upb/hash/common.h

// Protocol Buffers - Google's data interchange format
// Copyright 2023 Google LLC.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

/*
 * upb_table
 *
 * This header is INTERNAL-ONLY!  Its interfaces are not public or stable!
 * This file defines very fast int->upb_value (inttable) and string->upb_value
 * (strtable) hash tables.
 *
 * The table uses chained scatter with Brent's variation (inspired by the Lua
 * implementation of hash tables).  The hash function for strings is Austin
 * Appleby's "MurmurHash."
 *
 * The inttable uses uintptr_t as its key, which guarantees it can be used to
 * store pointers or integers of at least 32 bits (upb isn't really useful on
 * systems where sizeof(void*) < 4).
 *
 * The table must be homogeneous (all values of the same type).  In debug
 * mode, we check this on insert and lookup.
 */

#ifndef UPB_HASH_COMMON_H_
#define UPB_HASH_COMMON_H_

#include <string.h>

#include "upb/base/string_view.h"
#include "upb/mem/arena.h"

// Must be last.
#include "upb/port/def.inc"

#ifdef __cplusplus
extern "C" {
#endif

/* upb_value ******************************************************************/

typedef struct {
  uint64_t val;
} upb_value;

UPB_INLINE void _upb_value_setval(upb_value* v, uint64_t val) { v->val = val; }

/* For each value ctype, define the following set of functions:
 *
 * // Get/set an int32 from a upb_value.
 * int32_t upb_value_getint32(upb_value val);
 * void upb_value_setint32(upb_value *val, int32_t cval);
 *
 * // Construct a new upb_value from an int32.
 * upb_value upb_value_int32(int32_t val); */
#define FUNCS(name, membername, type_t, converter)                   \
  UPB_INLINE void upb_value_set##name(upb_value* val, type_t cval) { \
    val->val = (converter)cval;                                      \
  }                                                                  \
  UPB_INLINE upb_value upb_value_##name(type_t val) {                \
    upb_value ret;                                                   \
    upb_value_set##name(&ret, val);                                  \
    return ret;                                                      \
  }                                                                  \
  UPB_INLINE type_t upb_value_get##name(upb_value val) {             \
    return (type_t)(converter)val.val;                               \
  }

FUNCS(int32, int32, int32_t, int32_t)
FUNCS(int64, int64, int64_t, int64_t)
FUNCS(uint32, uint32, uint32_t, uint32_t)
FUNCS(uint64, uint64, uint64_t, uint64_t)
FUNCS(bool, _bool, bool, bool)
FUNCS(cstr, cstr, char*, uintptr_t)
FUNCS(uintptr, uptr, uintptr_t, uintptr_t)
FUNCS(ptr, ptr, void*, uintptr_t)
FUNCS(constptr, constptr, const void*, uintptr_t)

#undef FUNCS

UPB_INLINE void upb_value_setfloat(upb_value* val, float cval) {
  memcpy(&val->val, &cval, sizeof(cval));
}

UPB_INLINE void upb_value_setdouble(upb_value* val, double cval) {
  memcpy(&val->val, &cval, sizeof(cval));
}

UPB_INLINE upb_value upb_value_float(float cval) {
  upb_value ret;
  upb_value_setfloat(&ret, cval);
  return ret;
}

UPB_INLINE upb_value upb_value_double(double cval) {
  upb_value ret;
  upb_value_setdouble(&ret, cval);
  return ret;
}

/* upb_tabkey *****************************************************************/

/* Either:
 *   1. an actual integer key, or
 *   2. a pointer to a string prefixed by its uint32_t length, owned by us.
 *
 * ...depending on whether this is a string table or an int table.  We would
 * make this a union of those two types, but C89 doesn't support statically
 * initializing a non-first union member. */
typedef uintptr_t upb_tabkey;

UPB_INLINE char* upb_tabstr(upb_tabkey key, uint32_t* len) {
  char* mem = (char*)key;
  if (len) memcpy(len, mem, sizeof(*len));
  return mem + sizeof(*len);
}

UPB_INLINE upb_StringView upb_tabstrview(upb_tabkey key) {
  upb_StringView ret;
  uint32_t len;
  ret.data = upb_tabstr(key, &len);
  ret.size = len;
  return ret;
}

/* upb_tabval *****************************************************************/

typedef struct upb_tabval {
  uint64_t val;
} upb_tabval;

#define UPB_TABVALUE_EMPTY_INIT \
  { -1 }

/* upb_table ******************************************************************/

typedef struct _upb_tabent {
  upb_tabkey key;
  upb_tabval val;

  /* Internal chaining.  This is const so we can create static initializers for
   * tables.  We cast away const sometimes, but *only* when the containing
   * upb_table is known to be non-const.  This requires a bit of care, but
   * the subtlety is confined to table.c. */
  const struct _upb_tabent* next;
} upb_tabent;

typedef struct {
  size_t count;       /* Number of entries in the hash part. */
  uint32_t mask;      /* Mask to turn hash value -> bucket. */
  uint32_t max_count; /* Max count before we hit our load limit. */
  uint8_t size_lg2;   /* Size of the hashtable part is 2^size_lg2 entries. */
  upb_tabent* entries;
} upb_table;

UPB_INLINE size_t upb_table_size(const upb_table* t) {
  return t->size_lg2 ? 1 << t->size_lg2 : 0;
}

// Internal-only functions, in .h file only out of necessity.

UPB_INLINE bool upb_tabent_isempty(const upb_tabent* e) { return e->key == 0; }

uint32_t _upb_Hash(const void* p, size_t n, uint64_t seed);

#ifdef __cplusplus
} /* extern "C" */
#endif

#include "upb/port/undef.inc"

#endif /* UPB_HASH_COMMON_H_ */