函数 av_bprint_init 

pub unsafe extern "C" fn av_bprint_init(
    buf: *mut AVBPrint,
    size_init: c_uint,
    size_max: c_uint,
)

Init a print buffer.

@param buf buffer to init @param size_init initial size (including the final 0) @param size_max maximum size; - 0 means do not write anything, just count the length - 1 is replaced by the maximum value for automatic storage any large value means that the internal buffer will be reallocated as needed up to that limit - -1 is converted to UINT_MAX, the largest limit possible. Check also AV_BPRINT_SIZE_* macros.