32; self.nodes.len()];
for (i, &n) in order.iter().enumerate() {
dir_index[n] = i as u32;
}
// Stream placement.
let mut start = vec![ENDOFCHAIN; self.nodes.len()];
let mut next_sector = 0u32;
let mut big_chains: Vec<(u32, u32)> = Vec::new(); // (first, count)
for &n in &order {
let node = &self.nodes[n];
if node.kind == Kind::Stream && node.data.len() as u64 >= MINI_STREAM_CUTOFF as u64 {
let count = node.data.len().div_ceil(ss) as u32;
start[n] = next_sector;
big_chains.push((next_sector, count));
next_sector += count;
}
}
let mut next_mini = 0u32;
let mut mini_chains: Vec<(u32, u32)> = Vec::new();
for &n in &order {
let node = &self.nodes[n];
if node.kind == Kind::Stream && !node.data.is_empty() && (node.data.len() as u64) < MINI_STREAM_CUTOFF as u64 {
let count = node.data.len().div_ceil(MINI_SECTOR_SIZE) as u32;
start[n] = next_mini;
mini_chains.push((next_mini, count));
next_mini += count;
}
}
let mini_bytes = next_mini as usize * MINI_SECTOR_SIZE;
let mini_stream_sectors = mini_bytes.div_ceil(ss) as u32;
let mini_stream_start = if mini_stream_sectors > 0 { next_sector } else { ENDOFCHAIN };
next_sector += mini_stream_sectors;
let minifat_sectors = (next_mini as usize * 4).div_ceil(ss) as u32;
let minifat_start = if minifat_sectors > 0 { next_sector } else { ENDOFCHAIN };
next_sector += minifat_sectors;
let dir_sectors = (order.len() * 128).div_ceil(ss) as u32;
let dir_start = next_sector;
next_sector += dir_sectors;
let base = next_sector as usize;
let (mut fat_n, mut difat_n) = (1usize, 0usize);
loop {
let total = base + fat_n + difat_n;
let need_fat = total.div_ceil(per_sector);
let need_difat = if need_fat > 109 { (need_fat - 109).div_ceil(per_sector - 1) } else { 0 };
if need_fat == fat_n && need_difat == difat_n {
break;
}
fat_n = need_fat.max(fat_n);
difat_n = need_difat.max(difat_n);
}
let fat_start = next_sector;
let difat_start = fat_start + fat_n as u32;
let total = base + fat_n + difat_n;
// FAT.
let mut fat = vec![FREESECT; fat_n * per_sector];
let chain = |first: u32, count: u32, fat: &mut [u32]| {
for i in 0..count {
fat[(first + i) as usize] = if i + 1 == count { ENDOFCHAIN } else { first + i + 1 };
}
};
for &(f, c) in &big_chains {
chain(f, c, &mut fat);
}
if mini_stream_sectors > 0 {
chain(mini_stream_start, mini_stream_sectors, &mut fat);
}
if minifat_sectors > 0 {
chain(minifat_start, minifat_sectors, &mut fat);
}
chain(dir_start, dir_sectors, &mut fat);
for i in 0..fat_n {
fat[fat_start as usize + i] = FATSECT;
}
for i in 0..difat_n {
fat[difat_start as usize + i] = DIFSECT;
}
debug_assert!(total <= fat.len());
// Mini FAT.
let mut minifat = vec![FREESECT; minifat_sectors as usize * per_sector];
for &(f, c) in &mini_chains {
for i in 0..c {
minifat[(f + i) as usize] = if i + 1 == c { ENDOFCHAIN } else { f + i + 1 };
}
}
// Directory.
let mut tree = vec![(NOSTREAM, NOSTREAM, NOSTREAM, 1u8); self.nodes.len()]; // left, right, child, colour
for (p, node) in self.nodes.iter().enumerate() {
if node.kind == Kind::Stream || node.children.is_empty() {
continue;
}
let mut kids = node.children.clone();
kids.sort_by(|&a, &b| compare_names(&self.nodes[a].name, &self.nodes[b].name));
let height = usize::BITS - (kids.len() + 1).leading_zeros() - 1; // floor(log2(n + 1))
let perfect = (1usize << height) - 1 == kids.len();
let root = build_tree(&kids, 0, perfect, height as usize, &mut tree, &dir_index);
tree[p].2 = root;
}
let mut dir = Vec::with_capacity(dir_sectors as usize * ss);
for &n in &order {
let node = &self.nodes[n];
let mut e = [0u8; 128];
let units: Vec<u16> = node.name.encode_utf16().collect();
for (i, u) in units.iter().enumerate() {
e[i * 2..i * 2 + 2].copy_from_slice(&u.to_le_bytes());
}
e[64..66].copy_from_slice(&(((units.len() + 1) * 2) as u16).to_le_bytes());
e[66] = match node.kind {
Kind::Root => 5,
Kind::Storage => 1,
Kind::Stream => 2,
};
let (l, r, c, colour) = tree[n];
e[67] = if node.kind == Kind::Root { 1 } else { colour };
e[68..72].copy_from_slice(&l.to_le_bytes());
e[72..76].copy_from_slice(&r.to_le_bytes());
e[76..80].copy_from_slice(&c.to_le_bytes());
e[80..96].copy_from_slice(&node.clsid);
let (st, size) = match node.kind {
Kind::Root => (mini_stream_start, mini_bytes as u64),
Kind::Storage => (0, 0),
Kind::Stream => (if node.data.is_empty() { ENDOFCHAIN } else { start[n] }, node.data.len() as u64),
};
e[116..120].copy_from_slice(&st.to_le_bytes());
e[120..128].copy_from_slice(&size.to_le_bytes());
dir.extend_from_slice(&e);
}
while dir.len() < dir_sectors as usize * ss {
let mut e = [0u8; 128];
e[68..80].copy_from_slice(&[0xFF; 12]);
dir.extend_from_slice(&e);
}
// Header.
let mut out = Vec::with_capacity((total + 1) * ss);
out.extend_from_slice(&SIGNATURE);
out.extend_from_slice(&[0; 16]);
out.extend_from_slice(&0x003Eu16.to_le_bytes());
out.extend_from_slice(&(if self.version == Version::V3 { 3u16 } else { 4u16 }).to_le_bytes());
out.extend_from_slice(&0xFFFEu16.to_le_bytes());
out.extend_from_slice(&(if self.version == Version::V3 { 9u16 } else { 12u16 }).to_le_bytes());
out.extend_from_slice(&6u16.to_le_bytes());
out.extend_from_slice(&[0; 6]);
out.extend_from_slice(&(if self.version == Version::V3 { 0 } else { dir_sectors }).to_le_bytes());
out.extend_from_slice(&(fat_n as u32).to_le_bytes());
out.extend_from_slice(&dir_start.to_le_bytes());
out.extend_from_slice(&0u32.to_le_bytes());
out.extend_from_slice(&MINI_STREAM_CUTOFF.to_le_bytes());
out.extend_from_slice(&minifat_start.to_le_bytes());
out.extend_from_slice(&minifat_sectors.to_le_bytes());
out.extend_from_slice(&(if difat_n > 0 { difat_start } else { ENDOFCHAIN }).to_le_bytes());
out.extend_from_slice(&(difat_n as u32).to_le_bytes());
for i in 0..109 {
let v = if i < fat_n { fat_start + i as u32 } else { FREESECT };
out.extend_from_slice(&v.to_le_bytes());
}
out.resize(ss, 0);
// Sectors.
let pad = |out: &mut Vec<u8>| {
let r = out.len() % ss;
if r != 0 {
out.resize(out.len() + ss - r, 0);
}
};
for &n in &order {
let node = &self.nodes[n];
if node.kind == Kind::Stream && node.data.len() as u64 >= MINI_STREAM_CUTOFF as u64 {
out.extend_from_slice(&node.data);
pad(&mut out);
}
}
for &n in &order {
let node = &self.nodes[n];
if node.kind == Kind::Stream && !node.data.is_empty() && (node.data.len() as u64) < MINI_STREAM_CUTOFF as u64 {
out.extend_from_slice(&node.data);
let r = node.data.len() % MINI_SECTOR_SIZE;
if r != 0 {
out.resize(out.len() + MINI_SECTOR_SIZE - r, 0);
}
}
}
pad(&mut out);
for v in &minifat {
out.extend_from_slice(&v.to_le_bytes());
}
out.extend_from_slice(&dir);
for v in &fat {
out.extend_from_slice(&v.to_le_bytes());
}
let mut remaining: Vec<u32> = (109..fat_n).map(|i| fat_start + i as u32).collect();
for i in 0..difat_n {
let mut s = Vec::with_capacity(ss);
let take = remaining.len().min(per_sector - 1);
for v in remaining.drain(..take) {
s.extend_from_slice(&v.to_le_bytes());
}
while s.len() < ss - 4 {
s.extend_from_slice(&FREESECT.to_le_bytes());
}
let next = if i + 1 < difat_n { difat_start + i as u32 + 1 } else { ENDOFCHAIN };
s.extend_from_slice(&next.to_le_bytes());
out.extend_from_slice(&s);
}
debug_assert_eq!(out.len(), (total + 1) * ss);
out
}
}
/// Balanced BST of `kids[..]` (sorted). Nodes on the bottom level of an imperfect tree are red,
/// so every root-to-leaf path has the same number of black nodes.
fn build_tree(kids: &[usize], depth: usize, perfect: bool, height: usize, tree: &mut [(u32, u32, u32, u8)], dir_index: &[u32]) -> u32 {
if kids.is_empty() {
return NOSTREAM;
}
let mid = kids.len() / 2;
let n = kids[mid];
let left = build_tree(&kids[..mid], depth + 1, perfect, height, tree, dir_index);
let right = build_tree(&kids[mid + 1..], depth + 1, perfect, height, tree, dir_index);
tree[n].0 = left;
tree[n].1 = right;
tree[n].3 = if !perfect && depth == height { 0 } else { 1 };
dir_index[n]
}