Added generic hashmaps and 2 examples using them

examples/hm_basic.c

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#define LAZY_IMPL
+#include "../lazy.h"
+
+void printHmIdx(void *hm, int k) {
+  typedef Lz_HM(int,int) HM;
+  HM map = *(HM*)hm;
+  if (lz_hm_exists(map,k)) {
+    printf("hm[%d] = %d\n", k, lz_hm_get(map,k));
+  } else {
+    printf("hm[%d] = <N/A>\n", k);
+  }
+}
+
+int main() {
+  Lz_HM(int, int) hm;
+  lz_hm_init(hm);
+
+  lz_hm_add(hm, 1, 2);
+  lz_hm_add(hm, 2, 4);
+
+  printf("Hello World!\n");
+  printHmIdx(&hm, 1);
+  printHmIdx(&hm, 3);
+}

examples/hm_findsumpair.c

@@ -0,0 +1,33 @@
+#include <stdio.h>
+#define LAZY_IMPL
+#include "../lazy.h"
+
+// This is some CS problem I heard of
+// You need to find any two indecies in the array which add to k
+// Hashmaps are the main way to solve this better than O(n^2)
+int main() {
+  int vals[] = {7, 12, 25, 30, 43, 60, 1000, 50, 38, 62, 50};
+  int N = sizeof(vals)/sizeof(vals[0]);
+  int K = 100;
+
+  Lz_HM(int,size_t) LUT;
+  lz_hm_init(LUT);
+
+  for (size_t i = 0; i < N; ++i) {
+    lz_hm_add(LUT, vals[i], i);
+  }
+
+  for (size_t i = 0; i < N; ++i) {
+    int v = vals[i];
+    int other = K-v;
+    if (lz_hm_exists(LUT, other)) {
+      size_t otherIdx = lz_hm_get(LUT, other);
+      if (otherIdx == i) continue;
+      printf("Found pair: idx: %zu, %zu, vals %d, %d\n",
+             i, otherIdx,
+             v, other);
+      break;
+    }
+  }
+  return 0;
+}

lazy.h

@@ -2,6 +2,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <assert.h>
+#include <stdint.h>
 
 #define LZ_STR_FMT "%.*s"
 #define LZ_STR_PRINTF(slc) (int)slc.cnt, slc.data
@@ -18,6 +19,10 @@ void lz_drop_left(Lz_Slc *src, size_t n);
 void lz_drop_right(Lz_Slc *src, size_t n);
 void lz_split_slc(Lz_Slc *src, char delim, Lz_Slc *dst);
 void lz_split_slc_typ(Lz_Slc *src, int (*classfunc)(int), Lz_Slc *dst);
+size_t lz_hm_hash_void_set(void *hmdat, size_t e_size, size_t cap,
+                           void *key, size_t k_size);
+size_t lz_hm_hash_void_get(void *hmdat, size_t e_size, size_t cap,
+                           void *key, size_t k_size);
 Lz_Slc lz_cstr_to_slc(char *dat);
 char *lz_cstr_dup(const char *s);
 
@@ -85,8 +90,109 @@ char *lz_cstr_dup(const char *s);
 
 typedef Lz_DA(char) Lz_SB;
 
+#define Lz_HM_Pair(K_t, V_t) struct {\
+  size_t exists;\
+  K_t key;\
+  V_t val;\
+}
+
+#define Lz_HM(K_t, V_t) struct {\
+  size_t cap;\
+  size_t cnt;\
+  size_t valsize;\
+  size_t entrysize;\
+  size_t tmphash;\
+  V_t defval;\
+  K_t tmpkey;\
+  V_t tmpval;\
+  Lz_HM_Pair(K_t, V_t) *data;\
+}
+
+#define lz_hm_init(hm) do {\
+  (hm).cap = 256;\
+  (hm).cnt = 0;\
+  (hm).valsize = sizeof((*(hm).data).val);\
+  (hm).entrysize = sizeof(*(hm).data);\
+  (hm).data = malloc((hm).cap*(hm).entrysize);\
+} while (0)
+
+
+#define lz_hm_hash_set(hm, k) (\
+  (hm).tmpkey = k,\
+  lz_hm_hash_void_set((hm).data, (hm).entrysize,(hm.cap),\
+                  &(hm).tmpkey, sizeof((hm).tmpkey))\
+)
+#define lz_hm_hash_get(hm, k) (\
+  (hm).tmpkey = k,\
+  lz_hm_hash_void_get((hm).data, (hm).entrysize,(hm.cap),\
+                  &(hm).tmpkey, sizeof((hm).tmpkey))\
+)
+
+#define lz_hm_exists(hm, k) (\
+  (hm).tmphash = lz_hm_hash_get(hm, k),\
+  ((hm).tmphash != (size_t)-1)\
+)
+
+#define lz_hm_get(hm, k) (\
+  (hm).tmphash = lz_hm_hash_get(hm, k),\
+  ((hm).tmphash == (size_t)-1) ? (hm).defval : ((hm).data[(hm).tmphash].val)\
+)
+
+#define lz_hm_add(hm, k, v) do {\
+  size_t idx = lz_hm_hash_set(hm, k);\
+  (hm).data[idx].key = k;\
+  (hm).data[idx].val = v;\
+} while(0)
+
 #ifdef LAZY_IMPL
 
+size_t lz_hm_hash_void_get(void *hmdat, size_t e_size, size_t cap,
+                       void *key, size_t k_size) {
+  size_t hash = 0;
+  for (size_t i = 0; i < k_size; ++i) {
+    size_t b = (size_t)(((uint8_t*)key)[i]);
+    hash += b*31415 + 9265; //bytewise hash
+    hash %= cap;
+  }
+
+  for (size_t i = 0; i < cap; ++i) {
+    size_t localhash = (hash + i) % cap;
+    size_t structOffset = e_size*localhash;
+    void *pairStruct = (hmdat + structOffset);
+    void *structKey = pairStruct + sizeof(size_t);
+    int diff = memcmp(structKey, key, k_size);
+    if (diff == 0) {
+      return localhash;
+    }
+    
+    size_t istaken = *((size_t*)pairStruct);
+    if (!istaken) {
+      return (size_t)-1;
+    }
+  }
+  assert(0 && "Overflown Hashmap");
+  return 0;
+}
+
+size_t lz_hm_hash_void_set(void *hmdat, size_t e_size, size_t cap,
+                       void *key, size_t k_size) {
+  size_t hash = 0;
+  for (size_t i = 0; i < k_size; ++i) {
+    size_t b = (size_t)(((uint8_t*)key)[i]);
+    hash += b*31415 + 9265; //bytewise hash
+    hash %= cap;
+  }
+
+  for (size_t i = 0; i < cap; ++i) {
+    size_t localhash = (hash + i) % cap;
+    size_t structOffset = e_size*localhash;
+    void *pairStruct = (hmdat + structOffset);
+    size_t istaken = *((size_t*)pairStruct);
+    if (!istaken) return localhash;
+  }
+  return (size_t)-1;
+}
+
 // Horribly enough, strdup is a gnu extension
 // Here's a portable implementation
 char *lz_cstr_dup(const char *s) {