Obtain a writable buffer from a memory BIO without advancing the write pointer.
Call BIO_nwrite() afterward to commit written bytes, or use BIO_nwrite() directly.
Number of bytes available at *buf, or a negative value on error.
| Name | Description |
|---|---|
| bio | Memory BIO to write into. |
| buf | Receives a pointer into the BIO's internal buffer (valid until the next modify). |