BIO_read(3) - NetBSD Manual Pages

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BIO_read(3)                  OpenSSL                  BIO_read(3)



NAME

       BIO_read, BIO_write, BIO_gets, BIO_puts - BIO I/O func-
       tions


LIBRARY

       libcrypto, -lcrypto


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 suc-
       cessfully read or written (if the return value is posi-
       tive) 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



2001-04-12                    0.9.6g                            1





BIO_read(3)                  OpenSSL                  BIO_read(3)


       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










































2001-04-12                    0.9.6g                            2