Fmbm.CCFile 1.0.1

CCFile

Read, write and serialize to file - simply and robustly.

Features:

• Thread-safe reads and writes (similar to File.ReadAllText) plus serialization.
• Convenient, thread-safe ReadOrWrite method for initialization (similar to ConcurrentDictionary.GetOrAdd).
• Thread-safe Modify method.
• Automatically creates a backup of existing files.
• Supports additional archiving or versioning of files.
• Reduces likelihood of partial writes and detects them if they do happen.

Warning: Although intended to be robust, this is a first release and so may not be as reliable as hoped. It may have dreadful bugs.

For Me, By Me (FMBM)

This was created primarily for use by the author. It has only been tested in limited environments. It is intended for getting ad-hoc applications up and running quickly. It probably is not suitable for complex, production, nor evolving projects. (The name is inspired by the Fubu, For Us, By Us, project, but there is no other connection.)

Contents

• CCFile Basic Usage
• CCValue Basic Usage
• Symbolic Links
• ReadOrWrite
• Modify
• Exists and Delete
• Archive
• Interfaces
• Files Check
• Name

CCFile Basic Usage

CCFile supports Read, Write, Modify, and ReadOrWrite for each of bytes[], string and 'values'.

This shows a 'value' being written to disk and then read back as a string, as a byte[], and as a 'value':

using Fmbm.IO;

// Create new CCFile
var ccfile = new CCFile("CCFile_Sample.txt");

// Serialize a list to disk
ccfile.WriteValue(new List<string> { "Apple", "Banana", "Cherry" });

// Read file contents as text
Console.WriteLine(ccfile.ReadText());

// Read file contents as bytes
Console.WriteLine(ccfile.ReadBytes().Length);

// Read file contents as a value
Console.WriteLine(ccfile.ReadValue<List<string>>().Last());

// OUTPUT:
// [
//   "Apple",
//   "Banana",
//   "Cherry"
// ]
// 27
// Cherry

CCValue Basic Usage

CCValue is a strongly typed version that supports Read, Write, Modify, and ReadOrWrite but only for 'values'.

This shows a value being written to disk and then read back as a 'value':

using Fmbm.IO;

var ccvalue = new CCValue<List<string>>("CCFile_Sample.txt");

// Serialize a list to disk
ccvalue.Write(new List<string> { "Apple", "Banana", "Cherry" });

// Deserialize file and get last element of list
Console.WriteLine(ccvalue.Read().Last());

// OUTPUT:
// Cherry

Symbolic Links

The file's FullName is used as the key for synchronizing access it. This should work correctly across different instances of CCFile that access the same file even if they are created with different relative paths or with different casing. However if a file is accessible though a symbolic link then synchronization may not work as expected if different instances of CCFile use the symbolic link inconsistently. E.g. if CCFiles are instantiated with /apple/banana/cherry/thefile.txt and /apple/sldir/thefile.txt then access to thefile.txt will not be thread-safe.

ReadOrWrite

ReadOrWrite is a thread-safe and convenient way to set the initial content of the file if the file does not already exist.

If the file does not already exist then the getInitialValue argument is called and the result is written to the file. If the file already exists then ReadOrWrite will return the existing file content.

using Fmbm.IO;

var ccfile = new CCFile("CCFile_Sample.txt");

// If file does not already exist 'getInitialValue' will be called:
var result1 = ccfile.ReadOrWriteText(() => "Apple");
Console.WriteLine(result1);

// 'getInitialValue' not called because file now exists.
var result2 = ccfile.ReadOrWriteText(() => "Banana");
Console.WriteLine(result2);

// OUTPUT:
// Apple
// Apple

Modify

Modify provides a thread-safe way to change the contents of the file.

using Fmbm.IO;

var ccvalue = new CCValue<string[]>("CCFile_Sample.txt");

ccvalue.Write(new[] { "Cherry", "Banana", "Apple" });

Console.WriteLine(String.Join(", ", ccvalue.Read()));

ccvalue.Modify(fruit =>
{
    Array.Sort(fruit);
    return fruit;
});

Console.WriteLine(String.Join(", ", ccvalue.Read()));

// OUTPUT:
// Cherry, Banana, Apple
// Apple, Banana, Cherry

Exists and Delete

Exists indicates whether the file exists.

Delete deletes the file and any backup or temporary file.

using Fmbm.IO;

var ccfile = new CCFile("CCFile_Sample.txt");
Console.WriteLine(ccfile.Exists);

ccfile.WriteText("");
Console.WriteLine(ccfile.Exists);

ccfile.Delete();
Console.WriteLine(ccfile.Exists);

// OUTPUT:
// False
// True
// False

Archive

The constructors of CCFile and CCValue take an optional archive parameter. archive is an Action that takes a string and a nullable string.

archive is called when any write completes (including ReadOrWrite and Modify). The first argument is the path to the new or updated file. The second argument is the path to the backup file, or null if there is no backup file.

using Fmbm.IO;

void Archive(string filePath, string? backPath)
{
    var after = File.ReadAllText(filePath);
    var before = backPath is null ? "<none>" : File.ReadAllText(backPath);

    Console.Write($@"
** File Updated **
==================
Before: {before}
After: {after}
");
}

var ccvalue =
    new CCValue<Dictionary<string, string>>("CCFile_Sample.txt", Archive);

ccvalue.ReadOrWrite(() =>
    new Dictionary<string, string> { { "A", "Apple" }, { "B", "Banana" } });

ccvalue.Modify(fruit =>
{
    fruit.Add("C", "Cherry");
    return fruit;
});

// OUTPUT:

// ** File Updated **
// ==================
// Before: <none>
// After: {
//   "A": "Apple",
//   "B": "Banana"
// }

// ** File Updated **
// ==================
// Before: {
//   "A": "Apple",
//   "B": "Banana"
// }
// After: {
//   "A": "Apple",
//   "B": "Banana",
//   "C": "Cherry"
// }

Interfaces

CCFile implements the interface ICCFile which extends: ICCBinary, ICCText and ICCGeneric

CCValue implements the interface ICCValue

ICCBinary, ICCText, ICCGeneric and ICCValue each defines Exists and defines their own versions of:

• Read
• Write
• ReadOrWrite
• Modify

Files Check

The normal write process is:

• New data is written to the temporary path.
• The existing file is moved to the backup path overwriting any existing backup.
• The temporary file is moved to the file path.
• Archive is called.

The temporary path is the file path with a .tmp extension appended.

The backup path is the file path with a .bak extension appended.

Before reads and writes CCFile checks to determine if a previous write might be incomplete. If the check fails then a CCFileException is thrown.

This table shows the write steps and shows the combinations of files that would fail the check for an incomplete write and cause a CCFileException to be thrown.

Lower case f, b: existing file.
Upper case T, F, B: updated file.
┌──────┬──────┬──────┬─────────────────────────────────────────────────────┐
│ .tmp │ file │ .bak │                                                     │
├──────┴──────┴──────┴─────────────────────────────────────────────────────┤
│                                                                          │
│                              First write                                 │
├──────┬──────┬──────┬─────────────────────────────────────────────────────┤
│      │      │      │ Pass: initial state.                                │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│  T   │      │      │ Fail: .tmp may or may no be complete.               │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│      │  F   │      │ Pass: expected state after first write.             │
├──────┴──────┴──────┴─────────────────────────────────────────────────────┤
│                                                                          │
│                              Second write                                │
├──────┬──────┬──────┬─────────────────────────────────────────────────────┤
│      │  f   │      │ Pass: initial state.                                │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│  T   │  f   │      │ Fail: .tmp may or may not be complete.              │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│  T   │      │  B   │ Fail: but both files should be complete.            │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│      │  F   │  B   │ Pass: expected state after second write.            │
├──────┴──────┴──────┴─────────────────────────────────────────────────────┤
│                                                                          │
│                              Subsequent writes:                          │
├──────┬──────┬──────┬─────────────────────────────────────────────────────┤
│      │  f   │  b   │ Pass: initial state.                                │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│  T   │  f   │  b   │ Fail: .tmp may or may not be complete.              │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│  T   │      │  B   │ Fail: but both files should be complete.            │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│      │  F   │  B   │ Pass: expected state after subsequent writes.       │
├──────┴──────┴──────┴─────────────────────────────────────────────────────┤
│                                                                          │
│            If archive function moves or deletes the .bck file:           │
├──────┬──────┬──────┬─────────────────────────────────────────────────────┤
│      │  f   │      │ Pass: initial state.                                │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│  T   │  f   │      │ Fail: .tmp may or may not be complete.              │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│  T   │      │  B   │ Fail: but both files should be complete.            │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│      │  F   │  B   │ Pass: before archive is called.                     │
├──────┼──────┼──────┼─────────────────────────────────────────────────────┤
│      │  F   │      │ Pass: normal after archive moves/deletes .bak.      │
├──────┴──────┴──────┼─────────────────────────────────────────────────────┤
│                    │                                                     │
│ Other combinations │                  ¯\_(ツ)_/¯                         │
└────────────────────┴─────────────────────────────────────────────────────┘

Why is it called 'CCFile'?

Because it's a carbon copying, conveniently converting, concurrency conscious, crash catching file wrapper.