Class: EBNF::LL1::Scanner
- Inherits:
-
StringScanner
- Object
- StringScanner
- EBNF::LL1::Scanner
- Defined in:
- lib/ebnf/ll1/scanner.rb
Overview
Overload StringScanner with file operations
-
Reloads scanner as required until EOF.
-
Loads to a high-water and reloads when remaining size reaches a low-water.
FIXME: Only implements the subset required by the Lexer for now.
Constant Summary collapse
- HIGH_WATER =
Hopefully large enough to deal with long multi-line comments
512 * 1024
- LOW_WATER =
4 * 1024
Instance Attribute Summary collapse
- #input ⇒ IO, StringIO readonly
Instance Method Summary collapse
-
#ensure_buffer_full ⇒ Object
Ensures that the input buffer is full to the high water mark, or end of file.
-
#eos? ⇒ Boolean
Returns true if the scan pointer is at the end of the string.
-
#initialize(input, options = {}) ⇒ Scanner
constructor
Create a scanner, from an IO or String.
-
#rest ⇒ String
Returns the “rest” of the line, or the next line if at EOL (i.e. everything after the scan pointer).
-
#scan(pattern) ⇒ String
Tries to match with ‘pattern` at the current position.
-
#skip(pattern) ⇒ Object
Attempts to skip over the given ‘pattern` beginning with the scan pointer.
-
#terminate ⇒ Object
Set the scan pointer to the end of the string and clear matching data.
Constructor Details
#initialize(input, options = {}) ⇒ Scanner
Create a scanner, from an IO or String
28 29 30 31 32 33 34 35 36 37 38 |
# File 'lib/ebnf/ll1/scanner.rb', line 28 def initialize(input, = {}) = .merge(high_water: HIGH_WATER, low_water: LOW_WATER) if input.respond_to?(:read) @input = input super("") feed_me else super(encode_utf8 input.to_s) end end |
Instance Attribute Details
#input ⇒ IO, StringIO (readonly)
18 19 20 |
# File 'lib/ebnf/ll1/scanner.rb', line 18 def input @input end |
Instance Method Details
#ensure_buffer_full ⇒ Object
Ensures that the input buffer is full to the high water mark, or end of file. Useful when matching tokens that may be longer than the low water mark
102 103 104 105 106 107 108 109 110 |
# File 'lib/ebnf/ll1/scanner.rb', line 102 def ensure_buffer_full # Read up to high-water mark ensuring we're at an end of line if @input && !@input.eof? diff = [:high_water] - rest_size string = encode_utf8(@input.read(diff)) string << encode_utf8(@input.gets) unless @input.eof? self << string if string end end |
#eos? ⇒ Boolean
Returns true if the scan pointer is at the end of the string
66 67 68 69 |
# File 'lib/ebnf/ll1/scanner.rb', line 66 def eos? feed_me super end |
#rest ⇒ String
Returns the “rest” of the line, or the next line if at EOL (i.e. everything after the scan pointer). If there is no more data (eos? = true), it returns “”.
45 46 47 48 |
# File 'lib/ebnf/ll1/scanner.rb', line 45 def rest feed_me encode_utf8 super end |
#scan(pattern) ⇒ String
Tries to match with ‘pattern` at the current position.
If there is a match, the scanner advances the “scan pointer” and returns the matched string. Otherwise, the scanner returns nil.
If the scanner begins with the multi-line start expression
95 96 97 98 |
# File 'lib/ebnf/ll1/scanner.rb', line 95 def scan(pattern) feed_me encode_utf8 super end |
#skip(pattern) ⇒ Object
Attempts to skip over the given ‘pattern` beginning with the scan pointer. If it matches, the scan pointer is advanced to the end of the match, and the length of the match is returned. Otherwise, `nil` is returned.
similar to ‘scan`, but without returning the matched string.
57 58 59 60 |
# File 'lib/ebnf/ll1/scanner.rb', line 57 def skip(pattern) feed_me super end |
#terminate ⇒ Object
Set the scan pointer to the end of the string and clear matching data
73 74 75 76 |
# File 'lib/ebnf/ll1/scanner.rb', line 73 def terminate feed_me super end |