c : add bit_array, bit_compose, malloc_hook

1 files changed, 105 insertions, 0 deletions

diff --git a/c/bit_array.c b/c/bit_array.c
new file mode 100644
index 0000000..26c05f6
--- /dev/null
+++ b/c/bit_array.c
@@ -0,0 +1,105 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+typedef uint32_t bitfield_t;
+enum { BITFIELD_BITS = sizeof(bitfield_t) * 8 };
+
+static inline int bindex(int b) { return b / BITFIELD_BITS; }
+static inline int boffset(int b) { return b % BITFIELD_BITS; }
+#define bptr(st) (&((st)->bits))
+
+struct _Bits
+{
+    uint32_t nw;
+    bitfield_t bits;
+};
+
+typedef struct _Bits * Bits;
+
+static inline Bits bits_alloc(int n)
+{
+    uint32_t nw = (n / BITFIELD_BITS);
+    if (nw * BITFIELD_BITS < n) nw += 1;
+    int sz = sizeof(int) + (nw * sizeof(bitfield_t));
+    /* printf("wants %d bits : alloc %d bytes (1 uint32_t[%lu]  + %d bitfields[%lu])\n", n, sz, sizeof(uint32_t), nw, (nw * sizeof(bitfield_t))); */
+    Bits b = calloc(1, sz);
+    /* memset(b, 0, sz); */
+    b->nw = nw;
+    return b;
+}
+
+static inline void bits_free(Bits bits)
+{
+    free(bits);
+}
+
+static inline void set_bit(Bits bits, int b)
+{
+    bptr(bits)[bindex(b)] |= (bitfield_t)(1 << boffset(b));
+}
+
+static inline void reset_bit(Bits bits, int b)
+{
+    bptr(bits)[bindex(b)] &= ~(1 << boffset(b));
+}
+
+static inline int get_bit(Bits bits, int b)
+{
+    int of = boffset(b);
+    return (bptr(bits)[bindex(b)] & (1 << of)) >> of;
+}
+
+static inline Bits bits_copy(Bits dst, Bits src)
+{
+    if (dst->nw != src->nw) return 0;
+    return memcpy(&dst->bits, &src->bits, (sizeof(bitfield_t) * src->nw));
+}
+
+static void assert(int value, int expected, char*msg)
+{
+    if (value != expected) {
+        fprintf(stderr, "Error %s\n", msg);
+        exit(1);
+    }
+}
+
+int main(int argc, char **argv, char **env)
+{
+    printf("bits in an bitfield_t : %d\n", BITFIELD_BITS);
+    Bits a = bits_alloc(33);
+    Bits b = bits_alloc(33);
+    set_bit(a, 31);
+    set_bit(a, 32);
+    set_bit(a, 33);
+    assert(get_bit(a, 30), 0, "bit 30 is not 0");
+    assert(get_bit(a, 31), 1, "bit 31 is not 1");
+    assert(get_bit(a, 32), 1, "bit 32 is not 1");
+    assert(get_bit(a, 33), 1, "bit 33 is not 1");
+    assert(get_bit(a, 34), 0, "bit 34 is not 0");
+    reset_bit(a, 32);
+    assert(get_bit(a, 30), 0, "bit 30 is not 0");
+    assert(get_bit(a, 31), 1, "bit 31 is not 1");
+    assert(get_bit(a, 32), 0, "bit 32 is not 0");
+    assert(get_bit(a, 33), 1, "bit 33 is not 1");
+    assert(get_bit(a, 34), 0, "bit 34 is not 0");
+    set_bit(a, 32);
+    reset_bit(a, 33);
+    reset_bit(a, 31);
+    assert(get_bit(a, 30), 0, "bit 30 is not 0");
+    assert(get_bit(a, 31), 0, "bit 31 is not 0");
+    assert(get_bit(a, 32), 1, "bit 32 is not 1");
+    assert(get_bit(a, 33), 0, "bit 33 is not 0");
+    assert(get_bit(a, 34), 0, "bit 34 is not 0");
+    bits_copy(b, a);
+    assert(get_bit(b, 30), 0, "bit 30 is not 0");
+    assert(get_bit(b, 31), 0, "bit 31 is not 0");
+    assert(get_bit(b, 32), 1, "bit 32 is not 1");
+    assert(get_bit(b, 33), 0, "bit 33 is not 0");
+    assert(get_bit(b, 34), 0, "bit 34 is not 0");
+    bits_free(a);
+    bits_free(b);
+    printf("Success\n");
+    return 0;
+}