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+/* af_alg.h - Compute message digests from file streams and buffers.
+ Copyright (C) 2018-2022 Free Software Foundation, Inc.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ This file is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* Written by Matteo Croce <mcroce@redhat.com>, 2018.
+ Documentation by Bruno Haible <bruno@clisp.org>, 2018. */
+
+/* Declare specific functions for computing message digests
+ using the Linux kernel crypto API, if available. This kernel API gives
+ access to specialized crypto instructions (that would also be available
+ in user space) or to crypto devices (not directly available in user space).
+
+ For a more complete set of facilities that use the Linux kernel crypto API,
+ look at libkcapi. */
+
+#ifndef AF_ALG_H
+# define AF_ALG_H 1
+
+# include <stdio.h>
+# include <errno.h>
+
+# ifdef __cplusplus
+extern "C" {
+# endif
+
+# if USE_LINUX_CRYPTO_API
+
+/* Compute a message digest of a memory region.
+
+ The memory region starts at BUFFER and is LEN bytes long.
+
+ ALG is the message digest algorithm; see the file /proc/crypto.
+
+ RESBLOCK points to a block of HASHLEN bytes, for the result.
+ HASHLEN must be the length of the message digest, in bytes, in particular:
+
+ alg | hashlen
+ -------+--------
+ md5 | 16
+ sha1 | 20
+ sha224 | 28
+ sha256 | 32
+ sha384 | 48
+ sha512 | 64
+
+ If successful, fill RESBLOCK and return 0.
+ Upon failure, return a negated error number. */
+int
+afalg_buffer (const char *buffer, size_t len, const char *alg,
+ void *resblock, ssize_t hashlen);
+
+/* Compute a message digest of data read from STREAM.
+
+ STREAM is an open file stream. The last operation on STREAM should
+ not be 'ungetc', and if STREAM is also open for writing it should
+ have been fflushed since its last write. Read from the current
+ position to the end of STREAM. Handle regular files efficiently.
+
+ ALG is the message digest algorithm; see the file /proc/crypto.
+
+ RESBLOCK points to a block of HASHLEN bytes, for the result.
+ HASHLEN must be the length of the message digest, in bytes, in particular:
+
+ alg | hashlen
+ -------+--------
+ md5 | 16
+ sha1 | 20
+ sha224 | 28
+ sha256 | 32
+ sha384 | 48
+ sha512 | 64
+
+ If successful, fill RESBLOCK and return 0.
+ Upon failure, return a negated error number.
+ Unless returning 0 or -EIO, restore STREAM's file position so that
+ the caller can fall back on some other method. */
+int
+afalg_stream (FILE *stream, const char *alg,
+ void *resblock, ssize_t hashlen);
+
+# else
+
+static inline int
+afalg_buffer (const char *buffer, size_t len, const char *alg,
+ void *resblock, ssize_t hashlen)
+{
+ return -EAFNOSUPPORT;
+}
+
+static inline int
+afalg_stream (FILE *stream, const char *alg,
+ void *resblock, ssize_t hashlen)
+{
+ return -EAFNOSUPPORT;
+}
+
+# endif
+
+# ifdef __cplusplus
+}
+# endif
+
+#endif /* AF_ALG_H */