Class: Prism::Pack::Directive

Inherits:
Object
  • Object
show all
Defined in:
lib/prism/pack.rb

Overview

A directive in the pack template language.

Constant Summary collapse

ENDIAN_DESCRIPTIONS =

The descriptions of the various types of endianness.

{
  AGNOSTIC_ENDIAN: "agnostic",
  LITTLE_ENDIAN: "little-endian (VAX)",
  BIG_ENDIAN: "big-endian (network)",
  NATIVE_ENDIAN: "native-endian",
  ENDIAN_NA: "n/a"
}
SIGNED_DESCRIPTIONS =

The descriptions of the various types of signedness.

{
  UNSIGNED: "unsigned",
  SIGNED: "signed",
  SIGNED_NA: "n/a"
}
SIZE_DESCRIPTIONS =

The descriptions of the various types of sizes.

{
  SIZE_SHORT: "short",
  SIZE_INT: "int-width",
  SIZE_LONG: "long",
  SIZE_LONG_LONG: "long long",
  SIZE_8: "8-bit",
  SIZE_16: "16-bit",
  SIZE_32: "32-bit",
  SIZE_64: "64-bit",
  SIZE_P: "pointer-width"
}

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(version, variant, source, type, signed, endian, size, length_type, length) ⇒ Directive

Initialize a new directive with the given values.



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# File 'lib/prism/pack.rb', line 88

def initialize(version, variant, source, type, signed, endian, size, length_type, length)
  @version = version
  @variant = variant
  @source = source
  @type = type
  @signed = signed
  @endian = endian
  @size = size
  @length_type = length_type
  @length = length
end

Instance Attribute Details

#endian ⇒ Object (readonly)

The type of endianness of the directive.



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# File 'lib/prism/pack.rb', line 76

def endian
  @endian
end

#length ⇒ Object (readonly)

The length of this directive (used for integers).



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# File 'lib/prism/pack.rb', line 85

def length
  @length
end

#length_type ⇒ Object (readonly)

The length type of this directive (used for integers).



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# File 'lib/prism/pack.rb', line 82

def length_type
  @length_type
end

#signed ⇒ Object (readonly)

The type of signedness of the directive.



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# File 'lib/prism/pack.rb', line 73

def signed
  @signed
end

#size ⇒ Object (readonly)

The size of the directive.



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# File 'lib/prism/pack.rb', line 79

def size
  @size
end

#source ⇒ Object (readonly)

A byteslice of the source string that this directive represents.



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# File 'lib/prism/pack.rb', line 67

def source
  @source
end

#type ⇒ Object (readonly)

The type of the directive.



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# File 'lib/prism/pack.rb', line 70

def type
  @type
end

#variant ⇒ Object (readonly)

A symbol representing whether or not we are packing or unpacking.



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# File 'lib/prism/pack.rb', line 64

def variant
  @variant
end

#version ⇒ Object (readonly)

A symbol representing the version of Ruby.



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# File 'lib/prism/pack.rb', line 61

def version
  @version
end

Instance Method Details

#describe ⇒ Object

Provide a human-readable description of the directive.



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# File 'lib/prism/pack.rb', line 130

def describe
  case type
  when SPACE
    "whitespace"
  when COMMENT
    "comment"
  when INTEGER
    if size == SIZE_8
      base = "#{SIGNED_DESCRIPTIONS[signed]} #{SIZE_DESCRIPTIONS[size]} integer"
    else
      base = "#{SIGNED_DESCRIPTIONS[signed]} #{SIZE_DESCRIPTIONS[size]} #{ENDIAN_DESCRIPTIONS[endian]} integer"
    end
    case length_type
    when LENGTH_FIXED
      if length > 1
        base + ", x#{length}"
      else
        base
      end
    when LENGTH_MAX
      base + ", as many as possible"
    end
  when UTF8
    "UTF-8 character"
  when BER
    "BER-compressed integer"
  when FLOAT
    "#{SIZE_DESCRIPTIONS[size]} #{ENDIAN_DESCRIPTIONS[endian]} float"
  when STRING_SPACE_PADDED
    "arbitrary binary string (space padded)"
  when STRING_NULL_PADDED
    "arbitrary binary string (null padded, count is width)"
  when STRING_NULL_TERMINATED
    "arbitrary binary string (null padded, count is width), except that null is added with *"
  when STRING_MSB
    "bit string (MSB first)"
  when STRING_LSB
    "bit string (LSB first)"
  when STRING_HEX_HIGH
    "hex string (high nibble first)"
  when STRING_HEX_LOW
    "hex string (low nibble first)"
  when STRING_UU
    "UU-encoded string"
  when STRING_MIME
    "quoted printable, MIME encoding"
  when STRING_BASE64
    "base64 encoded string"
  when STRING_FIXED
    "pointer to a structure (fixed-length string)"
  when STRING_POINTER
    "pointer to a null-terminated string"
  when MOVE
    "move to absolute position"
  when BACK
    "back up a byte"
  when NULL
    "null byte"
  else
    raise
  end
end