Multiple verifier reference identities.

[openssl.git] / doc / crypto / BIO_ctrl.pod

diff --git a/doc/crypto/BIO_ctrl.pod b/doc/crypto/BIO_ctrl.pod
index c00fda9b08bbf6c1f464abc974b7dda37aef91a9..722e8b8f46c9c5b202bb4283338e7411d582f2d7 100644 (file)
--- a/doc/crypto/BIO_ctrl.pod
+++ b/doc/crypto/BIO_ctrl.pod
@@ -2,7 +2,10 @@
 
 =head1 NAME
 
-BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl - BIO control operations
+BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
+BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
+BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
+BIO_get_info_callback, BIO_set_info_callback - BIO control operations
 
 =head1 SYNOPSIS
 
@@ -14,6 +17,8 @@ BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl - BIO control operations
  long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg);
 
  int BIO_reset(BIO *b);
+ int BIO_seek(BIO *b, int ofs);
+ int BIO_tell(BIO *b);
  int BIO_flush(BIO *b);
  int BIO_eof(BIO *b);
  int BIO_set_close(BIO *b,long flag);
@@ -38,8 +43,14 @@ specific to a particular type of BIO are described in the specific
 BIOs manual page as well as any special features of the standard
 calls.
 
-BIO_reset() typically reset a BIO to some initial state, in the case
-of file related BIOs for example it rewinds the file pointer.
+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 (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.
 
 BIO_flush() normally writes out any internally buffered data, in some
 cases it is used to signal EOF and that no more data will be written.
@@ -55,14 +66,19 @@ be closed when the BIO is freed.
 BIO_get_close() returns the BIOs close flag.
 
 BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending()
-return the number of pending characterers in the BIOs read and write buffers.
+return the number of pending characters in the BIOs read and write buffers.
 Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending()
 return a size_t type and are functions, BIO_pending() and BIO_wpending() are
 macros which call BIO_ctrl().
 
 =head1 RETURN VALUES
 
-BIO_reset() returns 1 fo 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, 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.
 
@@ -88,6 +104,25 @@ 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 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. 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 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
 
 TBA