Initial push

util.c

@@ -0,0 +1,55 @@
+#include "util.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+char *memstr(char *haystack, size_t n, string needle) {
+    char *end = haystack + n;
+
+    // Iterate through the memory (haystack)
+    while ((haystack = memchr(haystack, needle[0], end - haystack)) != NULL) {
+        if (strncmp(haystack, needle, strlen(needle)) == 0) {
+            return haystack;
+        }
+    }
+
+    return NULL;
+}
+
+uint16_t safe_strtoul(const char *restrict nptr, char **restrict endptr,
+                      int base, const string message) {
+    errno = 0;
+    uint16_t result =
+        strtoul(nptr, endptr, base); // Convert string to unsigned int
+
+    if (errno != 0) {
+        fprintf(stderr, "%s\n", message);
+        exit(EXIT_FAILURE);
+    }
+    return result;
+}
+
+
+uint16_t pseudo_hash(const unsigned char *buffer, size_t buf_len) {
+    // we use tcp crc16 check here
+    uint32_t hash = 0;
+    // add zero padding to the end if buf_len not even
+    size_t pad_length = buf_len % 2 ? buf_len + 1 : buf_len;
+    uint8_t *int_buffer =  calloc(pad_length, sizeof *buffer);
+    memcpy(int_buffer, buffer, buf_len);
+
+    for (size_t i = 0; i < pad_length; i+=2) {
+        hash += int_buffer[i] << 8 | int_buffer[i+1];
+    }
+
+    hash = (hash & 0xFFFF) + (hash >> 16);
+
+    free(int_buffer);
+
+    return (uint16_t) ~hash;
+}
+
+
+