fix #1 use merge sort instead

jni/shadowsocks/encrypt.c

@@ -3,10 +3,124 @@
 
 #include <openssl/md5.h>
 
+typedef unsigned char uint8_t;
+typedef unsigned int uint32_t;
+typedef unsigned long long uint64_t;
+
+static int random_compare(const void *_x, const void *_y) {
+    uint32_t i = _i;
+    uint64_t a = _a;
+    uint8_t x = *((uint8_t *) _x);
+    uint8_t y = *((uint8_t*) _y);
+    return (a % (x + i) - a % (y + i));
+}
+
+
+static void merge(uint8_t *left, int llength, uint8_t *right, int rlength)
+{
+	/* Temporary memory locations for the 2 segments of the array to merge. */
+	uint8_t *ltmp = (uint8_t *) malloc(llength * sizeof(uint8_t));
+	uint8_t *rtmp = (uint8_t *) malloc(rlength * sizeof(uint8_t));
+
+	/*
+	 * Pointers to the elements being sorted in the temporary memory locations.
+	 */
+	uint8_t *ll = ltmp;
+	uint8_t *rr = rtmp;
+
+	uint8_t *result = left;
+
+	/*
+	 * Copy the segment of the array to be merged into the temporary memory
+	 * locations.
+	 */
+	memcpy(ltmp, left, llength * sizeof(uint8_t));
+	memcpy(rtmp, right, rlength * sizeof(uint8_t));
+
+	while (llength > 0 && rlength > 0) {
+		if (random_compare(ll, rr) <= 0) {
+			/*
+			 * Merge the first element from the left back into the main array
+			 * if it is smaller or equal to the one on the right.
+			 */
+			*result = *ll;
+			++ll;
+			--llength;
+		} else {
+			/*
+			 * Merge the first element from the right back into the main array
+			 * if it is smaller than the one on the left.
+			 */
+			*result = *rr;
+			++rr;
+			--rlength;
+		}
+		++result;
+	}
+	/*
+	 * All the elements from either the left or the right temporary array
+	 * segment have been merged back into the main array.  Append the remaining
+	 * elements from the other temporary array back into the main array.
+	 */
+	if (llength > 0)
+		while (llength > 0) {
+			/* Appending the rest of the left temporary array. */
+			*result = *ll;
+			++result;
+			++ll;
+			--llength;
+		}
+	else
+		while (rlength > 0) {
+			/* Appending the rest of the right temporary array. */
+			*result = *rr;
+			++result;
+			++rr;
+			--rlength;
+		}
+
+	/* Release the memory used for the temporary arrays. */
+	free(ltmp);
+	free(rtmp);
+}
+
+static void mergesort(uint8_t array[], int length)
+{
+	/* This is the middle index and also the length of the right array. */
+	uint8_t middle;
+
+	/*
+	 * Pointers to the beginning of the left and right segment of the array
+	 * to be merged.
+	 */
+	uint8_t *left, *right;
+
+	/* Length of the left segment of the array to be merged. */
+	int llength;
+
+	if (length <= 1)
+		return;
+
+	/* Let integer division truncate the value. */
+	middle = length / 2;
+
+	llength = length - middle;
+
+	/*
+	 * Set the pointers to the appropriate segments of the array to be merged.
+	 */
+	left = array;
+	right = array + llength;
+
+	mergesort(left, llength);
+	mergesort(right, middle);
+	merge(left, llength, right, middle);
+}
+
 void encrypt(char *buf, int len) {
     char *end = buf + len;
     while (buf < end) {
-        *buf = (char)encrypt_table[(unsigned char)*buf];
+        *buf = (char)encrypt_table[(uint8_t)*buf];
         buf++;
     }
 }
@@ -14,7 +128,7 @@ void encrypt(char *buf, int len) {
 void decrypt(char *buf, int len) {
     char *end = buf + len;
     while (buf < end) {
-        *buf = (char)decrypt_table[(unsigned char)*buf];
+        *buf = (char)decrypt_table[(uint8_t)*buf];
         buf++;
     }
 }
@@ -34,27 +148,19 @@ int recv_decrypt(int sock, char *buf, int len, int flags) {
     return result;
 }
 
-static int random_compare(const void *_x, const void *_y) {
-    unsigned int i = _i;
-    unsigned long long a = _a;
-    unsigned char x = *((unsigned char*) _x);
-    unsigned char y = *((unsigned char*) _y);
-    return (a % (x + i) - a % (y + i));
-}
-
 void get_table(const char* key) {
-    unsigned char *table = encrypt_table;
-    unsigned char *tmp_hash;
-    tmp_hash = MD5((const unsigned char*)key, strlen(key), NULL);
-    _a = *(unsigned long long *)tmp_hash;
-    unsigned int i;
+    uint8_t *table = encrypt_table;
+    uint8_t *tmp_hash;
+    tmp_hash = MD5((const uint8_t*)key, strlen(key), NULL);
+    _a = *(uint64_t *)tmp_hash;
+    uint32_t i;
 
     for(i = 0; i < 256; ++i) {
         table[i] = i;
     }
     for(i = 1; i < 1024; ++i) {
         _i = i;
-        qsort(table, 256, sizeof(unsigned char), random_compare);
+        mergesort(table, 256);
     }
     for(i = 0; i < 256; ++i) {
         // gen decrypt table from encrypt table