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8237514: Spec Clarification - ByteBuffer::alignmentOffset Spec

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Reviewed-by: alanb, psandoz
This commit is contained in:
Brian Burkhalter 2020-01-31 08:04:11 -08:00
parent 953fbd2e66
commit 7db8a1762f
4 changed files with 75 additions and 8 deletions
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15
src/java.base/share/classes/java/nio/X-Buffer.java.template
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@ -1871,19 +1871,20 @@ public abstract class $Type$Buffer
* Returns the memory address, pointing to the byte at the given index,
* modulo the given unit size.
*
* <p> The return value is non-negative, with {@code 0} indicating that the
* address of the byte at the index is aligned for the unit size, and a
* positive value that the address is misaligned for the unit size. If the
* address of the byte at the index is misaligned, the return value
* <p> The return value is non-negative in the range of {@code 0}
* (inclusive) up to {@code unitSize} (exclusive), with zero indicating
* that the address of the byte at the index is aligned for the unit size,
* and a positive value that the address is misaligned for the unit size.
* If the address of the byte at the index is misaligned, the return value
* represents how much the index should be adjusted to locate a byte at an
* aligned address. Specifically, the index should either be decremented by
* the return value, or incremented by the unit size minus the return value.
* Therefore given
* the return value if the latter is not greater than {@code index}, or be
* incremented by the unit size minus the return value. Therefore given
* <blockquote><pre>
* int value = alignmentOffset(index, unitSize)</pre></blockquote>
* then the identities
* <blockquote><pre>
* alignmentOffset(index - value, unitSize) == 0</pre></blockquote>
* alignmentOffset(index - value, unitSize) == 0, value &le; index</pre></blockquote>
* and
* <blockquote><pre>
* alignmentOffset(index + (unitSize - value), unitSize) == 0</pre></blockquote>