Added conversion to/from little-endian on disk

Required to support big-endian processors, with the most notable being
the PowerPC architecture.

On little-endian architectures, these conversions can be optimized out
and have no code impact.

Initial patch provided by gmouchard

lfs.c

@@ -323,6 +323,48 @@ static void lfs_alloc_ack(lfs_t *lfs) {
 }
 
 
+/// Endian swapping functions ///
+static void lfs_dir_fromle32(struct lfs_disk_dir *d) {
+    d->rev     = lfs_fromle32(d->rev);
+    d->size    = lfs_fromle32(d->size);
+    d->tail[0] = lfs_fromle32(d->tail[0]);
+    d->tail[1] = lfs_fromle32(d->tail[1]);
+}
+
+static void lfs_dir_tole32(struct lfs_disk_dir *d) {
+    d->rev     = lfs_tole32(d->rev);
+    d->size    = lfs_tole32(d->size);
+    d->tail[0] = lfs_tole32(d->tail[0]);
+    d->tail[1] = lfs_tole32(d->tail[1]);
+}
+
+static void lfs_entry_fromle32(struct lfs_disk_entry *d) {
+    d->u.dir[0] = lfs_fromle32(d->u.dir[0]);
+    d->u.dir[1] = lfs_fromle32(d->u.dir[1]);
+}
+
+static void lfs_entry_tole32(struct lfs_disk_entry *d) {
+    d->u.dir[0] = lfs_tole32(d->u.dir[0]);
+    d->u.dir[1] = lfs_tole32(d->u.dir[1]);
+}
+
+static void lfs_superblock_fromle32(struct lfs_disk_superblock *d) {
+    d->root[0]     = lfs_fromle32(d->root[0]);
+    d->root[1]     = lfs_fromle32(d->root[1]);
+    d->block_size  = lfs_fromle32(d->block_size);
+    d->block_count = lfs_fromle32(d->block_count);
+    d->version     = lfs_fromle32(d->version);
+}
+
+static void lfs_superblock_tole32(struct lfs_disk_superblock *d) {
+    d->root[0]     = lfs_tole32(d->root[0]);
+    d->root[1]     = lfs_tole32(d->root[1]);
+    d->block_size  = lfs_tole32(d->block_size);
+    d->block_count = lfs_tole32(d->block_count);
+    d->version     = lfs_tole32(d->version);
+}
+
+
 /// Metadata pair and directory operations ///
 static inline void lfs_pairswap(lfs_block_t pair[2]) {
     lfs_block_t t = pair[0];
@@ -364,6 +406,7 @@ static int lfs_dir_alloc(lfs_t *lfs, lfs_dir_t *dir) {
     // rather than clobbering one of the blocks we just pretend
     // the revision may be valid
     int err = lfs_bd_read(lfs, dir->pair[0], 0, &dir->d.rev, 4);
+    dir->d.rev = lfs_fromle32(dir->d.rev);
     if (err) {
         return err;
     }
@@ -389,6 +432,7 @@ static int lfs_dir_fetch(lfs_t *lfs,
     for (int i = 0; i < 2; i++) {
         struct lfs_disk_dir test;
         int err = lfs_bd_read(lfs, tpair[i], 0, &test, sizeof(test));
+        lfs_dir_fromle32(&test);
         if (err) {
             return err;
         }
@@ -403,7 +447,9 @@ static int lfs_dir_fetch(lfs_t *lfs,
         }
 
         uint32_t crc = 0xffffffff;
+        lfs_dir_tole32(&test);
         lfs_crc(&crc, &test, sizeof(test));
+        lfs_dir_fromle32(&test);
         err = lfs_bd_crc(lfs, tpair[i], sizeof(test),
                 (0x7fffffff & test.size) - sizeof(test), &crc);
         if (err) {
@@ -463,8 +509,10 @@ static int lfs_dir_commit(lfs_t *lfs, lfs_dir_t *dir,
             }
 
             uint32_t crc = 0xffffffff;
+            lfs_dir_tole32(&dir->d);
             lfs_crc(&crc, &dir->d, sizeof(dir->d));
             err = lfs_bd_prog(lfs, dir->pair[0], 0, &dir->d, sizeof(dir->d));
+            lfs_dir_fromle32(&dir->d);
             if (err) {
                 if (err == LFS_ERR_CORRUPT) {
                     goto relocate;
@@ -511,7 +559,9 @@ static int lfs_dir_commit(lfs_t *lfs, lfs_dir_t *dir,
                 }
             }
 
+            crc = lfs_tole32(crc);
             err = lfs_bd_prog(lfs, dir->pair[0], newoff, &crc, 4);
+            crc = lfs_fromle32(crc);
             if (err) {
                 if (err == LFS_ERR_CORRUPT) {
                     goto relocate;
@@ -584,11 +634,14 @@ relocate:
 }
 
 static int lfs_dir_update(lfs_t *lfs, lfs_dir_t *dir,
-        const lfs_entry_t *entry, const void *data) {
+        lfs_entry_t *entry, const void *data) {
-    return lfs_dir_commit(lfs, dir, (struct lfs_region[]){
+    lfs_entry_tole32(&entry->d);
+    int err = lfs_dir_commit(lfs, dir, (struct lfs_region[]){
             {entry->off, sizeof(entry->d), &entry->d, sizeof(entry->d)},
             {entry->off+sizeof(entry->d), entry->d.nlen, data, entry->d.nlen}
         }, data ? 2 : 1);
+    lfs_entry_fromle32(&entry->d);
+    return err;
 }
 
 static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
@@ -597,10 +650,14 @@ static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
     while (true) {
         if (dir->d.size + lfs_entry_size(entry) <= lfs->cfg->block_size) {
             entry->off = dir->d.size - 4;
-            return lfs_dir_commit(lfs, dir, (struct lfs_region[]){
+
+            lfs_entry_tole32(&entry->d);
+            int err = lfs_dir_commit(lfs, dir, (struct lfs_region[]){
                     {entry->off, 0, &entry->d, sizeof(entry->d)},
                     {entry->off, 0, data, entry->d.nlen}
                 }, 2);
+            lfs_entry_fromle32(&entry->d);
+            return err;
         }
 
         // we need to allocate a new dir block
@@ -614,10 +671,12 @@ static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
             newdir.d.tail[0] = dir->d.tail[0];
             newdir.d.tail[1] = dir->d.tail[1];
             entry->off = newdir.d.size - 4;
+            lfs_entry_tole32(&entry->d);
             err = lfs_dir_commit(lfs, &newdir, (struct lfs_region[]){
                     {entry->off, 0, &entry->d, sizeof(entry->d)},
                     {entry->off, 0, data, entry->d.nlen}
                 }, 2);
+            lfs_entry_fromle32(&entry->d);
             if (err) {
                 return err;
             }
@@ -703,6 +762,7 @@ static int lfs_dir_next(lfs_t *lfs, lfs_dir_t *dir, lfs_entry_t *entry) {
 
     int err = lfs_bd_read(lfs, dir->pair[0], dir->off,
             &entry->d, sizeof(entry->d));
+    lfs_entry_fromle32(&entry->d);
     if (err) {
         return err;
     }
@@ -1065,6 +1125,7 @@ static int lfs_ctz_find(lfs_t *lfs,
                 lfs_ctz(current));
 
         int err = lfs_cache_read(lfs, rcache, pcache, head, 4*skip, &head, 4);
+        head = lfs_fromle32(head);
         if (err) {
             return err;
         }
@@ -1140,8 +1201,10 @@ static int lfs_ctz_extend(lfs_t *lfs,
             lfs_size_t skips = lfs_ctz(index) + 1;
 
             for (lfs_off_t i = 0; i < skips; i++) {
+                head = lfs_tole32(head);
                 err = lfs_cache_prog(lfs, pcache, rcache,
                         nblock, 4*i, &head, 4);
+                head = lfs_fromle32(head);
                 if (err) {
                     if (err == LFS_ERR_CORRUPT) {
                         goto relocate;
@@ -1152,6 +1215,7 @@ static int lfs_ctz_extend(lfs_t *lfs,
                 if (i != skips-1) {
                     err = lfs_cache_read(lfs, rcache, NULL,
                             head, 4*i, &head, 4);
+                    head = lfs_fromle32(head);
                     if (err) {
                         return err;
                     }
@@ -1196,6 +1260,8 @@ static int lfs_ctz_traverse(lfs_t *lfs,
         lfs_block_t heads[2];
         int count = 2 - (index & 1);
         err = lfs_cache_read(lfs, rcache, pcache, head, 0, &heads, count*4);
+        heads[0] = lfs_fromle32(heads[0]);
+        heads[1] = lfs_fromle32(heads[1]);
         if (err) {
             return err;
         }
@@ -1456,6 +1522,7 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
         lfs_entry_t entry = {.off = file->poff};
         err = lfs_bd_read(lfs, cwd.pair[0], entry.off,
                 &entry.d, sizeof(entry.d));
+        lfs_entry_fromle32(&entry.d);
         if (err) {
             return err;
         }
@@ -2075,6 +2142,7 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
     superdir.d.size = sizeof(superdir.d) + sizeof(superblock.d) + 4;
 
     // write both pairs to be safe
+    lfs_superblock_tole32(&superblock.d);
     bool valid = false;
     for (int i = 0; i < 2; i++) {
         err = lfs_dir_commit(lfs, &superdir, (struct lfs_region[]){
@@ -2125,6 +2193,7 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
     if (!err) {
         err = lfs_bd_read(lfs, dir.pair[0], sizeof(dir.d),
                 &superblock.d, sizeof(superblock.d));
+        lfs_superblock_fromle32(&superblock.d);
         if (err) {
             return err;
         }
@@ -2182,6 +2251,7 @@ int lfs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data) {
         while (dir.off + sizeof(entry.d) <= (0x7fffffff & dir.d.size)-4) {
             err = lfs_bd_read(lfs, dir.pair[0], dir.off,
                     &entry.d, sizeof(entry.d));
+            lfs_entry_fromle32(&entry.d);
             if (err) {
                 return err;
             }

lfs_util.h

@@ -70,6 +70,29 @@ static inline int lfs_scmp(uint32_t a, uint32_t b) {
     return (int)(unsigned)(a - b);
 }
 
+static inline uint32_t lfs_fromle32(uint32_t a) {
+#if ( \
+    (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 ( \
+    (defined(  BYTE_ORDER  ) &&   BYTE_ORDER   ==   ORDER_BIG_ENDIAN  ) || \
+    (defined(__BYTE_ORDER  ) && __BYTE_ORDER   == __ORDER_BIG_ENDIAN  ) || \
+    (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__))
+    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);
+}
+
 // CRC-32 with polynomial = 0x04c11db7
 void lfs_crc(uint32_t *crc, const void *buffer, size_t size);