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spec: document the new unsafe functions SliceData, String, and StringData

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For #53003.

Change-Id: If5d76c7b8dfcbcab919cad9c333c0225fc155859
Reviewed-on: https://go-review.googlesource.com/c/go/+/449537
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
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Robert Griesemer 2022-11-10 15:28:03 -08:00 committed by Gopher Robot
parent d092f597d7
commit c55d184151
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doc/go_spec.html
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@ -8006,6 +8006,9 @@ func Sizeof(variable ArbitraryType) uintptr
type IntegerType int // shorthand for an integer type; it is not a real type
func Add(ptr Pointer, len IntegerType) Pointer
func Slice(ptr *ArbitraryType, len IntegerType) []ArbitraryType
func SliceData(slice []ArbitraryType) *ArbitraryType
func String(ptr *byte, len IntegerType) string
func StringData(str string) *byte
</pre>
<!--
@ -8109,6 +8112,27 @@ or if <code>ptr</code> is <code>nil</code> and <code>len</code> is not zero,
a <a href="#Run_time_panics">run-time panic</a> occurs.
</p>
<p>
The function <code>SliceData</code> returns a pointer to the underlying array of the <code>slice</code> argument.
If the slice's capacity <code>cap(slice)</code> is not zero, that pointer is <code>&slice[:1][0]</code>.
If <code>slice</code> is <code>nil</code>, the result is <code>nil</code>.
Otherwise it is a non-<code>nil</code> pointer to an unspecified memory address.
</p>
<p>
The function <code>String</code> returns a <code>string</code> value whose underlying bytes start at
<code>ptr</code> and whose length is <code>len</code>.
The same requirements apply to the <code>ptr</code> and <code>len</code> argument as in the function
<code>Slice</code>. If <code>len</code> is zero, the result is the empty string <code>""</code>.
Since Go strings are immutable, the bytes passed to <code>String</code> must not be modified afterwards.
</p>
<p>
The function <code>StringData</code> returns a pointer to the underlying bytes of the <code>str</code> argument.
For an empty string the return value is unspecified, and may be <code>nil</code>.
Since Go strings are immutable, the bytes returned by <code>StringData</code> must not be modified.
</p>
<h3 id="Size_and_alignment_guarantees">Size and alignment guarantees</h3>
<p>