1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535
use crate::hash_path::shard::ShardStrategy;
use crate::hash_path::shard::SHARDEND;
use crate::prelude::*;
use holochain_wasmer_guest::*;
use holochain_zome_types::link::LinkTag;
use std::str::FromStr;
use validate::RequiredValidationType;
/// Allows for "foo.bar.baz" to automatically move to/from ["foo", "bar", "baz"] components.
/// Technically it's moving each string component in as bytes.
/// If this is a problem for you simply build the components yourself as a Vec<Vec<u8>>.
///
/// See `impl From<String> for Path` below.
pub const DELIMITER: &str = ".";
/// All paths use the same link tag and entry def id.
/// Different pathing schemes/systems/implementations should namespace themselves by their path
/// components rather than trying to layer different link namespaces over the same path components.
/// Similarly there is no need to define different entry types for different pathing strategies.
/// The DHT_PREFIX ends up as both the prefix of the link tags and also in the
/// `PathEntry` struct itself to mitigate collisions on the DHT.
pub const DHT_PREFIX: u8 = 0;
/// Each path component is arbitrary bytes to be hashed together in a predictable way when the path
/// is hashed to create something that can be linked and discovered by all DHT participants.
#[derive(
Clone, PartialEq, Debug, Default, serde::Deserialize, serde::Serialize, SerializedBytes,
)]
#[repr(transparent)]
pub struct Component(#[serde(with = "serde_bytes")] Vec<u8>);
impl Component {
pub fn new(v: Vec<u8>) -> Self {
Self(v)
}
}
/// Wrap bytes.
impl From<Vec<u8>> for Component {
fn from(v: Vec<u8>) -> Self {
Self(v)
}
}
/// Access bytes.
impl AsRef<[u8]> for Component {
fn as_ref(&self) -> &[u8] {
self.0.as_ref()
}
}
/// Unwrap bytes.
impl From<Component> for Vec<u8> {
fn from(component: Component) -> Self {
component.0
}
}
/// Build a component from a String.
///
/// For many simple use cases we can construct a path out of a string similar to a URI.
/// We represent this using the utf32 bytes rather than the utf8 bytes for the chars in the string
/// which gives us a fixed width encoding for strings, which gives us a clean/easy way to support
/// sharding based on strings by iterating over u32s rather than deciding what to do with variable
/// width u8 or u16 characters.
///
/// IMPORTANT: if you are not using sharding and make heavy use of `Path` then
/// consider building your `Component` directly from `my_string.as_bytes()` to
/// achieve much more compact utf8 representations of each `Component`.
impl From<&str> for Component {
fn from(s: &str) -> Self {
let bytes: Vec<u8> = s
.chars()
.flat_map(|c| (c as u32).to_le_bytes().to_vec())
.collect();
Self::from(bytes)
}
}
/// Alias From<&str>
impl From<&String> for Component {
fn from(s: &String) -> Self {
Self::from(s.as_str())
}
}
/// Alias From<&str>
impl From<String> for Component {
fn from(s: String) -> Self {
Self::from(s.as_str())
}
}
/// Restoring a [ `String` ] from a [ `Component` ] requires [ `Vec<u8>` ] to [ `u32` ] to utf8 handling.
impl TryFrom<&Component> for String {
type Error = SerializedBytesError;
fn try_from(component: &Component) -> Result<Self, Self::Error> {
if component.as_ref().len() % 4 != 0 {
return Err(SerializedBytesError::Deserialize(format!(
"attempted to create u32s from utf8 bytes of length not a factor of 4: length {}",
component.as_ref().len()
)));
}
let (chars, _, error) = component
.as_ref()
.iter()
// @todo this algo seems a bit inefficient but also i'm not sure how much that
// matters in reality, maybe a premature optimisation to do anything else
.fold(
(vec![], vec![], None),
|(mut chars, mut build, mut error), b| {
if error.is_none() {
build.push(*b);
if build.len() == std::mem::size_of::<u32>() {
// Convert the build vector into 4 le_bytes for the u32.
// This is an unwrap because we already check the total length above.
let le_bytes = build[0..std::mem::size_of::<u32>()].try_into().unwrap();
let u = u32::from_le_bytes(le_bytes);
match std::char::from_u32(u) {
Some(c) => {
chars.push(c);
build = vec![];
}
None => {
error = Some(Err(SerializedBytesError::Deserialize(format!(
"unknown char for u32: {}",
u
))));
}
}
}
}
(chars, build, error)
},
);
match error {
Some(error) => error,
None => Ok(chars.iter().collect::<String>()),
}
}
}
/// A [ `Path` ] is a vector of [ `Component` ].
/// It represents a single traversal of a tree structure down to some arbitrary point.
/// The main intent is that we can recursively walk back up the tree, hashing, committing and
/// linking each sub-path along the way until we reach the root.
/// At this point it is possible to follow DHT links from the root back up the path.
/// i.e. the ahead-of-time predictability of the hashes of a given path allows us to travel "up"
/// the tree and the linking functionality of the holochain DHT allows us to travel "down" the tree
/// after at least one DHT participant has followed the path "up".
/// Note that the `Path` is not literally committed and/or linked from/to as
/// base and target. For this the [ `PathEntry` ] exists, which achieves a
/// constant size for the DHT representation of each node of the `Path`.
#[derive(
Clone, Debug, PartialEq, Default, serde::Deserialize, serde::Serialize, SerializedBytes,
)]
#[repr(transparent)]
pub struct Path(Vec<Component>);
entry_def!(Path EntryDef {
id: "hdk.path".into(),
crdt_type: CrdtType,
required_validations: RequiredValidations::default(),
visibility: EntryVisibility::Public,
required_validation_type: RequiredValidationType::default(),
});
/// A [ `PathEntry` ] is the hash of a [ `Path` ] and the [ `DHT_PREFIX` ].
/// This is what is committed and shared on the DHT to build links off as their
/// base and target. If we committed the `Path` directly then the size of each
/// node entry content would be the size of all the components of the path.
/// Given that `ensure` populates all the ancestor nodes committing [ A, B, C ]
/// would create entries with content [ A ], [ A, B ], [ A, B, C ]. For deep
/// paths, or paths with a large component (in bytes) at any node, this would
/// create a lot of redundant data in every descendent entry.
/// Instead, we commit a `PathEntry` so each node is constant size, just the
/// hash of the full `Path` up to that point. This means that committing
/// `PathEntry` instead of `Path` for `[A, B, C]` results in entries with
/// content [ HashA ], [ HashAB ], [ HashABC ]. Note that if A + B + C is much
/// less than the size of a holochain hash (~40 bytes) then this approach is
/// worse than simply committing the `Path` but in practise this is often not
/// the case, and `PathEntry` becomes a more scalable generalised solution.
#[derive(Clone, Debug, PartialEq, serde::Deserialize, serde::Serialize, SerializedBytes)]
pub struct PathEntry(#[serde(with = "serde_bytes")] Vec<u8>);
impl PathEntry {
pub fn new(entry_hash: EntryHash) -> Self {
Self(
[DHT_PREFIX]
.iter()
.chain(entry_hash.get_raw_32())
.cloned()
.collect(),
)
}
}
entry_def!(PathEntry EntryDef {
id: "hdk.path_entry".into(),
crdt_type: CrdtType,
required_validations: RequiredValidations::default(),
visibility: EntryVisibility::Public,
required_validation_type: RequiredValidationType::default(),
});
/// Wrap components vector.
impl From<Vec<Component>> for Path {
fn from(components: Vec<Component>) -> Self {
Self(components)
}
}
/// Unwrap components vector.
impl From<Path> for Vec<Component> {
fn from(path: Path) -> Self {
path.0
}
}
/// Access components vector.
impl AsRef<Vec<Component>> for Path {
fn as_ref(&self) -> &Vec<Component> {
self.0.as_ref()
}
}
/// Split a string path out into a vector of components.
/// This allows us to construct pseudo-URI-path-things as strings.
/// It is a simpler scheme than URLs and file paths.
/// Leading and trailing slashes are ignored as are duplicate dots and the empty string leads
/// to a path with zero length (no components).
///
/// e.g. all the following result in the same components as `vec!["foo", "bar"]` (as bytes)
/// - foo.bar
/// - foo.bar.
/// - .foo.bar
/// - .foo.bar.
/// - foo..bar
///
/// There is no normalisation of paths, e.g. to guarantee a specific root component exists, at this
/// layer so there is a risk that there are hash collisions with other data on the DHT network if
/// some disambiguation logic is not included in higher level abstractions.
///
/// This supports sharding strategies from a small inline DSL.
/// Start each component with <width>:<depth># to get shards out of the string.
///
/// e.g.
/// - foo.barbaz => normal path as above ["foo", "barbaz"]
/// - foo.1:3#barbazii => width 1, depth 3, ["foo", "b", "a", "r", "barbazii"]
/// - foo.2:3#barbazii => width 2, depth 3, ["foo", "ba", "rb", "az", "barbazii"]
///
/// Note that this all works because the components and sharding for strings maps to fixed-width
/// utf32 bytes under the hood rather than variable width bytes.
impl From<&str> for Path {
fn from(s: &str) -> Self {
Self(
s.split(DELIMITER)
.filter(|s| !s.is_empty())
.flat_map(|s| match ShardStrategy::from_str(s) {
// Handle a strategy if one is found.
Ok(strategy) => {
let (_strategy, component) = s.split_at(s.find(SHARDEND).unwrap());
let component = component.trim_start_matches(SHARDEND);
let shard_path = Path::from((&strategy, component));
let mut shard_components: Vec<Component> = shard_path.into();
shard_components.push(Component::from(component));
shard_components
}
// No strategy. Use the component directly.
Err(_) => vec![Component::from(s)],
})
.collect(),
)
}
}
/// Alias From<&str>
impl From<&String> for Path {
fn from(s: &String) -> Self {
Self::from(s.as_str())
}
}
/// Alias From<&str>
impl From<String> for Path {
fn from(s: String) -> Self {
Self::from(s.as_str())
}
}
impl Path {
pub fn path_entry(&self) -> ExternResult<PathEntry> {
Ok(PathEntry::new(hash_entry(self)?))
}
/// What is the hash for the current [ `Path` ]?
pub fn path_entry_hash(&self) -> ExternResult<holo_hash::EntryHash> {
hash_entry(self.path_entry()?)
}
/// Does an entry exist at the hash we expect?
pub fn exists(&self) -> ExternResult<bool> {
Ok(get(self.path_entry_hash()?, GetOptions::content())?.is_some())
}
/// Recursively touch this and every parent that doesn't exist yet.
pub fn ensure(&self) -> ExternResult<()> {
if !self.exists()? {
create_entry(self.path_entry()?)?;
if let Some(parent) = self.parent() {
parent.ensure()?;
create_link(
parent.path_entry_hash()?,
self.path_entry_hash()?,
LinkTag::new(
[DHT_PREFIX]
.iter()
.chain(
match self.leaf() {
None => <Vec<u8>>::with_capacity(0),
Some(component) => {
UnsafeBytes::from(SerializedBytes::try_from(component)?)
.into()
}
}
.iter(),
)
.cloned()
.collect::<Vec<u8>>(),
),
)?;
}
}
Ok(())
}
/// The parent of the current path is simply the path truncated one level.
pub fn parent(&self) -> Option<Path> {
if self.as_ref().len() > 1 {
let parent_vec: Vec<Component> = self.as_ref()[0..self.as_ref().len() - 1].to_vec();
Some(parent_vec.into())
} else {
None
}
}
/// Touch and list all the links from this path to paths below it.
/// Only returns links between paths, not to other entries that might have their own links.
pub fn children(&self) -> ExternResult<Vec<holochain_zome_types::link::Link>> {
Self::ensure(self)?;
let mut unwrapped = get_links(
self.path_entry_hash()?,
Some(holochain_zome_types::link::LinkTag::new([DHT_PREFIX])),
)?;
// Only need one of each hash to build the tree.
unwrapped.sort_unstable_by(|a, b| a.tag.cmp(&b.tag));
unwrapped.dedup_by(|a, b| a.tag.eq(&b.tag));
Ok(unwrapped)
}
/// Touch and list all the links from this path to paths below it.
/// Same as `Path::children` but returns `Vec<Path>` rather than `Vec<Link>`.
/// This is more than just a convenience. In general it's not possible to
/// construct a full `Path` from a child `Link` alone as only a single
/// `Component` is encoded into the link tag. To build a full child path
/// the parent path + child link must be combined, which this function does
/// to produce each child, by using `&self` as that parent.
pub fn children_paths(&self) -> ExternResult<Vec<Self>> {
let children = self.children()?;
let components: ExternResult<Vec<Option<Component>>> = children
.into_iter()
.map(|link| {
let component_bytes = &link.tag.0[1..];
if component_bytes.is_empty() {
Ok(None)
} else {
Ok(Some(
SerializedBytes::from(UnsafeBytes::from(component_bytes.to_vec()))
.try_into()
.map_err(WasmError::Serialize)?,
))
}
})
.collect();
Ok(components?
.into_iter()
.map(|maybe_component| {
let mut new_path = self.clone();
if let Some(component) = maybe_component {
new_path.append_component(component);
}
new_path
})
.collect())
}
pub fn children_details(&self) -> ExternResult<holochain_zome_types::link::LinkDetails> {
Self::ensure(self)?;
get_link_details(
self.path_entry_hash()?,
Some(holochain_zome_types::link::LinkTag::new([DHT_PREFIX])),
)
}
/// Mutate this `Path` into a child of itself by appending a `Component`.
pub fn append_component(&mut self, component: Component) {
self.0.push(component);
}
/// Accessor for the last `Component` of this `Path`.
/// This can be thought of as the leaf of the implied tree structure of
/// which this `Path` is one branch of.
pub fn leaf(&self) -> Option<&Component> {
self.0.last()
}
}
#[test]
#[cfg(test)]
fn hash_path_delimiter() {
assert_eq!(".", DELIMITER,);
}
#[test]
#[cfg(test)]
fn hash_path_component() {
use ::fixt::prelude::*;
let bytes: Vec<u8> = U8Fixturator::new(Unpredictable).take(5).collect();
let component = Component::from(bytes.clone());
assert_eq!(bytes, component.as_ref(),);
assert_eq!(
Component::from(vec![102, 0, 0, 0, 111, 0, 0, 0, 111, 0, 0, 0]),
Component::from("foo"),
);
assert_eq!(
String::try_from(&Component::from(vec![
102, 0, 0, 0, 111, 0, 0, 0, 111, 0, 0, 0
]))
.unwrap(),
String::from("foo"),
);
assert_eq!(
String::try_from(&Component::from(vec![1])),
Err(SerializedBytesError::Deserialize(
"attempted to create u32s from utf8 bytes of length not a factor of 4: length 1".into()
)),
);
assert_eq!(
String::try_from(&Component::from(vec![9, 9, 9, 9])),
Err(SerializedBytesError::Deserialize(
"unknown char for u32: 151587081".into()
)),
);
}
#[test]
#[cfg(test)]
fn hash_path_path() {
use ::fixt::prelude::*;
let components: Vec<Component> = {
let mut vec = vec![];
for _ in 0..10 {
let bytes: Vec<u8> = U8Fixturator::new(Unpredictable).take(10).collect();
vec.push(Component::from(bytes))
}
vec
};
assert_eq!(&components, Path::from(components.clone()).as_ref(),);
for (input, output) in vec![
("", vec![]),
(".", vec![]),
(".foo", vec![Component::from("foo")]),
("foo", vec![Component::from("foo")]),
("foo.", vec![Component::from("foo")]),
(".foo.", vec![Component::from("foo")]),
(
".foo.bar",
vec![Component::from("foo"), Component::from("bar")],
),
(
".foo.bar.",
vec![Component::from("foo"), Component::from("bar")],
),
(
"foo.bar",
vec![Component::from("foo"), Component::from("bar")],
),
(
"foo.bar.",
vec![Component::from("foo"), Component::from("bar")],
),
(
"foo..bar",
vec![Component::from("foo"), Component::from("bar")],
),
(
"foo.1:3#abcdef",
vec![
Component::from("foo"),
Component::from("a"),
Component::from("b"),
Component::from("c"),
Component::from("abcdef"),
],
),
(
"foo.2:3#zzzzzzzzzz",
vec![
Component::from("foo"),
Component::from("zz"),
Component::from("zz"),
Component::from("zz"),
Component::from("zzzzzzzzzz"),
],
),
(
"foo.1:3#abcdef.bar",
vec![
Component::from("foo"),
Component::from("a"),
Component::from("b"),
Component::from("c"),
Component::from("abcdef"),
Component::from("bar"),
],
),
] {
assert_eq!(Path::from(input), Path::from(output),);
}
}