add stb_ds.h and tests

stb_ds.h

@@ -0,0 +1,1626 @@
+/* stb_ds.h - v0.2 - public domain data structures - Sean Barrett 2019
+  
+   This is a single-header-file library that provides easy-to-use
+   dynamic arrays and hash tables for C (also works in C++).
+
+   For a gentle introduction:
+      http://nothings.org/stb_ds
+
+   To use this library, do this in *one* C or C++ file:
+      #define STB_DS_IMPLEMENTATION
+      #include "stb_ds.h"
+
+TABLE OF CONTENTS
+
+  Table of Contents
+  Compile-time options
+  License
+  Documentation
+  Notes
+  Notes - Dynamic arrays
+  Notes - Hash maps
+  Credits
+
+COMPILE-TIME OPTIONS
+
+  #define STBDS_NO_SHORT_NAMES
+
+     This flag needs to be set globally.
+       
+     By default stb_ds exposes shorter function names that are not qualified
+     with the "stbds_" prefix. If these names conflict with the names in your
+     code, define this flag.
+
+  #define STBDS_SIPHASH_2_4
+
+     This flag only needs to be set in the file containing #define STB_DS_IMPLEMENTATION.
+
+     By default stb_ds.h hashes using a weaker variant of SipHash and a custom hash for
+     4- and 8-byte keys. On 64-bit platforms, you can define the above flag to force
+     stb_ds.h to use specification-compliant SipHash-2-4 for all keys. Doing so makes
+     hash table insertion about 20% slower on 4- and 8-byte keys, 5% slower on
+     64-byte keys, and 10% slower on 256-byte keys on my test computer.
+
+LICENSE
+
+  Placed in the public domain and also MIT licensed.
+  See end of file for detailed license information.
+
+DOCUMENTATION
+
+  Dynamic Arrays
+
+    Non-function interface:
+
+      Declare an empty dynamic array of type T
+        T* foo = NULL;    
+
+      Access the i'th item of a dynamic array 'foo' of type T, T* foo:
+        foo[i]
+
+    Functions (actually macros)
+
+      arrfree:
+        void arrfree(T*);
+          Frees the array.
+
+      arrlen:
+        ptrdiff_t arrlen(T*);
+          Returns the number of elements in the array.
+
+      arrlenu:
+        size_t arrlenu(T*);
+          Returns the number of elements in the array as an unsigned type.
+
+      arrput:
+        T arrput(T* a, T b);
+          Appends the item b to the end of array a. Returns b.
+
+      arrins:
+        T arrins(T* a, int p, T b);
+          Inserts the item b into the middle of array a, into a[p],
+          moving the rest of the array over. Returns b.
+
+      arrinsn:
+        void arrins(T* a, int p, int n);
+          Inserts n uninitialized items into array a starting at a[p],
+          moving the rest of the array over.
+
+      arrdel:
+        void arrdel(T* a, int p);
+          Deletes the element at a[p], moving the rest of the array over.
+
+      arrdeln:
+        void arrdel(T* a, int p, int n);
+          Deletes n elements starting at a[p], moving the rest of the array over.
+
+      arrdelswap:
+        void arrdelswap(T* a, int p);
+          Deletes the element at a[p], replacing it with the element from
+          the end of the array. O(1) performance.
+
+      arrsetlen:
+        void arrsetlen(T* a, int n);
+          Changes the length of the array to n. Allocates uninitialized
+          slots at the end if necessary.
+
+      arrsetcap:
+        size_t arrsetcap(T* a, int n);
+          Sets the length of allocated storage to at least n. It will not
+          change the length of the array.
+
+      arrcap:
+        size_t arrcap(T* a);
+          Returns the number of total elements the array can contain without
+          needing to be reallocated.
+
+  Hash maps & String hash maps
+
+    Given T is a structure type: struct { TK key; TV value; }. Note that some
+    functions do not require TV value and can have other fields. For string
+    hash maps, TK must be 'char *'.
+
+    Special interface:
+
+      stbds_rand_seed:
+        void stbds_rand_seed(size_t seed);
+          For security against adversarially chosen data, you should seed the
+          library with a strong random number. Or at least seed it with time().
+
+      stbds_hash_string:
+        size_t stbds_hash_string(char *str, size_t seed);
+          Returns a hash value for a string.
+
+      stbds_hash_bytes:
+        size_t stbds_hash_bytes(void *p, size_t len, size_t seed);
+          These functions hash an arbitrary number of bytes. The function
+          uses a custom hash for 4- and 8-byte data, and a weakened version
+          of SipHash for everything else. On 64-bit platforms you can get
+          specification-compliant SipHash-2-4 on all data by defining
+          STBDS_SIPHASH_2_4, at a significant cost in speed.
+
+    Non-function interface:
+
+      Declare an empty hash map of type T
+        T* foo = NULL;
+
+      Access the i'th entry in a hash table T* foo:
+        foo[i]
+
+    Function interface (actually macros):
+
+      hmfree
+      shfree
+        void hmfree(T*);
+        void shfree(T*);
+          Frees the hashmap and sets the pointer to NULL.
+
+      hmlen
+      shlen
+        ptrdiff_t hmlen(T*)
+        ptrdiff_t shlen(T*)
+          Returns the number of elements in the hashmap.
+
+      hmlenu
+      shlenu
+        size_t hmlenu(T*)
+        size_t shlenu(T*)
+          Returns the number of elements in the hashmap.
+
+      hmgeti
+      shgeti
+        ptrdiff_t hmgeti(T*, TK key)
+        ptrdiff_t shgeti(T*, char* key)
+          Returns the index in the hashmap which has the key 'key', or -1
+          if the key is not present.
+
+      hmget
+      shget
+        TV hmget(T*, TK key)
+        TV shget(T*, char* key)
+          Returns the value corresponding to 'key' in the hashmap.
+          The structure must have a 'value' field
+
+      hmgets
+      shgets
+        T hmgets(T*, TK key)
+        T shgets(T*, char* key)
+          Returns the structure corresponding to 'key' in the hashmap.
+
+      hmdefault
+      shdefault
+        TV hmdefault(T*, TV value)
+        TV shdefault(T*, TV value)
+          Sets the default value for the hashmap, the value which will be
+          returned by hmget/shget if the key is not present.
+
+      hmdefaults
+      shdefaults
+        TV hmdefaults(T*, T item)
+        TV shdefaults(T*, T item)
+          Sets the default struct for the hashmap, the contents which will be
+          returned by hmgets/shgets if the key is not present.
+
+      hmput
+      shput
+        TV hmput(T*, TK key, TV value)
+        TV shput(T*, char* key, TV value)
+          Inserts a <key,value> pair into the hashmap. If the key is already
+          present in the hashmap, updates its value.
+
+      hmputs
+      shputs
+        T hmputs(T*, T item)
+        T shputs(T*, T item)
+          Returns the structure corresponding to 'key' in the hashmap.
+
+      hmdel
+      shdel
+        int hmdel(T*, TK key)
+        int shdel(T*, char* key)
+          If 'key' is in the hashmap, deletes its entry and returns 1.
+          Otherwise returns 0.
+
+    Function interface (actually macros) for strings only:
+
+      sh_new_strdup
+        void sh_new_strdup(T*);
+          Overwrites the existing pointer with a newly allocated
+          string hashmap which will automatically allocate and free
+          each string key using malloc/free
+
+      sh_new_arena
+        void sh_new_arena(T*);
+          Overwrites the existing pointer with a newly allocated
+          string hashmap which will automatically allocate each string
+          key to a string arena. Every string key ever used by this
+          hash table remains in the arena until the arena is freed.
+          Additionally, any key which is deleted and reinserted will
+          be allocated multiple times in the string arena.
+
+NOTES
+
+  * These data structures are realloc'd when they grow, and the macro "functions"
+    write to the provided pointer. This means: (a) the pointer must be an lvalue,
+    and (b) the pointer to the data structure is not stable, and you must maintain
+    it the same as you would a realloc'd pointer. For example, if you pass a pointer
+    to a dynamic array to a function which updates it, the function must return
+    back the new pointer to the caller. This is the price of trying to do this in C.
+
+  * You iterate over the contents of a dynamic array and a hashmap in exactly
+    the same way, using arrlen/hmlen/shlen:
+
+      for (i=0; i < arrlen(foo); ++i)
+         ... foo[i] ...
+
+  * All operations except arrins/arrdel are O(1) amortized, but individual
+    operations can be slow, so these data structures may not be suitable
+    for real time use. Dynamic arrays double in capacity as needed, so
+    elements are copied an average of once. Hash tables double/halve
+    their size as needed, with appropriate hysteresis to maintain O(1)
+    performance.
+
+NOTES - DYNAMIC ARRAY
+
+  * If you know how long a dynamic array is going to be in advance, you can avoid
+    extra memory allocations by using arrsetlen to allocate it to that length in
+    advance and use foo[n] while filling it out, or arrsetcap to allocate the memory
+    for that length and use arrput/arrpush as normal.
+
+  * Unlike some other versions of the dynamic array, this version should
+    be safe to use with strict-aliasing optimizations.
+
+NOTES - HASH MAP
+
+  * For compilers other than GCC and clang (e.g. Visual Studio), for hmput/hmget/hmdel
+    and variants, the key must be an lvalue (so the macro can take the address of it).
+    For GCC and clang, extensions are used that eliminate this requirement if you're
+    using C99 and later or using C++.
+
+  * To test for presence of a key in a hashmap, just do 'hmget(foo,key) >= 0'.
+
+  * The iteration order of your data in the hashmap is determined solely by the
+    order of insertions and deletions. In particular, if you never delete, new
+    keys are always added at the end of the array. This will be consistent
+    across all platforms and versions of the library. However, you should not
+    attempt to serialize the internal hash table, as the hash is not consistent
+    between different platforms, and may change with future versions of the library.
+
+  * Use sh_new_arena() for string hashmaps that you never delete from. Initialize
+    with NULL if you're managing the memory for your strings, or your strings are
+    never freed (at least until the hashmap is freed). Otherwise, use sh_new_strdup().
+    @TODO: make an arena variant that garbage collects the strings with a trivial
+    copy collector into a new arena whenever the table shrinks / rebuilds. Since
+    current arena recommendation is to only use arena if it never deletes, then
+    this can just replace current arena implementation.
+
+  * If adversarial input is a serious concern and you're on a 64-bit platform,
+    enable STBDS_SIPHASH_2_4 (see the 'Compile-time options' section), and pass
+    a strong random number to stbds_rand_seed.
+     
+  * The default value for the hash table is stored in foo[-1], so if you
+    use code like 'hmget(T,k)->value = 5' you can overwrite the value
+    stored by hmdefault if 'k' is not present.
+
+CREDITS
+
+  Sean Barrett -- library, idea for dynamic array API/implementation
+  Per Vognsen  -- idea for hash table API/implementation
+*/
+
+#ifndef INCLUDE_STB_DS_H
+#define INCLUDE_STB_DS_H
+
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+
+#ifndef STBDS_NO_SHORT_NAMES
+#define arrlen      stbds_arrlen
+#define arrlenu     stbds_arrlenu
+#define arrput      stbds_arrput
+#define arrpush     stbds_arrput
+#define arrfree     stbds_arrfree
+#define arraddn     stbds_arraddn
+#define arrsetlen   stbds_arrsetlen
+#define arrlast     stbds_arrlast
+#define arrins      stbds_arrins
+#define arrinsn     stbds_arrinsn
+#define arrdel      stbds_arrdel
+#define arrdeln     stbds_arrdeln
+#define arrdelswap  stbds_arrdelswap
+#define arrcap      stbds_arrcap
+#define arrsetcap   stbds_arrsetcap
+
+#define hmput       stbds_hmput
+#define hmputs      stbds_hmputs
+#define hmget       stbds_hmget
+#define hmgets      stbds_hmgets
+#define hmgetp      stbds_hmgetp
+#define hmgeti      stbds_hmgeti
+#define hmdel       stbds_hmdel
+#define hmlen       stbds_hmlen
+#define hmlenu      stbds_hmlenu
+#define hmfree      stbds_hmfree
+#define hmdefault   stbds_hmdefault
+#define hmdefaults  stbds_hmdefaults
+
+#define shput       stbds_shput
+#define shputs      stbds_shputs
+#define shget       stbds_shget
+#define shgets      stbds_shgets
+#define shgetp      stbds_shgetp
+#define shgeti      stbds_shgeti
+#define shdel       stbds_shdel
+#define shlen       stbds_shlen
+#define shlenu      stbds_shlenu
+#define shfree      stbds_shfree
+#define shdefault   stbds_shdefault
+#define shdefaults  stbds_shdefaults
+#define sh_new_arena  stbds_sh_new_arena
+#define sh_new_strdup stbds_sh_new_strdup
+
+#define stralloc    stbds_stralloc
+#define strreset    stbds_strreset
+#endif      
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// for security against attackers, seed the library with a random number, at least time() but stronger is better
+extern void stbds_rand_seed(size_t seed);
+
+// these are the hash functions used internally if you want to test them or use them for other purposes
+extern size_t stbds_hash_bytes(void *p, size_t len, size_t seed);
+extern size_t stbds_hash_string(char *str, size_t seed);
+
+// this is a simple string arena allocator, initialize with e.g. 'stbds_string_arena my_arena={0}'.
+typedef struct stbds_string_arena stbds_string_arena;
+extern char * stbds_stralloc(stbds_string_arena *a, char *str);
+extern void   stbds_strreset(stbds_string_arena *a);
+
+// have to #define STBDS_UNIT_TESTS to call this
+extern void stbds_unit_tests(void);
+
+///////////////
+//
+// Everything below here is implementation details
+//
+
+extern void * stbds_arrgrowf(void *a, size_t elemsize, size_t addlen, size_t min_cap);
+extern void   stbds_hmfree_func(void *p, size_t elemsize, size_t keyoff);
+extern void * stbds_hmget_key(void *a, size_t elemsize, void *key, size_t keysize, int mode);
+extern void * stbds_hmput_default(void *a, size_t elemsize);
+extern void * stbds_hmput_key(void *a, size_t elemsize, void *key, size_t keysize, int mode);
+extern void * stbds_hmdel_key(void *a, size_t elemsize, void *key, size_t keysize, size_t keyoffset, int mode);
+extern void * stbds_shmode_func(size_t elemsize, int mode);
+
+#ifdef __cplusplus
+}
+#endif
+
+#if defined(__GNUC__) || defined(__clang__)
+#define STBDS_HAS_TYPEOF
+#ifdef __cplusplus
+#define STBDS_HAS_LITERAL_ARRAY
+#endif
+#endif
+
+#if !defined(__cplusplus)
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+#define STBDS_HAS_LITERAL_ARRAY
+#endif
+#endif
+
+// this macro takes the address of the argument, but on gcc/clang can accept rvalues
+#if defined(STBDS_HAS_LITERAL_ARRAY) && defined(STBDS_HAS_TYPEOF)
+#define STBDS_ADDRESSOF(typevar, value)     ((typeof(typevar)[1]){value}) // literal array decays to pointer to value
+#else
+#define STBDS_ADDRESSOF(typevar, value)     &(value)
+#endif
+
+#define STBDS_OFFSETOF(var,field)           ((char *) &(var)->field - (char *) (var))
+
+#define stbds_header(t)  ((stbds_array_header *) (t) - 1)
+#define stbds_temp(t)    stbds_header(t)->temp
+
+#define stbds_arrsetcap(a,n) (stbds_arrgrow(a,0,n))
+#define stbds_arrsetlen(a,n) ((stbds_arrcap(a) < n ? stbds_arrsetcap(a,n),0 : 0), (a) ? stbds_header(a)->length = (n) : 0)
+#define stbds_arrcap(a)       ((a) ? stbds_header(a)->capacity : 0)
+#define stbds_arrlen(a)       ((a) ? (ptrdiff_t) stbds_header(a)->length : 0)
+#define stbds_arrlenu(a)      ((a) ?             stbds_header(a)->length : 0)
+#define stbds_arrput(a,v)     (stbds_arrmaybegrow(a,1), (a)[stbds_header(a)->length++] = (v))
+#define stbds_arrpush         stbds_arrput  // synonym
+#define stbds_arraddn(a,n)    (stbds_arrmaybegrow(a,n), stbds_header(a)->length += (n))
+#define stbds_arrlast(a)      ((a)[stbds_header(a)->length-1])
+#define stbds_arrfree(a)      ((void) ((a) ? realloc(stbds_header(a),0) : 0), (a)=NULL)
+#define stbds_arrdel(a,i)     stbds_arrdeln(a,i,1)
+#define stbds_arrdeln(a,i,n)  (memmove(&(a)[i], &(a)[(i)+(n)], sizeof *(a) * (stbds_header(a)->length-(n)-(i))), stbds_header(a)->length -= (n))
+#define stbds_arrdelswap(a,i) ((a)[i] = stbds_arrlast(a), stbds_header(a)->length -= 1)
+#define stbds_arrinsn(a,i,n)  (stbds_arraddn((a),(n)), memmove(&(a)[(i)+(n)], &(a)[i], sizeof *(a) * (stbds_header(a)->length-(n)-(i))))
+#define stbds_arrins(a,i,v)   (stbds_arrinsn((a),(i),1), (a)[i]=(v))
+
+#define stbds_arrmaybegrow(a,n)  ((!(a) || stbds_header(a)->length + (n) > stbds_header(a)->capacity) \
+                                  ? (stbds_arrgrow(a,n,0),0) : 0)
+
+#define stbds_arrgrow(a,b,c)   ((a) = stbds_arrgrowf((a), sizeof *(a), (b), (c)))
+
+#define stbds_hmput(t, k, v) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), STBDS_ADDRESSOF((t)->key, (k)), sizeof (t)->key, 0),   \
+     (t)[stbds_temp((t)-1)].key = (k), \
+     (t)[stbds_temp((t)-1)].value = (v))
+
+#define stbds_hmputs(t, s) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), &(s).key, sizeof (s).key, STBDS_HM_BINARY), \
+     (t)[stbds_temp((t)-1)] = (s))
+
+#define stbds_hmgeti(t,k) \
+    ((t) = stbds_hmget_key_wrapper((t), sizeof *(t), STBDS_ADDRESSOF((t)->key, (k)), sizeof (t)->key, STBDS_HM_BINARY), \
+      stbds_temp((t)-1))
+
+#define stbds_hmgetp(t, k) \
+    ((void) stbds_hmgeti(t,k), &(t)[stbds_temp((t)-1)])
+
+#define stbds_hmdel(t,k) \
+    (((t) = stbds_hmdel_key_wrapper((t),sizeof *(t), STBDS_ADDRESSOF((t)->key, (k)), sizeof (t)->key, STBDS_OFFSETOF((t),key), STBDS_HM_BINARY)),(t)?stbds_temp((t)-1):0)
+
+#define stbds_hmdefault(t, v) \
+    ((t) = stbds_hmput_default_wrapper((t), sizeof *(t)), (t)[-1].value = (v))
+
+#define stbds_hmdefaults(t, s) \
+    ((t) = stbds_hmput_default_wrapper((t), sizeof *(t)), (t)[-1] = (s))
+
+#define stbds_hmfree(p)        \
+    ((void) ((p) != NULL ? stbds_hmfree_func((p)-1,sizeof*(p),STBDS_OFFSETOF((p),key)),0 : 0),(p)=NULL)
+
+#define stbds_hmgets(t, k) (*stbds_hmgetp(t,k))
+#define stbds_hmget(t, k)  (stbds_hmgetp(t,k)->value)
+#define stbds_hmlen(t)     (stbds_arrlen((t)-1)-1)
+#define stbds_hmlenu(t)    (stbds_arrlenu((t)-1)-1)
+
+#define stbds_shput(t, k, v) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), (k), sizeof (t)->key, STBDS_HM_STRING),   \
+     (t)[stbds_temp(t-1)].value = (v))
+
+#define stbds_shputs(t, s) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), (s).key, sizeof (s).key, STBDS_HM_STRING), \
+     (t)[stbds_temp(t-1)] = (s))
+
+#define stbds_shgeti(t,k) \
+     ((t) = stbds_hmget_key_wrapper((t), sizeof *(t), (k), sizeof (t)->key, STBDS_HM_STRING), \
+      stbds_temp(t))
+
+#define stbds_shgetp(t, k) \
+    ((void) stbds_shgeti(t,k), &(t)[stbds_temp(t-1)])
+
+#define stbds_shdel(t,k) \
+    (((t) = stbds_hmdel_key((t),sizeof *(t), (k), sizeof (t)->key, STBDS_OFFSETOF((t),key), STBDS_HM_STRING)),(t)?stbds_temp((t)-1):0)
+
+#define stbds_sh_new_arena(t)  \
+    ((t) = stbds_shmode_func_wrapper(t, sizeof *(t), STBDS_SH_ARENA))
+#define stbds_sh_new_strdup(t) \
+    ((t) = stbds_shmode_func_wrapper(t, sizeof *(t), STBDS_SH_STRDUP))
+
+#define stbds_shdefault(t, v) stbds_hmdefault(t,v)
+#define stbds_shdefaults(t, s) stbds_hmdefaults(t,s)
+
+#define stbds_shfree       stbds_hmfree
+#define stbds_shlenu       stbds_hmlenu
+
+#define stbds_shgets(t, k) (*stbds_shgetp(t,k))
+#define stbds_shget(t, k)  (stbds_shgetp(t,k)->value)
+#define stbds_shlen        stbds_hmlen
+
+typedef struct
+{
+  size_t      length;
+  size_t      capacity;
+  void      * hash_table;
+  ptrdiff_t   temp;
+} stbds_array_header;
+
+typedef struct stbds_string_block
+{
+  struct stbds_string_block *next;
+  char storage[8];
+} stbds_string_block;
+
+struct stbds_string_arena
+{
+  stbds_string_block *storage;
+  size_t remaining;
+  unsigned char block;
+  unsigned char mode;  // this isn't used by the string arena itself
+};
+
+enum
+{
+   STBDS_HM_BINARY,
+   STBDS_HM_STRING,
+};
+
+enum
+{
+   STBDS_SH_NONE,
+   STBDS_SH_STRDUP,
+   STBDS_SH_ARENA
+};
+
+#ifdef __cplusplus
+// in C we use implicit assignment from these void*-returning functions to T*.
+// in C++ these templates make the same code work
+template<class T> static T * stbds_arrgrowf_wrapper(T *a, size_t elemsize, size_t addlen, size_t min_cap) {
+  return (T*)stbds_arrgrowf((void *)a, elemsize, addlen, min_cap);
+}
+template<class T> static T * stbds_hmget_key_wrapper(T *a, size_t elemsize, void *key, size_t keysize, int mode) {
+  return (T*)stbds_hmget_key((void*)a, elemsize, key, keysize, mode);
+}
+template<class T> static T * stbds_hmput_default_wrapper(T *a, size_t elemsize) {
+  return (T*)stbds_hmput_default((void *)a, elemsize);
+}
+template<class T> static T * stbds_hmput_key_wrapper(T *a, size_t elemsize, void *key, size_t keysize, int mode) {
+  return (T*)stbds_hmput_key((void*)a, elemsize, key, keysize, mode);
+}
+template<class T> static T * stbds_hmdel_key_wrapper(T *a, size_t elemsize, void *key, size_t keysize, size_t keyoffset, int mode){
+  return (T*)stbds_hmdel_key((void*)a, elemsize, key, keysize, keyoffset, mode);
+}
+template<class T> static T * stbds_shmode_func_wrapper(T *, size_t elemsize, int mode) {
+  return stbds_shmode_func(elemsize, mode);
+}
+#else
+#define stbds_arrgrowf_wrapper            stbds_arrgrowf
+#define stbds_hmget_key_wrapper           stbds_hmget_key
+#define stbds_hmput_default_wrapper       stbds_hmput_default
+#define stbds_hmput_key_wrapper           stbds_hmput_key
+#define stbds_hmdel_key_wrapper           stbds_hmdel_key
+#define stbds_shmode_func_wrapper(t,e,m)  stbds_shmode_func(e,m)
+#endif
+
+#endif // INCLUDE_STB_DS_H
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+//   IMPLEMENTATION
+//
+
+#ifdef STB_DS_IMPLEMENTATION
+#include <assert.h>
+#include <string.h>
+
+#ifndef STBDS_ASSERT
+#define STBDS_ASSERT(x)   ((void) 0)
+#endif
+
+#ifdef STBDS_STATISTICS
+#define STBDS_STATS(x)   x
+size_t stbds_array_grow;
+size_t stbds_hash_grow;
+size_t stbds_hash_shrink;
+size_t stbds_hash_rebuild;
+size_t stbds_hash_probes;
+size_t stbds_hash_alloc;
+size_t stbds_rehash_probes;
+size_t stbds_rehash_items;
+#else
+#define STBDS_STATS(x)
+#endif
+
+//
+// stbds_arr implementation
+//
+
+void *stbds_arrgrowf(void *a, size_t elemsize, size_t addlen, size_t min_cap)
+{
+  void *b;
+  size_t min_len = stbds_arrlen(a) + addlen;
+
+  // compute the minimum capacity needed
+  if (min_len > min_cap)
+    min_cap = min_len;
+
+  if (min_cap <= stbds_arrcap(a))
+    return a;
+
+  // increase needed capacity to guarantee O(1) amortized
+  if (min_cap < 2 * stbds_arrcap(a))
+    min_cap = 2 * stbds_arrcap(a);
+  else if (min_cap < 4)
+    min_cap = 4;
+
+  b = realloc((a) ? stbds_header(a) : 0, elemsize * min_cap + sizeof(stbds_array_header));
+  b = (char *) b + sizeof(stbds_array_header);
+  if (a == NULL) {
+    stbds_header(b)->length = 0;
+    stbds_header(b)->hash_table = 0;
+  } else {
+    STBDS_STATS(++stbds_array_grow);
+  }
+  stbds_header(b)->capacity = min_cap;
+  return b;
+}
+
+//
+// stbds_hm hash table implementation
+//
+
+#define STBDS_CACHE_LINE_SIZE   64
+#define STBDS_BUCKET_LENGTH      8
+#define STBDS_BUCKET_SHIFT       3
+#define STBDS_BUCKET_MASK       (STBDS_BUCKET_LENGTH-1)
+
+#define STBDS_ALIGN_FWD(n,a)   (((n) + (a) - 1) & ~((a)-1))
+
+typedef struct
+{
+   size_t    hash [STBDS_BUCKET_LENGTH];
+   ptrdiff_t index[STBDS_BUCKET_LENGTH];
+} stbds_hash_bucket; // in 32-bit, this is one 64-byte cache line; in 64-bit, each array is one 64-byte cache line
+
+typedef struct
+{
+  size_t slot_count;
+  size_t used_count;
+  size_t used_count_threshold;
+  size_t used_count_shrink_threshold;
+  size_t tombstone_count;
+  size_t tombstone_count_threshold;
+  size_t seed;
+  size_t slot_count_log2;
+  stbds_string_arena string;
+  stbds_hash_bucket *storage; // not a separate allocation, just 64-byte aligned storage after this struct
+} stbds_hash_index;
+
+#define STBDS_INDEX_EMPTY    -1
+#define STBDS_INDEX_DELETED  -2
+#define STBDS_INDEX_IN_USE(x)  ((x) >= 0)
+
+#define STBDS_HASH_EMPTY      0
+#define STBDS_HASH_DELETED    1
+
+static size_t stbds_hash_seed=0x31415926;
+
+void stbds_rand_seed(size_t seed)
+{
+  stbds_hash_seed = seed;
+}
+
+#define stbds_load_32_or_64(var, temp, v32, v64_hi, v64_lo)                                          \
+  temp = v64_lo ^ v32, temp <<= 16, temp <<= 16, temp >>= 16, temp >>= 16, /* discard if 32-bit */   \
+  var = v64_hi, var <<= 16, var <<= 16,                                    /* discard if 32-bit */   \
+  var ^= temp ^ v32
+
+#define STBDS_SIZE_T_BITS           ((sizeof (size_t)) * 8)
+
+static size_t stbds_probe_position(size_t hash, size_t slot_count, size_t slot_log2)
+{
+  #if 1
+  size_t pos = (hash >> (STBDS_SIZE_T_BITS-slot_log2));
+  STBDS_ASSERT(pos < slot_count);
+  return pos;
+  #else
+  return hash & (slot_count-1);
+  #endif
+}
+
+static size_t stbds_log2(size_t slot_count)
+{
+  size_t n=0;
+  while (slot_count > 1) {
+    slot_count >>= 1;
+    ++n;
+  }
+  return n;
+}
+
+static stbds_hash_index *stbds_make_hash_index(size_t slot_count, stbds_hash_index *ot)
+{
+  stbds_hash_index *t;
+  t = (stbds_hash_index *) realloc(0,(slot_count >> STBDS_BUCKET_SHIFT) * sizeof(stbds_hash_bucket) + sizeof(stbds_hash_index) + STBDS_CACHE_LINE_SIZE-1);
+  t->storage = (stbds_hash_bucket *) STBDS_ALIGN_FWD((size_t) (t+1), STBDS_CACHE_LINE_SIZE);
+  t->slot_count = slot_count;
+  t->slot_count_log2 = stbds_log2(slot_count);
+  t->tombstone_count = 0;
+  t->used_count = 0;
+
+  #if 0 // A1
+  t->used_count_threshold        = slot_count*12/16; // if 12/16th of table is occupied, grow
+  t->tombstone_count_threshold   = slot_count* 2/16; // if tombstones are 2/16th of table, rebuild
+  t->used_count_shrink_threshold = slot_count* 4/16; // if table is only 4/16th full, shrink
+  #elif 1 // A2
+  //t->used_count_threshold        = slot_count*12/16; // if 12/16th of table is occupied, grow
+  //t->tombstone_count_threshold   = slot_count* 3/16; // if tombstones are 3/16th of table, rebuild
+  //t->used_count_shrink_threshold = slot_count* 4/16; // if table is only 4/16th full, shrink
+
+  // compute without overflowing
+  t->used_count_threshold        = slot_count - (slot_count>>2);
+  t->tombstone_count_threshold   = (slot_count>>3) + (slot_count>>4);
+  t->used_count_shrink_threshold = slot_count >> 2;
+
+  #elif 0 // B1
+  t->used_count_threshold        = slot_count*13/16; // if 13/16th of table is occupied, grow
+  t->tombstone_count_threshold   = slot_count* 2/16; // if tombstones are 2/16th of table, rebuild
+  t->used_count_shrink_threshold = slot_count* 5/16; // if table is only 5/16th full, shrink
+  #else // C1
+  t->used_count_threshold        = slot_count*14/16; // if 14/16th of table is occupied, grow
+  t->tombstone_count_threshold   = slot_count* 2/16; // if tombstones are 2/16th of table, rebuild
+  t->used_count_shrink_threshold = slot_count* 6/16; // if table is only 6/16th full, shrink
+  #endif
+  // Following statistics were measured on a Core i7-6700 @ 4.00Ghz, compiled with clang 7.0.1 -O2
+    // Note that the larger tables have high variance as they were run fewer times
+  //     A1            A2          B1           C1
+  //    0.10ms :     0.10ms :     0.10ms :     0.11ms :      2,000 inserts creating 2K table   
+  //    0.96ms :     0.95ms :     0.97ms :     1.04ms :     20,000 inserts creating 20K table  
+  //   14.48ms :    14.46ms :    10.63ms :    11.00ms :    200,000 inserts creating 200K table 
+  //  195.74ms :   196.35ms :   203.69ms :   214.92ms :  2,000,000 inserts creating 2M table   
+  // 2193.88ms :  2209.22ms :  2285.54ms :  2437.17ms : 20,000,000 inserts creating 20M table  
+  //   65.27ms :    53.77ms :    65.33ms :    65.47ms : 500,000 inserts & deletes in 2K table  
+  //   72.78ms :    62.45ms :    71.95ms :    72.85ms : 500,000 inserts & deletes in 20K table 
+  //   89.47ms :    77.72ms :    96.49ms :    96.75ms : 500,000 inserts & deletes in 200K table
+  //   97.58ms :    98.14ms :    97.18ms :    97.53ms : 500,000 inserts & deletes in 2M table  
+  //  118.61ms :   119.62ms :   120.16ms :   118.86ms : 500,000 inserts & deletes in 20M table 
+  //  192.11ms :   194.39ms :   196.38ms :   195.73ms : 500,000 inserts & deletes in 200M table
+
+  if (slot_count <= STBDS_BUCKET_LENGTH)
+    t->used_count_shrink_threshold = 0;
+  // to avoid infinite loop, we need to guarantee that at least one slot is empty and will terminate probes
+  STBDS_ASSERT(t->used_count_threshold + t->tombstone_count_threshold < t->slot_count);
+  STBDS_STATS(++stbds_hash_alloc);
+  if (ot) {
+    t->string = ot->string;
+    // reuse old seed so we can reuse old hashes so below "copy out old data" doesn't do any hashing
+    t->seed = ot->seed;
+  } else {
+    size_t a,b,temp;
+    memset(&t->string, 0, sizeof(t->string));
+    t->seed = stbds_hash_seed;
+    // LCG
+    // in 32-bit, a =          2147001325   b =  715136305
+    // in 64-bit, a = 2862933555777941757   b = 3037000493
+    stbds_load_32_or_64(a,temp, 2147001325, 0x27bb2ee6, 0x87b0b0fd);
+    stbds_load_32_or_64(b,temp,  715136305,          0, 0xb504f32d);
+    stbds_hash_seed = stbds_hash_seed  * a + b;
+  }
+
+  {
+    size_t i,j;
+    for (i=0; i < slot_count >> STBDS_BUCKET_SHIFT; ++i) {
+      stbds_hash_bucket *b = &t->storage[i];
+      for (j=0; j < STBDS_BUCKET_LENGTH; ++j)
+        b->hash[j] = STBDS_HASH_EMPTY;
+      for (j=0; j < STBDS_BUCKET_LENGTH; ++j)
+        b->index[j] = STBDS_INDEX_EMPTY;
+    }
+  }
+
+  // copy out the old data, if any
+  if (ot) {
+    size_t i,j;
+    t->used_count = ot->used_count;
+    for (i=0; i < ot->slot_count >> STBDS_BUCKET_SHIFT; ++i) {
+      stbds_hash_bucket *ob = &ot->storage[i];
+      for (j=0; j < STBDS_BUCKET_LENGTH; ++j) {
+        if (STBDS_INDEX_IN_USE(ob->index[j])) {
+          size_t hash = ob->hash[j];
+          size_t pos = stbds_probe_position(hash, t->slot_count, t->slot_count_log2);
+          size_t step = STBDS_BUCKET_LENGTH;
+          STBDS_STATS(++stbds_rehash_items);
+          for (;;) {
+            size_t limit,z;
+            stbds_hash_bucket *bucket;
+            pos &= (t->slot_count-1);
+            bucket = &t->storage[pos >> STBDS_BUCKET_SHIFT];
+            STBDS_STATS(++stbds_rehash_probes);
+
+            for (z=pos & STBDS_BUCKET_MASK; z < STBDS_BUCKET_LENGTH; ++z) {
+              if (bucket->hash[z] == 0) {
+                bucket->hash[z] = hash;
+                bucket->index[z] = ob->index[j];
+                goto done;
+              }
+            }
+
+            limit = pos & STBDS_BUCKET_MASK;
+            for (z = 0; z < limit; ++z) {
+              if (bucket->hash[z] == 0) {
+                bucket->hash[z] = hash;
+                bucket->index[z] = ob->index[j];
+                goto done;
+              }
+            }
+
+            pos += step;                  // quadratic probing
+            step += STBDS_BUCKET_LENGTH;
+          }
+        }
+       done:
+        ;
+      }
+    }
+  }
+
+  return t;
+}
+
+#define STBDS_ROTATE_LEFT(val, n)   (((val) << (n)) | ((val) >> (STBDS_SIZE_T_BITS - (n))))
+#define STBDS_ROTATE_RIGHT(val, n)  (((val) >> (n)) | ((val) << (STBDS_SIZE_T_BITS - (n))))
+
+size_t stbds_hash_string(char *str, size_t seed)
+{
+  size_t hash = seed;
+  while (*str)
+     hash = STBDS_ROTATE_LEFT(hash, 9) + (unsigned char) *str++;
+
+  // Thomas Wang 64-to-32 bit mix function, hopefully also works in 32 bits
+  hash ^= seed;
+  hash = (~hash) + (hash << 18);
+  hash ^= hash ^ STBDS_ROTATE_RIGHT(hash,31);
+  hash = hash * 21;
+  hash ^= hash ^ STBDS_ROTATE_RIGHT(hash,11);
+  hash += (hash << 6);
+  hash ^= STBDS_ROTATE_RIGHT(hash,22);
+  return hash+seed;
+}
+
+#ifdef STBDS_SIPHASH_2_4
+#define STBDS_SIPHASH_C_ROUNDS 2
+#define STBDS_SIPHASH_D_ROUNDS 4
+typedef int STBDS_SIPHASH_2_4_can_only_be_used_in_64_bit_builds[sizeof(size_t) == 8 ? 1 : -1];
+#endif
+
+#ifndef STBDS_SIPHASH_C_ROUNDS
+#define STBDS_SIPHASH_C_ROUNDS 1
+#endif
+#ifndef STBDS_SIPHASH_D_ROUNDS
+#define STBDS_SIPHASH_D_ROUNDS 1
+#endif
+
+static size_t stbds_siphash_bytes(void *p, size_t len, size_t seed)
+{
+  unsigned char *d = (unsigned char *) p;
+  size_t i,j;
+  size_t v0,v1,v2,v3, data;
+
+  // hash that works on 32- or 64-bit registers without knowing which we have
+  // (computes different results on 32-bit and 64-bit platform)
+  // derived from siphash, but on 32-bit platforms very different as it uses 4 32-bit state not 4 64-bit
+  v0 = ((((size_t) 0x736f6d65 << 16) << 16) + 0x70736575) ^  seed;
+  v1 = ((((size_t) 0x646f7261 << 16) << 16) + 0x6e646f6d) ^ ~seed;
+  v2 = ((((size_t) 0x6c796765 << 16) << 16) + 0x6e657261) ^  seed; 
+  v3 = ((((size_t) 0x74656462 << 16) << 16) + 0x79746573) ^ ~seed;
+
+  #ifdef STBDS_TEST_SIPHASH_2_4
+  // hardcoded with key material in the siphash test vectors
+  v0 ^= 0x0706050403020100ull ^  seed;
+  v1 ^= 0x0f0e0d0c0b0a0908ull ^ ~seed;
+  v2 ^= 0x0706050403020100ull ^  seed;
+  v3 ^= 0x0f0e0d0c0b0a0908ull ^ ~seed;
+  #endif
+
+  #define STBDS_SIPROUND() \
+    do {                   \
+      v0 += v1; v1 = STBDS_ROTATE_LEFT(v1, 13);  v1 ^= v0; v0 = STBDS_ROTATE_LEFT(v0,STBDS_SIZE_T_BITS/2); \
+      v2 += v3; v3 = STBDS_ROTATE_LEFT(v3, 16);  v3 ^= v2;                                                 \
+      v2 += v1; v1 = STBDS_ROTATE_LEFT(v1, 17);  v1 ^= v2; v2 = STBDS_ROTATE_LEFT(v2,STBDS_SIZE_T_BITS/2); \
+      v0 += v3; v3 = STBDS_ROTATE_LEFT(v3, 21);  v3 ^= v0;                                                 \
+    } while (0)
+
+  for (i=0; i+sizeof(size_t) <= len; i += sizeof(size_t), d += sizeof(size_t)) {
+    data = d[0] | (d[1] << 8) | (d[2] << 16) | (d[3] << 24);
+    data |= (size_t) (d[4] | (d[5] << 8) | (d[6] << 16) | (d[7] << 24)) << 16 << 16; // discarded if size_t == 4
+
+    v3 ^= data;
+    for (j=0; j < STBDS_SIPHASH_C_ROUNDS; ++j)
+      STBDS_SIPROUND();
+    v0 ^= data;
+  }
+  data = len << (STBDS_SIZE_T_BITS-8);
+  switch (len - i) {
+    case 7: data |= ((size_t) d[6] << 48);
+    case 6: data |= ((size_t) d[5] << 40);
+    case 5: data |= ((size_t) d[4] << 32);
+    case 4: data |= (d[3] << 24);
+    case 3: data |= (d[2] << 16);
+    case 2: data |= (d[1] << 8);
+    case 1: data |= d[0];
+    case 0: break;
+  }
+  v3 ^= data;
+  for (j=0; j < STBDS_SIPHASH_C_ROUNDS; ++j)
+    STBDS_SIPROUND();
+  v0 ^= data;
+  v2 ^= 0xff;
+  for (j=0; j < STBDS_SIPHASH_D_ROUNDS; ++j)
+    STBDS_SIPROUND();
+#ifdef STBDS_SIPHASH_2_4
+  return v0^v1^v2^v3;
+#else
+  return v1^v2^v3; // slightly stronger since v0^v3 in above cancels out final round operation
+#endif
+}
+
+size_t stbds_hash_bytes(void *p, size_t len, size_t seed)
+{
+#ifdef STBDS_SIPHASH_2_4
+  return stbds_siphash_bytes(p,len,seed);
+#else
+  unsigned char *d = (unsigned char *) p;
+
+  if (len == 4) {
+    unsigned int hash = d[0] | (d[1] << 8) | (d[2] << 16) | (d[3] << 24);
+    #if 0
+    // HASH32-A  Bob Jenkin's hash function w/o large constants
+    hash ^= seed ^ len;
+    hash -= (hash<<6);
+    hash ^= (hash>>17);
+    hash -= (hash<<9);
+    hash ^= (hash<<4);
+    hash -= (hash<<3);
+    hash ^= (hash<<10);
+    hash ^= (hash>>15);
+    #elif 1
+    // HASH32-BB  Bob Jenkin's presumably-accidental version of Thomas Wang hash with rotates turned into shifts.
+    // Note that converting these back to rotates makes it run a lot slower, presumably due to collisions, so I'm
+    // not really sure what's going on.
+    hash ^= seed ^ len;
+    hash = (hash ^ 61) ^ (hash >> 16);
+    hash = hash + (hash << 3);
+    hash = hash ^ (hash >> 4);
+    hash = hash * 0x27d4eb2d;
+    hash = hash ^ (hash >> 15);
+    #else  // HASH32-C   -  Murmur3
+    hash *= 0xcc9e2d51;
+    hash = (hash << 17) | (hash >> 15);
+    hash *= 0x1b873593;
+    hash ^= seed;
+    hash = (hash << 19) | (hash >> 13);
+    hash = hash*5 + 0xe6546b64;
+    hash ^= len;
+    hash ^= hash >> 16;
+    hash *= 0x85ebca6b;
+    hash ^= hash >> 13;
+    hash *= 0xc2b2ae35;
+    hash ^= hash >> 16;
+    #endif
+    // Following statistics were measured on a Core i7-6700 @ 4.00Ghz, compiled with clang 7.0.1 -O2
+    // Note that the larger tables have high variance as they were run fewer times
+    //  HASH32-A   //  HASH32-BB  //  HASH32-C
+    //    0.10ms   //    0.10ms   //    0.10ms :      2,000 inserts creating 2K table   
+    //    0.96ms   //    0.95ms   //    0.99ms :     20,000 inserts creating 20K table  
+    //   14.69ms   //   14.43ms   //   14.97ms :    200,000 inserts creating 200K table 
+    //  199.99ms   //  195.36ms   //  202.05ms :  2,000,000 inserts creating 2M table   
+    // 2234.84ms   // 2187.74ms   // 2240.38ms : 20,000,000 inserts creating 20M table  
+    //   55.68ms   //   53.72ms   //   57.31ms : 500,000 inserts & deletes in 2K table  
+    //   63.43ms   //   61.99ms   //   65.73ms : 500,000 inserts & deletes in 20K table 
+    //   80.04ms   //   77.96ms   //   81.83ms : 500,000 inserts & deletes in 200K table
+    //  100.42ms   //   97.40ms   //  102.39ms : 500,000 inserts & deletes in 2M table  
+    //  119.71ms   //  120.59ms   //  121.63ms : 500,000 inserts & deletes in 20M table 
+    //  185.28ms   //  195.15ms   //  187.74ms : 500,000 inserts & deletes in 200M table
+    //   15.58ms   //   14.79ms   //   15.52ms : 200,000 inserts creating 200K table with varying key spacing
+
+    return (((size_t) hash << 16 << 16) | hash) ^ seed;
+  } else if (len == 8 && sizeof(size_t) == 8) {
+    size_t hash = d[0] | (d[1] << 8) | (d[2] << 16) | (d[3] << 24) | ((size_t)d[4] << 32) | ((size_t)d[5] << 40) | ((size_t)d[6] << 48) | ((size_t)d[7] << 56);
+    hash ^= seed ^ len;
+    hash = (~hash) + (hash << 21);
+    hash ^= STBDS_ROTATE_RIGHT(hash,24);
+    hash *= 265;
+    hash ^= STBDS_ROTATE_RIGHT(hash,14);
+    hash *= 21;
+    hash ^= STBDS_ROTATE_RIGHT(hash,28);
+    hash += (hash << 31);
+    hash = (~hash) + (hash << 18);
+    return hash^seed;
+  } else {
+    return stbds_siphash_bytes(p,len,seed);
+  }
+#endif
+}
+
+static int stbds_is_key_equal(void *a, size_t elemsize, void *key, size_t keysize, int mode, size_t i)
+{
+  if (mode >= STBDS_HM_STRING)
+    return 0==strcmp((char *) key, * (char **) ((char *) a + elemsize*i));
+  else
+    return 0==memcmp(key, (char *) a + elemsize*i, keysize);
+}
+
+#define STBDS_HASH_TO_ARR(x,elemsize) ((char*) (x) - (elemsize))
+#define STBDS_ARR_TO_HASH(x,elemsize) ((char*) (x) + (elemsize))
+#define STBDS_FREE(x)  realloc(x,0)
+
+#define stbds_hash_table(a)  ((stbds_hash_index *) stbds_header(a)->hash_table)
+ 
+void stbds_hmfree_func(void *a, size_t elemsize, size_t keyoff)
+{
+  if (a == NULL) return;
+  if (stbds_hash_table(a) != NULL) {
+     if (stbds_hash_table(a)->string.mode == STBDS_SH_STRDUP) {
+       size_t i;
+       // skip 0th element, which is default
+       for (i=1; i < stbds_header(a)->length; ++i)
+         STBDS_FREE(*(char**) ((char *) a + elemsize*i));
+     }
+     stbds_strreset(&stbds_hash_table(a)->string);
+   }
+  STBDS_FREE(stbds_header(a)->hash_table);
+  STBDS_FREE(stbds_header(a));
+}
+
+static ptrdiff_t stbds_hm_find_slot(void *a, size_t elemsize, void *key, size_t keysize, int mode)
+{
+  void *raw_a = STBDS_HASH_TO_ARR(a,elemsize);
+  stbds_hash_index *table = stbds_hash_table(raw_a);
+  size_t hash = mode >= STBDS_HM_STRING ? stbds_hash_string((char*)key,table->seed) : stbds_hash_bytes(key, keysize,table->seed);
+  size_t step = STBDS_BUCKET_LENGTH;
+  size_t limit,i;
+  size_t pos;
+  stbds_hash_bucket *bucket;
+
+  if (hash < 2) hash += 2; // stored hash values are forbidden from being 0, so we can detect empty slots
+
+  pos = stbds_probe_position(hash, table->slot_count, table->slot_count_log2);
+
+  for (;;) {
+    STBDS_STATS(++stbds_hash_probes);
+    bucket = &table->storage[pos >> STBDS_BUCKET_SHIFT];
+
+    // start searching from pos to end of bucket, this should help performance on small hash tables that fit in cache
+    for (i=pos & STBDS_BUCKET_MASK; i < STBDS_BUCKET_LENGTH; ++i) {
+      if (bucket->hash[i] == hash) {
+        if (stbds_is_key_equal(a, elemsize, key, keysize, mode, bucket->index[i])) {
+          return (pos & ~STBDS_BUCKET_MASK)+i;
+        }
+      } else if (bucket->hash[i] == STBDS_HASH_EMPTY) {
+        return -1;
+      }
+    }
+
+    // search from beginning of bucket to pos
+    limit = pos & STBDS_BUCKET_MASK;
+    for (i = 0; i < limit; ++i) {
+      if (bucket->hash[i] == hash) {
+        if (stbds_is_key_equal(a, elemsize, key, keysize, mode, bucket->index[i])) {
+          return (pos & ~STBDS_BUCKET_MASK)+i;
+        }
+      } else if (bucket->hash[i] == STBDS_HASH_EMPTY) {
+        return -1;
+      }
+    }
+
+    // quadratic probing
+    pos += step;
+    step += STBDS_BUCKET_LENGTH;
+    pos &= (table->slot_count-1);
+  }
+  /* NOTREACHED */
+  return -1;
+}
+
+void * stbds_hmget_key(void *a, size_t elemsize, void *key, size_t keysize, int mode)
+{
+  if (a == NULL) {
+    // make it non-empty so we can return a temp
+    a = stbds_arrgrowf(0, elemsize, 0, 1);
+    stbds_header(a)->length += 1;
+    memset(a, 0, elemsize);
+    stbds_temp(a) = STBDS_INDEX_EMPTY;
+    // adjust a to point after the default element
+    return STBDS_ARR_TO_HASH(a,elemsize);
+  } else {
+    stbds_hash_index *table;
+    void *raw_a = STBDS_HASH_TO_ARR(a,elemsize);
+    // adjust a to point to the default element
+    table = (stbds_hash_index *) stbds_header(raw_a)->hash_table;
+    if (table == 0) {
+      stbds_temp(raw_a) = -1;
+    } else {
+      ptrdiff_t slot = stbds_hm_find_slot(a, elemsize, key, keysize, mode);
+      if (slot < 0) {
+        stbds_temp(raw_a) = STBDS_INDEX_EMPTY;
+      } else {
+        stbds_hash_bucket *b = &table->storage[slot >> STBDS_BUCKET_SHIFT];
+        stbds_temp(raw_a) = b->index[slot & STBDS_BUCKET_MASK];
+      }
+    }
+    return a;
+  }
+}
+
+void * stbds_hmput_default(void *a, size_t elemsize)
+{
+  // three cases:
+  //   a is NULL <- allocate
+  //   a has a hash table but no entries, because of shmode <- grow
+  //   a has entries <- do nothing
+  if (a == NULL || stbds_header(STBDS_HASH_TO_ARR(a,elemsize))->length == 0) {
+    a = stbds_arrgrowf(a ? STBDS_HASH_TO_ARR(a,elemsize) : NULL, elemsize, 0, 1);
+    stbds_header(a)->length += 1;
+    memset(a, 0, elemsize);
+    a=STBDS_ARR_TO_HASH(a,elemsize);
+  }
+  return a;
+}
+
+static char *stbds_strdup(char *str);
+
+void *stbds_hmput_key(void *a, size_t elemsize, void *key, size_t keysize, int mode)
+{
+  void *raw_a;
+  stbds_hash_index *table;
+
+  if (a == NULL) {
+    a = stbds_arrgrowf(0, elemsize, 0, 1);
+    memset(a, 0, elemsize);
+    stbds_header(a)->length += 1;
+    // adjust a to point AFTER the default element
+    a = STBDS_ARR_TO_HASH(a,elemsize);
+  }
+
+  // adjust a to point to the default element
+  raw_a = a;
+  a = STBDS_HASH_TO_ARR(a,elemsize);
+
+  table = (stbds_hash_index *) stbds_header(a)->hash_table;
+
+  if (table == NULL || table->used_count >= table->used_count_threshold) {
+    stbds_hash_index *nt;
+    size_t slot_count;
+
+    slot_count = (table == NULL) ? STBDS_BUCKET_LENGTH : table->slot_count*2;
+    nt = stbds_make_hash_index(slot_count, table);
+    if (table) {
+      STBDS_FREE(table);
+    }
+    stbds_header(a)->hash_table = table = nt;
+    STBDS_STATS(++stbds_hash_grow);
+  }
+
+  // we iterate hash table explicitly because we want to track if we saw a tombstone
+  {
+    size_t hash = mode >= STBDS_HM_STRING ? stbds_hash_string((char*)key,table->seed) : stbds_hash_bytes(key, keysize,table->seed);
+    size_t step = STBDS_BUCKET_LENGTH;
+    size_t limit,i;
+    size_t pos;
+    ptrdiff_t tombstone = -1;
+    stbds_hash_bucket *bucket;
+
+    // stored hash values are forbidden from being 0, so we can detect empty slots to early out quickly
+    if (hash < 2) hash += 2;
+
+    pos = stbds_probe_position(hash, table->slot_count, table->slot_count_log2);
+
+    for (;;) {
+      STBDS_STATS(++stbds_hash_probes);
+      bucket = &table->storage[pos >> STBDS_BUCKET_SHIFT];
+
+      // start searching from pos to end of bucket
+      for (i=pos & STBDS_BUCKET_MASK; i < STBDS_BUCKET_LENGTH; ++i) {
+        if (bucket->hash[i] == hash) {
+          if (stbds_is_key_equal(raw_a, elemsize, key, keysize, mode, bucket->index[i])) {
+            stbds_temp(a) = bucket->index[i];
+            return STBDS_ARR_TO_HASH(a,elemsize);
+          }
+        } else if (bucket->hash[i] == 0) {
+          pos = (pos & ~STBDS_BUCKET_MASK) + i;
+          goto found_empty_slot;
+        } else if (tombstone < 0) {
+          if (bucket->index[i] == STBDS_INDEX_DELETED)
+            tombstone = (ptrdiff_t) ((pos & ~STBDS_BUCKET_MASK) + i);
+        }
+      }
+
+      // search from beginning of bucket to pos
+      limit = pos & STBDS_BUCKET_MASK;
+      for (i = 0; i < limit; ++i) {
+        if (bucket->hash[i] == hash) {
+          if (stbds_is_key_equal(raw_a, elemsize, key, keysize, mode, bucket->index[i])) {
+            stbds_temp(a) = bucket->index[i];
+            return STBDS_ARR_TO_HASH(a,elemsize);
+          }
+        } else if (bucket->hash[i] == 0) {
+          pos = (pos & ~STBDS_BUCKET_MASK) + i;
+          goto found_empty_slot;
+        } else if (tombstone < 0) {
+          if (bucket->index[i] == STBDS_INDEX_DELETED)
+            tombstone = (ptrdiff_t) ((pos & ~STBDS_BUCKET_MASK) + i);
+        }
+      }
+
+      // quadratic probing
+      pos += step;
+      step += STBDS_BUCKET_LENGTH;
+      pos &= (table->slot_count-1);
+    }
+   found_empty_slot:
+    if (tombstone >= 0) {
+      pos = tombstone;
+      --table->tombstone_count;
+    }
+    ++table->used_count;
+
+    {
+      ptrdiff_t i = (ptrdiff_t) stbds_arrlen(a);
+    // we want to do stbds_arraddn(1), but we can't use the macros since we don't have something of the right type
+      if ((size_t) i+1 > stbds_arrcap(a))
+        *(void **) &a = stbds_arrgrowf(a, elemsize, 1, 0);
+      raw_a = STBDS_ARR_TO_HASH(a,elemsize);
+
+      STBDS_ASSERT((size_t) i+1 <= stbds_arrcap(a));
+      stbds_header(a)->length = i+1;
+      bucket = &table->storage[pos >> STBDS_BUCKET_SHIFT];
+      bucket->hash[pos & STBDS_BUCKET_MASK] = hash;
+      bucket->index[pos & STBDS_BUCKET_MASK] = i-1;
+      stbds_temp(a) = i-1;
+
+      switch (table->string.mode) {
+         case STBDS_SH_STRDUP: *(char **) ((char *) a + elemsize*i) = stbds_strdup((char*) key); break;
+         case STBDS_SH_ARENA:  *(char **) ((char *) a + elemsize*i) = stbds_stralloc(&table->string, (char*)key); break;
+         default:              *(char **) ((char *) a + elemsize*i) = (char *) key; break;
+      }
+    }
+    return STBDS_ARR_TO_HASH(a,elemsize);
+  }
+}
+
+void * stbds_shmode_func(size_t elemsize, int mode)
+{
+  void *a = stbds_arrgrowf(0, elemsize, 0, 1);
+  stbds_hash_index *h;
+  stbds_header(a)->hash_table = h = (stbds_hash_index *) stbds_make_hash_index(STBDS_BUCKET_LENGTH, NULL);
+  h->string.mode = mode;
+  return STBDS_ARR_TO_HASH(a,elemsize);
+}
+
+void * stbds_hmdel_key(void *a, size_t elemsize, void *key, size_t keysize, size_t keyoffset, int mode)
+{
+  if (a == NULL) {
+    return 0;
+  } else {
+    stbds_hash_index *table;
+    void *raw_a = STBDS_HASH_TO_ARR(a,elemsize);
+    table = (stbds_hash_index *) stbds_header(raw_a)->hash_table;
+    stbds_temp(raw_a) = 0;
+    if (table == 0) {
+      return a;
+    } else {
+      ptrdiff_t slot;
+      slot = stbds_hm_find_slot(a, elemsize, key, keysize, mode);
+      if (slot < 0)
+        return a;
+      else {
+        stbds_hash_bucket *b = &table->storage[slot >> STBDS_BUCKET_SHIFT];
+        int i = slot & STBDS_BUCKET_MASK;
+        ptrdiff_t old_index = b->index[i];
+        ptrdiff_t final_index = (ptrdiff_t) stbds_arrlen(raw_a)-1-1; // minus one for the raw_a vs a, and minus one for 'last'
+        STBDS_ASSERT(slot < (ptrdiff_t) table->slot_count);
+        --table->used_count;
+        ++table->tombstone_count;
+        stbds_temp(raw_a) = 1;
+        STBDS_ASSERT(table->used_count >= 0);
+        //STBDS_ASSERT(table->tombstone_count < table->slot_count/4);
+        b->hash[i] = STBDS_HASH_DELETED;
+        b->index[i] = STBDS_INDEX_DELETED;
+
+        if (mode == STBDS_HM_STRING && table->string.mode == STBDS_SH_STRDUP)
+          STBDS_FREE(*(char**) ((char *) a+elemsize*old_index));
+
+        // if indices are the same, memcpy is a no-op, but back-pointer-fixup will fail, so skip
+        if (old_index != final_index) {
+          // swap delete 
+          memmove((char*) a + elemsize*old_index, (char*) a + elemsize*final_index, elemsize);
+
+          // now find the slot for the last element
+          if (mode == STBDS_HM_STRING)
+            slot = stbds_hm_find_slot(a, elemsize, *(char**) ((char *) a+elemsize*old_index + keyoffset), keysize, mode);
+          else
+            slot = stbds_hm_find_slot(a, elemsize,  (char* ) a+elemsize*old_index + keyoffset, keysize, mode);
+          STBDS_ASSERT(slot >= 0);
+          b = &table->storage[slot >> STBDS_BUCKET_SHIFT];
+          i = slot & STBDS_BUCKET_MASK;
+          STBDS_ASSERT(b->index[i] == final_index);
+          b->index[i] = old_index;
+        }
+        stbds_header(raw_a)->length -= 1;
+
+        if (table->used_count < table->used_count_shrink_threshold && table->slot_count > STBDS_BUCKET_LENGTH) {
+          stbds_header(raw_a)->hash_table = stbds_make_hash_index(table->slot_count>>1, table);
+          STBDS_FREE(table);
+          STBDS_STATS(++stbds_hash_shrink);
+        } else if (table->tombstone_count > table->tombstone_count_threshold) {
+          stbds_header(raw_a)->hash_table = stbds_make_hash_index(table->slot_count   , table);
+          STBDS_FREE(table);
+          STBDS_STATS(++stbds_hash_rebuild);
+        }
+
+        return a;
+      }
+    }
+  }
+  /* NOTREACHED */
+  return 0;
+}
+
+static char *stbds_strdup(char *str)
+{
+  // to keep replaceable allocator simple, we don't want to use strdup.
+  // rolling our own also avoids problem of strdup vs _strdup
+  size_t len = strlen(str)+1;
+  char *p = (char*) realloc(0, len);
+  memmove(p, str, len);
+  return p;
+}
+
+#ifndef STBDS_STRING_ARENA_BLOCKSIZE_MIN
+#define STBDS_STRING_ARENA_BLOCKSIZE_MIN  512
+#endif
+#ifndef STBDS_STRING_ARENA_BLOCKSIZE_MAX
+#define STBDS_STRING_ARENA_BLOCKSIZE_MAX  1<<20
+#endif
+
+char *stbds_stralloc(stbds_string_arena *a, char *str)
+{
+  char *p;
+  size_t len = strlen(str)+1;
+  if (len > a->remaining) {
+    // compute the next blocksize
+    size_t blocksize = a->block;
+
+    // size is 512, 512, 1024, 1024, 2048, 2048, 4096, 4096, etc., so that
+    // there are log(SIZE) allocations to free when we destroy the table
+    blocksize = (size_t) (STBDS_STRING_ARENA_BLOCKSIZE_MIN) << (blocksize>>1);
+
+    // if size is under 1M, advance to next blocktype
+    if (blocksize < (size_t)(STBDS_STRING_ARENA_BLOCKSIZE_MAX))
+      ++a->block;
+
+    if (len > blocksize) {
+      // if string is larger than blocksize, then just allocate the full size.
+      // note that we still advance string_block so block size will continue
+      // increasing, so e.g. if somebody only calls this with 1000-long strings,
+      // eventually the arena will start doubling and handling those as well
+      stbds_string_block *sb = (stbds_string_block *) realloc(0, sizeof(*sb)-8 + len);
+      memmove(sb->storage, str, len);
+      if (a->storage) {
+        // insert it after the first element, so that we don't waste the space there
+        sb->next = a->storage->next;
+        a->storage->next = sb;
+      } else {
+        sb->next = 0;
+        a->storage = sb;
+        a->remaining = 0; // this is redundant, but good for clarity
+      }
+      return sb->storage;
+    } else {
+      stbds_string_block *sb = (stbds_string_block *) realloc(0, sizeof(*sb)-8 + blocksize);
+      sb->next = a->storage;
+      a->storage = sb;
+      a->remaining = blocksize;
+    }
+  }
+
+  STBDS_ASSERT(len <= a->remaining);
+  p = a->storage->storage + a->remaining - len;
+  a->remaining -= len;
+  memmove(p, str, len);
+  return p;
+}
+
+void stbds_strreset(stbds_string_arena *a)
+{
+  stbds_string_block *x,*y;
+  x = a->storage;
+  while (x) {
+    y = x->next;
+    realloc(x,0);
+    x = y;
+  }
+  memset(a, 0, sizeof(*a));
+}
+
+#endif
+
+//////////////////////////////////////////////////////////////////////////////
+//
+//   UNIT TESTS
+//
+
+#ifdef STBDS_UNIT_TESTS
+#include <stdio.h>
+#ifndef STBDS_ASSERT
+#define STBDS_ASSERT assert
+#include <assert.h>
+#endif
+
+typedef struct { int key,b,c,d; } stbds_struct;
+
+static char buffer[256];
+char *strkey(int n)
+{
+   sprintf(buffer, "test_%d", n);
+   return buffer;
+}
+
+void stbds_unit_tests(void)
+{
+  const int testsize = 100000;
+  int *arr=NULL;
+  struct { int   key;        int value; } *intmap = NULL;
+  struct { char *key;        int value; } *strmap = NULL;
+  struct { stbds_struct key; int value; } *map    = NULL;
+  stbds_struct                            *map2   = NULL;
+  stbds_string_arena                       sa     = { 0 };
+
+  int i,j;
+
+  for (i=0; i < 20000; i += 50) {
+    for (j=0; j < i; ++j)
+      arrpush(arr,j);
+    arrfree(arr);
+  }
+
+  for (i=0; i < 4; ++i) {
+    arrpush(arr,1); arrpush(arr,2); arrpush(arr,3); arrpush(arr,4);
+    arrdel(arr,i);
+    arrfree(arr);
+    arrpush(arr,1); arrpush(arr,2); arrpush(arr,3); arrpush(arr,4);
+    arrdelswap(arr,i);
+    arrfree(arr);
+  }
+
+  for (i=0; i < 5; ++i) {
+    arrpush(arr,1); arrpush(arr,2); arrpush(arr,3); arrpush(arr,4);
+    stbds_arrins(arr,i,5);
+    assert(arr[i] == 5);
+    if (i < 4)
+      assert(arr[4] == 4);
+    arrfree(arr);
+  }
+
+  hmdefault(intmap, -1);
+  i=1; assert(hmget(intmap, i) == -1);
+  for (i=0; i < testsize; i+=2)
+    hmput(intmap, i, i*5);
+  for (i=0; i < testsize; i+=1)
+    if (i & 1) assert(hmget(intmap, i) == -1 );
+    else       assert(hmget(intmap, i) == i*5);
+  for (i=0; i < testsize; i+=2)
+    hmput(intmap, i, i*3);
+  for (i=0; i < testsize; i+=1)
+    if (i & 1) assert(hmget(intmap, i) == -1 );
+    else       assert(hmget(intmap, i) == i*3);
+  for (i=2; i < testsize; i+=4)
+    hmdel(intmap, i); // delete half the entries
+  for (i=0; i < testsize; i+=1)
+    if (i & 3) assert(hmget(intmap, i) == -1 );
+    else       assert(hmget(intmap, i) == i*3);
+  for (i=0; i < testsize; i+=1)
+    hmdel(intmap, i); // delete the rest of the entries    
+  for (i=0; i < testsize; i+=1)
+    assert(hmget(intmap, i) == -1 );
+  hmfree(intmap);
+  for (i=0; i < testsize; i+=2)
+    hmput(intmap, i, i*3);
+  hmfree(intmap);
+
+  #ifdef __clang__
+  intmap = NULL;
+  hmput(intmap, 15, 7);
+  hmput(intmap, 11, 3);
+  hmput(intmap,  9, 5);
+  assert(hmget(intmap, 9) == 5);
+  assert(hmget(intmap, 11) == 3);
+  assert(hmget(intmap, 15) == 7);
+  #endif
+
+  for (i=0; i < testsize; ++i)
+    stralloc(&sa, strkey(i));
+  strreset(&sa);
+
+  for (j=0; j < 2; ++j) {
+    if (j == 0)
+      sh_new_strdup(strmap);
+    else
+      sh_new_arena(strmap);
+    shdefault(strmap, -1);
+    for (i=0; i < testsize; i+=2)
+      shput(strmap, strkey(i), i*3);
+    for (i=0; i < testsize; i+=1)
+      if (i & 1) assert(shget(strmap, strkey(i)) == -1 );
+      else       assert(shget(strmap, strkey(i)) == i*3);
+    for (i=2; i < testsize; i+=4)
+      shdel(strmap, strkey(i)); // delete half the entries
+    for (i=0; i < testsize; i+=1)
+      if (i & 3) assert(shget(strmap, strkey(i)) == -1 );
+      else       assert(shget(strmap, strkey(i)) == i*3);
+    for (i=0; i < testsize; i+=1)
+      shdel(strmap, strkey(i)); // delete the rest of the entries    
+    for (i=0; i < testsize; i+=1)
+      assert(shget(strmap, strkey(i)) == -1 );
+    shfree(strmap);
+  }
+
+  {
+    struct { char *key; char value; } *hash = NULL;
+    char name[4] = "jen";
+    shput(hash, "bob"   , 'h');
+    shput(hash, "sally" , 'e');
+    shput(hash, "fred"  , 'l');
+    shput(hash, "jen"   , 'x');
+    shput(hash, "doug"  , 'o');
+
+    shput(hash, name    , 'l');
+    shfree(hash);
+  }
+
+  for (i=0; i < testsize; i += 2) {
+    stbds_struct s = { i,i*2,i*3,i*4 };
+    hmput(map, s, i*5);
+  }
+
+  for (i=0; i < testsize; i += 1) {
+    stbds_struct s = { i,i*2,i*3  ,i*4 };
+    stbds_struct t = { i,i*2,i*3+1,i*4 };
+    if (i & 1) assert(hmget(map, s) == 0);
+    else       assert(hmget(map, s) == i*5);
+    assert(hmget(map, t) == 0);
+  }
+
+  for (i=0; i < testsize; i += 2) {
+    stbds_struct s = { i,i*2,i*3,i*4 };
+    hmputs(map2, s);
+  }
+  hmfree(map);
+
+  for (i=0; i < testsize; i += 1) {
+    stbds_struct s = { i,i*2,i*3,i*4 };
+    stbds_struct t = { i,i*2,i*3,i*4 };
+    if (i & 1) assert(hmgets(map2, s.key).d == 0);
+    else       assert(hmgets(map2, s.key).d == i*4);
+  }
+  hmfree(map2);
+}
+#endif
+
+
+/*
+------------------------------------------------------------------------------
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2019 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+------------------------------------------------------------------------------
+*/

tests/test_ds.c

@@ -0,0 +1,416 @@
+#include <stdio.h>
+
+#ifdef DS_TEST
+#define STBDS_UNIT_TESTS
+#endif
+
+#ifdef DS_STATS
+#define STBDS_STATISTICS
+#endif
+
+#ifndef DS_PERF
+#define STBDS_ASSERT assert
+#include <assert.h>
+#endif
+
+//#define STBDS_SIPHASH_2_4
+#define STB_DS_IMPLEMENTATION
+#include "../stb_ds.h"
+
+size_t churn_inserts, churn_deletes;
+
+void churn(int a, int b, int count)
+{
+  struct { int key,value; } *map=NULL;
+  int i,j,n,k;
+  for (i=0; i < a; ++i)
+    hmput(map,i,i+1);
+  for (n=0; n < count; ++n) {
+    for (j=a; j < b; ++j,++i) {
+      hmput(map,i,i+1);
+    }
+    assert(hmlen(map) == b);
+    for (j=a; j < b; ++j) {
+      k=i-j-1;
+      k = hmdel(map,k);
+      assert(k != 0);
+    }
+    assert(hmlen(map) == a);
+  }
+  hmfree(map);
+  churn_inserts = i;
+  churn_deletes = (b-a) * n;
+}
+
+#ifdef DS_TEST
+int main(int argc, char **argv)
+{
+  stbds_unit_tests();
+  churn(0,100,1);
+  churn(3,7,50000);
+  churn(3,15,50000);
+  churn(16, 48, 25000);
+  churn(10, 15, 25000);
+  churn(200,500, 5000);
+  churn(2000,5000, 500);
+  churn(20000,50000, 50);
+  return 0;
+}
+#endif
+
+#ifdef DS_STATS
+#define MAX(a,b) ((a) > (b) ? (a) : (b))
+size_t max_hit_probes, max_miss_probes, total_put_probes, total_miss_probes, churn_misses;
+void churn_stats(int a, int b, int count)
+{
+  struct { int key,value; } *map=NULL;
+  int i,j,n,k;
+  churn_misses = 0;
+  for (i=0; i < a; ++i) {
+    hmput(map,i,i+1);
+    max_hit_probes = MAX(max_hit_probes, stbds_hash_probes);
+    total_put_probes += stbds_hash_probes;
+    stbds_hash_probes = 0;
+  }
+    
+  for (n=0; n < count; ++n) {
+    for (j=a; j < b; ++j,++i) {
+      hmput(map,i,i+1);
+      max_hit_probes = MAX(max_hit_probes, stbds_hash_probes);
+      total_put_probes += stbds_hash_probes;
+      stbds_hash_probes = 0;
+    }
+    for (j=0; j < (b-a)*10; ++j) {
+      k=i+j;
+      (void) hmgeti(map,k); // miss
+      max_miss_probes = MAX(max_miss_probes, stbds_hash_probes);
+      total_miss_probes += stbds_hash_probes;
+      stbds_hash_probes = 0;
+      ++churn_misses;
+    }
+    assert(hmlen(map) == b);
+    for (j=a; j < b; ++j) {
+      k=i-j-1;
+      k = hmdel(map,k);
+      stbds_hash_probes = 0;
+      assert(k);
+    }
+    assert(hmlen(map) == a);
+  }
+  hmfree(map);
+  churn_inserts = i;
+  churn_deletes = (b-a) * n;
+}
+
+void reset_stats(void)
+{
+  stbds_array_grow=0, 
+  stbds_hash_grow=0;
+  stbds_hash_shrink=0;
+  stbds_hash_rebuild=0;
+  stbds_hash_probes=0;
+  stbds_hash_alloc=0;
+  stbds_rehash_probes=0;
+  stbds_rehash_items=0;
+  max_hit_probes = 0;
+  max_miss_probes = 0;
+  total_put_probes = 0;
+  total_miss_probes = 0;
+}
+
+void print_churn_probe_stats(char *str)
+{
+  printf("Probes: %3d max hit, %3d max miss, %4.2f avg hit, %4.2f avg miss: %s\n",
+    (int) max_hit_probes, (int) max_miss_probes, (float) total_put_probes / churn_inserts, (float) total_miss_probes / churn_misses, str);
+  reset_stats();
+}
+
+int main(int arg, char **argv)
+{
+  churn_stats(0,500000,1); print_churn_probe_stats("Inserting 500000 items");
+  churn_stats(0,500000,1); print_churn_probe_stats("Inserting 500000 items");
+  churn_stats(0,500000,1); print_churn_probe_stats("Inserting 500000 items");
+  churn_stats(0,500000,1); print_churn_probe_stats("Inserting 500000 items");
+  churn_stats(49000,50000,500); print_churn_probe_stats("Deleting/Inserting 500000 items");
+  churn_stats(49000,50000,500); print_churn_probe_stats("Deleting/Inserting 500000 items");
+  churn_stats(49000,50000,500); print_churn_probe_stats("Deleting/Inserting 500000 items");
+  churn_stats(49000,50000,500); print_churn_probe_stats("Deleting/Inserting 500000 items");
+  return 0;
+}
+#endif
+
+#ifdef DS_PERF
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#define STB_DEFINE
+#define STB_NO_REGISTRY
+//#include "../stb.h"
+
+
+size_t t0, sum, mn,mx,count;
+void begin(void)
+{
+  size_t t0;
+  LARGE_INTEGER m;
+  QueryPerformanceCounter(&m);
+  t0 = m.QuadPart;
+  sum = 0;
+  count = 0;
+  mx = 0;
+  mn = ~(size_t) 0;
+}
+
+void measure(void)
+{
+  size_t t1, t;
+  LARGE_INTEGER m;
+  QueryPerformanceCounter(&m);
+  t1 = m.QuadPart;
+  t = t1-t0;
+  if (t1 < t0)
+    printf("ALERT: QueryPerformanceCounter was unordered!\n");
+  if (t < mn) mn = t;
+  if (t > mx) mx = t;
+  sum += t;
+  ++count;
+  t0 = t1;
+}
+
+void dont_measure(void)
+{
+  size_t t1, t;
+  LARGE_INTEGER m;
+  QueryPerformanceCounter(&m);
+  t0 = m.QuadPart;
+}
+
+double timer;
+void end(void)
+{
+  LARGE_INTEGER m;
+  QueryPerformanceFrequency(&m);
+
+  if (count > 3) {
+    // discard the highest and lowest
+    sum -= mn;
+    sum -= mx;
+    count -= 2;
+  }
+  timer = (double) (sum) / count / m.QuadPart * 1000;
+}
+
+void build(int a, int b, int count, int step)
+{
+  struct { int key,value; } *map=NULL;
+  int i,j,n,k;
+  for (i=0; i < a; ++i)
+    hmput(map,i*step,i+1);
+  measure();
+  churn_inserts = i;
+  hmfree(map);
+  dont_measure();
+}
+
+#ifdef STB__INCLUDE_STB_H
+void build_stb(int a, int b, int count, int step)
+{
+  stb_idict *d = stb_idict_new_size(8);
+  struct { int key,value; } *map=NULL;
+  int i,j,n,k;
+  for (i=0; i < a; ++i)
+    stb_idict_add(d, i*step, i+1);
+  measure();
+  churn_inserts = i;
+  stb_idict_destroy(d);
+  dont_measure();
+}
+#endif
+
+void churn_skip(unsigned int a, unsigned int b, int count)
+{
+  struct { unsigned int key,value; } *map=NULL;
+  unsigned int i,j,n,k;
+  for (i=0; i < a; ++i)
+    hmput(map,i,i+1);
+  dont_measure();
+  for (n=0; n < count; ++n) {
+    for (j=a; j < b; ++j,++i) {
+      hmput(map,i,i+1);
+    }
+    assert(hmlen(map) == b);
+    for (j=a; j < b; ++j) {
+      k=i-j-1;
+      k = hmdel(map,k);
+      assert(k != 0);
+    }
+    assert(hmlen(map) == a);
+  }
+  measure();
+  churn_inserts = i;
+  churn_deletes = (b-a) * n;
+  hmfree(map);
+  dont_measure();
+}
+
+typedef struct { int n[8]; } str32;
+void churn32(int a, int b, int count, int include_startup)
+{
+  struct { str32 key; int value; } *map=NULL;
+  int i,j,n;
+  str32 key = { 0 };
+  for (i=0; i < a; ++i) {
+    key.n[0] = i;
+    hmput(map,key,i+1);
+  }
+  if (!include_startup)
+    dont_measure();
+  for (n=0; n < count; ++n) {
+    for (j=a; j < b; ++j,++i) {
+      key.n[0] = i;
+      hmput(map,key,i+1);
+    }
+    assert(hmlen(map) == b);
+    for (j=a; j < b; ++j) {
+      key.n[0] = i-j-1;
+      hmdel(map,key);
+    }
+    assert(hmlen(map) == a);
+  }
+  measure();
+  hmfree(map);
+  churn_inserts = i;
+  churn_deletes = (b-a) * n;
+  dont_measure();
+}
+
+typedef struct { int n[32]; } str256;
+void churn256(int a, int b, int count, int include_startup)
+{
+  struct { str256 key; int value; } *map=NULL;
+  int i,j,n;
+  str256 key = { 0 };
+  for (i=0; i < a; ++i) {
+    key.n[0] = i;
+    hmput(map,key,i+1);
+  }
+  if (!include_startup)
+    dont_measure();
+  for (n=0; n < count; ++n) {
+    for (j=a; j < b; ++j,++i) {
+      key.n[0] = i;
+      hmput(map,key,i+1);
+    }
+    assert(hmlen(map) == b);
+    for (j=a; j < b; ++j) {
+      key.n[0] = i-j-1;
+      hmdel(map,key);
+    }
+    assert(hmlen(map) == a);
+  }
+  measure();
+  hmfree(map);
+  churn_inserts = i;
+  churn_deletes = (b-a) * n;
+  dont_measure();
+}
+
+void churn8(int a, int b, int count, int include_startup)
+{
+  struct { size_t key,value; } *map=NULL;
+  int i,j,n,k;
+  for (i=0; i < a; ++i)
+    hmput(map,i,i+1);
+  if (!include_startup)
+    dont_measure();
+  for (n=0; n < count; ++n) {
+    for (j=a; j < b; ++j,++i) {
+      hmput(map,i,i+1);
+    }
+    assert(hmlen(map) == b);
+    for (j=a; j < b; ++j) {
+      k=i-j-1;
+      k = hmdel(map,k);
+      assert(k != 0);
+    }
+    assert(hmlen(map) == a);
+  }
+  measure();
+  hmfree(map);
+  churn_inserts = i;
+  churn_deletes = (b-a) * n;
+  dont_measure();
+}
+
+
+int main(int arg, char **argv)
+{
+  int n,s,w;
+  double worst = 0;
+
+#if 0
+  begin(); for (n=0; n < 2000; ++n) { build_stb(2000,0,0,1);          } end(); printf("  // %7.2fms :      2,000 inserts creating 2K table\n", timer);
+  begin(); for (n=0; n <  500; ++n) { build_stb(20000,0,0,1);         } end(); printf("  // %7.2fms :     20,000 inserts creating 20K table\n", timer);
+  begin(); for (n=0; n <  100; ++n) { build_stb(200000,0,0,1);        } end(); printf("  // %7.2fms :    200,000 inserts creating 200K table\n", timer);
+  begin(); for (n=0; n <   10; ++n) { build_stb(2000000,0,0,1);       } end(); printf("  // %7.2fms :  2,000,000 inserts creating 2M table\n", timer);
+  begin(); for (n=0; n <    5; ++n) { build_stb(20000000,0,0,1);      } end(); printf("  // %7.2fms : 20,000,000 inserts creating 20M table\n", timer);
+#endif
+
+  begin(); for (n=0; n < 2000; ++n) { churn8(2000,0,0,1);          } end(); printf("  // %7.2fms :      2,000 inserts creating 2K table w/ 8-byte key\n", timer);
+  begin(); for (n=0; n <  500; ++n) { churn8(20000,0,0,1);         } end(); printf("  // %7.2fms :     20,000 inserts creating 20K table w/ 8-byte key\n", timer);
+  begin(); for (n=0; n <  100; ++n) { churn8(200000,0,0,1);        } end(); printf("  // %7.2fms :    200,000 inserts creating 200K table w/ 8-byte key\n", timer);
+  begin(); for (n=0; n <   10; ++n) { churn8(2000000,0,0,1);       } end(); printf("  // %7.2fms :  2,000,000 inserts creating 2M table w/ 8-byte key\n", timer);
+  begin(); for (n=0; n <    5; ++n) { churn8(20000000,0,0,1);      } end(); printf("  // %7.2fms : 20,000,000 inserts creating 20M table w/ 8-byte key\n", timer);
+
+#if 0
+  begin(); for (n=0; n < 2000; ++n) { churn32(2000,0,0,1);          } end(); printf("  // %7.2fms :      2,000 inserts creating 2K table w/ 32-byte key\n", timer);
+  begin(); for (n=0; n <  500; ++n) { churn32(20000,0,0,1);         } end(); printf("  // %7.2fms :     20,000 inserts creating 20K table w/ 32-byte key\n", timer);
+  begin(); for (n=0; n <  100; ++n) { churn32(200000,0,0,1);        } end(); printf("  // %7.2fms :    200,000 inserts creating 200K table w/ 32-byte key\n", timer);
+  begin(); for (n=0; n <   10; ++n) { churn32(2000000,0,0,1);       } end(); printf("  // %7.2fms :  2,000,000 inserts creating 2M table w/ 32-byte key\n", timer);
+  begin(); for (n=0; n <    5; ++n) { churn32(20000000,0,0,1);      } end(); printf("  // %7.2fms : 20,000,000 inserts creating 20M table w/ 32-byte key\n", timer);
+
+  begin(); for (n=0; n < 2000; ++n) { churn256(2000,0,0,1);          } end(); printf("  // %7.2fms :      2,000 inserts creating 2K table w/ 256-byte key\n", timer);
+  begin(); for (n=0; n <  500; ++n) { churn256(20000,0,0,1);         } end(); printf("  // %7.2fms :     20,000 inserts creating 20K table w/ 256-byte key\n", timer);
+  begin(); for (n=0; n <  100; ++n) { churn256(200000,0,0,1);        } end(); printf("  // %7.2fms :    200,000 inserts creating 200K table w/ 256-byte key\n", timer);
+  begin(); for (n=0; n <   10; ++n) { churn256(2000000,0,0,1);       } end(); printf("  // %7.2fms :  2,000,000 inserts creating 2M table w/ 256-byte key\n", timer);
+  begin(); for (n=0; n <    5; ++n) { churn256(20000000,0,0,1);      } end(); printf("  // %7.2fms : 20,000,000 inserts creating 20M table w/ 256-byte key\n", timer);
+#endif
+
+  begin(); for (n=0; n < 2000; ++n) { build(2000,0,0,1);          } end(); printf("  // %7.2fms :      2,000 inserts creating 2K table w/ 4-byte key\n", timer);
+  begin(); for (n=0; n <  500; ++n) { build(20000,0,0,1);         } end(); printf("  // %7.2fms :     20,000 inserts creating 20K table w/ 4-byte key\n", timer);
+  begin(); for (n=0; n <  100; ++n) { build(200000,0,0,1);        } end(); printf("  // %7.2fms :    200,000 inserts creating 200K table w/ 4-byte key\n", timer);
+  begin(); for (n=0; n <   10; ++n) { build(2000000,0,0,1);       } end(); printf("  // %7.2fms :  2,000,000 inserts creating 2M table w/ 4-byte key\n", timer);
+  begin(); for (n=0; n <    5; ++n) { build(20000000,0,0,1);      } end(); printf("  // %7.2fms : 20,000,000 inserts creating 20M table w/ 4-byte key\n", timer);
+
+  begin(); for (n=0; n <   60; ++n) { churn_skip(2000,2100,5000);            } end(); printf("  // %7.2fms : 500,000 inserts & deletes in 2K table\n", timer);
+  begin(); for (n=0; n <   30; ++n) { churn_skip(20000,21000,500);           } end(); printf("  // %7.2fms : 500,000 inserts & deletes in 20K table\n", timer);
+  begin(); for (n=0; n <   15; ++n) { churn_skip(200000,201000,500);         } end(); printf("  // %7.2fms : 500,000 inserts & deletes in 200K table\n", timer);
+  begin(); for (n=0; n <    8; ++n) { churn_skip(2000000,2001000,500);       } end(); printf("  // %7.2fms : 500,000 inserts & deletes in 2M table\n", timer);
+  begin(); for (n=0; n <    5; ++n) { churn_skip(20000000,20001000,500);     } end(); printf("  // %7.2fms : 500,000 inserts & deletes in 20M table\n", timer);
+  begin(); for (n=0; n <    1; ++n) { churn_skip(200000000u,200001000u,500); } end(); printf("  // %7.2fms : 500,000 inserts & deletes in 200M table\n", timer);
+  // even though the above measures a roughly fixed amount of work, we still have to build the table n times, hence the fewer measurements each time
+
+  begin(); for (n=0; n <   60; ++n) { churn_skip(1000,3000,250);             } end(); printf("  // %7.2fms :    500,000 inserts & deletes in 2K table\n", timer);
+  begin(); for (n=0; n <   15; ++n) { churn_skip(10000,30000,25);            } end(); printf("  // %7.2fms :    500,000 inserts & deletes in 20K table\n", timer);
+  begin(); for (n=0; n <    7; ++n) { churn_skip(100000,300000,10);          } end(); printf("  // %7.2fms :  2,000,000 inserts & deletes in 200K table\n", timer);
+  begin(); for (n=0; n <    2; ++n) { churn_skip(1000000,3000000,10);        } end(); printf("  // %7.2fms : 20,000,000 inserts & deletes in 2M table\n", timer);
+
+  // search for bad intervals.. in practice this just seems to measure execution variance
+  for (s = 2; s < 64; ++s) {
+    begin(); for (n=0; n < 50; ++n) { build(200000,0,0,s); } end();
+    if (timer > worst) {
+      worst = timer;
+      w = s;
+    }
+  }
+  for (; s <= 1024; s *= 2) {
+    begin(); for (n=0; n < 50; ++n) { build(200000,0,0,s); } end();
+    if (timer > worst) {
+      worst = timer;
+      w = s;
+    }
+  }
+  printf("  // %7.2fms(%d)   : Worst time from inserting 200,000 items with spacing %d.\n", worst, w, w);
+
+  return 0;
+}
+#endif

tests/test_siphash.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+#define STB_DS_IMPLEMENTATION
+#define STBDS_SIPHASH_2_4
+#define STBDS_TEST_SIPHASH_2_4
+#include "../stb_ds.h"
+
+int main(int argc, char **argv)
+{
+  unsigned char mem[64];
+  int i,j;
+  for (i=0; i < 64; ++i) mem[i] = i;
+  for (i=0; i < 64; ++i) {
+    size_t hash = stbds_hash_bytes(mem, i, 0);
+    printf("  { ");
+    for (j=0; j < 8; ++j)
+      printf("0x%02x, ", (unsigned char) ((hash >> (j*8)) & 255));
+    printf(" },\n");
+  }
+  return 0;
+}