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+# dynbuf
+
+This is the internal module for creating and handling "dynamic buffers". This
+means buffers that can be appended to, dynamically and grow in size 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 can't 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.