adds methods to obtain shreds' erasure coded block and index (#21325)
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@ -460,6 +460,44 @@ impl Shred {
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self.common_header.version
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}
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// Returns the block index within the erasure coding set.
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fn erasure_block_index(&self) -> Option<usize> {
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let fec_set_index = self.common_header.fec_set_index;
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let index = self.index().checked_sub(fec_set_index)? as usize;
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match self.shred_type() {
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ShredType::Data => Some(index),
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ShredType::Code => {
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let num_data_shreds = self.coding_header.num_data_shreds as usize;
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let num_coding_shreds = self.coding_header.num_coding_shreds as usize;
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let fec_set_size = num_data_shreds.checked_add(num_coding_shreds)?;
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let index = index.checked_add(num_data_shreds)?;
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(index < fec_set_size).then(|| index)
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}
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}
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}
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// Returns the portion of the shred's payload which is erasure coded.
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fn erasure_block(self) -> Vec<u8> {
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let shred_type = self.shred_type();
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let mut block = self.payload;
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match shred_type {
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ShredType::Data => {
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// SIZE_OF_CODING_SHRED_HEADERS bytes at the end of data shreds
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// is never used and is not part of erasure coding.
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let size = SHRED_PAYLOAD_SIZE - SIZE_OF_CODING_SHRED_HEADERS;
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block.resize(size, 0u8);
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}
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ShredType::Code => {
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// SIZE_OF_CODING_SHRED_HEADERS bytes at the begining of the
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// coding shreds contains the header and is not part of erasure
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// coding.
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let offset = SIZE_OF_CODING_SHRED_HEADERS.min(block.len());
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block.drain(..offset);
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}
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}
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block
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}
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pub fn set_index(&mut self, index: u32) {
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self.common_header.index = index;
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Self::serialize_obj_into(
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@ -869,7 +907,6 @@ impl Shredder {
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));
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let num_data_shreds = num_data_shreds as usize;
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let num_coding_shreds = num_coding_shreds as usize;
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let fec_set_index = fec_set_index as usize;
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let fec_set_size = num_data_shreds + num_coding_shreds;
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if num_coding_shreds == 0 || shreds.len() >= fec_set_size {
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return Ok(Vec::default());
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@ -878,42 +915,28 @@ impl Shredder {
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let mut mask = vec![false; num_data_shreds];
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let mut blocks = vec![None; fec_set_size];
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for shred in shreds {
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if (shred.index() as usize) < fec_set_index {
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return Err(InvalidIndex);
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}
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let shred_is_data = shred.is_data();
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let offset = if shred_is_data { 0 } else { num_data_shreds };
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let index = offset + shred.index() as usize - fec_set_index;
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let mut block = shred.payload;
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if shred_is_data {
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if index >= num_data_shreds {
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return Err(InvalidIndex);
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}
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mask[index] = true;
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// SIZE_OF_CODING_SHRED_HEADERS bytes at the end of data shreds
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// is never used and is not part of erasure coding.
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block.resize(SHRED_PAYLOAD_SIZE - SIZE_OF_CODING_SHRED_HEADERS, 0u8);
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} else {
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if index >= fec_set_size {
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return Err(InvalidIndex);
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}
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// SIZE_OF_CODING_SHRED_HEADERS bytes at the begining of the
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// coding shreds contains the header and is not part of erasure
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// coding.
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block.drain(..SIZE_OF_CODING_SHRED_HEADERS);
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let index = match shred.erasure_block_index() {
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Some(index) if index < fec_set_size => index,
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_ => return Err(InvalidIndex),
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};
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blocks[index] = Some(block);
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blocks[index] = Some(shred.erasure_block());
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if index < num_data_shreds {
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mask[index] = true;
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}
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}
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Session::new(num_data_shreds, num_coding_shreds)?.decode_blocks(&mut blocks)?;
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let data_shred_indices = fec_set_index..fec_set_index + num_data_shreds;
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let recovered_data = mask
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.into_iter()
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.zip(blocks)
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.filter(|(mask, _)| !mask)
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.filter_map(|(_, block)| Shred::new_from_serialized_shred(block?).ok())
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.filter(|shred| {
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let index = shred.index() as usize;
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shred.slot() == slot && data_shred_indices.contains(&index)
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shred.slot() == slot
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&& shred.is_data()
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&& match shred.erasure_block_index() {
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Some(index) => index < num_data_shreds,
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None => false,
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}
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})
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.collect();
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Ok(recovered_data)
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