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author | Matthew Dempsky <mdempsky@google.com> | 2021-04-21 00:12:02 -0700 |
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committer | Matthew Dempsky <mdempsky@google.com> | 2021-04-22 22:03:10 +0000 |
commit | 1da05eb0cebed9595ee0d326d9bd67edd046af0d (patch) | |
tree | 88bc7e65daba7b8e3661fd00e16be80dce9a428e /doc/go_spec.html | |
parent | 74059685fda0b60d539450ad6b7331ade838e90c (diff) | |
download | go-1da05eb0cebed9595ee0d326d9bd67edd046af0d.tar.gz go-1da05eb0cebed9595ee0d326d9bd67edd046af0d.zip |
spec: add unsafe.Add and unsafe.Slice
Updates #19367.
Updates #40481.
Change-Id: I578066ad68d2cd6bea50df1a534cf799e4404a7f
Reviewed-on: https://go-review.googlesource.com/c/go/+/312212
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Diffstat (limited to 'doc/go_spec.html')
-rw-r--r-- | doc/go_spec.html | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/doc/go_spec.html b/doc/go_spec.html index 13b8beb06c..bbcdd54b02 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -1,6 +1,6 @@ <!--{ "Title": "The Go Programming Language Specification", - "Subtitle": "Version of Apr 20, 2021", + "Subtitle": "Version of Apr 21, 2021", "Path": "/ref/spec" }--> @@ -6711,6 +6711,10 @@ type Pointer *ArbitraryType func Alignof(variable ArbitraryType) uintptr func Offsetof(selector ArbitraryType) uintptr 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 </pre> <p> @@ -6767,6 +6771,32 @@ Calls to <code>Alignof</code>, <code>Offsetof</code>, and <code>Sizeof</code> are compile-time constant expressions of type <code>uintptr</code>. </p> +<p> +The function <code>Add</code> adds <code>len</code> to <code>ptr</code> +and returns the updated pointer <code>unsafe.Pointer(uintptr(ptr) + uintptr(len))</code>. +The <code>len</code> argument must be of integer type or an untyped <a href="#Constants">constant</a>. +A constant <code>len</code> argument must be <a href="#Representability">representable</a> by a value of type <code>int</code>; +if it is an untyped constant it is given type <code>int</code>. +The rules for <a href="/pkg/unsafe#Pointer">valid uses</a> of <code>Pointer</code> still apply. +</p> + +<p> +The function <code>Slice</code> returns a slice whose underlying array starts at <code>ptr</code> +and whose length and capacity are <code>len</code>: +</p> + +<pre> +(*[len]ArbitraryType)(unsafe.Pointer(ptr))[:] +</pre> + +<p> +The <code>len</code> argument must be of integer type or an untyped <a href="#Constants">constant</a>. +A constant <code>len</code> argument must be non-negative and <a href="#Representability">representable</a> by a value of type <code>int</code>; +if it is an untyped constant it is given type <code>int</code>. +If <code>ptr</code> is <code>nil</code> or <code>len</code> is negative at run time, +a <a href="#Run_time_panics">run-time panic</a> occurs. +</p> + <h3 id="Size_and_alignment_guarantees">Size and alignment guarantees</h3> <p> |