---
title: C++ + ChakraCore
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---
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ChakraCore is an embeddable JS engine written in C++.
The [Standalone scripts](/docs/getting-started/installation/standalone) can be
parsed and evaluated in a ChakraCore context.
## Integration Details
_Initialize ChakraCore_
ChakraCore provides a `global` object through `JsGetGlobalObject`:
```cpp
/* initialize */
JsRuntimeHandle runtime;
JsContextRef context;
size_t cookie = 0;
JsCreateRuntime(JsRuntimeAttributeNone, nullptr, &runtime);
JsCreateContext(runtime, &context);
JsSetCurrentContext(context);
/* obtain reference to global object */
JsValueRef global;
JsGetGlobalObject(&global);
/* DO WORK HERE */
/* cleanup */
JsSetCurrentContext(JS_INVALID_REFERENCE);
JsDisposeRuntime(runtime);
```
:::note
Cleanup and validation code is omitted from the discussion. The integration
example shows structured validation and controlled memory usage.
:::
_Load SheetJS Scripts_
The main library can be loaded by reading the script from the file system and
evaluating in the ChakraCore context:
```cpp
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;
}
#define EVAL_FILE(path) {\
JsValueRef filename; \
JsValueRef result; \
JsCreateString(path, strlen(path), &filename); \
size_t len; const char* script = read_file(path, &len);\
JsValueRef src;\
JsCreateExternalArrayBuffer((void*)script, len, nullptr, nullptr, &src);\
JsRun(src, cookie++, filename, JsParseScriptAttributeNone, &result); \
}
// ...
/* load library */
EVAL_FILE("shim.min.js")
EVAL_FILE("xlsx.full.min.js")
```
### Reading Files
`JsCreateExternalArrayBuffer` can generate an `ArrayBuffer` from a C byte array:
```cpp
/* read file */
size_t len; char *buf = read_file(argv[1], &len);
/* load data into array buffer */
JsValueRef ab;
JsCreateExternalArrayBuffer((void*)buf, len, nullptr, nullptr, &ab);
```
After pushing the data, it is easiest to store properties on `globalThis`:
```cpp
/* assign to the `buf` global variable */
JsValueRef buf_str; JsCreateString("buf", strlen("buf"), &buf_str);
JsObjectSetProperty(global, buf_str, ab, true);
/* call globalThis.wb = XLSX.read(ab) */
const char* script_str ="globalThis.wb = XLSX.read(buf);"
JsValueRef script;
JsCreateExternalArrayBuffer((void*)script_str, (size_t)strlen(script_str), nullptr, nullptr, &script);
JsRun(script, cookie++, fname, JsParseScriptAttributeNone, &result);
```
## Complete Example
The "Integration Example" covers a traditional integration in a C application,
while the "CLI Test" demonstrates other concepts using the `ch` CLI tool.
### Integration Example
:::note
This demo was last tested on 2023 April 09 against ChakraCore commit `c3ead3f`
on a Intel Mac. `gcc -v` printed:
```
Apple clang version 14.0.0 (clang-1400.0.29.202)
Target: x86_64-apple-darwin21.6.0
```
:::
0) Build ChakraCore:
```bash
git clone https://github.com/Microsoft/ChakraCore
cd ChakraCore
git checkout c3ead3f
./build.sh --static --icu=/usr/local/opt/icu4c/include --test-build -j=8
cd ..
```
1) Download the source file and `Makefile`:
- [`sheetjs.ch.cpp`](pathname:///chakra/sheetjs.ch.cpp)
- [`Makefile`](pathname:///chakra/Makefile)
```bash
curl -LO https://docs.sheetjs.com/chakra/sheetjs.ch.c
curl -LO https://docs.sheetjs.com/chakra/Makefile
```
2) Build the sample application:
```bash
make
```
This program tries to parse the file specified by the first argument
4) Download the standalone script, shim script, and test file:
{`\
curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js
curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/shim.min.js
curl -LO https://sheetjs.com/pres.numbers`}
5) Run the test program:
```
./sheetjs.ch pres.numbers
```
If successful, the program will print the contents of the first sheet as CSV.
### CLI Test
:::note
This demo was last tested on 2023 April 09 against `ch` `1.13.0.0-beta`.
The command line tool was built against commit `c3ead3f`.
:::
Due to limitations of the `ch` standalone binary, this demo will encode a test
file as a Base64 string and directly add it to an amalgamated script.
0) Download and extract the ChakraCore release ZIP. Copy the binary (`bin/ch`)
to your project folder.
1) Download the standalone script, shim, and test file:
2) Bundle the test file and create `payload.js`:
```bash
node -e "fs.writeFileSync('payload.js', 'var payload = \"' + fs.readFileSync('pres.numbers').toString('base64') + '\";')"
```
3) Create support scripts:
- `global.js` creates a `global` variable:
```js title="global.js"
var global = (function(){ return this; }).call(null);
```
- `chakra.js` will call `XLSX.read` and `XLSX.utils.sheet_to_csv`:
```js title="chakra.js"
var wb = XLSX.read(payload, {type:'base64'});
console.log(XLSX.utils.sheet_to_csv(wb.Sheets[wb.SheetNames[0]]));
```
4) Create the amalgamation `xlsx.chakra.js`:
```bash
cat global.js xlsx.full.min.js payload.js chakra.js > xlsx.chakra.js
```
The final script defines `global` before loading the standalone library. Once
ready, it will read the bundled test data and print the contents as CSV.
5) Run the script using the ChakraCore standalone binary:
```
./ch xlsx.chakra.js
```