Class: RMail::Parser::PushbackReader
- Inherits:
-
Object
- Object
- RMail::Parser::PushbackReader
- Defined in:
- lib/rmail/parser/pushbackreader.rb
Overview
A utility class for reading from an input source in an efficient chunked manner.
The idea is to read data in descent sized chunks (the default is 16k), but provide a way to “push back” some of the chunk if we read too much.
This class is useful only as a base class for other readers – e.g. a reader that parses MIME multipart documents, or a reader that understands one or more mailbox formats.
The typical RubyMail user will have no interest in this class. ;-)
Direct Known Subclasses
Instance Attribute Summary collapse
-
#chunk_size ⇒ Object
Retrieve the chunk size of this reader.
Class Method Summary collapse
-
.maybe_contains_re(boundary) ⇒ Object
Creates a regexp that’ll match the given boundary string in its entirely anywhere in a string, or any partial prefix of the boundary string so long as the match is anchored at the end of the string.
Instance Method Summary collapse
-
#eof ⇒ Object
Returns true if the next call to read_chunk will return nil.
-
#initialize(input) ⇒ PushbackReader
constructor
Create a PushbackReader and have it read from a given input source.
-
#pushback(string) ⇒ Object
Push a string back.
-
#read(size = @chunk_size) ⇒ Object
Read a chunk of input.
-
#read_chunk(size) ⇒ Object
Read a chunk of a given size.
-
#standard_read_chunk(size) ⇒ Object
The standard implementation of read_chunk.
Constructor Details
#initialize(input) ⇒ PushbackReader
Create a PushbackReader and have it read from a given input source.
The input source must either be a String or respond to the “read” method in the same way as an IO object.
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# File 'lib/rmail/parser/pushbackreader.rb', line 54 def initialize(input) unless defined? input.read(1) unless input.is_a?(String) raise ArgumentError, "input object not IO or String" end @pushback = input @input = nil else @pushback = nil @input = input end @chunk_size = 16384 end |
Instance Attribute Details
#chunk_size ⇒ Object
Retrieve the chunk size of this reader.
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# File 'lib/rmail/parser/pushbackreader.rb', line 131 def chunk_size @chunk_size end |
Class Method Details
.maybe_contains_re(boundary) ⇒ Object
Creates a regexp that’ll match the given boundary string in its entirely anywhere in a string, or any partial prefix of the boundary string so long as the match is anchored at the end of the string. This is useful for various subclasses of PushbackReader that need to know if a given input chunk might contain (or contain just the beginning of) an interesting string.
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# File 'lib/rmail/parser/pushbackreader.rb', line 159 def self.maybe_contains_re(boundary) left = Regexp.quote(boundary[0,1]) right = '' boundary[1..-1].each_byte { |ch| left << '(?:' left << Regexp.quote(ch.chr) right << '|\z)' } left + right end |
Instance Method Details
#eof ⇒ Object
Returns true if the next call to read_chunk will return nil.
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# File 'lib/rmail/parser/pushbackreader.rb', line 148 def eof @pushback.nil? and (@input.nil? or @input.eof) end |
#pushback(string) ⇒ Object
Push a string back. This will be the next chunk of data returned by #read.
Because it has not been needed and would compromise efficiency, only one chunk of data can be pushed back between successive calls to #read.
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# File 'lib/rmail/parser/pushbackreader.rb', line 124 def pushback(string) raise RMail::Parser::Error, 'You have already pushed a string back.' if @pushback @pushback = string end |
#read(size = @chunk_size) ⇒ Object
Read a chunk of input. The “size” argument is just a suggestion, and more or fewer bytes may be returned. If “size” is nil, then return the entire rest of the input stream.
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# File 'lib/rmail/parser/pushbackreader.rb', line 72 def read(size = @chunk_size) case size when nil chunk = nil while temp = read(@chunk_size) if chunk chunk << temp else chunk = temp end end chunk when Fixnum read_chunk(size) else raise ArgumentError, "Read size (#{size.inspect}) must be a Fixnum or nil." end end |
#read_chunk(size) ⇒ Object
Read a chunk of a given size. Unlike #read, #read_chunk must be passed a chunk size, and cannot be passed nil.
This is the function that should be re-defined in subclasses for specialized behavior.
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# File 'lib/rmail/parser/pushbackreader.rb', line 97 def read_chunk(size) standard_read_chunk(size) end |
#standard_read_chunk(size) ⇒ Object
The standard implementation of read_chunk. This can be convenient to call from derived classes when super() isn’t easy to use.
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# File 'lib/rmail/parser/pushbackreader.rb', line 104 def standard_read_chunk(size) unless size.is_a?(Fixnum) && size > 0 raise ArgumentError, "Read size (#{size.inspect}) must be greater than 0." end if @pushback chunk = @pushback @pushback = nil elsif ! @input.nil? chunk = @input.read(size) end return chunk end |