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Document the builtins

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Jakub Konka 2020-06-05 09:27:52 +02:00 committed by Andrew Kelley
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@ -7643,6 +7643,46 @@ mem.copy(u8, dest[0..byte_count], source[0..byte_count]);{#endsyntax#}</pre>
mem.set(u8, dest, c);{#endsyntax#}</pre>
{#header_close#}
{#header_open|@wasmMemorySize#}
<pre>{#syntax#}@wasmMemorySize(index: u32) u32{#endsyntax#}</pre>
<p>
This function returns the size of the Wasm memory identified by {#syntax#}index{#endsyntax#} as
an unsigned value in units of Wasm pages. Note that each Wasm page is 64KB in size.
</p>
<p>
This function is a low level intrinsic with no safety mechanisms usually useful for allocator
designers targeting Wasm. So unless you are writing a new allocator from scratch, you should use
something like {#syntax#}@import("std").heap.WasmAllocator{#endsyntax#}.
</p>
{#see_also|@wasmMemoryGrow#}
{#header_close#}
{#header_open|@wasmMemoryGrow#}
<pre>{#syntax#}@wasmMemoryGrow(index: u32, delta: u32) i32{#endsyntax#}</pre>
<p>
This function increases the size of the Wasm memory identified by {#syntax#}index{#endsyntax#} by
{#syntax#}delta{#endsyntax#} in units of unsigned number of Wasm pages. Note that each Wasm page
is 64KB in size. On success, returns previous memory size; on failure, if the allocation fails,
returns -1.
</p>
<p>
This function is a low level intrinsic with no safety mechanisms usually useful for allocator
designers targeting Wasm. So unless you are writing a new allocator from scratch, you should use
something like {#syntax#}@import("std").heap.WasmAllocator{#endsyntax#}.
</p>
{#code_begin|test#}
const std = @import("std");
const assert = std.debug.assert;
test "@wasmMemoryGrow" {
var prev = @wasmMemorySize(0);
assert(prev == @wasmMemoryGrow(0, 1));
assert(prev + 1 == @wasmMemorySize(0));
}
{#code_end#}
{#see_also|@wasmMemorySize#}
{#header_close#}
{#header_open|@mod#}
<pre>{#syntax#}@mod(numerator: T, denominator: T) T{#endsyntax#}</pre>
<p>