https://github.com/orijtech/structslop
structslop is a static analyzer for Go that recommends struct field rearrangements to provide for maximum space/allocation efficiency.
https://github.com/orijtech/structslop
golang
Last synced: 2 months ago
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structslop is a static analyzer for Go that recommends struct field rearrangements to provide for maximum space/allocation efficiency.
- Host: GitHub
- URL: https://github.com/orijtech/structslop
- Owner: orijtech
- License: apache-2.0
- Created: 2020-09-18T07:10:49.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2024-02-08T11:39:21.000Z (over 1 year ago)
- Last Synced: 2024-07-31T18:18:36.726Z (10 months ago)
- Topics: golang
- Language: Go
- Homepage:
- Size: 45.9 KB
- Stars: 808
- Watchers: 8
- Forks: 29
- Open Issues: 10
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# structslop
Package structslop defines an [Analyzer](analyzer_link) that checks if struct fields can be re-arranged to optimize size.
## Installation
With Go modules:
```sh
go get github.com/orijtech/structslop/cmd/structslop
```
Without Go modules:
```sh
$ cd $GOPATH/src/github.com/orijtech/structslop
$ git checkout v0.0.6
$ go get
$ install ./cmd/structslop
```
## Usage
You can run `structslop` either on a Go package or Go files, the same way as
other Go tools work.
Example:
```sh
$ structslop github.com/orijtech/structslop/testdata/src/struct
```
or:
```sh
$ structslop ./testdata/src/struct/p.go
```
Sample output:
```text
/go/src/github.com/orijtech/structslop/testdata/struct/p.go:30:9: struct has size 24 (size class 32), could be 16 (size class 16), you'll save 50.00% if you rearrange it to:
struct {
y uint64
x uint32
z uint32
}
/go/src/github.com/orijtech/structslop/testdata/struct/p.go:36:9: struct has size 40 (size class 48), could be 24 (size class 32), you'll save 33.33% if you rearrange it to:
struct {
_ [0]func()
i1 int
i2 int
a3 [3]bool
b bool
}
/go/src/github.com/orijtech/structslop/testdata/struct/p.go:59:9: struct has size 40 (size class 48), could be 32 (size class 32), you'll save 33.33% if you rearrange it to:
struct {
y uint64
t *httptest.Server
w uint64
x uint32
z uint32
}
/go/src/github.com/orijtech/structslop/testdata/struct/p.go:67:9: struct has size 40 (size class 48), could be 32 (size class 32), you'll save 33.33% if you rearrange it to:
struct {
y uint64
t *s
w uint64
x uint32
z uint32
}
```
Example, for the first report above, the output meaning:
- The current struct size is `24`, the size that the Go runtime will allocate for that struct is `32`.
- The optimal struct size is `16`, the size that the Go runtime will allocate for that struct is `16`.
- The layout of optimal struct.
- The percentage savings with new struct layout.
That said, some structs may have a smaller size, but for efficiency, the Go runtime will allocate them in the same size class,
then those structs are not considered sloppy:
```go
type s1 struct {
x uint32
y uint64
z *s
t uint32
}
```
and:
```go
type s2 struct {
y uint64
z *s
x uint32
t uint32
}
```
have the same size class `32`, though `s2` layout is only `24` byte in size.
However, you can still get this information when you want, using `-verbose` flag:
```sh
$ structslop -verbose ./testdata/src/verbose/p.go
/go/src/github.com/orijtech/structslop/testdata/src/verbose/p.go:17:8: struct has size 0 (size class 0)
/go/src/github.com/orijtech/structslop/testdata/src/verbose/p.go:19:9: struct has size 1 (size class 8)
/go/src/github.com/orijtech/structslop/testdata/src/verbose/p.go:23:9: struct has size 32 (size class 32), could be 24 (size class 32), optimal fields order:
struct {
y uint64
z *s
x uint32
t uint32
}
```
**Note**
For applying suggested fix, use `-apply` flag, instead of `-fix`.
## Development
Go 1.20+
### Running test
Add test case to `testdata/src/struct` directory, then run:
```shell script
go test
```
## Contributing
TODO
[analyzer_link]: https://pkg.go.dev/golang.org/x/tools/go/analysis#Analyzer