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bio_f_buffer(3) [centos man page]

BIO_f_buffer(3) 						      OpenSSL							   BIO_f_buffer(3)

NAME
BIO_f_buffer - buffering BIO SYNOPSIS
#include <openssl/bio.h> BIO_METHOD * BIO_f_buffer(void); #define BIO_get_buffer_num_lines(b) BIO_ctrl(b,BIO_C_GET_BUFF_NUM_LINES,0,NULL) #define BIO_set_read_buffer_size(b,size) BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,0) #define BIO_set_write_buffer_size(b,size) BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,1) #define BIO_set_buffer_size(b,size) BIO_ctrl(b,BIO_C_SET_BUFF_SIZE,size,NULL) #define BIO_set_buffer_read_data(b,buf,num) BIO_ctrl(b,BIO_C_SET_BUFF_READ_DATA,num,buf) DESCRIPTION
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. NOTES
Buffering BIOs implement BIO_gets() by using BIO_read() operations on the next BIO in the chain. By prepending a buffering BIO to a chain it is therefore possible to provide BIO_gets() functionality if the following BIOs do not support it (for example SSL BIOs). 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. RETURN VALUES
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. SEE ALSO
BIO(3), BIO_reset(3), BIO_flush(3), BIO_pop(3), BIO_ctrl(3), BIO_int_ctrl(3) 1.0.1e 2013-02-11 BIO_f_buffer(3)

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BIO_read(3)							      OpenSSL							       BIO_read(3)

NAME
BIO_read, BIO_write, BIO_gets, BIO_puts - BIO I/O functions SYNOPSIS
#include <openssl/bio.h> int BIO_read(BIO *b, void *buf, int len); int BIO_gets(BIO *b,char *buf, int size); int BIO_write(BIO *b, const void *buf, int len); int BIO_puts(BIO *b,const char *buf); DESCRIPTION
BIO_read() attempts to read len bytes from BIO b and places the data in buf. BIO_gets() performs the BIOs "gets" operation and places the data in buf. Usually this operation will attempt to read a line of data from the BIO of maximum length len. There are exceptions to this however, for example BIO_gets() on a digest BIO will calculate and return the digest and other BIOs may not support BIO_gets() at all. BIO_write() attempts to write len bytes from buf to BIO b. BIO_puts() attempts to write a null terminated string buf to BIO b RETURN VALUES
All these functions return either the amount of data successfully read or written (if the return value is positive) or that no data was successfully read or written if the result is 0 or -1. If the return value is -2 then the operation is not implemented in the specific BIO type. NOTES
A 0 or -1 return is not necessarily an indication of an error. In particular when the source/sink is non-blocking or of a certain type it may merely be an indication that no data is currently available and that the application should retry the operation later. One technique sometimes used with blocking sockets is to use a system call (such as select(), poll() or equivalent) to determine when data is available and then call read() to read the data. The equivalent with BIOs (that is call select() on the underlying I/O structure and then call BIO_read() to read the data) should not be used because a single call to BIO_read() can cause several reads (and writes in the case of SSL BIOs) on the underlying I/O structure and may block as a result. Instead select() (or equivalent) should be combined with non blocking I/O so successive reads will request a retry instead of blocking. See BIO_should_retry(3) for details of how to determine the cause of a retry and other I/O issues. If the BIO_gets() function is not supported by a BIO then it possible to work around this by adding a buffering BIO BIO_f_buffer(3) to the chain. SEE ALSO
BIO_should_retry(3) TBA 1.0.1e 2013-02-11 BIO_read(3)
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