Prevent calls that modify an evbuffer from succeeding. A buffer may
frozen at the front, at the back, or at both the front and the back.
If the front of a buffer is frozen, operations that drain data from
the front of the buffer, or that prepend data to the buffer, will
fail until it is unfrozen. If the back a buffer is frozen, operations
that append data from the buffer will fail until it is unfrozen.
@param buf The buffer to freeze
@param at_front If true, we freeze the front of the buffer. If false,
we freeze the back.
@return 0 on success, -1 on failure.
Prevent calls that modify an evbuffer from succeeding. A buffer may frozen at the front, at the back, or at both the front and the back.
If the front of a buffer is frozen, operations that drain data from the front of the buffer, or that prepend data to the buffer, will fail until it is unfrozen. If the back a buffer is frozen, operations that append data from the buffer will fail until it is unfrozen.
@param buf The buffer to freeze @param at_front If true, we freeze the front of the buffer. If false, we freeze the back. @return 0 on success, -1 on failure.