SplitStreamCmdlet.cs

using Microsoft.PowerShell.Commands;
using PsUtils.Validation;
using System;
using System.IO;
using System.Linq;
using System.Management.Automation;
using Text = System.Text;

namespace PsUtils {

    [Cmdlet(VerbsCommon.Split, "Stream",
            DefaultParameterSetName = "Stream")]
    [OutputType(typeof(byte[]))]
    public class SplitStreamCmdlet : Cmdlet {

        #region Parameters

        [Parameter(Mandatory = true,
                   ParameterSetName = "Stream",
                   ValueFromPipeline = true,
                   Position = 1)]
        [Alias("FileStream")]
        public Stream Stream {
            get { return this.stream; }
            set { this.stream = value; }
        }
        private Stream stream;

        [Parameter(Mandatory = true,
                   ParameterSetName = "FilePath",
                   ValueFromPipeline = true,
                   Position = 1)]
        [ValidatePath()]
        public string Path {
            get { return this.path; }
            set { this.path = value; }
        }
        private string path;

        [Parameter(Mandatory = false,
                   Position = 2)]
        public string Delimiter {
            get { return this.delimiter; }
            set { this.delimiter = value; }
        }
        private string delimiter = Environment.NewLine;

        [Parameter(Mandatory = false)]
        public FileSystemCmdletProviderEncoding Encoding {
            get { return this.psEncoding; }
            set { this.psEncoding = value; }
        }
        private FileSystemCmdletProviderEncoding psEncoding = FileSystemCmdletProviderEncoding.Default;
        private Text.Encoding encoding;

        [Parameter(Mandatory = false)]
        public int BufferSize {
            get { return this.bufferSize; }
            set { this.bufferSize = value; }
        }
        private int bufferSize = 128 * 1024;

        #endregion

        #region Flow Functions

        protected override void BeginProcessing() {
            encoding = CmdletEncoding.Convert(Encoding);
        }

        protected override void ProcessRecord() {

            if (stream == null) {
                try {
                    stream = new FileStream(
                        Path,
                        FileMode.Open,
                        FileAccess.Read,
                        FileShare.Read,
                        BufferSize,
                        FileOptions.SequentialScan
                    );
                } catch (Exception e) {
                    WriteError(new ErrorRecord(e, "OpenStreamError", ErrorCategory.OpenError, Path));
                    return;
                }
            }

            // Discard encoding preamble
            var encPreamble = encoding.GetPreamble();
            if (encoding is Text.UTF8Encoding) {
                // by default utf8 without bom, check regardless
                encPreamble = Text.Encoding.UTF8.GetPreamble();
            }
            if (encPreamble.Length > 0) {
                var paLen = encPreamble.Length;
                var paBuf = new byte[paLen];
                stream.Read(paBuf, 0, paLen);
                if (encPreamble.SequenceEqual(paBuf)) {
                    WriteWarning(String.Format("BOM found ({0} bytes). It will be ignored.", paLen));
                } else {
                    stream.Seek(0, SeekOrigin.Begin);
                }
            }

            var delimBytes = encoding.GetBytes(Delimiter);

            foreach (var doc in StreamSplitter.Split(stream, delimBytes, bufferSize)) {
                WriteObject(doc);
            }

        }

        protected override void StopProcessing() {
            base.StopProcessing();
        }

        #endregion

    }

}