/* * lfs util functions * * Copyright (c) 2022, The littlefs authors. * Copyright (c) 2017, Arm Limited. All rights reserved. * SPDX-License-Identifier: BSD-3-Clause */ #include "lfs_util.h" // Only compile if user does not provide custom config #ifndef LFS_CONFIG // Need lfs.h for error codes // TODO should we actually move the error codes to lfs_util.h? #include "lfs.h" // Convert to/from leb128 encoding ssize_t lfs_toleb128(uint32_t word, void *buffer, size_t size) { uint8_t *data = buffer; for (size_t i = 0; i < size; i++) { uint8_t dat = word & 0x7f; word >>= 7; if (word != 0) { data[i] = dat | 0x80; } else { data[i] = dat | 0x00; return i+1; } } // buffer overflow? LFS_UNREACHABLE(); } ssize_t lfs_fromleb128(uint32_t *word, const void *buffer, size_t size) { const uint8_t *data = buffer; int32_t word_ = 0; for (size_t i = 0; i < size; i++) { int32_t dat = data[i]; word_ |= (dat & 0x7f) << 7*i; if (!(dat & 0x80)) { // did we overflow? if ((word_ >> 7*i) != dat) { return LFS_ERR_CORRUPT; } *word = word_; return i+1; } } // truncated? return LFS_ERR_CORRUPT; } //// Software CRC implementation with small lookup table //uint32_t lfs_crc(uint32_t crc, const void *buffer, size_t size) { // static const uint32_t rtable[16] = { // 0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac, // 0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c, // 0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c, // 0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c, // }; // // const uint8_t *data = buffer; // // for (size_t i = 0; i < size; i++) { // crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 0)) & 0xf]; // crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 4)) & 0xf]; // } // // return crc; //} // crc32c tables (see lfs_crc32c for more info) #if !defined(LFS_FASTER_CRC32C) static const uint32_t lfs_crc32c_table[16] = { 0x00000000, 0x105ec76f, 0x20bd8ede, 0x30e349b1, 0x417b1dbc, 0x5125dad3, 0x61c69362, 0x7198540d, 0x82f63b78, 0x92a8fc17, 0xa24bb5a6, 0xb21572c9, 0xc38d26c4, 0xd3d3e1ab, 0xe330a81a, 0xf36e6f75, }; #else static const uint32_t lfs_crc32c_table[256] = { 0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb, 0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b, 0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24, 0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b, 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384, 0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b, 0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a, 0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35, 0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5, 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa, 0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a, 0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a, 0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595, 0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957, 0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198, 0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927, 0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38, 0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7, 0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789, 0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859, 0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46, 0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6, 0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829, 0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c, 0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93, 0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c, 0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc, 0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c, 0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033, 0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d, 0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982, 0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d, 0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed, 0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f, 0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff, 0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0, 0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540, 0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f, 0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee, 0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1, 0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e, 0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e, 0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e, 0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351, }; #endif // Calculate crc32c incrementally uint32_t lfs_crc32c(uint32_t crc, const void *buffer, size_t size) { // init with 0xffffffff so prefixed zeros affect the crc const uint8_t *data = buffer; crc ^= 0xffffffff; // A couple crc32c implementations to choose from. // // The default, "small-table" implementation offers a decent performance // without much additional code-size, reasonable for microcontrollers. For // anything larger where you really don't care about an extra 1KiB of code // the "big-table" implementation is probably better. // // Some quick measurements with GCC 11 using -Os -mcpu=cortex-m55, with // instruction counts from QEMU and an input size of 4KiB. Note these are // not cycle-accurate: // // code stack ins ld/st branch // naive 48 12 221192 4099 36865 // small-table 124 12 49160 12291 4097 // big-table 1064 8 32776 8195 4097 // #if defined(LFS_SMALLER_CRC32C) for (size_t i = 0; i < size; i++) { crc = crc ^ data[i]; for (size_t j = 0; j < 8; j++) { crc = (crc >> 1) ^ ((crc & 1) ? 0x82f63b78 : 0); } } #elif !defined(LFS_FASTER_CRC32C) for (size_t i = 0; i < size; i++) { crc = (crc >> 4) ^ lfs_crc32c_table[0xf & (crc ^ (data[i] >> 0))]; crc = (crc >> 4) ^ lfs_crc32c_table[0xf & (crc ^ (data[i] >> 4))]; } #else for (size_t i = 0; i < size; i++) { crc = (crc >> 8) ^ lfs_crc32c_table[0xff & (crc ^ data[i])]; } #endif // fini with 0xffffffff to cancel out init when called incrementally crc ^= 0xffffffff; return crc; } // Multiply two crc32cs in the crc32c ring uint32_t lfs_crc32c_mul(uint32_t a, uint32_t b) { // Multiplication in a crc32c ring involves polynomial // multiplication modulo the crc32c polynomial to keep things // finite: // // r = a * b mod P // // Note because our crc32c is not irreducible, this does not give // us a finite-field, i.e. division is undefined. Still, // multiplication has useful properties. // This gets a bit funky because crc32cs are little-endian, but // fortunately pmul is symmetric. Unfortunately the result is // 31-bits large, so we need to shift by 1. uint64_t r = lfs_pmul(a, b) << 1; // We can accelerate our module with crc32c tables if present, these // loops may look familiar. #if defined(LFS_SMALLER_CRC32C) for (int i = 0; i < 32; i++) { r = (r >> 1) ^ ((r & 1) ? 0x82f63b78 : 0); } #elif !defined(LFS_FASTER_CRC32C) for (int i = 0; i < 8; i++) { r = (r >> 4) ^ lfs_crc32c_table[0xf & r]; } #else for (int i = 0; i < 4; i++) { r = (r >> 8) ^ lfs_crc32c_table[0xff & r]; } #endif return (uint32_t)r; } #endif