# GapBuffer
This repository implements a self-contained gap buffer data structure that's easily embeddable in your own C project!

(support for unicode (utf8))

# Table of contents
1. License
1. Context
1. Usage
  1. Install
  1. Instanciate
  1. Text insertion
  1. Cursor position
  1. Text deletion
  1. Querying
1. Testing

## License
This code is MIT licensed

> Copyright 2023 Francesco Cozzuto
> 
> Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
> 
> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
> 
> THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

## Context
A gap buffer is a data structure that stores strings of text in a way that's optimized for operations you do in a text editor.

## Usage
An overview of how to use this code follows. You can find more information in the documentation that comes with the code.

### Install
To use it, first you need to drop `gap_buffer.c` and `gap_buffer.h` in your project directory and link them during compilation
like they were your files.

### Instanciate
You can instanciate a gap buffer in one of two ways:

```c
GapBuffer *GapBuffer_create(size_t capacity);
GapBuffer *GapBuffer_createUsingMemory(void *mem, size_t len);
```

The basic option is using `GapBuffer *GapBuffer_create(size_t capacity)`, which instanciates a buffer with a given initial capacity allocating space through the libc allocator. If you fill the buffer up and insert more text, the buffer will grow by moving to a bigger memory region (also allocated through `malloc`). Conversely, `GapBuffer *GapBuffer_createUsingMemory(void *mem, size_t len)` doesn't use dynamic memory and does its job using only memory provided by the caller. Either way, if it wasn't possible to instanciate the gap buffer (either because the dynamic allocation failed or the provided memory isn't big enough), NULL is returned.
Once you're done with the buffer, you'll need to deallocate it using

```c
void GapBuffer_destroy(GapBuffer *buff);
```

### Text insertion
To insert text, you must use the function
```c
bool GapBuffer_insertString(GapBuffer **buff, const char *str, size_t len);
```
which expects a UTF-8 string `str` as input and inserts it into the buffer at the cursor's position (the `len` argument refers to the number of bytes of the string, not the number of characters). After insertion, the cursor is moved after the inserted text, just like a cursor of a text editor! 

The validity of the string is checked before insertion to make sure the buffer only contains valid UTF-8. If the string is inserted then `true` is returned, else if the string is invalid UTF-8 or relocation fails, false is returned.

An important thing to note is that the caller's handle of the buffer is passed by reference because the function may need to change the pointer if relocation occurres. 

### Cursor position
To move the cursor position you can use the functions
```c
void GapBuffer_moveRelative(GapBuffer *buff, int off);
void GapBuffer_moveAbsolute(GapBuffer *buff, size_t num);
```
which move the cursor position relative to the start of the buffer or the current position of the cursor. Both the `off` and `num` quantities refer tu number of unicode characters, not raw bytes.

### Text deletion
To delete text, you need to do so relative to the cursor's position. You can either remove text before or after the cursor using these functions
```c
void GapBuffer_removeForwards(GapBuffer *buff, size_t num);
void GapBuffer_removeBackwards(GapBuffer *buff, size_t num);
```
Where `num` is the number of unicode characters to be removed. If less than `num` characters are available, then they are all removed.

### Querying
To get the byte count using the getter function
```c
size_t GapBuffer_getByteCount(GapBuffer *buff);
```
This is currently only used for testing.