fix: extra byte read from chunk transfer

[xinsong-cui]

Issue #

Fixes #1285

Description of changes

Adds a public property contentBytesTransferred to track the content bytes transferred, excluding chunk metadata (need to opt in internal api to access).
This allows monitor file transfer progress without counting the overhead bytes from chunk encoding.

example usage:

override fun read(sink: SdkBuffer, limit: Long): Long = delegate.read(sink, limit).also {
    if (it > 0L) {
        val bytesTransferred = chunkedSource?.contentBytesTransferred ?: it
    }
}

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[ianbotsf]

Question: I feel pretty strongly that AwsChunkedSource.read should return the number of bytes which were read from the delegate source rather than the number of bytes written to the destination sink. Can we just return totalBytesTransferred - chunkReader.chunkMetadataBytes instead of storing it in a property? What do we need the total bytes transferred for (at least, as the output from read)?

[xinsong-cui]

We still need to return totalBytes for some of our tests:

smithy-kotlin/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedTestBase.kt

Line 445 in 444ff8a

val totalBytesExpected = encodedUnsignedChunkLength(CHUNK_SIZE_BYTES) + encodedUnsignedChunkLength(0) + "\r\n".length

If we not return the totalBytesTransferred, those tests will fail.

[lauzadis]

I'm pretty sure we can find a way around that, maybe by exposing the total bytes as some kind of test utility?

[github-actions]

Affected Artifacts

Changed in size

Artifact	Pull Request (bytes)	Latest Release (bytes)	Delta (bytes)	Delta (percentage)
aws-signing-common-jvm.jar	72,458	71,836	622	0.87%