'

malloc/src/helpers/helpers.c

@@ -1,4 +1,61 @@
 #include "helpers.h"
 
-size_t get_next_2power(size_t n)
+#include <sys/mman.h>
-{}
+
+// Returns the smallest power of 2 greater or equal to s
+size_t s2p(size_t s)
+{
+    // Trick I found on the internet but I don't completely understand it
+    // Quite amazing
+    // n--;           // 1101 1101 --> 1101 1100
+    // n |= n >> 1;   // 1101 1100 | 0110 1110 = 1111 1110
+    // n |= n >> 2;   // 1111 1110 | 0011 1111 = 1111 1111
+    // n |= n >> 4;   // ...
+    // n |= n >> 8;
+    // n |= n >> 16;  // 1111 1111 | 1111 1111 = 1111 1111
+    // n++;           // 1111 1111 --> 1 0000 0000
+
+    // There is also an x86 assembly instruction to do that in a single cycle:
+    // lzcnt
+    // Yeah... This one is definetely wild intel
+    // Now since asm{} is prohibited in the coding style it won't be useful
+    // Or maybe there is a builtin to do that ?
+    // (found __builtin_clzll but not sure of what it does)
+
+    // So here's the good old way
+    size_t n = 1;
+    while (n < s)
+    {
+        n <<= 1;
+    }
+
+    return n;
+}
+
+void *find_free_block(struct bucket *buck)
+{
+    unsigned maplength = buck->block_size / 8;
+    // for each block
+    for (unsigned i = 0; i < maplength; i++)
+    {
+        unsigned char map_byte = buck->free_list[i];
+        unsigned char bit = 1;
+        // Test byte
+        for (unsigned j = 0; j < 8; j <<= 1)
+        {
+            if (map_byte & bit) // Test if free
+                return buck->page + (buck->block_size * (i * 8 + j));
+
+            bit <<= 1;
+        }
+    }
+
+    return NULL;
+}
+
+struct bucket *create_bucket(size_t min_alloc_size)
+{
+    size_t alloc_size = s2p(min_alloc_size);
+    void *page =
+        mmap(NULL, alloc_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, -1, 0);
+}

malloc/src/helpers/helpers.h

@@ -3,6 +3,16 @@
 
 #include <stddef.h>
 
+struct bucket
+{
+    unsigned block_size;
+    unsigned char free_list[64]; // 4096 / MIN_BLOCK_SIZE /
+                                 // sizeof(unsigned char) (in bits)
+    char *page;
+};
+
 size_t get_next_2power(size_t n);
+void *find_free_block(struct bucket *buck);
+struct bucket *create_bucket(size_t min_alloc_size);
 
 #endif // ! HELPERS_H