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Improving the passStringToWasm function

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This commit is contained in:
Pauan 2019-08-23 01:06:21 +02:00
parent e39e8501db
commit 5581cdf656
1 changed files with 46 additions and 26 deletions
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72
crates/cli-support/src/js/mod.rs
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@ -805,6 +805,30 @@ impl<'a> Context<'a> {
self.global("let WASM_VECTOR_LEN = 0;");
}
fn expose_encode_as_ascii(&mut self) {
if !self.should_write_global("encode_as_ascii") {
return;
}
self.expose_uint8_memory();
self.global("
function encodeAsAscii(arg, ptr, len) {
let offset = 0;
const mem = getUint8Memory();
for (; offset < len; offset++) {
const code = arg.charCodeAt(offset);
if (code > 0x7F) break;
mem[ptr + offset] = code;
}
return offset;
}
");
}
fn expose_pass_string_to_wasm(&mut self) -> Result<(), Error> {
if !self.should_write_global("pass_string_to_wasm") {
return Ok(());
@ -846,6 +870,8 @@ impl<'a> Context<'a> {
self.expose_text_encoder()?;
self.expose_uint8_memory();
self.expose_encode_as_ascii();
// A fast path that directly writes char codes into WASM memory as long
// as it finds only ASCII characters.
//
@ -856,19 +882,11 @@ impl<'a> Context<'a> {
// expensive in mainstream engines than staying in the JS, and
// charCodeAt on ASCII strings is usually optimised to raw bytes.
let start_encoding_as_ascii = format!(
"
"\
{}
let size = arg.length;
let ptr = wasm.__wbindgen_malloc(size);
let offset = 0;
{{
const mem = getUint8Memory();
for (; offset < arg.length; offset++) {{
const code = arg.charCodeAt(offset);
if (code > 0x7F) break;
mem[ptr + offset] = code;
}}
}}
const len = arg.length;
let ptr = wasm.__wbindgen_malloc(len);
const offset = encodeAsAscii(arg, ptr, len);
",
debug
);
@ -876,10 +894,13 @@ impl<'a> Context<'a> {
// The first implementation we have for this is to use
// `TextEncoder#encode` which has been around for quite some time.
let use_encode = format!(
"
"\
{}
if (offset !== arg.length) {{
const buf = cachedTextEncoder.encode(arg.slice(offset));
if (offset !== len) {{
if (offset !== 0) {{
arg = arg.slice(offset);
}}
const buf = cachedTextEncoder.encode(arg);
ptr = wasm.__wbindgen_realloc(ptr, size, size = offset + buf.length);
getUint8Memory().set(buf, ptr + offset);
offset += buf.length;
@ -894,11 +915,13 @@ impl<'a> Context<'a> {
// newer and isn't implemented everywhere yet. It's more efficient,
// however, becaues it allows us to elide an intermediate allocation.
let use_encode_into = format!(
"
"\
{}
if (offset !== arg.length) {{
arg = arg.slice(offset);
ptr = wasm.__wbindgen_realloc(ptr, size, size = offset + arg.length * 3);
if (offset !== len) {{
if (offset !== 0) {{
arg = arg.slice(offset);
}}
ptr = wasm.__wbindgen_realloc(ptr, size, size = offset + len * 3);
const view = getUint8Memory().subarray(ptr + offset, ptr + size);
const ret = cachedTextEncoder.encodeInto(arg, view);
{}
@ -909,7 +932,7 @@ impl<'a> Context<'a> {
",
start_encoding_as_ascii,
if self.config.debug {
"if (ret.read != arg.length) throw new Error('failed to pass whole string');"
"if (ret.read != len) throw new Error('failed to pass whole string');"
} else {
""
},
@ -932,12 +955,9 @@ impl<'a> Context<'a> {
self.require_internal_export("__wbindgen_realloc")?;
self.global(&format!(
"
let passStringToWasm;
if (typeof cachedTextEncoder.encodeInto === 'function') {{
passStringToWasm = function(arg) {{ {} }};
}} else {{
passStringToWasm = function(arg) {{ {} }};
}}
const passStringToWasm = (typeof cachedTextEncoder.encodeInto === 'function'
? function (arg) {{ {} }}
: function (arg) {{ {} }});
",
use_encode_into, use_encode,
));