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**Note**: \Method +pread+ is different from other reading methods
in that it does not modify +self+ in any way;
thus, multiple threads may read safely from the same stream.
Reads up to +maxlen+ bytes from the stream,
beginning at 0-based byte offset +offset+;
returns a string containing the read bytes.
The returned string:
- Contains +maxlen+ bytes from the stream, if available;
otherwise contains all available bytes.
- Has encoding +Encoding::ASCII_8BIT+.
With only arguments +maxlen+ and +offset+ given,
returns a new string:
english = 'Hello' # Five 1-byte characters.
strio = StringIO.new(english)
strio.pread(3, 0) # => "Hel"
strio.pread(3, 2) # => "llo"
strio.pread(0, 0) # => ""
strio.pread(50, 0) # => "Hello"
strio.pread(50, 2) # => "llo"
strio.pread(50, 4) # => "o"
strio.pread(0, 0).encoding
# => #<Encoding:BINARY (ASCII-8BIT)>
russian = 'Привет' # Six 2-byte characters.
strio = StringIO.new(russian)
strio.pread(50, 0) # All 12 bytes.
# => "\xD0\x9F\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82"
strio.pread(3, 0) # => "\xD0\x9F\xD1"
strio.pread(3, 3) # => "\x80\xD0\xB8"
strio.pread(0, 0).encoding
# => #<Encoding:BINARY (ASCII-8BIT)>
japanese = 'こんにちは' # Five 3-byte characters.
strio = StringIO.new(japanese)
strio.pread(50, 0) # All 15 bytes.
# => "\xE3\x81\x93\xE3\x82\x93\xE3\x81\xAB\xE3\x81\xA1\xE3\x81\xAF"
strio.pread(6, 0) # => "\xE3\x81\x93\xE3\x82\x93"
strio.pread(1, 2) # => "\x93"
strio.pread(0, 0).encoding
# => #<Encoding:BINARY (ASCII-8BIT)>
Raises an exception if +offset+ is out-of-range:
strio = StringIO.new(english)
strio.pread(5, 50) # Raises EOFError: end of file reached
With string argument +out_string+ given:
- Reads as above.
- Overwrites the content of +out_string+ with the read bytes.
Examples:
out_string = 'Will be overwritten'
out_string.encoding # => #<Encoding:UTF-8>
result = StringIO.new(english).pread(50, 0, out_string)
result.__id__ == out_string.__id__ # => true
out_string # => "Hello"
out_string.encoding # => #<Encoding:BINARY (ASCII-8BIT)>
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