udp_header.h

   1 /*
   2  * Copyright (C) 2006-2009 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file udp_header.h some macros used by udp_send.c and udp_recv.c. */
   8 #include <net/if.h>
   9
  10 /**
  11  * Number of bytes of the paraslash udp header.
  12  *
  13  * The udp sender prepends a header at the beginning of each data chunk. Within
  14  * this header, the type of the current audio stream and the * type of this
  15  * data chunk is coded.
  16  */
  17 #define UDP_AUDIO_HEADER_LEN 16
  18
  19 /** The possible stream types. */
  20 enum udp_stream_type {
  21         /** Used for mp3 and aac streams. */
  22         UDP_PLAIN_STREAM,
  23         /** Ogg vorbis streams. */
  24         UDP_HEADER_STREAM,
  25         /** stream type not yet known. */
  26         UDP_UNKNOWN_STREAM
  27 };
  28
  29 /** The possible packet types. */
  30 enum udp_audio_packet_type {
  31         /** Beginning of file. */
  32         UDP_BOF_PACKET,
  33         /** End of file. */
  34         UDP_EOF_PACKET,
  35         /** Combined header/data packet (ogg only). */
  36         UDP_HEADER_PACKET,
  37         /** Packet contains only audio file data. */
  38         UDP_DATA_PACKET,
  39         /** Invalid packet type. */
  40         UDP_UNKNOWN_PACKET
  41 };
  42
  43 /** The contents of an udp audio header. */
  44 struct udp_audio_header {
  45         /** see \ref udp_stream_type. */
  46         uint8_t stream_type;
  47         /** see \ref udp_audio_packet_type. */
  48         uint8_t packet_type;
  49         /** Non-zero only for header packets. */
  50         uint16_t header_len;
  51         /** Length of header plus audio file data. */
  52         uint16_t payload_len;
  53 };
  54
  55 /**
  56  * Write a struct udp_audio_header to a buffer.
  57  *
  58  * \param buf The buffer to write to.
  59  * \param h The audio header to write.
  60  *
  61  * Used by the udp sender.
  62  *
  63  */
  64 _static_inline_ void write_udp_audio_header(char *buf, struct udp_audio_header *h)
  65 {
  66         memcpy(buf, "UDPM", 4);
  67         write_u8(buf + 4, h->stream_type);
  68         write_u8(buf + 5, h->packet_type);
  69         write_u16(buf + 6, h->header_len);
  70         write_u16(buf + 8, h->payload_len);
  71         memset(buf + 10, 0, 6);
  72 }
  73
  74 /**
  75  * Used by the udp receiver to read a struct udp_audio_header from a buffer.
  76  *
  77  * \param buf The buffer to read from.
  78  * \param len The length of \a buf.
  79  * \param h Result pointer.
  80  *
  81  * \return 1 if \a buf contains a valid udp audio header, -1 else.
  82  */
  83 _static_inline_ int read_udp_audio_header(char *buf, size_t len,
  84                 struct udp_audio_header *h)
  85 {
  86         if (len < 4)
  87                 goto err;
  88         if (memcmp(buf, "UDPM", 4))
  89                 goto err;
  90         h->stream_type = read_u8(buf + 4);
  91         h->packet_type = read_u8(buf + 5);
  92         h->header_len = read_u16(buf + 6);
  93         h->payload_len = read_u16(buf + 8);
  94         return 1;
  95 err:
  96         h->stream_type = UDP_UNKNOWN_STREAM;
  97         h->packet_type = UDP_UNKNOWN_PACKET;
  98         h->header_len = h->payload_len = 0;
  99         return -1;
 100 }