Share the store's digest between its files

1 files changed, 1 insertions, 70 deletions

diff --git a/store/store-tree.c b/store/store-tree.c
index 0f83f27..b9ae847 100644
--- a/store/store-tree.c
+++ b/store/store-tree.c
@@ -15,6 +15,7 @@
 #endif
 #include "store.h"
 #include "state.h"
+#include "digest.h"
 #include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
@@ -80,9 +81,6 @@ typedef struct {
 /* A commit's bytes are start..end (none for a file synced whole before it was
  * published); check is their digest. */
 typedef struct { uint64_t seq, end, catalog, catalog_bytes, live, start, check; } Head;
-/* The xxHash64 construction without a seed: four multiply-rotate lanes over
- * 32-byte stripes, several GB/s. An all-zero Digest is an empty one. */
-typedef struct { uint64_t lane[4], length; unsigned char held[32]; size_t count; } Digest;
 typedef struct {
     int fd;
     uint64_t at; /* file offset of the next byte */
@@ -130,73 +128,6 @@ static void encode64(unsigned char *bytes, uint64_t value) {
     for (unsigned i = 0; i < 8; ++i) bytes[i] = (unsigned char)(value >> (8 * i));
 }
 
-static uint64_t load64(const unsigned char *bytes) {
-    uint64_t value;
-    memcpy(&value, bytes, 8);
-#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-    value = __builtin_bswap64(value);
-#endif
-    return value;
-}
-
-/* Digests find torn and missing writes; they are not a defence against a
- * hostile file. */
-static const uint64_t P1 = UINT64_C(0x9E3779B185EBCA87), P2 = UINT64_C(0xC2B2AE3D27D4EB4F),
-                      P3 = UINT64_C(0x165667B19E3779F9), P4 = UINT64_C(0x85EBCA77C2B2AE63),
-                      P5 = UINT64_C(0x27D4EB2F165667C5);
-
-static uint64_t rotate(uint64_t value, unsigned bits) { return value << bits | value >> (64 - bits); }
-static uint64_t mix(uint64_t lane, uint64_t word) { return rotate(lane + word * P2, 31) * P1; }
-
-static void stripes(Digest *digest, const unsigned char *bytes, size_t count) {
-    uint64_t a = digest->lane[0], b = digest->lane[1], c = digest->lane[2], d = digest->lane[3];
-    for (; count; --count, bytes += 32) {
-        a = mix(a, load64(bytes));
-        b = mix(b, load64(bytes + 8));
-        c = mix(c, load64(bytes + 16));
-        d = mix(d, load64(bytes + 24));
-    }
-    digest->lane[0] = a, digest->lane[1] = b, digest->lane[2] = c, digest->lane[3] = d;
-}
-
-static void digest_add(Digest *digest, const unsigned char *bytes, size_t length) {
-    digest->length += length;
-    if (digest->count) {
-        size_t take = 32 - digest->count < length ? 32 - digest->count : length;
-        memcpy(digest->held + digest->count, bytes, take);
-        digest->count += take;
-        bytes += take;
-        length -= take;
-        if (digest->count < 32) return;
-        stripes(digest, digest->held, 1);
-        digest->count = 0;
-    }
-    stripes(digest, bytes, length / 32);
-    digest->count = length % 32;
-    if (digest->count) memcpy(digest->held, bytes + length - digest->count, digest->count);
-}
-
-static uint64_t digest_end(const Digest *digest) {
-    const uint64_t *lane = digest->lane;
-    uint64_t hash = rotate(lane[0], 1) + rotate(lane[1], 7) + rotate(lane[2], 12) + rotate(lane[3], 18);
-    for (unsigned i = 0; i < 4; ++i) hash = (hash ^ mix(0, lane[i])) * P1 + P4;
-    hash += digest->length;
-    size_t i = 0;
-    for (; i + 8 <= digest->count; i += 8) hash = rotate(hash ^ mix(0, load64(digest->held + i)), 27) * P1 + P4;
-    for (; i < digest->count; ++i) hash = rotate(hash ^ digest->held[i] * P5, 11) * P1;
-    hash ^= hash >> 33;
-    hash *= P2;
-    hash ^= hash >> 29;
-    hash *= P3;
-    return hash ^ hash >> 32;
-}
-
-static uint64_t digest_of(const unsigned char *bytes, size_t length) {
-    Digest digest = {0};
-    digest_add(&digest, bytes, length);
-    return digest_end(&digest);
-}
-
 #ifdef PURE_STORE_TEST
 static unsigned long syncs;
 unsigned long pure_tree_test_syncs(void) { return __atomic_load_n(&syncs, __ATOMIC_RELAXED); }