MirBSD manpage: BIO_gets(3), BIO_puts(3), BIO_read(3), BIO_write(3)

BIO_READ(3)                  OpenSSL                  BIO_READ(3)


     BIO_read, BIO_write, BIO_gets, BIO_puts - BIO I/O functions


      #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);


     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 dig-
     est 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


     All these functions return either the amount of data suc-
     cessfully 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 opera-
     tion is not implemented in the specific BIO type.


     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 struc-
     ture and may block as a result. Instead select() (or
     equivalent) should be combined with non blocking I/O so suc-
     cessive reads will request a retry instead of blocking.

MirBSD #10-current         2005-02-05                           1

BIO_READ(3)                  OpenSSL                  BIO_READ(3)

     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.




MirBSD #10-current         2005-02-05                           2

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