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cmd, lib, util: Add a new ansi logf library
This does some ansi magic that enables us to remove previous log messages that we didn't want to see. The magic is that it works when multiple writers are logging all in parallel.
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,103 @@ | ||
| // Copyright Amazon.com Inc or its affiliates and the project contributors | ||
| // Written by James Shubin <[email protected]> and the project contributors | ||
| // | ||
| // Licensed 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. | ||
| // | ||
| // We will never require a CLA to submit a patch. All contributions follow the | ||
| // `inbound == outbound` rule. | ||
| // | ||
| // This is not an official Amazon product. Amazon does not offer support for | ||
| // this project. | ||
| // | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
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| package ansi | ||
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| import ( | ||
| "fmt" | ||
| "os" | ||
| "strings" | ||
| "sync" | ||
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| "golang.org/x/term" | ||
| ) | ||
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| // Logf is a complex printing thing to do some ansi terminal escape sequence | ||
| // magic. | ||
| // FIXME: there might be bugs if Ellipsis is very big and Width is very small. | ||
| type Logf struct { | ||
| // Prefix is a prefix to append to each message. You can leave this | ||
| // empty. | ||
| Prefix string | ||
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| // Ellipsis is what is appended to the end of each message when | ||
| // truncating. You can leave this empty. | ||
| Ellipsis string | ||
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| // Enable specifies whether you want to turn this on or not. | ||
| Enable bool | ||
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| // Prefixes are a list of string prefixes to match when deciding to | ||
| // delete a previous entry. | ||
| Prefixes []string | ||
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| mutex *sync.Mutex | ||
| previous string | ||
| isTerminal bool | ||
| width int | ||
| } | ||
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| // Init must be called once before Logf is used. As a convenience, this returns | ||
| // the Logf function that you should use! | ||
| func (obj *Logf) Init() func(format string, v ...interface{}) { | ||
| obj.mutex = &sync.Mutex{} | ||
| //obj.previous = "" | ||
| obj.isTerminal = term.IsTerminal(0) | ||
| var err error | ||
| obj.width, _, err = term.GetSize(0) | ||
| if err != nil { | ||
| obj.isTerminal = false // keep it simple, who cares | ||
| } | ||
|
|
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| return obj.Logf | ||
| } | ||
|
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| // Logf is the actual Logf function you should use. You must run Init before | ||
| // you use this. | ||
| func (obj *Logf) Logf(format string, v ...interface{}) { | ||
| s := fmt.Sprintf(format, v...) | ||
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| if obj.isTerminal { | ||
| // TODO: what about multi-char width UTF-8 stuff? | ||
| if len(s) > obj.width-len(obj.Prefix) { // truncate/ellipsize | ||
| s = s[0:obj.width-len(obj.Prefix)-len(obj.Ellipsis)] + obj.Ellipsis | ||
| } | ||
| } | ||
| s = s + "\n" // add the newline in | ||
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| obj.mutex.Lock() // for safety | ||
| validPrefix := false | ||
| for _, p := range obj.Prefixes { | ||
| b := strings.HasPrefix(obj.previous, p) | ||
| validPrefix = validPrefix || b | ||
| } | ||
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| if obj.Enable && obj.previous != "" && validPrefix { | ||
| // move up 1 line, clear to left | ||
| fmt.Fprint(os.Stderr, "\033[1A\033[K") // not 1K as you'd think | ||
| } | ||
| fmt.Fprint(os.Stderr, obj.Prefix+s) // actually print | ||
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| obj.previous = s // save for later | ||
| obj.mutex.Unlock() | ||
| } |