mirror of https://github.com/deavmi/dlog.git
176 lines
6.1 KiB
Markdown
176 lines
6.1 KiB
Markdown
<p align="center">
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<img src="branding/logo.png" width=220>
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</p>
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<br>
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<h1 align="center">dlog</h1>
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<h3 align="center"><i><b>Simple and modular logging library</i></b></h3>
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---
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<br>
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<br
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`[2021-Dec-23 11:17:35.3527637] (source/dlog/testing/thing.d:12): This is a log message`
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---
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[](https://github.com/deavmi/dlog/actions/workflows/d.yml)
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## Usage
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We recommend you use [dub](http://code.dlang.org) to add dlog to your project as follows:
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```
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dub add dlog
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```
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* [View on DUB](https://code.dlang.org/packages/dlog)
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* [View API](https://dlog.dpldocs.info/v0.3.19/index.html)
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### Components
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dlog is formed out of two main components:
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1. `Logger`
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* The logger contains the needed barebones for facilitating the actual logging of text
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2. `MessageTransform`
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* A MessageTransform is attached to a logger and performs manipulation on the text input into the logger for logging
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* They may be chained as to perform multiple transformations in a stream-like fashion
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### Quick start
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If you want to immediately begin logging text usin the defaults and don't care about implementing your own transformations then you can
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simply use the default logger as follows:
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```d
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import dlog;
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Logger logger = new DefaultLogger();
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logger.log("This is a log message");
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logger.log(1);
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logger.log(1==1);
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logger.log([1,2,3]);
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```
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This will output the following:
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```
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[2021-Dec-23 11:17:35.3527637] (source/dlog/testing/thing.d:12): This is a log message
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[2021-Dec-23 11:17:35.3527717] (source/dlog/testing/thing.d:13): 1
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[2021-Dec-23 11:17:35.3527789] (source/dlog/testing/thing.d:14): true
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[2021-Dec-23 11:17:35.3527871] (source/dlog/testing/thing.d:15): [1, 2, 3]
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```
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As you can see file and line numbering of where the `log()` function is called appears in the log message which can be quite helpful
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for debugging.
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---
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We also support many different logging levels which can be accomplished using the `error`, `debug_` (or the `dbg` alias), `info `(the default) and `warn`:
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```d
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Logger logger = new DefaultLogger();
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// Create a default logger with the default joiner
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logger = new DefaultLogger();
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// Test out `error()`
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logger.error(["woah", "LEVELS!"], 69.420);
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// Test out `info()`
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logger.info(["woah", "LEVELS!"], 69.420);
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// Test out `warn()`
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logger.warn(["woah", "LEVELS!"], 69.420);
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// Test out `debug_()`
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logger.debug_(["woah", "LEVELS!"], 69.420);
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```
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This outputs the following:
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```
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[2023-Mar-03 11:33:49.2617904] (source/dlog/core.d:427): ["woah", "LEVELS!"] 69.42
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[2023-Mar-03 11:33:49.2618091] (source/dlog/core.d:430): ["woah", "LEVELS!"] 69.42
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[2023-Mar-03 11:33:49.2618273] (source/dlog/core.d:433): ["woah", "LEVELS!"] 69.42
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[2023-Mar-03 11:33:49.2618457] (source/dlog/core.d:436): ["woah", "LEVELS!"] 69.42
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```
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You can also look into `logc(Context, string)` which allows you to use a `Context` object when logging, more information available in the [full API](https://dlog.dpldocs.info/v0.3.19/dlog.context.html).
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### Custom loggers
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#### Implementing your own transform
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Perhaps the default transformation, `DefaultTransform`, may not be what you want. Maybe you want the module name included in the logged
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messages or perhaps don't want the date-and-timestamp included at all. All of this can be up to you if you choose to implement your own
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message transform.
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You will need to start off with a class that inherits from the `MessageTransform` class and then which overrides the `transform` method as shown below:
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```d
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import dlog;
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public class CustomTranform : MessageTransform
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{
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public override string transform(string text, Context context)
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{
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string transformed;
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/* Insert code to transform `text` and return the `transformed` text */
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return transformed;
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}
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}
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```
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Additional information, besides the text being logged itself (this is the `string text` argument), comes in the form of a `Context` object `context`. What one can get from this is a `CompilationInfo` struct which contains the following fields below if one calls `toArray()` on
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it which will return a string array shown below (we refer to this array as `lineInfo`):
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1. `lineInfo[0]`
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* This contains `__FILE_FULL_PATH__` which is the full path (absolute) to the source file where `log()` was called
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2. `lineInfo[1]`
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* This contains `__FILE__` which is the path (starting at `source/` to the source file where `log()` was called
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3. `lineInfo[2]`
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* This contains a stringified version of `__LINE__` which is the line number of the call to `log()`
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4. `lineInfo[3]`
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* This contains `__MODULE__` which is the name of the module the call to `log()` appeared in
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5. `lineInfo[4]`
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* This contains `__FUNCTION__` which is the name of the function `log()` was called in
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6. `lineInfo[5]`
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* This contains `__PRETTY_FUNCTION__` which is the same as above but with type information
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The point of a `Context` object is also such that a custom transformer may expect a kind-of `Context` like a custom one (i.e. `CustomContext`)
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which perhaps a custom logger (kind-of `Logger`) can then have set certain fields in it.
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## Creating a Logger
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We now need to create a logger that makes use of our message transform, we can do so by creating an instance
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of the `Logger` class and passing in our `MessageTransform` as so:
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```d
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Logger customLogger = new DefaultLogger(new CustomTranform());
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```
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The above is all one needs to be able to pull off a custom transformation.
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### Custom Logger
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Custom loggers can also be created by sub-classing the `Logger` class and overriding the `logImpl(string)` method.
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The reason someone may want to do this is up to them. One easy to think of reason is to perhaps applying filtering
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of messages to be logged and skip them (as this method is where the I/O of printing out the logs normally happens).
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Another reason may be to log to a different data resource, the `DefaultLogger` writes to the file descriptor `0` (stdout),
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but you may want to log over a socket connection to a remote machine for example, or perhaps do several pieces of
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I/O for your logging. One can do that with a custom logger, you shoudl see `source/dlog/defaults.d` for the implementation
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of a custom logger, such as `DefaultLogger`.
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## License
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LGPL v3
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