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BIO_get_buffer_num_lines, BIO_set_read_buffer_size, BIO_set_write_buffer_size, BIO_set_buffer_size, BIO_set_buffer_read_data, BIO_f_buffer - buffering BIO
#include <openssl/bio.h> const BIO_METHOD *BIO_f_buffer(void); long BIO_get_buffer_num_lines(BIO *b); long BIO_set_read_buffer_size(BIO *b, long size); long BIO_set_write_buffer_size(BIO *b, long size); long BIO_set_buffer_size(BIO *b, long size); long BIO_set_buffer_read_data(BIO *b, void *buf, long num);
BIO_f_buffer() returns the buffering BIO method. Data written to a buffering BIO is buffered and periodically written to the next BIO in the chain. Data read from a buffering BIO comes from an internal buffer which is filled from the next BIO in the chain. Both BIO_gets() and BIO_puts() are supported. Calling BIO_reset() on a buffering BIO clears any buffered data. BIO_get_buffer_num_lines() returns the number of lines currently buffered. BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and BIO_set_buffer_size() set the read, write or both read and write buffer sizes to size. The initial buffer size is DEFAULT_BUFFER_SIZE, currently 4096. Any attempt to reduce the buffer size below DEFAULT_BUFFER_SIZE is ignored. Any buffered data is cleared when the buffer is resized. BIO_set_buffer_read_data() clears the read buffer and fills it with num bytes of buf. If num is larger than the current buffer size the buffer is expanded.
These functions, other than BIO_f_buffer(), are implemented as macros. Buffering BIOs implement BIO_read_ex() and BIO_gets() by using BIO_read_ex() operations on the next BIO in the chain and storing the result in an internal buffer, from which bytes are given back to the caller as appropriate for the call; a BIO_gets() is guaranteed to give the caller a whole line, and BIO_read_ex() is guaranteed to give the caller the number of bytes it asks for, unless there's an error or end of communication is reached in the next BIO. By prepending a buffering BIO to a chain it is therefore possible to provide BIO_gets() or exact size BIO_read_ex() functionality if the following BIOs do not support it. Do not add more than one BIO_f_buffer() to a BIO chain. The result of doing so will force a full read of the size of the internal buffer of the top BIO_f_buffer(), which is 4 KiB at a minimum. Data is only written to the next BIO in the chain when the write buffer fills or when BIO_flush() is called. It is therefore important to call BIO_flush() whenever any pending data should be written such as when removing a buffering BIO using BIO_pop(). BIO_flush() may need to be retried if the ultimate source/sink BIO is non blocking.
BIO_f_buffer() returns the buffering BIO method. BIO_get_buffer_num_lines() returns the number of lines buffered (may be 0). BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and BIO_set_buffer_size() return 1 if the buffer was successfully resized or 0 for failure. BIO_set_buffer_read_data() returns 1 if the data was set correctly or 0 if there was an error.
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