refactor(format-context): add transfer method

docs/input-format-context.md

@@ -10,7 +10,7 @@ const format = new ffmpeg.InputFormatContext(io, options[, url])
 
 ### Parameters
 
-- `io` (`IOContext` | `InputFormat`): The IO context or input format. The ownership of `io` is transferred.
+- `io` (`IOContext` | `InputFormat`): The IO context or input format. When using `IOContext`, the native handle is transferred to the format context, making the original IOContext safe to destroy multiple times.
 - `options` (`Dictionary`): Format options. Required when using `InputFormat`, ignored when using `IOContext`. The ownership of `options` is transferred.
 - `url` (`string`, optional): Media source URL. Defaults to a platform-specific value
 

docs/io-context.md

@@ -60,8 +60,7 @@ Callback function called when FFmpeg needs to seek within the data source.
 const image = require('./fixtures/image/sample.jpeg', {
   with: { type: 'binary' }
 })
-const io = new ffmpeg.IOContext(image)
-io.destroy()
+using io = new ffmpeg.IOContext(image)
 ```
 
 ### Streaming with custom read callback
@@ -105,6 +104,25 @@ const io = new ffmpeg.IOContext(4096, {
 
 ### `IOContext.destroy()`
 
-Destroys the `IOContext` and frees all associated resources. Automatically called when the object is managed by a `using` declaration.
+Destroys the `IOContext` and frees all associated resources. Automatically called when the object is managed by a `using` declaration. Safe to call multiple times - becomes a no-op after the native handle is transferred.
 
 **Returns**: `void`
+
+### `IOContext.transfer(targetIOContext)`
+
+Transfers ownership from this IOContext to another IOContext. After transfer, this IOContext becomes inactive while the target takes full ownership. This enables safe ownership transfer between objects.
+
+**Parameters:**
+
+- `targetIOContext` (`IOContext`): The IOContext instance to receive ownership
+
+**Returns**: `void`
+
+**Example:**
+
+```js
+const sourceIO = new ffmpeg.IOContext(buffer)
+const targetIO = new ffmpeg.IOContext(null, null) // Empty IOContext
+sourceIO.transfer(targetIO)
+// sourceIO is now safe to destroy, targetIO has full ownership
+```

docs/output-format-context.md

@@ -11,7 +11,7 @@ const format = new ffmpeg.OutputFormatContext(formatName, io)
 ### Parameters
 
 - `formatName` (`string`): The output format name (e.g., `'mp4'`, `'avi'`)
-- `io` (`IOContext`): The IO context for writing. The ownership of `io` is transferred.
+- `io` (`IOContext`): The IO context for writing. The native handle is transferred to the format context, making the original IOContext safe to destroy multiple times.
 
 **Returns**: A new `OutputFormatContext` instance
 

lib/format-context.js

@@ -8,7 +8,11 @@ const Dictionary = require('./dictionary')
 
 class FFmpegFormatContext {
   constructor(io) {
-    this._io = io
+    if (io) {
+      const ownedIO = new IOContext(null, null)
+      io.transfer(ownedIO)
+      this._io = ownedIO
+    }
     this._streams = []
   }
 
@@ -86,7 +90,7 @@ exports.InputFormatContext = class FFmpegInputFormatContext extends FFmpegFormat
     if (io instanceof IOContext) {
       super(io)
 
-      this._handle = binding.openInputFormatContextWithIO(io._handle)
+      this._handle = binding.openInputFormatContextWithIO(this._io._handle)
     } else if (io instanceof InputFormat) {
       super()
 
@@ -125,7 +129,7 @@ exports.OutputFormatContext = class FFmpegOutputFormatContext extends FFmpegForm
 
     if (typeof format === 'string') format = new OutputFormat(format)
 
-    this._handle = binding.openOutputFormatContext(format._handle, io._handle)
+    this._handle = binding.openOutputFormatContext(format._handle, this._io._handle)
     this._isOutput = true
   }
 

lib/io-context.js

@@ -2,6 +2,11 @@ const binding = require('../binding')
 
 module.exports = class FFmpegIOContext {
   constructor(buffer, opts = {}) {
+    if (buffer === null && opts === null) {
+      this._handle = null
+      return
+    }
+
     let offset = 0
     let len = 0
 
@@ -27,7 +32,14 @@ module.exports = class FFmpegIOContext {
   }
 
   destroy() {
-    binding.destroyIOContext(this._handle)
+    if (this._handle) {
+      binding.destroyIOContext(this._handle)
+      this._handle = null
+    }
+  }
+
+  transfer(to) {
+    to._handle = this._handle
     this._handle = null
   }
 

test/decode.js

@@ -87,7 +87,7 @@ test('decode .webm', (t) => {
 })
 
 function decodeImage(image) {
-  const io = new ffmpeg.IOContext(image)
+  using io = new ffmpeg.IOContext(image)
   using format = new ffmpeg.InputFormatContext(io)
 
   let result
@@ -123,7 +123,7 @@ function decodeImage(image) {
 }
 
 function decodeAudio(audio) {
-  const io = new ffmpeg.IOContext(audio)
+  using io = new ffmpeg.IOContext(audio)
   using format = new ffmpeg.InputFormatContext(io)
 
   let result
@@ -189,7 +189,7 @@ function decodeAudio(audio) {
 }
 
 function decodeVideo(video) {
-  const io = new ffmpeg.IOContext(video)
+  using io = new ffmpeg.IOContext(video)
   using format = new ffmpeg.InputFormatContext(io)
 
   using packet = new ffmpeg.Packet()

test/format-context.js

@@ -10,8 +10,7 @@ test('InputFormatContext should be instantiate with IOContext', (t) => {
   const image = require('./fixtures/image/sample.jpeg', {
     with: { type: 'binary' }
   })
-  const io = new ffmpeg.IOContext(image)
-
+  using io = new ffmpeg.IOContext(image)
   using inputFormatContext = new ffmpeg.InputFormatContext(io)
 
   t.ok(inputFormatContext)
@@ -76,8 +75,8 @@ test('InputFormatContext.inputFormat should expose a inputFormat getter', (t) =>
 // OutputFormatContext
 
 test('OutputFormatContext should expose an outputFormat getter', (t) => {
-  const io = new ffmpeg.IOContext(4096)
-  const outContext = new ffmpeg.OutputFormatContext(new ffmpeg.OutputFormat('webm'), io)
+  using io = new ffmpeg.IOContext(4096)
+  using outContext = new ffmpeg.OutputFormatContext(new ffmpeg.OutputFormat('webm'), io)
 
   const outputFormat = outContext.outputFormat
 

test/io-context.js

@@ -5,7 +5,7 @@ const { mediaTypes } = ffmpeg.constants
 
 test('IOContext should propagate onread throwed error properly', (t) => {
   const readError = 'read error'
-  const io = new ffmpeg.IOContext(4096, {
+  using io = new ffmpeg.IOContext(4096, {
     onread: () => {
       throw new Error(readError)
     }
@@ -26,7 +26,7 @@ test('IOContext should propagate onseek throwed error properly', (t) => {
   const seekError = 'seek error'
 
   let offset = 0
-  const io = new ffmpeg.IOContext(4096, {
+  using io = new ffmpeg.IOContext(4096, {
     onread: (buffer) => {
       const remaining = data.length - offset
       if (remaining <= 0) return 0
@@ -51,7 +51,7 @@ test('IOContext should propagate onseek throwed error properly', (t) => {
 
 test('IOContext should propagate onwrite throwed error properly', (t) => {
   const writeError = 'write error'
-  const io = new ffmpeg.IOContext(4096, {
+  using io = new ffmpeg.IOContext(4096, {
     onwrite: () => {
       throw new Error(writeError)
     }
@@ -80,7 +80,7 @@ test('IOContext streaming webm with onread', (t) => {
   })
 
   let offset = 0
-  const io = new ffmpeg.IOContext(4096, {
+  using io = new ffmpeg.IOContext(4096, {
     onread: (buffer) => {
       if (!offset) {
         t.ok(Buffer.isBuffer(buffer), 'is buffer')
@@ -112,7 +112,7 @@ test('IOContext streaming mp4 with onseek', (t) => {
   })
 
   let offset = 0
-  const io = new ffmpeg.IOContext(4096, {
+  using io = new ffmpeg.IOContext(4096, {
     onread: (buffer) => {
       if (!offset) {
         t.ok(Buffer.isBuffer(buffer), 'is buffer')
@@ -153,6 +153,20 @@ test('IOContext streaming mp4 with onseek', (t) => {
   t.is(audio.length, 34914, `audio size: got ${audio.length}, expected 34914`)
 })
 
+test('IOContext.transfer() should transfer ownership between IOContext instances', (t) => {
+  const buffer = require('./fixtures/image/sample.jpeg', {
+    with: { type: 'binary' }
+  })
+  using sourceIO = new ffmpeg.IOContext(buffer)
+  using targetIO = new ffmpeg.IOContext(null, null)
+
+  sourceIO.transfer(targetIO)
+
+  using format = new ffmpeg.InputFormatContext(targetIO)
+  t.ok(format, 'targetIO works after transfer')
+  t.pass('both IOContext instances can be destroyed safely')
+})
+
 // Helpers
 
 function runStreams(io) {

test/packet.js

@@ -230,8 +230,8 @@ function fillPacket(packet) {
   const image = require('./fixtures/image/sample.jpeg', {
     with: { type: 'binary' }
   })
-  const io = new ffmpeg.IOContext(image)
-  const format = new ffmpeg.InputFormatContext(io)
+  using io = new ffmpeg.IOContext(image)
+  using format = new ffmpeg.InputFormatContext(io)
   format.readFrame(packet)
 }
 

test/resampler.js

@@ -107,8 +107,8 @@ test('resampler with audio from aiff file', (t) => {
   const audio = require('./fixtures/audio/sample.aiff', {
     with: { type: 'binary' }
   })
-  const io = new ffmpeg.IOContext(audio)
-  const format = new ffmpeg.InputFormatContext(io)
+  using io = new ffmpeg.IOContext(audio)
+  using format = new ffmpeg.InputFormatContext(io)
 
   for (const stream of format.streams) {
     const decoder = stream.decoder()
@@ -146,16 +146,14 @@ test('resampler with audio from aiff file', (t) => {
     decoder.destroy()
     resampler.destroy()
   }
-
-  format.destroy()
 })
 
 test('resampler converts between different sample formats', (t) => {
   const audio = require('./fixtures/audio/sample.aiff', {
     with: { type: 'binary' }
   })
 
-  const io = new ffmpeg.IOContext(audio)
+  using io = new ffmpeg.IOContext(audio)
   using format = new ffmpeg.InputFormatContext(io)
   const stream = format.streams[0]
   using decoder = stream.decoder()

test/scaler.js

@@ -6,38 +6,36 @@ test('it should preseve line number in case of downscale', (t) => {
     with: { type: 'binary' }
   })
 
-  const io = new ffmpeg.IOContext(image)
+  using io = new ffmpeg.IOContext(image)
   using format = new ffmpeg.InputFormatContext(io)
 
   for (const stream of format.streams) {
     using packet = new ffmpeg.Packet()
     format.readFrame(packet)
 
     using raw = new ffmpeg.Frame()
-    using rgba = new ffmpeg.Frame()
 
     using decoder = stream.decoder()
+    decoder.open()
     decoder.sendPacket(packet)
     decoder.receiveFrame(raw)
 
-    const targetWidth = decoder.width / 2
-    const targetHeight = decoder.height / 2
-
-    rgba.width = targetWidth
-    rgba.height = targetHeight
-    rgba.pixelFormat = ffmpeg.constants.pixelFormats.RGBA
+    using rgba = new ffmpeg.Frame()
+    rgba.width = decoder.width / 2
+    rgba.height = decoder.height / 2
+    rgba.format = ffmpeg.constants.pixelFormats.RGBA
     rgba.alloc()
 
     using scaler = new ffmpeg.Scaler(
       decoder.pixelFormat,
       decoder.width,
       decoder.height,
-      rgba.pixelFormat,
+      rgba.format,
       rgba.width,
       rgba.height
     )
     const lines = scaler.scale(raw, rgba)
 
-    t.ok(lines == targetHeight)
+    t.ok(lines == rgba.height)
   }
 })