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implement emscripten resize_heap

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This commit is contained in:
Mark McCaskey 2019-04-08 16:17:34 -07:00
parent 6578838acd
commit 50a22bcae2
2 changed files with 29 additions and 22 deletions
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49
lib/emscripten/src/memory.rs
View File

@ -1,7 +1,7 @@
use super::process::abort_with_message;
use libc::{c_int, c_void, memcpy, size_t};
use wasmer_runtime_core::{
units::{Pages, WASM_MAX_PAGES, WASM_PAGE_SIZE},
units::{Pages, WASM_MAX_PAGES, WASM_MIN_PAGES, WASM_PAGE_SIZE},
vm::Ctx,
};
@ -25,6 +25,14 @@ pub fn _emscripten_get_heap_size(ctx: &mut Ctx) -> u32 {
ctx.memory(0).size().bytes().0 as u32
}
// From emscripten implementation
fn align_up(mut val: usize, multiple: usize) -> usize {
if val % multiple > 0 {
val += multiple - val % multiple;
}
val
}
/// emscripten: _emscripten_resize_heap
/// Note: this function only allows growing the size of heap
pub fn _emscripten_resize_heap(ctx: &mut Ctx, requested_size: u32) -> u32 {
@ -32,29 +40,26 @@ pub fn _emscripten_resize_heap(ctx: &mut Ctx, requested_size: u32) -> u32 {
let current_memory_pages = ctx.memory(0).size();
let current_memory = current_memory_pages.bytes().0 as u32;
if requested_size > current_memory {
let remainder = (requested_size - current_memory) as usize % WASM_PAGE_SIZE;
let delta = {
let delta = (requested_size - current_memory) as usize / WASM_PAGE_SIZE;
if remainder != 0 {
delta + 1
} else {
delta
}
};
if current_memory_pages.0 as usize + delta > WASM_MAX_PAGES {
// TODO: handle this?
debug!("Can't exceed max pages");
return 0;
}
if let Ok(v) = ctx.memory(0).grow(Pages(delta as u32)) {
return v.0;
// implementation from emscripten
let mut new_size = usize::max(current_memory as usize, WASM_MIN_PAGES * WASM_PAGE_SIZE);
while new_size < requested_size as usize {
if new_size <= 0x2000_0000 {
new_size = align_up(new_size * 2, WASM_PAGE_SIZE);
} else {
new_size = usize::min(
align_up((3 * new_size + 0x8000_0000) / 4, WASM_PAGE_SIZE),
WASM_PAGE_SIZE * WASM_MAX_PAGES,
);
}
}
0
let amount_to_grow = (new_size - current_memory as usize) / WASM_PAGE_SIZE;
if let Ok(_pages_allocated) = ctx.memory(0).grow(Pages(amount_to_grow as u32)) {
debug!("{} pages allocated", _pages_allocated.0);
1
} else {
0
}
}
/// emscripten: getTotalMemory

2
lib/runtime-core/src/units.rs
View File

@ -6,6 +6,8 @@ use std::{
pub const WASM_PAGE_SIZE: usize = 65_536;
pub const WASM_MAX_PAGES: usize = 65_536;
// From emscripten resize_heap implementation
pub const WASM_MIN_PAGES: usize = 256;
/// Units of WebAssembly pages (as specified to be 65,536 bytes).
#[derive(Serialize, Deserialize, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]