# ResolvingDataSource

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/ResolvingDataSource.java+class:androidx.media3.datasource.ResolvingDataSource)

*** ** * ** ***


```
@UnstableApi
public final class ResolvingDataSource implements DataSource
```

<br />

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`https://developer.android.com/reference/androidx/media3/datasource/DataSource` wrapper allowing just-in-time resolution of `https://developer.android.com/reference/androidx/media3/datasource/DataSpec`.

## Summary

| ### Nested types |
|---|
| `public final class https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource.Factory implements https://developer.android.com/reference/androidx/media3/datasource/DataSource.Factory` `https://developer.android.com/reference/androidx/media3/datasource/DataSource.Factory` for `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource` instances. |
| `public interface https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource.Resolver` Resolves `https://developer.android.com/reference/androidx/media3/datasource/DataSpec`. |

| ### Public constructors |
|---|
| `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource#ResolvingDataSource(androidx.media3.datasource.DataSource,androidx.media3.datasource.ResolvingDataSource.Resolver)( https://developer.android.com/reference/androidx/media3/datasource/DataSource upstreamDataSource, https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource.Resolver resolver )` |

| ### Public methods |
|---|---|
| `void` | `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource#addTransferListener(androidx.media3.datasource.TransferListener)(https://developer.android.com/reference/androidx/media3/datasource/TransferListener transferListener)` Adds a `https://developer.android.com/reference/androidx/media3/datasource/TransferListener` to listen to data transfers. |
| `void` | `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource#close()()` Closes the source. |
| `https://developer.android.com/reference/java/util/Map.html<https://developer.android.com/reference/java/lang/String.html, https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/java/lang/String.html>>` | `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource#getResponseHeaders()()` When the source is open, returns the response headers associated with the last `https://developer.android.com/reference/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` call. |
| `@https://developer.android.com/reference/androidx/annotation/Nullable https://developer.android.com/reference/android/net/Uri.html` | `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource#getUri()()` When the source is open, returns the `https://developer.android.com/reference/android/net/Uri.html` from which data is being read. |
| `long` | `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource#open(androidx.media3.datasource.DataSpec)(https://developer.android.com/reference/androidx/media3/datasource/DataSpec dataSpec)` Opens the source to read the specified data. |
| `int` | `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource#read(byte[],int,int)(byte[] buffer, int offset, int length)` Reads up to `length` bytes of data from the input. |

## Public constructors

### ResolvingDataSource

```
public ResolvingDataSource(
    DataSource upstreamDataSource,
    ResolvingDataSource.Resolver resolver
)
```

| Parameters |
|---|---|
| `https://developer.android.com/reference/androidx/media3/datasource/DataSource upstreamDataSource` | The wrapped `https://developer.android.com/reference/androidx/media3/datasource/DataSource`. |
| `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource.Resolver resolver` | The `https://developer.android.com/reference/androidx/media3/datasource/ResolvingDataSource.Resolver` to resolve the `https://developer.android.com/reference/androidx/media3/datasource/DataSpec`. |

## Public methods

### addTransferListener

```
public void addTransferListener(TransferListener transferListener)
```

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

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

### close

```
public void close()
```

Closes the source. This method must be called even if the corresponding call to `https://developer.android.com/reference/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

```
public Map<String, List<String>> getResponseHeaders()
```

When the source is open, returns the response headers associated with the last `https://developer.android.com/reference/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

```
public @Nullable Uri getUri()
```

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/androidx/media3/datasource/DataSource#open(androidx.media3.datasource.DataSpec)` in the `https://developer.android.com/reference/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/androidx/annotation/Nullable 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

```
public long open(DataSpec dataSpec)
```

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

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

| Returns |
|---|---|
| `long` | The number of bytes that can be read from the opened source. For unbounded requests (i.e., requests where `https://developer.android.com/reference/androidx/media3/datasource/DataSpec#length()` equals `https://developer.android.com/reference/androidx/media3/common/C#LENGTH_UNSET()`) this value is the resolved length of the request, or `https://developer.android.com/reference/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/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/androidx/media3/datasource/DataSourceException` can be thrown or used as a cause of the thrown exception to specify the reason of the error. |

### read

```
public int read(byte[] buffer, int offset, int length)
```

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/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 |
|---|---|
| `byte[] buffer` | A target array into which data should be written. |
| `int offset` | The offset into the target array at which to write. |
| `int length` | The maximum number of bytes to read from the input. |

| Returns |
|---|---|
| `int` | The number of bytes read, or `https://developer.android.com/reference/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. |