mimalloc/include/mimalloc/internal.h

/* ----------------------------------------------------------------------------
Copyright (c) 2018-2023, Microsoft Research, Daan Leijen
This is free software; you can redistribute it and/or modify it under the
terms of the MIT license. A copy of the license can be found in the file
"LICENSE" at the root of this distribution.
-----------------------------------------------------------------------------*/
#pragma once
#ifndef MIMALLOC_INTERNAL_H
#define MIMALLOC_INTERNAL_H


// --------------------------------------------------------------------------
// This file contains the interal API's of mimalloc and various utility
// functions and macros.
// --------------------------------------------------------------------------

#include "types.h"
#include "track.h"
#include "bits.h"

#if (MI_DEBUG>0)
#define mi_trace_message(...)  _mi_trace_message(__VA_ARGS__)
#else
#define mi_trace_message(...)
#endif

#if defined(_MSC_VER)
#pragma warning(disable:4127)   // suppress constant conditional warning (due to MI_SECURE paths)
#pragma warning(disable:26812)  // unscoped enum warning
#pragma warning(disable:28159)  // don't use GetVersion
#pragma warning(disable:4996)   // don't use GetVersion
#define mi_decl_noinline        __declspec(noinline)
#define mi_decl_thread          __declspec(thread)
#define mi_decl_align(a)        __declspec(align(a))
#define mi_decl_weak
#elif (defined(__GNUC__) && (__GNUC__ >= 3)) || defined(__clang__) // includes clang and icc
#define mi_decl_noinline        __attribute__((noinline))
#define mi_decl_thread          __thread
#define mi_decl_align(a)        __attribute__((aligned(a)))
#define mi_decl_weak            __attribute__((weak))
#else
#define mi_decl_noinline
#define mi_decl_thread          __thread        // hope for the best :-)
#define mi_decl_align(a)
#define mi_decl_weak
#endif

#define mi_decl_cache_align     mi_decl_align(64)


#if defined(__EMSCRIPTEN__) && !defined(__wasi__)
#define __wasi__
#endif

#if defined(__cplusplus)
#define mi_decl_externc       extern "C"
#else
#define mi_decl_externc
#endif


// "options.c"
void       _mi_fputs(mi_output_fun* out, void* arg, const char* prefix, const char* message);
void       _mi_fprintf(mi_output_fun* out, void* arg, const char* fmt, ...);
void       _mi_warning_message(const char* fmt, ...);
void       _mi_verbose_message(const char* fmt, ...);
void       _mi_trace_message(const char* fmt, ...);
void       _mi_output_message(const char* fmt, ...);
void       _mi_options_init(void);
long       _mi_option_get_fast(mi_option_t option);
void       _mi_error_message(int err, const char* fmt, ...);

// random.c
void       _mi_random_init(mi_random_ctx_t* ctx);
void       _mi_random_init_weak(mi_random_ctx_t* ctx);
void       _mi_random_reinit_if_weak(mi_random_ctx_t * ctx);
void       _mi_random_split(mi_random_ctx_t* ctx, mi_random_ctx_t* new_ctx);
uintptr_t  _mi_random_next(mi_random_ctx_t* ctx);
uintptr_t  _mi_heap_random_next(mi_heap_t* heap);
uintptr_t  _mi_os_random_weak(uintptr_t extra_seed);
static inline uintptr_t _mi_random_shuffle(uintptr_t x);

// init.c
extern mi_decl_cache_align mi_stats_t       _mi_stats_main;
extern mi_decl_cache_align const mi_page_t  _mi_page_empty;
void       _mi_process_load(void);
void mi_cdecl _mi_process_done(void);
bool       _mi_is_redirected(void);
bool       _mi_allocator_init(const char** message);
void       _mi_allocator_done(void);
bool       _mi_is_main_thread(void);
size_t     _mi_current_thread_count(void);
bool       _mi_preloading(void);           // true while the C runtime is not initialized yet
void       _mi_thread_done(mi_heap_t* heap);
void       _mi_thread_data_collect(void);
void       _mi_tld_init(mi_tld_t* tld, mi_heap_t* bheap);

mi_threadid_t _mi_thread_id(void) mi_attr_noexcept;
size_t        _mi_thread_seq_id(void) mi_attr_noexcept;

mi_heap_t*    _mi_heap_main_get(void);     // statically allocated main backing heap
mi_subproc_t* _mi_subproc_from_id(mi_subproc_id_t subproc_id);
void          _mi_heap_guarded_init(mi_heap_t* heap);

// os.c
void       _mi_os_init(void);                                            // called from process init
void*      _mi_os_alloc(size_t size, mi_memid_t* memid, mi_stats_t* stats);
void*      _mi_os_zalloc(size_t size, mi_memid_t* memid, mi_stats_t* stats);
void       _mi_os_free(void* p, size_t size, mi_memid_t memid, mi_stats_t* stats);
void       _mi_os_free_ex(void* p, size_t size, bool still_committed, mi_memid_t memid, mi_stats_t* stats);

size_t     _mi_os_page_size(void);
size_t     _mi_os_good_alloc_size(size_t size);
bool       _mi_os_has_overcommit(void);
bool       _mi_os_has_virtual_reserve(void);
size_t     _mi_os_virtual_address_bits(void);

bool       _mi_os_reset(void* addr, size_t size, mi_stats_t* tld_stats);
bool       _mi_os_commit(void* p, size_t size, bool* is_zero, mi_stats_t* stats);
bool       _mi_os_decommit(void* addr, size_t size, mi_stats_t* stats);
bool       _mi_os_protect(void* addr, size_t size);
bool       _mi_os_unprotect(void* addr, size_t size);
bool       _mi_os_purge(void* p, size_t size, mi_stats_t* stats);
bool       _mi_os_purge_ex(void* p, size_t size, bool allow_reset, mi_stats_t* stats);

void*      _mi_os_alloc_aligned(size_t size, size_t alignment, bool commit, bool allow_large, mi_memid_t* memid, mi_stats_t* stats);
void*      _mi_os_alloc_aligned_at_offset(size_t size, size_t alignment, size_t align_offset, bool commit, bool allow_large, mi_memid_t* memid, mi_stats_t* tld_stats);

void*      _mi_os_get_aligned_hint(size_t try_alignment, size_t size);
bool       _mi_os_use_large_page(size_t size, size_t alignment);
size_t     _mi_os_large_page_size(void);

void*      _mi_os_alloc_huge_os_pages(size_t pages, int numa_node, mi_msecs_t max_secs, size_t* pages_reserved, size_t* psize, mi_memid_t* memid);

// arena.c
mi_arena_id_t _mi_arena_id_none(void);
void       _mi_arena_init(void);
void       _mi_arena_free(void* p, size_t size, size_t still_committed_size, mi_memid_t memid, mi_stats_t* stats);
void*      _mi_arena_alloc(size_t size, bool commit, bool allow_large, mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_tld_t* tld);
void*      _mi_arena_alloc_aligned(size_t size, size_t alignment, size_t align_offset, bool commit, bool allow_large, mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_tld_t* tld);
bool       _mi_arena_memid_is_suitable(mi_memid_t memid, mi_arena_id_t request_arena_id);
bool       _mi_arena_contains(const void* p);
void       _mi_arenas_collect(bool force_purge, mi_stats_t* stats);
void       _mi_arena_unsafe_destroy_all(mi_stats_t* stats);

mi_page_t* _mi_arena_page_alloc(mi_heap_t* heap, size_t block_size, size_t page_alignment);
void       _mi_arena_page_free(mi_page_t* page);
void       _mi_arena_page_abandon(mi_page_t* page);
void       _mi_arena_page_unabandon(mi_page_t* page);
bool       _mi_arena_page_try_reabandon_to_mapped(mi_page_t* page);

bool       _mi_arena_try_reclaim(mi_heap_t* heap, mi_page_t* page);
void       _mi_arena_reclaim_all_abandoned(mi_heap_t* heap);

void*      _mi_arena_meta_zalloc(size_t size, mi_memid_t* memid);
void       _mi_arena_meta_free(void* p, mi_memid_t memid, size_t size);

/*
typedef struct mi_arena_field_cursor_s { // abstract struct
  size_t         os_list_count;           // max entries to visit in the OS abandoned list
  size_t         start;                   // start arena idx (may need to be wrapped)
  size_t         end;                     // end arena idx (exclusive, may need to be wrapped)
  size_t         bitmap_idx;              // current bit idx for an arena
  mi_subproc_t*  subproc;                 // only visit blocks in this sub-process
  bool           visit_all;               // ensure all abandoned blocks are seen (blocking)
  bool           hold_visit_lock;         // if the subproc->abandoned_os_visit_lock is held
} mi_arena_field_cursor_t;
void          _mi_arena_field_cursor_init(mi_heap_t* heap, mi_subproc_t* subproc, bool visit_all, mi_arena_field_cursor_t* current);
mi_segment_t* _mi_arena_segment_clear_abandoned_next(mi_arena_field_cursor_t* previous);
void          _mi_arena_field_cursor_done(mi_arena_field_cursor_t* current);
*/

// "page-map.c"
bool       _mi_page_map_init(void);
void       _mi_page_map_register(mi_page_t* page);
void       _mi_page_map_unregister(mi_page_t* page);


// "page.c"
void*      _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero, size_t huge_alignment)  mi_attr_noexcept mi_attr_malloc;

void       _mi_page_retire(mi_page_t* page) mi_attr_noexcept;                  // free the page if there are no other pages with many free blocks
void       _mi_page_unfull(mi_page_t* page);
void       _mi_page_free(mi_page_t* page, mi_page_queue_t* pq);               // free the page
void       _mi_page_abandon(mi_page_t* page, mi_page_queue_t* pq);            // abandon the page, to be picked up by another thread...
void       _mi_page_force_abandon(mi_page_t* page);

// void       _mi_heap_delayed_free_all(mi_heap_t* heap);
// bool       _mi_heap_delayed_free_partial(mi_heap_t* heap);
void       _mi_heap_collect_retired(mi_heap_t* heap, bool force);

size_t     _mi_page_queue_append(mi_heap_t* heap, mi_page_queue_t* pq, mi_page_queue_t* append);
void       _mi_deferred_free(mi_heap_t* heap, bool force);

void       _mi_page_free_collect(mi_page_t* page,bool force);
// void       _mi_page_reclaim(mi_heap_t* heap, mi_page_t* page);   // callback from segments
void       _mi_page_init(mi_heap_t* heap, mi_page_t* page);

size_t     _mi_bin_size(uint8_t bin);           // for stats
uint8_t    _mi_bin(size_t size);                // for stats

// "heap.c"
void       _mi_heap_init(mi_heap_t* heap, mi_tld_t* tld, mi_arena_id_t arena_id, bool noreclaim, uint8_t tag);
void       _mi_heap_destroy_pages(mi_heap_t* heap);
void       _mi_heap_collect_abandon(mi_heap_t* heap);
void       _mi_heap_set_default_direct(mi_heap_t* heap);
bool       _mi_heap_memid_is_suitable(mi_heap_t* heap, mi_memid_t memid);
void       _mi_heap_unsafe_destroy_all(void);
mi_heap_t* _mi_heap_by_tag(mi_heap_t* heap, uint8_t tag);
void       _mi_heap_area_init(mi_heap_area_t* area, mi_page_t* page);
bool       _mi_heap_area_visit_blocks(const mi_heap_area_t* area, mi_page_t* page, mi_block_visit_fun* visitor, void* arg);
void       _mi_heap_page_reclaim(mi_heap_t* heap, mi_page_t* page);

// "stats.c"
void       _mi_stats_done(mi_stats_t* stats);
mi_msecs_t  _mi_clock_now(void);
mi_msecs_t  _mi_clock_end(mi_msecs_t start);
mi_msecs_t  _mi_clock_start(void);

// "alloc.c"
void*       _mi_page_malloc_zero(mi_heap_t* heap, mi_page_t* page, size_t size, bool zero) mi_attr_noexcept;  // called from `_mi_malloc_generic`
void*       _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t size) mi_attr_noexcept;                  // called from `_mi_heap_malloc_aligned`
void*       _mi_page_malloc_zeroed(mi_heap_t* heap, mi_page_t* page, size_t size) mi_attr_noexcept;           // called from `_mi_heap_malloc_aligned`
void*       _mi_heap_malloc_zero(mi_heap_t* heap, size_t size, bool zero) mi_attr_noexcept;
void*       _mi_heap_malloc_zero_ex(mi_heap_t* heap, size_t size, bool zero, size_t huge_alignment) mi_attr_noexcept;     // called from `_mi_heap_malloc_aligned`
void*       _mi_heap_realloc_zero(mi_heap_t* heap, void* p, size_t newsize, bool zero) mi_attr_noexcept;
mi_block_t* _mi_page_ptr_unalign(const mi_page_t* page, const void* p);
void        _mi_padding_shrink(const mi_page_t* page, const mi_block_t* block, const size_t min_size);
// bool        _mi_free_delayed_block(mi_block_t* block);


// "libc.c"
#include    <stdarg.h>
void        _mi_vsnprintf(char* buf, size_t bufsize, const char* fmt, va_list args);
void        _mi_snprintf(char* buf, size_t buflen, const char* fmt, ...);
char        _mi_toupper(char c);
int         _mi_strnicmp(const char* s, const char* t, size_t n);
void        _mi_strlcpy(char* dest, const char* src, size_t dest_size);
void        _mi_strlcat(char* dest, const char* src, size_t dest_size);
size_t      _mi_strlen(const char* s);
size_t      _mi_strnlen(const char* s, size_t max_len);
bool        _mi_getenv(const char* name, char* result, size_t result_size);

#if MI_DEBUG>1
bool        _mi_page_is_valid(mi_page_t* page);
#endif


// ------------------------------------------------------
// Branches
// ------------------------------------------------------

#if defined(__GNUC__) || defined(__clang__)
#define mi_unlikely(x)     (__builtin_expect(!!(x),false))
#define mi_likely(x)       (__builtin_expect(!!(x),true))
#elif (defined(__cplusplus) && (__cplusplus >= 202002L)) || (defined(_MSVC_LANG) && _MSVC_LANG >= 202002L)
#define mi_unlikely(x)     (x) [[unlikely]]
#define mi_likely(x)       (x) [[likely]]
#else
#define mi_unlikely(x)     (x)
#define mi_likely(x)       (x)
#endif

#ifndef __has_builtin
#define __has_builtin(x)  0
#endif


/* -----------------------------------------------------------
  Error codes passed to `_mi_fatal_error`
  All are recoverable but EFAULT is a serious error and aborts by default in secure mode.
  For portability define undefined error codes using common Unix codes:
  <https://www-numi.fnal.gov/offline_software/srt_public_context/WebDocs/Errors/unix_system_errors.html>
----------------------------------------------------------- */
#include <errno.h>
#ifndef EAGAIN         // double free
#define EAGAIN (11)
#endif
#ifndef ENOMEM         // out of memory
#define ENOMEM (12)
#endif
#ifndef EFAULT         // corrupted free-list or meta-data
#define EFAULT (14)
#endif
#ifndef EINVAL         // trying to free an invalid pointer
#define EINVAL (22)
#endif
#ifndef EOVERFLOW      // count*size overflow
#define EOVERFLOW (75)
#endif


/* -----------------------------------------------------------
  Inlined definitions
----------------------------------------------------------- */
#define MI_UNUSED(x)     (void)(x)
#if (MI_DEBUG>0)
#define MI_UNUSED_RELEASE(x)
#else
#define MI_UNUSED_RELEASE(x)  MI_UNUSED(x)
#endif

#define MI_INIT4(x)   x(),x(),x(),x()
#define MI_INIT8(x)   MI_INIT4(x),MI_INIT4(x)
#define MI_INIT16(x)  MI_INIT8(x),MI_INIT8(x)
#define MI_INIT32(x)  MI_INIT16(x),MI_INIT16(x)
#define MI_INIT64(x)  MI_INIT32(x),MI_INIT32(x)
#define MI_INIT128(x) MI_INIT64(x),MI_INIT64(x)
#define MI_INIT256(x) MI_INIT128(x),MI_INIT128(x)


#include <string.h>
// initialize a local variable to zero; use memset as compilers optimize constant sized memset's
#define _mi_memzero_var(x)  memset(&x,0,sizeof(x))

// Is `x` a power of two? (0 is considered a power of two)
static inline bool _mi_is_power_of_two(uintptr_t x) {
  return ((x & (x - 1)) == 0);
}

// Is a pointer aligned?
static inline bool _mi_is_aligned(void* p, size_t alignment) {
  mi_assert_internal(alignment != 0);
  return (((uintptr_t)p % alignment) == 0);
}

// Align upwards
static inline uintptr_t _mi_align_up(uintptr_t sz, size_t alignment) {
  mi_assert_internal(alignment != 0);
  uintptr_t mask = alignment - 1;
  if ((alignment & mask) == 0) {  // power of two?
    return ((sz + mask) & ~mask);
  }
  else {
    return (((sz + mask)/alignment)*alignment);
  }
}


// Align a pointer upwards
static inline uint8_t* _mi_align_up_ptr(void* p, size_t alignment) {
  return (uint8_t*)_mi_align_up((uintptr_t)p, alignment);
}


static inline uintptr_t _mi_align_down(uintptr_t sz, size_t alignment) {
  mi_assert_internal(alignment != 0);
  uintptr_t mask = alignment - 1;
  if ((alignment & mask) == 0) { // power of two?
    return (sz & ~mask);
  }
  else {
    return ((sz / alignment) * alignment);
  }
}

static inline void* mi_align_down_ptr(void* p, size_t alignment) {
  return (void*)_mi_align_down((uintptr_t)p, alignment);
}

// Divide upwards: `s <= _mi_divide_up(s,d)*d < s+d`.
static inline uintptr_t _mi_divide_up(uintptr_t size, size_t divider) {
  mi_assert_internal(divider != 0);
  return (divider == 0 ? size : ((size + divider - 1) / divider));
}


// clamp an integer
static inline size_t _mi_clamp(size_t sz, size_t min, size_t max) {
  if (sz < min) return min;
  else if (sz > max) return max;
  else return sz;
}

// Is memory zero initialized?
static inline bool mi_mem_is_zero(const void* p, size_t size) {
  for (size_t i = 0; i < size; i++) {
    if (((uint8_t*)p)[i] != 0) return false;
  }
  return true;
}

// Align a byte size to a size in _machine words_,
// i.e. byte size == `wsize*sizeof(void*)`.
static inline size_t _mi_wsize_from_size(size_t size) {
  mi_assert_internal(size <= SIZE_MAX - sizeof(uintptr_t));
  return (size + sizeof(uintptr_t) - 1) / sizeof(uintptr_t);
}

// Overflow detecting multiply
#if __has_builtin(__builtin_umul_overflow) || (defined(__GNUC__) && (__GNUC__ >= 5))
#include <limits.h>      // UINT_MAX, ULONG_MAX
#if defined(_CLOCK_T)    // for Illumos
#undef _CLOCK_T
#endif
static inline bool mi_mul_overflow(size_t count, size_t size, size_t* total) {
  #if (SIZE_MAX == ULONG_MAX)
    return __builtin_umull_overflow(count, size, (unsigned long *)total);
  #elif (SIZE_MAX == UINT_MAX)
    return __builtin_umul_overflow(count, size, (unsigned int *)total);
  #else
    return __builtin_umulll_overflow(count, size, (unsigned long long *)total);
  #endif
}
#else /* __builtin_umul_overflow is unavailable */
static inline bool mi_mul_overflow(size_t count, size_t size, size_t* total) {
  #define MI_MUL_COULD_OVERFLOW ((size_t)1 << (4*sizeof(size_t)))  // sqrt(SIZE_MAX)
  *total = count * size;
  // note: gcc/clang optimize this to directly check the overflow flag
  return ((size >= MI_MUL_COULD_OVERFLOW || count >= MI_MUL_COULD_OVERFLOW) && size > 0 && (SIZE_MAX / size) < count);
}
#endif

// Safe multiply `count*size` into `total`; return `true` on overflow.
static inline bool mi_count_size_overflow(size_t count, size_t size, size_t* total) {
  if (count==1) {  // quick check for the case where count is one (common for C++ allocators)
    *total = size;
    return false;
  }
  else if mi_unlikely(mi_mul_overflow(count, size, total)) {
    #if MI_DEBUG > 0
    _mi_error_message(EOVERFLOW, "allocation request is too large (%zu * %zu bytes)\n", count, size);
    #endif
    *total = SIZE_MAX;
    return true;
  }
  else return false;
}


/*----------------------------------------------------------------------------------------
  Heap functions
------------------------------------------------------------------------------------------- */

extern const mi_heap_t _mi_heap_empty;  // read-only empty heap, initial value of the thread local default heap

static inline bool mi_heap_is_backing(const mi_heap_t* heap) {
  return (heap->tld->heap_backing == heap);
}

static inline bool mi_heap_is_initialized(mi_heap_t* heap) {
  mi_assert_internal(heap != NULL);
  return (heap != &_mi_heap_empty);
}

static inline uintptr_t _mi_ptr_cookie(const void* p) {
  extern mi_heap_t _mi_heap_main;
  mi_assert_internal(_mi_heap_main.cookie != 0);
  return ((uintptr_t)p ^ _mi_heap_main.cookie);
}

static inline mi_tld_t* _mi_tld(void) {
  return mi_heap_get_default()->tld;
}

/* -----------------------------------------------------------
  Pages
----------------------------------------------------------- */

static inline mi_page_t* _mi_heap_get_free_small_page(mi_heap_t* heap, size_t size) {
  mi_assert_internal(size <= (MI_SMALL_SIZE_MAX + MI_PADDING_SIZE));
  const size_t idx = _mi_wsize_from_size(size);
  mi_assert_internal(idx < MI_PAGES_DIRECT);
  return heap->pages_free_direct[idx];
}


extern uint8_t* _mi_page_map;

static inline mi_page_t* _mi_ptr_page_ex(const void* p, bool* valid) {
  #if 1
  const uintptr_t idx = ((uintptr_t)p) >> MI_ARENA_SLICE_SHIFT;
  const size_t ofs = _mi_page_map[idx];
  if (valid != NULL) *valid = (ofs != 0);
  return (mi_page_t*)((idx - ofs + 1) << MI_ARENA_SLICE_SHIFT);
  #else
  const uintptr_t idx = ((uintptr_t)p) >> MI_ARENA_SLICE_SHIFT;
  const uintptr_t up   = idx << MI_ARENA_SLICE_SHIFT;
  __builtin_prefetch((void*)up);
  const size_t ofs = _mi_page_map[idx];
  if (valid != NULL) *valid = (ofs != 0);
  return (mi_page_t*)(up - ((ofs - 1) << MI_ARENA_SLICE_SHIFT));
  #endif
}

static inline mi_page_t* _mi_checked_ptr_page(const void* p) {
  bool valid;
  mi_page_t* const page = _mi_ptr_page_ex(p,&valid);
  return (valid ? page : NULL);
}

static inline mi_page_t* _mi_ptr_page(const void* p) {
  #if MI_DEBUG
  return _mi_checked_ptr_page(p);
  #else
  return _mi_ptr_page_ex(p,NULL);
  #endif
}


// Get the block size of a page
static inline size_t mi_page_block_size(const mi_page_t* page) {
  mi_assert_internal(page->block_size > 0);
  return page->block_size;
}

// Page start
static inline uint8_t* mi_page_start(const mi_page_t* page) {
  return page->page_start;
}

static inline uint8_t* mi_page_area(const mi_page_t* page, size_t* size) {
  if (size) { *size = mi_page_block_size(page) * page->reserved; }
  return mi_page_start(page);
}

static inline bool mi_page_contains_address(const mi_page_t* page, const void* p) {
  size_t psize;
  uint8_t* start = mi_page_area(page, &psize);
  return (start <= (uint8_t*)p && (uint8_t*)p < start + psize);
}

static inline bool mi_page_is_in_arena(const mi_page_t* page) {
  return (page->memid.memkind == MI_MEM_ARENA);
}

static inline bool mi_page_is_singleton(const mi_page_t* page) {
  return (page->reserved == 1);
}

// Get the usable block size of a page without fixed padding.
// This may still include internal padding due to alignment and rounding up size classes.
static inline size_t mi_page_usable_block_size(const mi_page_t* page) {
  return mi_page_block_size(page) - MI_PADDING_SIZE;
}

static inline mi_heap_t* mi_page_heap(const mi_page_t* page) {
  return page->heap;
}

static inline void mi_page_set_heap(mi_page_t* page, mi_heap_t* heap) {
  if (heap != NULL) {
    // mi_atomic_store_release(&page->xheap, (uintptr_t)heap);
    page->heap = heap;
    page->heap_tag = heap->tag;
    mi_atomic_store_release(&page->xthread_id, heap->thread_id);
  }
  else {
    // mi_atomic_store_release(&page->xheap, (uintptr_t)heap->tld->subproc);
    page->heap = NULL;
    mi_atomic_store_release(&page->xthread_id,0);
  }
}

//static inline void mi_page_set_heap(mi_page_t* page, mi_heap_t* heap) {
//  mi_assert_internal(mi_page_thread_free_flag(page) != MI_DELAYED_FREEING);
//  if (heap != NULL) {
//    mi_atomic_store_release(&page->xheap, (uintptr_t)heap);
//    page->heap_tag = heap->tag;
//    mi_atomic_store_release(&page->xthread_id, heap->thread_id);
//  }
//  else {
//    mi_atomic_store_release(&page->xheap, (uintptr_t)mi_page_heap(page)->tld->subproc);
//    mi_atomic_store_release(&page->xthread_id,0);
//  }
//}

// Thread free flag helpers
static inline mi_block_t* mi_tf_block(mi_thread_free_t tf) {
  return (mi_block_t*)(tf & ~1);
}
static inline bool mi_tf_is_owned(mi_thread_free_t tf) {
  return ((tf & 1) == 1);
}
static inline mi_thread_free_t mi_tf_create(mi_block_t* block, bool owned) {
  return (mi_thread_free_t)((uintptr_t)block | (owned ? 1 : 0));
}


// Thread id of thread that owns this page
static inline mi_threadid_t mi_page_thread_id(const mi_page_t* page) {
  return mi_atomic_load_relaxed(&page->xthread_id);
}

// Thread free access
static inline mi_block_t* mi_page_thread_free(const mi_page_t* page) {
  return mi_tf_block(mi_atomic_load_relaxed(&((mi_page_t*)page)->xthread_free));
}

// Owned?
static inline bool mi_page_is_owned(const mi_page_t* page) {
  return mi_tf_is_owned(mi_atomic_load_relaxed(&((mi_page_t*)page)->xthread_free));
}


//static inline mi_thread_free_t mi_tf_set_delayed(mi_thread_free_t tf, mi_delayed_t delayed) {
//  return mi_tf_make(mi_tf_block(tf),delayed);
//}
//static inline mi_thread_free_t mi_tf_set_block(mi_thread_free_t tf, mi_block_t* block) {
//  return mi_tf_make(block, mi_tf_delayed(tf));
//}

// are all blocks in a page freed?
// note: needs up-to-date used count, (as the `xthread_free` list may not be empty). see `_mi_page_collect_free`.
static inline bool mi_page_all_free(const mi_page_t* page) {
  mi_assert_internal(page != NULL);
  return (page->used == 0);
}

// are there any available blocks?
static inline bool mi_page_has_any_available(const mi_page_t* page) {
  mi_assert_internal(page != NULL && page->reserved > 0);
  return (page->used < page->reserved || (mi_page_thread_free(page) != NULL));
}

// are there immediately available blocks, i.e. blocks available on the free list.
static inline bool mi_page_immediate_available(const mi_page_t* page) {
  mi_assert_internal(page != NULL);
  return (page->free != NULL);
}


// is the page not yet used up to its reserved space?
static inline bool mi_page_is_expandable(const mi_page_t* page) {
  mi_assert_internal(page != NULL);
  mi_assert_internal(page->capacity <= page->reserved);
  return (page->capacity < page->reserved);
}


static inline bool mi_page_is_full(mi_page_t* page) {
  bool full = (page->reserved == page->used);
  mi_assert_internal(!full || page->free == NULL);
  return full;
}

// is more than 7/8th of a page in use?
static inline bool mi_page_is_mostly_used(const mi_page_t* page) {
  if (page==NULL) return true;
  uint16_t frac = page->reserved / 8U;
  return (page->reserved - page->used <= frac);
}

// is more than (n-1)/n'th of a page in use?
static inline bool mi_page_is_used_at_frac(const mi_page_t* page, uint16_t n) {
  if (page==NULL) return true;
  uint16_t frac = page->reserved / n;
  return (page->reserved - page->used <= frac);
}

static inline bool mi_page_is_abandoned(const mi_page_t* page) {
  // note: the xheap field of an abandoned heap is set to the subproc (for fast reclaim-on-free)
  return (mi_atomic_load_acquire(&page->xthread_id) <= 1);
}

static inline bool mi_page_is_abandoned_mapped(const mi_page_t* page) {
  return (mi_atomic_load_acquire(&page->xthread_id) == 1);
}

static inline void mi_page_set_abandoned_mapped(mi_page_t* page) {
  mi_atomic_or_acq_rel(&page->xthread_id, (uintptr_t)1);
}

static inline void mi_page_clear_abandoned_mapped(mi_page_t* page) {
  mi_atomic_and_acq_rel(&page->xthread_id, ~(uintptr_t)1);
}


static inline bool mi_page_is_huge(const mi_page_t* page) {
  return (page->block_size > MI_LARGE_MAX_OBJ_SIZE || (mi_memkind_is_os(page->memid.memkind) && page->memid.mem.os.alignment > MI_PAGE_MAX_OVERALLOC_ALIGN));
}


static inline mi_page_queue_t* mi_page_queue(const mi_heap_t* heap, size_t size) {
  return &((mi_heap_t*)heap)->pages[_mi_bin(size)];
}


// Unown a page that is currently owned
static inline void _mi_page_unown_unconditional(mi_page_t* page) {
  mi_assert_internal(mi_page_is_owned(page));
  mi_assert_internal(mi_page_thread_id(page)==0);
  const uintptr_t old = mi_atomic_and_acq_rel(&page->xthread_free, ~((uintptr_t)1));
  mi_assert_internal((old&1)==1); MI_UNUSED(old);
  /*
  mi_thread_free_t tf_new;
  mi_thread_free_t tf_old;
  do {
    tf_old = mi_atomic_load_relaxed(&page->xthread_free);
    mi_assert_internal(mi_tf_is_owned(tf_old));
    tf_new = mi_tf_create(mi_tf_block(tf_old), false);
  } while (!mi_atomic_cas_weak_release(&page->xthread_free, &tf_old, tf_new));
  */
}


// get ownership if it is not yet owned
static inline bool mi_page_try_claim_ownership(mi_page_t* page) {
  const uintptr_t old = mi_atomic_or_acq_rel(&page->xthread_free, 1);
  return ((old&1)==0);
}

// release ownership of a page. This may free the page if all blocks were concurrently
// freed in the meantime. Returns true if the page was freed.
static inline bool _mi_page_unown(mi_page_t* page) {
  mi_assert_internal(mi_page_is_owned(page));
  mi_assert_internal(mi_page_is_abandoned(page));
  mi_thread_free_t tf_new;
  mi_thread_free_t tf_old = mi_atomic_load_relaxed(&page->xthread_free);
  do {
    mi_assert_internal(mi_tf_is_owned(tf_old));
    while mi_unlikely(mi_tf_block(tf_old) != NULL) {
      _mi_page_free_collect(page, false);  // update used
      if (mi_page_all_free(page)) {        // it may become free just before unowning it
        _mi_arena_page_unabandon(page);
        _mi_arena_page_free(page);
        return true;
      }
      tf_old = mi_atomic_load_relaxed(&page->xthread_free);
    }
    mi_assert_internal(mi_tf_block(tf_old)==NULL);
    tf_new = mi_tf_create(NULL, false);
  } while (!mi_atomic_cas_weak_release(&page->xthread_free, &tf_old, tf_new));
  return false;
}

//-----------------------------------------------------------
// Page flags
//-----------------------------------------------------------
static inline bool mi_page_is_in_full(const mi_page_t* page) {
  return page->flags.x.in_full;
}

static inline void mi_page_set_in_full(mi_page_t* page, bool in_full) {
  page->flags.x.in_full = in_full;
}

static inline bool mi_page_has_aligned(const mi_page_t* page) {
  return page->flags.x.has_aligned;
}

static inline void mi_page_set_has_aligned(mi_page_t* page, bool has_aligned) {
  page->flags.x.has_aligned = has_aligned;
}

/* -------------------------------------------------------------------
  Guarded objects
------------------------------------------------------------------- */
#if MI_GUARDED
static inline bool mi_block_ptr_is_guarded(const mi_block_t* block, const void* p) {
  const ptrdiff_t offset = (uint8_t*)p - (uint8_t*)block;
  return (offset >= (ptrdiff_t)(sizeof(mi_block_t)) && block->next == MI_BLOCK_TAG_GUARDED);
}

static inline bool mi_heap_malloc_use_guarded(mi_heap_t* heap, size_t size) {
  // this code is written to result in fast assembly as it is on the hot path for allocation
  const size_t count = heap->guarded_sample_count - 1;  // if the rate was 0, this will underflow and count for a long time..
  if mi_likely(count != 0) {
    // no sample
    heap->guarded_sample_count = count;
    return false;
  }
  else if (size >= heap->guarded_size_min && size <= heap->guarded_size_max) {
    // use guarded allocation
    heap->guarded_sample_count = heap->guarded_sample_rate;  // reset
    return (heap->guarded_sample_rate != 0);
  }
  else {
    // failed size criteria, rewind count (but don't write to an empty heap)
    if (heap->guarded_sample_rate != 0) { heap->guarded_sample_count = 1; }
    return false;
  }
}

mi_decl_restrict void* _mi_heap_malloc_guarded(mi_heap_t* heap, size_t size, bool zero) mi_attr_noexcept;

#endif


/* -------------------------------------------------------------------
Encoding/Decoding the free list next pointers

This is to protect against buffer overflow exploits where the
free list is mutated. Many hardened allocators xor the next pointer `p`
with a secret key `k1`, as `p^k1`. This prevents overwriting with known
values but might be still too weak: if the attacker can guess
the pointer `p` this  can reveal `k1` (since `p^k1^p == k1`).
Moreover, if multiple blocks can be read as well, the attacker can
xor both as `(p1^k1) ^ (p2^k1) == p1^p2` which may reveal a lot
about the pointers (and subsequently `k1`).

Instead mimalloc uses an extra key `k2` and encodes as `((p^k2)<<<k1)+k1`.
Since these operations are not associative, the above approaches do not
work so well any more even if the `p` can be guesstimated. For example,
for the read case we can subtract two entries to discard the `+k1` term,
but that leads to `((p1^k2)<<<k1) - ((p2^k2)<<<k1)` at best.
We include the left-rotation since xor and addition are otherwise linear
in the lowest bit. Finally, both keys are unique per page which reduces
the re-use of keys by a large factor.

We also pass a separate `null` value to be used as `NULL` or otherwise
`(k2<<<k1)+k1` would appear (too) often as a sentinel value.
------------------------------------------------------------------- */

static inline bool mi_is_in_same_page(const void* p, const void* q) {
  mi_page_t* page = _mi_ptr_page(p);
  return mi_page_contains_address(page,q);
  // return (_mi_ptr_page(p) == _mi_ptr_page(q));
}

static inline void* mi_ptr_decode(const void* null, const mi_encoded_t x, const uintptr_t* keys) {
  void* p = (void*)(mi_rotr(x - keys[0], keys[0]) ^ keys[1]);
  return (p==null ? NULL : p);
}

static inline mi_encoded_t mi_ptr_encode(const void* null, const void* p, const uintptr_t* keys) {
  uintptr_t x = (uintptr_t)(p==NULL ? null : p);
  return mi_rotl(x ^ keys[1], keys[0]) + keys[0];
}

static inline uint32_t mi_ptr_encode_canary(const void* null, const void* p, const uintptr_t* keys) {
  const uint32_t x = (uint32_t)(mi_ptr_encode(null,p,keys));
  // make the lowest byte 0 to prevent spurious read overflows which could be a security issue (issue #951)
  #if MI_BIG_ENDIAN
  return (x & 0x00FFFFFF);
  #else
  return (x & 0xFFFFFF00);
  #endif
}

static inline mi_block_t* mi_block_nextx( const void* null, const mi_block_t* block, const uintptr_t* keys ) {
  mi_track_mem_defined(block,sizeof(mi_block_t));
  mi_block_t* next;
  #ifdef MI_ENCODE_FREELIST
  next = (mi_block_t*)mi_ptr_decode(null, block->next, keys);
  #else
  MI_UNUSED(keys); MI_UNUSED(null);
  next = (mi_block_t*)block->next;
  #endif
  mi_track_mem_noaccess(block,sizeof(mi_block_t));
  return next;
}

static inline void mi_block_set_nextx(const void* null, mi_block_t* block, const mi_block_t* next, const uintptr_t* keys) {
  mi_track_mem_undefined(block,sizeof(mi_block_t));
  #ifdef MI_ENCODE_FREELIST
  block->next = mi_ptr_encode(null, next, keys);
  #else
  MI_UNUSED(keys); MI_UNUSED(null);
  block->next = (mi_encoded_t)next;
  #endif
  mi_track_mem_noaccess(block,sizeof(mi_block_t));
}

static inline mi_block_t* mi_block_next(const mi_page_t* page, const mi_block_t* block) {
  #ifdef MI_ENCODE_FREELIST
  mi_block_t* next = mi_block_nextx(page,block,page->keys);
  // check for free list corruption: is `next` at least in the same page?
  // TODO: check if `next` is `page->block_size` aligned?
  if mi_unlikely(next!=NULL && !mi_is_in_same_page(block, next)) {
    _mi_error_message(EFAULT, "corrupted free list entry of size %zub at %p: value 0x%zx\n", mi_page_block_size(page), block, (uintptr_t)next);
    next = NULL;
  }
  return next;
  #else
  MI_UNUSED(page);
  return mi_block_nextx(page,block,NULL);
  #endif
}

static inline void mi_block_set_next(const mi_page_t* page, mi_block_t* block, const mi_block_t* next) {
  #ifdef MI_ENCODE_FREELIST
  mi_block_set_nextx(page,block,next, page->keys);
  #else
  MI_UNUSED(page);
  mi_block_set_nextx(page,block,next,NULL);
  #endif
}

/* -----------------------------------------------------------
  arena blocks
----------------------------------------------------------- */

// Blocks needed for a given byte size
static inline size_t mi_slice_count_of_size(size_t size) {
  return _mi_divide_up(size, MI_ARENA_SLICE_SIZE);
}

// Byte size of a number of blocks
static inline size_t mi_size_of_slices(size_t bcount) {
  return (bcount * MI_ARENA_SLICE_SIZE);
}


/* -----------------------------------------------------------
  memory id's
----------------------------------------------------------- */

static inline mi_memid_t _mi_memid_create(mi_memkind_t memkind) {
  mi_memid_t memid;
  _mi_memzero_var(memid);
  memid.memkind = memkind;
  return memid;
}

static inline mi_memid_t _mi_memid_none(void) {
  return _mi_memid_create(MI_MEM_NONE);
}

static inline mi_memid_t _mi_memid_create_os(void* base, size_t size, bool committed, bool is_zero, bool is_large) {
  mi_memid_t memid = _mi_memid_create(MI_MEM_OS);
  memid.mem.os.base = base;
  memid.mem.os.size = size;
  memid.initially_committed = committed;
  memid.initially_zero = is_zero;
  memid.is_pinned = is_large;
  return memid;
}


// -------------------------------------------------------------------
// Fast "random" shuffle
// -------------------------------------------------------------------

static inline uintptr_t _mi_random_shuffle(uintptr_t x) {
  if (x==0) { x = 17; }   // ensure we don't get stuck in generating zeros
#if (MI_INTPTR_SIZE>=8)
  // by Sebastiano Vigna, see: <http://xoshiro.di.unimi.it/splitmix64.c>
  x ^= x >> 30;
  x *= 0xbf58476d1ce4e5b9UL;
  x ^= x >> 27;
  x *= 0x94d049bb133111ebUL;
  x ^= x >> 31;
#elif (MI_INTPTR_SIZE==4)
  // by Chris Wellons, see: <https://nullprogram.com/blog/2018/07/31/>
  x ^= x >> 16;
  x *= 0x7feb352dUL;
  x ^= x >> 15;
  x *= 0x846ca68bUL;
  x ^= x >> 16;
#endif
  return x;
}

// -------------------------------------------------------------------
// Optimize numa node access for the common case (= one node)
// -------------------------------------------------------------------

int    _mi_os_numa_node_get(mi_os_tld_t* tld);
size_t _mi_os_numa_node_count_get(void);

extern _Atomic(size_t) _mi_numa_node_count;
static inline int _mi_os_numa_node(mi_os_tld_t* tld) {
  if mi_likely(mi_atomic_load_relaxed(&_mi_numa_node_count) == 1) { return 0; }
  else return _mi_os_numa_node_get(tld);
}
static inline size_t _mi_os_numa_node_count(void) {
  const size_t count = mi_atomic_load_relaxed(&_mi_numa_node_count);
  if mi_likely(count > 0) { return count; }
  else return _mi_os_numa_node_count_get();
}


// ---------------------------------------------------------------------------------
// Provide our own `_mi_memcpy` for potential performance optimizations.
//
// For now, only on Windows with msvc/clang-cl we optimize to `rep movsb` if
// we happen to run on x86/x64 cpu's that have "fast short rep movsb" (FSRM) support
// (AMD Zen3+ (~2020) or Intel Ice Lake+ (~2017). See also issue #201 and pr #253.
// ---------------------------------------------------------------------------------

#if !MI_TRACK_ENABLED && defined(_WIN32) && (defined(_M_IX86) || defined(_M_X64))
#include <intrin.h>
extern bool _mi_cpu_has_fsrm;
extern bool _mi_cpu_has_erms;
static inline void _mi_memcpy(void* dst, const void* src, size_t n) {
  if ((_mi_cpu_has_fsrm && n <= 128) || (_mi_cpu_has_erms && n > 128)) {
    __movsb((unsigned char*)dst, (const unsigned char*)src, n);
  }
  else {
    memcpy(dst, src, n);
  }
}
static inline void _mi_memset(void* dst, int val, size_t n) {
  if ((_mi_cpu_has_fsrm && n <= 128) || (_mi_cpu_has_erms && n > 128)) {
    __stosb((unsigned char*)dst, (uint8_t)val, n);
  }
  else {
    memset(dst, val, n);
  }
}
#else
static inline void _mi_memcpy(void* dst, const void* src, size_t n) {
  memcpy(dst, src, n);
}
static inline void _mi_memset(void* dst, int val, size_t n) {
  memset(dst, val, n);
}
#endif

// -------------------------------------------------------------------------------
// The `_mi_memcpy_aligned` can be used if the pointers are machine-word aligned
// This is used for example in `mi_realloc`.
// -------------------------------------------------------------------------------

#if (defined(__GNUC__) && (__GNUC__ >= 4)) || defined(__clang__)
// On GCC/CLang we provide a hint that the pointers are word aligned.
static inline void _mi_memcpy_aligned(void* dst, const void* src, size_t n) {
  mi_assert_internal(((uintptr_t)dst % MI_INTPTR_SIZE == 0) && ((uintptr_t)src % MI_INTPTR_SIZE == 0));
  void* adst = __builtin_assume_aligned(dst, MI_INTPTR_SIZE);
  const void* asrc = __builtin_assume_aligned(src, MI_INTPTR_SIZE);
  _mi_memcpy(adst, asrc, n);
}

static inline void _mi_memset_aligned(void* dst, int val, size_t n) {
  mi_assert_internal((uintptr_t)dst % MI_INTPTR_SIZE == 0);
  void* adst = __builtin_assume_aligned(dst, MI_INTPTR_SIZE);
  _mi_memset(adst, val, n);
}
#else
// Default fallback on `_mi_memcpy`
static inline void _mi_memcpy_aligned(void* dst, const void* src, size_t n) {
  mi_assert_internal(((uintptr_t)dst % MI_INTPTR_SIZE == 0) && ((uintptr_t)src % MI_INTPTR_SIZE == 0));
  _mi_memcpy(dst, src, n);
}

static inline void _mi_memset_aligned(void* dst, int val, size_t n) {
  mi_assert_internal((uintptr_t)dst % MI_INTPTR_SIZE == 0);
  _mi_memset(dst, val, n);
}
#endif

static inline void _mi_memzero(void* dst, size_t n) {
  _mi_memset(dst, 0, n);
}

static inline void _mi_memzero_aligned(void* dst, size_t n) {
  _mi_memset_aligned(dst, 0, n);
}


#endif