#String of Bytes

#Features

• Efficient byte-to-string conversion: Convert UTF-16 LE encoded bytes to strings
• Substring extraction: Extract substrings from byte arrays with offset and length
• Move semantics: Zero-copy conversion for performance-critical applications
• Cross-platform: Works across WASM, JavaScript, and native backends
• Unicode support: Full support for Unicode characters including emojis and surrogate pairs

#Installation

moon add illusory0x0/string_of_bytes

#API Reference

#string_of_bytes(bytes, byte_offset, byte_length)

• bytes: Bytes - The source byte array
• byte_offset: Int - Starting byte offset (must be even for UTF-16)
• byte_length: Int - Number of bytes to convert (must be even for UTF-16)

test "basic string conversion" {
  // "Hello" in UTF-16 LE encoding
  let bytes : Bytes = b"\x48\x00\x65\x00\x6C\x00\x6C\x00\x6F\x00"
  let result = @string_of_bytes.string_of_bytes(bytes, 0, bytes.length())
  inspect(result, content="Hello")
}

#Substring Extraction

test "substring extraction" {
  // "Hello World" but extract only "World"
  let bytes : Bytes = b"\x48\x00\x65\x00\x6C\x00\x6C\x00\x6F\x00\x20\x00\x57\x00\x6F\x00\x72\x00\x6C\x00\x64\x00"
  let result = @string_of_bytes.string_of_bytes(bytes, 12, 10) // Skip "Hello " (12 bytes), take "World" (10 bytes)
  inspect(result, content="World")
}

#Unicode and Emoji Support

test "unicode characters" {
  // Chinese characters "你好" in UTF-16 LE
  let bytes : Bytes = b"\x60\x4F\x7D\x59"
  let result = @string_of_bytes.string_of_bytes(bytes, 0, bytes.length())
  inspect(result, content="你好")
}

test "emoji support" {
  // Grinning face emoji 😀 with surrogate pairs
  let bytes : Bytes = b"\x3D\xD8\x00\xDE"
  let result = @string_of_bytes.string_of_bytes(bytes, 0, bytes.length())
  inspect(result, content="😀")
}

#move_bytes_to_string(bytes)

• bytes: Bytes - The source byte array (will be moved)

test "move semantics conversion" {
  let bytes : Bytes = b"\x48\x00\x65\x00\x6C\x00\x6C\x00\x6F\x00"
  let copied_bytes = copy_bytes(bytes)
  let result = @string_of_bytes.move_bytes_to_string(copied_bytes)
  inspect(result, content="Hello")
  // ⚠️ Do not use 'copied_bytes' after this point!
}

#Performance Optimization

test "large string performance" {
  // Create a larger byte array
  let byte_array : Array[Byte] = []
  for i = 0; i < 10; i = i + 1 {
    byte_array.push(0x41) // A
    byte_array.push(0x00)
    byte_array.push(0x42) // B  
    byte_array.push(0x00)
    byte_array.push(0x43) // C
    byte_array.push(0x00)
    byte_array.push(0x44) // D
    byte_array.push(0x00)
  }
  let bytes = Bytes::from_array(byte_array)
  let copied_bytes = copy_bytes(bytes)
  let result = @string_of_bytes.move_bytes_to_string(copied_bytes)
  inspect(result, content="ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD")
}

#Mixed Character Sets

test "mixed scripts" {
  // "Hi你" - English + Chinese
  let bytes : Bytes = b"\x48\x00\x69\x00\x60\x4F"
  let result = @string_of_bytes.string_of_bytes(bytes, 0, bytes.length())
  inspect(result, content="Hi你")
}

#Special Characters and Symbols

test "special characters" {
  // Mathematical symbols ∑∏∫∆
  let bytes : Bytes = b"\x11\x22\x0F\x22\x2B\x22\x06\x22"
  let result = @string_of_bytes.string_of_bytes(bytes, 0, bytes.length())
  inspect(result, content="∑∏∫∆")
}

test "currency symbols" {
  // Various currency symbols $€£¥₹
  let bytes : Bytes = b"\x24\x00\xAC\x20\xA3\x00\xA5\x00\xB9\x20"
  let result = @string_of_bytes.string_of_bytes(bytes, 0, bytes.length())
  inspect(result, content="$€£¥₹")
}

#Empty and Edge Cases

test "empty string" {
  let bytes : Bytes = b""
  let result = @string_of_bytes.string_of_bytes(bytes, 0, 0)
  inspect(result, content="")
}

test "null character" {
  let bytes : Bytes = b"\x00\x00"
  let result = @string_of_bytes.string_of_bytes(bytes, 0, 2)
  inspect(result, content="\u0000")
}

#UTF-16 Little Endian Format

• Each character is represented by 2 bytes (or 4 bytes for surrogate pairs)
• The least significant byte comes first
• For example, 'A' (U+0041) is encoded as [0x41, 0x00]

#Platform Support

• WASM/WASM-GC: Uses runtime memory manipulation for optimal performance
• JavaScript: Uses copying approach for compatibility
• Native: Uses efficient C-based memory operations

#Performance Considerations

• Use move_bytes_to_string() when you don't need the original bytes afterward
• Use string_of_bytes() when you need to preserve the original data or extract substrings
• Both functions are optimized for their respective use cases across all supported platforms

#License