From 97353ebddc1395f737874d7f9af608efccfbecbc Mon Sep 17 00:00:00 2001
From: Dmitrii Krosh <gudovdo@my.msu.ru>
Date: Mon, 3 Aug 2026 11:39:14 +0300
Subject: [PATCH] new hash_set reimplement

---
 new_version/direct_hash/hash_set.c | 504 +++++++++++++++++++++++++++++
 new_version/main_ideas.md          |   1 +
 2 files changed, 505 insertions(+)
 create mode 100644 new_version/direct_hash/hash_set.c

diff --git a/new_version/direct_hash/hash_set.c b/new_version/direct_hash/hash_set.c
new file mode 100644
index 0000000..019275b
--- /dev/null
+++ b/new_version/direct_hash/hash_set.c
@@ -0,0 +1,504 @@
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include "rpmlib.h"
+#include "set.h"
+#include "system.h"
+
+/*
+ * This is intentionally a new set-string format. It is not compatible with
+ * the Golomb-Rice/base62 strings produced by the original lib/set.c.
+ *
+ *   D1<two decimal bpp digits><RFC 4648 base64 of packed hashes>
+ *
+ * Sorted unique hashes are packed least-significant bit first, using exactly
+ * bpp bits per hash. Base64 is only a textual representation of those bytes;
+ * there is no delta or Golomb-Rice coding.
+ */
+#define FORMAT_PREFIX "D1"
+#define FORMAT_HEADER_LEN 4
+
+struct set {
+  size_t cnt;
+  size_t symbols_cap;
+  size_t strings_len;
+  size_t strings_cap;
+  char* strings;
+  struct symbols {
+    size_t offset;
+    unsigned hash;
+  }* symbols_v;
+};
+
+struct decoded_set {
+  unsigned* hashes;
+  size_t count;
+  unsigned bpp;
+};
+
+struct set* set_new(void) {
+  struct set* set = xmalloc(sizeof(*set));
+  set->cnt = 0;
+  set->symbols_cap = 0;
+  set->strings_len = 0;
+  set->strings_cap = 0;
+  set->strings = NULL;
+  set->symbols_v = NULL;
+  return set;
+}
+
+void set_add(struct set* set, const char* sym) {
+  if (set->cnt == set->symbols_cap) {
+    set->symbols_cap += 1024;
+    set->symbols_v = xrealloc(set->symbols_v, sizeof(*set->symbols_v) * set->symbols_cap);
+  }
+
+  size_t length = strlen(sym) + 1;
+  size_t required = set->strings_len + length;
+  if (required > set->strings_cap) {
+    size_t capacity = set->strings_cap ? set->strings_cap : 4096;
+    while (capacity < required) capacity *= 2;
+    set->strings = xrealloc(set->strings, capacity);
+    set->strings_cap = capacity;
+  }
+
+  set->symbols_v[set->cnt].offset = set->strings_len;
+  set->symbols_v[set->cnt].hash = 0;
+  memcpy(set->strings + set->strings_len, sym, length);
+  set->strings_len = required;
+  ++set->cnt;
+}
+
+struct set* set_free(struct set* set) {
+  if (set) {
+    _free(set->strings);
+    _free(set->symbols_v);
+    set = _free(set);
+  }
+  return NULL;
+}
+
+static unsigned hash(const char* str) {
+  unsigned hash = UINT32_C(0x9e3779b9);
+  const unsigned char* p = (const unsigned char*)str;
+
+  while (*p) {
+    hash += *p++;
+    hash += hash << 10;
+    hash ^= hash >> 6;
+  }
+
+  hash += hash << 3;
+  hash ^= hash >> 11;
+  hash += hash << 15;
+  return hash;
+}
+
+static int compare_symbols(const void* arg1, const void* arg2) {
+  const struct symbols* s1 = arg1;
+  const struct symbols* s2 = arg2;
+
+  if (s1->hash > s2->hash) return 1;
+  if (s1->hash < s2->hash) return -1;
+  return 0;
+}
+
+static void sort_symbols(struct symbols* values, size_t count, unsigned bpp) {
+  if (count < 128) {
+    qsort(values, count, sizeof(*values), compare_symbols);
+    return;
+  }
+
+  struct symbols* temporary = xmalloc(count * sizeof(*temporary));
+  struct symbols* source = values;
+  struct symbols* destination = temporary;
+  unsigned passes = (bpp + 7) / 8;
+
+  for (unsigned pass = 0; pass < passes; ++pass) {
+    size_t offsets[256] = {0};
+    unsigned shift = pass * 8;
+    for (size_t i = 0; i < count; ++i) ++offsets[(source[i].hash >> shift) & 0xffu];
+
+    size_t position = 0;
+    for (size_t i = 0; i < 256; ++i) {
+      size_t bucket_count = offsets[i];
+      offsets[i] = position;
+      position += bucket_count;
+    }
+
+    for (size_t i = 0; i < count; ++i) {
+      unsigned bucket = (source[i].hash >> shift) & 0xffu;
+      destination[offsets[bucket]++] = source[i];
+    }
+
+    struct symbols* swap = source;
+    source = destination;
+    destination = swap;
+  }
+
+  if (source != values) memcpy(values, source, count * sizeof(*values));
+  _free(temporary);
+}
+
+static const char base64_alphabet[] =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+static size_t base64_encoded_size(size_t byte_count) {
+  if (byte_count > SIZE_MAX - 2) abort();
+  size_t groups = (byte_count + 2) / 3;
+  if (groups > (SIZE_MAX - FORMAT_HEADER_LEN - 1) / 4) abort();
+  return groups * 4;
+}
+
+static void base64_encode(const unsigned char* input, size_t input_len, char* output) {
+  while (input_len >= 3) {
+    uint32_t value = ((uint32_t)input[0] << 16) | ((uint32_t)input[1] << 8) | input[2];
+    output[0] = base64_alphabet[(value >> 18) & 0x3f];
+    output[1] = base64_alphabet[(value >> 12) & 0x3f];
+    output[2] = base64_alphabet[(value >> 6) & 0x3f];
+    output[3] = base64_alphabet[value & 0x3f];
+    input += 3;
+    input_len -= 3;
+    output += 4;
+  }
+
+  if (input_len == 1) {
+    uint32_t value = (uint32_t)input[0] << 16;
+    output[0] = base64_alphabet[(value >> 18) & 0x3f];
+    output[1] = base64_alphabet[(value >> 12) & 0x3f];
+    output[2] = '=';
+    output[3] = '=';
+  } else if (input_len == 2) {
+    uint32_t value = ((uint32_t)input[0] << 16) | ((uint32_t)input[1] << 8);
+    output[0] = base64_alphabet[(value >> 18) & 0x3f];
+    output[1] = base64_alphabet[(value >> 12) & 0x3f];
+    output[2] = base64_alphabet[(value >> 6) & 0x3f];
+    output[3] = '=';
+  }
+}
+
+static unsigned char* pack_hashes(const unsigned* hashes, size_t count, unsigned bpp,
+                                  size_t* byte_count) {
+  if (count > (SIZE_MAX - 7) / bpp) abort();
+  size_t bit_count = count * bpp;
+  *byte_count = (bit_count + 7) / 8;
+  unsigned char* bytes = xmalloc(*byte_count);
+  unsigned char* output = bytes;
+  uint64_t bits = 0;
+  unsigned filled = 0;
+
+  for (size_t i = 0; i < count; ++i) {
+    bits |= (uint64_t)hashes[i] << filled;
+    filled += bpp;
+    while (filled >= 8) {
+      *output++ = (unsigned char)bits;
+      bits >>= 8;
+      filled -= 8;
+    }
+  }
+  if (filled) *output++ = (unsigned char)bits;
+  assert((size_t)(output - bytes) == *byte_count);
+  return bytes;
+}
+
+const char* set_fini(struct set* set, int bpp) {
+  assert(set != NULL);
+  assert(set->cnt > 0);
+  assert(bpp >= 10 && bpp <= 32);
+
+  unsigned mask = bpp < 32 ? (UINT32_C(1) << bpp) - 1 : UINT32_MAX;
+  for (size_t i = 0; i < set->cnt; ++i) {
+    set->symbols_v[i].hash = hash(set->strings + set->symbols_v[i].offset) & mask;
+  }
+  sort_symbols(set->symbols_v, set->cnt, (unsigned)bpp);
+
+  for (size_t i = 0; i + 1 < set->cnt; ++i) {
+    if (set->symbols_v[i].hash != set->symbols_v[i + 1].hash) continue;
+    const char* left = set->strings + set->symbols_v[i].offset;
+    const char* right = set->strings + set->symbols_v[i + 1].offset;
+    if (strcmp(left, right) != 0) fprintf(stderr, "warning: hash collision: %s %s\n", left, right);
+  }
+
+  unsigned* unique_hashes = xmalloc(set->cnt * sizeof(*unique_hashes));
+  size_t unique_count = 0;
+  for (size_t i = 0; i < set->cnt; ++i) {
+    while (i + 1 < set->cnt && set->symbols_v[i].hash == set->symbols_v[i + 1].hash) ++i;
+    unique_hashes[unique_count++] = set->symbols_v[i].hash;
+  }
+
+  size_t byte_count;
+  unsigned char* bytes = pack_hashes(unique_hashes, unique_count, (unsigned)bpp, &byte_count);
+  size_t payload_len = base64_encoded_size(byte_count);
+  char* output = xmalloc(FORMAT_HEADER_LEN + payload_len + 1);
+  memcpy(output, FORMAT_PREFIX, sizeof(FORMAT_PREFIX) - 1);
+  output[2] = (char)('0' + bpp / 10);
+  output[3] = (char)('0' + bpp % 10);
+  base64_encode(bytes, byte_count, output + FORMAT_HEADER_LEN);
+  output[FORMAT_HEADER_LEN + payload_len] = '\0';
+
+  _free(bytes);
+  _free(unique_hashes);
+  return output;
+}
+
+static int base64_value(unsigned char c) {
+  if (c >= 'A' && c <= 'Z') return c - 'A';
+  if (c >= 'a' && c <= 'z') return c - 'a' + 26;
+  if (c >= '0' && c <= '9') return c - '0' + 52;
+  if (c == '+') return 62;
+  if (c == '/') return 63;
+  return -1;
+}
+
+static int base64_decode(const char* input, size_t input_len, unsigned char** bytes,
+                         size_t* byte_count) {
+  if (input_len == 0 || input_len % 4 != 0) return -1;
+  if (input_len / 4 > SIZE_MAX / 3) return -1;
+
+  size_t capacity = input_len / 4 * 3;
+  unsigned char* output = xmalloc(capacity);
+  unsigned char* destination = output;
+
+  for (size_t offset = 0; offset < input_len; offset += 4) {
+    int v0 = base64_value((unsigned char)input[offset]);
+    int v1 = base64_value((unsigned char)input[offset + 1]);
+    int last = offset + 4 == input_len;
+    if (v0 < 0 || v1 < 0) goto invalid;
+
+    *destination++ = (unsigned char)((v0 << 2) | (v1 >> 4));
+    if (input[offset + 2] == '=') {
+      if (!last || input[offset + 3] != '=' || (v1 & 0x0f) != 0) goto invalid;
+      continue;
+    }
+
+    int v2 = base64_value((unsigned char)input[offset + 2]);
+    if (v2 < 0) goto invalid;
+    *destination++ = (unsigned char)((v1 << 4) | (v2 >> 2));
+    if (input[offset + 3] == '=') {
+      if (!last || (v2 & 0x03) != 0) goto invalid;
+      continue;
+    }
+
+    int v3 = base64_value((unsigned char)input[offset + 3]);
+    if (v3 < 0) goto invalid;
+    *destination++ = (unsigned char)((v2 << 6) | v3);
+  }
+
+  *bytes = output;
+  *byte_count = (size_t)(destination - output);
+  return 0;
+
+invalid:
+  _free(output);
+  return -1;
+}
+
+static int decode_set(const char* str, struct decoded_set* decoded) {
+  if (strncmp(str, "set:", 4) == 0) str += 4;
+  size_t str_len = strlen(str);
+  if (str_len <= FORMAT_HEADER_LEN) return -1;
+  if (strncmp(str, FORMAT_PREFIX, sizeof(FORMAT_PREFIX) - 1) != 0) return -1;
+  if (str[2] < '0' || str[2] > '9' || str[3] < '0' || str[3] > '9') return -1;
+
+  unsigned bpp = (unsigned)(str[2] - '0') * 10 + (unsigned)(str[3] - '0');
+  if (bpp < 10 || bpp > 32) return -1;
+
+  unsigned char* bytes;
+  size_t byte_count;
+  if (base64_decode(str + FORMAT_HEADER_LEN, str_len - FORMAT_HEADER_LEN, &bytes, &byte_count) < 0)
+    return -1;
+  if (byte_count > SIZE_MAX / 8) {
+    _free(bytes);
+    return -1;
+  }
+
+  size_t count = byte_count * 8 / bpp;
+  if (count == 0 || count > (SIZE_MAX - 7) / bpp || (count * bpp + 7) / 8 != byte_count) {
+    _free(bytes);
+    return -1;
+  }
+
+  unsigned* hashes = xmalloc(count * sizeof(*hashes));
+  const unsigned char* input = bytes;
+  const unsigned char* input_end = bytes + byte_count;
+  uint64_t bits = 0;
+  unsigned filled = 0;
+  uint64_t mask = bpp < 32 ? (UINT64_C(1) << bpp) - 1 : UINT32_MAX;
+
+  for (size_t i = 0; i < count; ++i) {
+    while (filled < bpp) {
+      if (input == input_end) {
+        _free(hashes);
+        _free(bytes);
+        return -1;
+      }
+      bits |= (uint64_t)*input++ << filled;
+      filled += 8;
+    }
+    hashes[i] = (unsigned)(bits & mask);
+    bits >>= bpp;
+    filled -= bpp;
+    if (i > 0 && hashes[i - 1] >= hashes[i]) {
+      _free(hashes);
+      _free(bytes);
+      return -1;
+    }
+  }
+
+  while (input < input_end) {
+    bits |= (uint64_t)*input++ << filled;
+    filled += 8;
+  }
+  _free(bytes);
+  if (bits != 0) {
+    _free(hashes);
+    return -1;
+  }
+
+  decoded->hashes = hashes;
+  decoded->count = count;
+  decoded->bpp = bpp;
+  return 0;
+}
+
+/* Reduce a sorted set of (bpp + 1)-bit values to a sorted set of bpp-bit values. */
+static size_t downsample_set(size_t count, const unsigned* hashes, unsigned* result, unsigned bpp) {
+  unsigned mask = (UINT32_C(1) << bpp) - 1;
+  size_t lower = 0;
+  size_t upper = count;
+
+  while (lower < upper) {
+    size_t middle = lower + (upper - lower) / 2;
+    if (hashes[middle] <= mask)
+      lower = middle + 1;
+    else
+      upper = middle;
+  }
+
+  unsigned* output = result;
+  const unsigned* low = hashes;
+  const unsigned* low_end = hashes + lower;
+  const unsigned* high = hashes + lower;
+  const unsigned* high_end = hashes + count;
+
+  while (low < low_end && high < high_end) {
+    unsigned low_value = *low;
+    unsigned high_value = *high & mask;
+    if (low_value < high_value) {
+      *output++ = low_value;
+      ++low;
+    } else if (high_value < low_value) {
+      *output++ = high_value;
+      ++high;
+    } else {
+      *output++ = low_value;
+      ++low;
+      ++high;
+    }
+  }
+  while (low < low_end) *output++ = *low++;
+  while (high < high_end) *output++ = *high++ & mask;
+  return (size_t)(output - result);
+}
+
+static void downsample_to(struct decoded_set* set, unsigned target_bpp) {
+  if (set->bpp == target_bpp) return;
+
+  unsigned* original = set->hashes;
+  unsigned* scratch = xmalloc(set->count * sizeof(*scratch));
+  unsigned* source = original;
+  unsigned* destination = scratch;
+
+  while (set->bpp > target_bpp) {
+    --set->bpp;
+    set->count = downsample_set(set->count, source, destination, set->bpp);
+    unsigned* swap = source;
+    source = destination;
+    destination = swap;
+  }
+
+  if (source == original) {
+    _free(scratch);
+  } else {
+    _free(original);
+    set->hashes = scratch;
+  }
+}
+
+static const unsigned* step_lower_bound(const unsigned* first, const unsigned* last, unsigned value,
+                                        size_t jump) {
+  size_t count = (size_t)(last - first);
+  if (count == 0 || first[0] >= value) return first;
+  if (jump == 0) jump = 1;
+
+  size_t position = 0;
+  size_t step = jump;
+  while (step != 0) {
+    if (step > count - position - 1) {
+      step /= 2;
+      continue;
+    }
+    size_t next = position + step;
+    if (first[next] < value)
+      position = next;
+    else
+      step /= 2;
+  }
+  return first + position + 1;
+}
+
+static int sorted_subset(const unsigned* small, size_t small_count, const unsigned* large,
+                         size_t large_count) {
+  const unsigned* small_end = small + small_count;
+  const unsigned* large_end = large + large_count;
+  size_t jump = large_count / small_count;
+
+  if (jump < 4) {
+    while (small < small_end) {
+      unsigned value = *small++;
+      while (large < large_end && *large < value) ++large;
+      if (large == large_end || *large != value) return 0;
+      ++large;
+    }
+    return 1;
+  }
+
+  while (small < small_end) {
+    unsigned value = *small++;
+    large = step_lower_bound(large, large_end, value, jump);
+    if (large == large_end || *large != value) return 0;
+    ++large;
+  }
+  return 1;
+}
+
+int rpmsetcmp(const char* str1, const char* str2) {
+  struct decoded_set set1;
+  struct decoded_set set2;
+  if (decode_set(str1, &set1) < 0) return -3;
+  if (decode_set(str2, &set2) < 0) {
+    _free(set1.hashes);
+    return -4;
+  }
+
+  unsigned target_bpp = set1.bpp < set2.bpp ? set1.bpp : set2.bpp;
+  downsample_to(&set1, target_bpp);
+  downsample_to(&set2, target_bpp);
+
+  int result;
+  if (set1.count == set2.count) {
+    result = memcmp(set1.hashes, set2.hashes, set1.count * sizeof(*set1.hashes)) == 0 ? 0 : -2;
+  } else if (set1.count > set2.count) {
+    result = sorted_subset(set2.hashes, set2.count, set1.hashes, set1.count) ? 1 : -2;
+  } else {
+    result = sorted_subset(set1.hashes, set1.count, set2.hashes, set2.count) ? -1 : -2;
+  }
+
+  _free(set1.hashes);
+  _free(set2.hashes);
+  return result;
+}
diff --git a/new_version/main_ideas.md b/new_version/main_ideas.md
index cf6b6d6..91c7ffd 100644
--- a/new_version/main_ideas.md
+++ b/new_version/main_ideas.md
@@ -6,6 +6,7 @@
 
 ## хранить сразу расшифрованный set
 
+- WIP [здесь](new_version/direct_hash/about.md)
 - огромная часть ресурсов уходит не на просмотр включения множеств, а на декодирование set-строк
   - при возможности хранить больше данных за более дешёвое сравнение - прекрасно
   - тупо условный формат: