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Add syscall/js.copyBytesToJS support #933

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Merged
merged 1 commit into from
Mar 1, 2020
+19 −0
Merged

Add syscall/js.copyBytesToJS support #933

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19 changes: 19 additions & 0 deletions targets/wasm_exec.js
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Original file line number Diff line number Diff line change
Expand Up @@ -319,6 +319,25 @@
//"syscall/js.valueInstanceOf": (sp) => {
// mem().setUint8(sp + 24, loadValue(sp + 8) instanceof loadValue(sp + 16));
//},

// copyBytesToJS(dst ref, src []byte) (int, bool)
// Originally copied from upstream Go project, then modified:
// https://github.com/golang/go/blob/3f995c3f3b43033013013e6c7ccc93a9b1411ca9/misc/wasm/wasm_exec.js#L404-L416
"syscall/js.copyBytesToJS": (ret_addr, dest_addr, source_addr, source_len, source_cap) => {
let num_bytes_copied_addr = ret_addr;
let returned_status_addr = ret_addr + 4; // Address of returned boolean status variable

const dst = loadValue(dest_addr);
const src = loadSlice(source_addr, source_len);
if (!(dst instanceof Uint8Array)) {
mem().setUint8(returned_status_addr, 0); // Return "not ok" status
return;
}
const toCopy = src.subarray(0, dst.length);
dst.set(toCopy);
setInt64(num_bytes_copied_addr, toCopy.length);
mem().setUint8(returned_status_addr, 1); // Return "ok" status
},
}
};
}
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