Added hash function computation compatible with openssl 3.0

dircomp.c

@@ -355,6 +355,54 @@ unsigned char* sha1(char *filename)
     return hash;
 }
 
+unsigned char* sha1_openssl3(char *filename){
+    EVP_MD_CTX *mdctx; // envelope context
+    const EVP_MD *md; // envelope mode (SHA1)
+    unsigned char *hash = malloc(EVP_MAX_MD_SIZE * sizeof(unsigned char)); // result will be here
+    unsigned int digest_len, i;
+
+    FILE *f = fopen(filename, "rb");
+    if (f == NULL)
+    {
+        fprintf(stderr, "Couldn't open %s\n", filename);
+        return NULL;
+    }
+
+    mdctx = EVP_MD_CTX_new();
+    if (mdctx == NULL) {
+        return NULL;
+    }
+    md = EVP_sha1();
+    if (!EVP_DigestInit_ex(mdctx, md, NULL)) {
+        return NULL;
+    }
+
+    #define BYTES_TO_READ_AT_ONCE 512000    // 500KiB
+    unsigned int bytes;                 // how many bytes we have actually read from fread
+    #if BYTES_TO_READ_AT_ONCE > UINT_MAX
+    #error Trying to read more bytes than what is possible to handle. Recompile using unsigned long or reduce BYTES_TO_READ_AT_ONCE
+    #endif
+    unsigned char databuffer[BYTES_TO_READ_AT_ONCE];
+    while ((bytes = fread(databuffer, 1, BYTES_TO_READ_AT_ONCE, f)) != 0)
+    {
+        if (!EVP_DigestUpdate(mdctx, databuffer, bytes)) {
+            return NULL;
+        }
+    }
+
+    if (!EVP_DigestFinal_ex(mdctx, hash, &digest_len)) {
+        return NULL;
+    }
+    EVP_MD_CTX_free(mdctx);
+    // print the result in hexadecimal format
+    for (i = 0; i < digest_len; i++) {
+        printf("%02x", hash[i]);
+    }
+
+    fclose(f);
+    return hash;
+}
+
 /// @brief Combines two paths
 /// @param path1
 /// @param path2