Small secure random changes

Author: yoniko

lib/common/random.h

@@ -11,6 +11,8 @@
 #ifndef ZSTD_RANDOM_H
 #define ZSTD_RANDOM_H
 
+#include "mem.h"
+
 /*
  * Portability helpers for secure random, exposes the following:
  * - `HAS_SECURE_RANDOM` a macro that determines if secure random API is available on
@@ -24,10 +26,11 @@
 
 #define HAS_SECURE_RANDOM
 #include <sys/random.h>
-static size_t getSecureRandom(void *buf, size_t buflen) {
+MEM_STATIC size_t getSecureRandom(void *buf, size_t buflen) {
     return getrandom(buf, buflen, GRND_NONBLOCK) != (ssize_t) buflen;
 }
 
+
 #endif
 
 

lib/compress/zstd_compress.c

@@ -1910,6 +1910,10 @@ ZSTD_reset_matchState(ZSTD_matchState_t* ms,
             int needTagTableInit = 1;
 #ifdef HAS_SECURE_RANDOM
             if(forWho == ZSTD_resetTarget_CCtx) {
+                /* TODO: We might not need to generate secure random everytime. For example,
+                 * we could generate 256 bit of secure random and roll it using a cryptographic
+                 * hash function. This optimization could lend some performance wins for very
+                 * small inputs. */
                 size_t randomGenerated = getSecureRandom(&ms->hashSalt, sizeof(ms->hashSalt));
                 if (!randomGenerated) {
                     /* We've successfully generated secure random, so we don't need to explicitly memset