descriptors: implement some helper functions

- add dvbpsi_CanDecodeAsDescriptor() helper function
- add dvbpsi_IsDescriptorDecoded() helper function
- update descriptors

src/descriptor.c

@@ -39,6 +39,41 @@
 #include "dvbpsi.h"
 #include "descriptor.h"
 
+/*****************************************************************************
+ * dvbpsi_IsDescriptor
+ *****************************************************************************
+ * Is this descriptor of type i_tag?
+ *****************************************************************************/
+static inline bool dvbpsi_IsDescriptor(dvbpsi_descriptor_t *p_descriptor, const uint8_t i_tag)
+{
+    return (p_descriptor->i_tag == i_tag);
+}
+
+/*****************************************************************************
+ * IsDescriptorDecoded
+ *****************************************************************************
+ * Is this descriptor already decoded?
+ *****************************************************************************/
+bool dvbpsi_IsDescriptorDecoded(dvbpsi_descriptor_t *p_descriptor)
+{
+    return (p_descriptor->p_decoded != NULL);
+}
+
+/*****************************************************************************
+ * dvbpsi_CanDescodeAsDescriptor
+ *****************************************************************************
+ * Can Decode this descriptor as?
+ *****************************************************************************/
+bool dvbpsi_CanDecodeAsDescriptor(dvbpsi_descriptor_t *p_descriptor, const uint8_t i_tag)
+{
+    if (!p_descriptor)
+        return false;
+
+    if (!dvbpsi_IsDescriptor(p_descriptor, i_tag))
+        return false;
+
+    return true;
+}
 
 /*****************************************************************************
  * dvbpsi_NewDescriptor

src/descriptor.h

@@ -68,7 +68,6 @@ typedef struct dvbpsi_descriptor_s
 
 } dvbpsi_descriptor_t;
 
-
 /*****************************************************************************
  * dvbpsi_NewDescriptor
  *****************************************************************************/
@@ -97,6 +96,28 @@ dvbpsi_descriptor_t* dvbpsi_NewDescriptor(uint8_t i_tag, uint8_t i_length,
  */
 void dvbpsi_DeleteDescriptors(dvbpsi_descriptor_t* p_descriptor);
 
+/*****************************************************************************
+ * dvbpsi_CanDecodeAsDescriptor
+ *****************************************************************************/
+/*!
+ * \fn bool dvbpsi_CanDecodeAsDescriptor(dvbpsi_descriptor_t *p_descriptor, const uint8_t i_tag);
+ * \brief Checks if descriptor tag matches.
+ * \param p_descriptor pointer to descriptor allocated with @see dvbpsi_NewDescriptor
+ * \param i_tag descriptor tag to evaluate against
+ * \return true if descriptor can be decoded, false if not.
+ */
+bool dvbpsi_CanDecodeAsDescriptor(dvbpsi_descriptor_t *p_descriptor, const uint8_t i_tag);
+
+/*****************************************************************************
+ * dvbpsi_IsDescriptorDecoded
+ *****************************************************************************/
+/*!
+ * \fn bool dvbpsi_IsDescriptorDecoded(dvbpsi_descriptor_t *p_descriptor);
+ * \brief Checks if descriptor was already decoded.
+ * \param p_descriptor pointer to descriptor allocated with @see dvbpsi_NewDescriptor
+ * \return true if descriptor can be decoded, false if already decoded.
+ */
+bool dvbpsi_IsDescriptorDecoded(dvbpsi_descriptor_t *p_descriptor);
 
 #ifdef __cplusplus
 };

src/descriptors/dr_02.c

@@ -48,11 +48,11 @@ dvbpsi_vstream_dr_t * dvbpsi_DecodeVStreamDr(dvbpsi_descriptor_t * p_descriptor)
   dvbpsi_vstream_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x02)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x02))
      return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_03.c

@@ -49,11 +49,11 @@ dvbpsi_astream_dr_t * dvbpsi_DecodeAStreamDr(dvbpsi_descriptor_t * p_descriptor)
   dvbpsi_astream_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x03)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x03))
      return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */
@@ -67,10 +67,10 @@ dvbpsi_astream_dr_t * dvbpsi_DecodeAStreamDr(dvbpsi_descriptor_t * p_descriptor)
     return NULL;
   }
 
-  p_decoded->b_free_format = (p_descriptor->p_data[0] & 0x80);
+  p_decoded->b_free_format = (p_descriptor->p_data[0] & 0x80) ? true : false;
   p_decoded->i_id = (p_descriptor->p_data[0] & 0x40) >> 6;
   p_decoded->i_layer = (p_descriptor->p_data[0] & 0x30) >> 4;
-  p_decoded->b_variable_rate_audio_indicator = (p_descriptor->p_data[0] & 0x08) >> 3;
+  p_decoded->b_variable_rate_audio_indicator = ((p_descriptor->p_data[0] & 0x08) >> 3) ? true : false;
 
   p_descriptor->p_decoded = (void*)p_decoded;
 

src/descriptors/dr_04.c

@@ -50,11 +50,11 @@ dvbpsi_hierarchy_dr_t * dvbpsi_DecodeHierarchyDr(
   dvbpsi_hierarchy_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x04)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x04))
      return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_05.c

@@ -50,11 +50,11 @@ dvbpsi_registration_dr_t * dvbpsi_DecodeRegistrationDr(
   dvbpsi_registration_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x05)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x05))
      return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_06.c

@@ -50,13 +50,9 @@ dvbpsi_ds_alignment_dr_t * dvbpsi_DecodeDSAlignmentDr(
   dvbpsi_ds_alignment_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x06)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x06))
     return NULL;
 
-  /* Don't decode twice */
-  if(p_descriptor->p_decoded)
-    return p_descriptor->p_decoded;
-
   /* Allocate memory */
   p_decoded = (dvbpsi_ds_alignment_dr_t*)
                                 malloc(sizeof(dvbpsi_ds_alignment_dr_t));

src/descriptors/dr_07.c

@@ -50,11 +50,11 @@ dvbpsi_target_bg_grid_dr_t * dvbpsi_DecodeTargetBgGridDr(
   dvbpsi_target_bg_grid_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x07)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x07))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_08.c

@@ -49,11 +49,11 @@ dvbpsi_vwindow_dr_t * dvbpsi_DecodeVWindowDr(dvbpsi_descriptor_t * p_descriptor)
   dvbpsi_vwindow_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x08)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x08))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_09.c

@@ -49,11 +49,11 @@ dvbpsi_ca_dr_t * dvbpsi_DecodeCADr(dvbpsi_descriptor_t * p_descriptor)
   dvbpsi_ca_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x09)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x09))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_0a.c

@@ -50,11 +50,11 @@ dvbpsi_iso639_dr_t * dvbpsi_DecodeISO639Dr(dvbpsi_descriptor_t * p_descriptor)
   int i;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x0a)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x0a))
      return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_0b.c

@@ -50,11 +50,11 @@ dvbpsi_system_clock_dr_t * dvbpsi_DecodeSystemClockDr(
   dvbpsi_system_clock_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x0b)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x0b))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_0c.c

@@ -50,11 +50,11 @@ dvbpsi_mx_buff_utilization_dr_t * dvbpsi_DecodeMxBuffUtilizationDr(
   dvbpsi_mx_buff_utilization_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x0c)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x0c))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_0d.c

@@ -50,11 +50,11 @@ dvbpsi_copyright_dr_t * dvbpsi_DecodeCopyrightDr(
   dvbpsi_copyright_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x0d)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x0d))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_0e.c

@@ -50,11 +50,11 @@ dvbpsi_max_bitrate_dr_t * dvbpsi_DecodeMaxBitrateDr(
   dvbpsi_max_bitrate_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x0e)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x0e))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_0f.c

@@ -50,11 +50,11 @@ dvbpsi_private_data_dr_t * dvbpsi_DecodePrivateDataDr(
   dvbpsi_private_data_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x0f)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x0f))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_40.c

@@ -48,11 +48,11 @@ dvbpsi_network_name_dr_t* dvbpsi_DecodeNetworkNameDr(
     dvbpsi_network_name_dr_t * p_decoded;
 
     /* Check the tag */
-    if (p_descriptor->i_tag != 0x40)
+    if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x40))
         return NULL;
 
     /* Don't decode twice */
-    if (p_descriptor->p_decoded)
+    if (dvbpsi_IsDescriptorDecoded(p_descriptor))
        return p_descriptor->p_decoded;
 
     /* Allocate memory */

src/descriptors/dr_42.c

@@ -51,11 +51,11 @@ dvbpsi_stuffing_dr_t * dvbpsi_DecodeStuffingDr(
   dvbpsi_stuffing_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x42)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x42))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_43.c

@@ -50,11 +50,11 @@ dvbpsi_sat_deliv_sys_dr_t * dvbpsi_DecodeSatDelivSysDr(
   dvbpsi_sat_deliv_sys_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x43)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x43))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_44.c

@@ -50,11 +50,11 @@ dvbpsi_cable_deliv_sys_dr_t * dvbpsi_DecodeCableDelivSysDr(
   dvbpsi_cable_deliv_sys_dr_t * p_decoded;
 
   /* Check the tag */
-  if (p_descriptor->i_tag != 0x44)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x44))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_45.c

@@ -50,11 +50,11 @@ dvbpsi_vbi_dr_t * dvbpsi_DecodeVBIDataDr(
   dvbpsi_vbi_dr_t * p_decoded;
 
   /* Check the tag */
-  if( p_descriptor->i_tag != 0x45 )
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x45))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Decode data and check the length */

src/descriptors/dr_47.c

@@ -51,11 +51,11 @@ dvbpsi_bouquet_name_dr_t * dvbpsi_DecodeBouquetNameDr(
   dvbpsi_bouquet_name_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x47)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x47))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_48.c

@@ -51,11 +51,11 @@ dvbpsi_service_dr_t * dvbpsi_DecodeServiceDr(
   dvbpsi_service_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x48)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x48))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_4d.c

@@ -50,10 +50,14 @@ dvbpsi_short_event_dr_t * dvbpsi_DecodeShortEventDr(dvbpsi_descriptor_t * p_desc
   int i_len2;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x4d ||
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x4d) ||
       p_descriptor->i_length < 5 )
     return NULL;
 
+  /* Don't decode twice */
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
+     return p_descriptor->p_decoded;
+
   /* Check length */
   i_len1 = p_descriptor->p_data[3];
   i_len2 = p_descriptor->p_data[4+i_len1];

src/descriptors/dr_4e.c

@@ -51,12 +51,12 @@ dvbpsi_extended_event_dr_t * dvbpsi_DecodeExtendedEventDr(dvbpsi_descriptor_t *
   uint8_t *p;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x4e ||
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x4e) ||
      p_descriptor->i_length < 6 )
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_52.c

@@ -49,11 +49,11 @@ dvbpsi_stream_identifier_dr_t * dvbpsi_DecodeStreamIdentifierDr(
   dvbpsi_stream_identifier_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x52)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x52))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_55.c

@@ -51,11 +51,11 @@ dvbpsi_parental_rating_dr_t * dvbpsi_DecodeParentalRatingDr(
   dvbpsi_parental_rating_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x55)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x55))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_56.c

@@ -50,11 +50,12 @@ dvbpsi_teletext_dr_t * dvbpsi_DecodeTeletextDr(
   dvbpsi_teletext_dr_t * p_decoded;
 
   /* Check the tag */
-  if( (p_descriptor->i_tag != 0x56) && (p_descriptor->i_tag != 0x46) )
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x56) &&
+      !dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x46))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Decode data and check the length */

src/descriptors/dr_58.c

@@ -52,11 +52,11 @@ dvbpsi_local_time_offset_dr_t * dvbpsi_DecodeLocalTimeOffsetDr(
   dvbpsi_local_time_offset_t * p_current;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x58)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x58))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_59.c

@@ -52,13 +52,17 @@ dvbpsi_subtitling_dr_t * dvbpsi_DecodeSubtitlingDr(
   dvbpsi_subtitling_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x59)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x59))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
+  /* Decode data and check the length */
+  if(p_descriptor->i_length < 3)
+    return NULL;
+
   /* Allocate memory */
   p_decoded =
         (dvbpsi_subtitling_dr_t*)malloc(sizeof(dvbpsi_subtitling_dr_t));

src/descriptors/dr_5a.c

@@ -50,11 +50,11 @@ dvbpsi_terr_deliv_sys_dr_t * dvbpsi_DecodeTerrDelivSysDr(
   dvbpsi_terr_deliv_sys_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x5a)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x5a))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */

src/descriptors/dr_69.c

@@ -49,14 +49,14 @@ dvbpsi_PDC_dr_t * dvbpsi_DecodePDCDr(dvbpsi_descriptor_t * p_descriptor)
   dvbpsi_PDC_dr_t * p_decoded;
 
   /* Check the tag */
-  if(p_descriptor->i_tag != 0x69)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x69))
     return NULL;
 
   /* Don't decode twice */
-  if(p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
-  /* Decode data and check the length */
+  /* Check the length */
   if( p_descriptor->i_length != 3)
     return NULL;
 

src/descriptors/dr_8a.c

@@ -48,11 +48,11 @@ dvbpsi_cuei_dr_t * dvbpsi_DecodeCUEIDr(dvbpsi_descriptor_t * p_descriptor)
   dvbpsi_cuei_dr_t *p_decoded;
 
   /* Check the tag */
-  if (p_descriptor->i_tag != 0x8a)
+  if (!dvbpsi_CanDecodeAsDescriptor(p_descriptor, 0x8a))
     return NULL;
 
   /* Don't decode twice */
-  if (p_descriptor->p_decoded)
+  if (dvbpsi_IsDescriptorDecoded(p_descriptor))
      return p_descriptor->p_decoded;
 
   /* Allocate memory */