snvijaya commented on a change in pull request #2464:
URL: https://github.com/apache/hadoop/pull/2464#discussion_r544826406
##########
File path:
hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/AbfsInputStream.java
##########
@@ -206,11 +231,121 @@ private int readOneBlock(final byte[] b, final int off,
final int len) throws IO
fCursor += bytesRead;
fCursorAfterLastRead = fCursor;
}
+ return copyToUserBuffer(b, off, len);
+ }
+
+ private int readFileCompletely(final byte[] b, final int off, final int len)
+ throws IOException {
+ if (len == 0) {
+ return 0;
+ }
+ if (!validate(b, off, len)) {
+ return -1;
+ }
+ savePointerState();
+ // data need to be copied to user buffer from index bCursor, bCursor has
+ // to be the current fCusor
+ bCursor = (int) fCursor;
+ return optimisedRead(b, off, len, 0, contentLength);
+ }
+
+ private int readLastBlock(final byte[] b, final int off, final int len)
+ throws IOException {
+ if (len == 0) {
+ return 0;
+ }
+ if (!validate(b, off, len)) {
+ return -1;
+ }
+ savePointerState();
+ // data need to be copied to user buffer from index bCursor,
+ // AbfsInutStream buffer is going to contain data from last block start. In
+ // that case bCursor will be set to fCursor - lastBlockStart
+ long lastBlockStart = max(0, contentLength - bufferSize);
+ bCursor = (int) (fCursor - lastBlockStart);
+ // 0 if contentlength is < buffersize
+ long actualLenToRead = min(bufferSize, contentLength);
+ return optimisedRead(b, off, len, lastBlockStart, actualLenToRead);
+ }
+
+ private int optimisedRead(final byte[] b, final int off, final int len,
+ final long readFrom, final long actualLen) throws IOException {
+ fCursor = readFrom;
+ int totalBytesRead = 0;
+ int lastBytesRead = 0;
+ try {
+ buffer = new byte[bufferSize];
+ for (int i = 0;
+ i < MAX_OPTIMIZED_READ_ATTEMPTS && fCursor < contentLength; i++) {
+ lastBytesRead = readInternal(fCursor, buffer, limit,
+ (int) actualLen - limit, true);
+ if (lastBytesRead > 0) {
+ totalBytesRead += lastBytesRead;
+ limit += lastBytesRead;
+ fCursor += lastBytesRead;
+ fCursorAfterLastRead = fCursor;
+ }
+ }
+ } catch (IOException e) {
+ LOG.debug("Optimized read failed. Defaulting to readOneBlock {}", e);
+ restorePointerState();
+ return readOneBlock(b, off, len);
+ }
+ firstRead = false;
+ if (totalBytesRead < 1) {
+ return lastBytesRead;
Review comment:
Restore needed in case of no read to get the file pointer to where app
had set it earlier. Also return explicit -1 as it is a no data read case.
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