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feat: simplify manual bits extraction and an unneeded reref #484
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Byron
approved these changes
Apr 27, 2025
| @@ -303,7 +303,7 @@ impl<R: BufRead> Read for GzDecoder<R> { | |||
| if *pos < buf.len() { | |||
| *pos += read_into(self.reader.get_mut().get_mut(), &mut buf[*pos..])?; | |||
| } else { | |||
| let (crc, amt) = finish(&buf); | |||
| let (crc, amt) = finish(buf); | |||
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It's strange that clippy didn't catch this one before.
There are, however, many other warnings might be something you are interested in fixing/improving as well.
clippy log
❯ cargo clippy
Updating crates.io index
Locking 13 packages to latest compatible versions
Adding bitflags v2.9.0
Updating cloudflare-zlib-sys v0.3.3 -> v0.3.6
Adding getrandom v0.3.2
Updating libc v0.2.153 -> v0.2.172
Updating libz-rs-sys v0.4.1 -> v0.5.0
Updating miniz_oxide v0.8.0 -> v0.8.8
Adding r-efi v5.2.0
Adding rand v0.9.1
Updating rand_chacha v0.3.1 -> v0.9.0
Adding rand_core v0.9.3
Adding wasi v0.14.2+wasi-0.2.4
Adding wit-bindgen-rt v0.39.0
Updating zlib-rs v0.4.1 -> v0.5.0
Downloaded crc32fast v1.4.0
Downloaded 1 crate (38.7 KB) in 0.19s
Compiling crc32fast v1.4.0
Checking adler2 v2.0.0
Checking cfg-if v1.0.0
Checking miniz_oxide v0.8.8
Checking flate2 v1.1.1 (/Users/byron/dev/github.com/rust-lang/flate2-rs)
warning: this operation has no effect
--> src/gz/bufread.rs:89:13
|
89 | (crc.amount() >> 0) as u8,
| ^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `crc.amount()`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
= note: `#[warn(clippy::identity_op)]` on by default
warning: this operation has no effect
--> src/gz/bufread.rs:120:15
|
120 | let crc = ((buf[0] as u32) << 0)
| ^^^^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `((buf[0] as u32))`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: this operation has no effect
--> src/gz/bufread.rs:124:15
|
124 | let amt = ((buf[4] as u32) << 0)
| ^^^^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `((buf[4] as u32))`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: this expression creates a reference which is immediately dereferenced by the compiler
--> src/gz/bufread.rs:306:49
|
306 | let (crc, amt) = finish(&buf);
| ^^^^ help: change this to: `buf`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow
= note: `#[warn(clippy::needless_borrow)]` on by default
warning: this operation has no effect
--> src/gz/write.rs:96:17
|
96 | (sum >> 0) as u8,
| ^^^^^^^^^^ help: consider reducing it to: `sum`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: this operation has no effect
--> src/gz/write.rs:100:17
|
100 | (amt >> 0) as u8,
| ^^^^^^^^^^ help: consider reducing it to: `amt`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: this operation has no effect
--> src/gz/write.rs:297:19
|
297 | let crc = ((self.crc_bytes[0] as u32) << 0)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `((self.crc_bytes[0] as u32))`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: this operation has no effect
--> src/gz/write.rs:301:19
|
301 | let amt = ((self.crc_bytes[4] as u32) << 0)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `((self.crc_bytes[4] as u32))`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: this operation has no effect
--> src/gz/mod.rs:138:41
|
138 | self.header.mtime = ((buffer[4] as u32) << 0)
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `((buffer[4] as u32))`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: this operation has no effect
--> src/gz/mod.rs:405:25
|
405 | header.push((v.len() >> 0) as u8);
| ^^^^^^^^^^^^^^ help: consider reducing it to: `v.len()`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: this operation has no effect
--> src/gz/mod.rs:421:21
|
421 | header[4] = (mtime >> 0) as u8;
| ^^^^^^^^^^^^ help: consider reducing it to: `mtime`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op
warning: casting to the same type is unnecessary (`isize` -> `isize`)
--> src/mem.rs:50:12
|
50 | None = ffi::MZ_NO_FLUSH as isize,
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ffi::MZ_NO_FLUSH`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
= note: `#[warn(clippy::unnecessary_cast)]` on by default
warning: casting to the same type is unnecessary (`isize` -> `isize`)
--> src/mem.rs:60:15
|
60 | Partial = ffi::MZ_PARTIAL_FLUSH as isize,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ffi::MZ_PARTIAL_FLUSH`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`isize` -> `isize`)
--> src/mem.rs:69:12
|
69 | Sync = ffi::MZ_SYNC_FLUSH as isize,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ffi::MZ_SYNC_FLUSH`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`isize` -> `isize`)
--> src/mem.rs:76:12
|
76 | Full = ffi::MZ_FULL_FLUSH as isize,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ffi::MZ_FULL_FLUSH`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`isize` -> `isize`)
--> src/mem.rs:82:14
|
82 | Finish = ffi::MZ_FINISH as isize,
| ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ffi::MZ_FINISH`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`isize` -> `isize`)
--> src/mem.rs:93:12
|
93 | None = ffi::MZ_NO_FLUSH as isize,
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ffi::MZ_NO_FLUSH`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`isize` -> `isize`)
--> src/mem.rs:102:12
|
102 | Sync = ffi::MZ_SYNC_FLUSH as isize,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ffi::MZ_SYNC_FLUSH`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`isize` -> `isize`)
--> src/mem.rs:108:14
|
108 | Finish = ffi::MZ_FINISH as isize,
| ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ffi::MZ_FINISH`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: `flate2` (lib) generated 19 warnings (run `cargo clippy --fix --lib -p flate2` to apply 19 suggestions)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 2.30s
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Yeah, I'm working my way up to solve all of them (:
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#487 is here to add Clippy to CI.
| @@ -402,8 +402,7 @@ impl GzBuilder { | |||
| let mut header = vec![0u8; 10]; | |||
| if let Some(v) = extra { | |||
| flg |= FEXTRA; | |||
| header.push((v.len() >> 0) as u8); | |||
| header.push((v.len() >> 8) as u8); | |||
| header.extend((v.len() as u16).to_le_bytes()); | |||
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I think I remember that in another PR with a similar change you could even validate that the assembly remains the same, so I'd think the same is happening here.
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finishalready takes in a reference, so this creates a needless borrow which is dereferenced at compile time.is exactly the same as doing
because we dont need the full length anyways, I find the latter simpler, LLVM should solve these as exactly the same operations with optimizations on.