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//! The underlying API of lucky_commit is also exposed as a Rust library, in case anyone
//! wants to use it programmatically. However, note that the library API is considered
//! unstable, and might have backwards-incompatible changes even in minor or patch
//! releases of the crate. If you use the library interface, pinning to an exact version
//! is recommended.
#![deny(missing_docs)]
use std::{
cmp::Ord,
error::Error,
fmt::{Debug, Display, Formatter},
iter, mem,
ops::Range,
str::FromStr,
sync::{
atomic::{AtomicBool, Ordering},
mpsc, Arc,
},
thread::{self, JoinHandle},
};
#[cfg(feature = "opencl")]
use ocl::{
builders::DeviceSpecifier::TypeFlags,
flags::{DeviceType, MemFlags},
prm::Uint16,
Buffer, Context, Kernel, Platform, Program, Queue,
};
#[cfg(feature = "opencl")]
use std::convert::TryInto;
/// A worker that, when invoked, will look in a predetermined search space to find a modification
/// to a specific commit that matches a specific hash spec.
#[derive(Debug, PartialEq)]
pub struct HashSearchWorker<H: GitHashFn> {
processed_commit: ProcessedCommit,
hash_spec: HashSpec<H>,
search_space: Range<u64>,
}
// The fully padded data that gets hashed is the concatenation of all the following:
// |--- GIT COMMIT HEADER (part of git's raw commit format) ---
// | * The ASCII string "commit "
// | * The byte-length of the entire "git commit" section below, represented as base-10 ASCII digits
// | * A null byte (0x0)
// |--- GIT COMMIT ---
// | * The original git commit object that was provided as input, in git's normal commit encoding, up
// | to the "padding insertion point". (For commits that are not GPG-signed, the padding insertion
// | point is right near the end of the commit. For commits that are GPG-signed, the padding insertion
// | point is at the end of the signature, which is right before the commit message.) This section
// | contains metadata such as the author, timestamp, and parent commit.
// | * Some number of ASCII space characters, as "static padding", such that the point after the static
// | padding is at a multiple-of-64-byte offset from the start of the data. Note that in very rare
// | pathological cases, more than 63 space characters will be needed. This is because adding static
// | padding also increases the length of the commit object, which is used in the git commit header
// | above. As a result, adding one additional padding character could increase the alignment by 2,
// | e.g. if the length increases from 999 to 1000.
// |
// | - NOTE: The length of all the data up to this point is a multiple of 64 bytes, and the length
// | of the all the data after this point is also a multiple of 64 bytes. For reasons that will
// | be explained in the declaration of `PartiallyHashedCommit`, the 64-byte blocks preceding
// | this point are called "static blocks", and the 64-byte blocks following this point are called
// | "dynamic blocks".
// |
// | * 48 bytes of "dynamic padding", consisting of some combination of ASCII space and tab characters.
// | This is the only part of the commit data that actually varies across hash invocations. The ultimate
// | goal is to find a dynamic padding arrangement that produces the desired hash. A 48-byte length was
// | chosen with the goal of only needing a single dynamic block for non-GPG-signed commits.
// | * The rest of the original commit object (from the "padding insertion point" onwards). For
// | non-GPG-signed commits, this will typically just be a single newline. For GPG-signed commits, this
// | will contain the commit message.
// |--- SHA1/SHA256 FINALIZATION PADDING (specified as part of the SHA1/SHA256 algorithm) ---
// | * The byte 0x80
// | * Up to 63 null bytes (0x0), such that the point after the null bytes is at an offset of 56 (mod 64) bytes
// | from the start of the data
// | * The bit-length of everything before the "finalization padding" section, represented as a big-endian
// | 64-bit integer
#[derive(Debug, PartialEq, Clone)]
struct ProcessedCommit {
/// The data, as specified in the comment above. The length will always be a multiple of 64 bytes.
data: Box<[u8]>,
/// The location of the git commit, as an index range into `data`
commit_range: Range<usize>,
/// The number of 64-byte static blocks in the data
num_static_blocks: usize,
}
/// A view of an underlying `ProcessedCommit`, with cached hash state.
///
/// SHA1 and SHA256 work as follows:
///
/// * First, a 20-byte or 32-byte "state vector" is initialized to a constant.
/// * Next, each each 64-byte block in the input is processed in sequence. The state vector after
/// processing a block is a convoluted, deteriministic function of (a) the state vector before
/// processing the block, and (b) the contents of the block. Processing blocks is the main performance
/// bottleneck of lucky-commit.
/// * The "hash" of some data is just the contents of the state vector after processing all of
/// the data (with finalization padding added to the end of the data, as described in the comment
/// about the `ProcessedCommit` format).
///
/// So there's a big optimization we can do here -- we have to compute a bunch of hashes, but the
/// only part of the data that we're changing between runs is the dynamic padding, which is very close
/// to the end of the data. The state vector after processing all of the blocks before the dynamic
/// padding (the "static blocks") doesn't depend at all on the contents of the dynamic padding -- it's
/// effectively a constant for any given `ProcessedCommit`. The purpose of `PartiallyHashedCommit` is
/// to cache that state vector, and only reprocess the "dynamic blocks" on each change to the dynamic
/// padding. This drastically reduces the number of blocks that need to be processed, resulting in a
/// ~5x end-to-end performance improvement for an average-sized commit.
#[derive(Debug)]
struct PartiallyHashedCommit<'a, H: GitHashFn> {
intermediate_state: H::State,
dynamic_blocks: &'a mut [H::Block],
}
/// Defines a spec for a desired commit hash.
#[derive(Debug, PartialEq, Clone)]
pub struct HashSpec<H: GitHashFn> {
/// The data in the desired hash, as split into big-endian four-byte chunks.
/// All bits that are unspecified (e.g. bits corresponding to the end of the hash, when only a prefix is being matched)
/// are set to zero.
data: H::State,
/// Mask containing bits set to 1 if the bit at that position is specified, and 0 otherwise.
mask: H::State,
// For example, the sha1 hash prefix "deadbeef123" corresponds to the
// following spec:
// HashSpec { data: [0xdeadbeef, 0x12300000, 0, 0, 0], mask: [0xffffffff, 0xfff00000, 0, 0, 0] }
}
/// An error that results from parsing an invalid HashSpec
#[non_exhaustive]
#[derive(PartialEq, Eq)]
pub enum ParseHashSpecErr {
/// The input string is longer than a hash with the specified algorithm
TooLong,
/// The input string contains characters which are neither hex characters nor '_'.
InvalidCharacter(char),
}
/// A git commit
#[derive(PartialEq, Eq)]
pub struct GitCommit<H: GitHashFn> {
/// The commit data, represented in git's object format
object: Vec<u8>,
/// The hash of the commit
hash: H::State,
}
/// A hash function used by git. This is a sealed trait implemented by `Sha1` and `Sha256`.
/// The fields and methods on this trait are subject to change. Consumers should pretend that
/// the types implementing the trait are opaque.
pub trait GitHashFn: private::Sealed + Debug + Send + Clone + Eq + 'static {
/// The type of the output and intermediate state of this hash function.
/// For sha1 and sha256, this is [u32; N] for some N. Ideally this trait would just
/// have an associated const for the length of the state vector, and then
/// `State` would be defined as `[u32; N]`, but this isn't possible due
/// to <https://github.com/rust-lang/rust/issues/60551>.
type State: AsRef<[u32]> + AsMut<[u32]> + Clone + Copy + Debug + Default + Eq + Send;
/// The initial value of the state vector for the given algorithm
const INITIAL_STATE: Self::State;
/// The datatype representing a block for this algorithm. This must be layout-equivalent
/// to [u8; 64], although the nominal type that gets used might be different on a
/// per-library basis due to const generic limitations.
type Block: AsRef<[u8]> + AsMut<[u8]> + Copy + Debug;
/// Processes a set of blocks using the given algorithm
fn compress(state: &mut Self::State, blocks: &[Self::Block]);
#[cfg(feature = "opencl")]
/// Source code of an OpenCL shader kernel finding hash matches for the given
/// algorithm. The kernel should have a function `scatter_padding_and_find_match`, which
/// accepts the following parameters:
/// 1. A pointer to the `data` in the desired hash spec (pointing to the appropriate
/// number of bytes for the given hash algorithm)
/// 1. A pointer to the `mask` of the desired hash spec
/// 1. The "base padding specifier" for the current run, which determines which padding will
/// be attempted. The padding specifier used by any given thread is equal to the base
/// specifier plus that thread's ID.
/// 1. A pointer to the intermediate state after all static blocks have been hashed
/// 1. A pointer to the dynamic blocks, encoded as big-endian 32-bit integers
/// 1. The number of dynamic blocks that are present
/// 1. A writeable pointer where the shader should write a thread ID if it finds an appropriate
/// match.
const KERNEL: &'static str;
}
/// The hash type used for Sha1 git repositories (the default at the time of writing)
/// This type is uninhabited, and is only intended to be used as a type parameter.
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Sha1 {}
impl GitHashFn for Sha1 {
type State = [u32; 5];
const INITIAL_STATE: Self::State = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0];
type Block = sha1::digest::core_api::Block<sha1::Sha1Core>;
fn compress(state: &mut Self::State, blocks: &[Self::Block]) {
sha1::compress(state, blocks)
}
#[cfg(feature = "opencl")]
const KERNEL: &'static str = include_str!("sha1_matcher.cl");
}
/// The hash type used for Sha256 git repositories.
/// This type is uninhabited, and is only intended to be used as a type parameter.
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Sha256 {}
impl GitHashFn for Sha256 {
type State = [u32; 8];
const INITIAL_STATE: Self::State = [
0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab,
0x5be0cd19,
];
type Block = sha2::digest::core_api::Block<sha2::Sha256>;
fn compress(state: &mut Self::State, blocks: &[Self::Block]) {
sha2::compress256(state, blocks)
}
#[cfg(feature = "opencl")]
const KERNEL: &'static str = include_str!("sha256_matcher.cl");
}
mod private {
pub trait Sealed {}
impl Sealed for super::Sha1 {}
impl Sealed for super::Sha256 {}
}
impl<H: GitHashFn> HashSearchWorker<H> {
/// Creates a worker for a specific commit and hash spec, with an initial
/// search space of 2**48.
pub fn new(current_commit: &[u8], hash_spec: HashSpec<H>) -> Self {
Self {
processed_commit: ProcessedCommit::new(current_commit),
hash_spec,
search_space: 0..(1 << 48),
}
}
/// Caps a worker's search space to approximately the given size.
pub fn with_capped_search_space(mut self, workload: u64) -> Self {
self.search_space = self.search_space.start
..Ord::min(self.search_space.end, self.search_space.start + workload);
self
}
/// Splits this worker into `divisor` new workers for the same commit and
/// desired hash, with the search space split roughly equally.
/// A worker's search space is an approximation to help with effecient threading. There is
/// no guarantee that the resulting workers have perfectly disjoint search spaces, so in theory
/// multiple workers could both find the same hash match despite having "split" the space.
fn split_search_space(self, divisor: u64) -> impl Iterator<Item = Self> {
let amount_per_worker = (self.search_space.end - self.search_space.start) / divisor;
(0..divisor).map(move |index| {
let range_start = index * amount_per_worker + self.search_space.start;
let range_end = if index < divisor - 1 {
range_start + amount_per_worker
} else {
// In case the work can't be divided perfectly, just give all the slack to the last
// worker. Typically, `amount_per_worker` will be many orders of magnitude larger
// than `divisor`, so having a few extra units of work is immaterial.
self.search_space.end
};
Self {
processed_commit: self.processed_commit.clone(),
hash_spec: self.hash_spec.clone(),
search_space: range_start..range_end,
}
})
}
/// Invokes the worker. The worker will return a git commit matching the hash,
/// if it finds one. Otherwise, it will return None after exhausing its entire search space.
pub fn search(self) -> Option<GitCommit<H>> {
#[cfg(feature = "opencl")]
if Self::gpus_available() {
return self.search_with_gpu().unwrap();
}
self.search_with_cpus()
}
#[cfg(feature = "opencl")]
fn gpus_available() -> bool {
Platform::first().is_ok()
&& !TypeFlags(DeviceType::GPU)
.to_device_list(None::<Platform>)
.unwrap()
.is_empty()
}
#[allow(clippy::needless_collect)]
fn search_with_cpus(self) -> Option<GitCommit<H>> {
let thread_count = num_cpus::get_physical();
let lame_duck_cancel_signal = Arc::new(AtomicBool::new(false));
let (shared_sender, receiver) = mpsc::channel();
let _handles = self
.split_search_space(thread_count as u64)
.map(|worker| {
let result_sender = shared_sender.clone();
let worker_cancel_signal = Arc::clone(&lame_duck_cancel_signal);
thread::spawn(move || {
let _ = result_sender
.send(worker.search_with_cpu_single_threaded(worker_cancel_signal));
})
})
.collect::<Vec<JoinHandle<()>>>();
for _ in 0..thread_count {
if let Some(result) = receiver.recv().unwrap() {
lame_duck_cancel_signal.store(true, Ordering::Relaxed);
// Lame-duck threads should halt shortly after any thread finds a match. However,
// we don't want to actually wait for them to halt when running in production, especially
// since the process will usually terminate shortly afterwards anyway. So the waiting
// and panic detection is debug/test-only
#[cfg(debug_assertions)]
_handles
.into_iter()
.map(JoinHandle::join)
.collect::<Result<Vec<_>, _>>()
.unwrap();
return Some(result);
}
}
None
}
#[inline(never)]
fn search_with_cpu_single_threaded(
self,
lame_duck_cancel_signal: Arc<AtomicBool>,
) -> Option<GitCommit<H>> {
let HashSearchWorker {
search_space,
hash_spec,
mut processed_commit,
..
} = self;
let mut partially_hashed_commit = processed_commit.as_partially_hashed_commit::<H>();
let lame_duck_check_interval = Ord::min(search_space.end - search_space.start, 1 << 20);
for base_padding_specifier in search_space.step_by(lame_duck_check_interval as usize) {
for index_in_interval in 0..lame_duck_check_interval {
partially_hashed_commit.scatter_padding(base_padding_specifier + index_in_interval);
if hash_spec.matches(&partially_hashed_commit.current_hash()) {
return Some(GitCommit::new(processed_commit.commit()));
}
}
if lame_duck_cancel_signal.load(Ordering::Relaxed) {
break;
}
}
None
}
#[cfg(feature = "opencl")]
fn search_with_gpu(self) -> ocl::Result<Option<GitCommit<H>>> {
let HashSearchWorker {
search_space,
hash_spec,
mut processed_commit,
..
} = self;
let mut partially_hashed_commit = processed_commit.as_partially_hashed_commit::<H>();
let num_threads = *[
hash_spec.estimated_attempts_needed().saturating_mul(4),
search_space.end - search_space.start,
1 << 22,
]
.iter()
.min()
.unwrap() as usize;
assert!(num_threads < u32::MAX as usize);
let devices = TypeFlags(DeviceType::GPU).to_device_list(Some(Platform::default()))?[0];
let context = Context::builder().devices(devices).build()?;
let queue = Queue::new(&context, devices, None)?;
let mut successful_match_receiver_host_handle = [u32::MAX];
let successful_match_receiver = Buffer::builder()
.queue(queue.clone())
.len(1)
.flags(MemFlags::READ_WRITE)
.copy_host_slice(&successful_match_receiver_host_handle)
.build()?;
const BASE_PADDING_SPECIFIER_ARG: &str = "base_padding_specifier";
let kernel = Kernel::builder()
.name("scatter_padding_and_find_match")
.program(
&Program::builder()
.src(H::KERNEL)
.cmplr_opt("-Werror")
.build(&context)?,
)
.arg(
&Buffer::builder()
.queue(queue.clone())
.len(hash_spec.data.as_ref().len())
.flags(MemFlags::READ_ONLY)
.copy_host_slice(hash_spec.data.as_ref())
.build()?,
)
.arg(
&Buffer::builder()
.queue(queue.clone())
.len(hash_spec.mask.as_ref().len())
.flags(MemFlags::READ_ONLY)
.copy_host_slice(hash_spec.mask.as_ref())
.build()?,
)
.arg(
&Buffer::builder()
.queue(queue.clone())
.len(partially_hashed_commit.intermediate_state.as_ref().len())
.flags(MemFlags::READ_ONLY)
.copy_host_slice(partially_hashed_commit.intermediate_state.as_ref())
.build()?,
)
.arg_named(BASE_PADDING_SPECIFIER_ARG, 0u64) // filled in later
.arg(
&Buffer::builder()
.queue(queue.clone())
.len(partially_hashed_commit.dynamic_blocks.len())
.flags(MemFlags::READ_ONLY)
.copy_host_slice(
&partially_hashed_commit
.dynamic_blocks
.iter()
.map(|&block| encode_into_opencl_vector::<H>(block))
.collect::<Vec<_>>(),
)
.build()?,
)
.arg(partially_hashed_commit.dynamic_blocks.len() as u64)
.arg(&successful_match_receiver)
.queue(queue)
.global_work_size(num_threads)
.build()?;
for base_padding_specifier in search_space.step_by(num_threads) {
kernel.set_arg(BASE_PADDING_SPECIFIER_ARG, base_padding_specifier)?;
// SAFETY: The OpenCL scripts are optimistically assumed to have no memory safety issues
unsafe {
kernel.enq()?;
}
successful_match_receiver
.read(&mut successful_match_receiver_host_handle[..])
.enq()?;
if successful_match_receiver_host_handle[0] != u32::MAX {
let successful_padding_specifier =
base_padding_specifier + (successful_match_receiver_host_handle[0] as u64);
partially_hashed_commit.scatter_padding(successful_padding_specifier);
assert!(
hash_spec.matches(&partially_hashed_commit.current_hash()),
"\
A GPU search reported a commit with a successful match, but when that \
commit was hashed in postprocessing, it didn't match the desired spec. \
This is a bug. The most likely explanation is that the two implementations of \
`scatter_padding` in Rust and OpenCL (or the implementations of SHA1/SHA256) have diverged \
from each other.\n\npartial commit:\n\t{:?}\ndesired hash spec:\n\t{:?}\ncommit hash \
produced during postprocessing:{:?}\n\tpadding specifier: {}",
partially_hashed_commit,
hash_spec,
partially_hashed_commit.current_hash(),
successful_padding_specifier,
);
return Ok(Some(GitCommit::new(processed_commit.commit())));
}
}
Ok(None)
}
}
impl ProcessedCommit {
const DYNAMIC_PADDING_LENGTH: usize = 48;
/// See the comment above the definition of `ProcessedCommit` for details on how
/// the data layout.
fn new(original_commit: &[u8]) -> Self {
let padding_insertion_point = Self::get_padding_insertion_point(original_commit);
// If the commit message already has spaces or tabs where we're putting padding, the most
// likely explanation is that the user has run lucky-commit on this commit before. To prevent
// commits from repeatedly growing after lucky-commit is run on them, omit the old padding
// rather than piling onto it.
let replaceable_padding_size = original_commit[padding_insertion_point..]
.iter()
.take_while(|&&byte| byte == b' ' || byte == b'\t')
.count();
// Use enough static padding to pad to a multiple of 64
let static_padding_length = Self::compute_static_padding_length(
padding_insertion_point,
original_commit.len() - replaceable_padding_size + Self::DYNAMIC_PADDING_LENGTH,
);
let commit_length = original_commit.len() - replaceable_padding_size
+ static_padding_length
+ Self::DYNAMIC_PADDING_LENGTH;
// Git commit header
let mut data = format!("commit {}\0", commit_length).into_bytes();
let commit_range = data.len()..(data.len() + commit_length);
// First part of commit
data.extend(&original_commit[..padding_insertion_point]);
// Static padding
data.resize(data.len() + static_padding_length, b' ');
assert_eq!(data.len() % 64, 0);
let num_static_blocks = data.len() / 64;
// Dynamic padding, initialized to tabs for now
data.resize(data.len() + Self::DYNAMIC_PADDING_LENGTH, b'\t');
// Second part of commit
data.extend(&original_commit[padding_insertion_point + replaceable_padding_size..]);
assert_eq!(data.len(), commit_range.end);
// SHA finalization padding
data.extend(sha_finalization_padding(data.len()));
assert_eq!(data.len() % 64, 0);
Self {
data: data.into_boxed_slice(),
commit_range,
num_static_blocks,
}
}
/// Finds the index at which static and dynamic padding should be inserted into a commit.
///
/// If the commit has a GPG signature (detected by the presence of "-----END PGP SIGNATURE-----"
/// after a line that starts with "gpgsig "), then add the padding whitespace immediately after
/// the text "-----END PGP SIGNATURE-----".
/// Otherwise, add the padding whitespace right before the end of the commit message.
///
/// To save time hashing, we want the padding to be as close to the end of the commit
/// as possible. However, if a signature is present, modifying the commit message would make
/// the signature invalid.
fn get_padding_insertion_point(commit: &[u8]) -> usize {
// Check if the commit has a signature header before the start of the commit message
let insertion_point_plus_preexisting_padding = (0..commit.len())
.take_while(|&i| !commit[i..].starts_with(b"\n\n"))
.find(|&i| {
commit[i..].starts_with(b"\ngpgsig ")
|| commit[i..].starts_with(b"\ngpgsig-sha256 ")
})
.map(|i| i + 1)
// If so, put the padding right at the end of that header
.and_then(|signature_header_start_index| {
(signature_header_start_index..commit.len())
.find(|&i| commit[i..].starts_with(b"\n") && !commit[i..].starts_with(b"\n "))
})
.unwrap_or(commit.len());
return insertion_point_plus_preexisting_padding
- commit[..insertion_point_plus_preexisting_padding]
.iter()
.rev()
.take_while(|&&byte| byte == b' ' || byte == b'\t' || byte == b'\n')
.count();
}
/// Returns the smallest nonnegative integer `static_padding_length` such that:
/// static_padding_length
/// + commit_length_before_static_padding
/// + 8
/// + (number of digits in the base10 representation of
/// commit_length_excluding_static_padding + static_padding_length)
/// is a multiple of 64.
///
/// The 8 comes from the length of the word `commit`, plus a space and a null character, in
/// git's commit hashing format.
fn compute_static_padding_length(
commit_length_before_static_padding: usize,
commit_length_excluding_static_padding: usize,
) -> usize {
let compute_alignment = |padding_len: usize| {
(format!(
"commit {}\0",
commit_length_excluding_static_padding + padding_len
)
.len()
+ commit_length_before_static_padding
+ padding_len)
% 64
};
let prefix_length_estimate = format!("commit {}\0", commit_length_excluding_static_padding)
.len()
+ commit_length_before_static_padding;
let initial_padding_length_guess = (64 - prefix_length_estimate % 64) % 64;
let static_padding_length = if compute_alignment(initial_padding_length_guess) == 0 {
initial_padding_length_guess
} else if compute_alignment(initial_padding_length_guess - 1) == 0 {
initial_padding_length_guess - 1
} else {
initial_padding_length_guess + 63
};
assert_eq!(compute_alignment(static_padding_length), 0);
debug_assert!((0..static_padding_length).all(|len| compute_alignment(len) != 0));
static_padding_length
}
fn commit(&self) -> &[u8] {
&self.data[self.commit_range.clone()]
}
fn as_partially_hashed_commit<H: GitHashFn>(&mut self) -> PartiallyHashedCommit<H> {
let (static_blocks, dynamic_blocks) =
as_chunks_mut::<H>(&mut self.data[..]).split_at_mut(self.num_static_blocks);
let mut intermediate_state = H::INITIAL_STATE;
H::compress(&mut intermediate_state, static_blocks);
PartiallyHashedCommit {
intermediate_state,
dynamic_blocks,
}
}
}
impl<'a, H: GitHashFn> PartiallyHashedCommit<'a, H> {
#[inline(always)]
fn dynamic_padding_mut(&mut self) -> &mut [u8] {
&mut self.dynamic_blocks[0].as_mut()[..48]
}
// This should be kept in sync with the OpenCL `arrange_padding_block` implementation.
#[inline(always)]
fn scatter_padding(&mut self, padding_specifier: u64) {
// The 256 unique strings of length 8 which contain only ' ' and '\t'.
// These are computed at compile-time to allow them to be copied quickly.
static PADDING_CHUNKS: [[u8; 8]; 256] = {
let mut padding_chunks = [[0; 8]; 256];
let mut i = 0;
while i < 256 {
let mut j = 0;
while j < 8 {
padding_chunks[i][j] = if i & (0x80 >> j) == 0 { b' ' } else { b'\t' };
j += 1;
}
i += 1;
}
padding_chunks
};
self.dynamic_padding_mut()
.chunks_exact_mut(8)
.zip(padding_specifier.to_le_bytes().iter())
.for_each(|(padding_chunk, &padding_specifier_byte)| {
// An padding specifier is represented by an integer in the range [0, 2 ** 48).
// The 48-byte dynamic padding string is mapped from the 48-bit specifier such that
// each byte of padding is a [space/tab] if the corresponding little-endian bit of
// the specifier is a [0/1], respectively.
padding_chunk.copy_from_slice(&PADDING_CHUNKS[padding_specifier_byte as usize]);
})
}
#[inline(always)]
fn current_hash(&self) -> H::State {
let mut hash = self.intermediate_state;
H::compress(&mut hash, self.dynamic_blocks);
hash
}
}
impl<H: GitHashFn> HashSpec<H> {
#[inline(always)]
fn matches(&self, hash: &H::State) -> bool {
hash.as_ref()
.iter()
.zip(self.mask.as_ref().iter())
.map(|(&hash_word, &mask_word)| hash_word & mask_word)
.zip(self.data.as_ref().iter())
.all(|(masked_hash_word, &hash_spec_word)| masked_hash_word == hash_spec_word)
}
#[cfg(feature = "opencl")]
fn estimated_attempts_needed(&self) -> u64 {
2u64.saturating_pow(
self.mask
.as_ref()
.iter()
.map(|word| word.count_ones())
.sum(),
)
}
}
impl<H: GitHashFn> FromStr for HashSpec<H> {
type Err = ParseHashSpecErr;
/// Parses a HashSpec from a string. The string must only contain hex characters (0-9, a-f, A-F), indicating the hex
/// value that the hash should have at a given position, or `_`, indicating that the hash can have any value at the given
/// position. All positions in the hash beyond the length of the string are treated as unspecified (equivalent to if the
/// string was right-padded with `_`).
fn from_str(prefix_string: &str) -> Result<Self, Self::Err> {
let max_hex_character_length = mem::size_of::<H::State>() * 2;
if prefix_string.chars().count() > max_hex_character_length {
return Err(ParseHashSpecErr::TooLong);
}
let mut parsed_hash_spec = HashSpec::<H> {
// Zero-initialize the data and mask
data: H::State::default(),
mask: H::State::default(),
};
prefix_string
.chars()
// Pad the input string out to the length of a hash
.chain(iter::repeat('_'))
.take(max_hex_character_length)
// Split it into 8-hex-character chunks
.collect::<Vec<_>>()
.chunks(8)
// Associate each 8-hex-character chunk with corresponding 32-bit word of the hash spec
.zip(parsed_hash_spec.data.as_mut())
.zip(parsed_hash_spec.mask.as_mut())
.try_for_each(|((hash_spec_chunk, data_word), mask_word)| {
hash_spec_chunk
.iter()
.zip((0..32).step_by(4).rev())
.try_for_each(|(&hash_spec_character, slot_bit_offset)| {
// Parse each hex character of the input string and write it to the appropriate slots of the hash spec.
if let Some(hex_character_value) = hash_spec_character.to_digit(16) {
*data_word |= hex_character_value << slot_bit_offset;
*mask_word |= 0xf << slot_bit_offset;
} else if hash_spec_character != '_' {
// The '_' character in a hash spec is allowed as an "any value is allowed here" placeholder
// (corresponds to a 0 in both the data slot and the mask slot). All other non-hex characters are
// disallowed.
return Err(ParseHashSpecErr::InvalidCharacter(hash_spec_character));
}
Ok(())
})
})?;
Ok(parsed_hash_spec)
}
}
impl<H: GitHashFn> Default for HashSpec<H> {
fn default() -> Self {
"0000000".parse().unwrap()
}
}
impl Error for ParseHashSpecErr {}
impl Display for ParseHashSpecErr {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
match *self {
Self::TooLong => write!(f, "hash spec can't be longer than an actual hash"),
Self::InvalidCharacter(c) => write!(f, "hash spec contains invalid character '{}' (only hex characters and underscores are allowed)", c),
}
}
}
impl Debug for ParseHashSpecErr {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
<Self as Display>::fmt(self, f)
}
}
impl<H: GitHashFn> GitCommit<H> {
/// Constructs a GitCommit from the given commit data. The data is assumed to be in
/// git's object format, but this is not technically required.
pub fn new(commit: &[u8]) -> Self {
Self {
object: commit.to_vec(),
hash: {
let mut state = H::INITIAL_STATE;
let commit_header = format!("commit {}\0", commit.len()).into_bytes();
let commit_data_length = commit_header.len() + commit.len();
H::compress(
&mut state,
as_chunks_mut::<H>(
commit_header
.into_iter()
.chain(commit.iter().cloned())
.chain(sha_finalization_padding(commit_data_length))
.collect::<Vec<_>>()
.as_mut(),
),
);
state
},
}
}
/// The git object data for this commit
pub fn object(&self) -> &[u8] {
&self.object
}
/// The hash of this commit, as a hex string
pub fn hex_hash(&self) -> String {
self.hash
.as_ref()
.iter()
.map(|word| format!("{:08x}", word))
.collect()
}
}
impl<H: GitHashFn> Debug for GitCommit<H> {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
write!(
f,
"GitCommit {{ object: {:?}, hash: {:?} }}",
String::from_utf8_lossy(&self.object),
self.hex_hash()
)
}
}
#[cfg(feature = "opencl")]
/// Reinterpret a block with 64 8-bit integers as an OpenCL vector with 16 32-bit big-endian integers
fn encode_into_opencl_vector<H: GitHashFn>(data: H::Block) -> Uint16 {
let words: [u32; 16] = data
.as_ref()
.chunks(4)
.map(|chunk| u32::from_be_bytes(chunk.try_into().unwrap()))
.collect::<Vec<_>>()
.try_into()
.unwrap();
words.into()
}
// This is a modified implementation of std::slice::as_chunks_mut. It's copied because the
// standard library function is not yet stable. As a local safety invariant, `Block` is expected
// to be layout-identical to `[u8; 64]`. (It's a generic parameter because the `GenericArray` subdependency
// could technically end up being at different versions between the sha1 and sha2 crates, which would cause
// compile errors if the sha1 version of `GenericArray` gets passed to sha2 methods.
fn as_chunks_mut<H: GitHashFn>(slice: &mut [u8]) -> &mut [H::Block] {
assert_eq!(mem::size_of::<H::Block>(), 64);
assert_eq!(mem::align_of::<H::Block>(), mem::align_of::<u8>());
assert_eq!(slice.len() % mem::size_of::<H::Block>(), 0);
// SAFETY:
// * All of the bytes in the slice are initialized, and the alignment of u8 and [u8; 64]
// are the same.
// * The slice length is a multiple of 64, and so the slice's pointer points to
// the same number of elements as the resulting pointer.
// * Since `slice` is mutable, its values aren't accessible anywhere else during its lifetime.
// * Since the length of the new slice is smaller, it can't overflow beyond isize::MAX.
unsafe {
std::slice::from_raw_parts_mut(
slice.as_mut_ptr().cast(),
slice.len() / mem::size_of::<H::Block>(),
)
}
}
// Finalization padding that gets added to the end of data being hashed with sha1 or sha256
// (the padding happens to be the same for both)
fn sha_finalization_padding(data_length: usize) -> impl IntoIterator<Item = u8> {
iter::once(0x80)
.chain(iter::repeat(0).take((55 - data_length as isize).rem_euclid(64) as usize))
.chain(<[u8; 8]>::into_iter((data_length as u64 * 8).to_be_bytes()))
}
#[cfg(test)]
mod tests;