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HASUMI Hitoshi
03a426ec8d
This patch extends the following String methods: * String#bit_set(offset, length, lsb_first: true) -> self * String#bit_set(range, lsb_first: true) -> self * String#bit_clear(offset, length, lsb_first: true) -> self * String#bit_clear(range, lsb_first: true) -> self * String#bit_flip(offset, length, lsb_first: true) -> self * String#bit_flip(range, lsb_first: true) -> self * String#bit_count(offset, length, lsb_first: true) -> Integer * String#bit_count(range, lsb_first: true) -> Integer Link: [Feature #22279]
39 lines
1.4 KiB
Plaintext
39 lines
1.4 KiB
Plaintext
Returns the number of set bits in +self+.
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With no arguments, counts over all bytes of +self+:
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"\x00".bit_count # => 0
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"\xFF".bit_count # => 8
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"\xAA".bit_count # => 4
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With +offset+ and +length+, counts only the +length+ bits beginning at
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zero-based bit +offset+; with a Range, counts the bits covered by +range+:
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data = "\xFF\x00\xF0"
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data.bit_count(0, 8) # => 8
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data.bit_count(8, 8) # => 0
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data.bit_count(0..7) # => 8
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data.bit_count(8...16) # => 0
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data.bit_count(16..) # => 4
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A region that extends beyond the end of +self+ is clamped to the bits that
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exist; a region that begins at or beyond the end counts zero:
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data.bit_count(16, 100) # => 4
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data.bit_count(100, 8) # => 0
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By default, bits within each byte are numbered from least-significant to
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most-significant. If +lsb_first+ is +false+, byte order is unchanged but bits
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within each byte are numbered from most-significant to least-significant.
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The numbering matters only when the region is not byte-aligned; the
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no-argument form is independent of it:
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"\xF0".bit_count(0, 4) # => 0
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"\xF0".bit_count(0, 4, lsb_first: false) # => 4
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The count is over the bytes of +self+ and is independent of string encoding.
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Raises +IndexError+ if +offset+ or a Range endpoint is negative.
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Raises +ArgumentError+ if +length+ is negative.
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Raises +ArgumentError+ if a bit position is too large to be represented.
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Raises +ArgumentError+ if +lsb_first+ is neither +true+ nor +false+.
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