dagronf/BytesParser

A simple byte-oriented parser/writer. Read and write formatted values to/from binary blobs/files with ease!

BytesParser

A simple byte-oriented parser/writer. Read and write formatted values to/from binary blobs/files with ease!

Supports :-

• reading to/writing from a Data object, a file URL or an OutputStream object
• different endianness, even within the same file
• different string encodings, including multi-byte encodings like UInt32
• explicit string null-termination handling
• explicit endian handling for appropriate types (eg. Int32) so no unintential byte swaps.
• padding to byte boundaries

Online Documentation

Reading

The BytesParser class type provides the basic mechanism for reading and extracting useful information from binary data.

Using a BytesParser Object

let parser = BytesParser(data: <some data object>)

// The magic identifier for the file is an 8-byte ascii string (not null terminated)
let magic = try parser.readString(length: 8, encoding: .ascii)
assert("8BCBAFFE", magic)

// Read 12-character little-endian encoded WCS2 (UTF16) string 
let title = try parser.readUTF16String(.littleEndian, length: 12)
let length = try parser.readInt16(.littleEndian)
let offset = try parser.readInt32(.littleEndian)

Closure based

The closure based API hides some of the complexity of opening/closing a bytes file/blob.

Example

// Parsing a (local) crossword file
try BytesParser.parse(fileURL: url) { parser in
   let checksum: UInt16 = try parser.readInteger(.littleEndian)
   let magic = try parser.readString(length: 12, encoding: .ascii, lengthIncludesTerminator: true)
   assert(magic, "ACROSS&DOWN")

   let width = try parser.readInt8()
   let height = try parser.readInt8()

   let clueCount: UInt16 = try parser.readInteger(.littleEndian)
   ...
   let title = try parser.readStringNullTerminated(encoding: .ascii)
}

Writing

The BytesWriter class allows you to write formatted binary data to a file/data

The basic process is as follows :-

1. Create a new BytesWriter writer object with the appropriate initializer
2. Write to the writer object using the .write(...) methods
3. Call complete() on the writer to close any open file(s) and make the data ready. Failure to call .complete() may render your data unreadable.

• If using a BytesWriter to write to a data object, call the .data() method to retrieve the data. Calling .data() on a file-based writer will throw an error.

Using a BytesWriter Object

let data: [UInt8] = [0x20, 0x40, 0x60, 0x80]

let writer = try BytesWriter()
try writer.writeBytes(data)
writer.complete()

let myData = writer.data()

Closure based

The closure based API hides some of the complexity of opening/closing a writing destination. You won't need to call complete() at the end of an assemble block.

// Write to a Data object 
static func assemble(_ block: (BytesWriter) throws -> Void) throws -> Data

// Write to a file
static func assemble(fileURL: URL, _ block: (BytesWriter) throws -> Void) throws

Example

let message = "10. 好き 【す・き】 (na-adj) – likable; desirable"
try BytesWriter.assemble(fileURL: fileURL) { writer in
   // Write out a 'message' block
   // > Write out the block type identifier
   try writer.writeByte(0x78)
	// > Write message length (big-endian UInt32)
   try writer.writeUInt32(...message length in UTF32 chars..., .bigEndian)
   // > Write out the message in a big-endian, UTF32 format
   try writer.writeWide32String(message, encoding: .utf32BigEndian)

   // Write a 'data' block
	// > Write out the block type identifier
   try writer.writeByte(0x33)
   // > Write data length (big-endian UInt32)
   try writer.writeUInt32(...length of data..., .bigEndian)
   // > Write raw data as bytes
   try writer.writeData(...data...)
}

Notes

• Forward reading only (no rewinding!)
• Intentionally not thread safe (no calling from multiple different threads!)

License

MIT License

Copyright (c) 2023 Darren Ford

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.