code/Audio/Metadata/ID3/Frames/Comment.cs

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Sylloge.Audio.Metadata.ID3.Frames
{
    public class Comment : TextFrame
    {
        public Sylloge.Data.ISO639_2 Language { get; private set; }

        public Comment()
            : base(ID3.Frame.Keys.Comment)
        {
            this.Initialize(0x00, new Data.ISO639_2(Sylloge.Data.ISO639_2.Code.ENG), string.Empty, string.Empty);
        }

        public Comment(string text)
            : base(ID3.Frame.Keys.Comment)
        {
            this.Initialize(0x00, new Data.ISO639_2(Sylloge.Data.ISO639_2.Code.ENG), string.Empty, text);
        }

        internal Comment(byte encoding, Sylloge.Data.ISO639_2 language, string shortDesc, string text)
            : base(ID3.Frame.Keys.Comment)
        {
            this.Initialize(encoding, language, shortDesc, text);
        }

        private Comment(byte encoding, byte[] language, string shortDesc, string text)
            : base(ID3.Frame.Keys.Comment)
        {
            this.Initialize(encoding, Sylloge.Data.ISO639_2.Parse(language), shortDesc, text);
        }

        public Comment(Frame other)
            : base(other)
        {
            if (other.ID != ID3.Frame.Keys.Comment) { throw new System.InvalidCastException("Frame ID must be equal to copy the data within it."); }
            Comment c = Comment.Parse(other);
            this.Description = c.Description;
            this.Encoding = c.Encoding;
            this.Language = c.Language;
            this.Value = c.Value;
        }

        public Comment(TextFrame other)
            : base(other)
        {
            if (other.ID != ID3.Frame.Keys.Comment) { throw new System.InvalidCastException("Frame ID must be equal to copy the data within it."); }
            this.Language = new Data.ISO639_2(Sylloge.Data.ISO639_2.Code.ENG);
        }

        public Comment(Comment other)
            : base(other)
        {
            this.Language = other.Language;
        }

        public override byte[] GenerateTag()
        {
            /* <Header for 'Comment', ID: "COMM"> 
            Text encoding           $xx (1 byte)
            Language                $xx xx xx (3 bytes)
            Short content descrip.  <text string according to encoding> (upto 0x00, plus 1 byte)
            The actual text         <full text string according to encoding>
            */
            byte[] pre_data = new byte[3];
            if (this.Language != null) { System.Buffer.BlockCopy(this.Language.Bytes, 0, pre_data, 0, 3); }
            return base.GenerateTagData(pre_data);
        }

        public void SetLanguage(Sylloge.Data.ISO639_2 lang)
        {
            if (lang == null) { throw new System.ArgumentNullException("lang"); }
            this.Language = lang;
            this.GenerateTag();
        }

        private void Initialize(byte encoding, Sylloge.Data.ISO639_2 language, string shortDesc, string text)
        {
            this.Language = language;
            this.Initialize(encoding, shortDesc, text);
            this.GenerateTag();
        }

        public static ID3.Frames.Comment Parse(Frame frame)
        {
            if (frame.ID != ID3.Frame.Keys.Comment) { throw new System.InvalidCastException("Frame ID must be equal to copy the data within it."); }
            Comment ret = new Comment(); // (Comment)frame;
            ret.Data = frame.Data;
            ret.Format = frame.Format;
            ret.Status = frame.Status;
            /* <Header for 'Comment', ID: "COMM"> 
            Text encoding           $xx (1 byte)
            Language                $xx xx xx (3 bytes)
            Short content descrip.  <text string according to encoding> (upto 0x00, plus 1 byte)
            The actual text         <full text string according to encoding> (the rest of the data)
            */
            List<byte> bdata = new List<byte>(ret.Data);
            ret.Encoding = bdata[0];
            ret.Language = Sylloge.Data.ISO639_2.Parse((new byte[] { bdata[1], bdata[2], bdata[3] }));
            System.Text.Encoding enc = ID3.Helper.GetEncoding(ret.Encoding);
            bdata.RemoveRange(0, 4);
            if (bdata[0] != Frame.EOL) {
                ret.Description = enc.GetString(bdata.ToArray());
                int idx = 0;
                for (idx = 0; idx < ret.Description.Length; idx++) {
                    if (ret.Description[idx] == '\0') { break; }
                }
                ret.Description = ret.Description.Substring(0, idx);
                int len = enc.GetByteCount(ret.Description);
                if ((len + 1) > bdata.Count) {
                    bdata.Clear();
                } else {
                    bdata.RemoveRange(0, len + 1);
                }
                if (enc.GetByteCount("A") > 1) {
                    // for multi-byte encodings
                    bdata.RemoveAt(0);
                }
            } else {
                bdata.RemoveAt(0);
            }
            if (bdata.Count > 0 && bdata[0] != Frame.EOL) {
                ret.Value = enc.GetString(bdata.ToArray());
                int idx = 0;
                for (; idx < ret.Value.Length; idx++) {
                    if (ret.Value[idx] == '\0') { break; }
                }
                ret.Value = ret.Value.Substring(0, idx);
            }
            return ret;
        }

        public static ID3.Frames.Comment Parse(byte[] data)
        {
            /* <Header for 'Comment', ID: "COMM"> 
            Text encoding           $xx (1 byte)
            Language                $xx xx xx (3 bytes)
            Short content descrip.  <text string according to encoding> (upto 0x00, plus 1 byte)
            The actual text         <full text string according to encoding> (the rest of the data)
            */
            List<byte> bdata = new List<byte>(data);
            byte[] lang = new byte[3];
            string sdesc = string.Empty;
            string text = string.Empty;
            byte benc = bdata[0];
            bdata.RemoveAt(0);
            System.Text.Encoding enc = ID3.Helper.GetEncoding(benc);
            System.Buffer.BlockCopy(bdata.ToArray(), 0, lang, 0, 3);
            bdata.RemoveRange(0, 3);
            if (bdata[0] != Frame.EOL) {
                sdesc = enc.GetString(bdata.ToArray());
                int idx = 0;
                for (idx = 0; idx < sdesc.Length; idx++) {
                    if (sdesc[idx] == '\0') { break; }
                }
                sdesc = sdesc.Substring(0, idx);
                int len = enc.GetByteCount(sdesc);
                if ((len + 1) > bdata.Count) {
                    bdata.Clear();
                } else {
                    bdata.RemoveRange(0, len + 1);
                }
                if (enc.GetByteCount("A") > 1) {
                    // for multi-byte encodings
                    bdata.RemoveAt(0);
                }
            } else {
                bdata.RemoveAt(0);
            }
            if (bdata[0] != Frame.EOL) {
                text = enc.GetString(bdata.ToArray());
                int idx = 0;
                for (; idx < text.Length; idx++) {
                    if (text[idx] == '\0') { break; }
                }
                text = text.Substring(0, idx);
            }
            return (new ID3.Frames.Comment(benc, lang, sdesc, text));
        }
    }
}