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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
  The BIO_read() function attempts to read len bytes from BIO b and places
  the data in buf.

  The BIO_gets() function 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. However, there are exceptions to this.
  For example, BIO_gets() on a digest BIO will calculate and return the
  digest, and other BIOs might not support BIO_gets().

  The BIO_write() function attempts to write len bytes from buf to BIO b.

  The BIO_puts() function attempts to write a null terminated string buf to
  BIO b

NOTES
  A 0 or -1 return might indicate an error. However, when the source/sink is
  non-blocking or of a certain type, it might be an indication that no data
  is 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 nonblocking 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 is possible to
  work around this by adding a buffering BIO, BIO_f_buffer(), to the chain.

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.

SEE ALSO
  Functions: BIO_should_retry(3)

Index for Section 3

Alphabetical listing for B

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