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docs.sheetjs.com/docz/docs/03-demos/42-engines/02-v8.md
SheetJS 8ccb92b3e5 V8 Python Binding Demo
2024-10-20 13:42:13 -04:00

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Blazing Fast Data Processing with V8 C++ + V8 Process structured data in C++ or Rust programs. Seamlessly integrate spreadsheets by pairing V8 and SheetJS. Modernize workflows while maintaining Excel compatibility. demos/bigdata/index solutions/input

import current from '/version.js'; import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem'; import CodeBlock from '@theme/CodeBlock';

V8 is an embeddable JavaScript engine written in C++. It powers Chromium and Chrome, NodeJS and Deno, Adobe UXP and other platforms.

SheetJS is a JavaScript library for reading and writing data from spreadsheets.

This demo uses V8 and SheetJS to read and write spreadsheets. We'll explore how to load SheetJS in a V8 context and process spreadsheets and structured data from C++ and Rust programs.

The "Complete Example" creates a C++ command-line tool for reading spreadsheet files and generating new workbooks. "Bindings" covers V8 engine bindings for other programming languages.

Integration Details

The SheetJS Standalone scripts can be parsed and evaluated in a V8 context.

:::note pass

This section describes a flow where the script is parsed and evaluated each time the program is run.

Using V8 snapshots, SheetJS libraries can be parsed and evaluated at build time. This greatly improves program startup time.

The "Snapshots" section includes a complete example.

:::

Initialize V8

The official V8 hello-world example covers initialization and cleanup. For the purposes of this demo, the key variables are noted below:

v8::Isolate* isolate = v8::Isolate::New(create_params);
v8::Local<v8::Context> context = v8::Context::New(isolate);

The following helper function evaluates C strings as JS code:

v8::Local<v8::Value> eval_code(v8::Isolate *isolate, v8::Local<v8::Context> context, char* code, size_t sz = -1) {
  v8::Local<v8::String> source = v8::String::NewFromUtf8(isolate, code, v8::NewStringType::kNormal, sz).ToLocalChecked();
  v8::Local<v8::Script> script = v8::Script::Compile(context, source).ToLocalChecked();
  return script->Run(context).ToLocalChecked();
}

Load SheetJS Scripts

The main library can be loaded by reading the scripts from the file system and evaluating in the V8 context:

/* simple wrapper to read the entire script file */
static char *read_file(const char *filename, size_t *sz) {
  FILE *f = fopen(filename, "rb");
  if(!f) return NULL;
  long fsize; { fseek(f, 0, SEEK_END); fsize = ftell(f); fseek(f, 0, SEEK_SET); }
  char *buf = (char *)malloc(fsize * sizeof(char));
  *sz = fread((void *) buf, 1, fsize, f);
  fclose(f);
  return buf;
}

// ...
  size_t sz; char *file = read_file("xlsx.full.min.js", &sz);
  v8::Local<v8::Value> result = eval_code(isolate, context, file, sz);

To confirm the library is loaded, XLSX.version can be inspected:

  /* get version string */
  v8::Local<v8::Value> result = eval_code(isolate, context, "XLSX.version");
  v8::String::Utf8Value vers(isolate, result);
  printf("SheetJS library version %s\n", *vers);

Reading Files

V8 supports ArrayBuffer natively. Assuming buf is a C byte array, with length len, the following code stores the data in a global ArrayBuffer:

/* load C char array and save to an ArrayBuffer */
std::unique_ptr<v8::BackingStore> back = v8::ArrayBuffer::NewBackingStore(isolate, len);
memcpy(back->Data(), buf, len);
v8::Local<v8::ArrayBuffer> ab = v8::ArrayBuffer::New(isolate, std::move(back));
v8::Maybe<bool> res = context->Global()->Set(context, v8::String::NewFromUtf8Literal(isolate, "buf"), ab);

Once the raw data is pulled into the engine, the SheetJS read method1 can parse the data. It is recommended to attach the result to a global variable:

/* parse with SheetJS */
v8::Local<v8::Value> result = eval_code(isolate, context, "globalThis.wb = XLSX.read(buf)");

wb, a SheetJS workbook object2, will be a variable in the JS environment that can be inspected using the various SheetJS API functions3.

Writing Files

The SheetJS write method4 generates file bytes from workbook objects. The array type5 instructs the library to generate ArrayBuffer objects:

/* write with SheetJS using type: "array" */
v8::Local<v8::Value> result = eval_code(isolate, context, "XLSX.write(wb, {type:'array', bookType:'xlsb'})");

The underlying memory from an ArrayBuffer can be pulled from the engine:

/* pull result back to C++ */
v8::Local<v8::ArrayBuffer> ab = v8::Local<v8::ArrayBuffer>::Cast(result);
size_t sz = ab->ByteLength();
char *buf = ab->Data();

The resulting buf can be written to file with fwrite.

Complete Example

:::note Tested Deployments

This demo was tested in the following deployments:

V8 Version Platform OS Version Compiler Date
12.4.253 darwin-x64 macOS 14.4 clang 15.0.0 2024-03-15
12.7.130 darwin-arm macOS 14.5 clang 15.0.0 2024-05-25
12.5.48 win10-x64 Windows 10 CL 19.39.33523 2024-03-24
12.5.48 linux-x64 HoloOS 3.5.17 gcc 13.1.1 2024-03-21
12.7.130 linux-arm Debian 12 gcc 12.2.0 2024-05-25

:::

This program parses a file and prints CSV data from the first worksheet. It also generates an XLSB file and writes to the filesystem.

:::caution pass

When the demo was last tested, there were errors in the official V8 embed guide. Corrected instructions are included below.

:::

:::danger pass

The build process is long and will test your patience.

:::

Preparation

  1. Prepare /usr/local/lib:
mkdir -p /usr/local/lib
cd /usr/local/lib

:::note pass

If this step throws a permission error, run the following commands:

sudo mkdir -p /usr/local/lib
sudo chmod 777 /usr/local/lib

:::

  1. Follow the official "Visual Studio" installation steps.

:::info pass

Using the installer tool, the "Desktop development with C++" workload must be installed. In the sidebar, verify the following components are checked:

  • "C++ ATL for latest ... build tools" (v143 when last tested)
  • "C++ MFC for latest ... build tools" (v143 when last tested)

In the "Individual components" tab, search for "Windows 11 SDK" and verify that "Windows 11 SDK (10.0.22621.0)" is checked.

Click "Modify" and allow the installer to finish.

The SDK debugging tools must be installed after the SDK is installed.

  1. Using the Search bar, search "Apps & features".

  2. When the setting panel opens, scroll down to "Windows Software Development Kit - Windows 10.0.22621 and click "Modify".

  3. In the new window, select "Change" and click "Next"

  4. Check "Debugging Tools for Windows" and click "Change"

:::

The following git settings should be changed:

git config --global core.autocrlf false
git config --global core.filemode false
git config --global branch.autosetuprebase always
  1. Download and install depot_tools:
git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

:::note pass

If this step throws a permission error, run the following commands and retry:

sudo mkdir -p /usr/local/lib
sudo chmod 777 /usr/local/lib

:::

The bundle is a ZIP file that should be downloaded and extracted.

The demo was last tested on an exFAT-formatted drive (mounted at E:\).

After extracting, verify that the depot_tools folder is not read-only.

  1. Add the path to the PATH environment variable:
export PATH="/usr/local/lib/depot_tools:$PATH"

At this point, it is strongly recommended to add the line to a shell startup script such as .bashrc or .zshrc

:::caution pass

These instructions are for cmd use. Do not run in PowerShell!

It is strongly recommended to use the "Developer Command Prompt" from Visual Studio as it prepares the console to run build tools.

:::

set DEPOT_TOOLS_WIN_TOOLCHAIN=0
set PATH=E:\depot_tools;%PATH%

In addition, the vs2022_install variable must be set to the Visual Studio folder. For example, using the "Community Edition", the assignment should be

set vs2022_install="C:\Program Files\Microsoft Visual Studio\2022\Community"

These environment variables can be persisted in the Control Panel.

  1. Run gclient once to update depot_tools:
gclient

gclient

:::caution pass

gclient may throw errors related to git and permissions issues:

fatal: detected dubious ownership in repository at 'E:/depot_tools'
'E:/depot_tools' is on a file system that doesnot record ownership
To add an exception for this directory, call:

        git config --global --add safe.directory E:/depot_tools

These issues are related to the exFAT file system. They were resolved by running the recommended commands and re-running gclient.

:::

:::caution pass

There were errors pertaining to gitconfig:

error: could not write config file E:/depot_tools/bootstrap-2@3_8_10_chromium_26_bin/git/etc/gitconfig: File exists

This can happen if the depot_tools folder is read-only. The workaround is to unset the read-only flag for the E:\depot_tools folder.

:::

Clone V8

  1. Create a base directory:
mkdir -p ~/dev/v8
cd ~/dev/v8
fetch v8
cd v8

Note that the actual repo will be placed in ~/dev/v8/v8.

cd E:\
mkdir v8
cd v8
fetch v8
cd v8

:::caution pass

On exFAT, every cloned repo elicited the same git permissions error. fetch will fail with a clear remedy message such as

        git config --global --add safe.directory E:/v8/v8

Run the command then run gclient sync, repeating each time the command fails.

:::

:::caution pass

There were occasional git conflict errors:

v8/tools/clang (ERROR)
----------------------------------------
[0:00:01] Started.
...
error: Your local changes to the following files would be overwritten by checkout:
        plugins/FindBadRawPtrPatterns.cpp
...
Please commit your changes or stash them before you switch branches.
Aborting
error: could not detach HEAD
----------------------------------------
Error: 28> Unrecognized error, please merge or rebase manually.
28> cd E:\v8\v8\tools\clang && git rebase --onto 65ceb79efbc9d1dec9b1a0f4bc0b8d010b9d7a66 refs/remotes/origin/main

The recommended fix is to delete the referenced folder and re-run gclient sync

:::

  1. Checkout the desired version. The following command pulls 12.7.130:
git checkout tags/12.7.130 -b sample

:::caution pass

The official documentation recommends:

git checkout refs/tags/12.7.130 -b sample -t

This command failed in local testing:

E:\v8\v8>git checkout refs/tags/12.7.130 -b sample -t
fatal: cannot set up tracking information; starting point 'refs/tags/12.7.130' is not a branch

:::

Build V8

  1. Build the static library.
tools/dev/v8gen.py x64.release.sample
ninja -C out.gn/x64.release.sample v8_monolith

tools/dev/v8gen.py arm64.release.sample
ninja -C out.gn/arm64.release.sample v8_monolith

tools/dev/v8gen.py x64.release.sample
ninja -C out.gn/x64.release.sample v8_monolith

:::note pass

In some Linux x64 tests using GCC 12, there were build errors that stemmed from warnings. The error messages included the tag -Werror:

../../src/compiler/turboshaft/wasm-gc-type-reducer.cc:212:18: error: 'back_insert_iterator' may not intend to support class template argument deduction [-Werror,-Wctad-maybe-unsupported]
  212 |                  std::back_insert_iterator(snapshots), [this](Block* pred) {
      |                  ^
../../build/linux/debian_bullseye_amd64-sysroot/usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_iterator.h:596:11: note: add a deduction guide to suppress this warning
  596 |     class back_insert_iterator
      |           ^
1 error generated.

This was resolved by manually editing out.gn/x64.release.sample/args.gn. The option treat_warnings_as_errors should be set to false:

treat_warnings_as_errors = false

:::

tools/dev/v8gen.py arm64.release.sample

Append the following lines to out.gn/arm64.release.sample/args.gn:

is_clang = false
treat_warnings_as_errors = false

Run the build:

ninja -C out.gn/arm64.release.sample v8_monolith

:::caution pass

When this demo was last tested, an assertion failed:

../../src/base/small-vector.h: In instantiation of ‘class v8::base::SmallVector<std::pair<const v8::internal::compiler::turboshaft::PhiOp*, const v8::internal::compiler::turboshaft::OpIndex>, 16>’:
../../src/compiler/turboshaft/loop-unrolling-reducer.h:577:11:   required from here
../../src/base/macros.h:215:55: error: static assertion failed: T should be trivially copyable
  215 |   static_assert(::v8::base::is_trivially_copyable<T>::value, \
      |                                                       ^~~~~
../../src/base/small-vector.h:25:3: note: in expansion of macro ‘ASSERT_TRIVIALLY_COPYABLE’
   25 |   ASSERT_TRIVIALLY_COPYABLE(T);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~

The build passed after disabling the assertions:

 class SmallVector {
   // Currently only support trivially copyable and trivially destructible data
   // types, as it uses memcpy to copy elements and never calls destructors.
   // highlight-start
   //ASSERT_TRIVIALLY_COPYABLE(T);
   //static_assert(std::is_trivially_destructible<T>::value);
   // highlight-end

  public:
   static constexpr size_t kInlineSize = kSize;

:::

python3 tools\dev\v8gen.py -vv x64.release.sample
ninja -C out.gn\x64.release.sample v8_monolith

:::caution pass

In local testing, the build sometimes failed with a dbghelp.dll error:

 Exception: dbghelp.dll not found in "C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\dbghelp.dll"

This issue was fixed by removing and reinstalling "Debugging Tools for Windows" from the Control Panel as described in step 0.

:::

:::caution pass

In local testing, the ninja build failed with C++ deprecation errors:

../..\src/wasm/wasm-code-manager.h(670,28): error: 'atomic_load<v8::base::OwnedVector<const unsigned char>>' is deprecated: warning STL4029: std::atomic_*() overloads for shared_ptr are deprecated in C++20. The shared_ptr specialization of std::atomic provides superior functionality. You can define _SILENCE_CXX20_OLD_SHARED_PTR_ATOMIC_SUPPORT_DEPRECATION_WARNING or _SILENCE_ALL_CXX20_DEPRECATION_WARNINGS to suppress this warning. [-Werror,-Wdeprecated-declarations]
  670 |     auto wire_bytes = std::atomic_load(&wire_bytes_);
      |                            ^
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.37.32822\include\memory(3794,1): note: 'atomic_load<v8::base::OwnedVector<const unsigned char>>' has been explicitly marked deprecated here
 3794 | _CXX20_DEPRECATE_OLD_SHARED_PTR_ATOMIC_SUPPORT _NODISCARD shared_ptr<_Ty> atomic_load(
      | ^
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.37.32822\include\yvals_core.h(1317,7): note: expanded from macro '_CXX20_DEPRECATE_OLD_SHARED_PTR_ATOMIC_SUPPORT'
 1317 |     [[deprecated("warning STL4029: "                                                                \
      |       ^
2 errors generated.

The workaround is to append a line to out.gn\x64.release.sample\args.gn:

treat_warnings_as_errors = false

After adding the line, run the ninja command again:

ninja -C out.gn\x64.release.sample v8_monolith

:::

  1. Ensure the sample hello-world compiles and runs:
g++ -I. -Iinclude samples/hello-world.cc -o hello_world -fno-rtti -lv8_monolith \
    -ldl -Lout.gn/x64.release.sample/obj/ -pthread \
    -std=c++17 -DV8_COMPRESS_POINTERS=1 -DV8_ENABLE_SANDBOX
./hello_world

:::info pass

In older V8 versions, the flags -lv8_libbase -lv8_libplatform were required.

Linking against libv8_libbase or libv8_libplatform in V8 version 12.4.253 elicited linker errors:

ld: multiple errors: unknown file type in '/Users/test/dev/v8/v8/out.gn/x64.release.sample/obj/libv8_libplatform.a'; unknown file type in '/Users/test/dev/v8/v8/out.gn/x64.release.sample/obj/libv8_libbase.a'

:::

g++ -I. -Iinclude samples/hello-world.cc -o hello_world -fno-rtti -lv8_monolith \
    -ldl -Lout.gn/arm64.release.sample/obj/ -pthread \
    -std=c++17 -DV8_COMPRESS_POINTERS=1 -DV8_ENABLE_SANDBOX
./hello_world

:::info pass

In older V8 versions, the flags -lv8_libbase -lv8_libplatform were required.

Linking against libv8_libbase or libv8_libplatform in V8 version 12.4.253 elicited linker errors:

ld: multiple errors: unknown file type in '/Users/test/dev/v8/v8/out.gn/x64.release.sample/obj/libv8_libplatform.a'; unknown file type in '/Users/test/dev/v8/v8/out.gn/x64.release.sample/obj/libv8_libbase.a'

:::

g++ -I. -Iinclude samples/hello-world.cc -o hello_world -fno-rtti -lv8_monolith \
    -lv8_libbase -lv8_libplatform -ldl -Lout.gn/x64.release.sample/obj/ -pthread \
    -std=c++17 -DV8_COMPRESS_POINTERS=1 -DV8_ENABLE_SANDBOX
./hello_world

g++ -I. -Iinclude samples/hello-world.cc -o hello_world -fno-rtti -lv8_monolith \
    -lv8_libbase -lv8_libplatform -ldl -Lout.gn/arm64.release.sample/obj/ -pthread \
    -std=c++17 -DV8_COMPRESS_POINTERS=1 -DV8_ENABLE_SANDBOX
./hello_world

cl /I. /Iinclude samples/hello-world.cc /GR- v8_monolith.lib Advapi32.lib Winmm.lib Dbghelp.lib /std:c++17 /DV8_COMPRESS_POINTERS=1 /DV8_ENABLE_SANDBOX /link /out:hello_world.exe /LIBPATH:out.gn\x64.release.sample\obj\
.\hello_world.exe

Prepare Project

  1. Make a new project folder:
cd ~/dev
mkdir -p sheetjs-v8
cd sheetjs-v8

cd E:\
mkdir sheetjs-v8
cd sheetjs-v8
  1. Copy the sample source:
cp ~/dev/v8/v8/samples/hello-world.cc .
  1. Create symbolic links to the include headers and obj library folders:
ln -s ~/dev/v8/v8/include
ln -s ~/dev/v8/v8/out.gn/x64.release.sample/obj

ln -s ~/dev/v8/v8/include
ln -s ~/dev/v8/v8/out.gn/arm64.release.sample/obj

ln -s ~/dev/v8/v8/include
ln -s ~/dev/v8/v8/out.gn/x64.release.sample/obj

ln -s ~/dev/v8/v8/include
ln -s ~/dev/v8/v8/out.gn/arm64.release.sample/obj

copy E:\v8\v8\samples\hello-world.cc .\
  1. Observe that exFAT does not support symbolic links and move on to step 11.
  1. Build and run the hello-world example from this folder:
g++ -I. -Iinclude hello-world.cc -o hello_world -fno-rtti -lv8_monolith \
    -lv8_libbase -lv8_libplatform -ldl -Lobj/ -pthread -std=c++17 \
    -DV8_COMPRESS_POINTERS=1 -DV8_ENABLE_SANDBOX
./hello_world

:::caution pass

In some V8 versions, the command failed in the linker stage:

ld: multiple errors: unknown file type in '/Users/test/dev/v8/v8/out.gn/x64.release.sample/obj/libv8_libplatform.a'; unknown file type in '/Users/test/dev/v8/v8/out.gn/x64.release.sample/obj/libv8_libbase.a'

The build succeeds after removing libv8_libbase and libv8_libplatform:

g++ -I. -Iinclude hello-world.cc -o hello_world -fno-rtti -lv8_monolith \
    -ldl -Lobj/ -pthread -std=c++17 \
    -DV8_COMPRESS_POINTERS=1 -DV8_ENABLE_SANDBOX
./hello_world

:::

cl /MT /I..\v8\v8\ /I..\v8\v8\include hello-world.cc /GR- v8_monolith.lib Advapi32.lib Winmm.lib Dbghelp.lib /std:c++17 /DV8_COMPRESS_POINTERS=1 /DV8_ENABLE_SANDBOX /link /out:hello_world.exe /LIBPATH:..\v8\v8\out.gn\x64.release.sample\obj\
.\hello_world.exe

Add SheetJS

  1. Download the SheetJS Standalone script and test file. Save both files in the project directory:

{\ curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js curl -LO https://docs.sheetjs.com/pres.numbers}

  1. Download sheetjs.v8.cc:
curl -LO https://docs.sheetjs.com/v8/sheetjs.v8.cc
  1. Compile standalone sheetjs.v8 binary
g++ -I. -Iinclude sheetjs.v8.cc -o sheetjs.v8 -fno-rtti -lv8_monolith \
    -lv8_libbase -lv8_libplatform -ldl -Lobj/ -pthread -std=c++17 \
    -DV8_COMPRESS_POINTERS=1 -DV8_ENABLE_SANDBOX

:::caution pass

In some V8 versions, the command failed in the linker stage:

ld: multiple errors: unknown file type in '/Users/test/dev/v8/v8/out.gn/x64.release.sample/obj/libv8_libplatform.a'; unknown file type in '/Users/test/dev/v8/v8/out.gn/x64.release.sample/obj/libv8_libbase.a'

The build succeeds after removing libv8_libbase and libv8_libplatform:

g++ -I. -Iinclude sheetjs.v8.cc -o sheetjs.v8 -fno-rtti -lv8_monolith \
    -ldl -Lobj/ -pthread -std=c++17 \
    -DV8_COMPRESS_POINTERS=1 -DV8_ENABLE_SANDBOX

:::

cl /MT /I..\v8\v8\ /I..\v8\v8\include sheetjs.v8.cc /GR- v8_monolith.lib Advapi32.lib Winmm.lib Dbghelp.lib /std:c++17 /DV8_COMPRESS_POINTERS=1 /DV8_ENABLE_SANDBOX /link /out:sheetjs.v8.exe /LIBPATH:..\v8\v8\out.gn\x64.release.sample\obj\
  1. Run the demo:
./sheetjs.v8 pres.numbers

.\sheetjs.v8.exe pres.numbers

If the program succeeded, the CSV contents will be printed to console and the file sheetjsw.xlsb will be created. That file can be opened with Excel.

Bindings

Bindings exist for many languages. As these bindings require "native" code, they may not work on every platform.

Rust

The v8 crate6 provides binary builds and straightforward bindings. The Rust code is similar to the C++ code.

Pulling data from an ArrayBuffer back into Rust involves an unsafe operation:

/* assuming JS code returns an ArrayBuffer, copy result to a Vec<u8> */
fn eval_code_ab(scope: &mut v8::HandleScope, code: &str) -> Vec<u8> {
  let source = v8::String::new(scope, code).unwrap();
  let script = v8::Script::compile(scope, source, None).unwrap();
  let result: v8::Local<v8::ArrayBuffer> = script.run(scope).unwrap().try_into().unwrap();
  /* In C++, `Data` returns a pointer. Collecting data into Vec<u8> is unsafe */
  unsafe { return std::slice::from_raw_parts_mut(
    result.data().unwrap().cast::<u8>().as_ptr(),
    result.byte_length()
  ).to_vec(); }
}

:::note Tested Deployments

This demo was last tested in the following deployments:

Architecture V8 Crate Date
darwin-x64 0.92.0 2024-05-28
darwin-arm 0.92.0 2024-05-25
win10-x64 0.89.0 2024-03-24
linux-x64 0.91.0 2024-04-25
linux-arm 0.92.0 2024-05-25

:::

  1. Create a new project:
cargo new sheetjs-rustyv8
cd sheetjs-rustyv8
cargo run
  1. Add the v8 crate:
cargo add v8
cargo run
  1. Download the SheetJS Standalone script and test file. Save both files in the project directory:

{\ curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js curl -LO https://docs.sheetjs.com/pres.numbers}

  1. Download main.rs and replace src/main.rs:
curl -L -o src/main.rs https://docs.sheetjs.com/v8/main.rs
  1. Build and run the app:
cargo run pres.numbers

If the program succeeded, the CSV contents will be printed to console and the file sheetjsw.xlsb will be created. That file can be opened with Excel.

Java

Javet is a Java binding to the V8 engine. Javet simplifies conversions between Java data structures and V8 equivalents.

Java byte arrays (byte[]) are projected in V8 as Int8Array. The SheetJS read method expects a Uint8Array. The following script snippet performs a zero-copy conversion:

// assuming `i8` is an Int8Array
const u8 = new Uint8Array(i8.buffer, i8.byteOffset, i8.length);

:::note Tested Deployments

This demo was last tested in the following deployments:

Architecture V8 Version Javet Java Date
darwin-x64 12.6.228.13 3.1.3 22 2024-06-19
darwin-arm 12.6.228.13 3.1.3 11.0.23 2024-06-19
win10-x64 12.6.228.13 3.1.3 11.0.16 2024-06-21
linux-x64 12.6.228.13 3.1.3 17.0.7 2024-06-20
linux-arm 12.6.228.13 3.1.3 17.0.11 2024-06-20

:::

  1. Create a new project:
mkdir sheetjs-javet
cd sheetjs-javet
  1. Download the Javet JAR. There are different archives for different platforms.
curl -LO https://repo1.maven.org/maven2/com/caoccao/javet/javet-macos/3.1.3/javet-macos-3.1.3.jar

curl -LO https://repo1.maven.org/maven2/com/caoccao/javet/javet-macos/3.1.3/javet-macos-3.1.3.jar

curl -LO https://repo1.maven.org/maven2/com/caoccao/javet/javet/3.1.3/javet-3.1.3.jar

curl -LO https://repo1.maven.org/maven2/com/caoccao/javet/javet-linux-arm64/3.1.3/javet-linux-arm64-3.1.3.jar

curl -LO https://repo1.maven.org/maven2/com/caoccao/javet/javet/3.1.3/javet-3.1.3.jar
  1. Download the SheetJS Standalone script and test file. Save both files in the project directory:

{\ curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js curl -LO https://docs.sheetjs.com/pres.xlsx}

  1. Download SheetJSJavet.java:
curl -LO https://docs.sheetjs.com/v8/SheetJSJavet.java
  1. Build and run the Java application:
javac -cp ".:javet-macos-3.1.3.jar" SheetJSJavet.java
java -cp ".:javet-macos-3.1.3.jar" SheetJSJavet pres.xlsx

javac -cp ".:javet-macos-3.1.3.jar" SheetJSJavet.java
java -cp ".:javet-macos-3.1.3.jar" SheetJSJavet pres.xlsx

javac -cp ".:javet-3.1.3.jar" SheetJSJavet.java
java -cp ".:javet-3.1.3.jar" SheetJSJavet pres.xlsx

javac -cp ".:javet-linux-arm64-3.1.3.jar" SheetJSJavet.java
java -cp ".:javet-linux-arm64-3.1.3.jar" SheetJSJavet pres.xlsx

javac -cp ".;javet-3.1.3.jar" SheetJSJavet.java
java -cp ".;javet-3.1.3.jar" SheetJSJavet pres.xlsx

If the program succeeded, the CSV contents will be printed to console.

C#

ClearScript is a .NET interface to the V8 engine.

C# byte arrays (byte[]) must be explicitly converted to arrays of bytes:

/* read data into a byte array */
byte[] filedata = File.ReadAllBytes("pres.numbers");

// highlight-start
/* generate a JS Array (variable name `buf`) from the data */
engine.Script.buf = engine.Script.Array.from(filedata);
// highlight-end

/* parse data */
engine.Evaluate("var wb = XLSX.read(buf, {type: 'array'});");

:::note Tested Deployments

This demo was last tested in the following deployments:

Architecture V8 Version Date
darwin-x64 12.3.219.12 2024-07-16
darwin-arm 12.3.219.12 2024-07-16
win10-x64 12.3.219.12 2024-07-16
win11-arm 12.3.219.12 2024-07-16
linux-x64 12.3.219.12 2024-07-16
linux-arm 12.3.219.12 2024-07-16

:::

  1. Set the DOTNET_CLI_TELEMETRY_OPTOUT environment variable to 1.
How to disable telemetry (click to hide)

Add the following line to .profile, .bashrc and .zshrc:

export DOTNET_CLI_TELEMETRY_OPTOUT=1

Close and restart the Terminal to load the changes.

Type env in the search bar and select "Edit the system environment variables".

In the new window, click the "Environment Variables..." button.

In the new window, look for the "System variables" section and click "New..."

Set the "Variable name" to DOTNET_CLI_TELEMETRY_OPTOUT and the value to 1.

Click "OK" in each window (3 windows) and restart your computer.

  1. Install .NET
Installation Notes (click to show)

For macOS x64 and ARM64, install the dotnet-sdk Cask with Homebrew:

brew install --cask dotnet-sdk

For Steam Deck Holo and other Arch Linux x64 distributions, the dotnet-sdk and dotnet-runtime packages should be installed using pacman:

sudo pacman -Syu dotnet-sdk dotnet-runtime

https://dotnet.microsoft.com/en-us/download/dotnet/6.0 is the official source for Windows and ARM64 Linux versions.

  1. Open a new Terminal window in macOS or PowerShell window in Windows.

  2. Create a new project:

mkdir SheetJSClearScript
cd SheetJSClearScript
dotnet new console
dotnet run
  1. Add ClearScript to the project:
dotnet add package Microsoft.ClearScript.Complete --version 7.4.5
  1. Download the SheetJS standalone script and test file. Move both files to the project directory:

{\ curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js curl -LO https://docs.sheetjs.com/pres.xlsx}

  1. Replace Program.cs with the following:
using Microsoft.ClearScript.JavaScript;
using Microsoft.ClearScript.V8;

/* initialize ClearScript */
var engine = new V8ScriptEngine();

/* Load SheetJS Scripts */
engine.Evaluate(File.ReadAllText("xlsx.full.min.js"));
Console.WriteLine("SheetJS version {0}", engine.Evaluate("XLSX.version"));

/* Read and Parse File */
byte[] filedata = File.ReadAllBytes(args[0]);
engine.Script.buf = engine.Script.Array.from(filedata);
engine.Evaluate("var wb = XLSX.read(buf, {type: 'array'});");

/* Print CSV of first worksheet */
engine.Evaluate("var ws = wb.Sheets[wb.SheetNames[0]];");
var csv = engine.Evaluate("XLSX.utils.sheet_to_csv(ws)");
Console.Write(csv);

/* Generate XLSB file and save to SheetJSJint.xlsb */
var xlsb = (ITypedArray<byte>)engine.Evaluate("XLSX.write(wb, {bookType: 'xlsb', type: 'buffer'})");
File.WriteAllBytes("SheetJSClearScript.xlsb", xlsb.ToArray());

After saving, run the program and pass the test file name as an argument:

dotnet run pres.xlsx

If successful, the program will print the contents of the first sheet as CSV rows. It will also create SheetJSClearScript.xlsb, a workbook that can be opened in a spreadsheet editor.

Python

pyv8 is a Python wrapper for V8.

The stpyv8 package7 is an actively-maintained fork with binary wheels.

:::caution pass

When this demo was last tested, there was no direct conversion between Python bytes and JavaScript ArrayBuffer data.

This is a known issue8. The current recommendation is Base64 strings.

:::

Python Base64 Strings

The SheetJS read1 and write4 methods support Base64 strings through the base64 type5.

Reading Files

It is recommended to create a global context with a special method that handles file reading from Python. The read_file helper in the following snippet will read bytes from sheetjs.xlsx and generate a Base64 string:

from base64 import b64encode;
from STPyV8 import JSContext, JSClass;

# Create context with methods for file i/o
class Base64Context(JSClass):
  def read_file(self, path):
    with open(path, "rb") as f:
      data = f.read();
    return b64encode(data).decode("ascii");
globals = Base64Context();

# The JSContext starts and cleans up the V8 engine
with JSContext(globals) as ctxt:
  print(ctxt.eval("read_file('sheetjs.xlsx')")); # read base64 data and print

Writing Files

Since the SheetJS write method returns a Base64 string, the result can be decoded and written to file from Python:

from base64 import b64decode;
from STPyV8 import JSContext;

# The JSContext starts and cleans up the V8 engine
with JSContext() as ctxt:
  # ... initialization and workbook creation ...
  xlsb = ctxt.eval("XLSX.write(wb, {type: 'base64', bookType: 'xlsb'})");
  with open("SheetJSSTPyV8.xlsb", "wb") as f:
    f.write(b64decode(xlsb));

Python Demo

:::note Tested Deployments

This demo was last tested in the following deployments:

Architecture V8 Version Python Date
darwin-arm 13.0.245.16 3.13.0 2024-10-20

:::

  1. Make a new folder for the project:
mkdir sheetjs-stpyv8
cd sheetjs-stpyv8
  1. Install stpyv8:
pip install stpyv8

:::caution pass

The install may fail with a externally-managed-environment error:

error: externally-managed-environment

× This environment is externally managed

The wheel can be downloaded and forcefully installed. The following commands download and install version 13.0.245.16 for Python 3.13 on darwin-arm:

curl -LO https://github.com/cloudflare/stpyv8/releases/download/v13.0.245.16/stpyv8-13.0.245.16-cp313-cp313-macosx_14_0_arm64.whl
sudo python -m pip install --upgrade stpyv8-13.0.245.16-cp313-cp313-macosx_14_0_arm64.whl --break-system-packages

:::

  1. Download the SheetJS standalone script and test file. Move both files to the project directory:

{\ curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js curl -LO https://docs.sheetjs.com/pres.xlsx}

  1. Download sheetjs-stpyv8.py:
curl -LO https://docs.sheetjs.com/v8/sheetjs-stpyv8.py
  1. Run the script and pass pres.xlsx as the first argument:
python sheetjs-stpyv8.py pres.xlsx

The script will display CSV rows from the first worksheet. It will also create SheetJSSTPyV8.xlsb, a workbook that can be opened with a spreadsheet editor.

Snapshots

At a high level, V8 snapshots are raw dumps of the V8 engine state. It is much more efficient for programs to load snapshots than to evaluate code.

Snapshot Demo

There are two parts to this demo:

A) The snapshot command creates a snapshot with the SheetJS standalone script and supplementary NUMBERS script. It will dump the snapshot to snapshot.bin

B) The sheet2csv tool embeds snapshot.bin. The tool will parse a specified file, print CSV contents of a named worksheet, and export the workbook to NUMBERS.

:::note Tested Deployments

This demo was last tested in the following deployments:

Architecture V8 Version Crate Date
darwin-x64 12.6.228.3 0.92.0 2024-05-28
darwin-arm 12.6.228.3 0.92.0 2024-05-23
win10-x64 12.3.219.9 0.88.0 2024-03-24
win11-x64 12.6.228.3 0.92.0 2024-05-23
linux-x64 12.3.219.9 0.88.0 2024-03-18
linux-arm 12.6.228.3 0.92.0 2024-05-26

:::

  1. Make a new folder for the project:
mkdir sheetjs2csv
cd sheetjs2csv
  1. Download the following scripts:
curl -o Cargo.toml https://docs.sheetjs.com/cli/Cargo.toml
curl -o snapshot.rs https://docs.sheetjs.com/cli/snapshot.rs
curl -o sheet2csv.rs https://docs.sheetjs.com/cli/sheet2csv.rs
  1. Download the SheetJS Standalone script and NUMBERS supplementary script. Move both scripts to the project directory:
  • xlsx.full.min.js
  • xlsx.zahl.js

{\ curl -o xlsx.full.min.js https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js curl -o xlsx.zahl.js https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.zahl.js}

  1. Build the V8 snapshot:
cargo build --bin snapshot
cargo run --bin snapshot

:::caution pass

In some tests, the Linux AArch64 build failed with an error:

error[E0080]: evaluation of constant value failed

     |
1715 |   assert!(size_of::<TypeId>() == size_of::<u64>());
     |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'assertion failed: size_of::<TypeId>() == size_of::<u64>()'

Versions 0.75.1, 0.82.0, and 0.92.0 are known to work.

:::

  1. Build sheet2csv (sheet2csv.exe in Windows):
cargo build --release --bin sheet2csv
  1. Download the test file https://docs.sheetjs.com/pres.numbers:
curl -o pres.numbers https://docs.sheetjs.com/pres.numbers
  1. Test the application:
mv target/release/sheet2csv .
./sheet2csv pres.numbers

mv target/release/sheet2csv.exe .
.\sheet2csv.exe pres.numbers

  1. See read in "Reading Files" ↩︎

  2. See "SheetJS Data Model" for more details on the object representation. ↩︎

  3. See "API Reference" for a list of functions that ship with the library. "Spreadsheet Features" covers workbook and worksheet features that can be modified directly. ↩︎

  4. See write in "Writing Files" ↩︎

  5. See "Supported Output Formats" type in "Writing Files" ↩︎

  6. The project does not have an official website. The official Rust crate is hosted on crates.io. ↩︎

  7. The project does not have a separate website. The source repository is hosted on GitHub ↩︎

  8. According to a maintainer, typed arrays were not supported in the original pyv8 project ↩︎