In order to support standard (de)serialization of structs, the
`rust-bitcoin` ecosystem uses the standard `std::io::{Read,Write}`
traits. This works great for environments with `std`, however sadly
the `std::io` module has not yet been added to the `core` crate.
Thus, in `no-std`, the `rust-bitcoin` ecosystem has historically
used the `core2` crate to provide copies of the `std::io` module
without any major dependencies. Sadly, its one dependency,
`memchr`, recently broke our MSRV.
Worse, because we didn't want to take on any excess dependencies
for `std` builds, `rust-bitcoin` has had to have
mutually-exclusive `std` and `no-std` builds. This breaks general
assumptions about how features work in Rust, causing substantial
pain for applications far downstream of `rust-bitcoin` crates.
Here, we add a new `bitcoin_io` crate, making it an unconditional
dependency and using its `io` module in the in-repository crates
in place of `std::io` and `core2::io`. As it is not substantial
additional code, the `hashes` io implementations are no longer
feature-gated.
This doesn't actually accomplish anything on its own, only adding
the new crate which still depends on `core2`.
71454d438a Use hash_type macro for sha512::Hash (Tobin C. Harding)
d51c1857fd sha512: Move from_engine functions (Tobin C. Harding)
Pull request description:
This PR does not introduce any logic changes.
- Patch 1 is a code move.
- Patch 2 uses the `hash_type!` macro to define the `sha512::Hash` type.
ACKs for top commit:
Kixunil:
ACK 71454d438a
apoelstra:
ACK 71454d438a
Tree-SHA512: c0148391fbea3602f0c52e5e08883faac6b5cb3f75ae62bfb53b1d2762e28871d349b3d3fb589f59d8bf2912dd63934f8f9a6fe6390afd378e5391eb2c91c237
Make the `sha512_256` module use similar code layout to the other hash
modules by putting the call to `hash_type` at the top followed by the
`from_engine` function.
Code move only, no other changes.
Currently we are defining the `sha512::Hash` type manually instead of
using the `hash_type` macro.
The generated code using the macro is identical to that without
it (although I didn't actually look at the generated code :)
On our way to v1.0.0 we are defining a standard for our error types,
this includes:
- Uses the following derives (unless not possible, usually because of `io::Error`)
`#[derive(Debug, Clone, PartialEq, Eq)]`
- Has `non_exhaustive` unless we really know we can commit to not adding
anything.
Furthermore, we are trying to make the codebase easy to read. Error code
is write-once-read-many (well it should be) so if we make all the error
code super uniform the users can flick to an error and quickly see what
it includes. In an effort to achieve this I have made up a style and
over recent times have change much of the error code to that new style,
this PR audits _all_ error types in the code base and enforces the
style, specifically:
- Is layed out: definition, [impl block], Display impl, error::Error impl, From impls
- `error::Error` impl matches on enum even if it returns `None` for all variants
- Display/Error impls import enum variants locally
- match uses *self and `ref e`
- error::Error variants that return `Some` come first, `None` after
Re: non_exhaustive
To make dev and review easier I have added `non_exhaustive` to _every_
error type. We can then remove it error by error as we see fit. This is
because it takes a bit of thinking to do and review where as this patch
should not take much brain power to review.
f2c5f19557 Introduce the `small-hash` feature for `bitcoin_hashes` (Alekos Filini)
Pull request description:
When enabled this feature swaps the hash implementation of sha512, sha256 and ripemd160 for a smaller (but also slower) one.
On embedded processors (Cortex-M4) it can lead to up to a 52% size reduction, from around 37KiB for just the `process_block` methods of the three hash functions to 17.8KiB.
The following numbers were collected on `aarch64-unknown-linux-gnu` with `cargo 1.72.0-nightly`.
## Original
```
RUSTFLAGS='--cfg=bench -C opt-level=z' cargo bench
```
```
test hash160::benches::hash160_10 ... bench: 33 ns/iter (+/- 1) = 303 MB/s
test hash160::benches::hash160_1k ... bench: 2,953 ns/iter (+/- 187) = 346 MB/s
test hash160::benches::hash160_64k ... bench: 188,480 ns/iter (+/- 11,595) = 347 MB/s
test hmac::benches::hmac_sha256_10 ... bench: 33 ns/iter (+/- 2) = 303 MB/s
test hmac::benches::hmac_sha256_1k ... bench: 2,957 ns/iter (+/- 104) = 346 MB/s
test hmac::benches::hmac_sha256_64k ... bench: 192,022 ns/iter (+/- 6,407) = 341 MB/s
test ripemd160::benches::ripemd160_10 ... bench: 25 ns/iter (+/- 1) = 400 MB/s
test ripemd160::benches::ripemd160_1k ... bench: 2,288 ns/iter (+/- 93) = 447 MB/s
test ripemd160::benches::ripemd160_64k ... bench: 146,823 ns/iter (+/- 1,102) = 446 MB/s
test sha1::benches::sha1_10 ... bench: 41 ns/iter (+/- 0) = 243 MB/s
test sha1::benches::sha1_1k ... bench: 3,844 ns/iter (+/- 70) = 266 MB/s
test sha1::benches::sha1_64k ... bench: 245,854 ns/iter (+/- 10,158) = 266 MB/s
test sha256::benches::sha256_10 ... bench: 35 ns/iter (+/- 0) = 285 MB/s
test sha256::benches::sha256_1k ... bench: 3,063 ns/iter (+/- 15) = 334 MB/s
test sha256::benches::sha256_64k ... bench: 195,729 ns/iter (+/- 2,880) = 334 MB/s
test sha256d::benches::sha256d_10 ... bench: 34 ns/iter (+/- 1) = 294 MB/s
test sha256d::benches::sha256d_1k ... bench: 3,071 ns/iter (+/- 107) = 333 MB/s
test sha256d::benches::sha256d_64k ... bench: 188,614 ns/iter (+/- 8,101) = 347 MB/s
test sha512::benches::sha512_10 ... bench: 21 ns/iter (+/- 0) = 476 MB/s
test sha512::benches::sha512_1k ... bench: 1,714 ns/iter (+/- 36) = 597 MB/s
test sha512::benches::sha512_64k ... bench: 110,084 ns/iter (+/- 3,637) = 595 MB/s
test sha512_256::benches::sha512_256_10 ... bench: 22 ns/iter (+/- 1) = 454 MB/s
test sha512_256::benches::sha512_256_1k ... bench: 1,822 ns/iter (+/- 70) = 562 MB/s
test sha512_256::benches::sha512_256_64k ... bench: 116,231 ns/iter (+/- 4,745) = 563 MB/s
test siphash24::benches::siphash24_1ki ... bench: 1,072 ns/iter (+/- 41) = 955 MB/s
test siphash24::benches::siphash24_1ki_hash ... bench: 1,102 ns/iter (+/- 42) = 929 MB/s
test siphash24::benches::siphash24_1ki_hash_u64 ... bench: 1,064 ns/iter (+/- 41) = 962 MB/s
test siphash24::benches::siphash24_64ki ... bench: 69,957 ns/iter (+/- 2,712) = 936 MB/
```
```
0000000000005872 t _ZN84_$LT$bitcoin_hashes..ripemd160..HashEngine$u20$as$u20$bitcoin_hashes..HashEngine$GT$5input17hc4800746a9da7ff4E
0000000000007956 t _ZN81_$LT$bitcoin_hashes..sha256..HashEngine$u20$as$u20$bitcoin_hashes..HashEngine$GT$5input17hf49345f65130ce9bE
0000000000008024 t _ZN14bitcoin_hashes6sha2568Midstate10const_hash17h57317bc8012004b4E.llvm.441255102889972912
0000000000010528 t _ZN81_$LT$bitcoin_hashes..sha512..HashEngine$u20$as$u20$bitcoin_hashes..HashEngine$GT$5input17h9bc868d4392bd9acE
```
Total size: 32380 bytes
## With `small-hash` enabled
```
RUSTFLAGS='--cfg=bench -C opt-level=z' cargo bench --features small-hash
```
```
test hash160::benches::hash160_10 ... bench: 52 ns/iter (+/- 3) = 192 MB/s
test hash160::benches::hash160_1k ... bench: 4,817 ns/iter (+/- 286) = 212 MB/s
test hash160::benches::hash160_64k ... bench: 319,572 ns/iter (+/- 11,031) = 205 MB/s
test hmac::benches::hmac_sha256_10 ... bench: 54 ns/iter (+/- 2) = 185 MB/s
test hmac::benches::hmac_sha256_1k ... bench: 4,846 ns/iter (+/- 204) = 211 MB/s
test hmac::benches::hmac_sha256_64k ... bench: 319,114 ns/iter (+/- 4,451) = 205 MB/s
test ripemd160::benches::ripemd160_10 ... bench: 27 ns/iter (+/- 0) = 370 MB/s
test ripemd160::benches::ripemd160_1k ... bench: 2,358 ns/iter (+/- 150) = 434 MB/s
test ripemd160::benches::ripemd160_64k ... bench: 154,573 ns/iter (+/- 3,954) = 423 MB/s
test sha1::benches::sha1_10 ... bench: 41 ns/iter (+/- 1) = 243 MB/s
test sha1::benches::sha1_1k ... bench: 3,700 ns/iter (+/- 243) = 276 MB/s
test sha1::benches::sha1_64k ... bench: 231,039 ns/iter (+/- 13,989) = 283 MB/s
test sha256::benches::sha256_10 ... bench: 51 ns/iter (+/- 3) = 196 MB/s
test sha256::benches::sha256_1k ... bench: 4,823 ns/iter (+/- 182) = 212 MB/s
test sha256::benches::sha256_64k ... bench: 299,960 ns/iter (+/- 17,545) = 218 MB/s
test sha256d::benches::sha256d_10 ... bench: 52 ns/iter (+/- 2) = 192 MB/s
test sha256d::benches::sha256d_1k ... bench: 4,827 ns/iter (+/- 323) = 212 MB/s
test sha256d::benches::sha256d_64k ... bench: 302,844 ns/iter (+/- 15,796) = 216 MB/s
test sha512::benches::sha512_10 ... bench: 34 ns/iter (+/- 1) = 294 MB/s
test sha512::benches::sha512_1k ... bench: 3,002 ns/iter (+/- 123) = 341 MB/s
test sha512::benches::sha512_64k ... bench: 189,767 ns/iter (+/- 10,396) = 345 MB/s
test sha512_256::benches::sha512_256_10 ... bench: 34 ns/iter (+/- 1) = 294 MB/s
test sha512_256::benches::sha512_256_1k ... bench: 2,996 ns/iter (+/- 198) = 341 MB/s
test sha512_256::benches::sha512_256_64k ... bench: 192,024 ns/iter (+/- 8,181) = 341 MB/s
test siphash24::benches::siphash24_1ki ... bench: 1,081 ns/iter (+/- 65) = 947 MB/s
test siphash24::benches::siphash24_1ki_hash ... bench: 1,083 ns/iter (+/- 63) = 945 MB/s
test siphash24::benches::siphash24_1ki_hash_u64 ... bench: 1,084 ns/iter (+/- 63) = 944 MB/s
test siphash24::benches::siphash24_64ki ... bench: 67,237 ns/iter (+/- 4,185) = 974 MB/s
```
```
0000000000005384 t _ZN81_$LT$bitcoin_hashes..sha256..HashEngine$u20$as$u20$bitcoin_hashes..HashEngine$GT$5input17hae341658cf9b880bE
0000000000005608 t _ZN14bitcoin_hashes9ripemd16010HashEngine13process_block17h3276b13f1e9feef8E.llvm.13618235596061801146
0000000000005616 t _ZN14bitcoin_hashes6sha2568Midstate10const_hash17h3e6fbef64c15ee00E.llvm.7326223909590351031
0000000000005944 t _ZN81_$LT$bitcoin_hashes..sha512..HashEngine$u20$as$u20$bitcoin_hashes..HashEngine$GT$5input17h321a237bfbe5c0bbE
```
Total size: 22552 bytes
## Conclusion
On `aarch64` there's overall a ~30% improvement in size, although ripemd160 doesn't really shrink that much (and its performance also aren't impacted much with only a 6% slowdown). sha512 and sha256 instead are almost 40% slower with `small-hash` enabled.
I don't have performance numbers for other architectures, but in terms of size there was an even larger improvements on `thumbv7em-none-eabihf`, with a 52% size reduction overall:
```
Size Crate Name
25.3KiB bitcoin_hashes <bitcoin_hashes[fe467ef2aa3a1470]::sha512::HashEngine as bitcoin_hashes[fe467ef2aa3a1470]::HashEngine>::input
6.9KiB bitcoin_hashes <bitcoin_hashes[fe467ef2aa3a1470]::sha256::HashEngine as bitcoin_hashes[fe467ef2aa3a1470]::HashEngine>::input
4.8KiB bitcoin_hashes <bitcoin_hashes[fe467ef2aa3a1470]::ripemd160::HashEngine as bitcoin_hashes[fe467ef2aa3a1470]::HashEngine>::input
```
vs
```
Size Crate Name
9.5KiB bitcoin_hashes <bitcoin_hashes[974bb476ef905797]::sha512::HashEngine as bitcoin_hashes[974bb476ef905797]::HashEngine>::input
4.5KiB bitcoin_hashes <bitcoin_hashes[974bb476ef905797]::ripemd160::HashEngine>::process_block
3.8KiB bitcoin_hashes <bitcoin_hashes[974bb476ef905797]::sha256::HashEngine as bitcoin_hashes[974bb476ef905797]::HashEngine>::input
```
I'm assuming this is because on more limited architectures the compiler needs to use more instructions to move data in and out of registers (especially for sha512 which ideally would benefit from 64-bit registers), so reusing the code by moving it into functions saves a lot of those instructions.
Also note that the `const_hash` method on `sha256` causes the compiler to emit two independent implementations. I haven't looked into the code yet, maybe there's a way to merge them so that the non-const `process_block` calls into the const fn.
-----
Note: commits are unverified right now because I don't have the keys available, I will sign them after addressing the review comments.
ACKs for top commit:
apoelstra:
ACK f2c5f19557
tcharding:
ACK f2c5f19557
Tree-SHA512: 1d5eb56324c458660e2571e8cf59895dc31dae9c5427c7ed36f8a0e81ca2e9a0f39026f56b6803df03635cc8b66aee3bf5182d51ab8972d169d56bcfec33771c
546c0122d7 Add simd sha256 intrinsics for x86 machines (sanket1729)
Pull request description:
This is my first time dabbling into architecture specific code and simd. The algorithm is a word to word translation of the C code from 4899efc81d/sha256-x86.c .
Some benchmarks:
With simd
```
test sha256::benches::sha256_10 ... bench: 11 ns/iter (+/- 0) = 909 MB/s
test sha256::benches::sha256_1k ... bench: 712 ns/iter (+/- 2) = 1438 MB/s
test sha256::benches::sha256_64k ... bench: 45,597 ns/iter (+/- 189) = 1437 MB/s
```
Without simd
```
test sha256::benches::sha256_10 ... bench: 47 ns/iter (+/- 0) = 212 MB/s
test sha256::benches::sha256_1k ... bench: 4,243 ns/iter (+/- 17) = 241 MB/s
test sha256::benches::sha256_64k ... bench: 271,263 ns/iter (+/- 1,610) = 241 MB/s
```
ACKs for top commit:
apoelstra:
ACK 546c0122d7
tcharding:
ACK 546c0122d7
Tree-SHA512: 7167c900b77e63cf38135a3960cf9ac2615f73b2ef7020a12b5cc3f4c047910063ba9045217b9ecfa70f7de1eb0f02f2674f291bd023a853bad2b9162fae831e
When enabled this feature swaps the hash implementation of sha512,
sha256 and ripemd160 for a smaller (but also slower) one.
On embedded processors (Cortex-M4) it can lead to up to a 52% size
reduction, from around 37KiB for just the `process_block` methods of the
three hash functions to 17.8KiB.
154552e334 docs: Do not link to std::option::Option (Tobin C. Harding)
24843468c3 Remove rustdocs links to serde (Tobin C. Harding)
Pull request description:
Two minor patches to fix up docs links. These were originally done as part of #1880 but are unrelated so pushing them up separately.
ACKs for top commit:
apoelstra:
ACK 154552e334
RCasatta:
utACK 154552e334
Tree-SHA512: e45e1538c66b59d63a66898896927bb6c1336fb4c8515bb9e2204c8035870ef8e4a6fd32dfc83db2938afda67feb27c48989e382410f9e7ea7a967132941c720
We have just released the `hex-conservative` crate, we can now use it.
Do the following:
- Depend on `hex-conservative` in `bitcoin` and `hashes`
- Re-export `hex-conservative` as `hex` from both crate roots.
- Remove all the old hex code from `hashes`
- Fix all the import statements (makes up the bulk of the lines changed
in this patch)
Recently we made the hash engine fields pub crate so that `sha512_256`
could construct a hash engine with different constants. We can make the
code slightly cleaner by adding a pub crate constructor and making the
fields private again.
Idea from Kixunil:
https://github.com/rust-bitcoin/rust-bitcoin/pull/1413#pullrequestreview-1197207593
We are trying to make error types stable on the way to v1.0
The current `hashes::Error` is a "general" enum error type with a single
variant, better to use a struct and make the error usecase specific.
Improve the `hashes::Error` by doing:
- Make it a struct
- Rename to `FromSliceError`
- Move it to the crate root (remove `error` module)
Includes usage in `bitcoin`.
Whether or not every file needs an explicit license comment is out of
scope for this patch; in the `bitcoin` crate we use SPDX identifiers
because they are a single line with no loss of "benefit" over any longer
form.
Use SPDX identifiers in `hashes`. Drop the mention of re-licensing code
from Apache to CC0-1 (because the original code was written by Andrew
as well as the copied code then if the argument ever comes up it can be
easily countered).
6c61e1019e Fix pinning (schemars and MSRV) (Tobin C. Harding)
c8e38d6a5a hashes: Implement JsonSchema for sha256t::Hash<T> (Tobin C. Harding)
Pull request description:
This has grown due to now including pinning work also done in https://github.com/rust-bitcoin/rust-bitcoin/pull/1736, I decided to do this because the PRs conflict and doing it all here saves accidentally getting out of sync. And https://github.com/rust-bitcoin/rust-bitcoin/pull/1764 requires this PR.
- Patch 1 is unchanged
- Patch 2 now fixes pinning in bitcoin and hashes CI scripts and in the docs of both as well as the manifest stuff relating to `schemars` - phew.
Fix: #1687
ACKs for top commit:
Kixunil:
ACK 6c61e1019e
apoelstra:
ACK 6c61e1019e
Tree-SHA512: eae4aa9700817bab6ad444e07709e8b1a4ffb1625e08be6ba399abde38bf6f8e5ea216a0836e2e26dfaddc76c392802cd016738ea6e753a1bca2584d9d2a9796
Done as is single patch to make sure all the docs and CI are in sync and
correct.
We currently pin the `schemars` dependency using `<=0.8.3` as well as a
the `dyn-clone` transient dependency in the manifest (`hashes` and the
extended test crate). This is incorrect because it makes usage of the
crate klunky (or possibly impossible) if downstream users wish to use a
later version of `schemars`.
Observe also that we do not have to pin `schemars`, we do however have to pin
the `serde` crate if either `serde` or `schemars` features are enabled.
Do so in CI and document in the readme file within hashes.
Currently we have a pin remaining from the old MSRV (`syn` due to use
of `matches!`).
Fix pinning by:
- Remove pin in manifest for `schemars`
- Fix pinning for MSRV in CI and docs (this includes documenting pinning
requirements for `schemars` feature because it is related to the other
pin of `serde`) in both `hashes` readme and main repo readme.
The Rust API guidelines state that macros should be evocative of the
output, which is a sensible recommendation. We already had this for
`hash_newtype!` macro but didn't for sha256t version.
This changes the macro to have this syntax:
```rust
sha256t_hash_newtype! {
// Order of these structs is fixed.
/// Optional documentation details here. Summary is auto-generated.
/*pub*/ struct Tag = raw(MIDSTATE_BYTES, LEN);
/// Documentation here
#[hash_newtype(forward)] // optional, default is backward
/*pub*/ struct HashType(/* attributes allowed here */ _);
}
```
Closes#1427
Computing hashes in const fn is useful for esily creating tags for
`sha256t`. This adds `const fn` implementation for `sha256::Hash` and
the algorithm for computing midstate of tagged hash in `const` context.
Part of #1427
a189942c64 Use doc_auto_cfg (Tobin C. Harding)
Pull request description:
If we use `#![cfg_attr(docsrs, feature(doc_auto_cfg))]` instead of `#![cfg_attr(docsrs, feature(doc_cfg))]` we no longer need to manually mark types with `#[cfg_attr(docsrs, doc(cfg(feature = "std")))]`.
Sweeeeeet.
Props to pezcore for the lesson :)
ACKs for top commit:
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ACK a189942c64
Kixunil:
ACK a189942c64
Tree-SHA512: 1ced1e09f5d1733b362b83ca650d3f52c89eb57e78e8437f74c496d89776548f8c50feab6750352342e2abe680434681de2c126ce36a81dda21397b9695d4d4e
If we use `#![cfg_attr(docsrs, feature(doc_auto_cfg))]` instead of
`#![cfg_attr(docsrs, feature(doc_cfg))]` we no longer need to manually
mark types with `#[cfg_attr(docsrs, doc(cfg(feature = "std")))]`.
Sweeeeeet.
The `hashes` module contains a bunch of arrays, mostly formatted with 8
hex bytes on a line; add `rustfmt::skip` to keep the formatting of
arrays as is.
Remove the exclude for the `hashes` crate. Do not run the formatter,
that will be done as a separate patch to aid review.
8ccfb412c1 Improve documentation of `hash_newtype!` (Martin Habovstiak)
58876e2be9 Remove unused macro (Martin Habovstiak)
Pull request description:
Removed unused macro and improved documentation to address review of #1659 - see commits. I also added a note about recursion.
ACKs for top commit:
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tcharding:
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Tree-SHA512: 3b4b0c4ffc8a5166619110d9dcb51affd5cafbb2af84a55dd540a815e4702514d99c71dc1c54aca27fb91970e7e7189d1dffb4f7da7951b0f71336ef6f32d30b
The macro is non-trivial, so documenting it well is very useful. This
change improves both user-facing and developer-facing code with
appropriate warnings about the limitations of the code and Rust macro
system.
Currently we have an associated type on hash types `Inner` with
accompanying methods `into_inner`, `from_inner`, `as_inner`. Also, we
provide a way to create new wrapped hash types. The use of 'inner'
becomes ambiguous with the addition of wrapped types because the inner
could be the inner hash type or the `Inner` byte array of the inner
wrapped hash type.
In an effort to make the API more clear and uniform do the following:
- Rename `Inner` -> `Bytes`
- Rename `*_inner` -> `*_byte_array`
- Rename the inner hash to/from methods to `*_raw_hash`
Correct method prefix `into_` -> `to_` because theses methods convert
owned `Copy` types.
Add the trait Bound `Copy` to the `Bytes` type because we rely on this
trait bound for the conversion methods to be correctly named according
to convention.
Because of the dependency hole created by `secp256k1` this patch changes
the secp dependency to a git tag dependency that includes changes to the
hashes calls required so that we can get green lights on CI in this
repo.
The API guidelines say macro input should be evocative of the output.
`hash_newtype` didn't have this property.
This change makes it look exactly like the resulting struct, `$len`
parameter was removed since it's not needed, reversing is controlled
using an attribute. The macro is also better documented and ready to be
extended in the future.
The tagged SHA256 newtype is not yet modified because it has a more
complicated input parameters.
Closes#1648
a121e19e94 hashes: Implement AsRef for fixed size arrays (Tobin C. Harding)
Pull request description:
Implement `AsRef<[u8; X]>` for hash types including wrapped hash types. Doing so means at times the compiler can no longer infer the type because we have `AsRef<[u8]` implemented also but we can use `into_inner` and `as_inner` to get the inner array if needed.
Fix: #1462
## Note
This touches code that will likely be changed by #1577 and when we do #1491 but I believe its a step forward.
ACKs for top commit:
arturomf94:
ACK [`a121e19`](a121e19e94)
apoelstra:
ACK a121e19e94
Kixunil:
ACK a121e19e94
Tree-SHA512: 257c44826c7649db25bb3a6f023f68b2f17b70c546a056afad044bc8a16bf61f654c3846222505aaf5e6f9a0ad1d2113272d61317b407d0ac83702e41060a1ee
Currently we have a few things mixed up in the feature gating of
`hashes`.
Observe that:
- `io::Write` is not related to allocation.
- "std" should be able to enable "alloc".
Improve feature gating by doing:
- Enable "alloc" from "std" and simplify `cfg` codebase wide.
- Enable "internals/alloc" from "alloc".
- Fix feature gating to use the minimal requirement i.e., "alloc".
Remove `FromHex` from hash and script types
- Remove the `FromHex` implementation from hash types and `ScriptBuf`
- Remove the `FromStr` implementation from `ScriptBuf` because it does not
roundtrip with `Display`.
- Implement a method `from_hex` on `ScriptBuf`.
- Implement `FromStr` on hash types using a fixed size array.
This leaves `FromHex` implementations only on `Vec` and fixed size arrays.
It is easier to maintain code if macros use the fully qualified path to
types and functions instead of relying on code that uses the macro to
import said type or function.
We have old Rust 1.29 error handling code still in `hashes`. Implement
`std::error::Error` for the `hex::Error` and `error::Error` types in
line with "modern" Rust 1.41.1 error handling.
Implement `AsRef<[u8; X]>` for hash types including wrapped hash types.
Doing so means at times the compiler can no longer infer the type because we have
`AsRef<[u8]` implemented also but we can use `into_inner` and `as_inner`
to get the inner array if needed.
Matt Corallo
Andrew Poelstra
Tobin C. Harding
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