Class DenoFileStream

A read/write IOStream backed by a Deno.FsFile from Deno's native file system API.

Read-write mode (default): opens the file with { read: true, write: true }. All mutating operations (writeBlock, insert, removeBlock, truncate) are available.

Read-only mode: opens the file with { read: true } only. Any attempt to call a mutating method throws an Error.

The constructor is private. Always use one of the async factories:

const stream = await DenoFileStream.open("/path/to/audio.mp3");
const ro     = await DenoFileStream.openReadOnly("/path/to/audio.mp3");

Example

// Read-write
const stream = await DenoFileStream.open("song.mp3");
const tag    = await FileRef.open(stream);
await stream.close();

Example

// Read-only
const stream = await DenoFileStream.openReadOnly("song.flac");
const tag    = await FileRef.open(stream);
await stream.close();

Hierarchy (View Summary)

IOStream
- DenoFileStream

Index

Methods

clear close insert isOpen length name readBlock readOnly removeBlock seek tell truncate writeBlock open openReadOnly

Methods

clear

clear(): Promise<void>
Resets the stream position to the beginning of the file.

Returns Promise<void>
Overrides IOStream.clear
- Defined in toolkit/denoFileStream.ts:316

close

close(): Promise<void>
Closes the underlying Deno.FsFile. After calling close(), isOpen returns false.

Returns Promise<void>
- Defined in toolkit/denoFileStream.ts:347

insert

insert(data: ByteVector, start: number, replace?: number): Promise<void>
Inserts data at byte offset start, optionally replacing replace bytes of existing content. The position is set to start + data.length after the operation.

Because Deno.FsFile does not support in-place insertion, this method reads the tail of the file, writes the new data at start, then writes the tail back, and truncates if necessary.
Parameters
- data: ByteVector
  The bytes to insert.
- start: number
  Byte offset at which to begin the insertion.
- replace: number = 0
  Number of existing bytes to overwrite. Defaults to 0.
Returns Promise<void>
Throws
If the stream is read-only.
Overrides IOStream.insert
- Defined in toolkit/denoFileStream.ts:199

isOpen

isOpen(): boolean
Returns true if the stream has not yet been closed.

Returns boolean
Overrides IOStream.isOpen
- Defined in toolkit/denoFileStream.ts:141

length

length(): Promise<number>
Returns the total size of the file in bytes.

Returns Promise<number>
Overrides IOStream.length
- Defined in toolkit/denoFileStream.ts:326

name

name(): string
Returns the file path this stream was opened with.

Returns string
Overrides IOStream.name
- Defined in toolkit/denoFileStream.ts:131

readBlock

readBlock(length: number): Promise<ByteVector>
Reads up to length bytes from the current file position and advances the position by the number of bytes actually read.
Parameters
- length: number
  Maximum number of bytes to read.
Returns Promise<ByteVector>
Resolves with a ByteVector containing the bytes read. May be shorter than length when the end of the file is reached.
Overrides IOStream.readBlock
- Defined in toolkit/denoFileStream.ts:153

readOnly

readOnly(): boolean
Returns true if this stream was opened in read-only mode.

Returns boolean
Overrides IOStream.readOnly
- Defined in toolkit/denoFileStream.ts:136

removeBlock

removeBlock(start: number, length: number): Promise<void>
Removes length bytes beginning at byte offset start, shifting all subsequent bytes towards the beginning of the file.
Parameters
- start: number
  Byte offset of the first byte to remove.
- length: number
  Number of bytes to remove.
Returns Promise<void>
Throws
If the stream is read-only.
Overrides IOStream.removeBlock
- Defined in toolkit/denoFileStream.ts:256

seek

seek(offset: number, position?: Position): Promise<void>
Moves the read/write position within the file.
Parameters
- offset: number
  Number of bytes to move relative to position.
- position: Position = Position.Beginning
  Reference point for the seek. Defaults to Position.Beginning.
Returns Promise<void>
Overrides IOStream.seek
- Defined in toolkit/denoFileStream.ts:301

tell

tell(): Promise<number>
Returns the current read/write position in bytes from the start of the file.

Returns Promise<number>
Overrides IOStream.tell
- Defined in toolkit/denoFileStream.ts:321

truncate

truncate(length: number): Promise<void>
Truncates or zero-extends the file to exactly length bytes.
Parameters
- length: number
  The desired file length in bytes.
Returns Promise<void>
Throws
If the stream is read-only.
Overrides IOStream.truncate
- Defined in toolkit/denoFileStream.ts:336

writeBlock

writeBlock(data: ByteVector): Promise<void>
Writes data at the current file position, extending the file if necessary, and advances the position by data.length.
Parameters
- data: ByteVector
  The bytes to write.
Returns Promise<void>
Throws
If the stream is read-only.
Overrides IOStream.writeBlock
- Defined in toolkit/denoFileStream.ts:175

`Static`open

open(path: string, create?: boolean): Promise<DenoFileStream>
Opens a file at path for reading and optionally writing.

Internally calls:
```
await Deno.open(path, { read: true, write: true, create: create ?? false })
```
Parameters
- path: string
  Absolute or relative path to the file.
- Optionalcreate: boolean
  When true the file is created if it does not exist. Defaults to false.
Returns Promise<DenoFileStream>
A fully initialised DenoFileStream in read-write mode.
- Defined in toolkit/denoFileStream.ts:105

`Static`openReadOnly

openReadOnly(path: string): Promise<DenoFileStream>
Opens a file at path for reading only.

Internally calls:
```
await Deno.open(path, { read: true })
```
Parameters
- path: string
  Absolute or relative path to the file.
Returns Promise<DenoFileStream>
A fully initialised DenoFileStream in read-only mode.
- Defined in toolkit/denoFileStream.ts:121

Class DenoFileStream

Example

Example

Hierarchy (View Summary)

Index

Methods

Methods

clear

Returns Promise<void>

close

Returns Promise<void>

insert

Parameters

Returns Promise<void>

Throws

isOpen

Returns boolean

length

Returns Promise<number>

name

Returns string

readBlock

Parameters

Returns Promise<ByteVector>

readOnly

Returns boolean

removeBlock

Parameters

Returns Promise<void>

Throws

seek

Parameters

Returns Promise<void>

tell

Returns Promise<number>

truncate

Parameters

Returns Promise<void>

Throws

writeBlock

Parameters

Returns Promise<void>

Throws

Staticopen

Parameters

Returns Promise<DenoFileStream>

StaticopenReadOnly

Parameters

Returns Promise<DenoFileStream>

Settings

On This Page

`Static`open

`Static`openReadOnly