# extract_fence_ext.c

Extract the extension from a markdown code fence.

---

## Includes
```c
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#include "utils.h"
```

---

## Function Description

### `extract_fence_ext`
Extracts the extension from a markdown code fence string.

#### Parameter
- `fence`: Pointer to a null-terminated string representing the code fence.

#### Return Value

Returns a dynamically allocated string containing the extracted extension, or
`NULL` if no extension is found or if the input is not a valid code fence.

Return value must be freed by the caller.

#### Implementation

```c
char *
extract_fence_ext(const char *fence)
{
	const char	*start;
	const char	*end;
	size_t		len;
	char		*ext;

	if (0 != strncmp(fence, "```", 3))
		return (NULL);
	start = fence + 3;
	while (' ' == *start || '\t' == *start)
		start++;
	if ('\n' == *start || '\0' == *start)
		return (NULL);
	end = start;
	while ('\n' != *end && '\0' != *end && ' ' != *end && '\t' != *end)
		end++;
	len = (size_t)(end - start);
	ext = malloc(len + 1);
	if (NULL == ext)
		return (NULL);
	memcpy(ext, start, len);
	ext[len] = '\0';
	return (ext);
}
```