New functions BN_CTX_start(), BN_CTX_get(), BN_CTX_end() to access

temporary BIGNUMs. BN_CTX still uses a fixed number of BIGNUMs, but
the BN_CTX implementation could now easily be changed.

3 files changed, 52 insertions, 1 deletions

diff --git a/doc/crypto/BN_CTX_new.pod b/doc/crypto/BN_CTX_new.pod
index 37a188e3c3..2a02da03b9 100644
--- a/doc/crypto/BN_CTX_new.pod
+++ b/doc/crypto/BN_CTX_new.pod
@@ -38,7 +38,8 @@ BN_CTX_init() and BN_CTX_free() have no return values.
 
 =head1 SEE ALSO
 
-L<bn(3)|bn(3)>, L<err(3)|err(3)>, L<BN_add(3)|BN_add(3)>
+L<bn(3)|bn(3)>, L<err(3)|err(3)>, L<BN_add(3)|BN_add(3)>,
+L<BN_CTX_start(3)|BN_CTX_start(3)>
 
 =head1 HISTORY
 
diff --git a/doc/crypto/BN_CTX_start.pod b/doc/crypto/BN_CTX_start.pod
new file mode 100644
index 0000000000..3e1032375f
--- /dev/null
+++ b/doc/crypto/BN_CTX_start.pod
@@ -0,0 +1,49 @@
+=pod
+
+=head1 NAME
+
+BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
+
+=head1 SYNOPSIS
+
+ #include <openssl/bn.h>
+
+ void BN_CTX_start(BN_CTX *ctx);
+
+ BIGNUM *BN_CTX_get(BN_CTX *ctx);
+
+ void BN_CTX_end(BN_CTX *ctx);
+
+=head1 DESCRIPTION
+
+These functions are used to obtain temporary B<BIGNUM> variables from
+a B<BN_CTX> in order to save the overhead of repeatedly creating and
+freeing B<BIGNUM>s in functions that are called from inside a loop.
+
+A function must call BN_CTX_start() first. Then, BN_CTX_get() may be
+called repeatedly to obtain temporary B<BIGNUM>s. All BN_CTX_get()
+calls must be made before calling any other functions that use the
+B<ctx> as an argument.
+
+Finally, BN_CTX_end() must be called before returning from the function.
+When BN_CTX_end() is called, the B<BIGNUM> pointers obtained from
+BN_CTX_get() become invalid.
+
+=head1 RETURN VALUES
+
+BN_CTX_start() and BN_CTX_end() return no values.
+
+BN_CTX_get() returns a pointer to the B<BIGNUM>, or B<NULL> on error.
+Once BN_CTX_get() has failed, the subsequent calls will return B<NULL>
+as well, so it is sufficient to check the return value of the last
+BN_CTX_get() call.
+
+=head1 SEE ALSO
+
+L<BN_CTX_new(3)|BN_CTX_new(3)>
+
+=head1 HISTORY
+
+BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added in OpenSSL 0.9.5.
+
+=cut
diff --git a/doc/crypto/BN_add.pod b/doc/crypto/BN_add.pod
index 2f6a3b448f..e4230851e4 100644
--- a/doc/crypto/BN_add.pod
+++ b/doc/crypto/BN_add.pod
@@ -40,6 +40,7 @@ B<r> may be the same B<BIGNUM> as B<a> or B<b>.
 BN_sub() subtracts B<b> from B<a> and places the result in B<r> (C<r=a-b>).
 
 BN_mul() multiplies B<a> and B<b> and places the result in B<r> (C<r=a*b>).
+B<r> may be the same B<BIGNUM> as B<a> or B<b>.
 For multiplication by powers of 2, use L<BN_lshift(3)|BN_lshift(3)>.
 
 BN_div() divides B<a> by B<d> and places the result in B<dv> and the