node-av / lib / Fifo

Class: Fifo

Defined in: src/lib/fifo.ts:42

Generic FIFO (First-In-First-Out) buffer for arbitrary data types.

Provides a thread-safe buffer for generic data elements. Unlike AudioFifo which is specialized for audio samples, Fifo can handle any data type by specifying the element size. Supports automatic growth and manual size management.

Direct mapping to FFmpeg's AVFifo.

Example

import { Fifo, FFmpegError } from 'node-av';
import { AV_FIFO_FLAG_AUTO_GROW } from 'node-av/constants';

// Create FIFO for 32-bit integers
const fifo = new Fifo();
fifo.alloc(100, 4, AV_FIFO_FLAG_AUTO_GROW);
fifo.setAutoGrowLimit(1000);

// Write data
const data = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
const written = await fifo.write(data, 2); // Write 2 elements (8 bytes)
FFmpegError.throwIfError(written, 'write');

// Read data
const outBuffer = Buffer.alloc(8);
const read = await fifo.read(outBuffer, 2); // Read 2 elements
FFmpegError.throwIfError(read, 'read');

// Cleanup
fifo.free();

See

AVFifo - FFmpeg Doxygen

Implements

• Disposable
• NativeWrapper<NativeFifo>

Constructors

Constructor

new Fifo(): Fifo

Defined in: src/lib/fifo.ts:45

Returns

Fifo

Accessors

canRead

Get Signature

get canRead(): number

Defined in: src/lib/fifo.ts:63

Number of elements that can be read from the FIFO.

Direct mapping to av_fifo_can_read().

Returns

number

---

canWrite

Get Signature

get canWrite(): number

Defined in: src/lib/fifo.ts:72

Number of elements that can be written without reallocation.

Direct mapping to av_fifo_can_write().

Returns

number

---

elemSize

Get Signature

get elemSize(): number

Defined in: src/lib/fifo.ts:81

Size in bytes of a single element.

Direct mapping to av_fifo_elem_size().

Returns

number

---

size

Get Signature

get size(): number

Defined in: src/lib/fifo.ts:54

Number of elements currently in the FIFO.

Direct mapping to av_fifo_can_read().

Returns

number

Methods

[dispose]()

[dispose](): void

Defined in: src/lib/fifo.ts:471

Dispose of the FIFO buffer.

Implements the Disposable interface for automatic cleanup. Equivalent to calling free().

Returns

void

Example

{
  using fifo = new Fifo();
  fifo.alloc(100, 4);
  // Use fifo...
} // Automatically freed when leaving scope

Implementation of

Disposable.[dispose]

---

alloc()

alloc(nbElems, elemSize, flags?): void

Defined in: src/lib/fifo.ts:120

Allocate an AVFifo buffer.

Creates a FIFO buffer with the specified element count, size and flags. The FIFO can be configured to automatically grow when full.

Direct mapping to av_fifo_alloc2().

Parameters

nbElems

number

Initial number of elements to allocate

elemSize

number

Size in bytes of each element

flags?

AVFifoFlag = AVFLAG_NONE

Optional flags (e.g., AV_FIFO_FLAG_AUTO_GROW). Defaults to 0

Returns

void

Throws

If allocation fails (ENOMEM)

Example

import { Fifo } from 'node-av';
import { AV_FIFO_FLAG_AUTO_GROW } from 'node-av/constants';

// Fixed size FIFO for 100 32-bit integers
const fifo1 = new Fifo();
fifo1.alloc(100, 4);

// Auto-growing FIFO for 8-byte structures
const fifo2 = new Fifo();
fifo2.alloc(50, 8, AV_FIFO_FLAG_AUTO_GROW);
fifo2.setAutoGrowLimit(1000); // Max 1000 elements

See

• grow To manually grow the FIFO
• setAutoGrowLimit To set auto-grow limit
• free To release the FIFO

---

free()

free(): void

Defined in: src/lib/fifo.ts:140

Free the FIFO buffer and all associated resources.

After calling this, the FIFO is invalid and must be reallocated before use.

Direct mapping to av_fifo_freep().

Returns

void

Example

fifo.free();
// FIFO is now invalid, must call alloc() before using again

See

• Symbol.dispose For automatic cleanup
• alloc To allocate

---

getNative()

getNative(): NativeFifo

Defined in: src/lib/fifo.ts:452

Internal

Get the underlying native Fifo object.

Returns

NativeFifo

The native Fifo binding object

Implementation of

NativeWrapper.getNative

---

grow()

grow(inc): number

Defined in: src/lib/fifo.ts:397

Grow the FIFO buffer by the specified number of elements.

Increases the allocated size of the FIFO by adding more space. Existing elements are preserved.

Direct mapping to av_fifo_grow2().

Parameters

inc

number

Number of additional elements to allocate

Returns

number

0 on success, negative AVERROR on error:

• AVERROR_EINVAL: Invalid size
• AVERROR_ENOMEM: Memory allocation failure

Example

import { FFmpegError } from 'node-av';

// Grow FIFO to handle more elements
const ret = fifo.grow(100);
FFmpegError.throwIfError(ret, 'grow');
console.log(`New write capacity: ${fifo.canWrite} elements`);

See

alloc For initial allocation

---

peek()

peek(buf, nbElems, offset?): Promise<number>

Defined in: src/lib/fifo.ts:329

Read elements from the FIFO without removing them.

Similar to read() but leaves the elements in the FIFO. Useful for inspecting upcoming data without consuming it. Optionally start reading from an offset.

Direct mapping to av_fifo_peek().

Parameters

buf

Buffer

Pre-allocated buffer to peek into

nbElems

number

Maximum number of elements to peek

offset?

number = 0

Offset in elements from start of FIFO. Defaults to 0

Returns

Promise<number>

Number of elements peeked (>= 0), or negative AVERROR:

• AVERROR_EINVAL: Invalid parameters or offset too large

Example

import { FFmpegError } from 'node-av';

// Peek at next 5 elements without removing them
const peekBuffer = Buffer.alloc(5 * fifo.elemSize);
const peeked = await fifo.peek(peekBuffer, 5);
FFmpegError.throwIfError(peeked, 'peek');

// Peek at elements starting at offset 10
const peeked2 = await fifo.peek(peekBuffer, 5, 10);
FFmpegError.throwIfError(peeked2, 'peek');

// Elements are still in FIFO
console.log(`FIFO still has ${fifo.canRead} elements`);

See

read To read and remove elements

---

peekSync()

peekSync(buf, nbElems, offset?): number

Defined in: src/lib/fifo.ts:367

Read elements from the FIFO without removing them synchronously. Synchronous version of peek.

Similar to readSync() but leaves the elements in the FIFO. Useful for inspecting upcoming data without consuming it. Optionally start reading from an offset.

Direct mapping to av_fifo_peek().

Parameters

buf

Buffer

Pre-allocated buffer to peek into

nbElems

number

Maximum number of elements to peek

offset?

number = 0

Offset in elements from start of FIFO. Defaults to 0

Returns

number

Number of elements peeked (>= 0), or negative AVERROR:

• AVERROR_EINVAL: Invalid parameters or offset too large

Example

import { FFmpegError } from 'node-av';

// Peek at next elements without removing them
const peekBuffer = Buffer.alloc(10 * fifo.elemSize);
const peeked = fifo.peekSync(peekBuffer, 10);
FFmpegError.throwIfError(peeked, 'peekSync');

// Elements are still in FIFO
console.log(`FIFO still has ${fifo.canRead} elements`);

See

peek For async version

---

read()

read(buf, nbElems): Promise<number>

Defined in: src/lib/fifo.ts:252

Read and remove elements from the FIFO.

Reads up to the specified number of elements from the FIFO. The elements are removed from the FIFO after reading. Buffer must be pre-allocated with sufficient size (nbElems * elemSize).

Direct mapping to av_fifo_read().

Parameters

buf

Buffer

Pre-allocated buffer to read into

nbElems

number

Maximum number of elements to read

Returns

Promise<number>

Number of elements read (>= 0), or negative AVERROR:

• AVERROR_EINVAL: Invalid parameters or insufficient buffer size

Example

import { FFmpegError } from 'node-av';

// Check available elements
const available = fifo.canRead;
if (available >= 10) {
  // Read 10 elements (40 bytes for 4-byte elements)
  const outBuffer = Buffer.alloc(40);
  const read = await fifo.read(outBuffer, 10);
  FFmpegError.throwIfError(read, 'read');
  console.log(`Read ${read} elements`);
}

See

• peek To read without removing
• canRead To check available elements

---

readSync()

readSync(buf, nbElems): number

Defined in: src/lib/fifo.ts:288

Read and remove elements from the FIFO synchronously. Synchronous version of read.

Reads up to the specified number of elements from the FIFO. The elements are removed from the FIFO after reading. Buffer must be pre-allocated with sufficient size.

Direct mapping to av_fifo_read().

Parameters

buf

Buffer

Pre-allocated buffer to read into

nbElems

number

Maximum number of elements to read

Returns

number

Number of elements read (>= 0), or negative AVERROR:

• AVERROR_EINVAL: Invalid parameters

Example

import { FFmpegError } from 'node-av';

// Read up to 20 elements
const readBuffer = Buffer.alloc(20 * fifo.elemSize);
const read = fifo.readSync(readBuffer, 20);
FFmpegError.throwIfError(read, 'readSync');

console.log(`Read ${read} elements from FIFO`);
console.log(`FIFO now has ${fifo.canRead} elements remaining`);

See

read For async version

---

reset()

reset(): void

Defined in: src/lib/fifo.ts:416

Remove all elements from the FIFO.

Empties the FIFO buffer without deallocating it. The FIFO remains allocated and ready for new data.

Direct mapping to av_fifo_reset2().

Returns

void

Example

fifo.reset();
console.log(fifo.canRead);  // 0
console.log(fifo.canWrite); // Original allocation size

---

setAutoGrowLimit()

setAutoGrowLimit(maxElems): void

Defined in: src/lib/fifo.ts:441

Set the maximum number of elements for auto-grow.

When AV_FIFO_FLAG_AUTO_GROW is set, the FIFO will automatically grow up to this limit when full. After reaching the limit, writes will fail.

Direct mapping to av_fifo_auto_grow_limit().

Parameters

maxElems

number

Maximum number of elements (0 = unlimited)

Returns

void

Example

import { AV_FIFO_FLAG_AUTO_GROW } from 'node-av/constants';

const fifo = new Fifo();
fifo.alloc(100, 4, AV_FIFO_FLAG_AUTO_GROW);
fifo.setAutoGrowLimit(10000); // Limit to 10000 elements

See

alloc For setting auto-grow flag

---

write()

write(buf, nbElems): Promise<number>

Defined in: src/lib/fifo.ts:179

Write elements to the FIFO.

Writes elements to the FIFO buffer. If AV_FIFO_FLAG_AUTO_GROW was set, automatically reallocates if more space is needed (up to auto-grow limit).

Direct mapping to av_fifo_write().

Parameters

buf

Buffer

Data buffer containing elements to write

nbElems

number

Number of elements to write

Returns

Promise<number>

Number of elements written (>= 0), or negative AVERROR:

• AVERROR_EINVAL: Invalid parameters
• AVERROR_ENOMEM: Not enough space and auto-grow failed/disabled

Example

import { FFmpegError } from 'node-av';

// Write 4 32-bit integers (16 bytes)
const data = Buffer.from([
  0x01, 0x00, 0x00, 0x00,  // 1
  0x02, 0x00, 0x00, 0x00,  // 2
  0x03, 0x00, 0x00, 0x00,  // 3
  0x04, 0x00, 0x00, 0x00,  // 4
]);
const written = await fifo.write(data, 4);
FFmpegError.throwIfError(written, 'write');
console.log(`Wrote ${written} elements`);

See

• read To retrieve elements from FIFO
• canWrite To check available space

---

writeSync()

writeSync(buf, nbElems): number

Defined in: src/lib/fifo.ts:214

Write elements to the FIFO synchronously. Synchronous version of write.

Writes elements to the FIFO buffer. Can write fewer elements than requested if space is limited and auto-grow is disabled or has reached the limit.

Direct mapping to av_fifo_write().

Parameters

buf

Buffer

Data buffer containing elements to write

nbElems

number

Number of elements to write

Returns

number

Number of elements written (>= 0), or negative AVERROR:

• AVERROR_EINVAL: Invalid parameters
• AVERROR_ENOMEM: Not enough space

Example

import { FFmpegError } from 'node-av';

const buffer = Buffer.alloc(32); // 8 elements of 4 bytes each
// Fill with data...

const written = fifo.writeSync(buffer, 8);
FFmpegError.throwIfError(written, 'writeSync');
console.log(`Wrote ${written} elements`);

See

write For async version