private static async Task Main(string[] args)
{
var rootCommand = new RootCommand {
Options.Regexp,
Options.File,
Options.PrintStatistics,
Options.Trim,
Options.MaxCount,
Options.OutputFile
};
rootCommand.Description = "Yet another sub-optimal grep implementation.";
rootCommand.Handler = CommandHandler.Create <string, FileInfo, bool, bool, int, FileInfo>(
async(regexp, file, statistics, trim, maxCount, outputFile) => {
var options = new GrepOptions(trim: trim, maxCount: maxCount, captureStatistics: statistics);
var result = outputFile == null
? await file.FullName.Grep(regexp,
r => WriteLine("[line {0}]{1}", r.LineNumber, r.Line.AsString()),
options)
: await GrepAndSaveOnFile(file, regexp, outputFile, options);
if (statistics)
{
WriteLine("------------------------");
WriteLine("------ STATISTICS ------");
WriteLine("------------------------");
WriteLine(result);
}
});
Environment.ExitCode = await rootCommand.InvokeAsync(args);
}
public LineReader(StreamReader haystack, GrepOptions options)
{
_buffer = new char[options.BufferSize];
_haystack = haystack;
_options = options;
_line = new Line(_buffer, options.Trim);
}
private static async Task <GrepStatistics> GrepAndSaveOnFile(
FileSystemInfo input, string regexp, FileInfo output, GrepOptions options)
{
await using var target = File.Create(output.FullName);
await using var writer = new StreamWriter(target, Encoding.UTF8)
{
NewLine = "\n", AutoFlush = true
};
return(await input.FullName.Grep(regexp, async r => await r.FlushInto(writer, autoFlush: false), options));
}
public static Func <Line, int, GrepResult> For(string needle, GrepOptions options)
{
// TODO: regexp support
return(NaiveStringContains(needle, options));
}
public static Func <Line, int, GrepResult> NaiveStringContains(string needle, GrepOptions options) =>
(line, lineIndex) => {
var limit = line.Length - needle.Length + 1;
if (limit < 1)
{
return(GrepResult.Failure(line));
}
// Store the first 2 characters of the needle
var c0 = needle[0];
var c1 = needle[1];
// Find the first occurrence of the first character
var possibleMatchStart = line.IndexOf(c0, startSearch: 0, limit);
while (possibleMatchStart != -1)
{
// Check if the following character is the same like the 2nd character of the needle
if (line[possibleMatchStart + 1] != c1)
{
possibleMatchStart = line.IndexOf(c0, ++possibleMatchStart, limit - possibleMatchStart);
continue;
}
var found = true;
// Looking for the rest of the needle (starting with the 3rd character)
for (var i = 2; i < needle.Length; i++)
{
if (line[possibleMatchStart + i] != needle[i])
{
found = false; break;
}
}
// If the whole word was found, return its index, otherwise try again
if (found)
{
return(GrepResult.Success(line, lineIndex + 1,
possibleMatchStart, possibleMatchStart + needle.Length - 1));
}
possibleMatchStart = line.IndexOf(c0, ++possibleMatchStart, limit - possibleMatchStart);
}
return(GrepResult.Failure(line));
};
