Class: PDF::Reader::Buffer
- Inherits:
-
Object
- Object
- PDF::Reader::Buffer
- Defined in:
- lib/pdf/reader/buffer.rb
Overview
A string tokeniser that recognises PDF grammar. When passed an IO stream or a string, repeated calls to token() will return the next token from the source.
This is very low level, and getting the raw tokens is not very useful in itself.
This will usually be used in conjunction with PDF:Reader::Parser, which converts the raw tokens into objects we can work with (strings, ints, arrays, etc)
Constant Summary collapse
- TOKEN_WHITESPACE =
[0x00, 0x09, 0x0A, 0x0C, 0x0D, 0x20]
- LEFT_PAREN =
some strings for comparissons. Declaring them here avoids creating new strings that need GC over and over
"("
- LESS_THAN =
"<"
- STREAM =
"stream"
- ID =
"ID"
- FWD_SLASH =
"/"
Instance Attribute Summary collapse
-
#pos ⇒ Object
readonly
Returns the value of attribute pos.
Instance Method Summary collapse
-
#empty? ⇒ Boolean
return true if there are no more tokens left.
-
#find_first_xref_offset ⇒ Object
return the byte offset where the first XRef table in th source can be found.
-
#initialize(io, opts = {}) ⇒ Buffer
constructor
Creates a new buffer.
-
#read(bytes, opts = {}) ⇒ Object
return raw bytes from the underlying IO stream.
-
#token ⇒ Object
return the next token from the source.
Constructor Details
#initialize(io, opts = {}) ⇒ Buffer
Creates a new buffer.
Params:
io - an IO stream or string with the raw data to tokenise
options:
:seek - a byte offset to seek to before starting to tokenise
:content_stream - set to true if buffer will be tokenising a
content stream. Defaults to false
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# File 'lib/pdf/reader/buffer.rb', line 63 def initialize (io, opts = {}) @io = io @tokens = [] @in_content_stream = opts[:content_stream] @io.seek(opts[:seek]) if opts[:seek] @pos = @io.pos end |
Instance Attribute Details
#pos ⇒ Object (readonly)
Returns the value of attribute pos.
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# File 'lib/pdf/reader/buffer.rb', line 49 def pos @pos end |
Instance Method Details
#empty? ⇒ Boolean
return true if there are no more tokens left
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# File 'lib/pdf/reader/buffer.rb', line 74 def empty? prepare_tokens if @tokens.size < 3 @tokens.empty? end |
#find_first_xref_offset ⇒ Object
return the byte offset where the first XRef table in th source can be found.
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# File 'lib/pdf/reader/buffer.rb', line 125 def find_first_xref_offset check_size_is_non_zero @io.seek(-1024, IO::SEEK_END) rescue @io.seek(0) data = @io.read(1024) # the PDF 1.7 spec (section #3.4) says that EOL markers can be either \r, \n, or both. lines = data.split(/[\n\r]+/).reverse eof_index = lines.index { |l| l.strip[/^%%EOF/] } raise MalformedPDFError, "PDF does not contain EOF marker" if eof_index.nil? raise MalformedPDFError, "PDF EOF marker does not follow offset" if eof_index >= lines.size-1 lines[eof_index+1].to_i end |
#read(bytes, opts = {}) ⇒ Object
return raw bytes from the underlying IO stream.
bytes - the number of bytes to read
options:
:skip_eol - if true, the IO stream is advanced past a CRLF or LF that
is sitting under the io cursor.
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# File 'lib/pdf/reader/buffer.rb', line 89 def read(bytes, opts = {}) reset_pos if opts[:skip_eol] @io.seek(-1, IO::SEEK_CUR) str = @io.read(2) if str.nil? return nil elsif str == "\r\n" # do nothing elsif str[0,1] == "\n" @io.seek(-1, IO::SEEK_CUR) else @io.seek(-2, IO::SEEK_CUR) end end bytes = @io.read(bytes) save_pos bytes end |
#token ⇒ Object
return the next token from the source. Returns a string if a token is found, nil if there are no tokens left.
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# File 'lib/pdf/reader/buffer.rb', line 114 def token reset_pos prepare_tokens if @tokens.size < 3 merge_indirect_reference prepare_tokens if @tokens.size < 3 @tokens.shift end |