diff options
author | Dr. Stephen Henson <steve@openssl.org> | 2000-09-18 23:05:33 +0000 |
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committer | Dr. Stephen Henson <steve@openssl.org> | 2000-09-18 23:05:33 +0000 |
commit | 3b2cbbcb9ae6093510b00c459e73104095a29ab9 (patch) | |
tree | 10638a10a4c83925ddbf5cbd884b10d543a2bb3c /doc/crypto/BIO_ctrl.pod | |
parent | c69c47b9fed34d518c54083abf0c9d904b59d91e (diff) |
Clarify the BIO_seek() mess and related issues.
Buffering BIO docs.
Diffstat (limited to 'doc/crypto/BIO_ctrl.pod')
-rw-r--r-- | doc/crypto/BIO_ctrl.pod | 28 |
1 files changed, 20 insertions, 8 deletions
diff --git a/doc/crypto/BIO_ctrl.pod b/doc/crypto/BIO_ctrl.pod index acc46db8ce..722e8b8f46 100644 --- a/doc/crypto/BIO_ctrl.pod +++ b/doc/crypto/BIO_ctrl.pod @@ -47,8 +47,8 @@ BIO_reset() typically resets a BIO to some initial state, in the case of file related BIOs for example it rewinds the file pointer to the start of the file. -BIO_seek() resets a file related BIO's file position pointer to B<ofs> -bytes from start of file. +BIO_seek() resets a file related BIO's (that is file descriptor and +FILE BIOs) file position pointer to B<ofs> bytes from start of file. BIO_tell() returns the current file position of a file related BIO. @@ -73,10 +73,12 @@ macros which call BIO_ctrl(). =head1 RETURN VALUES -BIO_reset() returns 1 for success and 0 for failure. +BIO_reset() normally returns 1 for success and 0 or -1 for failure. File +BIOs are an exception, they return 0 for success and -1 for failure. BIO_seek() and BIO_tell() both return the current file position on success -and -1 for failure. +and -1 for failure, except file BIOs which for BIO_seek() always return 0 +for success and -1 for failure. BIO_flush() returns 1 for success and 0 or -1 for failure. @@ -102,14 +104,24 @@ case of a file BIO some data may be available in the FILE structures internal buffers but it is not possible to determine this in a portably way. For other types of BIO they may not be supported. -Filter BIOs if the do not internally handle a particular BIO_ctrl() +Filter BIOs if they do not internally handle a particular BIO_ctrl() operation usually pass the operation to the next BIO in the chain. This often means there is no need to locate the required BIO for a particular operation, it can be called on a chain and it will -be automatically passed to the relevant BIO. +be automatically passed to the relevant BIO. However this can cause +unexpected results: for example no current filter BIOs implement +BIO_seek(), but this may still succeed if the chain ends in a FILE +or file descriptor BIO. -Source/sink BIOs will return an error if the do not recognize the -BIO_ctrl() operation. +Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl() +operation. + +=head1 BUGS + +Some of the return values are ambiguous and care should be taken. In +particular a return value of 0 can be returned if an operation is not +supported, if an error occurred, if EOF has not been reached and in +the case of BIO_seek() on a file BIO for a successful operation. =head1 SEE ALSO |