shachain: add shachain_next_index()

[ccan] / ccan / crypto / shachain / shachain.c

diff --git a/ccan/crypto/shachain/shachain.c b/ccan/crypto/shachain/shachain.c
index c6bd37e8f55c76cd72a2720669e8083d4d4585fe..d4508a05a0f7addf2e33442ff1f13d3564bab9e7 100644 (file)
--- a/ccan/crypto/shachain/shachain.c
+++ b/ccan/crypto/shachain/shachain.c
@@ -5,8 +5,6 @@
 #include <string.h>
 #include <assert.h>
 
-#define INDEX_BITS ((sizeof(shachain_index_t)) * CHAR_BIT)
-
 static void change_bit(unsigned char *arr, size_t index)
 {
        arr[index / CHAR_BIT] ^= (1 << (index % CHAR_BIT));
@@ -15,11 +13,11 @@ static void change_bit(unsigned char *arr, size_t index)
 static unsigned int count_trailing_zeroes(shachain_index_t index)
 {
 #if HAVE_BUILTIN_CTZLL
-       return index ? (unsigned int)__builtin_ctzll(index) : INDEX_BITS;
+       return index ? (unsigned int)__builtin_ctzll(index) : SHACHAIN_BITS;
 #else
        unsigned int i;
 
-       for (i = 0; i < INDEX_BITS; i++) {
+       for (i = 0; i < SHACHAIN_BITS; i++) {
                if (index & (1ULL << i))
                        break;
        }
@@ -68,10 +66,16 @@ void shachain_from_seed(const struct sha256 *seed, shachain_index_t index,
        derive(0, index, seed, hash);
 }
 
+shachain_index_t shachain_next_index(const struct shachain *chain)
+{
+       return chain->min_index - 1;
+}
+
 void shachain_init(struct shachain *chain)
 {
        chain->num_valid = 0;
-       chain->min_index = 0;
+       /* This is 0 in the case where SHACHAIN_BITS is 64. */
+       chain->min_index = (shachain_index_t)((UINT64_MAX >> (64 - SHACHAIN_BITS)) + 1);
 }
 
 bool shachain_add_hash(struct shachain *chain,
@@ -80,8 +84,7 @@ bool shachain_add_hash(struct shachain *chain,
        unsigned int i, pos;
 
        /* You have to insert them in order! */
-       assert(index == chain->min_index - 1 ||
-              (index == (shachain_index_t)(-1ULL) && chain->num_valid == 0));
+       assert(index == shachain_next_index(chain));
 
        pos = count_trailing_zeroes(index);