Add OPENSSL_hexstr2buf_ex() and OPENSSL_buf2hexstr_ex()

They do the same thing as OPENSSL_hexstr2buf() and OPENSSL_buf2hexstr(),
except they take a result buffer from the caller.

We take the opportunity to break out the documentation of the hex to /
from buffer conversion routines from the OPENSSL_malloc() file to its
own file.  These routines aren't memory allocation routines per se.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9303)

1 files changed, 74 insertions, 0 deletions

diff --git a/doc/man3/OPENSSL_hexchar2int.pod b/doc/man3/OPENSSL_hexchar2int.pod
new file mode 100644
index 0000000000..930b32b61f
--- /dev/null
+++ b/doc/man3/OPENSSL_hexchar2int.pod
@@ -0,0 +1,74 @@
+=pod
+
+=head1 NAME
+
+OPENSSL_hexchar2int,
+OPENSSL_hexstr2buf_ex, OPENSSL_hexstr2buf,
+OPENSSL_buf2hexstr_ex, OPENSSL_buf2hexstr
+- Hex encoding and decoding functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/crypto.h>
+
+ int OPENSSL_hexchar2int(unsigned char c);
+ int OPENSSL_hexstr2buf_ex(unsigned char *buf, size_t buf_n, long *buflen,
+                           const char *str);
+ unsigned char *OPENSSL_hexstr2buf(const char *str, long *len);
+ int OPENSSL_buf2hexstr_ex(char *str, size_t str_n, size_t *strlen,
+                           const unsigned char *buf, long buflen);
+ char *OPENSSL_buf2hexstr(const unsigned char *buf, long buflen);
+
+=head1 DESCRIPTION
+
+OPENSSL_hexchar2int() converts a hexadecimal character to its numeric
+equivalent.
+
+OPENSSL_hexstr2buf_ex() decodes the hex string B<str> and places the
+resulting string of bytes in the given I<buf>.
+I<buf_n> gives the size of the buffer.
+If I<buflen> is not NULL, it is filled in with the result length.
+To find out how large the result will be, call this function with NULL
+for I<buf>.
+Colons between two-character hex "bytes" are accepted and ignored.
+An odd number of hex digits is an error.
+
+OPENSSL_hexstr2buf() does the same thing as OPENSSL_hexstr2buf_ex(),
+but allocates the space for the result, and returns the result.
+The memory is allocated by calling OPENSSL_malloc() and should be
+released by calling OPENSSL_free().
+
+OPENSSL_buf2hexstr_ex() encodes the contents of the given I<buf> with
+length I<buflen> and places the resulting hexadecimal character string
+in the given I<str>.
+I<str_n> gives the size of the of the string buffer.
+If I<strlen> is not NULL, it is filled in with the result length.
+To find out how large the result will be, call this function with NULL
+for I<str>.
+
+OPENSSL_buf2hexstr() does the same thing as OPENSSL_buf2hexstr_ex(),
+but allocates the space for the result, and returns the result.
+The memory is allocated by calling OPENSSL_malloc() and should be
+released by calling OPENSSL_free().
+
+=head1 RETURN VALUES
+
+OPENSSL_hexchar2int returns the value of a decoded hex character,
+or -1 on error.
+
+OPENSSL_buf2hexstr() and OPENSSL_hexstr2buf()
+return a pointer to allocated memory, or NULL on error.
+
+OPENSSL_buf2hexstr_ex() and OPENSSL_hexstr2buf_ex() return 1 on
+success, or 0 on error.
+
+=head1 COPYRIGHT
+
+Copyright 2016-2019 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the Apache License 2.0 (the "License").  You may not use
+this file except in compliance with the License.  You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
+=cut