Refactor ExtractorInput javadoc about allowEndOfInput

This parameter is a little confusing, especially as the behaviour
can be surprising if the intended use-case isn't clear. This change
moves the description of the parameter into the class javadoc,
adds context/justification and slims down each method's
javadoc to refer to the class-level.

Related to investigating/fixing issue:#6700

PiperOrigin-RevId: 283724826

library/core/src/main/java/com/google/android/exoplayer2/extractor/ExtractorInput.java

@@ -18,9 +18,50 @@ package com.google.android.exoplayer2.extractor;
 import com.google.android.exoplayer2.C;
 import java.io.EOFException;
 import java.io.IOException;
+import java.io.InputStream;
 
 /**
  * Provides data to be consumed by an {@link Extractor}.
+ *
+ * <p>This interface provides two modes of accessing the underlying input. See the subheadings below
+ * for more info about each mode.
+ *
+ * <ul>
+ *   <li>The {@code read()} and {@code skip()} methods provide {@link InputStream}-like byte-level
+ *       access operations.
+ *   <li>The {@code read/skip/peekFully()} and {@code advancePeekPosition()} methods assume the user
+ *       wants to read an entire block/frame/header of known length.
+ * </ul>
+ *
+ * <h4>{@link InputStream}-like methods</h4>
+ *
+ * <p>The {@code read()} and {@code skip()} methods provide {@link InputStream}-like byte-level
+ * access operations. The {@code length} parameter is a maximum, and each method returns the number
+ * of bytes actually processed. This may be less than {@code length} because the end of the input
+ * was reached, or the method was interrupted, or the operation was aborted early for another
+ * reason.
+ *
+ * <h4>Block-based methods</h4>
+ *
+ * <p>The {@code read/skip/peekFully()} and {@code advancePeekPosition()} methods assume the user
+ * wants to read an entire block/frame/header of known length.
+ *
+ * <p>These methods all have a variant that takes a boolean {@code allowEndOfInput} parameter. This
+ * parameter is intended to be set to true when the caller believes the input might be fully
+ * exhausted before the call is made (i.e. they've previously read/skipped/peeked the final
+ * block/frame/header). It's <b>not</b> intended to allow a partial read (i.e. greater than 0 bytes,
+ * but less than {@code length}) to succeed - this will always throw an {@link EOFException} from
+ * these methods (a partial read is assumed to indicate a malformed block/frame/header - and
+ * therefore a malformed file).
+ *
+ * <p>The expected behaviour of the block-based methods is therefore:
+ *
+ * <ul>
+ *   <li>Already at end-of-input and {@code allowEndOfInput=false}: Throw {@link EOFException}.
+ *   <li>Already at end-of-input and {@code allowEndOfInput=true}: Return {@code false}.
+ *   <li>Encounter end-of-input during read/skip/peek/advance: Throw {@link EOFException}
+ *       (regardless of {@code allowEndOfInput}).
+ * </ul>
  */
 public interface ExtractorInput {
 
@@ -41,22 +82,16 @@ public interface ExtractorInput {
 
   /**
    * Like {@link #read(byte[], int, int)}, but reads the requested {@code length} in full.
-   * <p>
-   * If the end of the input is found having read no data, then behavior is dependent on
-   * {@code allowEndOfInput}. If {@code allowEndOfInput == true} then {@code false} is returned.
-   * Otherwise an {@link EOFException} is thrown.
-   * <p>
-   * Encountering the end of input having partially satisfied the read is always considered an
-   * error, and will result in an {@link EOFException} being thrown.
    *
    * @param target A target array into which data should be written.
    * @param offset The offset into the target array at which to write.
    * @param length The number of bytes to read from the input.
    * @param allowEndOfInput True if encountering the end of the input having read no data is
    *     allowed, and should result in {@code false} being returned. False if it should be
-   *     considered an error, causing an {@link EOFException} to be thrown.
-   * @return True if the read was successful. False if the end of the input was encountered having
-   *     read no data.
+   *     considered an error, causing an {@link EOFException} to be thrown. See note in class
+   *     Javadoc.
+   * @return True if the read was successful. False if {@code allowEndOfInput=true} and the end of
+   *     the input was encountered having read no data.
    * @throws EOFException If the end of input was encountered having partially satisfied the read
    *     (i.e. having read at least one byte, but fewer than {@code length}), or if no bytes were
    *     read and {@code allowEndOfInput} is false.
@@ -94,9 +129,10 @@ public interface ExtractorInput {
    * @param length The number of bytes to skip from the input.
    * @param allowEndOfInput True if encountering the end of the input having skipped no data is
    *     allowed, and should result in {@code false} being returned. False if it should be
-   *     considered an error, causing an {@link EOFException} to be thrown.
-   * @return True if the skip was successful. False if the end of the input was encountered having
-   *     skipped no data.
+   *     considered an error, causing an {@link EOFException} to be thrown. See note in class
+   *     Javadoc.
+   * @return True if the skip was successful. False if {@code allowEndOfInput=true} and the end of
+   *     the input was encountered having skipped no data.
    * @throws EOFException If the end of input was encountered having partially satisfied the skip
    *     (i.e. having skipped at least one byte, but fewer than {@code length}), or if no bytes were
    *     skipped and {@code allowEndOfInput} is false.
@@ -121,12 +157,8 @@ public interface ExtractorInput {
   /**
    * Peeks {@code length} bytes from the peek position, writing them into {@code target} at index
    * {@code offset}. The current read position is left unchanged.
-   * <p>
-   * If the end of the input is found having peeked no data, then behavior is dependent on
-   * {@code allowEndOfInput}. If {@code allowEndOfInput == true} then {@code false} is returned.
-   * Otherwise an {@link EOFException} is thrown.
-   * <p>
-   * Calling {@link #resetPeekPosition()} resets the peek position to equal the current read
+   *
+   * <p>Calling {@link #resetPeekPosition()} resets the peek position to equal the current read
    * position, so the caller can peek the same data again. Reading or skipping also resets the peek
    * position.
    *
@@ -135,9 +167,10 @@ public interface ExtractorInput {
    * @param length The number of bytes to peek from the input.
    * @param allowEndOfInput True if encountering the end of the input having peeked no data is
    *     allowed, and should result in {@code false} being returned. False if it should be
-   *     considered an error, causing an {@link EOFException} to be thrown.
-   * @return True if the peek was successful. False if the end of the input was encountered having
-   *     peeked no data.
+   *     considered an error, causing an {@link EOFException} to be thrown. See note in class
+   *     Javadoc.
+   * @return True if the peek was successful. False if {@code allowEndOfInput=true} and the end of
+   *     the input was encountered having peeked no data.
    * @throws EOFException If the end of input was encountered having partially satisfied the peek
    *     (i.e. having peeked at least one byte, but fewer than {@code length}), or if no bytes were
    *     peeked and {@code allowEndOfInput} is false.
@@ -165,18 +198,16 @@ public interface ExtractorInput {
   void peekFully(byte[] target, int offset, int length) throws IOException, InterruptedException;
 
   /**
-   * Advances the peek position by {@code length} bytes.
-   * <p>
-   * If the end of the input is encountered before advancing the peek position, then behavior is
-   * dependent on {@code allowEndOfInput}. If {@code allowEndOfInput == true} then {@code false} is
-   * returned. Otherwise an {@link EOFException} is thrown.
+   * Advances the peek position by {@code length} bytes. Like {@link #peekFully(byte[], int, int,
+   * boolean)} except the data is skipped instead of read.
    *
    * @param length The number of bytes by which to advance the peek position.
    * @param allowEndOfInput True if encountering the end of the input before advancing is allowed,
    *     and should result in {@code false} being returned. False if it should be considered an
-   *     error, causing an {@link EOFException} to be thrown.
-   * @return True if advancing the peek position was successful. False if the end of the input was
-   *     encountered before the peek position could be advanced.
+   *     error, causing an {@link EOFException} to be thrown. See note in class Javadoc.
+   * @return True if advancing the peek position was successful. False if {@code
+   *     allowEndOfInput=true} and the end of the input was encountered before advancing over any
+   *     data.
    * @throws EOFException If the end of input was encountered having partially advanced (i.e. having
    *     advanced by at least one byte, but fewer than {@code length}), or if the end of input was
    *     encountered before advancing and {@code allowEndOfInput} is false.
@@ -187,7 +218,8 @@ public interface ExtractorInput {
       throws IOException, InterruptedException;
 
   /**
-   * Advances the peek position by {@code length} bytes.
+   * Advances the peek position by {@code length} bytes. Like {@link #peekFully(byte[], int, int,)}
+   * except the data is skipped instead of read.
    *
    * @param length The number of bytes to peek from the input.
    * @throws EOFException If the end of input was encountered.