From 89a3585c7f3a1a5d10e036050111255e21856058 Mon Sep 17 00:00:00 2001
From: Evan Burkey <evan@burkey.co>
Date: Sun, 5 May 2024 17:05:12 -0700
Subject: [PATCH] add hamming_distance

---
 docs/crypto.md     | 10 +++++++++-
 include/lfcrypto.h |  3 ++-
 src/crypto.c       |  6 +++++-
 tests/tests.c      |  7 ++++++-
 4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/docs/crypto.md b/docs/crypto.md
index d993427..e3833e9 100644
--- a/docs/crypto.md
+++ b/docs/crypto.md
@@ -92,8 +92,16 @@ const unsigned char *repeating_key_xor_s(const char* s, const char* key);
 
 ### hamming_distance
 
+Calculates the Hamming Distance (the number of differing bits) between two arrays of unsigned bytes
+
+```c
+unsigned int hamming_distance(unsigned char *a, unsigned char *b);
+```
+
+### hamming_distance_s
+
 Calculates the Hamming Distance (the number of differing bits) between two strings
 
 ```c
-unsigned int hamming_distance(const char *a, const char *b);
+unsigned int hamming_distance_s(const char *a, const char *b);
 ```
diff --git a/include/lfcrypto.h b/include/lfcrypto.h
index 7492841..29c64bd 100644
--- a/include/lfcrypto.h
+++ b/include/lfcrypto.h
@@ -13,6 +13,7 @@ const char *hex_to_str(const unsigned char *hex, size_t sz);
 const unsigned char* repeating_key_xor(const unsigned char* s, size_t s_sz, const unsigned char* key, size_t k_sz);
 const unsigned char *repeating_key_xor_s(const char* s, const char* key);
 
-unsigned int hamming_distance(const char *a, const char *b);
+unsigned int hamming_distance_s(const char *a, const char *b);
+unsigned int hamming_distance(unsigned char *a, unsigned char *b, size_t sz);
 
 #endif // LIBFLINT_CRYPTO_H
diff --git a/src/crypto.c b/src/crypto.c
index ac04bdf..d0cfea9 100644
--- a/src/crypto.c
+++ b/src/crypto.c
@@ -272,12 +272,16 @@ const unsigned char *repeating_key_xor_s(const char* s, const char* key) {
     return repeating_key_xor((unsigned char*)s, strlen(s), (unsigned char*)key, strlen(key));
 }
 
-unsigned int hamming_distance(const char *a, const char *b) {
+unsigned int hamming_distance_s(const char *a, const char *b) {
     size_t sz = strlen(a);
     if (sz != strlen(b)) {
         return -1;
     }
 
+    return hamming_distance((unsigned char *)a, (unsigned char *)b, sz);
+}
+
+unsigned int hamming_distance(unsigned char *a, unsigned char *b, size_t sz) {
     unsigned int hamming = 0;
     for (size_t i = 0; i < sz; ++i) {
         if (a[i] == b[i]) {
diff --git a/tests/tests.c b/tests/tests.c
index e8d4ddf..541550e 100644
--- a/tests/tests.c
+++ b/tests/tests.c
@@ -374,7 +374,12 @@ void test_crypto() {
     free(enc);
     free(s);
 
-    unsigned int hamming = hamming_distance("this is a test", "wokka wokka!!!");
+    unsigned char ua[2] = { 0x2, 0xF };
+    unsigned char ub[2] = { 0x4, 0xE };
+    unsigned int hamming = hamming_distance(ua, ub, 2);
+    assert(hamming == 3);
+
+    hamming = hamming_distance_s("this is a test", "wokka wokka!!!");
     assert(hamming == 37);
 
     printf("Passes all crypto tests\n");