dvbpsi_decoder_t: solve alignment issues with dvbpsi_decoder_t casting.

Repack DVBPSI_DECODER_COMMON to be byte aligned and add some checks to
do clever casting.
The TOT and SIS table structure definition need to be packed explicitly for use on ARM and MIPS platforms.

src/dvbpsi.c

@@ -170,7 +170,7 @@ void dvbpsi_delete(dvbpsi_t *p_dvbpsi)
  * dvbpsi_decoder_new
  *****************************************************************************/
 #define DVBPSI_INVALID_CC (0xFF)
-dvbpsi_decoder_t *dvbpsi_decoder_new(dvbpsi_callback_gather_t pf_gather,
+void *dvbpsi_decoder_new(dvbpsi_callback_gather_t pf_gather,
     const int i_section_max_size, const bool b_discontinuity, const size_t psi_size)
 {
     assert(psi_size >= sizeof(dvbpsi_decoder_t));
@@ -179,6 +179,7 @@ dvbpsi_decoder_t *dvbpsi_decoder_new(dvbpsi_callback_gather_t pf_gather,
     if (p_decoder == NULL)
         return NULL;
 
+    memcpy(&p_decoder->i_magic[0], "psi", 3);
     p_decoder->pf_gather = pf_gather;
     p_decoder->p_current_section = NULL;
     p_decoder->i_section_max_size = i_section_max_size;

src/dvbpsi.h

@@ -42,6 +42,16 @@
 extern "C" {
 #endif
 
+/*****************************************************************************
+ * Helper for GCC version checks borrowed from VLC.
+ *****************************************************************************/
+#ifdef __GNUC__
+# define DVBPSI_GCC_VERSION(maj,min) \
+    ((__GNUC__ > (maj)) || (__GNUC__ == (maj) && __GNUC_MINOR__ >= (min)))
+#else
+# define DVBPSI_GCC_VERSION(maj,min) (0)
+#endif
+
 /*****************************************************************************
  * dvbpsi_t
  *****************************************************************************/
@@ -90,7 +100,22 @@ typedef struct dvbpsi_decoder_s dvbpsi_decoder_t;
  * \def DVBPSI_DECODER(x)
  * \brief Helper macro for casting a private decoder into a dvbpsi_decoder_t
  */
-#define DVBPSI_DECODER(x) ((dvbpsi_decoder_t *)(x))
+/* Clever cast borrowed from VLC */
+#if DVBPSI_GCC_VERSION(4,0)
+# ifndef __cplusplus
+#  define DVBPSI_DECODER( x ) \
+    __builtin_choose_expr( \
+        __builtin_offsetof(__typeof__(*(x)), i_magic), \
+        (void)0, \
+        (dvbpsi_decoder_t *)(x))
+# else
+#  define DVBPSI_DECODER( x ) \
+    ((dvbpsi_decoder_t *)(x) \
+      + 0 * __builtin_offsetof(__typeof__(*(x)), i_magic))
+# endif
+#else
+# define DVBPSI_DECODER(x) ((dvbpsi_decoder_t *)(x))
+#endif
 
 /*****************************************************************************
  * dvbpsi_t
@@ -186,6 +211,28 @@ typedef struct dvbpsi_psi_section_s dvbpsi_psi_section_t;
 typedef void (* dvbpsi_callback_gather_t)(dvbpsi_t *p_dvbpsi,  /*!< pointer to dvbpsi handle */
                             dvbpsi_psi_section_t* p_section);  /*!< pointer to psi section */
 
+/*****************************************************************************
+ * DVBPSI_DECODER_COMMON
+ *****************************************************************************/
+#define DVBPSI_DECODER_COMMON                                                     \
+/*!                                                                               \
+ * \name DVBPSI_DECODER_COMMON                                                    \
+ * these members are common for all dvbpsi_decoder_t                              \
+ */                                                                               \
+/**@{*/                                                                           \
+    uint8_t  i_magic[3];           /*!< Reserved magic value */                   \
+    bool     b_complete_header;    /*!< Flag for header completion */             \
+    bool     b_discontinuity;      /*!< Discontinuity flag */                     \
+    bool     b_current_valid;      /*!< Current valid indicator */                \
+    uint8_t  i_continuity_counter; /*!< Continuity counter */                     \
+    uint8_t  i_last_section_number;/*!< Last received section number */           \
+    dvbpsi_psi_section_t *p_current_section; /*!< Current section */              \
+    dvbpsi_psi_section_t *p_sections; /*!< List of received PSI sections */       \
+    dvbpsi_callback_gather_t  pf_gather;/*!< PSI decoder's callback */            \
+    int      i_section_max_size;   /*!< Max size of a section for this decoder */ \
+    int      i_need;               /*!< Bytes needed */                           \
+/**@}*/
+
 /*****************************************************************************
  * struct dvbpsi_decoder_s
  *****************************************************************************/
@@ -196,18 +243,6 @@ typedef void (* dvbpsi_callback_gather_t)(dvbpsi_t *p_dvbpsi,  /*!< pointer to d
  * This structure shouldn't be used but if you want to write an external
  * decoder.
  */
-#define DVBPSI_DECODER_COMMON                                                     \
-    dvbpsi_callback_gather_t  pf_gather;/*!< PSI decoder's callback */            \
-    int      i_section_max_size;   /*!< Max size of a section for this decoder */ \
-    uint8_t  i_continuity_counter; /*!< Continuity counter */                     \
-    bool     b_discontinuity;      /*!< Discontinuity flag */                     \
-    dvbpsi_psi_section_t *p_current_section; /*!< Current section */              \
-    bool     b_current_valid;      /*!< Current valid indicator */                \
-    uint8_t  i_last_section_number;/*!< Last received section number */           \
-    dvbpsi_psi_section_t *p_sections; /*!< List of received PSI sections */       \
-    int      i_need;               /*!< Bytes needed */                           \
-    bool     b_complete_header;    /*!< Flag for header completion */
-
 struct dvbpsi_decoder_s
 {
     DVBPSI_DECODER_COMMON
@@ -217,22 +252,25 @@ struct dvbpsi_decoder_s
  * dvbpsi_decoder_new
  *****************************************************************************/
 /*!
- * \fn dvbpsi_decoder_t *dvbpsi_decoder_new(dvbpsi_callback_gather_t pf_gather,
+ * \fn void *dvbpsi_decoder_new(dvbpsi_callback_gather_t pf_gather,
  *     const int i_section_max_size, const bool b_discontinuity, const size_t psi_size);
- * \brief Create a new dvbpsi_decoder_t.
+ * \brief Create a new (private) dvbpsi decoder.
  * \param pf_gather pointer to gather function for PSI decoder.
  * \param i_section_max_size Max size of a section for this decoder
  * \param b_discontinuity Discontinuity flag
  * \param psi_size size of new PSI struct, eg: sizeof(dvbpsi_pat_t)
- * \return pointer to dvbpsi_decoder_t
+ * \return pointer to memory of size 'psi_size' that can be casted into a dvbpsi_decoder_t.
  *
- * Creates a dvbpsi_decoder_t pointer to struct dvbpsi_decoder_s. It should be
- * delete with @see dvbpsi_decoder_delete() function.
+ * Creates a void pointer that points to a private dvbpsi decoder struct (eg: dvbpsi_pat_t).
+ * The first elements in this newly created decoder should contain DVBPSI_DECODER_COMMON, which
+ * corresponds to a dvbpsi_decoder_t.
+ * Upon return the pointer should be casted to the correct type. Delete the pointer
+ * with @see dvbpsi_decoder_delete() function.
  */
-dvbpsi_decoder_t *dvbpsi_decoder_new(dvbpsi_callback_gather_t pf_gather,
-                                    const int i_section_max_size,
-                                    const bool b_discontinuity,
-                                    const size_t psi_size);
+void *dvbpsi_decoder_new(dvbpsi_callback_gather_t pf_gather,
+                         const int i_section_max_size,
+                         const bool b_discontinuity,
+                         const size_t psi_size);
 
 /*****************************************************************************
  * dvbpsi_decoder_delete

src/tables/nit_private.h

@@ -39,14 +39,14 @@ typedef struct dvbpsi_nit_decoder_s
 {
     DVBPSI_DECODER_COMMON
 
-    uint16_t                      i_network_id;
-
     dvbpsi_nit_callback           pf_nit_callback;
     void *                        p_cb_data;
 
     dvbpsi_nit_t                  current_nit;
     dvbpsi_nit_t *                p_building_nit;
 
+    uint16_t                      i_network_id;
+
 } dvbpsi_nit_decoder_t;
 
 /*****************************************************************************

src/tables/pmt_private.h

@@ -37,14 +37,14 @@ typedef struct dvbpsi_pmt_decoder_s
 {
     DVBPSI_DECODER_COMMON
 
-    uint16_t                      i_program_number;
-
     dvbpsi_pmt_callback           pf_pmt_callback;
     void *                        p_cb_data;
 
     dvbpsi_pmt_t                  current_pmt;
     dvbpsi_pmt_t *                p_building_pmt;
 
+    uint16_t                      i_program_number;
+
 } dvbpsi_pmt_decoder_t;
 
 /*****************************************************************************

src/tables/sis.h

@@ -97,7 +97,7 @@ typedef struct dvbpsi_sis_s
   /* FIXME: alignment stuffing */
   uint32_t i_ecrc; /*!< CRC 32 of decrypted splice_info_section */
 
-} dvbpsi_sis_t;
+} __attribute__((packed)) dvbpsi_sis_t;
 
 /*****************************************************************************
  * Splice Commands

src/tables/tot.h

@@ -67,7 +67,7 @@ typedef struct dvbpsi_tot_s
 
     uint32_t      i_crc;                          /*!< CRC_32 (TOT only) */
 
-} dvbpsi_tot_t;
+} __attribute__((packed)) dvbpsi_tot_t;
 
 /*****************************************************************************
  * dvbpsi_tot_callback