Add randombytes wrappers.

These are real wrappers, not globals or macros, in order to make it easier
to use them in different programming languages.

src/libsodium/include/sodium/randombytes.h

@@ -12,12 +12,12 @@ extern "C" {
 #include <stdio.h>
 
 typedef struct randombytes_implementation {
-    const char (**randombytes_implementation_name)(void);
-    uint32_t   (*randombytes_random)(void);
-    void       (*randombytes_stir)(void);
-    uint32_t   (*randombytes_uniform)(const uint32_t upper_bound);
-    void       (*randombytes_buf)(void * const buf, const size_t size);
-    int        (*randombytes_close)(void);
+    const char *(*randombytes_implementation_name)(void);
+    uint32_t    (*randombytes_random)(void);
+    void        (*randombytes_stir)(void);
+    uint32_t    (*randombytes_uniform)(const uint32_t upper_bound);
+    void        (*randombytes_buf)(void * const buf, const size_t size);
+    int         (*randombytes_close)(void);
 } randombytes_implementation;
 
 int         randombytes_set_implementation(randombytes_implementation *impl);

src/libsodium/include/sodium/salsa20_random.h

@@ -9,11 +9,13 @@
 extern "C" {
 #endif
 
-uint32_t  salsa20_random(void);
-void      salsa20_random_stir(void);
-uint32_t  salsa20_random_uniform(const uint32_t upper_bound);
-void      salsa20_random_buf(void * const buf, const size_t size);
-int       salsa20_random_close(void);
+const char *salsa20_random_implementation_name(void);
+
+uint32_t    salsa20_random(void);
+void        salsa20_random_stir(void);
+uint32_t    salsa20_random_uniform(const uint32_t upper_bound);
+void        salsa20_random_buf(void * const buf, const size_t size);
+int         salsa20_random_close(void);
 
 #ifdef __cplusplus
 }

src/libsodium/randombytes/randombytes.c

@@ -7,9 +7,54 @@
 #include "randombytes.h"
 #include "salsa20_random.h"
 
+static randombytes_implementation implementation = {
+    .randombytes_implementation_name = salsa20_random_implementation_name,
+    .randombytes_random = salsa20_random,
+    .randombytes_stir = salsa20_random_stir,
+    .randombytes_uniform = salsa20_random_uniform,
+    .randombytes_buf = salsa20_random_buf,
+    .randombytes_close = salsa20_random_close
+};
+
+const char *
+randombytes_implementation_name(void)
+{
+    return implementation.randombytes_implementation_name();
+}
+
+uint32_t
+randombytes_random(void)
+{
+    return implementation.randombytes_random();
+}
+
+void
+randombytes_stir(void)
+{
+    return implementation.randombytes_stir();
+}
+
+uint32_t
+randombytes_uniform(const uint32_t upper_bound)
+{
+    return implementation.randombytes_uniform(upper_bound);
+}
+
+void
+randombytes_buf(void * const buf, const size_t size)
+{
+    return implementation.randombytes_buf(buf, size);
+}
+
+int
+randombytes_close(void)
+{
+    return implementation.randombytes_close();
+}
+
 void
 randombytes(unsigned char * const buf, const unsigned long long buf_len)
 {
     assert(buf_len <= SIZE_MAX);
-    salsa20_random_buf(buf, buf_len);
+    randombytes_buf(buf, (size_t) buf_len);
 }

src/libsodium/randombytes/salsa20_random.c

@@ -306,3 +306,9 @@ salsa20_random_uniform(const uint32_t upper_bound)
     }
     return r % upper_bound;
 }
+
+const char *
+salsa20_random_implementation_name(void)
+{
+    return "salsa20_random";
+}