Deno Core

https://docs.rs/deno_core
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Deno_core is a Rust library that provides the core runtime for Deno, enabling JavaScript execution...
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### Example extension usage

Source: https://docs.rs/deno_core/latest/deno_core/macro.extension.html

A basic example showing how to define an extension with an op and an ESM file.

```rust
#[op]
fn op_xyz() {
}

deno_core::extension!(
  my_extension,
  ops = [ op_xyz ],
  esm = [ "my_script.js" ],
  docs = "A small sample extension"
);
```

--------------------------------

### FastString Construction Example

Source: https://docs.rs/deno_core/latest/src/deno_core/fast_string.rs.html

Example showing how to construct a FastString.

```rust
168/// ```rust
169/// # use deno_core::{ascii_str, FastString};
170///
```

--------------------------------

### Trim start matches example

Source: https://docs.rs/deno_core/latest/deno_core/stats/struct.RuntimeActivityTrace.html

Demonstrates trimming characters from the start of a string using a slice of characters.

```rust
let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");
```

--------------------------------

### Box::from_raw Examples

Source: https://docs.rs/deno_core/latest/deno_core/type.CustomModuleEvaluationCb.html

Examples demonstrating how to reconstruct a Box from a raw pointer.

```rust
let x = Box::new(5);
let ptr = Box::into_raw(x);
let x = unsafe { Box::from_raw(ptr) };
```

```rust
use std::alloc::{alloc, Layout};

unsafe {
    let ptr = alloc(Layout::new::<i32>()) as *mut i32;
    // In general .write is required to avoid attempting to destruct
    // the (uninitialized) previous contents of `ptr`, though for this
    // simple example `*ptr = 5` would have worked as well.
    ptr.write(5);
    let x = Box::from_raw(ptr);
}
```

--------------------------------

### Box::from_non_null Examples

Source: https://docs.rs/deno_core/latest/deno_core/type.CustomModuleEvaluationCb.html

Examples demonstrating how to reconstruct a Box from a NonNull pointer using experimental nightly APIs.

```rust
#![feature(box_vec_non_null)]

let x = Box::new(5);
let non_null = Box::into_non_null(x);
let x = unsafe { Box::from_non_null(non_null) };
```

```rust
#![feature(box_vec_non_null)]

use std::alloc::{alloc, Layout};
use std::ptr::NonNull;

unsafe {
    let non_null = NonNull::new(alloc(Layout::new::<i32>()).cast::<i32>())
        .expect("allocation failed");
    // In general .write is required to avoid attempting to destruct
    // the (uninitialized) previous contents of `non_null`.
    non_null.write(5);
    let x = Box::from_non_null(non_null);
}
```

--------------------------------

### Async Operation Examples

Source: https://docs.rs/deno_core/latest/src/deno_core/runtime/ops.rs.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Examples of defining and testing asynchronous operations in Deno Core.

```rust
#[op2]
async fn op_async_void() {}

#[tokio::test]
pub async fn test_op_async_void() -> Result<(), Box<dyn std::error::Error>> {
  run_async_test(JIT_ITERATIONS, "op_async_void", "await op_async_void()")
    .await?;
  Ok(())
}
```

```rust
#[op2]
async fn op_async_number(x: u32) -> u32 {
  x
}

#[op2]
async fn op_async_add(x: u32, y: u32) -> u32 {
  x.wrapping_add(y)
}

// Note: #[smi] parameters are signed in JS regardless of the sign in Rust. Overflow and underflow
// of valid ranges result in automatic wrapping.
#[op2]
#[smi]
async fn op_async_add_smi(#[smi] x: u32, #[smi] y: u32) -> u32 {
  tokio::time::sleep(Duration::from_millis(10)).await;
  x.wrapping_add(y)
}

#[tokio::test]
pub async fn test_op_async_number() -> Result<(), Box<dyn std::error::Error>>
{
  run_async_test(
    JIT_ITERATIONS,
    "op_async_number",
    "assert(await op_async_number(__index__) == __index__)",
  )
  .await?;
  run_async_test(
    JIT_ITERATIONS,
    "op_async_add",
    "assert(await op_async_add(__index__, 100) == __index__ + 100)",
  )
  .await?;
  run_async_test(
```

--------------------------------

### uv_idle_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_idle_start.html

Starts the given idle handle with the provided callback function.

```APIDOC
## uv_idle_start

### Signature
`pub unsafe extern "C" fn uv_idle_start(handle: *mut uv_idle_t, cb: uv_idle_cb) -> c_int`

### Description
Starts the idle handle. The callback will be called once per loop iteration, right before the prepare handles.

### Safety
`handle` must be a valid pointer to a `uv_idle_t` initialized by `uv_idle_init`.

### Parameters
- **handle** (*mut uv_idle_t) - Required - A pointer to an initialized idle handle.
- **cb** (uv_idle_cb) - Required - The callback function to be executed when the handle is active.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### uv_prepare_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_start.html?search=std%3A%3Avec

Starts the prepare handle. The provided callback will be called once per loop iteration, right before blocking for I/O.

```APIDOC
## Function: uv_prepare_start

### Description
Starts the prepare handle. The callback will be called once per loop iteration, right before blocking for I/O.

### Signature
`pub unsafe extern "C" fn uv_prepare_start(handle: *mut uv_prepare_t, cb: uv_prepare_cb) -> c_int`

### Parameters
- **handle** (*mut uv_prepare_t) - A pointer to a uv_prepare_t handle that must be initialized by uv_prepare_init.
- **cb** (uv_prepare_cb) - The callback function to be executed.

### Safety
This function is unsafe. The `handle` must be a valid pointer to a `uv_prepare_t` initialized by `uv_prepare_init`.
```

--------------------------------

### Retrieve match indices in strings

Source: https://docs.rs/deno_core/latest/deno_core/stats/struct.RuntimeActivityTrace.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Use match_indices or rmatch_indices to get both the start index and the matched content.

```rust
let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);

let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
assert_eq!(v, [(1, "abc"), (4, "abc")]);

let v: Vec<_> = "ababa".match_indices("aba").collect();
assert_eq!(v, [(0, "aba")]); // only the first `aba`
```

```rust
let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);

let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
assert_eq!(v, [(4, "abc"), (1, "abc")]);

let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
assert_eq!(v, [(2, "aba")]); // only the last `aba`
```

--------------------------------

### uv_prepare_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_start.html?search=

Starts the prepare handle. The callback will be called once per loop iteration, right before blocking for I/O.

```APIDOC
## uv_prepare_start

### Signature
`pub unsafe extern "C" fn uv_prepare_start(handle: *mut uv_prepare_t, cb: uv_prepare_cb) -> c_int`

### Description
Starts the prepare handle. The callback will be called once per loop iteration, right before blocking for I/O.

### Safety
`handle` must be a valid pointer to a `uv_prepare_t` initialized by `uv_prepare_init`.

### Parameters
- **handle** (*mut uv_prepare_t) - Required - A pointer to a `uv_prepare_t` handle.
- **cb** (uv_prepare_cb) - Required - The callback function to be executed.

### Returns
- **c_int** - Returns 0 on success, or an error code on failure.
```

--------------------------------

### Test V8 task spawner

Source: https://docs.rs/deno_core/latest/src/deno_core/tasks.rs.html?search=

Example test setup for the V8 task spawner using a multi-threaded runtime.

```rust
#[test]
  #[cfg(not(all(miri, target_os = "linux")))]
  fn test_spawner_serial() {
    let runtime = tokio::runtime::Builder::new_multi_thread()
      .worker_threads(1)
      .build()
      .unwrap();
    runtime.block_on(async {
      let factory = Arc::<V8TaskSpawnerFactory>::default();
      let cross_thread_spawner = factory.clone().new_cross_thread_spawner();
      let local_set = LocalSet::new();

      const COUNT: usize = 1000;
```

--------------------------------

### uv_prepare_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_start.html?search=u32+-%3E+bool

Starts the handle with the given callback. The handle must be a valid pointer to a uv_prepare_t initialized by uv_prepare_init.

```APIDOC
## Function: uv_prepare_start

### Description
Starts a libuv prepare handle. This function is unsafe and requires a valid pointer to a `uv_prepare_t` that has been previously initialized.

### Signature
`pub unsafe extern "C" fn uv_prepare_start(handle: *mut uv_prepare_t, cb: uv_prepare_cb) -> c_int`

### Parameters
- **handle** (*mut uv_prepare_t) - Required - A pointer to a `uv_prepare_t` handle initialized by `uv_prepare_init`.
- **cb** (uv_prepare_cb) - Required - The callback function to be executed.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### Test V8 task spawner

Source: https://docs.rs/deno_core/latest/src/deno_core/tasks.rs.html

Example test setup for the V8 task spawner using a multi-threaded Tokio runtime.

```rust
#[test]
  #[cfg(not(all(miri, target_os = "linux")))]
  fn test_spawner_serial() {
    let runtime = tokio::runtime::Builder::new_multi_thread()
      .worker_threads(1)
      .build()
      .unwrap();
    runtime.block_on(async {
      let factory = Arc::<V8TaskSpawnerFactory>::default();
      let cross_thread_spawner = factory.clone().new_cross_thread_spawner();
```

--------------------------------

### uv_prepare_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_start.html

Starts the handle with the given callback. The handle must be a valid pointer to a uv_prepare_t initialized by uv_prepare_init.

```APIDOC
## uv_prepare_start

### Signature
`pub unsafe extern "C" fn uv_prepare_start(handle: *mut uv_prepare_t, cb: uv_prepare_cb) -> c_int`

### Description
Starts the libuv prepare handle. This function is unsafe as it requires a valid pointer to a `uv_prepare_t` that has been previously initialized by `uv_prepare_init`.

### Parameters
- **handle** (*mut uv_prepare_t) - Required - A pointer to a libuv prepare handle.
- **cb** (uv_prepare_cb) - Required - The callback function to be executed when the prepare handle is triggered.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### uv_prepare_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_start.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Starts the handle with the given callback. The handle must be a valid pointer to a uv_prepare_t initialized by uv_prepare_init.

```APIDOC
## uv_prepare_start

### Signature
`pub unsafe extern "C" fn uv_prepare_start(handle: *mut uv_prepare_t, cb: uv_prepare_cb) -> c_int`

### Description
Starts the prepare handle. The handle must be a valid pointer to a `uv_prepare_t` initialized by `uv_prepare_init`.

### Parameters
- **handle** (*mut uv_prepare_t) - Required - A pointer to a libuv prepare handle.
- **cb** (uv_prepare_cb) - Required - The callback function to be invoked.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### Basic Box initialization

Source: https://docs.rs/deno_core/latest/deno_core/type.CustomModuleEvaluationCb.html

Demonstrates basic Box creation and pinning.

```rust
let foo = Box::new(());
let bar = Pin::from(foo);
```

--------------------------------

### Start Timer Handle

Source: https://docs.rs/deno_core/latest/src/deno_core/uv_compat.rs.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Starts a timer with a specified timeout and repeat interval.

```rust
/// ### Safety
/// `handle` must be a valid pointer to a `uv_timer_t` initialized by `uv_timer_init`.
#[cfg_attr(feature = "uv_compat_export", unsafe(no_mangle))]
pub unsafe extern "C" fn uv_timer_start(
  handle: *mut uv_timer_t,
  cb: uv_timer_cb,
  timeout: u64,
  repeat: u64,
) -> c_int {
  // SAFETY: Caller guarantees handle was initialized by uv_timer_init.
  unsafe {
    if (*handle).flags & UV_HANDLE_CLOSING != 0 {
      return UV_EINVAL;
    }
    let loop_ = (*handle).loop_;
    let inner = get_inner(loop_);

    if (*handle).flags & UV_HANDLE_ACTIVE != 0 {
      inner.stop_timer(handle);
    }

    let id = inner.alloc_timer_id();
    let now = inner.now_ms();
    let deadline = now.saturating_add(timeout);

    (*handle).cb = Some(cb);
    (*handle).timeout = timeout;
    (*handle).repeat = repeat;
    (*handle).internal_id = id;
    (*handle).internal_deadline = deadline;
    (*handle).flags |= UV_HANDLE_ACTIVE;

    let key = TimerKey {
      deadline_ms: deadline,
      id,
    };
    inner.timers.borrow_mut().insert(key);
    inner.timer_handles.borrow_mut().insert(id, handle);
  }
  0
}
```

--------------------------------

### Prepare Handle Lifecycle Management

Source: https://docs.rs/deno_core/latest/src/deno_core/uv_compat.rs.html

Initialize, start, and stop libuv prepare handles.

```rust
/// ### Safety
/// `loop_` must be initialized by `uv_loop_init`. `handle` must be a valid, writable pointer.
#[cfg_attr(feature = "uv_compat_export", unsafe(no_mangle))]
pub unsafe extern "C" fn uv_prepare_init(
  loop_: *mut uv_loop_t,
  handle: *mut uv_prepare_t,
) -> c_int {
  // SAFETY: Caller guarantees both pointers are valid.
  unsafe {
    (*handle).r#type = uv_handle_type::UV_PREPARE;
    (*handle).loop_ = loop_;
    (*handle).data = std::ptr::null_mut();
    (*handle).flags = UV_HANDLE_REF;
    (*handle).cb = None;
  }
  0
}
```

```rust
/// ### Safety
/// `handle` must be a valid pointer to a `uv_prepare_t` initialized by `uv_prepare_init`.
#[cfg_attr(feature = "uv_compat_export", unsafe(no_mangle))]
pub unsafe extern "C" fn uv_prepare_start(
  handle: *mut uv_prepare_t,
  cb: uv_prepare_cb,
) -> c_int {
  // SAFETY: Caller guarantees handle was initialized by `uv_prepare_init`.
  unsafe {
    // Match libuv: no-op if already active.
    if (*handle).flags & UV_HANDLE_ACTIVE != 0 {
      return 0;
    }
    (*handle).cb = Some(cb);
    (*handle).flags |= UV_HANDLE_ACTIVE;

    let loop_ = (*handle).loop_;
    let inner = get_inner(loop_);
    inner.prepare_handles.borrow_mut().push(handle);
  }
  0
}
```

```rust
/// ### Safety
/// `handle` must be a valid pointer to a `uv_prepare_t` initialized by `uv_prepare_init`.
#[cfg_attr(feature = "uv_compat_export", unsafe(no_mangle))]
pub unsafe extern "C" fn uv_prepare_stop(handle: *mut uv_prepare_t) -> c_int {
  // SAFETY: Caller guarantees handle was initialized by `uv_prepare_init`.
  unsafe {
    if (*handle).flags & UV_HANDLE_ACTIVE == 0 {
      return 0;
    }
    let loop_ = (*handle).loop_;
    let inner = get_inner(loop_);
    inner.stop_prepare(handle);
    (*handle).cb = None;
  }
  0
}
```

--------------------------------

### Startup Phase Tracing Utilities

Source: https://docs.rs/deno_core/latest/src/deno_core/runtime/jsruntime.rs.html?search=

Helper functions to track and log startup performance phases when the DENO_STARTUP_PHASES environment variable is enabled.

```rust
fn startup_phases_enabled() -> bool {
  static ENABLED: OnceLock<bool> = OnceLock::new();
  *ENABLED.get_or_init(|| {
    // Diagnostic env var — only consulted once per process. Bypassing
    // `sys_traits` here is intentional: the snapshot/runtime layers don't
    // thread an `EnvProvider` through this code path, and this opt-in
    // tracing is only useful when running an actual `deno` binary anyway.
    #[allow(
      clippy::disallowed_methods,
      reason = "diagnostic env var; not part of the sys_traits surface"
    )]
    let v = std::env::var_os("DENO_STARTUP_PHASES");
    v.is_some_and(|v| !v.is_empty() && v != "0")
  })
}

#[inline]
fn startup_phase_begin() -> Option<Instant> {
  if startup_phases_enabled() {
    Some(Instant::now())
  } else {
    None
  }
}

#[inline]
fn startup_phase_end(t: Option<Instant>, label: &str) {
  if let Some(start) = t {
    let elapsed = start.elapsed();
    #[allow(clippy::print_stderr, reason = "diagnostic")]
    {
      eprintln!("[startup] {label:>32}  {elapsed:?}");
    }
  }
}
```

--------------------------------

### Startup Phase Tracking Utilities

Source: https://docs.rs/deno_core/latest/src/deno_core/runtime/jsruntime.rs.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Functions to enable, begin, and end tracking of startup phases for diagnostic purposes.

```rust
fn startup_phases_enabled() -> bool {
  static ENABLED: OnceLock<bool> = OnceLock::new();
  *ENABLED.get_or_init(|| {
    // Diagnostic env var — only consulted once per process. Bypassing
    // `sys_traits` here is intentional: the snapshot/runtime layers don't
    // thread an `EnvProvider` through this code path, and this opt-in
    // tracing is only useful when running an actual `deno` binary anyway.
    #[allow(
      clippy::disallowed_methods,
      reason = "diagnostic env var; not part of the sys_traits surface"
    )]
    let v = std::env::var_os("DENO_STARTUP_PHASES");
    v.is_some_and(|v| !v.is_empty() && v != "0")
  })
}
```

```rust
#[inline]
fn startup_phase_begin() -> Option<Instant> {
  if startup_phases_enabled() {
    Some(Instant::now())
  } else {
    None
  }
}
```

```rust
#[inline]
fn startup_phase_end(t: Option<Instant>, label: &str) {
  if let Some(start) = t {
    let elapsed = start.elapsed();
    #[allow(clippy::print_stderr, reason = "diagnostic")]
    {
      eprintln!("[startup] {label:>32}  {elapsed:?}");
    }
  }
}
```

--------------------------------

### Start a libuv check handle

Source: https://docs.rs/deno_core/latest/src/deno_core/uv_compat.rs.html?search=

Starts a previously initialized check handle. If the handle is already active, this is a no-op.

```rust
#[cfg_attr(feature = "uv_compat_export", unsafe(no_mangle))]
pub unsafe extern "C" fn uv_check_start(
  handle: *mut uv_check_t,
  cb: uv_check_cb,
) -> c_int {
  // SAFETY: Caller guarantees handle was initialized by uv_check_init.
  unsafe {
    // Match libuv: no-op if already active.
    if (*handle).flags & UV_HANDLE_ACTIVE != 0 {
      return 0;
    }
    (*handle).cb = Some(cb);
    (*handle).flags |= UV_HANDLE_ACTIVE;

    let loop_ = (*handle).loop_;
    let inner = get_inner(loop_);
    inner.check_handles.borrow_mut().push(handle);
  }
  0
}
```

--------------------------------

### get<I>(i: I)

Source: https://docs.rs/deno_core/latest/deno_core/struct.FastString.html?search=u32+-%3E+bool

Returns a subslice of the string safely.

```APIDOC
## pub fn get<I>(&self, i: I) -> Option<&<I as SliceIndex<str>>::Output>

### Description
Returns a subslice of the string. This is the non-panicking alternative to indexing, returning None if the index is out of bounds or not on a UTF-8 boundary.
```

--------------------------------

### BufMutView::reset_cursor

Source: https://docs.rs/deno_core/latest/src/deno_core/io/buffers.rs.html?search=u32+-%3E+bool

Resets the cursor to the start of the buffer.

```APIDOC
## BufMutView::reset_cursor(&mut self) -> usize

### Description
Resets the internal cursor to the beginning of the buffer and returns the previous cursor position.
```

--------------------------------

### uv_prepare_init

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_init.html?search=std%3A%3Avec

Initializes a prepare handle. The loop must be initialized by uv_loop_init, and the handle must be a valid, writable pointer.

```APIDOC
## Function: uv_prepare_init

### Signature
`pub unsafe extern "C" fn uv_prepare_init(loop_: *mut uv_loop_t, handle: *mut uv_prepare_t) -> c_int`

### Description
Initializes the handle. This function is unsafe as it requires valid pointers for the loop and the handle.

### Safety
- `loop_` must be initialized by `uv_loop_init`.
- `handle` must be a valid, writable pointer.

### Parameters
- **loop_** (*mut uv_loop_t) - The event loop to associate with the handle.
- **handle** (*mut uv_prepare_t) - The prepare handle to initialize.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### uv_prepare_init

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_init.html?search=

Initializes a prepare handle. This function is part of the libuv compatibility layer in deno_core.

```APIDOC
## uv_prepare_init

### Signature
`pub unsafe extern "C" fn uv_prepare_init(loop_: *mut uv_loop_t, handle: *mut uv_prepare_t) -> c_int`

### Description
Initializes the handle to be used with a libuv prepare watcher. This function must be called before the handle is used in any other libuv functions.

### Safety
- `loop_` must be initialized by `uv_loop_init`.
- `handle` must be a valid, writable pointer.

### Parameters
- **loop_** (*mut uv_loop_t) - Required - A pointer to an initialized libuv loop.
- **handle** (*mut uv_prepare_t) - Required - A pointer to the prepare handle to initialize.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### Sort a slice

Source: https://docs.rs/deno_core/latest/deno_core/convert/struct.ByteString.html

Example of sorting a mutable slice of integers.

```rust
let mut v = [4, -5, 1, -3, 2];
```

--------------------------------

### uv_prepare_init

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_init.html?search=u32+-%3E+bool

Initializes a libuv prepare handle. This function is unsafe and requires valid pointers to an initialized loop and a writable handle.

```APIDOC
## uv_prepare_init

### Signature
`pub unsafe extern "C" fn uv_prepare_init(loop_: *mut uv_loop_t, handle: *mut uv_prepare_t) -> c_int`

### Description
Initializes the handle for a prepare watcher. This function must be called before the handle is used in any other libuv functions.

### Safety
- `loop_` must be initialized by `uv_loop_init`.
- `handle` must be a valid, writable pointer.
```

--------------------------------

### uv_listen

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_listen.html?search=

Starts listening for incoming connections on a libuv stream.

```APIDOC
## uv_listen

### Signature
`pub unsafe fn uv_listen(stream: *mut uv_stream_t, backlog: c_int, cb: Option<uv_connection_cb>) -> c_int`

### Description
Starts listening for incoming connections on the provided stream. This function is unsafe and requires the stream to be properly initialized and bound.

### Safety
`stream` must be a valid pointer to a `uv_tcp_t` (cast as `uv_stream_t`) initialized by `uv_tcp_init`, with a bind address set via `uv_tcp_bind`.

### Parameters
- **stream** (*mut uv_stream_t) - Required - A pointer to the libuv stream to listen on.
- **backlog** (c_int) - Required - The maximum length of the queue of pending connections.
- **cb** (Option<uv_connection_cb>) - Required - The callback function to be invoked when a new connection is available.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### starts_with

Source: https://docs.rs/deno_core/latest/deno_core/convert/struct.BigUint64Array.html?search=std%3A%3Avec

Returns true if the slice starts with the provided needle.

```APIDOC
## pub fn starts_with(&self, needle: &[T]) -> bool

### Description
Returns `true` if `needle` is a prefix of the slice or equal to the slice.
```

--------------------------------

### uv_prepare_init

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_init.html

Initializes a prepare handle. This function is part of the libuv compatibility layer.

```APIDOC
## uv_prepare_init

### Signature
`pub unsafe extern "C" fn uv_prepare_init(loop_: *mut uv_loop_t, handle: *mut uv_prepare_t) -> c_int`

### Description
Initializes the given `uv_prepare_t` handle to be used with the specified `uv_loop_t`.

### Safety
- `loop_` must be initialized by `uv_loop_init`.
- `handle` must be a valid, writable pointer.
```

--------------------------------

### Get URL username

Source: https://docs.rs/deno_core/latest/deno_core/type.ModuleSpecifier.html?search=std%3A%3Avec

Retrieve the percent-encoded username from the URL.

```rust
use url::Url;

let url = Url::parse("ftp://rms@example.com")?;
assert_eq!(url.username(), "rms");

let url = Url::parse("ftp://:secret123@example.com")?;
assert_eq!(url.username(), "");

let url = Url::parse("https://example.com")?;
assert_eq!(url.username(), "");
```

--------------------------------

### Op Registration and State Management

Source: https://docs.rs/deno_core/latest/src/deno_core/runtime/ops.rs.html

Example of defining op lists and initializing state within a runtime configuration.

```rust
      op_arraybuffer_slice,
      op_test_get_cppgc_resource,
      op_test_get_cppgc_resource_option,
      op_test_make_cppgc_resource,
      op_test_make_cppgc_resource_option,
      op_external_make,
      op_external_process,
      op_external_make_ptr,
      op_external_process_ptr,
      op_typed_external,
      op_typed_external_process,
      op_typed_external_take,
      op_isolate_queue_microtask,
      op_isolate_run_microtasks,

      op_async_void,
      op_async_number,
      op_async_add,
      op_async_add_smi,
      op_async_sleep,
      op_async_sleep_impl,
      op_async_sleep_error,
      op_async_deferred_error,
      op_async_deferred_success,
      op_async_lazy_error,
      op_async_lazy_success,
      op_async_result_impl,
      op_async_state_rc,
      op_async_buffer,
      op_async_buffer_vec,
      op_async_buffer_impl,
      op_async_external,
      op_async_serde_option_v8,

      op_smi_to_from_v8,
      op_number_to_from_v8,
      op_bool_to_from_v8,

      op_create_buf_u8,
      op_create_buf_u16,
      op_create_buf_u32,
      op_create_buf_u64,
      op_create_buf_i8,
      op_create_buf_i16,
      op_create_buf_i32,
      op_create_buf_i64,
      op_create_buf_f32,
      op_create_buf_f64,
    ],
    state = |state| {
      state.put(1234u32);
      state.put(10000u16);
    }
  );
```

--------------------------------

### Get Source Line

Source: https://docs.rs/deno_core/latest/deno_core/struct.SourceMapper.html?search=

Retrieves a specific line from the source.

```rust
pub fn get_source_line( &mut self, file_name: &str, line_number: i64, ) -> Option<String>
```

--------------------------------

### as_array

Source: https://docs.rs/deno_core/latest/deno_core/struct.BufMutView.html?search=u32+-%3E+bool

Gets a reference to the underlying array if the length matches.

```APIDOC
## pub fn as_array<const N: usize>(&self) -> Option<&[T; N]>

### Description
Gets a reference to the underlying array. If N is not exactly equal to the length of the slice, this method returns None.
```

--------------------------------

### Initialize Deno core namespace

Source: https://docs.rs/deno_core/latest/src/deno_core/runtime/bindings.rs.html

Sets up the globalThis.Deno object structure, including ops and console bindings.

```rust
globalThis.Deno = {
  core: {
    ops: {},
  },
  // console from V8
  console,
  // wrapper fn to forward message to V8 console
  callConsole,
};
```

```rust
pub(crate) fn initialize_deno_core_namespace<'s, 'i>(
  scope: &mut v8::PinScope<'s, 'i>,
  context: v8::Local<'s, v8::Context>,
  init_mode: InitMode,
) {
  let global = context.global(scope);
  let deno_str = DENO.v8_string(scope).unwrap();

  let maybe_deno_obj_val = global.get(scope, deno_str.into());

  // If `Deno.core` is already set up, let's exit early.
  if let Some(deno_obj_val) = maybe_deno_obj_val
    && !deno_obj_val.is_undefined()
  {
    return;
  }

  let deno_obj = v8::Object::new(scope);
  let deno_core_key = CORE.v8_string(scope).unwrap();
  // Set up `Deno.core.ops` object
  let deno_core_ops_obj = v8::Object::new(scope);
  let deno_core_ops_key = OPS.v8_string(scope).unwrap();

  let deno_core_obj = v8::Object::new(scope);
  deno_core_obj
    .set(scope, deno_core_ops_key.into(), deno_core_ops_obj.into())
    .unwrap();

  // If we're initializing fresh context set up the console
  if init_mode == InitMode::New {
    // Bind `call_console` to Deno.core.callConsole
    let call_console_fn = v8::Function::new(scope, call_console).unwrap();
    let call_console_key = CALL_CONSOLE.v8_string(scope).unwrap();
    deno_core_obj.set(scope, call_console_key.into(), call_console_fn.into());

    // Bind v8 console object to Deno.core.console
    let extra_binding_obj = context.get_extras_binding_object(scope);
    let console_obj: v8::Local<v8::Object> = get(
      scope,
      extra_binding_obj,
      CONSOLE,
      "ExtrasBindingObject.console",
    );
    let console_key = CONSOLE.v8_string(scope).unwrap();
    deno_core_obj.set(scope, console_key.into(), console_obj.into());
  }

  deno_obj.set(scope, deno_core_key.into(), deno_core_obj.into());
  global.set(scope, deno_str.into(), deno_obj.into());
}
```

--------------------------------

### Other Module Type Usage

Source: https://docs.rs/deno_core/latest/deno_core/enum.RequestedModuleType.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Example of importing a custom module type.

```javascript
import url from "./style.css" with { type: "url" };

const imgData = await import(`./images/${name}.png`, { with: { type: "image" }});
```

--------------------------------

### uv_idle_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_idle_start.html?search=

Starts the idle handle. The provided callback will be called once per loop iteration, right before the prepare handles.

```APIDOC
## uv_idle_start

### Signature
`pub unsafe extern "C" fn uv_idle_start(handle: *mut uv_idle_t, cb: uv_idle_cb) -> c_int`

### Description
Starts the idle handle. The provided callback will be called once per loop iteration, right before the prepare handles.

### Safety
`handle` must be a valid pointer to a `uv_idle_t` initialized by `uv_idle_init`.

### Parameters
- **handle** (*mut uv_idle_t) - Required - A pointer to an initialized idle handle.
- **cb** (uv_idle_cb) - Required - The callback function to be invoked.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### uv_timer_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_timer_start.html?search=

Starts the timer handle with the specified timeout and repeat interval.

```APIDOC
## uv_timer_start

### Signature
`pub unsafe extern "C" fn uv_timer_start(handle: *mut uv_timer_t, cb: uv_timer_cb, timeout: u64, repeat: u64) -> c_int`

### Description
Starts the timer handle. The callback `cb` will be triggered after `timeout` milliseconds. If `repeat` is non-zero, the timer will repeat every `repeat` milliseconds.

### Safety
`handle` must be a valid pointer to a `uv_timer_t` initialized by `uv_timer_init`.

### Parameters
- **handle** (*mut uv_timer_t) - The timer handle to start.
- **cb** (uv_timer_cb) - The callback function to be executed when the timer expires.
- **timeout** (u64) - The initial delay in milliseconds.
- **repeat** (u64) - The repeat interval in milliseconds. Set to 0 to disable repetition.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### Initialize Deno Core Ops Bindings

Source: https://docs.rs/deno_core/latest/src/deno_core/runtime/bindings.rs.html?search=

Sets up JavaScript bindings for ops by injecting functions into the Deno.core.ops object and configuring templates.

```rust
pub(crate) fn initialize_deno_core_ops_bindings<'s, 'i>(
  scope: &mut v8::PinScope<'s, 'i>,
  context: v8::Local<'s, v8::Context>,
  op_ctxs: &[OpCtx],
  op_method_decls: &[OpMethodDecl],
  methods_ctx_offset: usize,
  fn_template_store: &mut FunctionTemplateData,
  will_snapshot: bool,
) {
  let global = context.global(scope);

  // Set up JavaScript bindings for the defined op - this will insert proper
  // `v8::Function` into `Deno.core.ops` object. For async ops, there a bit
  // more machinery involved, see comment below.
  let deno_obj = get(scope, global, DENO, "Deno");
  let deno_core_obj = get(scope, deno_obj, CORE, "Deno.core");
  let deno_core_ops_obj: v8::Local<v8::Object> =
    get(scope, deno_core_obj, OPS, "Deno.core.ops");

  let set_up_async_stub_fn: v8::Local<v8::Function> = get(
    scope,
    deno_core_obj,
    SET_UP_ASYNC_STUB,
    "Deno.core.setUpAsyncStub",
  );

  let prototype_key = v8::String::new(scope, "prototype").unwrap();
  let undefined = v8::undefined(scope);
  let mut index = 0;

  for decl in op_method_decls {
    if index == methods_ctx_offset {
      break;
    }

    let tmpl = if decl.constructor.is_some() {
      let constructor_ctx = &op_ctxs[index];

      let tmpl = op_ctx_template(
        scope,
        constructor_ctx,
        v8::ConstructorBehavior::Allow,
        will_snapshot,
      );

      index += 1;

      tmpl
    } else {
      crate::cppgc::make_cppgc_template(scope)
    };

    let key = decl.name.1.v8_string(scope).unwrap();

    let method_ctxs = &op_ctxs[index..index + decl.methods.len()];
    let accessor_store = create_accessor_store(method_ctxs);

    if !will_snapshot {
      let prototype = tmpl.prototype_template(scope);
      for method in method_ctxs.iter() {
        // Skip async methods, we are going to register them later.
        if method.decl.is_async {
          continue;
        }

        op_ctx_template_or_accessor(
          &accessor_store,
          set_up_async_stub_fn,
          scope,
          prototype,
          tmpl,
          method,
          will_snapshot,
        );
      }
    }

    index += decl.methods.len();

    let static_method_ctxs = &op_ctxs[index..index + decl.static_methods.len()];
    if !will_snapshot {
      for method in static_method_ctxs.iter() {
        let op_fn = op_ctx_template(
          scope,
          method,
          v8::ConstructorBehavior::Throw,
          will_snapshot,
        );
        let method_key = name_key(scope, &method.decl);

        tmpl.set(method_key, op_fn.into());
      }
    }

    index += decl.static_methods.len();

    if !will_snapshot {
      let prototype = tmpl.prototype_template(scope);
      // Register async methods at the end since we need to create the template instance.
      for method in method_ctxs.iter() {
        if method.decl.is_async {
          op_ctx_template_or_accessor(
            &accessor_store,
            set_up_async_stub_fn,
            scope,
            prototype,
            tmpl,
            method,
            will_snapshot,
          );
        }
      }
    }

    if let Some(e) = (decl.inherits_type_name)() {
      let parent = fn_template_store.get_raw(e).unwrap();
      tmpl.inherit(v8::Local::new(scope, parent));
    }

    let op_fn = tmpl.get_function(scope).unwrap();
    op_fn.set_name(key);

    if will_snapshot {
      let prototype = op_fn
        .get(scope, prototype_key.into())
        .and_then(|p| v8::Local::<v8::Object>::try_from(p).ok())
        .unwrap();

      for method in method_ctxs.iter() {
        op_ctx_function_or_accessor(
          &accessor_store,
          set_up_async_stub_fn,
          scope,
          prototype,
          op_fn,
          method,
        );
      }

      for method in static_method_ctxs.iter() {
        let method_fn =
          op_ctx_plain_function(scope, method, v8::ConstructorBehavior::Throw);
        let method_key = name_key(scope, &method.decl);

        op_fn.set(scope, method_key.into(), method_fn.into());
      }
    }

    deno_core_ops_obj.set(scope, key.into(), op_fn.into());
  }
}
```

--------------------------------

### uv_prepare_init

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_prepare_init.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Initializes a prepare handle. This function is unsafe and requires valid pointers to an initialized loop and a writable handle.

```APIDOC
## Function: uv_prepare_init

### Signature
`pub unsafe extern "C" fn uv_prepare_init(loop_: *mut uv_loop_t, handle: *mut uv_prepare_t) -> c_int`

### Description
Initializes the handle to be used with a libuv prepare watcher.

### Safety
- `loop_` must be initialized by `uv_loop_init`.
- `handle` must be a valid, writable pointer.
```

--------------------------------

### uv_timer_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_timer_start.html?search=std%3A%3Avec

Starts the timer handle with the specified timeout and repeat interval.

```APIDOC
## Function: uv_timer_start

### Description
Starts the timer handle. The timer will expire after the `timeout` period, and if `repeat` is non-zero, it will repeat at the given interval.

### Signature
`pub unsafe extern "C" fn uv_timer_start(handle: *mut uv_timer_t, cb: uv_timer_cb, timeout: u64, repeat: u64) -> c_int`

### Parameters
- **handle** (*mut uv_timer_t) - A pointer to a `uv_timer_t` handle. Must be initialized by `uv_timer_init`.
- **cb** (uv_timer_cb) - The callback function to be invoked when the timer expires.
- **timeout** (u64) - The initial delay before the timer expires in milliseconds.
- **repeat** (u64) - The repeat interval in milliseconds. If 0, the timer will not repeat.

### Safety
This function is unsafe. The `handle` must be a valid pointer to a `uv_timer_t` initialized by `uv_timer_init`.
```

--------------------------------

### uv_timer_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_timer_start.html?search=u32+-%3E+bool

Starts the timer handle with the specified timeout and repeat interval.

```APIDOC
## uv_timer_start

### Signature
`pub unsafe extern "C" fn uv_timer_start(handle: *mut uv_timer_t, cb: uv_timer_cb, timeout: u64, repeat: u64) -> c_int`

### Description
Starts the timer handle. The callback will be triggered after the specified timeout, and if repeat is non-zero, it will repeat at the given interval.

### Safety
`handle` must be a valid pointer to a `uv_timer_t` initialized by `uv_timer_init`.

### Parameters
- **handle** (*mut uv_timer_t) - Required - A pointer to an initialized libuv timer handle.
- **cb** (uv_timer_cb) - Required - The callback function to be executed when the timer expires.
- **timeout** (u64) - Required - The initial delay in milliseconds.
- **repeat** (u64) - Required - The repeat interval in milliseconds.

### Returns
- **c_int** - Returns 0 on success, or a negative error code on failure.
```

--------------------------------

### Module Loading Entrypoints

Source: https://docs.rs/deno_core/latest/src/deno_core/modules/recursive_load.rs.html

Methods to initiate the loading process for different types of modules.

```rust
  /// Starts a new asynchronous load of the module graph for given specifier.
  ///
  /// The module corresponding for the given `specifier` will be marked as
  // "the main module" (`import.meta.main` will return `true` for this module).
  pub(crate) async fn main(
    specifier: String,
    module_map_rc: Rc<ModuleMap>,
  ) -> Result<Self, CoreError> {
    let mut load = Self::new(LoadInit::Main(specifier), module_map_rc);
    load.prepare().await?;
    Ok(load)
  }

  /// Starts a new asynchronous load of the module graph for given specifier.
  pub(crate) async fn side(
    specifier: String,
    module_map_rc: Rc<ModuleMap>,
    kind: SideModuleKind,
    code: Option<String>,
  ) -> Result<Self, CoreError> {
    let mut load = Self::new(
      LoadInit::Side {
        specifier,
        kind,
        code,
      },
      module_map_rc,
    );
    load.prepare().await?;
    Ok(load)
  }

  pub(crate) fn new_dynamic_import(
    specifier: String,
    referrer: String,
    requested_module_type: RequestedModuleType,
    phase: ModuleImportPhase,
    module_map_rc: Rc<ModuleMap>,
    resolved_specifier: Result<ModuleSpecifier, ModuleLoaderError>,
  ) -> Self {
    Self::new_with_resolved_specifier(
      LoadInit::DynamicImport(
        specifier,
        referrer,
        requested_module_type,
        phase,
      ),
      module_map_rc,
      resolved_specifier,
    )
  }
```

--------------------------------

### uv_timer_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_timer_start.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Starts the timer handle with the specified timeout and repeat interval.

```APIDOC
## Function: uv_timer_start

### Description
Starts the timer handle. The callback will be triggered after the specified timeout, and if repeat is non-zero, it will repeat at the given interval.

### Signature
`pub unsafe extern "C" fn uv_timer_start(handle: *mut uv_timer_t, cb: uv_timer_cb, timeout: u64, repeat: u64) -> c_int`

### Parameters
- **handle** (*mut uv_timer_t) - A pointer to a uv_timer_t handle initialized by uv_timer_init.
- **cb** (uv_timer_cb) - The callback function to be executed when the timer expires.
- **timeout** (u64) - The initial delay in milliseconds.
- **repeat** (u64) - The repeat interval in milliseconds.

### Safety
This function is unsafe. The `handle` must be a valid pointer to a `uv_timer_t` initialized by `uv_timer_init`.
```

--------------------------------

### uv_idle_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_idle_start.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Starts the idle handle. The callback will be called once per loop iteration, right before the prepare handles.

```APIDOC
## Function: uv_idle_start

### Signature
`pub unsafe extern "C" fn uv_idle_start(handle: *mut uv_idle_t, cb: uv_idle_cb) -> c_int`

### Description
Starts the idle handle. The callback will be called once per loop iteration, right before the prepare handles.

### Safety
`handle` must be a valid pointer to a `uv_idle_t` initialized by `uv_idle_init`.

### Parameters
- **handle** (*mut uv_idle_t) - Required - A pointer to a valid `uv_idle_t` handle.
- **cb** (uv_idle_cb) - Required - The callback function to be executed.

### Returns
- **c_int** - Returns 0 on success, or an error code on failure.
```

--------------------------------

### Format File Names

Source: https://docs.rs/deno_core/latest/src/deno_core/error.rs.html?search=std%3A%3Avec

Examples of formatting file paths with optional base URLs.

```rust
assert_eq!(file_name.file_name, expected);
    let file_name = format_file_name("file:///foo/bar.ts", None);
    assert_eq!(file_name.file_name, "file:///foo/bar.ts");

    let file_name = format_file_name(
      "file:///foo/bar.ts",
      Some(&Url::parse("file:///foo/").unwrap()),
    );
    assert_eq!(file_name.file_name, "./bar.ts");

    let file_name =
      format_file_name("file:///%E6%9D%B1%E4%BA%AC/%F0%9F%A6%95.ts", None);
    assert_eq!(file_name.file_name, "file:///東京/🦕.ts");
```

--------------------------------

### uv_timer_start

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_timer_start.html

Starts a timer handle with a specified timeout and repeat interval.

```APIDOC
## uv_timer_start

### Description
Starts the timer handle. `timeout` and `repeat` are in milliseconds. If `timeout` is zero, the callback fires on the next event loop iteration. If `repeat` is non-zero, the timer will repeat after the timeout expires.

### Signature
`pub unsafe extern "C" fn uv_timer_start(handle: *mut uv_timer_t, cb: uv_timer_cb, timeout: u64, repeat: u64) -> c_int`

### Parameters
- **handle** (*mut uv_timer_t) - Required - A valid pointer to a uv_timer_t initialized by uv_timer_init.
- **cb** (uv_timer_cb) - Required - The callback function to be invoked when the timer expires.
- **timeout** (u64) - Required - The initial delay in milliseconds.
- **repeat** (u64) - Required - The repeat interval in milliseconds.

### Safety
`handle` must be a valid pointer to a `uv_timer_t` initialized by `uv_timer_init`.
```

--------------------------------

### uv_pipe_connect

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_pipe_connect.html?search=

Starts an async connect to a Unix domain socket path.

```APIDOC
## uv_pipe_connect

### Description
Starts an async connect to a Unix domain socket path.

### Signature
`pub unsafe fn uv_pipe_connect(req: *mut uv_connect_t, pipe: *mut uv_pipe_t, path: &str, cb: Option<uv_connect_cb>) -> c_int`

### Safety
`pipe` must be a valid pointer to an initialized `uv_pipe_t`. `req` must be a valid pointer to a `uv_connect_t`.
```

--------------------------------

### uv_tcp_init

Source: https://docs.rs/deno_core/latest/deno_core/uv_compat/fn.uv_tcp_init.html

Initializes a TCP handle using a libuv loop.

```APIDOC
## uv_tcp_init

### Signature
`pub unsafe fn uv_tcp_init(loop_: *mut uv_loop_t, tcp: *mut uv_tcp_t) -> c_int`

### Description
Initializes a TCP handle. This function is part of the libuv compatibility layer.

### Safety
- `loop_` must be initialized by `uv_loop_init`.
- `tcp` must be a valid, writable pointer.
```

--------------------------------

### Trim start of string

Source: https://docs.rs/deno_core/latest/deno_core/stats/struct.RuntimeActivityTrace.html

Removes leading whitespace from a string slice.

```rust
let s = "  עברית  ";
assert!(Some('ע') == s.trim_start().chars().next());
```
Tokens:
Raw