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.tr \(*W- . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\}
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. \" fudge factors for nroff and troff . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] .\} . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents . \" corrections for vroff . \" for low resolution devices (crt and lpr) \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} ========================================================================
Title "BIO_SHOULD_RETRY 3ossl"
way too many mistakes in technical documents.
\fBBIO_should_retry() is true if the call that produced this condition should then be retried at a later time.
If BIO_should_retry() is false then the cause is an error condition.
\fBBIO_should_read() is true if the cause of the condition is that the \s-1BIO\s0 has insufficient data to return. Check for readability and/or retry the last operation.
\fBBIO_should_write() is true if the cause of the condition is that the \s-1BIO\s0 has pending data to write. Check for writability and/or retry the last operation.
\fBBIO_should_io_special() is true if some \*(L"special\*(R" condition, that is a reason other than reading or writing is the cause of the condition.
\fBBIO_retry_type() returns a mask of the cause of a retry condition consisting of the values \s-1BIO_FLAGS_READ\s0, \s-1BIO_FLAGS_WRITE\s0, \fB\s-1BIO_FLAGS_IO_SPECIAL\s0 though current \s-1BIO\s0 types will only set one of these.
\fBBIO_get_retry_BIO() determines the precise reason for the special condition, it returns the \s-1BIO\s0 that caused this condition and if \fBreason is not \s-1NULL\s0 it contains the reason code. The meaning of the reason code and the action that should be taken depends on the type of \s-1BIO\s0 that resulted in this condition.
\fBBIO_get_retry_reason() returns the reason for a special condition if passed the relevant \s-1BIO,\s0 for example as returned by BIO_get_retry_BIO().
\fBBIO_set_retry_reason() sets the retry reason for a special condition for a given \s-1BIO.\s0 This would usually only be called by \s-1BIO\s0 implementations.
If BIO_should_retry() returns false then the precise \*(L"error condition\*(R" depends on the \s-1BIO\s0 type that caused it and the return code of the \s-1BIO\s0 operation. For example if a call to BIO_read_ex() on a socket \s-1BIO\s0 returns 0 and BIO_should_retry() is false then the cause will be that the connection closed. A similar condition on a file \s-1BIO\s0 will mean that it has reached \s-1EOF.\s0 Some \s-1BIO\s0 types may place additional information on the error queue. For more details see the individual \s-1BIO\s0 type manual pages.
If the underlying I/O structure is in a blocking mode almost all current \s-1BIO\s0 types will not request a retry, because the underlying I/O calls will not. If the application knows that the \s-1BIO\s0 type will never signal a retry then it need not call BIO_should_retry() after a failed \s-1BIO I/O\s0 call. This is typically done with file BIOs.
\s-1SSL\s0 BIOs are the only current exception to this rule: they can request a retry even if the underlying I/O structure is blocking, if a handshake occurs during a call to BIO_read(). An application can retry the failed call immediately or avoid this situation by setting \s-1SSL_MODE_AUTO_RETRY\s0 on the underlying \s-1SSL\s0 structure.
While an application may retry a failed non blocking call immediately this is likely to be very inefficient because the call will fail repeatedly until data can be processed or is available. An application will normally wait until the necessary condition is satisfied. How this is done depends on the underlying I/O structure.
For example if the cause is ultimately a socket and BIO_should_read() is true then a call to select() may be made to wait until data is available and then retry the \s-1BIO\s0 operation. By combining the retry conditions of several non blocking BIOs in a single select() call it is possible to service several BIOs in a single thread, though the performance may be poor if \s-1SSL\s0 BIOs are present because long delays can occur during the initial handshake process.
It is possible for a \s-1BIO\s0 to block indefinitely if the underlying I/O structure cannot process or return any data. This depends on the behaviour of the platforms I/O functions. This is often not desirable: one solution is to use non blocking I/O and use a timeout on the select() (or equivalent) call.
\fBBIO_retry_type() returns a flag combination presenting the cause of a retry condition or false if there is no retry condition.
\fBBIO_get_retry_BIO() returns a valid \s-1BIO\s0 structure.
\fBBIO_get_retry_reason() returns the reason for a special condition.
Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.