/*!@file
  \brief   STON Hash Tables
  \details Aligned general purpose hash functions and memory definitions
           whose columns are provided, and whose rows, and sizes, are derived.

             ht_size = header.ht_columns << header.ht_2pow;
             ht_rows = 0x1 << header.ht_2pow;

           All generic hashtables in henge must have a power-of-two number of
           rows.  An ht_columns value that is also a power-of-two will result in
           a power-of-two sized memory imprint for the structure, making it easy
           to page align.

           Elements in the columns may be of any arbitrary size.

             typedef uint32_t my_ht_type;
             ht_bytes = ht_size * sizeof(my_ht_type);

           implementation covers only 32-bit unit sizes.

  \author  Ken Grimes
  \date    Feb 2017
  ----------------------------------------------------------------------------*/
#ifndef _STON_HT_T_
#define _STON_HT_T_
/* Define STON_NOSTATIC to expose included function symbols */
#ifndef STON_NOSTATIC
#define STON_FUNC_STATIC static
#else
#define STON_FUNC_STATIC
#endif //STON_NOSTATIC
/* If GNUC is detected, uses attributes to stop inlining */
#ifdef  __GNUC__
#define STON_FUNC_NOINLINE __attribute__ ((noinline))
#else
#define STON_FUNC_NOINLINE
#endif //__GNUC__
/* Define STON_NOINLINE to prevent inline compiler hints */
#ifndef STON_NOINLINE
#define STON_FUNC_INLINE inline
#else
#define STON_FUNC_INLINE
#endif //STON_NOINLINE
/* Define STON_FUNC to override the default STON Function attributes */
#ifndef STON_FUNC
#define STON_FUNC STON_FUNC_STATIC STON_FUNC_INLINE
#endif //STON_FUNC
#ifdef STON_HT_FREAD
#include <stdio.h>
#include <errno.h>
#include <alloca.h>
STON_FUNC_STATIC
STON_FUNC_NOINLINE
ston_ht   ston_ht32_fread(FILE*,long,void*(*)(size_t));
STON_FUNC_STATIC
STON_FUNC_NOINLINE
size_t    ston_ht32_fwrite(ston_ht,FILE*,long);
#else
#include <stddef.h>
#endif //STON_HT_FREAD
#include <stdint.h>
#include <string.h> //mem*
/* STON Hashtable Structure
   Hashtables are stored as dynamically sized two dimensional arrays
*/
typedef struct ston_ht_header_t
{ uint16_t ht_columns;
  uint8_t  ht_2pow, ht_flags;
}ston_ht_h,* ston_ht;

STON_FUNC
uint32_t  ston_up2pow(uint32_t);
STON_FUNC
uint8_t   ston_trailing0(uint32_t);
STON_FUNC
ston_ht   ston_ht32_create(uint16_t,uint8_t,uint8_t,void*(*)(size_t));
STON_FUNC
uint32_t* ston_ht32_row(ston_ht,uint32_t);
STON_FUNC
uint32_t  ston_ht32_insert(ston_ht,uint32_t,uint16_t,uint32_t);
STON_FUNC
size_t    ston_ht32_insertx(ston_ht,uint32_t,uint32_t*,size_t,size_t);

#define   ston_ht32_new(_COL,_N,_F,_FN) (ston_ht32_create(_COL,ston_trailing0(ston_up2pow(_N << 1)),_F,_FN))
#define   ston_ht32_entry(_HT,_KEY,_COL) (ston_ht32_row(_HT,_KEY) + _COL)
#define   ston_ht_size(_HT)            ((_HT)->ht_columns << (_HT)->ht_2pow)
#define   ston_ht_rows(_HT)            (0x1 << (_HT)->ht_2pow)
#define   ston_ht_cols(_HT)            ((_HT)->ht_columns)
#define   ston_ht_start(_HT)           ((uint8_t*)((_HT) + 1))
#define   ston_ht_keyrow(_HT,_KEY)     ((_KEY) & (ston_ht_rows(ht) - 1))
#define   ston_ht32_start(_HT)         ((uint32_t*)ston_ht_start(_HT))
#define   ston_ht32_end(_HT)           (ston_ht32_start(_HT) + ston_ht_size(_HT))
#define   ston_ht32_size(_HT)          (ston_ht_size(_HT) * sizeof(uint32_t))

/** @see http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2 */
STON_FUNC
uint32_t ston_up2pow
( uint32_t val )
{ val = (val << 1) - 1;
  val |= val >> 1;
  val |= val >> 2;
  val |= val >> 4;
  val |= val >> 8;
  val |= val >> 16;
  return ++val;
}

/** @see https://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightParallel */
STON_FUNC
uint8_t ston_trailing0
( uint32_t v )
{ uint8_t c = 32;
  v &= -(int32_t)v;
  if (v) c--;
  if (v & 0x0000FFFF) c -= 16;
  if (v & 0x00FF00FF) c -= 8;
  if (v & 0x0F0F0F0F) c -= 4;
  if (v & 0x33333333) c -= 2;
  if (v & 0x55555555) c -= 1;
  return c;
}

/* Creates a new hash table, provided a memory allocation function that takes a
   single size_t bytes, a column count, and a row count which determines the
   size of the table.

   use ston_ht32_new to specify the exact or estimated number of unique keys
   held in the table.  With ston_ht32_new, the provided ht_rows is doubled, and
   rounded up to the nearest power of two to create a hash table with minimal
   collisions.
*/
STON_FUNC
ston_ht ston_ht32_create
( uint16_t ht_columns,
  uint8_t  ht_2pow,
  uint8_t  ht_flags,
  void*    (*alloc_fn)(size_t)
)
{ size_t  ht_bytes = (ht_columns << ht_2pow) * sizeof(uint32_t);
  ston_ht ht = (ston_ht) alloc_fn(sizeof(ston_ht_h) + ht_bytes);
  if (ht != NULL)
    { ht->ht_columns = ht_columns;
      ht->ht_2pow = ht_2pow;
      ht->ht_flags = ht_flags;
      memset(ht + 1, 0, ht_bytes);
    }
  return ht;
}

#ifdef STON_HT_FREAD
/* Reads a 32-bit hash table out of the provided file at the provide fpos, into
   a buffer allocated by alloc_fn.  Memory is allocated to the stack until the
   entire structure is verified, and all file operations are finished.  
   Returns NULL with properly set errno on failure.
*/
STON_FUNC_STATIC
STON_FUNC_NOINLINE
ston_ht ston_ht32_fread
( FILE* file,
  long  fpos,
  void* (*alloc_fn)(size_t)
)
{ struct ston_ht_header_t header;
  ston_ht                 stack_ht, ht;
  long                    fpos_start;
  size_t                  table_size, alloc_size;
  int                     errno_local;
  if ((fpos_start = ftell(file)) == -1)
    return NULL;
  if (fread(&header, sizeof(header), 1, file) != 1)
    goto fail_seekback;
  table_size = ston_ht32_size(&header);
  alloc_size = sizeof(header) + table_size;
  stack_ht = (ston_ht) alloca(alloc_size);
  memcpy(stack_ht, &header, sizeof(header));
  if (fread(stack_ht + sizeof(header), table_size, 1, file) != 1)
    goto fail_seekback;
  if (fseek(file, fpos_start, SEEK_SET) != 0)
    return NULL;
  ht = (ston_ht) alloc_fn(alloc_size);
  if (ht != NULL)
    memcpy(ht, stack_ht, alloc_size);
  return ht;
 fail_seekback:
  /* Try to seek the file back to origin without clobbering errno */
  errno_local = errno;
  fseek(file, fpos_start, SEEK_SET);
  errno = errno_local;
  return NULL;
}

/* Writes a 32-bit hash table from memory into a file at fpos.  Returns the
   number of bytes written to the file, errno is set on error. */
STON_FUNC_STATIC
STON_FUNC_NOINLINE
size_t ston_ht32_fwrite
( struct ston_ht_header_t* ht,
  FILE*                    file,
  long                     fpos
)
{ size_t bytes_written;
  long   fpos_start;
  if ((fpos_start = ftell(file)) == NULL
      || fseek(file, fpos, SEEK_SET) == 0
      || (bytes_written = fwrite(file, 1, sizeof(ston_ht_h), file)) < sizeof(ston_ht_h)
      || (bytes_written += fwrite(file, 1, ston_ht32_bytes(ht), file)) < (sizeof(ston_ht_h) + ston_ht32_bytes(ht))
      || fseek(file, fpos_start, SEEK_SET) == 0)
    return 0;
  return bytes_written;
}
#endif

/* Returns a pointer to the row of data in the hashtable containing the provided
   key, inserts if not found.  Returns NULL on overflow.
*/
STON_FUNC
uint32_t* ston_ht32_row
( struct ston_ht_header_t* ht,
  uint32_t                key
)
{ uint32_t* row;
  uint32_t* row_start = ston_ht32_start(ht);
  uint32_t* row_end = ston_ht32_end(ht);
  uint16_t  ht_cols = ston_ht_cols(ht);
  size_t    row_number = ston_ht_keyrow(ht,key);
  uint8_t   looped = 0;
  row = row_start + (row_number * ht_cols);
 next_row:
  if (row[0] != 0)
    goto populated;
 write_position:
  row[0] = key;
  return row;
 populated:
  if (row[0] == key)
    goto write_position;
  if (row + ht_cols < row_end)
    row += ht_cols;
  else if (looped)
      return NULL;
  else
    { looped++;
      row = row_start;
    }
  goto next_row;
}

/* Inserts a value into a hashtable at the specified column, returning the
   previous value */
STON_FUNC
uint32_t ston_ht32_insert
( struct ston_ht_header_t* ht,
  uint32_t                key,
  uint16_t                column,
  uint32_t                value
)
{ uint32_t* value_location, old_value;
  value_location = ston_ht32_entry(ht,key,column);
  old_value = *value_location;
  *value_location = value;
  return old_value;
}

/* Inserts a row of units into a hashtable, starting with the specified column.
   Returns the number of elements that were written.  This function will not
   overflow internal buffers, but will return a short count (lower than the
   provided 'units') when truncation of source data occurs. */
STON_FUNC
size_t
ston_ht32_insertx
( struct ston_ht_header_t* ht,
  uint32_t                 key,
  uint32_t*                data_src,
  size_t                   start_column,
  size_t                   units
)
{ uint32_t* data_row = ston_ht32_row(ht,key);
  uint32_t* data_limit = data_row + ston_ht_cols(ht);
  uint32_t* data_trg = data_row + start_column;
  if (data_row == NULL)
    return 0;
  while (units-- && data_trg < data_limit)
    *data_trg++ = *data_src++;
  return (size_t)(data_trg - data_row);
}


/* STON Dynamic Hashtable Structure
   A dynamic form of the generic hashtable implementation above which uses
   external allocation.
*/
typedef struct ston_dht_header_t
{ uint16_t  val_bytes;
  uint8_t   key_bytes;
  uint8_t   flags;
}ston_dht_h;

typedef struct ston_dht_t
{ ston_dht_h header;
  void*      (*ht_alloc)(size_t);
  void       (*ht_free)(void*);
  void       (*ht_iter)(void*,void*,void*);
  void*      ht_user_data;
  void*      bucket_root;
  size_t     rowsize, bucketsize;
}* ston_dht;

STON_FUNC
ston_dht  ston_dht_new(uint16_t,uint8_t,void*(*)(size_t),void(*)(void*));
STON_FUNC
ston_dht  ston_dht_free(ston_dht);
STON_FUNC
void*     ston_dht_val(ston_dht,void*);
STON_FUNC_STATIC
STON_FUNC_NOINLINE
void      ston_dht_free_bucket(ston_dht,void*);
STON_FUNC
void      ston_dht_iterate(ston_dht,void(*)(void*,void*,void*),void*);
STON_FUNC_STATIC
STON_FUNC_NOINLINE
void      ston_dht_iterate_r(ston_dht,void*);

// Compatibility macros
#define ston_dht32_new(_COL,_ALOC,_FRE) (ston_dht_new(4 * _COL, 4, _ALOC, _FRE))
#define ston_dht32_row(_HT,_K) ((uint32_t*)((uint8_t*)ston_dht_val(_HT,&(_K)) - 4))
#define ston_dht32_insertx(_HT,_K,_VP,_OFFS,_N) \
  memcpy((uint32_t*)((uint8_t*)ston_dht_val(_HT,&(_K)) + ((_OFFS - 1) * 4)),_VP,_N * 4)

/* Creates a new bucketted hash table, provided a memory allocation function
   that takes a single size_t bytes, a memory free function, a column count, and
   a row count which determines the size of the buckets.
*/
STON_FUNC
ston_dht ston_dht_new
( uint16_t val_bytes,
  uint8_t  key_bytes,
  void*    (*ht_alloc)(size_t),
  void     (*ht_free)(void*)
)
{ ston_dht ht = (ston_dht) ht_alloc(sizeof(struct ston_dht_t));
  if (ht != NULL)
    { ht->header.val_bytes = val_bytes;
      ht->header.key_bytes = key_bytes;
      ht->rowsize = sizeof(void*) + key_bytes + val_bytes;
      ht->bucketsize = ht->rowsize * 0x100;
      ht->ht_alloc = ht_alloc;
      ht->ht_free = ht_free;
      ht->bucket_root = ht_alloc(ht->bucketsize);
      if (ht->bucket_root == NULL && ht_free != NULL)
	ht_free(ht);
      else
	memset((ht->bucket_root), 0, ht->bucketsize);
    }
  return ht;
}


/* Returns a pointer to the value in the hashtable matching the provided key,
   inserting if not found, or NULL if a memory error occurs */
STON_FUNC
void* ston_dht_val
( struct ston_dht_t* ht,
  void*              key
)
{ size_t   key_bytes = ht->header.key_bytes;
  uint8_t* key_byte = (uint8_t*)key;
  uint8_t* bucket = (uint8_t*)ht->bucket_root;
  uint8_t** bucketp;
  uint8_t* row,* a,* b;
  uint8_t  a_not_empty;
  size_t   i;
 next_row:
  row = bucket + (ht->rowsize * (*key_byte));
  a = row + sizeof(void*);
  b = (uint8_t*)key;
  a_not_empty = 0;
  for (i = 0; i < key_bytes; i++)
    { a_not_empty |= a[i];
      if (a_not_empty && a[i] != b[i])
	goto next_bucket;
    }
  if (!a_not_empty)
    memcpy(row + sizeof(void*),key,key_bytes);
  goto done;
 next_bucket:
  key_byte++;
  bucketp = (uint8_t**)row;
  if (*bucketp == NULL)
    { if ((*bucketp = ht->ht_alloc(ht->bucketsize)) == NULL)
	return NULL;
      else
	memset(*bucketp,0,ht->bucketsize);
    }
  bucket = *bucketp;
  goto next_row;
 done:
  return (void*) row + sizeof(void*) + key_bytes;
}

/* Free the dynamic hash table */
STON_FUNC
struct ston_dht_t* ston_dht_free
( struct ston_dht_t* ht )
{ void (*ht_free)(void*) = ht->ht_free;
  if (ht_free == NULL)
    return NULL;
  ston_dht_free_bucket(ht, ht->bucket_root);
  ht_free(ht);
  return ht;
}

/* Recursively free pages by lookup */
STON_FUNC_STATIC
STON_FUNC_NOINLINE
void ston_dht_free_bucket
( struct ston_dht_t* ht,
  void*              bucket
)
{ void** bucket_cur = (void**)((uint8_t*)bucket);
  void** bucket_max = (void**)((uint8_t*)bucket_cur + (ht->rowsize * 0x100));
  while (bucket_cur < bucket_max)
    { if (*bucket_cur != NULL)
	ston_dht_free_bucket(ht, *bucket_cur);
      bucket_cur = (void**)((uint8_t*)bucket_cur + ht->rowsize);
    }
  ht->ht_free(bucket);
}

/* Iterate over each key/value pair and execut 'fn' with key and value as
   arguments */
STON_FUNC
void ston_dht_iterate
( struct ston_dht_t* ht,
  void               (*fn)(void*,void*,void*),
  void*              user_data
)
{ ht->ht_iter = fn;
  ht->ht_user_data = user_data;
  ston_dht_iterate_r(ht,(void**)ht->bucket_root);
}

/* Recursively iterate through the given bucket belonging to hashtable ht */
STON_FUNC_STATIC
STON_FUNC_NOINLINE
void ston_dht_iterate_r
( struct ston_dht_t* ht,
  void*              bucket
)
{ uint8_t* row = (uint8_t*)bucket;
  uint8_t* row_max = (row + (ht->rowsize * 0x100));
  while (row < row_max)
    { if (*(void**)row != NULL)
	ston_dht_iterate_r(ht, *(void**)row);
      row += sizeof(void*);
      ht->ht_iter((void*)row, (void*)(row + ht->header.key_bytes),ht->ht_user_data);
      row += ht->header.key_bytes + ht->header.val_bytes;
    }
}

#endif //_STON_HT_H_