# CacheDataSource

Artifact: [androidx.media3:media3-datasource](https://developer.android.com/jetpack/androidx/releases/media3) [View Source](https://cs.android.com/search?q=file:androidx/media3/datasource/cache/CacheDataSource.java+class:androidx.media3.datasource.cache.CacheDataSource)

*** ** * ** ***

<br />

```
@UnstableApi
class CacheDataSource : DataSource
```

<br />

*** ** * ** ***

A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` that reads and writes a `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache`. Requests are fulfilled from the cache when possible. When data is not cached it is requested from an upstream `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and written into the cache.

## Summary

| ### Nested types |
|---|
| `@https://developer.android.com/reference/java/lang/annotation/Documented.html @https://developer.android.com/reference/java/lang/annotation/Retention.html(value = https://developer.android.com/reference/java/lang/annotation/RetentionPolicy.html#SOURCE) @https://developer.android.com/reference/java/lang/annotation/Target.html(value = ) @https://developer.android.com/reference/kotlin/androidx/annotation/IntDef(value = ) annotation https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.CacheIgnoredReason` Reasons the cache may be ignored. |
| `interface https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.EventListener` Listener of `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource` events. |
| `class https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.Factory : https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource.Factory` `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource.Factory` for `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource` instances. |
| `@https://developer.android.com/reference/java/lang/annotation/Documented.html @https://developer.android.com/reference/java/lang/annotation/Retention.html(value = https://developer.android.com/reference/java/lang/annotation/RetentionPolicy.html#SOURCE) @https://developer.android.com/reference/java/lang/annotation/Target.html(value = https://developer.android.com/reference/java/lang/annotation/ElementType.html#TYPE_USE) @https://developer.android.com/reference/kotlin/androidx/annotation/IntDef(flag = true, value = ) annotation https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.Flags` Flags controlling the CacheDataSource's behavior. |

| ### Constants |
|---|---|
| `const https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#CACHE_IGNORED_REASON_ERROR() = 0` Cache ignored due to a cache related error. |
| `const https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#CACHE_IGNORED_REASON_UNSET_LENGTH() = 1` Cache ignored due to a request with an unset length. |
| `const https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_BLOCK_ON_CACHE() = 1` A flag indicating whether we will block reads if the cache key is locked. |
| `const https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS() = 4` A flag indicating that the cache should be bypassed for requests whose lengths are unset. |
| `const https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_IGNORE_CACHE_ON_ERROR() = 2` A flag indicating whether the cache is bypassed following any cache related error. |

| ### Public constructors |
|---|
| `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#CacheDataSource(androidx.media3.datasource.cache.Cache,androidx.media3.datasource.DataSource)(cache: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!, upstreamDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource?)` Constructs an instance with default `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` instances for reading and writing the cache. |
| `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#CacheDataSource(androidx.media3.datasource.cache.Cache,androidx.media3.datasource.DataSource,int)( cache: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!, upstreamDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource?, @https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.Flags flags: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html )` Constructs an instance with default `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` instances for reading and writing the cache. |
| `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#CacheDataSource(androidx.media3.datasource.cache.Cache,androidx.media3.datasource.DataSource,androidx.media3.datasource.DataSource,androidx.media3.datasource.DataSink,int,androidx.media3.datasource.cache.CacheDataSource.EventListener)( cache: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!, upstreamDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource?, cacheReadDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource!, cacheWriteDataSink: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink?, @https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.Flags flags: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html, eventListener: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.EventListener? )` Constructs an instance with arbitrary `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` instances for reading and writing the cache. |
| `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#CacheDataSource(androidx.media3.datasource.cache.Cache,androidx.media3.datasource.DataSource,androidx.media3.datasource.DataSource,androidx.media3.datasource.DataSink,int,androidx.media3.datasource.cache.CacheDataSource.EventListener,androidx.media3.datasource.cache.CacheKeyFactory)( cache: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!, upstreamDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource?, cacheReadDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource!, cacheWriteDataSink: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink?, @https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.Flags flags: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html, eventListener: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.EventListener?, cacheKeyFactory: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheKeyFactory? )` Constructs an instance with arbitrary `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` instances for reading and writing the cache. |

| ### Public functions |
|---|---|
| `https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-unit/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#addTransferListener(androidx.media3.datasource.TransferListener)(transferListener: https://developer.android.com/reference/kotlin/androidx/media3/datasource/TransferListener!)` Adds a `https://developer.android.com/reference/kotlin/androidx/media3/datasource/TransferListener` to listen to data transfers. |
| `https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-unit/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#close()()` Closes the source. |
| `(https://kotlinlang.org/api/core/kotlin-stdlib/kotlin.collections/-mutable-map/index.html)https://kotlinlang.org/api/core/kotlin-stdlib/kotlin.collections/-map/index.html<https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-string/index.html!, (https://kotlinlang.org/api/core/kotlin-stdlib/kotlin.collections/-mutable-list/index.html)https://kotlinlang.org/api/core/kotlin-stdlib/kotlin.collections/-list/index.html<https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-string/index.html!>!>!` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#getResponseHeaders()()` When the source is open, returns the response headers associated with the last `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` call. |
| `https://developer.android.com/reference/android/net/Uri.html?` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#getUri()()` When the source is open, returns the `https://developer.android.com/reference/android/net/Uri.html` from which data is being read. |
| `https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-long/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#open(androidx.media3.datasource.DataSpec)(dataSpec: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec!)` Opens the source to read the specified data. |
| `https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#read(byte[],int,int)(buffer: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-byte-array/index.html<https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-byte/index.html>!, offset: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html, length: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html)` Reads up to `length` bytes of data from the input. |

| ### Public properties |
|---|---|
| `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#cache()` |
| `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheKeyFactory!` | `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#cacheKeyFactory()` |

## Constants

### CACHE_IGNORED_REASON_ERROR

```
const val CACHE_IGNORED_REASON_ERROR = 0: Int
```

Cache ignored due to a cache related error.

### CACHE_IGNORED_REASON_UNSET_LENGTH

```
const val CACHE_IGNORED_REASON_UNSET_LENGTH = 1: Int
```

Cache ignored due to a request with an unset length.

### FLAG_BLOCK_ON_CACHE

```
const val FLAG_BLOCK_ON_CACHE = 1: Int
```

A flag indicating whether we will block reads if the cache key is locked. If unset then data is read from upstream if the cache key is locked, regardless of whether the data is cached.

### FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS

```
const val FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS = 4: Int
```

A flag indicating that the cache should be bypassed for requests whose lengths are unset. This flag is provided for legacy reasons only.

### FLAG_IGNORE_CACHE_ON_ERROR

```
const val FLAG_IGNORE_CACHE_ON_ERROR = 2: Int
```

A flag indicating whether the cache is bypassed following any cache related error. If set then cache related exceptions may be thrown for one cycle of open, read and close calls. Subsequent cycles of these calls will then bypass the cache.

## Public constructors

### CacheDataSource

```
CacheDataSource(cache: Cache!, upstreamDataSource: DataSource?)
```

Constructs an instance with default `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` instances for reading and writing the cache.

| Parameters |
|---|---|
| `cache: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!` | The cache. |
| `upstreamDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource?` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` for reading data not in the cache. If null, reading will fail if a cache miss occurs. |

### CacheDataSource

```
CacheDataSource(
    cache: Cache!,
    upstreamDataSource: DataSource?,
    @CacheDataSource.Flags flags: Int
)
```

Constructs an instance with default `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` instances for reading and writing the cache.

| Parameters |
|---|---|
| `cache: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!` | The cache. |
| `upstreamDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource?` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` for reading data not in the cache. If null, reading will fail if a cache miss occurs. |
| `@https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.Flags flags: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | A combination of `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_BLOCK_ON_CACHE()`, `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_IGNORE_CACHE_ON_ERROR()` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS()`, or 0. |

### CacheDataSource

```
CacheDataSource(
    cache: Cache!,
    upstreamDataSource: DataSource?,
    cacheReadDataSource: DataSource!,
    cacheWriteDataSink: DataSink?,
    @CacheDataSource.Flags flags: Int,
    eventListener: CacheDataSource.EventListener?
)
```

Constructs an instance with arbitrary `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` instances for reading and writing the cache. One use of this constructor is to allow data to be transformed before it is written to disk.

| Parameters |
|---|---|
| `cache: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!` | The cache. |
| `upstreamDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource?` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` for reading data not in the cache. If null, reading will fail if a cache miss occurs. |
| `cacheReadDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource!` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` for reading data from the cache. |
| `cacheWriteDataSink: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink?` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` for writing data to the cache. If null, cache is accessed read-only. |
| `@https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.Flags flags: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | A combination of `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_BLOCK_ON_CACHE()`, `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_IGNORE_CACHE_ON_ERROR()` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS()`, or 0. |
| `eventListener: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.EventListener?` | An optional `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.EventListener` to receive events. |

### CacheDataSource

```
CacheDataSource(
    cache: Cache!,
    upstreamDataSource: DataSource?,
    cacheReadDataSource: DataSource!,
    cacheWriteDataSink: DataSink?,
    @CacheDataSource.Flags flags: Int,
    eventListener: CacheDataSource.EventListener?,
    cacheKeyFactory: CacheKeyFactory?
)
```

Constructs an instance with arbitrary `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` instances for reading and writing the cache. One use of this constructor is to allow data to be transformed before it is written to disk.

| Parameters |
|---|---|
| `cache: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/Cache!` | The cache. |
| `upstreamDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource?` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` for reading data not in the cache. If null, reading will fail if a cache miss occurs. |
| `cacheReadDataSource: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource!` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource` for reading data from the cache. |
| `cacheWriteDataSink: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink?` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSink` for writing data to the cache. If null, cache is accessed read-only. |
| `@https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.Flags flags: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | A combination of `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_BLOCK_ON_CACHE()`, `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_IGNORE_CACHE_ON_ERROR()` and `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource#FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS()`, or 0. |
| `eventListener: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.EventListener?` | An optional `https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheDataSource.EventListener` to receive events. |
| `cacheKeyFactory: https://developer.android.com/reference/kotlin/androidx/media3/datasource/cache/CacheKeyFactory?` | An optional factory for cache keys. |

## Public functions

### addTransferListener

```
fun addTransferListener(transferListener: TransferListener!): Unit
```

Adds a `https://developer.android.com/reference/kotlin/androidx/media3/datasource/TransferListener` to listen to data transfers. This method is not thread-safe.

| Parameters |
|---|---|
| `transferListener: https://developer.android.com/reference/kotlin/androidx/media3/datasource/TransferListener!` | A `https://developer.android.com/reference/kotlin/androidx/media3/datasource/TransferListener`. |

### close

```
fun close(): Unit
```

Closes the source. This method must be called even if the corresponding call to `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` threw an `https://developer.android.com/reference/java/io/IOException.html`.

| Throws |
|---|---|
| `https://developer.android.com/reference/java/io/IOException.html` | If an error occurs closing the source. |

### getResponseHeaders

```
fun getResponseHeaders(): (Mutable)Map<String!, (Mutable)List<String!>!>!
```

When the source is open, returns the response headers associated with the last `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` call. Otherwise, returns an empty map.

Key look-up in the returned map is case-insensitive.

### getUri

```
fun getUri(): Uri?
```

When the source is open, returns the `https://developer.android.com/reference/android/net/Uri.html` from which data is being read. The returned `https://developer.android.com/reference/android/net/Uri.html` will be identical to the one passed `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` in the `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec` unless redirection has occurred. If redirection has occurred, the `https://developer.android.com/reference/android/net/Uri.html` after redirection is returned.

| Returns |
|---|---|
| `https://developer.android.com/reference/android/net/Uri.html?` | The `https://developer.android.com/reference/android/net/Uri.html` from which data is being read, or null if the source is not open. |

### open

```
fun open(dataSpec: DataSpec!): Long
```

Opens the source to read the specified data. If an `https://developer.android.com/reference/java/io/IOException.html` is thrown, callers must still call `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource#close()` to ensure that any partial effects of the invocation are cleaned up.

The following edge case behaviors apply:

- If the `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec#position()` is within the resource, but the `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec#length()` extends beyond the end of the resource, then `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` will succeed and data from the requested position to the end of the resource will be made available through `https://developer.android.com/reference/kotlin/androidx/media3/common/DataReader#read(byte[],int,int)`.
- If the `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec#position()` is equal to the length of the resource, then `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` will succeed, and `https://developer.android.com/reference/kotlin/androidx/media3/common/DataReader#read(byte[],int,int)` will immediately return `https://developer.android.com/reference/kotlin/androidx/media3/common/C#RESULT_END_OF_INPUT()`.
- If the `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec#position()` is greater than the length of the resource, then `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` will throw an `https://developer.android.com/reference/java/io/IOException.html` for which `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSourceException#isCausedByPositionOutOfRange(java.io.IOException)` will be `true`.

| Parameters |
|---|---|
| `dataSpec: https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec!` | Defines the data to be read. |

| Returns |
|---|---|
| `https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-long/index.html` | The number of bytes that can be read from the opened source. For unbounded requests (i.e., requests where `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec#length()` equals `https://developer.android.com/reference/kotlin/androidx/media3/common/C#LENGTH_UNSET()`) this value is the resolved length of the request, or `https://developer.android.com/reference/kotlin/androidx/media3/common/C#LENGTH_UNSET()` if the length is still unresolved. For all other requests, the value returned will be equal to the request's `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSpec#length()`. |

| Throws |
|---|---|
| `https://developer.android.com/reference/java/io/IOException.html` | If an error occurs opening the source. `https://developer.android.com/reference/kotlin/androidx/media3/datasource/DataSourceException` can be thrown or used as a cause of the thrown exception to specify the reason of the error. |

### read

```
fun read(buffer: ByteArray<Byte>!, offset: Int, length: Int): Int
```

Reads up to `length` bytes of data from the input.

If `readLength` is zero then 0 is returned. Otherwise, if no data is available because the end of the opened range has been reached, then `https://developer.android.com/reference/kotlin/androidx/media3/common/C#RESULT_END_OF_INPUT()` is returned. Otherwise, the call will block until at least one byte of data has been read and the number of bytes read is returned.

| Parameters |
|---|---|
| `buffer: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-byte-array/index.html<https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-byte/index.html>!` | A target array into which data should be written. |
| `offset: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | The offset into the target array at which to write. |
| `length: https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | The maximum number of bytes to read from the input. |

| Returns |
|---|---|
| `https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-int/index.html` | The number of bytes read, or `https://developer.android.com/reference/kotlin/androidx/media3/common/C#RESULT_END_OF_INPUT()` if the input has ended. This may be less than `length` because the end of the input (or available data) was reached, the method was interrupted, or the operation was aborted early for another reason. |

| Throws |
|---|---|
| `https://developer.android.com/reference/java/io/IOException.html` | If an error occurs reading from the input. |

## Public properties

### cache

```
val cache: Cache!
```

### cacheKeyFactory

```
val cacheKeyFactory: CacheKeyFactory!
```