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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



0.9.7l                                           2000-09-16                                      BIO_read(3)