curl/docs/DYNBUF.md

# dynbuf

This is the internal module for creating and handling "dynamic buffers". This
means buffers that can be appended to, dynamically and grow to adapt.

There will always be a terminating zero put at the end of the dynamic buffer.

The `struct dynbuf` is used to hold data for each instance of a dynamic
buffer. The members of that struct **MUST NOT** be accessed or modified
without using the dedicated dynbuf API.

## init

```c
void Curl_dyn_init(struct dynbuf *s, size_t toobig);
```

This inits a struct to use for dynbuf and it cannot fail. The `toobig` value
**must** be set to the maximum size we allow this buffer instance to grow to.
The functions below will return `CURLE_OUT_OF_MEMORY` when hitting this limit.

## free

```c
void Curl_dyn_free(struct dynbuf *s);
```

Free the associated memory and clean up. After a free, the `dynbuf` struct can
be re-used to start appending new data to.

## addn

```c
CURLcode Curl_dyn_addn(struct dynbuf *s, const void *mem, size_t len);
```

Append arbitrary data of a given length to the end of the buffer.

## add

```c
CURLcode Curl_dyn_add(struct dynbuf *s, const char *str);
```

Append a C string to the end of the buffer.

## addf

```c
CURLcode Curl_dyn_addf(struct dynbuf *s, const char *fmt, ...);
```

Append a `printf()`-style string to the end of the buffer.

## vaddf

```c
CURLcode Curl_dyn_vaddf(struct dynbuf *s, const char *fmt, va_list ap);
```

Append a `vprintf()`-style string to the end of the buffer.

## reset

```c
void Curl_dyn_reset(struct dynbuf *s);
```

Reset the buffer length, but leave the allocation.

## tail

```c
CURLcode Curl_dyn_tail(struct dynbuf *s, size_t length);
```

Keep `length` bytes of the buffer tail (the last `length` bytes of the
buffer). The rest of the buffer is dropped. The specified `length` must not be
larger than the buffer length.

## ptr

```c
char *Curl_dyn_ptr(const struct dynbuf *s);
```

Returns a `char *` to the buffer if it has a length, otherwise a NULL. Since
the buffer may be reallocated, this pointer should not be trusted or used
anymore after the next buffer manipulation call.

## uptr

```c
unsigned char *Curl_dyn_uptr(const struct dynbuf *s);
```

Returns an `unsigned char *` to the buffer if it has a length, otherwise a
NULL. Since the buffer may be reallocated, this pointer should not be trusted
or used anymore after the next buffer manipulation call.

## len

```c
size_t Curl_dyn_len(const struct dynbuf *s);
```

Returns the length of the buffer in bytes. Does not include the terminating
zero byte.