feat: improve slice usage from pooled objects #160
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,34 @@ | ||
| // Licensed to Elasticsearch B.V. under one or more contributor | ||
| // license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright | ||
| // ownership. Elasticsearch B.V. licenses this file to you under | ||
| // the Apache License, Version 2.0 (the "License"); you may | ||
| // not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
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| package modeldecoderutil | ||
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| // Reslice increases the slice's capacity, if necessary, to match n. | ||
| // If specified, the newFn function is used to create the elements | ||
| // to populate the additional space appended to the slice. | ||
| func Reslice[Slice ~[]model, model any](slice Slice, n int, newFn func() model) Slice { | ||
| if diff := n - cap(slice); diff > 0 { | ||
| extra := make([]model, diff) | ||
| if newFn != nil { | ||
| for i := range extra { | ||
| extra[i] = newFn() | ||
| } | ||
| } | ||
| slice = append([]model(slice)[:cap(slice)], extra...) | ||
| } | ||
| return slice[:n] | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,50 @@ | ||
| // Licensed to Elasticsearch B.V. under one or more contributor | ||
| // license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright | ||
| // ownership. Elasticsearch B.V. licenses this file to you under | ||
| // the Apache License, Version 2.0 (the "License"); you may | ||
| // not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
|
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| package modeldecoderutil | ||
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| import ( | ||
| "testing" | ||
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| "github.com/elastic/apm-data/model/modelpb" | ||
| "github.com/stretchr/testify/assert" | ||
| ) | ||
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| func TestReslice(t *testing.T) { | ||
| originalSize := 10 | ||
| s := make([]*modelpb.APMEvent, originalSize) | ||
| for i := range s { | ||
| s[i] = &modelpb.APMEvent{} | ||
| } | ||
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| downsize := 4 | ||
| s = Reslice(s, downsize, nil) | ||
| for _, e := range s { | ||
| assert.NotNil(t, e) | ||
| } | ||
| assert.Equal(t, downsize, len(s)) | ||
| assert.Equal(t, originalSize, cap(s)) | ||
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| upsize := 20 | ||
| s = Reslice(s, upsize, func() *modelpb.APMEvent { return &modelpb.APMEvent{} }) | ||
| assert.Equal(t, upsize, len(s)) | ||
| for _, e := range s { | ||
| assert.NotNil(t, e) | ||
| } | ||
| assert.Equal(t, upsize, cap(s)) | ||
|
|
||
| } |
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This doesn't seem right, we're passing out and also returning out?
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If
outis not big enough we might append to it, so we need to return a slice because they might not matchThere was a problem hiding this comment.
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I find this API a bit confusing, I think it'd be best to do one or the other. If we want to accept the
outas an argument, then we can passout *[]*modelpb.HTTPHeaderThere was a problem hiding this comment.
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I guess this signature looks similar to
s = append(s, struct{}), so that's an argument for this pattern. But we'll have to remember to use the return value.There was a problem hiding this comment.
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But for conversion purposes like this specific one, I think @marclop 's comment makes sense. It will be clearer.
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I'm a bit conflicted. This method was inspired by the
slicespackage in the stdlib (https://pkg.go.dev/slices)There are several methods/API there that returns the result (modified slice) despite changing the argument (Compact, Grow, Replace, Clip, etc.). I assume they might in turn have copied the signature of
append.I think this is a common pattern in go ecosystem but I don't feel strongly about it.
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Thanks for chiming in. I was unaware of the widespread apdoption of this pattern in the current Go stdlib. I still think it's clearer and simpler to accept a single argument. If we leave it as is, I would prefer if we documented the behaviour since there are currently no godocs for these functions.
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Done!