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switch impls based on crate features for u8 as an example #101

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5 changes: 5 additions & 0 deletions Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,11 @@ keywords = ["crc", "crc16", "crc32", "crc64", "hash"]
categories = ["algorithms", "no-std"]
edition = "2018"

[features]
notable-defaults = []
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[nit] On naming, wdyt about "prefer-low-memory" and "prefer-fast" instead for "notable-defaults" and "slice16-defaults" respectively? They might be easier to understand for some users since it maps closer to intent.

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I'd expect the people that care about any of this to also care about the specifics i.e. how much memory is "low memory" exactly at which point they also need to read about the different implementations. To then name the features after these implementations seems logical to me

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Fair enough, I still think the feature names can be a bit clearer though. Especially with "notable" as it can be interpreted as a single word. Maybe "prefer-no-table", "prefer-bytewise", "prefer-slice-by-16"? I think it's worth avoiding "default" as it's an overloaded term.

Also, would be good to add a comment on top of each feature (similar to https://github.com/serde-rs/serde/blob/master/serde/Cargo.toml#L39)

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I'll have another think about the naming

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I came up with

  • no-table-memory-restrictions
  • bytewise-memory-restrictions
  • slice16-memory-restrictions

I think this captures the aspect of the additional restrictions one is imposing by activating the features, hopefully also conveying that those are additive.

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Ah, that's a good idea! I've also seen "limit" used in this context. Wdyt about using "mem-limit" or "memory-limit" as the suffix? Has the advantage that it's shorter. Sorry for being so picky on the naming :)

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Sorry for being so picky on the naming :)

No worries, naming is important and one of the hardest things to get right :)

"Limit" seems like a fine choice!

bytewise-defaults = []
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slice16-defaults = []

[dependencies]
crc-catalog = "2.1.0"

Expand Down
3 changes: 1 addition & 2 deletions src/crc128.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,5 @@
use crc_catalog::Algorithm;

use crate::util::crc128;
use crc_catalog::Algorithm;

mod bytewise;
mod default;
Expand Down
87 changes: 82 additions & 5 deletions src/crc128/default.rs
Original file line number Diff line number Diff line change
@@ -1,11 +1,62 @@
use crate::table::crc128_table;
use crate::{Algorithm, Crc, Digest};
use crate::crc128::{finalize, init};
use crate::{Algorithm, Crc, Digest, Implementation};

use super::{finalize, init, update_bytewise};
#[cfg(feature = "notable-defaults")]
impl Implementation for u128 {
type Width = u128;
type Table = ();
}

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
impl Implementation for u128 {
type Width = u128;
type Table = [u128; 256];
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
impl Implementation for u128 {
type Width = u128;
type Table = [[u128; 256]; 16];
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
impl Implementation for u128 {
type Width = u128;
type Table = [u128; 256];
}

impl Crc<u128> {
pub const fn new(algorithm: &'static Algorithm<u128>) -> Self {
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let table = crc128_table(algorithm.width, algorithm.poly, algorithm.refin);
#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
let table =
crate::table::crc128_table_slice_16(algorithm.width, algorithm.poly, algorithm.refin);

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
let table = crate::table::crc128_table(algorithm.width, algorithm.poly, algorithm.refin);

#[cfg(feature = "notable-defaults")]
#[allow(clippy::let_unit_value)]
let table = ();

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
let table = crate::table::crc128_table(algorithm.width, algorithm.poly, algorithm.refin);

Self { algorithm, table }
}

Expand All @@ -16,7 +67,33 @@ impl Crc<u128> {
}

const fn update(&self, crc: u128, bytes: &[u8]) -> u128 {
update_bytewise(crc, self.algorithm.refin, &self.table, bytes)
#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
{
super::update_slice16(crc, self.algorithm.refin, &self.table, bytes)
}

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
{
super::update_bytewise(crc, self.algorithm.refin, &self.table, bytes)
}

#[cfg(feature = "notable-defaults")]
{
super::update_nolookup(crc, self.algorithm, bytes)
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
{
super::update_bytewise(crc, self.algorithm.refin, &self.table, bytes)
}
}

pub const fn digest(&self) -> Digest<u128> {
Expand Down
86 changes: 81 additions & 5 deletions src/crc16/default.rs
Original file line number Diff line number Diff line change
@@ -1,12 +1,62 @@
use crate::crc16::{finalize, init};
use crate::table::crc16_table_slice_16;
use crate::{Algorithm, Crc, Digest};
use crate::{Algorithm, Crc, Digest, Implementation};

use super::update_slice16;
#[cfg(feature = "notable-defaults")]
impl Implementation for u16 {
type Width = u16;
type Table = ();
}

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
impl Implementation for u16 {
type Width = u16;
type Table = [u16; 256];
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
impl Implementation for u16 {
type Width = u16;
type Table = [[u16; 256]; 16];
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
impl Implementation for u16 {
type Width = u16;
type Table = [u16; 256];
}

impl Crc<u16> {
pub const fn new(algorithm: &'static Algorithm<u16>) -> Self {
let table = crc16_table_slice_16(algorithm.width, algorithm.poly, algorithm.refin);
#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
let table =
crate::table::crc16_table_slice_16(algorithm.width, algorithm.poly, algorithm.refin);

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
let table = crate::table::crc16_table(algorithm.width, algorithm.poly, algorithm.refin);

#[cfg(feature = "notable-defaults")]
#[allow(clippy::let_unit_value)]
let table = ();

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
let table = crate::table::crc16_table(algorithm.width, algorithm.poly, algorithm.refin);

Self { algorithm, table }
}

Expand All @@ -17,7 +67,33 @@ impl Crc<u16> {
}

const fn update(&self, crc: u16, bytes: &[u8]) -> u16 {
update_slice16(crc, self.algorithm.refin, &self.table, bytes)
#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
{
super::update_slice16(crc, self.algorithm.refin, &self.table, bytes)
}

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
{
super::update_bytewise(crc, self.algorithm.refin, &self.table, bytes)
}

#[cfg(feature = "notable-defaults")]
{
super::update_nolookup(crc, self.algorithm, bytes)
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
{
super::update_bytewise(crc, self.algorithm.refin, &self.table, bytes)
}
}

pub const fn digest(&self) -> Digest<u16> {
Expand Down
6 changes: 3 additions & 3 deletions src/crc32.rs
Original file line number Diff line number Diff line change
@@ -1,11 +1,11 @@
use crate::util::crc32;
use crc_catalog::Algorithm;

mod bytewise;
mod default;
mod nolookup;
mod slice16;

use crate::util::crc32;
use crc_catalog::Algorithm;

// init is shared between all impls
const fn init(algorithm: &Algorithm<u32>, initial: u32) -> u32 {
if algorithm.refin {
Expand Down
87 changes: 82 additions & 5 deletions src/crc32/default.rs
Original file line number Diff line number Diff line change
@@ -1,11 +1,62 @@
use crate::table::crc32_table_slice_16;
use crate::{Algorithm, Crc, Digest};
use crate::crc32::{finalize, init};
use crate::{Algorithm, Crc, Digest, Implementation};

use super::{finalize, init, update_slice16};
#[cfg(feature = "notable-defaults")]
impl Implementation for u32 {
type Width = u32;
type Table = ();
}

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
impl Implementation for u32 {
type Width = u32;
type Table = [u32; 256];
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
impl Implementation for u32 {
type Width = u32;
type Table = [[u32; 256]; 16];
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
impl Implementation for u32 {
type Width = u32;
type Table = [u32; 256];
}

impl Crc<u32> {
pub const fn new(algorithm: &'static Algorithm<u32>) -> Self {
let table = crc32_table_slice_16(algorithm.width, algorithm.poly, algorithm.refin);
#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
let table =
crate::table::crc32_table_slice_16(algorithm.width, algorithm.poly, algorithm.refin);

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
let table = crate::table::crc32_table(algorithm.width, algorithm.poly, algorithm.refin);

#[cfg(feature = "notable-defaults")]
#[allow(clippy::let_unit_value)]
let table = ();

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
let table = crate::table::crc32_table(algorithm.width, algorithm.poly, algorithm.refin);

Self { algorithm, table }
}

Expand All @@ -16,7 +67,33 @@ impl Crc<u32> {
}

const fn update(&self, crc: u32, bytes: &[u8]) -> u32 {
update_slice16(crc, self.algorithm.refin, &self.table, bytes)
#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
feature = "slice16-defaults"
))]
{
super::update_slice16(crc, self.algorithm.refin, &self.table, bytes)
}

#[cfg(all(not(feature = "notable-defaults"), feature = "bytewise-defaults"))]
{
super::update_bytewise(crc, self.algorithm.refin, &self.table, bytes)
}

#[cfg(feature = "notable-defaults")]
{
super::update_nolookup(crc, self.algorithm, bytes)
}

#[cfg(all(
not(feature = "notable-defaults"),
not(feature = "bytewise-defaults"),
not(feature = "slice16-defaults")
))]
{
super::update_bytewise(crc, self.algorithm.refin, &self.table, bytes)
}
}

pub const fn digest(&self) -> Digest<u32> {
Expand Down
3 changes: 1 addition & 2 deletions src/crc64.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,5 @@
use crc_catalog::Algorithm;

use crate::util::crc64;
use crc_catalog::Algorithm;

mod bytewise;
mod default;
Expand Down
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