diff --git a/README.md b/README.md
index e87c8bc..b060266 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ much faster than ``rclone mount``.
 
 ## Usage
 
-	./httpdirfs -f --cache -f $URL $YOUR_MOUNT_POINT
+	./httpdirfs -f --cache $URL $YOUR_MOUNT_POINT
 
 An example URL would be
 [Debian CD Image Server](https://cdimage.debian.org/debian-cd/). The ``-f`` flag
diff --git a/src/README.md b/src/README.md
new file mode 100644
index 0000000..fa89bde
--- /dev/null
+++ b/src/README.md
@@ -0,0 +1,5 @@
+## Coding Convention
+- External variables: capital letters
+- Static global variables: lower case letters
+- Function names: TypeName_verb or verb_noun
+- Type names: camel case with the first letter capitalised, e.g. CamelCase
diff --git a/src/cache.c b/src/cache.c
index 502c22c..baff2ec 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -211,11 +211,8 @@ blksz: %d, segbc: %ld\n", cf->path, cf->content_length, cf->blksz, cf->segbc);
         fprintf(stderr, "Meta_read(): Error: segbc: %ld\n", cf->segbc);
         return EMEM;
     }
-    cf->seg = calloc(cf->segbc, sizeof(Seg));
-    if (!cf->seg) {
-        fprintf(stderr, "Meta_read(): calloc failure: %s\n", strerror(errno));
-        return EMEM;
-    }
+    cf->seg = CALLOC(cf->segbc, sizeof(Seg));
+
     /* Read all the segment */
     nmemb = fread(cf->seg, sizeof(Seg), cf->segbc, fp);
 
@@ -474,11 +471,7 @@ int CacheDir_create(const char *dirn)
  */
 static Cache *Cache_alloc()
 {
-    Cache *cf = calloc(1, sizeof(Cache));
-    if (!cf) {
-        fprintf(stderr, "Cache_new(): calloc failure!\n");
-        exit_failure();
-    }
+    Cache *cf = CALLOC(1, sizeof(Cache));
 
     if (pthread_mutex_init(&cf->seek_lock, NULL)) {
         fprintf(stderr, "Cache_alloc(): seek_lock initialisation failed!\n");
@@ -680,12 +673,7 @@ int Cache_create(Link *this_link)
     cf->content_length = this_link->content_length;
     cf->blksz = DATA_BLK_SZ;
     cf->segbc = (cf->content_length / cf->blksz) + 1;
-    cf->seg = calloc(cf->segbc, sizeof(Seg));
-
-    if (!cf->seg) {
-        fprintf(stderr, "Cache_create(): cf->seg calloc failure!\n");
-        exit_failure();
-    }
+    cf->seg = CALLOC(cf->segbc, sizeof(Seg));
 
     if (Meta_create(cf)) {
         fprintf(stderr, "Cache_create(): cannot create metadata.\n");
@@ -914,7 +902,7 @@ static void *Cache_bgdl(void *arg)
             pthread_self());
     #endif
     PTHREAD_MUTEX_LOCK(&cf->w_lock);
-    uint8_t *recv_buf = calloc(cf->blksz, sizeof(uint8_t));
+    uint8_t *recv_buf = CALLOC(cf->blksz, sizeof(uint8_t));
     fprintf(stderr, "Cache_bgdl(): thread %lu: ", pthread_self());
     long recv = path_download(cf->path, (char *) recv_buf, cf->blksz,
                               cf->next_dl_offset);
@@ -976,7 +964,7 @@ long Cache_read(Cache *cf,  char * const output_buf, const off_t len,
 
     /* ------------------------Download the segment -------------------------*/
 
-    uint8_t *recv_buf = calloc(cf->blksz, sizeof(uint8_t));
+    uint8_t *recv_buf = CALLOC(cf->blksz, sizeof(uint8_t));
     fprintf(stderr, "Cache_read(): thread %lu: ", pthread_self());
     long recv = path_download(cf->path, (char *) recv_buf, cf->blksz,
                                 dl_offset);
diff --git a/src/link.c b/src/link.c
index c7e4f6c..bf29513 100644
--- a/src/link.c
+++ b/src/link.c
@@ -48,11 +48,8 @@ static void LinkTable_add(LinkTable *linktbl, Link *link)
 
 static Link *Link_new(const char *linkname, LinkType type)
 {
-    Link *link = calloc(1, sizeof(Link));
-    if (!link) {
-        fprintf(stderr, "Link_new(): calloc failure!\n");
-        exit_failure();
-    }
+    Link *link = CALLOC(1, sizeof(Link));
+
     strncpy(link->linkname, linkname, MAX_FILENAME_LEN);
     link->type = type;
 
@@ -172,11 +169,8 @@ void Link_req_file_stat(Link *this_link)
      *
      * It gets freed in curl_multi_perform_once();
      */
-    TransferStruct *transfer = calloc(1, sizeof(TransferStruct));
-    if (!transfer) {
-        fprintf(stderr, "Link_get_size(): malloc failed!\n");
-        exit_failure();
-    }
+    TransferStruct *transfer = CALLOC(1, sizeof(TransferStruct));
+
     transfer->link = this_link;
     transfer->type = FILESTAT;
     curl_easy_setopt(curl, CURLOPT_PRIVATE, transfer);
@@ -326,11 +320,7 @@ LinkTable *LinkTable_new(const char *url)
             pthread_self());
     #endif
     PTHREAD_MUTEX_LOCK(&link_lock);
-    LinkTable *linktbl = calloc(1, sizeof(LinkTable));
-    if (!linktbl) {
-        fprintf(stderr, "LinkTable_new(): calloc failure!\n");
-        exit_failure();
-    }
+    LinkTable *linktbl = CALLOC(1, sizeof(LinkTable));
 
     /* populate the base URL */
     LinkTable_add(linktbl, Link_new("/", LINK_HEAD));
@@ -507,19 +497,12 @@ LinkTable *LinkTable_disk_open(const char *dirn)
         return NULL;
     }
 
-    LinkTable *linktbl = calloc(1, sizeof(LinkTable));
-    if (!linktbl) {
-        fprintf(stderr, "LinkTable_disk_open(): calloc linktbl failed!\n");
-        return NULL;
-    }
+    LinkTable *linktbl = CALLOC(1, sizeof(LinkTable));
 
     fread(&linktbl->num, sizeof(int), 1, fp);
-    linktbl->links = calloc(linktbl->num, sizeof(Link *));
+    linktbl->links = CALLOC(linktbl->num, sizeof(Link *));
     for (int i = 0; i < linktbl->num; i++) {
-        linktbl->links[i] = calloc(1, sizeof(Link));
-        if (!linktbl->links[i]) {
-            fprintf(stderr, "LinkTable_disk_open(): calloc links[i] failed!\n");
-        }
+        linktbl->links[i] = CALLOC(1, sizeof(Link));
         fread(linktbl->links[i]->linkname, sizeof(char), MAX_FILENAME_LEN, fp);
         fread(linktbl->links[i]->f_url, sizeof(char), MAX_PATH_LEN, fp);
         fread(&linktbl->links[i]->type, sizeof(LinkType), 1, fp);
diff --git a/src/link.h b/src/link.h
index 0d2dd7d..a47523b 100644
--- a/src/link.h
+++ b/src/link.h
@@ -50,6 +50,11 @@ struct Link {
     int cache_opened;
     /** \brief The pointer associated with the cache file */
     Cache *cache_ptr;
+    /**
+     * \brief Subsonic Music Directory ID
+     * \details We use linkname to store filename
+     */
+    int sonic_id;
 };
 
 struct LinkTable {
diff --git a/src/main.c b/src/main.c
index e8843ec..2adcba4 100644
--- a/src/main.c
+++ b/src/main.c
@@ -241,7 +241,7 @@ static void print_help(char *program_name, int long_help)
 static void print_version()
 {
     fprintf(stderr,
-            "HTTPDirFS version %s\n", VERSION);
+            "HTTPDirFS version " VERSION "\n");
 }
 
 static void print_long_help()
diff --git a/src/network.c b/src/network.c
index 407c0ac..0f6f8fe 100644
--- a/src/network.c
+++ b/src/network.c
@@ -239,7 +239,7 @@ void network_config_init()
     NETWORK_CONFIG.proxy_user = NULL;
     NETWORK_CONFIG.proxy_pass = NULL;
     NETWORK_CONFIG.max_conns = DEFAULT_NETWORK_MAX_CONNS;
-    NETWORK_CONFIG.user_agent = "HTTPDirFS";
+    NETWORK_CONFIG.user_agent = DEFAULT_USER_AGENT;
     NETWORK_CONFIG.cache_enabled = 0;
     NETWORK_CONFIG.cache_dir = NULL;
 }
diff --git a/src/network.h b/src/network.h
index d6d6f4c..5be2039 100644
--- a/src/network.h
+++ b/src/network.h
@@ -8,6 +8,11 @@
 
 #include "link.h"
 
+/**
+ * \brief the default user agent string
+ */
+#define DEFAULT_USER_AGENT "HTTPDirFS-" VERSION
+
 typedef enum {
     FILESTAT = 's',
     DATA = 'd'
diff --git a/src/sonic.c b/src/sonic.c
index 91815a8..4c6013b 100644
--- a/src/sonic.c
+++ b/src/sonic.c
@@ -1,48 +1,96 @@
-#include "util.h"
+#include "sonic.h"
+
+#include "util.h"
+#include "network.h"
+
 
-#include <openssl/md5.h>
-#include <uuid/uuid.h>
 
 #include <string.h>
 #include <stdlib.h>
 
-#define MD5_HASH_LEN 32
-#define SALT_LEN 36
+typedef struct {
+    char *server;
+    char *username;
+    char *password;
+    char *client;
+    char *api_version;
+} SonicConfigStruct;
+
+static SonicConfigStruct SONIC_CONFIG;
+
 /**
- * \brief generate the salt for authentication string
- * \details this effectively generates a UUID string, which we use as the salt
- * \return a pointer to a 37-char array with the salt.
+ * \brief initalise Subsonic configuration struct
  */
-char *generate_salt()
+void sonic_config_init(const char *server, const char *username,
+                       const char *password)
 {
-    char *out;
-    out = calloc(SALT_LEN + 1, sizeof(char));
-    uuid_t uu;
-    uuid_generate(uu);
-    uuid_unparse(uu, out);
-    return out;
+    SONIC_CONFIG.server = strndup(server, MAX_PATH_LEN);
+    /* Correct for the extra '/' */
+    size_t server_url_len = strnlen(SONIC_CONFIG.server, MAX_PATH_LEN) - 1;
+    if (SONIC_CONFIG.server[server_url_len] == '/') {
+        SONIC_CONFIG.server[server_url_len] = '\0';
+    }
+    SONIC_CONFIG.username = strndup(username, MAX_FILENAME_LEN);
+    SONIC_CONFIG.password = strndup(password, MAX_FILENAME_LEN);
+    SONIC_CONFIG.client = DEFAULT_USER_AGENT;
+    /*
+     * API 1.13.0 is the minimum version that supports
+     * salt authentication scheme
+     */
+    SONIC_CONFIG.api_version = "1.13.0";
 }
 
 /**
- * \brief generate the md5sum of a string
- * \param[in] str a character array for the input string
- * \return a pointer to a 33-char array with the salt
+ * \brief generate authentication string
  */
-char *generate_md5sum(const char *str)
+static char *sonic_gen_auth_str()
 {
-    MD5_CTX c;
-    unsigned char md5[MD5_DIGEST_LENGTH];
-    size_t len = strnlen(str, MAX_PATH_LEN);
-    char *out = calloc(MD5_HASH_LEN + 1, sizeof(char));
+    char *salt = generate_salt();
+    size_t password_len = strnlen(SONIC_CONFIG.password, MAX_FILENAME_LEN);
+    size_t password_salt_len = password_len + strnlen(salt, MAX_FILENAME_LEN);
+    char *password_salt = CALLOC(password_salt_len + 1, sizeof(char));
+    strncat(password_salt, SONIC_CONFIG.password, MAX_FILENAME_LEN);
+    strncat(password_salt + password_len, salt, MAX_FILENAME_LEN);
+    char *token = generate_md5sum(password_salt);
+    char *auth_str = CALLOC(MAX_PATH_LEN + 1, sizeof(char));
+    snprintf(auth_str, MAX_PATH_LEN,
+                        ".view?u=%s&t=%s&s=%s&v=%s&c=%s",
+                        SONIC_CONFIG.username, token, salt,
+                        SONIC_CONFIG.api_version, SONIC_CONFIG.client);
+    free(salt);
+    free(token);
+    return auth_str;
+}
 
-    MD5_Init(&c);
-    MD5_Update(&c, str, len);
-    MD5_Final(md5, &c);
+/**
+ * \brief generate the first half of the request URL
+ */
+static char *sonic_gen_url_first_part(char *method)
+{
+    char *auth_str = sonic_gen_auth_str();
+    char *url = CALLOC(MAX_PATH_LEN + 1, sizeof(char));
+    snprintf(url, MAX_PATH_LEN, "%s/rest/%s%s", SONIC_CONFIG.server, method,
+             auth_str);
+    free(auth_str);
+    return url;
+}
 
-    for(int i = 0; i < MD5_DIGEST_LENGTH; i++) {
-        sprintf(out + 2 * i, "%02x", md5[i]);
+LinkTable *sonic_LinkTable_new(int id)
+{
+    char *url;
+    if (id > 0) {
+        char *first_part = sonic_gen_url_first_part("getMusicDirectory");
+        url = CALLOC(MAX_PATH_LEN + 1, sizeof(char));
+        snprintf(url, MAX_PATH_LEN, "%s&id=%d", first_part, id);
+        free(first_part);
+    } else {
+        url = sonic_gen_url_first_part("getIndexes");
     }
-    return out;
+
+    printf("%s\n", url);
+    LinkTable *linktbl = CALLOC(1, sizeof(LinkTable));
+
+    return NULL;
 }
 
 int main(int argc, char **argv)
@@ -50,8 +98,7 @@ int main(int argc, char **argv)
     (void) argc;
     (void) argv;
 
-    char *salt = generate_salt();
-    char *md5sum = generate_md5sum(salt);
-
-    printf("%s\n%s\n", salt, md5sum);
+    sonic_config_init(argv[1], argv[2], argv[3]);
+    sonic_LinkTable_new(0);
+    sonic_LinkTable_new(3);
 }
diff --git a/src/sonic.h b/src/sonic.h
index 546a530..b92bfc2 100644
--- a/src/sonic.h
+++ b/src/sonic.h
@@ -1,4 +1,15 @@
 #ifndef SONIC_H
 #define SONIC_H
+/**
+ * \file sonic.h
+ * \brief Subsonic related function
+ */
 
+#include "link.h"
+
+/**
+ * \brief Initialise SubSonic configuration.
+ */
+void sonic_config_init(const char *server, const char *username,
+                       const char *password);
 #endif
diff --git a/src/util.c b/src/util.c
index e65fd37..708b226 100644
--- a/src/util.c
+++ b/src/util.c
@@ -1,12 +1,17 @@
 #include "util.h"
 
+#include <openssl/md5.h>
+#include <uuid/uuid.h>
+
 #include <execinfo.h>
 #include <unistd.h>
-
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 
 #define BT_BUF_SIZE 100
+#define MD5_HASH_LEN 32
+#define SALT_LEN 36
 
 char *path_append(const char *path, const char *filename)
 {
@@ -18,11 +23,7 @@ char *path_append(const char *path, const char *filename)
     char *str;
     size_t ul = strnlen(path, MAX_PATH_LEN);
     size_t sl = strnlen(filename, MAX_FILENAME_LEN);
-    str = calloc(ul + sl + needs_separator + 1, sizeof(char));
-    if (!str) {
-        fprintf(stderr, "path_append(): calloc failure!\n");
-        exit_failure();
-    }
+    str = CALLOC(ul + sl + needs_separator + 1, sizeof(char));
     strncpy(str, path, ul);
     if (needs_separator) {
         str[ul] = '/';
@@ -85,3 +86,40 @@ void erase_string(FILE *file, size_t max_len, char *s)
         fprintf(file, "\b");
     }
 }
+
+char *generate_salt()
+{
+    char *out;
+    out = CALLOC(SALT_LEN + 1, sizeof(char));
+    uuid_t uu;
+    uuid_generate(uu);
+    uuid_unparse(uu, out);
+    return out;
+}
+
+char *generate_md5sum(const char *str)
+{
+    MD5_CTX c;
+    unsigned char md5[MD5_DIGEST_LENGTH];
+    size_t len = strnlen(str, MAX_PATH_LEN);
+    char *out = CALLOC(MD5_HASH_LEN + 1, sizeof(char));
+
+    MD5_Init(&c);
+    MD5_Update(&c, str, len);
+    MD5_Final(md5, &c);
+
+    for(int i = 0; i < MD5_DIGEST_LENGTH; i++) {
+        sprintf(out + 2 * i, "%02x", md5[i]);
+    }
+    return out;
+}
+
+void *CALLOC(size_t nmemb, size_t size)
+{
+    void *ptr = calloc(nmemb, size);
+    if (!ptr) {
+        fprintf(stderr, "calloc() failed, %s!\n", strerror(errno));
+        exit_failure();
+    }
+    return ptr;
+}
diff --git a/src/util.h b/src/util.h
index eefcb95..7a5a260 100644
--- a/src/util.h
+++ b/src/util.h
@@ -36,17 +36,17 @@ char *path_append(const char *path, const char *filename);
 int64_t round_div(int64_t a, int64_t b);
 
 /**
- * \brief wrapper for pthread_mutex_lock()
+ * \brief wrapper for pthread_mutex_lock(), with error handling
  */
 void PTHREAD_MUTEX_LOCK(pthread_mutex_t *x);
 
 /**
- * \brief wrapper for pthread_mutex_unlock()
+ * \brief wrapper for pthread_mutex_unlock(), with error handling
  */
 void PTHREAD_MUTEX_UNLOCK(pthread_mutex_t *x);
 
 /**
- * \brief wrapper for exit(EXIT_FAILURE)
+ * \brief wrapper for exit(EXIT_FAILURE), with error handling
  */
 void exit_failure(void);
 
@@ -55,4 +55,23 @@ void exit_failure(void);
  */
 void erase_string(FILE *file, size_t max_len, char *s);
 
+/**
+ * \brief generate the salt for authentication string
+ * \details this effectively generates a UUID string, which we use as the salt
+ * \return a pointer to a 37-char array with the salt.
+ */
+char *generate_salt();
+
+/**
+ * \brief generate the md5sum of a string
+ * \param[in] str a character array for the input string
+ * \return a pointer to a 33-char array with the salt
+ */
+char *generate_md5sum(const char *str);
+
+/**
+ * \brief wrapper for calloc(), with error handling
+ */
+void *CALLOC(size_t nmemb, size_t size);
+
 #endif