From fa9e13139f2290625b5e3e244da2f14d0b33730f Mon Sep 17 00:00:00 2001
From: Matthew Wampler-Doty <matthew.wampler.doty@gmail.com>
Date: Tue, 10 Mar 2015 15:24:54 -0400
Subject: [PATCH] Introducing get_seedhash

---
 ethash.h   | 7 ++++++-
 internal.c | 7 +++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/ethash.h b/ethash.h
index 5491f4a4e..bcbe2d7ef 100644
--- a/ethash.h
+++ b/ethash.h
@@ -68,26 +68,31 @@ void ethash_mkcache(ethash_cache *cache, ethash_params const *params, const uint
 void ethash_compute_full_data(void *mem, ethash_params const *params, ethash_cache const *cache);
 void ethash_full(ethash_return_value *ret, void const *full_mem, ethash_params const *params, const uint8_t header_hash[32], const uint64_t nonce);
 void ethash_light(ethash_return_value *ret, ethash_cache const *cache, ethash_params const *params, const uint8_t header_hash[32], const uint64_t nonce);
+void ethash_get_seedhash(uint8_t seedhash[32], const uint32_t block_number);
 
 static inline void ethash_prep_light(void *cache, ethash_params const *params, const uint8_t seed[32]) {
     ethash_cache c;
     c.mem = cache;
     ethash_mkcache(&c, params, seed);
 }
+
 static inline void ethash_compute_light(ethash_return_value *ret, void const *cache, ethash_params const *params, const uint8_t header_hash[32], const uint64_t nonce) {
     ethash_cache c;
     c.mem = (void *) cache;
     ethash_light(ret, &c, params, header_hash, nonce);
 }
+
 static inline void ethash_prep_full(void *full, ethash_params const *params, void const *cache) {
     ethash_cache c;
     c.mem = (void *) cache;
     ethash_compute_full_data(full, params, &c);
 }
+
 static inline void ethash_compute_full(ethash_return_value *ret, void const *full, ethash_params const *params, const uint8_t header_hash[32], const uint64_t nonce) {
     ethash_full(ret, full, params, header_hash, nonce);
 }
 
+// Returns if hash is less than or equal to difficulty
 static inline int ethash_check_difficulty(
         const uint8_t hash[32],
         const uint8_t difficulty[32]) {
@@ -96,7 +101,7 @@ static inline int ethash_check_difficulty(
         if (hash[i] == difficulty[i]) continue;
         return hash[i] < difficulty[i];
     }
-    return 0;
+    return 1;
 }
 
 int ethash_quick_check_difficulty(
diff --git a/internal.c b/internal.c
index cba08d116..3144bf8d6 100644
--- a/internal.c
+++ b/internal.c
@@ -273,6 +273,13 @@ void ethash_quick_hash(
     SHA3_256(return_hash, buf, 64 + 32);
 }
 
+void ethash_get_seedhash(uint8_t seedhash[32], const uint32_t block_number) {
+    memset(seedhash,0,32);
+    const uint32_t epochs = block_number / EPOCH_LENGTH;
+    for (uint32_t i = 0 ; i < epochs ; ++i)
+        SHA3_256(seedhash, seedhash, 32);
+}
+
 int ethash_quick_check_difficulty(
         const uint8_t header_hash[32],
         const uint64_t nonce,