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littlefs/lfs_util.h
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Christopher Haster 9b2f3cd5bb Rerouted all btree mutation through attr-list parser 
The idea here: Instead of having unique functionality for each
individual btree operation (push/set/pop/split), we treat btrees sort of
like rbyds, with a single commit entry point that operates on attr-lists.

This adds code cost, due to needing to parse the attr-list for properties
that can affect inlined btrees (tag changes mostly), but, in theory, comes
with some advantages:

1. A single btree commit entry point with all of the inlined/uninlining
   logic should offer better chances for code deduplication, vs
   spreading this logic out in each btree operation.

2. Higher-levels should know what the current weight of the branch is,
   so we may be able to avoid the implicit math needed to calculate
   deltas.

3. Higher-levels have more knowledge about the state of the btree in
   general, so there may be other shortcuts. The mtree, for example,
   only operates on weight=1 entries, which greatly simplifies a lot of
   the related math.

Note that btrees still have strict limits in what's possible in an
attr-list. Btree operations can't cross leaf-rbyd boundaries for
example.

---

A notable omission in this change is the loss of reinlining btrees.

This wase dropped for a couple reasons. It may be worth adding back at a
later time, maybe after we actually have files implemented, but for now
does not seem worth it:

1. Reinlining adds code cost. Reinlining is more complex than you might
   expect because we only reinline on compaction. And because we compact
   before playing out our attr-list, we need to know if a commit makes
   the btree inlinable before committing to the btree.

   This is still doable with our attr-lists. We already derive the
   change in tags, since we need this to know when to uninline. But it
   adds a kind of complex bailing out of btree commits.

2. The benefits of reinlining may not be that great. In most systems, a
   tree that is uninlined once is likely to be uninlined again. It's
   only if there is a bigger state change in a system that it makes
   sense to reinline.

   Though, to be fair, waiting for compaction to reinline handled this
   quite well. Only reinlining when all erased storage is used up...

3. Thanks to our roots did entry, our mtree can never reinline.

   It would be nice to change this, but this would require explicit
   handling in lfsr_mdir_commit. Future work?

4. Files are another can of worms, with more complex interactions with
   inlinability thanks to (at least on paper right now) always having
   inlined data even when uninlined.

   If reinlining is valuable for files this can change during that work.

5. Even if files never support reinlinability, truncating files (via
   either lfsr_file_truncate or LFSR_O_TRUNC) should give the file a
   blank slate, effectively reinlining the file in that case.

---

The current implementation also changes the attr-list to be mutable so
we can adjust attr-list based on the current btree node. This is a
temporary hack! We should add the appropriate functionality to our rbyd
utilities to revert this eventually.
2023-08-19 11:41:36 -05:00

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/*
* lfs utility functions
*
* Copyright (c) 2022, The littlefs authors.
* Copyright (c) 2017, Arm Limited. All rights reserved.
* SPDX-License-Identifier: BSD-3-Clause
*/
#ifndef LFS_UTIL_H
#define LFS_UTIL_H
// Users can override lfs_util.h with their own configuration by defining
// LFS_CONFIG as a header file to include (-DLFS_CONFIG=lfs_config.h).
//
// If LFS_CONFIG is used, none of the default utils will be emitted and must be
// provided by the config file. To start, I would suggest copying lfs_util.h
// and modifying as needed.
#ifdef LFS_CONFIG
#define LFS_STRINGIZE(x) LFS_STRINGIZE2(x)
#define LFS_STRINGIZE2(x) #x
#include LFS_STRINGIZE(LFS_CONFIG)
#else
// System includes
#include <stdint.h>
#include <stdbool.h>
#include <sys/types.h>
#include <string.h>
#include <inttypes.h>
#ifndef LFS_NO_MALLOC
#include <stdlib.h>
#endif
#ifndef LFS_NO_ASSERT
#include <assert.h>
#endif
#if !defined(LFS_NO_DEBUG) || \
!defined(LFS_NO_WARN) || \
!defined(LFS_NO_ERROR) || \
defined(LFS_YES_TRACE)
#include <stdio.h>
#endif
#ifdef __cplusplus
extern "C"
{
#endif
// Macros, may be replaced by system specific wrappers. Arguments to these
// macros must not have side-effects as the macros can be removed for a smaller
// code footprint
// Logging functions
#ifndef LFS_TRACE
#ifdef LFS_YES_TRACE
#define LFS_TRACE_(fmt, ...) \
printf("%s:%d:trace: " fmt "%s\n", __FILE__, __LINE__, __VA_ARGS__)
#define LFS_TRACE(...) LFS_TRACE_(__VA_ARGS__, "")
#else
#define LFS_TRACE(...)
#endif
#endif
#ifndef LFS_DEBUG
#ifndef LFS_NO_DEBUG
#define LFS_DEBUG_(fmt, ...) \
printf("%s:%d:debug: " fmt "%s\n", __FILE__, __LINE__, __VA_ARGS__)
#define LFS_DEBUG(...) LFS_DEBUG_(__VA_ARGS__, "")
#else
#define LFS_DEBUG(...)
#endif
#endif
#ifndef LFS_WARN
#ifndef LFS_NO_WARN
#define LFS_WARN_(fmt, ...) \
printf("%s:%d:warn: " fmt "%s\n", __FILE__, __LINE__, __VA_ARGS__)
#define LFS_WARN(...) LFS_WARN_(__VA_ARGS__, "")
#else
#define LFS_WARN(...)
#endif
#endif
#ifndef LFS_ERROR
#ifndef LFS_NO_ERROR
#define LFS_ERROR_(fmt, ...) \
printf("%s:%d:error: " fmt "%s\n", __FILE__, __LINE__, __VA_ARGS__)
#define LFS_ERROR(...) LFS_ERROR_(__VA_ARGS__, "")
#else
#define LFS_ERROR(...)
#endif
#endif
// Runtime assertions
#ifndef LFS_ASSERT
#ifndef LFS_NO_ASSERT
#define LFS_ASSERT(test) assert(test)
#else
#define LFS_ASSERT(test)
#endif
#endif
#ifndef LFS_UNREACHABLE
#ifndef LFS_NO_ASSERT
#define LFS_UNREACHABLE() __builtin_unreachable()
#else
#define LFS_UNREACHABLE() LFS_ASSERT(false)
#endif
#endif
// We need to know the endianness of the system for some struct packing
#if (defined(BYTE_ORDER) \
&& defined(ORDER_LITTLE_ENDIAN) \
&& BYTE_ORDER == ORDER_LITTLE_ENDIAN) \
|| (defined(__BYTE_ORDER) \
&& defined(__ORDER_LITTLE_ENDIAN) \
&& __BYTE_ORDER == __ORDER_LITTLE_ENDIAN) \
|| (defined(__BYTE_ORDER__) \
&& defined(__ORDER_LITTLE_ENDIAN__) \
&& __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
#define LFS_LITTLE_ENDIAN
#elif (defined(BYTE_ORDER) \
&& defined(ORDER_BIG_ENDIAN) \
&& BYTE_ORDER == ORDER_BIG_ENDIAN) \
|| (defined(__BYTE_ORDER) \
&& defined(__ORDER_BIG_ENDIAN) \
&& __BYTE_ORDER == __ORDER_BIG_ENDIAN) \
|| (defined(__BYTE_ORDER__) \
&& defined(__ORDER_BIG_ENDIAN__) \
&& __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
#define LFS_BIG_ENDIAN
#else
#error "lfs: Unknown endianness?"
#endif
// Builtin functions, these may be replaced by more efficient
// toolchain-specific implementations. LFS_NO_INTRINSICS falls back to a more
// expensive basic C implementation for debugging purposes
// Min/max functions for unsigned 32-bit numbers
static inline uint32_t lfs_max(uint32_t a, uint32_t b) {
return (a > b) ? a : b;
}
static inline uint32_t lfs_min(uint32_t a, uint32_t b) {
return (a < b) ? a : b;
}
static inline uint32_t lfs_max32(uint32_t a, uint32_t b) {
return (a > b) ? a : b;
}
static inline uint32_t lfs_min32(uint32_t a, uint32_t b) {
return (a < b) ? a : b;
}
static inline int32_t lfs_smax32(int32_t a, int32_t b) {
return (a > b) ? a : b;
}
static inline int32_t lfs_smin32(int32_t a, int32_t b) {
return (a < b) ? a : b;
}
// TODO other 16-bit ops?
static inline uint16_t lfs_max16(uint16_t a, uint16_t b) {
return (a > b) ? a : b;
}
static inline uint16_t lfs_min16(uint16_t a, uint16_t b) {
return (a < b) ? a : b;
}
// Clamp is useful as the logic for min/max when clamping can become confusing
static inline uint32_t lfs_clamp32(uint32_t a, uint32_t min, uint32_t max) {
return lfs_min32(lfs_max32(a, min), max);
}
static inline int32_t lfs_sclamp32(int32_t a, int32_t min, int32_t max) {
return lfs_smin32(lfs_smax32(a, min), max);
}
// Absolute value of signed numbers
static inline int32_t lfs_abs32(int32_t a) {
return a < 0 ? -a : a;
}
// TODO how many of these do we actually need
// Swap two 16-bit numbers
static inline void lfs_swap16(uint16_t *a, uint16_t *b) {
uint16_t t = *a;
*a = *b;
*b = t;
}
static inline void lfs_sswap16(int16_t *a, int16_t *b) {
int16_t t = *a;
*a = *b;
*b = t;
}
// Swap two 32-bit numbers
static inline void lfs_swap32(uint32_t *a, uint32_t *b) {
uint32_t t = *a;
*a = *b;
*b = t;
}
static inline void lfs_sswap32(int32_t *a, int32_t *b) {
int32_t t = *a;
*a = *b;
*b = t;
}
// Align to nearest multiple of a size
static inline uint32_t lfs_aligndown(uint32_t a, uint32_t alignment) {
return a - (a % alignment);
}
static inline uint32_t lfs_alignup(uint32_t a, uint32_t alignment) {
return lfs_aligndown(a + alignment-1, alignment);
}
// Find the smallest power of 2 greater than or equal to a
static inline uint32_t lfs_npw2(uint32_t a) {
// __builtin_clz of zero is undefined, so treat both 0 and 1 specially
if (a <= 1) {
return a;
}
#if !defined(LFS_NO_INTRINSICS) && (defined(__GNUC__) || defined(__CC_ARM))
return 32 - __builtin_clz(a-1);
#else
uint32_t r = 0;
uint32_t s;
a -= 1;
s = (a > 0xffff) << 4; a >>= s; r |= s;
s = (a > 0xff ) << 3; a >>= s; r |= s;
s = (a > 0xf ) << 2; a >>= s; r |= s;
s = (a > 0x3 ) << 1; a >>= s; r |= s;
return (r | (a >> 1)) + 1;
#endif
}
// TODO we should eventually adopt this as the new name for npw2
// Find the ceiling of log base 2 of the given number
static inline uint32_t lfs_nlog2(uint32_t a) {
return lfs_npw2(a);
}
// Count the number of trailing binary zeros in a
// lfs_ctz(0) may be undefined
static inline uint32_t lfs_ctz(uint32_t a) {
#if !defined(LFS_NO_INTRINSICS) && defined(__GNUC__)
return __builtin_ctz(a);
#else
return lfs_npw2((a & -a) + 1) - 1;
#endif
}
// Count the number of binary ones in a
static inline uint32_t lfs_popc(uint32_t a) {
#if !defined(LFS_NO_INTRINSICS) && (defined(__GNUC__) || defined(__CC_ARM))
return __builtin_popcount(a);
#else
a = a - ((a >> 1) & 0x55555555);
a = (a & 0x33333333) + ((a >> 2) & 0x33333333);
return (((a + (a >> 4)) & 0xf0f0f0f) * 0x1010101) >> 24;
#endif
}
// Find the sequence comparison of a and b, this is the distance
// between a and b ignoring overflow
static inline int lfs_scmp(uint32_t a, uint32_t b) {
return (int)(unsigned)(a - b);
}
// Convert between 32-bit little-endian and native order
static inline uint32_t lfs_fromle32(uint32_t a) {
#if !defined(LFS_NO_INTRINSICS) && defined(LFS_LITTLE_ENDIAN)
return a;
#elif !defined(LFS_NO_INTRINSICS)
return __builtin_bswap32(a);
#else
return (((uint8_t*)&a)[0] << 0) |
(((uint8_t*)&a)[1] << 8) |
(((uint8_t*)&a)[2] << 16) |
(((uint8_t*)&a)[3] << 24);
#endif
}
static inline uint32_t lfs_tole32(uint32_t a) {
return lfs_fromle32(a);
}
// Convert between 32-bit big-endian and native order
static inline uint32_t lfs_frombe32(uint32_t a) {
#if !defined(LFS_NO_INTRINSICS) && defined(LFS_LITTLE_ENDIAN)
return __builtin_bswap32(a);
#elif !defined(LFS_NO_INTRINSICS)
return a;
#else
return (((uint8_t*)&a)[0] << 24) |
(((uint8_t*)&a)[1] << 16) |
(((uint8_t*)&a)[2] << 8) |
(((uint8_t*)&a)[3] << 0);
#endif
}
static inline uint32_t lfs_tobe32(uint32_t a) {
return lfs_frombe32(a);
}
// Convert to/from 16-bit little-endian
static inline void lfs_tole16_(uint16_t word, void *buffer) {
((uint8_t*)buffer)[0] = word >> 0;
((uint8_t*)buffer)[1] = word >> 8;
}
static inline uint16_t lfs_fromle16_(const void *buffer) {
return (((uint8_t*)buffer)[0] << 0)
| (((uint8_t*)buffer)[1] << 8);
}
// Convert to/from 32-bit little-endian
static inline void lfs_tole32_(uint32_t word, void *buffer) {
((uint8_t*)buffer)[0] = word >> 0;
((uint8_t*)buffer)[1] = word >> 8;
((uint8_t*)buffer)[2] = word >> 16;
((uint8_t*)buffer)[3] = word >> 24;
}
static inline uint32_t lfs_fromle32_(const void *buffer) {
return (((uint8_t*)buffer)[0] << 0)
| (((uint8_t*)buffer)[1] << 8)
| (((uint8_t*)buffer)[2] << 16)
| (((uint8_t*)buffer)[3] << 24);
}
// Convert to/from leb128 encoding
// TODO should we really be using ssize_t here and not lfs_ssize_t?
ssize_t lfs_toleb128(int32_t word, void *buffer, size_t size);
ssize_t lfs_fromleb128(int32_t *word, const void *buffer, size_t size);
static inline size_t lfs_sizeleb128(int32_t word) {
// this is the size of the leb128 after encoding
return (lfs_nlog2(word+1)+7-1) / 7;
}
// Calculate CRC-32 with polynomial = 0x04c11db7
uint32_t lfs_crc(uint32_t crc, const void *buffer, size_t size);
// Calculate crc32c incrementally
//
// polynomial = 0x11edc6f41
// init = 0xffffffff
// fini = 0xffffffff
//
uint32_t lfs_crc32c(uint32_t crc, const void *buffer, size_t size);
// Allocate memory, only used if buffers are not provided to littlefs
// Note, memory must be 64-bit aligned
static inline void *lfs_malloc(size_t size) {
#ifndef LFS_NO_MALLOC
return malloc(size);
#else
(void)size;
return NULL;
#endif
}
// Deallocate memory, only used if buffers are not provided to littlefs
static inline void lfs_free(void *p) {
#ifndef LFS_NO_MALLOC
free(p);
#else
(void)p;
#endif
}
#ifdef __cplusplus
} /* extern "C" */
#endif
#endif
#endif
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