source: gs3-extensions/web-audio/trunk/js-mad/jsmad-master/src/stream.js@ 28388

Mad.Error = {
  NONE           : 0x0000,      /* no error */

  BUFLEN         : 0x0001,      /* input buffer too small (or EOF) */
  BUFPTR         : 0x0002,      /* invalid (null) buffer pointer */

  NOMEM          : 0x0031,      /* not enough memory */

  LOSTSYNC       : 0x0101,      /* lost synchronization */
  BADLAYER       : 0x0102,      /* reserved header layer value */
  BADBITRATE     : 0x0103,      /* forbidden bitrate value */
  BADSAMPLERATE  : 0x0104,      /* reserved sample frequency value */
  BADEMPHASIS    : 0x0105,      /* reserved emphasis value */

  BADCRC         : 0x0201,      /* CRC check failed */
  BADBITALLOC    : 0x0211,      /* forbidden bit allocation value */
  BADSCALEFACTOR : 0x0221,      /* bad scalefactor index */
  BADMODE        : 0x0222,      /* bad bitrate/mode combination */
  BADFRAMELEN    : 0x0231,      /* bad frame length */
  BADBIGVALUES   : 0x0232,      /* bad big_values count */
  BADBLOCKTYPE   : 0x0233,      /* reserved block_type */
  BADSCFSI       : 0x0234,      /* bad scalefactor selection info */
  BADDATAPTR     : 0x0235,      /* bad main_data_begin pointer */
  BADPART3LEN    : 0x0236,      /* bad audio data length */
  BADHUFFTABLE   : 0x0237,      /* bad Huffman table select */
  BADHUFFDATA    : 0x0238,      /* Huffman data overrun */
  BADSTEREO      : 0x0239       /* incompatible block_type for JS */
};

Mad.BUFFER_GUARD = 8;
Mad.BUFFER_MDLEN = (511 + 2048 + Mad.BUFFER_GUARD);

Mad.Stream = function (stream) {
    this.stream = stream;                           /* actual buffer (js doesn't have pointers!) */
    this.buffer = 0;                                /* input bitstream buffer */
    this.bufend = stream.length;                    /* input bitstream buffer */
    this.skiplen = 0;                               /* bytes to skip before next frame */

    this.sync = 0;                                  /* stream sync found */
    this.freerate = 0;                              /* free bitrate (fixed) */

    this.this_frame = 0;                            /* start of current frame */
    this.next_frame = 0;                            /* start of next frame */
    
    this.ptr = new Mad.Bit(this.stream, this.buffer); /* current processing bit pointer */
    
    this.anc_ptr = /* MadBit */ null;               /* ancillary bits pointer */
    this.anc_bitlen = 0;                            /* number of ancillary bits */

    this.main_data = /* string */ Mad.Storage.newBuffer(Mad.BUFFER_MDLEN); /* Layer III main_data() */
    this.md_len = 0; /* bytes in main_data */

    var options = 0;                                /* decoding options (see below) */
    var error = Mad.Error.NONE;                     /* error code (see above) */
};

Mad.Stream.fromFile = function(file, callback) {
    var reader = new FileReader();
    reader.onloadend = function (evt) {
        callback(new Mad.Stream(evt.target.result));
    };
    reader.readAsBinaryString(file);
};

Mad.Stream.prototype.readShort = function(bBigEndian) {
    return this.stream.readU16(bBigEndian);
};
    
Mad.Stream.prototype.readSShort = function(bBigEndian) {
    return this.stream.readI16(bBigEndian);
};

Mad.Stream.prototype.getU8 = function(index) {
    return this.stream.getU8(index);
};


Mad.Stream.prototype.readU8 = function() {
    return this.stream.readU8(index);
};

Mad.Stream.prototype.readChars = function(length) {
    return this.stream.read(length);
};

Mad.Stream.prototype.peekChars = function(length) {
    return this.stream.peek(length);
}

/*
 * NAME:        stream->sync()
 * DESCRIPTION: locate the next stream sync word
 */
Mad.Stream.prototype.doSync = function() {
    var ptr = this.ptr.nextbyte();
    var end = this.bufend;

    while (ptr < end - 1 && !(this.getU8(ptr) === 0xff && (this.getU8(ptr + 1) & 0xe0) === 0xe0)) {
        ++ptr;
    }

    if (end - ptr < Mad.BUFFER_GUARD) {
        return -1;
    }

    this.ptr = new Mad.Bit(this.stream, ptr);
    
    return 0;
}