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experimental zstd support for images and partfiles (via webworker)
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copy committed Aug 6, 2023
1 parent de1f83c commit 8aa33c7
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Showing 2 changed files with 136 additions and 25 deletions.
118 changes: 115 additions & 3 deletions src/browser/starter.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -188,13 +188,15 @@ function V86Starter(options)
try
{
const { instance } = await WebAssembly.instantiate(bytes, env);
this.wasm_source = bytes;
resolve(instance.exports);
}
catch(err)
{
v86util.load_file(v86_bin_fallback, {
done: async bytes => {
const { instance } = await WebAssembly.instantiate(bytes, env);
this.wasm_source = bytes;
resolve(instance.exports);
},
});
Expand Down Expand Up @@ -227,6 +229,9 @@ function V86Starter(options)

this.continue_init(emulator, options);
});

this.zstd_worker = null;
this.zstd_worker_request_id = 0;
}

V86Starter.prototype.continue_init = async function(emulator, options)
Expand Down Expand Up @@ -365,7 +370,7 @@ V86Starter.prototype.continue_init = async function(emulator, options)

var files_to_load = [];

function add_file(name, file)
const add_file = (name, file) =>
{
if(!file)
{
Expand Down Expand Up @@ -437,7 +442,7 @@ V86Starter.prototype.continue_init = async function(emulator, options)

if(file.use_parts)
{
buffer = new v86util.AsyncXHRPartfileBuffer(file.url, file.size, file.fixed_chunk_size);
buffer = new v86util.AsyncXHRPartfileBuffer(file.url, file.size, file.fixed_chunk_size, false, this.zstd_decompress_worker.bind(this));
}
else
{
Expand All @@ -462,7 +467,7 @@ V86Starter.prototype.continue_init = async function(emulator, options)
{
dbg_log("Ignored file: url=" + file.url + " buffer=" + file.buffer);
}
}
};

if(options["state"])
{
Expand Down Expand Up @@ -543,6 +548,12 @@ V86Starter.prototype.continue_init = async function(emulator, options)
v86util.load_file(f.url, {
done: function(result)
{
if(f.url.endsWith(".zst") && f.name !== "initial_state")
{
dbg_assert(f.size, "A size must be provided for compressed images");
result = this.zstd_decompress(f.size, new Uint8Array(result));
}

put_on_settings.call(this, f.name, f.as_json ? result : new v86util.SyncBuffer(result));
cont(index + 1);
}.bind(this),
Expand Down Expand Up @@ -648,6 +659,107 @@ V86Starter.prototype.continue_init = async function(emulator, options)
}
};

/**
* @param {number} decompressed_size
* @param {Uint8Array} src
* @return {ArrayBuffer}
*/
V86Starter.prototype.zstd_decompress = function(decompressed_size, src)
{
const cpu = this.v86.cpu;

dbg_assert(!this.zstd_context);
this.zstd_context = cpu.zstd_create_ctx(src.length);

new Uint8Array(cpu.wasm_memory.buffer).set(src, cpu.zstd_get_src_ptr(this.zstd_context));

const ptr = cpu.zstd_read(this.zstd_context, decompressed_size);
const result = cpu.wasm_memory.buffer.slice(ptr, ptr + decompressed_size);
cpu.zstd_read_free(ptr, decompressed_size);

cpu.zstd_free_ctx(this.zstd_context);
this.zstd_context = null;

return result;
};

/**
* @param {number} decompressed_size
* @param {Uint8Array} src
* @return {Promise<ArrayBuffer>}
*/
V86Starter.prototype.zstd_decompress_worker = async function(decompressed_size, src)
{
if(!this.zstd_worker)
{
function the_worker()
{
let wasm;

globalThis.onmessage = function(e)
{
if(!wasm)
{
const env = Object.fromEntries([
"cpu_exception_hook", "hlt_op",
"microtick", "get_rand_int", "pic_acknowledge",
"io_port_read8", "io_port_read16", "io_port_read32",
"io_port_write8", "io_port_write16", "io_port_write32",
"mmap_read8", "mmap_read16", "mmap_read32",
"mmap_write8", "mmap_write16", "mmap_write32", "mmap_write64", "mmap_write128",
"codegen_finalize",
"jit_clear_func", "jit_clear_all_funcs",
].map(f => [f, () => console.error("zstd worker unexpectedly called " + f)]));

env["__indirect_function_table"] = new WebAssembly.Table({ element: "anyfunc", "initial": 1024 });
env["abort"] = () => { throw new Error("zstd worker aborted"); };
env["log_from_wasm"] = env["console_log_from_wasm"] = (off, len) => {
console.log(String.fromCharCode(...new Uint8Array(wasm.exports.memory.buffer, off, len)));
};
env["dbg_trace_from_wasm"] = () => console.trace();

wasm = new WebAssembly.Instance(new WebAssembly.Module(e.data), { "env": env });
return;
}

const { src, decompressed_size, id } = e.data;
const exports = wasm.exports;

const zstd_context = exports["zstd_create_ctx"](src.length);
new Uint8Array(exports.memory.buffer).set(src, exports["zstd_get_src_ptr"](zstd_context));

const ptr = exports["zstd_read"](zstd_context, decompressed_size);
const result = exports.memory.buffer.slice(ptr, ptr + decompressed_size);
exports["zstd_read_free"](ptr, decompressed_size);

exports["zstd_free_ctx"](zstd_context);

postMessage({ result, id }, [result]);
};
}

const url = URL.createObjectURL(new Blob(["(" + the_worker.toString() + ")()"], { type: "text/javascript" }));
this.zstd_worker = new Worker(url);
URL.revokeObjectURL(url);
this.zstd_worker.postMessage(this.wasm_source, [this.wasm_source]);
}

return new Promise(resolve => {
const id = this.zstd_worker_request_id++;
const done = async e =>
{
if(e.data.id === id)
{
this.zstd_worker.removeEventListener("message", done);
dbg_assert(decompressed_size === e.data.result.byteLength);
resolve(e.data.result);
}
};
this.zstd_worker.addEventListener("message", done);
this.zstd_worker.postMessage({ src, decompressed_size, id }, [src.buffer]);
});
};

V86Starter.prototype.get_bzimage_initrd_from_filesystem = function(filesystem)
{
const root = (filesystem.read_dir("/") || []).map(x => "/" + x);
Expand Down
43 changes: 21 additions & 22 deletions src/buffer.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -381,20 +381,14 @@
* @param {number|undefined} fixed_chunk_size
* @param {boolean|undefined} partfile_alt_format
*/
function AsyncXHRPartfileBuffer(filename, size, fixed_chunk_size, partfile_alt_format)
function AsyncXHRPartfileBuffer(filename, size, fixed_chunk_size, partfile_alt_format, zstd_decompress)
{
const parts = filename.match(/(.*)(\..*)/);
const parts = filename.match(/\.[^\.]+(\.zst)?$/);

if(parts)
{
this.basename = parts[1];
this.extension = parts[2];
}
else
{
this.basename = filename;
this.extension = "";
}
this.extension = parts ? parts[0] : "";
this.basename = filename.substring(0, filename.length - this.extension.length);

this.is_zstd = this.extension.endsWith(".zst");

if(!this.basename.endsWith("/"))
{
Expand All @@ -407,6 +401,7 @@
this.byteLength = size;
this.fixed_chunk_size = fixed_chunk_size;
this.partfile_alt_format = !!partfile_alt_format;
this.zstd_decompress = zstd_decompress;

this.cache_reads = !!fixed_chunk_size; // TODO: could also be useful in other cases (needs testing)

Expand Down Expand Up @@ -478,29 +473,33 @@

if(block)
{
const cur = i * this.fixed_chunk_size;
blocks.set(block, cur);
blocks.set(block, i * this.fixed_chunk_size);
finished++;
if(finished === total_count)
{
const tmp_blocks = blocks.subarray(m_offset, m_offset + len);
fn(tmp_blocks);
fn(blocks.subarray(m_offset, m_offset + len));
}
}
else
{
v86util.load_file(part_filename, {
done: function done(buffer)
done: async function done(buffer)
{
const cur = i * this.fixed_chunk_size;
const block = new Uint8Array(buffer);
let block = new Uint8Array(buffer);

if(this.is_zstd)
{
const decompressed = await this.zstd_decompress(this.fixed_chunk_size, block);
block = new Uint8Array(decompressed);
}

blocks.set(block, i * this.fixed_chunk_size);
this.handle_read((start_index + i) * this.fixed_chunk_size, this.fixed_chunk_size|0, block);
blocks.set(block, cur);

finished++;
if(finished === total_count)
{
const tmp_blocks = blocks.subarray(m_offset, m_offset + len);
fn(tmp_blocks);
fn(blocks.subarray(m_offset, m_offset + len));
}
}.bind(this),
});
Expand Down

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