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Some small clarifications.

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This commit is contained in:
Bodo Möller 2000-09-14 22:09:55 +00:00
parent e1b78bc64d
commit e39c194387
1 changed files with 9 additions and 8 deletions
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17
doc/crypto/BIO_s_bio.pod
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@ -33,15 +33,16 @@ BIO_ctrl_reset_read_request - BIO pair BIO
BIO_s_bio() returns the method for a BIO pair. A BIO pair is a pair of source/sink BIO_s_bio() returns the method for a BIO pair. A BIO pair is a pair of source/sink
BIOs where data written to either half of the pair is buffered and can be read from BIOs where data written to either half of the pair is buffered and can be read from
the other half. the other half. Both halves must usually by handled by the same application thread
since no locking is done on the internal data structures.
Since BIO chains typically end in a source/sink BIO it is possible to make this Since BIO chains typically end in a source/sink BIO it is possible to make this
one half of a BIO pair and have all the data processed by the chain under application one half of a BIO pair and have all the data processed by the chain under application
control. control.
One typical use of BIO pairs is to place SSL I/O under application control, this One typical use of BIO pairs is to place TLS/SSL I/O under application control, this
can be used when the application wishes to use a non standard trasport for can be used when the application wishes to use a non standard transport for
SSL or the normal socket routines are inappropriate. TLS/SSL or the normal socket routines are inappropriate.
Calls to BIO_read() will read data from the buffer or request a retry if no Calls to BIO_read() will read data from the buffer or request a retry if no
data is available. data is available.
@ -57,7 +58,7 @@ BIO_reset() clears any data in the write buffer.
BIO_make_bio_pair() joins two separate BIOs into a connected pair. BIO_make_bio_pair() joins two separate BIOs into a connected pair.
BIO_destroy_pair() destroys the association between two connected BIOs. Freeing BIO_destroy_pair() destroys the association between two connected BIOs. Freeing
up both halves of the pair will automatically destroy the association. up any half of the pair will automatically destroy the association.
BIO_set_write_buf_size() sets the write buffer size of BIO B<b> to B<size>. BIO_set_write_buf_size() sets the write buffer size of BIO B<b> to B<size>.
If the size is not initialised a default value is used. This is currently If the size is not initialised a default value is used. This is currently
@ -79,7 +80,7 @@ whereas BIO_get_write_guarantee() is a macro.
BIO_get_read_request() and BIO_ctrl_get_read_request() return the amount of data BIO_get_read_request() and BIO_ctrl_get_read_request() return the amount of data
requested (or the buffer size if it is less) if the last read failed due to an requested (or the buffer size if it is less) if the last read failed due to an
empty buffer. This can be used to determine how much data should be written to the empty buffer. This can be used to determine how much data should be written to the
other half of the pair so the next read will succeed: this is most useful in SSL other half of the pair so the next read will succeed: this is most useful in TLS/SSL
applications where the amount of data read is usually meaningful rather than just applications where the amount of data read is usually meaningful rather than just
a buffer size. After a successful read this call will return zero. a buffer size. After a successful read this call will return zero.
@ -91,7 +92,7 @@ BIO_get_read_request() to zero.
Both halves of a BIO pair should be freed. That is even if one half is implicity Both halves of a BIO pair should be freed. That is even if one half is implicity
freed due to a BIO_free_all() or SSL_free() call the other half needs to be freed. freed due to a BIO_free_all() or SSL_free() call the other half needs to be freed.
When used in bidirectional applications (such as SSL) care should be taken to When used in bidirectional applications (such as TLS/SSL) care should be taken to
flush any data in the write buffer. This can be done by calling BIO_pending() flush any data in the write buffer. This can be done by calling BIO_pending()
on the other half of the pair and, if any data is pending, reading it and sending on the other half of the pair and, if any data is pending, reading it and sending
it to the underlying transport. This must be done before any normal processing it to the underlying transport. This must be done before any normal processing
@ -99,7 +100,7 @@ it to the underlying transport. This must be done before any normal processing
To see why this is important consider a case where a request is sent using To see why this is important consider a case where a request is sent using
BIO_write() and a response read with BIO_read(), this can occur during an BIO_write() and a response read with BIO_read(), this can occur during an
SSL handshake for example. BIO_write() will succeed and place data in the write TLS/SSL handshake for example. BIO_write() will succeed and place data in the write
buffer. BIO_read() will initially fail and BIO_should_read() will be true. If buffer. BIO_read() will initially fail and BIO_should_read() will be true. If
the application then waits for data to be available on the underlying transport the application then waits for data to be available on the underlying transport
before flusing the write buffer it will never succeed because the request was before flusing the write buffer it will never succeed because the request was