c: Implement the C implementation of the bhash module

c/bhash/inc/bhash.h

@@ -0,0 +1,46 @@
+#ifndef BHASH_H_INCLUDED
+#define BHASH_H_INCLUDED
+
+#include <stdint.h>
+
+#define BHASH_MOD32_ERR UINT32_MAX
+
+typedef struct bhash bhash_t;
+
+struct bhash
+{
+    uint8_t    *bh_data;            /* Current data buffer */
+    size_t      bh_len;             /* Data length */
+    double      bh_bits_avail;      /* Bits available */
+    double      bh_bits_used;       /* Bits used */
+};
+
+/*
+ * Initialize new instance of Bhash
+ */
+void bhash_init(bhash_t *bh, const void *data, size_t data_len);
+
+/*
+ * Destroy a bhash object and its associated data
+ */
+void bhash_fini(bhash_t *bh);
+
+/*
+ * Perform a divison of the whole bhash data using the 32-bit `mod` variable
+ * and return the 32-bit reminder.
+ *
+ * This function returns BHASH_MOD32_ERR on error.
+ */
+uint32_t bhash_mod32(bhash_t *bh, uint32_t mod);
+
+/*
+ * Return the number of total bits available in hash
+ */
+double bhash_bits_avail(bhash_t *bh);
+
+/*
+ * Return the number of bits used in bhash
+ */
+double bhash_bits_used(bhash_t *bh);
+
+#endif /* BHASH_H_INCLUDED */

c/bhash/meson.build

@@ -0,0 +1,12 @@
+
+cc = meson.get_compiler('c')
+
+bhash_inc = include_directories('inc')
+
+bhash_lib = static_library(
+        'bhash',
+        ['src/bhash.c'],
+        include_directories : bhash_inc,
+        dependencies: [ cc.find_library('m', required: false) ])
+
+bhash_dep = declare_dependency(link_with : bhash_lib, include_directories : bhash_inc)

c/bhash/src/bhash.c

@@ -0,0 +1,67 @@
+#include <arpa/inet.h> /* For htonl() */
+
+#include <math.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "bhash.h"
+
+void bhash_init(bhash_t *bh, const void *data, size_t data_len)
+{
+    memset(bh, 0, sizeof(*bh));
+
+    bh->bh_data = malloc(data_len);
+    memcpy(bh->bh_data, data, data_len);
+    bh->bh_len = data_len;
+
+    bh->bh_bits_avail = data_len * 8.0;
+}
+
+void bhash_fini(bhash_t *bh)
+{
+    free(bh->bh_data);
+}
+
+uint32_t bhash_mod32(bhash_t *bh, uint32_t mod)
+{
+    uint32_t *pi;
+    uint32_t *pend;
+    uint64_t n;
+
+    uint32_t rv = 0;
+
+    if ((bh->bh_len % sizeof(uint32_t)) != 0)
+    {
+        return BHASH_MOD32_ERR;
+    }
+
+    pend = (uint32_t *)(bh->bh_data + bh->bh_len);
+
+    for (pi = (uint32_t *)bh->bh_data; pi < pend; pi++)
+    {
+        n = (uint64_t)rv << (sizeof(uint32_t) * 8);
+        n |= htonl(*pi);
+
+        *pi = ntohl(n / mod);
+        rv = n % mod;
+    }
+
+    bh->bh_bits_used += log(mod) / log(2);
+    if (bh->bh_bits_used > bh->bh_bits_avail)
+    {
+        return BHASH_MOD32_ERR;
+    }
+
+    return rv;
+}
+
+double bhash_bits_avail(bhash_t *bh)
+{
+    return bh->bh_bits_avail;
+}
+double bhash_bits_used(bhash_t *bh)
+{
+    return bh->bh_bits_used;
+}
+