1267565Sdelphij/* 2267565Sdelphij * CDDL HEADER START 3267565Sdelphij * 4267565Sdelphij * This file and its contents are supplied under the terms of the 5267565Sdelphij * Common Development and Distribution License ("CDDL"), version 1.0. 6267565Sdelphij * You may only use this file in accordance with the terms of version 7267565Sdelphij * 1.0 of the CDDL. 8267565Sdelphij * 9267565Sdelphij * A full copy of the text of the CDDL should have accompanied this 10267565Sdelphij * source. A copy of the CDDL is also available via the Internet at 11267565Sdelphij * http://www.illumos.org/license/CDDL. 12267565Sdelphij * 13267565Sdelphij * CDDL HEADER END 14267565Sdelphij */ 15267565Sdelphij 16267565Sdelphij/* 17267565Sdelphij * Copyright (c) 2013 by Delphix. All rights reserved. 18267565Sdelphij */ 19267565Sdelphij 20267565Sdelphij/* 21267565Sdelphij * Embedded-data Block Pointers 22267565Sdelphij * 23267565Sdelphij * Normally, block pointers point (via their DVAs) to a block which holds data. 24267565Sdelphij * If the data that we need to store is very small, this is an inefficient 25267565Sdelphij * use of space, because a block must be at minimum 1 sector (typically 512 26267565Sdelphij * bytes or 4KB). Additionally, reading these small blocks tends to generate 27267565Sdelphij * more random reads. 28267565Sdelphij * 29267565Sdelphij * Embedded-data Block Pointers allow small pieces of data (the "payload", 30267565Sdelphij * up to 112 bytes) to be stored in the block pointer itself, instead of 31267565Sdelphij * being pointed to. The "Pointer" part of this name is a bit of a 32267565Sdelphij * misnomer, as nothing is pointed to. 33267565Sdelphij * 34267565Sdelphij * BP_EMBEDDED_TYPE_DATA block pointers allow highly-compressible data to 35267565Sdelphij * be embedded in the block pointer. The logic for this is handled in 36267565Sdelphij * the SPA, by the zio pipeline. Therefore most code outside the zio 37267565Sdelphij * pipeline doesn't need special-cases to handle these block pointers. 38267565Sdelphij * 39267565Sdelphij * See spa.h for details on the exact layout of embedded block pointers. 40267565Sdelphij */ 41267565Sdelphij 42267565Sdelphij/* 43267565Sdelphij * buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be 44267565Sdelphij * more than BPE_PAYLOAD_SIZE bytes). 45267565Sdelphij */ 46267565Sdelphijvoid 47267565Sdelphijdecode_embedded_bp_compressed(const blkptr_t *bp, void *buf) 48267565Sdelphij{ 49267565Sdelphij int psize; 50267565Sdelphij uint8_t *buf8 = buf; 51267565Sdelphij uint64_t w = 0; 52267565Sdelphij const uint64_t *bp64 = (const uint64_t *)bp; 53267565Sdelphij 54267565Sdelphij ASSERT(BP_IS_EMBEDDED(bp)); 55267565Sdelphij 56267565Sdelphij psize = BPE_GET_PSIZE(bp); 57267565Sdelphij 58267565Sdelphij /* 59267565Sdelphij * Decode the words of the block pointer into the byte array. 60267565Sdelphij * Low bits of first word are the first byte (little endian). 61267565Sdelphij */ 62267565Sdelphij for (int i = 0; i < psize; i++) { 63267565Sdelphij if (i % sizeof (w) == 0) { 64267565Sdelphij /* beginning of a word */ 65267565Sdelphij ASSERT3P(bp64, <, bp + 1); 66267565Sdelphij w = *bp64; 67267565Sdelphij bp64++; 68267565Sdelphij if (!BPE_IS_PAYLOADWORD(bp, bp64)) 69267565Sdelphij bp64++; 70267565Sdelphij } 71267565Sdelphij buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY); 72267565Sdelphij } 73267565Sdelphij} 74