Add support for updating local cache through patches

- refactor some code:
   - code handling the file cache is now in fuse/filecache.c
   - base36 and base16 encoding and decoding moved to utils/hash.c
 - mfshell: add "updates" command calling device/get_updates
 - add container class to store patch information as mfapi/patch.c
 - apicalls: store more info retrieved by file/get_info
 - apicalls: add device/get_updates
 - apicalls: add device/get_patch

utils/hash.c

@@ -23,6 +23,54 @@
 
 #define bufsize 32768
 
+/*
+ * we use this table to convert from a base36 char (ignoring case) to an
+ * integer or from a hex string to binary (in the latter case letters g-z and
+ * G-Z remain unused)
+ * we "waste" these 128 bytes of memory so that we don't need branching
+ * instructions when decoding
+ * we only need 128 bytes because the input is a *signed* char
+ */
+static unsigned char base36_decoding_table[] = {
+/* 0x00 */ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+/* 0x10 */ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+/* 0x20 */ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+/* 0x30 */ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 0, 0, 0,
+/* 0x40 */ 0, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
+/* 0x50 */ 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 0, 0, 0, 0, 0,
+/* 0x60 */ 0, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
+/* 0x70 */ 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 0, 0, 0, 0, 0
+};
+
+/*
+ * table to convert from a byte into the two hexadecimal digits representing
+ * it
+ */
+static char     base16_encoding_table[][2] = {
+    "00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "0A", "0B",
+    "0C", "0D", "0E", "0F", "10", "11", "12", "13", "14", "15", "16", "17",
+    "18", "19", "1A", "1B", "1C", "1D", "1E", "1F", "20", "21", "22", "23",
+    "24", "25", "26", "27", "28", "29", "2A", "2B", "2C", "2D", "2E", "2F",
+    "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "3A", "3B",
+    "3C", "3D", "3E", "3F", "40", "41", "42", "43", "44", "45", "46", "47",
+    "48", "49", "4A", "4B", "4C", "4D", "4E", "4F", "50", "51", "52", "53",
+    "54", "55", "56", "57", "58", "59", "5A", "5B", "5C", "5D", "5E", "5F",
+    "60", "61", "62", "63", "64", "65", "66", "67", "68", "69", "6A", "6B",
+    "6C", "6D", "6E", "6F", "70", "71", "72", "73", "74", "75", "76", "77",
+    "78", "79", "7A", "7B", "7C", "7D", "7E", "7F", "80", "81", "82", "83",
+    "84", "85", "86", "87", "88", "89", "8A", "8B", "8C", "8D", "8E", "8F",
+    "90", "91", "92", "93", "94", "95", "96", "97", "98", "99", "9A", "9B",
+    "9C", "9D", "9E", "9F", "A0", "A1", "A2", "A3", "A4", "A5", "A6", "A7",
+    "A8", "A9", "AA", "AB", "AC", "AD", "AE", "AF", "B0", "B1", "B2", "B3",
+    "B4", "B5", "B6", "B7", "B8", "B9", "BA", "BB", "BC", "BD", "BE", "BF",
+    "C0", "C1", "C2", "C3", "C4", "C5", "C6", "C7", "C8", "C9", "CA", "CB",
+    "CC", "CD", "CE", "CF", "D0", "D1", "D2", "D3", "D4", "D5", "D6", "D7",
+    "D8", "D9", "DA", "DB", "DC", "DD", "DE", "DF", "E0", "E1", "E2", "E3",
+    "E4", "E5", "E6", "E7", "E8", "E9", "EA", "EB", "EC", "ED", "EE", "EF",
+    "F0", "F1", "F2", "F3", "F4", "F5", "F6", "F7", "F8", "F9", "FA", "FB",
+    "FC", "FD", "FE", "FF"
+};
+
 int calc_md5(FILE * file, unsigned char *hash)
 {
     int             bytesRead;
@@ -60,3 +108,60 @@ int calc_sha256(FILE * file, unsigned char *hash)
     free(buffer);
     return 0;
 }
+
+/* decodes a zero terminated string containing hex characters into their
+ * binary representation. The length of the string must be even as pairs of
+ * characters are converted to one output byte. The output buffer must be at
+ * least half the length of the input string.
+ */
+void hex2binary(const char *hex, unsigned char *binary)
+{
+    unsigned char   val1,
+                    val2;
+    const char     *c1,
+                   *c2;
+    unsigned char  *b;
+
+    for (b = binary, c1 = hex, c2 = hex + 1;
+         *c1 != '\0' && *c2 != '\0'; b++, c1 += 2, c2 += 2) {
+        val1 = base36_decoding_table[(int)(*c1)];
+        val2 = base36_decoding_table[(int)(*c2)];
+        *b = (val1 << 4) | val2;
+    }
+}
+
+char *binary2hex(const unsigned char *binary, size_t length)
+{
+    char           *out;
+    char           *p;
+    size_t          i;
+
+    out = malloc(length * 2 + 1);
+    if (out == NULL) {
+        fprintf(stderr, "cannot allocate memory\n");
+        return NULL;
+    }
+    for (i = 0; i < length; i++) {
+        p = base16_encoding_table[binary[i]];
+        out[i * 2] = p[0];
+        out[i * 2 + 1] = p[1];
+    }
+    out[length * 2] = '\0';
+    return out;
+}
+
+/*
+ * a function to convert a char* of the key into a hash of its first three
+ * characters, treating those first three characters as if they represented a
+ * number in base36
+ *
+ * in the future this could be made more dynamic by using the ability of
+ * strtoll to convert numbers of base36 and then only retrieving the desired
+ * amount of high-bits for the desired size of the hashtable
+ */
+int base36_decode_triplet(const char *key)
+{
+    return base36_decoding_table[(int)(key)[0]]*36*36
+         + base36_decoding_table[(int)(key)[1]]*36
+         + base36_decoding_table[(int)(key)[2]];
+}

utils/hash.h

@@ -21,5 +21,8 @@
 
 int             calc_md5(FILE * file, unsigned char *hash);
 int             calc_sha256(FILE * file, unsigned char *hash);
+int             base36_decode_triplet(const char *key);
+void            hex2binary(const char *hex, unsigned char *binary);
+char           *binary2hex(const unsigned char *binary, size_t length);
 
 #endif