[tracker] tracker-extract: Add helpers to retrieve BE uints/sizes from MP3 ID3 tags

[Carlos Garnacho <carlosg src gnome org>]

commit ccf5b4b5af4fae2187fcf0e540fd0e1272678a07
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Jan 29 14:00:07 2017 +0100

    tracker-extract: Add helpers to retrieve BE uints/sizes from MP3 ID3 tags
    
    The current code pretty much seems to assume that the host byte order
    is little endian, as multibyte data contained in ID3 frames is BE and
    byte swapping is performed. Add helpers that do care to translate that
    to the host memory order.

 src/tracker-extract/tracker-extract-mp3.c |   99 +++++++++++++++++++----------
 1 files changed, 64 insertions(+), 35 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-mp3.c b/src/tracker-extract/tracker-extract-mp3.c
index 1d80d51..32e4ad9 100644
--- a/src/tracker-extract/tracker-extract-mp3.c
+++ b/src/tracker-extract/tracker-extract-mp3.c
@@ -447,6 +447,60 @@ strnlen (const char *str, size_t max)
 
 #endif /* HAVE_STRNLEN */
 
+/* Helpers to get data from BE */
+inline static guint32
+extract_uint32 (gconstpointer data)
+{
+       const guint32 *ptr = data;
+       return GUINT32_FROM_BE (*ptr);
+}
+
+inline static guint16
+extract_uint16 (gconstpointer data)
+{
+       const guint16 *ptr = data;
+       return GUINT16_FROM_BE (*ptr);
+}
+
+inline static guint32
+extract_uint32_7bit (gconstpointer data)
+{
+       const guchar *ptr = data;
+#if (G_BYTE_ORDER == G_LITTLE_ENDIAN)
+       return (((ptr[0] & 0x7F) << 21) |
+               ((ptr[1] & 0x7F) << 14) |
+               ((ptr[2] & 0x7F) << 7) |
+               ((ptr[3] & 0x7F) << 0));
+#elif (G_BYTE_ORDER == G_BIG_ENDIAN)
+       return (((ptr[0] & 0x7F) << 0) |
+               ((ptr[1] & 0x7F) << 7) |
+               ((ptr[2] & 0x7F) << 14) |
+               ((ptr[3] & 0x7F) << 21));
+#else
+       g_warning ("Can't figure endianness");
+       return 0;
+#endif
+}
+
+/* id3v20 is odd... */
+inline static guint32
+extract_uint32_3byte (gconstpointer data)
+{
+       const guchar *ptr = data;
+#if (G_BYTE_ORDER == G_LITTLE_ENDIAN)
+       return ((ptr[0] << 16) |
+               (ptr[1] << 8) |
+               (ptr[2] << 0));
+#elif (G_BYTE_ORDER == G_BIG_ENDIAN)
+       return ((ptr[0] << 0) |
+               (ptr[1] << 8) |
+               (ptr[2] << 16));
+#else
+       g_warning ("Can't figure endianness");
+       return 0;
+#endif
+}
+
 static void
 id3tag_free (id3tag *tags)
 {
@@ -1793,10 +1847,7 @@ parse_id3v24 (const gchar           *data,
         * unsychronisation, including padding, excluding the header
         * but not excluding the extended header (total tag size - 10)
         */
-       tsize = (((data[6] & 0x7F) << 21) |
-                ((data[7] & 0x7F) << 14) |
-                ((data[8] & 0x7F) << 7) |
-                ((data[9] & 0x7F) << 0));
+       tsize = extract_uint32_7bit (&data[6]);
 
        /* We don't handle experimental cases */
        if (experimental) {
@@ -1823,10 +1874,7 @@ parse_id3v24 (const gchar           *data,
                 *   Extended Flags         $xx xx
                 *   Size of padding        $xx xx xx xx
                 */
-               ext_header_size = (((data[10] & 0x7F) << 21) |
-                                  ((data[11] & 0x7F) << 14) |
-                                  ((data[12] & 0x7F) << 7) |
-                                  ((data[13] & 0x7F) << 0));
+               ext_header_size = extract_uint32_7bit (&data[10]);
 
                /* Where the 'Extended header size', currently 6 or 10
                 * bytes, excludes itself. The 'Size of padding' is
@@ -1874,10 +1922,7 @@ parse_id3v24 (const gchar           *data,
 
                frame = id3v24_get_frame (frame_name);
 
-               csize = (((data[pos+4] & 0x7F) << 21) |
-                        ((data[pos+5] & 0x7F) << 14) |
-                        ((data[pos+6] & 0x7F) << 7) |
-                        ((data[pos+7] & 0x7F) << 0));
+               csize = (size_t) extract_uint32_7bit (&data[pos + 4]);
 
                if (pos + frame_size + csize > size) {
                        g_debug ("[v24] Size of current frame '%s' (%" G_GSIZE_FORMAT ") "
@@ -1887,8 +1932,7 @@ parse_id3v24 (const gchar           *data,
                        break;
                }
 
-               flags = (((unsigned char) (data[pos + 8]) << 8) +
-                        ((unsigned char) (data[pos + 9])));
+               flags = extract_uint16 (&data[pos + 8]);
 
                pos += frame_size;
 
@@ -2005,10 +2049,7 @@ parse_id3v23 (const gchar          *data,
         * unsychronisation, including padding, excluding the header
         * but not excluding the extended header (total tag size - 10)
         */
-       tsize = (((data[6] & 0x7F) << 21) |
-                ((data[7] & 0x7F) << 14) |
-                ((data[8] & 0x7F) << 7) |
-                ((data[9] & 0x7F) << 0));
+       tsize = extract_uint32_7bit (&data[6]);
 
        /* We don't handle experimental cases */
        if (experimental) {
@@ -2035,10 +2076,7 @@ parse_id3v23 (const gchar          *data,
                 *   Extended Flags         $xx xx
                 *   Size of padding        $xx xx xx xx
                 */
-               ext_header_size = (((unsigned char)(data[10]) << 24) |
-                                  ((unsigned char)(data[11]) << 16) |
-                                  ((unsigned char)(data[12]) << 8) |
-                                  ((unsigned char)(data[13]) << 0));
+               ext_header_size = extract_uint32 (&data[10]);
 
                /* Where the 'Extended header size', currently 6 or 10
                 * bytes, excludes itself. The 'Size of padding' is
@@ -2080,10 +2118,7 @@ parse_id3v23 (const gchar          *data,
 
                frame = id3v24_get_frame (frame_name);
 
-               csize = (((unsigned char)(data[pos + 4]) << 24) |
-                        ((unsigned char)(data[pos + 5]) << 16) |
-                        ((unsigned char)(data[pos + 6]) << 8)  |
-                        ((unsigned char)(data[pos + 7]) << 0) );
+               csize = (size_t) extract_uint32 (&data[pos + 4]);
 
                if (pos + frame_size + csize > size) {
                        g_debug ("[v23] Size of current frame '%s' (%" G_GSIZE_FORMAT ") "
@@ -2093,8 +2128,7 @@ parse_id3v23 (const gchar          *data,
                        break;
                }
 
-               flags = (((unsigned char)(data[pos + 8]) << 8) +
-                        ((unsigned char)(data[pos + 9])));
+               flags = extract_uint16 (&data[pos + 8]);
 
                pos += frame_size;
 
@@ -2185,10 +2219,7 @@ parse_id3v20 (const gchar          *data,
        }
 
        unsync = (data[5] & 0x80) > 0;
-       tsize = (((data[6] & 0x7F) << 21) |
-                ((data[7] & 0x7F) << 14) |
-                ((data[8] & 0x7F) << 07) |
-                ((data[9] & 0x7F) << 00));
+       tsize = extract_uint32_7bit (&data[6]);
 
        if (tsize + header_size > size)  {
                g_message ("[v20] Expected MP3 tag size and header size to be within file size boundaries");
@@ -2218,9 +2249,7 @@ parse_id3v20 (const gchar          *data,
 
                frame = id3v2_get_frame (frame_name);
 
-               csize = (((unsigned char)(data[pos + 3]) << 16) +
-                        ((unsigned char)(data[pos + 4]) << 8) +
-                        ((unsigned char)(data[pos + 5]) ) );
+               csize = (size_t) extract_uint32_3byte (&data[pos + 3]);
 
                if (pos + frame_size + csize > size) {
                        g_debug ("[v20] Size of current frame '%s' (%" G_GSIZE_FORMAT ") "