# class Prism::Source

This represents a source of Ruby code that has been parsed. It is used in conjunction with locations to allow them to resolve line numbers and source ranges.

### Attributes

offsets [R]

The list of newline byte offsets in the source code.

source [R]

The source code that this source object represents.

start_line [R]

The line number where this source starts.

### Public Class Methods

for (source, start_line = 1, offsets = [])
Source

    # File lib/prism/parse_result.rb, line 12
    def self.for(source, start_line = 1, offsets = [])
      if source.ascii_only?
        ASCIISource.new(source, start_line, offsets)
      elsif source.encoding == Encoding::BINARY
        source.force_encoding(Encoding::UTF_8)

        if source.valid_encoding?
          new(source, start_line, offsets)
        else
          # This is an extremely niche use case where the file is marked as
          # binary, contains multi-byte characters, and those characters are not
          # valid UTF-8. In this case we'll mark it as binary and fall back to
          # treating everything as a single-byte character. This _may_ cause
          # problems when asking for code units, but it appears to be the
          # cleanest solution at the moment.
          source.force_encoding(Encoding::BINARY)
          ASCIISource.new(source, start_line, offsets)
        end
      else
        new(source, start_line, offsets)
      end
    end

Create a new source object with the given source code. This method should be used instead of ‘new` and it will return either a `Source` or a specialized and more performant `ASCIISource` if no multibyte characters are present in the source code.

new (source, start_line = 1, offsets = [])
Source

    # File lib/prism/parse_result.rb, line 45
    def initialize(source, start_line = 1, offsets = [])
      @source = source
      @start_line = start_line # set after parsing is done
      @offsets = offsets # set after parsing is done
    end

Create a new source object with the given source code.

### Public Instance Methods

character_column (byte_offset)
Source

    # File lib/prism/parse_result.rb, line 97
    def character_column(byte_offset)
      character_offset(byte_offset) - character_offset(line_start(byte_offset))
    end

Return the column number in characters for the given byte offset.

character_offset (byte_offset)
Source

    # File lib/prism/parse_result.rb, line 92
    def character_offset(byte_offset)
      (source.byteslice(0, byte_offset) or raise).length
    end

Return the character offset for the given byte offset.

code_units_cache (encoding)
Source

    # File lib/prism/parse_result.rb, line 125
    def code_units_cache(encoding)
      CodeUnitsCache.new(source, encoding)
    end

Generate a cache that targets a specific encoding for calculating code unit offsets.

code_units_column (byte_offset, encoding)
Source

    # File lib/prism/parse_result.rb, line 131
    def code_units_column(byte_offset, encoding)
      code_units_offset(byte_offset, encoding) - code_units_offset(line_start(byte_offset), encoding)
    end

Returns the column number in code units for the given encoding for the given byte offset.

code_units_offset (byte_offset, encoding)
Source

    # File lib/prism/parse_result.rb, line 113
    def code_units_offset(byte_offset, encoding)
      byteslice = (source.byteslice(0, byte_offset) or raise).encode(encoding, invalid: :replace, undef: :replace)

      if encoding == Encoding::UTF_16LE || encoding == Encoding::UTF_16BE
        byteslice.bytesize / 2
      else
        byteslice.length
      end
    end

Returns the offset from the start of the file for the given byte offset counting in code units for the given encoding.

This method is tested with UTF-8, UTF-16, and UTF-32. If there is the concept of code units that differs from the number of characters in other encodings, it is not captured here.

We purposefully replace invalid and undefined characters with replacement characters in this conversion. This happens for two reasons. First, it’s possible that the given byte offset will not occur on a character boundary. Second, it’s possible that the source code will contain a character that has no equivalent in the given encoding.

column (byte_offset)
Source

    # File lib/prism/parse_result.rb, line 87
    def column(byte_offset)
      byte_offset - line_start(byte_offset)
    end

Return the column number for the given byte offset.

encoding ()
Source

    # File lib/prism/parse_result.rb, line 53
    def encoding
      source.encoding
    end

Returns the encoding of the source code, which is set by parameters to the parser or by the encoding magic comment.

line (byte_offset)
Source

    # File lib/prism/parse_result.rb, line 70
    def line(byte_offset)
      start_line + find_line(byte_offset)
    end

Binary search through the offsets to find the line number for the given byte offset.

line_end (byte_offset)
Source

    # File lib/prism/parse_result.rb, line 82
    def line_end(byte_offset)
      offsets[find_line(byte_offset) + 1] || source.bytesize
    end

Returns the byte offset of the end of the line corresponding to the given byte offset.

line_start (byte_offset)
Source

    # File lib/prism/parse_result.rb, line 76
    def line_start(byte_offset)
      offsets[find_line(byte_offset)]
    end

Return the byte offset of the start of the line corresponding to the given byte offset.

lines ()
Source

    # File lib/prism/parse_result.rb, line 58
    def lines
      source.lines
    end

Returns the lines of the source code as an array of strings.

slice (byte_offset, length)
Source

    # File lib/prism/parse_result.rb, line 64
    def slice(byte_offset, length)
      source.byteslice(byte_offset, length) or raise
    end

Perform a byteslice on the source code using the given byte offset and byte length.

### Private Instance Methods

find_line (byte_offset)
Source

    # File lib/prism/parse_result.rb, line 139
    def find_line(byte_offset)
      left = 0
      right = offsets.length - 1

      while left <= right
        mid = left + (right - left) / 2
        return mid if (offset = offsets[mid]) == byte_offset

        if offset < byte_offset
          left = mid + 1
        else
          right = mid - 1
        end
      end

      left - 1
    end

Binary search through the offsets to find the line number for the given byte offset.