More preliminary BIO docs...

Incomplete and possibly inaccurate. Hope somone is
checking these :-)

doc/crypto/BIO_s_file.pod

+=pod
+
+=head1 NAME
+
+	BIO_s_file - FILE bio.
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ BIO_METHOD *	BIO_s_file(void);
+ BIO *BIO_new_file(const char *filename, const char *mode);
+ BIO *BIO_new_fp(FILE *stream, int flags);
+
+ BIO_set_fp(BIO *b,FILE *fp, int flags);
+ BIO_get_fp(BIO *b,FILE **fpp);
+
+ BIO_seek(BIO *b,int offset);
+ int BIO_tell(BIO *b);
+
+ int BIO_read_filename(BIO *b, char *name)
+ int BIO_write_filename(BIO *b, char *name)
+ int BIO_append_filename(BIO *b, char *name)
+ int BIO_rw_filename(BIO *b, char *name)
+
+=head1 DESCRIPTION
+
+BIO_s_file() returns the BIO file method. As its name implies it
+is a wrapper round the stdio FILE structure and it is a
+source/sink BIO.
+
+Calls to BIO_read() and BIO_write() read and write data to the
+underlying stream. BIO_gets() and BIO_puts() are supported on file BIOs.
+
+BIO_flush() on a file BIO calls the fflush() function on the wrapped
+stream.
+
+BIO_reset() on a file BIO calls fseek() to reset the position indicator
+to the start of the file.
+
+BIO_eof() calls feof().
+
+Setting the BIO_CLOSE flag calls fclose() on the stream when the BIO
+is freed.
+
+BIO_new_file() creates a new file BIO with mode B<mode> the meaning
+of B<mode> is the same as the stdio function fopen(). The BIO_CLOSE
+flag is set on the returned BIO.
+
+BIO_new_fp() creates a file BIO wrapping B<stream>. Flags can be:
+BIO_CLOSE, BIO_NOCLOSE (the close flag) BIO_FP_TEXT (sets the underlying
+stream to text mode, default is binary: this only has any effect under
+Win32).
+
+BIO_set_fp() set the fp of a file BIO to B<fp>. B<flags> has the same
+meaning as in BIO_new_fp(), it is a macro.
+
+BIO_get_fp() retrieves the fp of a file BIO, it is a macro.
+
+BIO_seek() is a macro that sets the position pointer to B<offset> bytes
+from the start of file.
+
+BIO_tell() returns the value of the position pointer.
+
+BIO_read_filename(), BIO_write_filename(), BIO_append_filename() and
+BIO_rw_filename() set the file BIO B<b> to use file B<name> for
+reading, writing, append or read write respectively.
+
+=head1 NOTES
+
+When wrapping stdout, stdin or stderr the underlying stream should not
+normally be closed so the BIO_NOCLOSE flag should be set.
+
+Because the file BIO calls the underlying stdio functions any quirks
+in stdio behaviour will be mirrored by the corresponding BIO.
+
+=head1 EXAMPLES
+
+File BIO "hello world":
+
+ BIO *bio_out;
+ bio_out = BIO_new_fp(stdout, BIO_NOCLOSE);
+ BIO_printf(bio_out, "Hello World\n");
+
+Alternative technique:
+
+ BIO *bio_out;
+ bio_out = BIO_new(BIO_s_file());
+ if(bio_out == NULL) /* Error ... */
+ if(!BIO_set_fp(bio_out, stdout, BIO_NOCLOSE)) /* Error ... */
+ BIO_printf(bio_out, "Hello World\n");
+
+Write to a file:
+
+ BIO *out;
+ out = BIO_new_file("filename.txt", "w");
+ if(!out) /* Error occurred */
+ BIO_printf(out, "Hello World\n");
+ BIO_free(out);
+
+Alternative technique:
+
+ BIO *out;
+ out = BIO_new(BIO_s_file());
+ if(out == NULL) /* Error ... */
+ if(!BIO_read_filename(out, "filename.txt")) /* Error ... */
+ BIO_printf(out, "Hello World\n");
+ BIO_free(out);
+
+=head1 RETURN VALUES
+
+BIO_s_file() returns the file BIO method.
+
+BIO_new_file() and BIO_new_fp() return a file BIO or NULL if an error
+occurred.
+
+BIO_set_fp() and BIO_get_fp() return 1 for success or 0 for failure
+(although the current implementation never return 0).
+
+BIO_seek() returns the same value as the underlying fseek() function:
+0 for success or -1 for failure.
+
+BIO_tell() returns the current file position.
+
+BIO_read_filename(), BIO_write_filename(),  BIO_append_filename() and
+BIO_rw_filename() return 1 for success or 0 for failure.
+
+=head1 SEE ALSO
+
+TBA

doc/crypto/BIO_s_mem.pod

+=pod
+
+=head1 NAME
+
+	BIO_s_mem - memory BIO
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ BIO_METHOD *	BIO_s_mem(void);
+
+ BIO_set_mem_eof_return(BIO *b,int v)
+ long BIO_get_mem_data(BIO *b, char **pp)
+ BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c)
+ BIO_get_mem_ptr(BIO *b,BUF_MEM **pp)
+
+ BIO *BIO_new_mem_buf(void *buf, int len);
+
+=head1 DESCRIPTION
+
+BIO_s_mem() return the memory BIO method function. 
+
+A memory BIO is a source/sink BIO which uses memory for its I/O. Data
+written to a memory BIO is stored in a BUF_MEM structure which is extended
+as appropriate to accommodate the stored data.
+
+Any data written to a memory BIO can be recalled by reading from it.
+Unless the memory BIO is read only any data read from it is deleted from
+the BIO.
+
+Memory BIOs support BIO_gets() and BIO_puts().
+
+If the BIO_CLOSE flag is set when a memory BIO is freed then the underlying
+BUF_MEM structure is also freed.
+
+Calling BIO_reset() on a read write memory BIO clears any data in it. On a
+read only BIO it restores the BIO to its original state and the read only
+data can be read again.
+
+BIO_eof() is true if no data is in the BIO.
+
+BIO_ctrl_pending() returns the number of bytes currently stored.
+
+BIO_set_mem_eof_return() sets the behaviour of memory BIO B<b> when it is
+empty. If the B<v> is zero then an empty memory BIO will return EOF (that is
+it will return zero and BIO_should_retry(b) will be false. If B<v> is non
+zero then it will return B<v> when it is empty and it will set the read retry
+flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal
+positive return value B<v> should be set to a negative value, typically -1.
+
+BIO_get_mem_data() sets B<pp> to a pointer to the start of the memory BIOs data
+and returns the total amount of data available. It is implemented as a macro.
+
+BIO_set_mem_buf() sets the internal BUF_MEM structure to B<bm> and sets the
+close flag to B<c>, that is B<c> should be either BIO_CLOSE or BIO_NOCLOSE.
+It is a macro.
+
+BIO_get_mem_ptr() places the underlying BUF_MEM structure in B<pp>. It is
+a macro.
+
+BIO_new_mem_buf() creates a memory BIO using B<len> bytes of data at B<buf>,
+if B<len> is -1 then the B<buf> is assumed to be null terminated and its
+length is determined by B<strlen>. The BIO is set to a read only state and
+as a result cannot be written to. This is useful when some data needs to be
+made available from a static area of memory in the form of a BIO. The
+supplied data is read directly from the supplied buffer: it is B<not> copied
+first, so the supplied area of memory must be unchanged until the BIO is freed.
+
+=head1 NOTES
+
+Writes to memory BIOs will always succeed if memory is available: that is
+their size can grow indefinitely.
+
+Every read from a read write memory BIO will remove the data just read with
+an internal copy operation, if a BIO contains a lots of data and it is
+read in small chunks the operation can be very slow. The use of a read only
+memory BIO avoids this problem. If the BIO must be read write then adding
+a buffering BIO to the chain will speed up the process.
+
+=head1 BUGS
+
+There should be an option to set the maximum size of a memory BIO.
+
+There should be a way to "rewind" a read write BIO without destroying
+its contents.
+
+The copying operation should not occur after every small read of a large BIO
+to improve efficieny.
+
+There shoy
+
+=head1 EXAMPLE
+
+Create a memory BIO and write some data to it:
+
+ BIO *mem = BIO_new(BIO_s_mem());
+ BIO_puts(mem, "Hello World\n"); 
+
+Create a read only memory BIO:
+
+ char data[] = "Hello World";
+ BIO *mem;
+ mem = BIO_new_mem_buf(data, -1);
+
+Extract the BUF_MEM structure from a memory BIO and then free up the BIO:
+
+ BUF_MEM *bptr;
+ BIO_get_mem_ptr(mem, &bptr);
+ BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
+ BIO_free(mem);
+ 
+
+=head1 SEE ALSO
+
+TBA

doc/crypto/BIO_should_retry.pod

+=pod
+
+=head1 NAME
+
+	BIO_should_retry, BIO_should_read, BIO_should_write - BIO retry functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ #define BIO_should_read(a)		((a)->flags & BIO_FLAGS_READ)
+ #define BIO_should_write(a)		((a)->flags & BIO_FLAGS_WRITE)
+ #define BIO_should_io_special(a)	((a)->flags & BIO_FLAGS_IO_SPECIAL)
+ #define BIO_retry_type(a)		((a)->flags & BIO_FLAGS_RWS)
+ #define BIO_should_retry(a)		((a)->flags & BIO_FLAGS_SHOULD_RETRY)
+
+ #define BIO_FLAGS_READ		0x01
+ #define BIO_FLAGS_WRITE	0x02
+ #define BIO_FLAGS_IO_SPECIAL	0x04
+ #define BIO_FLAGS_RWS (BIO_FLAGS_READ|BIO_FLAGS_WRITE|BIO_FLAGS_IO_SPECIAL)
+ #define BIO_FLAGS_SHOULD_RETRY	0x08
+
+ BIO *	BIO_get_retry_BIO(BIO *bio, int *reason);
+ int	BIO_get_retry_reason(BIO *bio);
+
+=head1 DESCRIPTION
+
+These functions determine why a BIO is not able to read or write data.
+They will typically be called after a failed BIO_read() or BIO_write()
+call.
+
+BIO_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.
+
+BIO_should_read() is true if the cause of the condition is that a BIO
+needs to read data.
+
+BIO_should_write() is true if the cause of the condition is that a BIO
+needs to read data.
+
+BIO_should_io_special() is true if some "special" condition, that is a
+reason other than reading or writing is the cause of the condition.
+
+BIO_get_retry_reason() returns a mask of the cause of a retry condition
+consisting of the values B<BIO_FLAGS_READ>, B<BIO_FLAGS_WRITE>,
+B<BIO_FLAGS_IO_SPECIAL> though current BIO types will only set one of
+these (Q: is this correct?).
+
+BIO_get_retry_BIO() determines the precise reason for the special
+condition, it returns the BIO that caused this condition and if 
+B<reason> is not NULL it contains the reason code. The meaning of
+the reason code and the action that should be taken depends on
+the type of BIO that resulted in this condition.
+
+BIO_get_retry_reason() returns the reason for a special condition if
+pass the relevant BIO, for example as returned by BIO_get_retry_BIO().
+
+=head1 NOTES
+
+If BIO_should_retry() returns false then the precise "error condition"
+depends on the BIO type that caused it and the return code of the BIO
+operation. For example if a call to BIO_read() on a socket BIO returns
+0 and BIO_should_retry() is false then the cause will be that the
+connection closed. A similar condition on a file BIO will mean that it
+has reached EOF. Some BIO types may place additional information on
+the error queue. For more details see the individual BIO type manual
+pages.
+
+If the underlying I/O structure is in a blocking mode then most BIO
+types will not signal a retry condition, because the underlying I/O
+calls will not. If the application knows that the BIO type will never
+signal a retry then it need not call BIO_should_retry() after a failed
+BIO I/O call. This is typically done with file BIOs.
+
+The presence of an SSL BIO is an exception to this rule: it can
+request a retry because the handshake process is underway (either
+initially or due to a session renegotiation) even if the underlying
+I/O structure (for example a socket) is in a blocking mode.
+
+The action an application should take after a BIO has signalled that a
+retry is required depends on the BIO that caused the retry.
+
+If the underlying I/O structure is in a blocking mode then the BIO
+call can be retried immediately. That is something like this can be
+done:
+
+ do {
+    len = BIO_read(bio, buf, len);
+ } while((len <= 0) && BIO_should_retry(bio));
+
+While an application may retry a failed non blocking call immediately
+this is likely to be very inefficient because the call is likely to
+fail repeatedly until data can be processed. 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 BIO 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. 
+
+The cause of the retry condition may not be the same as the call that
+made it: for example if BIO_write() fails BIO_should_read() can be
+true. One possible reason for this is that an SSL handshake is taking
+place.
+
+Even if data is read from the underlying I/O structure this does not
+imply that the next BIO I/O call will succeed. For example if an
+encryption BIO reads only a fraction of a block it will not be
+able to pass any data to the application until a complete block has
+been read.
+
+It is possible for a BIO to block indefinitely if the underlying I/O
+structure cannot process the 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.
+
+=head1 BUGS
+
+The OpenSSL ASN1 functions cannot gracefully deal with non blocking I/O:
+that is they cannot retry after a partial read or write. This is usually
+worked around by only passing the relevant data to ASN1 functions when
+the entire structure can be read or written.
+
+=head1 SEE ALSO
+
+TBA