src: add cleaner md5 API

This API is intended to replace the existing MD5 hashing API.
It uses properly prefixed functions and has documentation.

include/vlc_hash.h

@@ -0,0 +1,146 @@
+/*****************************************************************************
+ * vlc_hash.h: Hash functions
+ *****************************************************************************
+ * Copyright © 2004-2020 VLC authors and VideoLAN
+ *
+ * Authors: Rémi Denis-Courmont
+ *          Rafaël Carré
+ *          Marvin Scholz
+ *
+ * This program 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 program 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, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifndef VLC_HASH_H
+# define VLC_HASH_H
+
+#include <vlc_md5.h>
+
+/**
+ * \defgroup vlc_hash  Hash functions
+ * APIs for simple and frequently used hash algorithms in VLC
+ * 
+ * Each hash algorithm has a context object which stores all data needed for the
+ * hash calculation, this context is not supposed to be modified directly by the
+ * called but only with the functions listed here.
+ *
+ * Supported hash algorithms:
+ *   - \ref vlc_hash_md5 "MD5"
+ *
+ * @{
+ */
+
+/**
+ * \defgroup vlc_hash_utils  Helper functions
+ * Functions commonly used together with hashing functions
+ * @{
+ */
+
+/**
+ * Finish hash computation and return hex representation
+ *
+ * Finishes the hash computation and provides the hash for the
+ * concatenation of all provided data in hex encoded format.
+ * The result is written to the buffer pointed to by output, which
+ * must be larger than twice the size of the hash output.
+ *
+ * \param[in,out] ctx    Hash context to finish
+ * \param[out]    output Output buffer to write the string to
+ */
+#ifndef __cplusplus
+#define vlc_hash_FinishHex(ctx, output)                             \
+    do {                                                            \
+        char out_tmp[_Generic((ctx),                                \
+            vlc_hash_md5_t *: VLC_HASH_MD5_DIGEST_SIZE)];           \
+        _Generic((ctx),                                             \
+            vlc_hash_md5_t *: vlc_hash_md5_Finish)                  \
+        (ctx, out_tmp, sizeof(out_tmp));                            \
+        vlc_hex_encode_binary(out_tmp, sizeof(out_tmp), output);    \
+    } while (0)
+#endif
+
+/**
+ * @}
+ */
+
+/**
+ * \defgroup vlc_hash_md5  MD5 hashing
+ * APIs to hash data using the Message-Digest Algorithm 5 (MD5)
+ * @{
+ */
+
+/**
+ * MD5 hash context
+ */
+typedef struct vlc_hash_md5_ctx
+{
+    struct md5_s priv; /**< \internal Private */
+} vlc_hash_md5_t;
+
+/**
+ * MD5 digest output size
+ */
+#define VLC_HASH_MD5_DIGEST_SIZE 16
+
+/**
+ * MD5 digest hex representation size
+ */
+#define VLC_HASH_MD5_DIGEST_HEX_SIZE 33 // 2 chars per byte + null
+
+/**
+ * Initialize MD5 context
+ * 
+ * Initializes the given MD5 hash function context, if the context is
+ * already initialized, it is reset.
+ * 
+ * \param[out] ctx  MD5 hash context to init
+ */
+VLC_API void vlc_hash_md5_Init(vlc_hash_md5_t *ctx);
+
+/**
+ * Update MD5 hash computation with new data
+ * 
+ * Updates the context with provided data which is used for the hash
+ * calculation. Can be called repeatedly with new data. The final
+ * hash represents the hash for the concatenation of all data.
+ * 
+ * \param[in,out] ctx    MD5 hash context to update
+ * \param         data   Data to add
+ * \param         size   Size of the data to add
+ */
+VLC_API void vlc_hash_md5_Update(vlc_hash_md5_t *ctx, const void *data, size_t size);
+
+/**
+ * Finish MD5 hash computation
+ * 
+ * Finishes the MD5 hash computation and provides the hash for the
+ * concatenation of all provided data by previous calls to \ref vlc_hash_md5_Update.
+ * The result is written to the buffer pointed to by output, which must be at
+ * least \ref VLC_HASH_MD5_DIGEST_SIZE big.
+ * 
+ * \param[in,out] ctx    MD5 hash context to finish
+ * \param[out]    output Output buffer to write to
+ * \param         size   Output buffer size
+ */
+VLC_API void vlc_hash_md5_Finish(vlc_hash_md5_t *ctx, void *output, size_t size);
+
+/**
+ * @}
+ */
+
+/**
+ * @}
+ */
+
+#endif

src/Makefile.am

@@ -54,6 +54,7 @@ pluginsinclude_HEADERS = \
 	../include/vlc_fs.h \
 	../include/vlc_gcrypt.h \
 	../include/vlc_opengl.h \
+	../include/vlc_hash.h \
 	../include/vlc_http.h \
 	../include/vlc_httpd.h \
 	../include/vlc_image.h \

src/libvlccore.sym

@@ -141,6 +141,9 @@ httpd_HandlerNew
 httpd_HostDelete
 vlc_http_HostNew
 vlc_https_HostNew
+vlc_hash_md5_Init
+vlc_hash_md5_Update
+vlc_hash_md5_Finish
 vlc_rtsp_HostNew
 httpd_MsgAdd
 httpd_MsgGet

src/misc/md5.c

@@ -40,9 +40,10 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
 
 #include <vlc_common.h>
-#include <vlc_md5.h>
+#include <vlc_hash.h>
 
 typedef uint32_t u32;
 typedef uint8_t byte;
@@ -347,3 +348,21 @@ void EndMD5( struct md5_s *h )
 {
     md5_final( h );
 }
+
+/* New API */
+void vlc_hash_md5_Init(vlc_hash_md5_t *ctx)
+{
+    md5_init(&ctx->priv);
+}
+
+void vlc_hash_md5_Update(vlc_hash_md5_t *ctx, const void *data, size_t length)
+{
+    md5_write(&ctx->priv, data, length);
+}
+
+void vlc_hash_md5_Finish(vlc_hash_md5_t *ctx, void *output, size_t size)
+{
+    assert(size >= VLC_HASH_MD5_DIGEST_SIZE);
+    md5_final(&ctx->priv);
+    memcpy(output, ctx->priv.buf, VLC_HASH_MD5_DIGEST_SIZE);
+}