hasher: add HASHER_SAPLING_PREIMAGE

hasher.c

@@ -56,7 +56,10 @@ void hasher_Init(Hasher *hasher, HasherType type) {
 		blake2b_InitPersonal(&hasher->ctx.blake2b, 32, "ZcashOutputsHash", 16);
 		break;
 	case HASHER_OVERWINTER_PREIMAGE:
-		blake2b_InitPersonal(&hasher->ctx.blake2b, 32, "ZcashSigHash\x19\x1b\xa8\x5b", 16);  // BRANCH_ID = 0x5ba81b19
+		blake2b_InitPersonal(&hasher->ctx.blake2b, 32, "ZcashSigHash\x19\x1b\xa8\x5b", 16);  // BRANCH_ID = 0x5ba81b19 / Overwinter
+		break;
+	case HASHER_SAPLING_PREIMAGE:
+		blake2b_InitPersonal(&hasher->ctx.blake2b, 32, "ZcashSigHash\xbb\x09\xb8\x76", 16);  // BRANCH_ID = 0x76b809bb / Sapling
 		break;
 	}
 }
@@ -90,6 +93,7 @@ void hasher_Update(Hasher *hasher, const uint8_t *data, size_t length) {
 	case HASHER_OVERWINTER_SEQUENCE:
 	case HASHER_OVERWINTER_OUTPUTS:
 	case HASHER_OVERWINTER_PREIMAGE:
+	case HASHER_SAPLING_PREIMAGE:
 		blake2b_Update(&hasher->ctx.blake2b, data, length);
 		break;
 	}
@@ -134,6 +138,7 @@ void hasher_Final(Hasher *hasher, uint8_t hash[HASHER_DIGEST_LENGTH]) {
 	case HASHER_OVERWINTER_SEQUENCE:
 	case HASHER_OVERWINTER_OUTPUTS:
 	case HASHER_OVERWINTER_PREIMAGE:
+	case HASHER_SAPLING_PREIMAGE:
 		blake2b_Final(&hasher->ctx.blake2b, hash, 32);
 		break;
 	}

hasher.h

@@ -54,6 +54,7 @@ typedef enum {
     HASHER_OVERWINTER_SEQUENCE,
     HASHER_OVERWINTER_OUTPUTS,
     HASHER_OVERWINTER_PREIMAGE,
+    HASHER_SAPLING_PREIMAGE,
 } HasherType;
 
 typedef struct {
@@ -64,7 +65,7 @@ typedef struct {
         SHA3_CTX sha3;          // for HASHER_SHA3{,K}
         BLAKE256_CTX blake;     // for HASHER_BLAKE{,D}
         GROESTL512_CTX groestl; // for HASHER_GROESTLD_TRUNC
-        BLAKE2B_CTX blake2b;    // for HASHER_OVERWINTER_*
+        BLAKE2B_CTX blake2b;    // for HASHER_OVERWINTER_*, HASHER_SAPLING_*
     } ctx;
 } Hasher;