Really add BIO_read this time...

doc/crypto/BIO_read.pod

@@ -0,0 +1,52 @@
+=pod
+
+=head1 NAME
+
+	BIO_read, BIO_write, BIO_gets, BIO_puts - BIO I/O functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+int	BIO_read(BIO *b, void *buf, int len);
+int	BIO_gets(BIO *b,char *buf, int size);
+int	BIO_write(BIO *b, const void *buf, int len);
+int	BIO_puts(BIO *b,const char *buf);
+
+=head1 DESCRIPTION
+
+BIO_read() attempts to read B<len> bytes from BIO B<b> and places
+the data in B<buf>.
+
+BIO_gets() performs the BIOs "gets" operation and places the data
+in B<buf>. Usually this operation will attempt to read a line of data
+from the BIO of maximum length B<len>. There are exceptions to this
+however, for example BIO_gets() on a digest BIO will calculate and
+return the digest and other BIOs may not support BIO_gets() at all.
+
+BIO_write() attempts to write B<len> bytes from B<buf> to BIO B<b>.
+
+BIO_puts() attempts to write a null terminated string B<buf> to BIO B<b>
+
+=head1 RETURN VALUES
+
+All these functions return either the amount of data successfully read or
+written (if the return value is positive) or that no data was successfully
+read or written (if the result is zero or negative).
+
+=head1 NOTES
+
+A negative or zero return is not necessarily an indication of an error. In
+particular when the source/sink is non-blocking or of a certain type (for
+example an SSL BIO can retry even if the underlying connection is blocking)
+it may merely be an indication that no data is currently available and that
+the application should retry the operation later. L<BIO_should_retry(3)|BIO_should_retry(3)>
+can be called to determine the precise cause.
+
+If the BIO_gets() function is not supported by a BIO then it possible to
+work around this by adding a buffering BIO L<BIO_f_buffer(3)|BIO_f_buffer(3)>
+to the chain.
+
+=head1 SEE ALSO
+
+TBA