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