Initial commit of block device interface and emulated block device

emubd/lfs_emubd.c

@@ -0,0 +1,223 @@
+/*
+ * Block device emulated on standard files
+ *
+ * Copyright (c) 2017 Christopher Haster
+ * Distributed under the MIT license
+ */
+#include "emubd/lfs_emubd.h"
+#include "emubd/lfs_cfg.h"
+
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <limits.h>
+#include <dirent.h>
+
+
+// Block device emulated on existing filesystem
+lfs_error_t lfs_emubd_create(lfs_emubd_t *emu, const char *path) {
+    memset(&emu->info, 0, sizeof(emu->info));
+
+    // Allocate buffer for creating children files
+    size_t pathlen = strlen(path);
+    emu->path = malloc(pathlen + 1 + LFS_NAME_MAX + 1);
+    if (!emu->path) {
+        return -ENOMEM;
+    }
+
+    strcpy(emu->path, path);
+    emu->path[pathlen] = '/';
+    emu->path[pathlen + 1 + LFS_NAME_MAX] = '\0';
+    emu->child = &emu->path[pathlen+1];
+    strncpy(emu->child, "config", LFS_NAME_MAX);
+
+    // Load config, erroring if it doesn't exist
+    lfs_cfg_t cfg;
+    int err = lfs_cfg_create(&cfg, emu->path);
+    if (err) {
+        return err;
+    }
+
+    emu->info.read_size = lfs_cfg_getu(&cfg,  "read_size",  0);
+    emu->info.write_size = lfs_cfg_getu(&cfg, "write_size", 0);
+    emu->info.erase_size = lfs_cfg_getu(&cfg, "erase_size", 0);
+    emu->info.total_size = lfs_cfg_getu(&cfg, "total_size", 0);
+
+    lfs_cfg_destroy(&cfg);
+
+    return 0;
+}
+
+void lfs_emubd_destroy(lfs_emubd_t *emu) {
+    free(emu->path);
+}
+
+lfs_error_t lfs_emubd_read(lfs_emubd_t *emu, uint8_t *buffer,
+        lfs_ino_t ino, lfs_off_t off, lfs_size_t size) {
+
+    // Check if read is valid
+    if (!(off % emu->info.read_size == 0 &&
+         size % emu->info.read_size == 0 &&
+         ((lfs_lsize_t)ino*emu->info.erase_size + off + size
+          < emu->info.total_size))) {
+        return -EINVAL;
+    }
+
+    // Default to some arbitrary value for debugging
+    memset(buffer, 0xcc, size);
+
+    // Iterate over blocks until enough data is read
+    while (size > 0) {
+        snprintf(emu->child, LFS_NAME_MAX, "%d", ino);
+        size_t count = lfs_min(emu->info.erase_size - off, size);
+
+        FILE *f = fopen(emu->path, "rb");
+        if (!f && errno != ENOENT) {
+            return -errno;
+        }
+
+        if (f) {
+            int err = fseek(f, off, SEEK_SET);
+            if (err) {
+                return -errno;
+            }
+
+            size_t res = fread(buffer, 1, count, f);
+            if (res < count && !feof(f)) {
+                return -errno;
+            }
+
+            err = fclose(f);
+            if (err) {
+                return -errno;
+            }
+        }
+
+        size -= count;
+        buffer += count;
+        ino += 1;
+        off = 0;
+    }
+
+    return 0;
+}
+
+lfs_error_t lfs_emubd_write(lfs_emubd_t *emu, const uint8_t *buffer,
+        lfs_ino_t ino, lfs_off_t off, lfs_size_t size) {
+
+    // Check if write is valid
+    if (!(off % emu->info.write_size == 0 &&
+         size % emu->info.write_size == 0 &&
+         ((lfs_lsize_t)ino*emu->info.erase_size + off + size
+          < emu->info.total_size))) {
+        return -EINVAL;
+    }
+
+    // Iterate over blocks until enough data is read
+    while (size > 0) {
+        snprintf(emu->child, LFS_NAME_MAX, "%d", ino);
+        size_t count = lfs_min(emu->info.erase_size - off, size);
+
+        FILE *f = fopen(emu->path, "r+b");
+        if (!f && errno == ENOENT) {
+            f = fopen(emu->path, "w+b");
+            if (!f) {
+                return -errno;
+            }
+        }
+
+        int err = fseek(f, off, SEEK_SET);
+        if (err) {
+            return -errno;
+        }
+
+        size_t res = fwrite(buffer, 1, count, f);
+        if (res < count) {
+            return -errno;
+        }
+
+        err = fclose(f);
+        if (err) {
+            return -errno;
+        }
+
+        size -= count;
+        buffer += count;
+        ino += 1;
+        off = 0;
+    }
+
+    return 0;
+}
+
+lfs_error_t lfs_emubd_erase(lfs_emubd_t *emu,
+        lfs_ino_t ino, lfs_off_t off, lfs_size_t size) {
+
+    // Check if erase is valid
+    if (!(off % emu->info.erase_size == 0 &&
+         size % emu->info.erase_size == 0 &&
+         ((lfs_lsize_t)ino*emu->info.erase_size + off + size
+          < emu->info.total_size))) {
+        return -EINVAL;
+    }
+
+    // Iterate and erase blocks
+    while (size > 0) {
+        snprintf(emu->child, LFS_NAME_MAX, "%d", ino);
+        int err = unlink(emu->path);
+        if (err && errno != ENOENT) {
+            return -errno;
+        }
+
+        size -= emu->info.erase_size;
+        ino += 1;
+        off = 0;
+    }
+
+    return 0;
+}
+
+lfs_error_t lfs_emubd_sync(lfs_emubd_t *emu) {
+    // Always in sync
+    return 0;
+}
+
+lfs_error_t lfs_emubd_info(lfs_emubd_t *emu, struct lfs_bd_info *info) {
+    *info = emu->info;
+    return 0;
+}
+
+
+// Wrappers for void*s
+static lfs_error_t lfs_emubd_bd_read(void *bd, uint8_t *buffer,
+        lfs_ino_t ino, lfs_off_t off, lfs_size_t size) {
+    return lfs_emubd_read((lfs_emubd_t*)bd, buffer, ino, off, size);
+}
+
+static lfs_error_t lfs_emubd_bd_write(void *bd, const uint8_t *buffer,
+        lfs_ino_t ino, lfs_off_t off, lfs_size_t size) {
+    return lfs_emubd_write((lfs_emubd_t*)bd, buffer, ino, off, size);
+}
+
+static lfs_error_t lfs_emubd_bd_erase(void *bd,
+        lfs_ino_t ino, lfs_off_t off, lfs_size_t size) {
+    return lfs_emubd_erase((lfs_emubd_t*)bd, ino, off, size);
+}
+
+static lfs_error_t lfs_emubd_bd_sync(void *bd) {
+    return lfs_emubd_sync((lfs_emubd_t*)bd);
+}
+
+static lfs_error_t lfs_emubd_bd_info(void *bd, struct lfs_bd_info *info) {
+    return lfs_emubd_info((lfs_emubd_t*)bd, info);
+}
+
+const struct lfs_bd_ops lfs_emubd_ops = {
+    .read = lfs_emubd_bd_read,
+    .write = lfs_emubd_bd_write,
+    .erase = lfs_emubd_bd_erase,
+    .sync = lfs_emubd_bd_sync,
+    .info = lfs_emubd_bd_info,
+};
+