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/*
* CDDL HEADER START
*
* This file and its contents are supplied under the terms of the
* Common Development and Distribution License ("CDDL"), version 1.0.
* You may only use this file in accordance with the terms of version
* 1.0 of the CDDL.
*
* A full copy of the text of the CDDL should have accompanied this
* source. A copy of the CDDL is also available via the Internet at
* http://www.illumos.org/license/CDDL.
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2013 by Delphix. All rights reserved.
*/
/*
* Embedded-data Block Pointers
*
* Normally, block pointers point (via their DVAs) to a block which holds data.
* If the data that we need to store is very small, this is an inefficient
* use of space, because a block must be at minimum 1 sector (typically 512
* bytes or 4KB). Additionally, reading these small blocks tends to generate
* more random reads.
*
* Embedded-data Block Pointers allow small pieces of data (the "payload",
* up to 112 bytes) to be stored in the block pointer itself, instead of
* being pointed to. The "Pointer" part of this name is a bit of a
* misnomer, as nothing is pointed to.
*
* BP_EMBEDDED_TYPE_DATA block pointers allow highly-compressible data to
* be embedded in the block pointer. The logic for this is handled in
* the SPA, by the zio pipeline. Therefore most code outside the zio
* pipeline doesn't need special-cases to handle these block pointers.
*
* See spa.h for details on the exact layout of embedded block pointers.
*/
/*
* buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be
* more than BPE_PAYLOAD_SIZE bytes).
*/
void
decode_embedded_bp_compressed(const blkptr_t *bp, void *buf)
{
int psize;
uint8_t *buf8 = buf;
uint64_t w = 0;
const uint64_t *bp64 = (const uint64_t *)bp;
ASSERT(BP_IS_EMBEDDED(bp));
psize = BPE_GET_PSIZE(bp);
/*
* Decode the words of the block pointer into the byte array.
* Low bits of first word are the first byte (little endian).
*/
for (int i = 0; i < psize; i++) {
if (i % sizeof (w) == 0) {
/* beginning of a word */
ASSERT3P(bp64, <, bp + 1);
w = *bp64;
bp64++;
if (!BPE_IS_PAYLOADWORD(bp, bp64))
bp64++;
}
buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY);
}
}
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