Added more configurable utils

Note: It's still expected to modify lfs_utils.h when porting littlefs
to a new target/system. There's just too much room for system-specific
improvements, such as taking advantage of CRC hardware.

Rather, encouraging modification of lfs_util.h and making it easy to
modify and debug should result in better integration with the consuming
systems.

This just adds a bunch of quality-of-life improvements that should help
development and integration in littlefs.

- Macros that require no side-effects are all-caps
- System includes are only brought in when needed
- Malloc/free wrappers
- LFS_NO_* checks for quickly disabling things at the command line
- At least a little-bit more docs

lfs.c

@@ -18,17 +18,13 @@
 #include "lfs.h"
 #include "lfs_util.h"
 
-#include <string.h>
-#include <stdlib.h>
-#include <assert.h>
-
 
 /// Caching block device operations ///
 static int lfs_cache_read(lfs_t *lfs, lfs_cache_t *rcache,
         const lfs_cache_t *pcache, lfs_block_t block,
         lfs_off_t off, void *buffer, lfs_size_t size) {
     uint8_t *data = buffer;
-    assert(block < lfs->cfg->block_count);
+    LFS_ASSERT(block < lfs->cfg->block_count);
 
     while (size > 0) {
         if (pcache && block == pcache->block && off >= pcache->off &&
@@ -153,7 +149,7 @@ static int lfs_cache_prog(lfs_t *lfs, lfs_cache_t *pcache,
         lfs_cache_t *rcache, lfs_block_t block,
         lfs_off_t off, const void *buffer, lfs_size_t size) {
     const uint8_t *data = buffer;
-    assert(block < lfs->cfg->block_count);
+    LFS_ASSERT(block < lfs->cfg->block_count);
 
     while (size > 0) {
         if (block == pcache->block && off >= pcache->off &&
@@ -180,7 +176,7 @@ static int lfs_cache_prog(lfs_t *lfs, lfs_cache_t *pcache,
 
         // pcache must have been flushed, either by programming and
         // entire block or manually flushing the pcache
-        assert(pcache->block == 0xffffffff);
+        LFS_ASSERT(pcache->block == 0xffffffff);
 
         if (off % lfs->cfg->prog_size == 0 &&
                 size >= lfs->cfg->prog_size) {
@@ -1130,7 +1126,7 @@ static int lfs_ctz_find(lfs_t *lfs,
             return err;
         }
 
-        assert(head >= 2 && head <= lfs->cfg->block_count);
+        LFS_ASSERT(head >= 2 && head <= lfs->cfg->block_count);
         current -= 1 << skip;
     }
 
@@ -1150,7 +1146,7 @@ static int lfs_ctz_extend(lfs_t *lfs,
         if (err) {
             return err;
         }
-        assert(nblock >= 2 && nblock <= lfs->cfg->block_count);
+        LFS_ASSERT(nblock >= 2 && nblock <= lfs->cfg->block_count);
 
         if (true) {
             err = lfs_bd_erase(lfs, nblock);
@@ -1221,7 +1217,7 @@ static int lfs_ctz_extend(lfs_t *lfs,
                     }
                 }
 
-                assert(head >= 2 && head <= lfs->cfg->block_count);
+                LFS_ASSERT(head >= 2 && head <= lfs->cfg->block_count);
             }
 
             *block = nblock;
@@ -1347,12 +1343,12 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
     if (lfs->cfg->file_buffer) {
         file->cache.buffer = lfs->cfg->file_buffer;
     } else if ((file->flags & 3) == LFS_O_RDONLY) {
-        file->cache.buffer = malloc(lfs->cfg->read_size);
+        file->cache.buffer = lfs_malloc(lfs->cfg->read_size);
         if (!file->cache.buffer) {
             return LFS_ERR_NOMEM;
         }
     } else {
-        file->cache.buffer = malloc(lfs->cfg->prog_size);
+        file->cache.buffer = lfs_malloc(lfs->cfg->prog_size);
         if (!file->cache.buffer) {
             return LFS_ERR_NOMEM;
         }
@@ -1378,7 +1374,7 @@ int lfs_file_close(lfs_t *lfs, lfs_file_t *file) {
 
     // clean up memory
     if (!lfs->cfg->file_buffer) {
-        free(file->cache.buffer);
+        lfs_free(file->cache.buffer);
     }
 
     return err;
@@ -1527,7 +1523,7 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
             return err;
         }
 
-        assert(entry.d.type == LFS_TYPE_REG);
+        LFS_ASSERT(entry.d.type == LFS_TYPE_REG);
         entry.d.u.file.head = file->head;
         entry.d.u.file.size = file->size;
 
@@ -1753,7 +1749,7 @@ int lfs_file_truncate(lfs_t *lfs, lfs_file_t *file, lfs_off_t size) {
 
         // flush+seek if not already at end
         if (file->pos != oldsize) {
-            int err = lfs_file_seek(lfs, file, 0, SEEK_END);
+            int err = lfs_file_seek(lfs, file, 0, LFS_SEEK_END);
             if (err < 0) {
                 return err;
             }
@@ -1886,7 +1882,7 @@ int lfs_remove(lfs_t *lfs, const char *path) {
             return res;
         }
 
-        assert(res); // must have pred
+        LFS_ASSERT(res); // must have pred
         cwd.d.tail[0] = dir.d.tail[0];
         cwd.d.tail[1] = dir.d.tail[1];
 
@@ -2003,7 +1999,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
             return res;
         }
 
-        assert(res); // must have pred
+        LFS_ASSERT(res); // must have pred
         newcwd.d.tail[0] = dir.d.tail[0];
         newcwd.d.tail[1] = dir.d.tail[1];
 
@@ -2026,7 +2022,7 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
     if (lfs->cfg->read_buffer) {
         lfs->rcache.buffer = lfs->cfg->read_buffer;
     } else {
-        lfs->rcache.buffer = malloc(lfs->cfg->read_size);
+        lfs->rcache.buffer = lfs_malloc(lfs->cfg->read_size);
         if (!lfs->rcache.buffer) {
             return LFS_ERR_NOMEM;
         }
@@ -2037,30 +2033,30 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
     if (lfs->cfg->prog_buffer) {
         lfs->pcache.buffer = lfs->cfg->prog_buffer;
     } else {
-        lfs->pcache.buffer = malloc(lfs->cfg->prog_size);
+        lfs->pcache.buffer = lfs_malloc(lfs->cfg->prog_size);
         if (!lfs->pcache.buffer) {
             return LFS_ERR_NOMEM;
         }
     }
 
     // setup lookahead, round down to nearest 32-bits
-    assert(lfs->cfg->lookahead % 32 == 0);
-    assert(lfs->cfg->lookahead > 0);
+    LFS_ASSERT(lfs->cfg->lookahead % 32 == 0);
+    LFS_ASSERT(lfs->cfg->lookahead > 0);
     if (lfs->cfg->lookahead_buffer) {
         lfs->free.buffer = lfs->cfg->lookahead_buffer;
     } else {
-        lfs->free.buffer = malloc(lfs->cfg->lookahead/8);
+        lfs->free.buffer = lfs_malloc(lfs->cfg->lookahead/8);
         if (!lfs->free.buffer) {
             return LFS_ERR_NOMEM;
         }
     }
 
     // check that program and read sizes are multiples of the block size
-    assert(lfs->cfg->prog_size % lfs->cfg->read_size == 0);
-    assert(lfs->cfg->block_size % lfs->cfg->prog_size == 0);
+    LFS_ASSERT(lfs->cfg->prog_size % lfs->cfg->read_size == 0);
+    LFS_ASSERT(lfs->cfg->block_size % lfs->cfg->prog_size == 0);
 
     // check that the block size is large enough to fit ctz pointers
-    assert(4*lfs_npw2(0xffffffff / (lfs->cfg->block_size-2*4))
+    LFS_ASSERT(4*lfs_npw2(0xffffffff / (lfs->cfg->block_size-2*4))
             <= lfs->cfg->block_size);
 
     // setup default state
@@ -2076,15 +2072,15 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
 static int lfs_deinit(lfs_t *lfs) {
     // free allocated memory
     if (!lfs->cfg->read_buffer) {
-        free(lfs->rcache.buffer);
+        lfs_free(lfs->rcache.buffer);
     }
 
     if (!lfs->cfg->prog_buffer) {
-        free(lfs->pcache.buffer);
+        lfs_free(lfs->pcache.buffer);
     }
 
     if (!lfs->cfg->lookahead_buffer) {
-        free(lfs->free.buffer);
+        lfs_free(lfs->free.buffer);
     }
 
     return 0;

lfs.h

@@ -27,7 +27,7 @@
 // Software library version
 // Major (top-nibble), incremented on backwards incompatible changes
 // Minor (bottom-nibble), incremented on feature additions
-#define LFS_VERSION 0x00010002
+#define LFS_VERSION 0x00010003
 #define LFS_VERSION_MAJOR (0xffff & (LFS_VERSION >> 16))
 #define LFS_VERSION_MINOR (0xffff & (LFS_VERSION >>  0))
 

lfs_util.h

@@ -18,13 +18,60 @@
 #ifndef LFS_UTIL_H
 #define LFS_UTIL_H
 
-#include <stdlib.h>
 #include <stdint.h>
+#include <stdbool.h>
+#include <string.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)
 #include <stdio.h>
+#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_NO_DEBUG
+#define LFS_DEBUG(fmt, ...) \
+    printf("lfs debug:%d: " fmt "\n", __LINE__, __VA_ARGS__)
+#else
+#define LFS_DEBUG(fmt, ...)
+#endif
+
+#ifndef LFS_NO_WARN
+#define LFS_WARN(fmt, ...) \
+    printf("lfs warn:%d: " fmt "\n", __LINE__, __VA_ARGS__)
+#else
+#define LFS_WARN(fmt, ...)
+#endif
+
+#ifndef LFS_NO_ERROR
+#define LFS_ERROR(fmt, ...) \
+    printf("lfs error:%d: " fmt "\n", __LINE__, __VA_ARGS__)
+#else
+#define LFS_ERROR(fmt, ...)
+#endif
+
+// Runtime assertions
+#ifndef LFS_NO_ASSERT
+#define LFS_ASSERT(test) assert(test)
+#else
+#define LFS_ASSERT(test)
+#endif
 
 
-// Builtin functions, these may be replaced by more
-// efficient implementations in the system
+// 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;
 }
@@ -33,8 +80,9 @@ static inline uint32_t lfs_min(uint32_t a, uint32_t b) {
     return (a < b) ? a : b;
 }
 
+// Find the next smallest power of 2 less than or equal to a
 static inline uint32_t lfs_npw2(uint32_t a) {
-#if defined(__GNUC__) || defined(__CC_ARM)
+#if !defined(LFS_NO_INTRINSICS) && (defined(__GNUC__) || defined(__CC_ARM))
     return 32 - __builtin_clz(a-1);
 #else
     uint32_t r = 0;
@@ -48,16 +96,19 @@ static inline uint32_t lfs_npw2(uint32_t a) {
 #endif
 }
 
+// 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(__GNUC__)
+#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(__GNUC__) || defined(__CC_ARM)
+#if !defined(LFS_NO_INTRINSICS) && (defined(__GNUC__) || defined(__CC_ARM))
     return __builtin_popcount(a);
 #else
     a = a - ((a >> 1) & 0x55555555);
@@ -66,17 +117,20 @@ static inline uint32_t lfs_popc(uint32_t a) {
 #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 from 32-bit little-endian to native order
 static inline uint32_t lfs_fromle32(uint32_t a) {
-#if ( \
+#if !defined(LFS_NO_INTRINSICS) && ( \
     (defined(  BYTE_ORDER  ) &&   BYTE_ORDER   ==   ORDER_LITTLE_ENDIAN  ) || \
     (defined(__BYTE_ORDER  ) && __BYTE_ORDER   == __ORDER_LITTLE_ENDIAN  ) || \
     (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__))
     return a;
-#elif ( \
+#elif !defined(LFS_NO_INTRINSICS) && ( \
     (defined(  BYTE_ORDER  ) &&   BYTE_ORDER   ==   ORDER_BIG_ENDIAN  ) || \
     (defined(__BYTE_ORDER  ) && __BYTE_ORDER   == __ORDER_BIG_ENDIAN  ) || \
     (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__))
@@ -89,19 +143,29 @@ static inline uint32_t lfs_fromle32(uint32_t a) {
 #endif
 }
 
+// Convert to 32-bit little-endian from native order
 static inline uint32_t lfs_tole32(uint32_t a) {
     return lfs_fromle32(a);
 }
 
-// CRC-32 with polynomial = 0x04c11db7
+// Calculate CRC-32 with polynomial = 0x04c11db7
 void lfs_crc(uint32_t *crc, const void *buffer, size_t size);
 
+// Allocate memory, only used if buffers are not provided to littlefs
+static inline void *lfs_malloc(size_t size) {
+#ifndef LFS_NO_MALLOC
+    return malloc(size);
+#else
+    return NULL;
+#endif
+}
 
-// Logging functions, these may be replaced by system-specific
-// logging functions
-#define LFS_DEBUG(fmt, ...) printf("lfs debug: " fmt "\n", __VA_ARGS__)
-#define LFS_WARN(fmt, ...)  printf("lfs warn: " fmt "\n", __VA_ARGS__)
-#define LFS_ERROR(fmt, ...) printf("lfs error: " fmt "\n", __VA_ARGS__)
+// Deallocate memory, only used if buffers are not provided to littlefs
+static inline void lfs_free(void *p) {
+#ifndef LFS_NO_MALLOC
+    free(p);
+#endif
+}
 
 
 #endif