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Command: BIO_s_fd | Section: 3 | Source: OpenBSD | File: BIO_s_fd.3
BIO_S_FD(3) FreeBSD Library Functions Manual BIO_S_FD(3)
NAME
BIO_s_fd, BIO_set_fd, BIO_get_fd, BIO_new_fd, BIO_fd_non_fatal_error,
BIO_fd_should_retry - file descriptor BIO
SYNOPSIS
#include <openssl/bio.h>
const BIO_METHOD *
BIO_s_fd(void);
long
BIO_set_fd(BIO *b, int fd, long close_flag);
long
BIO_get_fd(BIO *b, int *c);
BIO *
BIO_new_fd(int fd, int close_flag);
int
BIO_fd_non_fatal_error(int errnum);
int
BIO_fd_should_retry(int retval);
DESCRIPTION
BIO_s_fd() returns the file descriptor BIO method. This is a wrapper
around the platform's file descriptor routines such as read(2) and
write(2).
BIO_read(3) and BIO_write(3) read or write the underlying descriptor.
BIO_puts(3) is supported but BIO_gets(3) is not.
If the close flag is set, close(2) is called on the underlying file
descriptor when the BIO is freed.
BIO_reset(3) attempts to set the file pointer to the start of the file
using lseek(fd, 0, 0).
BIO_seek(3) sets the file pointer to position ofs from start of file
using lseek(fd, ofs, 0).
BIO_tell(3) returns the current file position by calling lseek(fd, 0, 1).
BIO_set_fd() sets the file descriptor of BIO b to fd and the close flag
to close_flag.
BIO_get_fd() places the file descriptor in c if it is not NULL and also
returns the file descriptor.
BIO_new_fd() returns a file descriptor BIO using fd and close_flag.
BIO_fd_non_fatal_error() determines whether the error status code errnum
represents a recoverable error. BIO_fd_should_retry() determines whether
a recoverable error occurred by inspecting both errno(2) and retval,
which is supposed to usually be the return value of a previously called
function like BIO_read(3) or BIO_write(3). These two functions are
mostly used internally; in application code, it is usually easier and
more robust to use BIO_should_retry(3), which works for any BIO type.
The behaviour of BIO_read(3) and BIO_write(3) depends on the behavior of
the platform's read(2) and write(2) calls on the descriptor. If the
underlying file descriptor is in a non-blocking mode, then the BIO will
behave in the manner described in the BIO_read(3) and BIO_should_retry(3)
manual pages.
File descriptor BIOs should not be used for socket I/O. Use socket BIOs
instead.
BIO_ctrl(3) cmd arguments correspond to macros as follows:
cmd constant corresponding macro
BIO_C_FILE_SEEK BIO_seek(3)
BIO_C_FILE_TELL BIO_tell(3)
BIO_C_GET_FD BIO_get_fd()
BIO_C_SET_FD BIO_set_fd()
BIO_CTRL_GET_CLOSE BIO_get_close(3)
BIO_CTRL_RESET BIO_reset(3)
BIO_CTRL_SET_CLOSE BIO_set_close(3)
RETURN VALUES
BIO_s_fd() returns the file descriptor BIO method.
When called on a file descriptor BIO object, BIO_method_type(3) returns
the constant BIO_TYPE_FD and BIO_method_name(3) returns a pointer to the
static string "file descriptor".
BIO_set_fd() always returns 1.
BIO_get_fd() returns the file descriptor or -1 if the BIO has not been
initialized.
BIO_new_fd() returns the newly allocated BIO or NULL if an error
occurred.
BIO_fd_non_fatal_error() returns 1 if errnum is EAGAIN, EALREADY,
EINPROGRESS, EINTR, or ENOTCONN and 0 otherwise, even if errnum is 0.
BIO_fd_should_retry() returns 1 if BIO_fd_non_fatal_error(errno) is 1 and
retval is either 0 or -1, or 0 otherwise.
EXAMPLES
This is a file descriptor BIO version of "Hello World":
BIO *out;
out = BIO_new_fd(fileno(stdout), BIO_NOCLOSE);
BIO_printf(out, "Hello World\n");
BIO_free(out);
SEE ALSO
BIO_new(3), BIO_read(3), BIO_s_socket(3), BIO_seek(3),
BIO_should_retry(3)
HISTORY
BIO_s_fd(), BIO_set_fd(), and BIO_get_fd() first appeared in SSLeay
0.6.0, BIO_fd_should_retry() in SSLeay 0.6.5, and BIO_new_fd() and
BIO_fd_non_fatal_error() in SSLeay 0.8.0. All these functions have been
available since OpenBSD 2.4.
FreeBSD 14.1-RELEASE-p8 November 16, 2023 FreeBSD 14.1-RELEASE-p8