Refactor the command line interface

Select operation by its name instead of by number of the arguments.

11 files changed, 481 insertions, 230 deletions

diff --git a/src/Makefile b/src/Makefile
index 8b24b35..4deaaec 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS=-Wall
+CFLAGS=-Wall -fmax-errors=2
 
 SOURCES=*.c
 HEADERS=*.h
diff --git a/src/backup.c b/src/backup.c
index 4691bac..4c9dfbd 100644
--- a/src/backup.c
+++ b/src/backup.c
@@ -34,15 +34,14 @@
 #include <stdlib.h>
 #include <string.h>
 
-static int check_files(const options_t *const opts,
-                       const resources_t *const res);
-static int allocate_buffers(const options_t *const opts, size_t out_buffer_size,
-                            resources_t *const res);
+static int check_files(const options_backup_t *const opts,
+                       const resources_backup_t *const res);
 static int write_out_buffer(const char *const buffer, size_t size,
                             FILE *const file);
 
 static int
-check_files(const options_t *const opts, const resources_t *const res)
+check_files(const options_backup_t *const opts,
+            const resources_backup_t *const res)
 {
     const long in_size = file_size(res->in_file);
 
@@ -73,25 +72,6 @@ check_files(const options_t *const opts, const resources_t *const res)
 }
 
 static int
-allocate_buffers(const options_t *const opts, size_t out_buffer_size,
-                 resources_t *const res)
-{
-
-    if ((res->in_buffer = (char *)malloc(opts->buffer_size)) == NULL) {
-        print_error("cannot allocate buffer for input file data");
-        return 1;
-    } else if ((res->ref_buffer = (char *)malloc(opts->buffer_size)) == NULL) {
-        print_error("cannot allocate buffer for reference file data");
-        return 1;
-    } else if ((res->out_buffer = (char *)malloc(out_buffer_size)) == NULL) {
-        print_error("cannot allocate buffer for output file data");
-        return 1;
-    }
-
-    return 0;
-}
-
-static int
 write_out_buffer(const char *const buffer, size_t size, FILE *const file)
 {
     const size_t bytes_written = fwrite(buffer, 1U, size, file);
@@ -105,21 +85,12 @@ write_out_buffer(const char *const buffer, size_t size, FILE *const file)
 }
 
 int
-backup(const options_t *const opts, resources_t *const res)
+backup(const options_backup_t *const opts, const resources_backup_t *const res)
 {
     if (check_files(opts, res) != 0) {
         return 1;
     }
 
-    /* The output buffer contains also the offsets */
-    const size_t out_buffer_size =
-        ((opts->buffer_size / opts->sector_size) * sizeof(uint64_t)) +
-        opts->buffer_size;
-
-    if (allocate_buffers(opts, out_buffer_size, res) != 0) {
-        return 1;
-    }
-
     size_t out_buffer_index = 0;
     uint64_t input_file_offset = 0;
 
@@ -148,7 +119,7 @@ backup(const options_t *const opts, resources_t *const res)
                        res->ref_buffer + buffer_offset,
                        opts->sector_size) != 0) {
                 /* Backup the changed sector */
-                if (out_buffer_index >= out_buffer_size) {
+                if (out_buffer_index >= res->out_buffer_size) {
                     /* The output buffer is full. Write it to the output file */
                     if (write_out_buffer(res->out_buffer, out_buffer_index,
                                          res->out_file) != 0) {
diff --git a/src/backup.h b/src/backup.h
index 057aa15..9f14559 100644
--- a/src/backup.h
+++ b/src/backup.h
@@ -30,6 +30,7 @@
 #include "options.h"
 #include "resources.h"
 
-int backup(const options_t *const opts, resources_t *const res);
+int backup(const options_backup_t *const opts,
+           const resources_backup_t *const res);
 
 #endif /* BACKUP_H */
diff --git a/src/main.c b/src/main.c
index 80e6129..35e5c3d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -25,19 +25,11 @@
  */
 
 #include "backup.h"
-#include "file.h"
 #include "options.h"
-#include "print.h"
 #include "resources.h"
 #include "restore.h"
 
-#include <endian.h>
-#include <errno.h>
-#include <inttypes.h>
-#include <stdint.h>
-#include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 
 static void
 clean_exit(resources_t *const res, int exit_code)
@@ -46,67 +38,26 @@ clean_exit(resources_t *const res, int exit_code)
     exit(exit_code);
 }
 
-static int
-open_files(const options_t *const opts, resources_t *const res,
-           bool is_action_backup)
-{
-    /* Open the input file */
-    if ((opts->in_file_path != NULL) &&
-        ((res->in_file = fopen(opts->in_file_path, "r")) == NULL)) {
-        print_error("cannot open input file: %s", strerror(errno));
-        return 1;
-    }
-
-    /* Open the reference file */
-    if ((res->ref_file = fopen(opts->ref_file_path, "r")) == NULL) {
-        print_error("cannot open reference file: %s", strerror(errno));
-        return 1;
-    }
-
-    /* Open the output file
-     *
-     * When restoring, the file must be opened for writing and not
-     * truncated
-     */
-    char out_mode[] = "r+";
-
-    if (is_action_backup) {
-        /* When backing up, the output file is truncated to hold the
-         * new data
-         */
-        out_mode[0] = 'w';
-        out_mode[1] = '\0';
-    }
-
-    if ((res->out_file = fopen(opts->out_file_path, out_mode)) == NULL) {
-        print_error("cannot open output file: %s", strerror(errno));
-        return 1;
-    }
-
-    return 0;
-}
-
 int
 main(int argc, char **argv)
 {
     options_t opts;
 
-    if (options_parse(argc, argv, &opts)) {
+    if (!options_parse(argc, argv, &opts)) {
         options_usage(1);
-    } else if (opts.help) {
+    } else if (options_is_operation(&opts, OPERATION_ID_HELP)) {
         options_usage(0);
     }
 
-    const bool is_action_backup = (opts.in_file_path != NULL);
     resources_t res;
 
-    resources_init(&res);
-
-    if (open_files(&opts, &res, is_action_backup) != 0) {
+    if (resources_allocate(&opts, &res)) {
         clean_exit(&res, 1);
-    } else if (is_action_backup) {
-        clean_exit(&res, backup(&opts, &res));
+    } else if (options_is_operation(&opts, OPERATION_ID_BACKUP)) {
+        clean_exit(&res, backup(options_get_for_backup(&opts),
+                                resources_get_for_backup(&res)));
     } else {
-        clean_exit(&res, restore(&opts, &res));
+        clean_exit(&res, restore(options_get_for_restore(&opts),
+                                 resources_get_for_restore(&res)));
     }
 }
diff --git a/src/operation_id.h b/src/operation_id.h
new file mode 100644
index 0000000..99536af
--- /dev/null
+++ b/src/operation_id.h
@@ -0,0 +1,37 @@
+/* Copyright 2019 Ján Sučan <jan@jansucan.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef OPERATION_ID_H
+#define OPERATION_ID_H
+
+typedef enum {
+    OPERATION_ID_UNKNOWN,
+    OPERATION_ID_HELP,
+    OPERATION_ID_BACKUP,
+    OPERATION_ID_RESTORE,
+} operation_id_t;
+
+#endif /* OPERATION_ID_H */
diff --git a/src/options.c b/src/options.c
index 002b36c..e2fcfdb 100644
--- a/src/options.c
+++ b/src/options.c
@@ -38,22 +38,126 @@
  */
 #include "program_info.h"
 
+#define OPTIONS_MAX_OPERATION_NAME_LENGTH 8
 #define OPTIONS_DEFAULT_SECTOR_SIZE 512
 #define OPTIONS_DEFAULT_BUFFER_SIZE (4 * 1024 * 1024)
 
-static void options_init(options_t *const opts);
+struct common_options {
+    bool help;
+    uint32_t sector_size;
+    uint32_t buffer_size;
+};
+
 static int options_parse_unsigned(const char *const arg, uint32_t *const value);
+static void options_parse_operation(const char *const argv,
+                                    options_t *const opts);
+static bool options_parse_common(int *const argc, char ***const argv,
+                                 struct common_options *const opts);
+static bool options_parse_backup(int *const argc, char ***const argv,
+                                 options_t *const opts);
+static bool options_parse_restore(int *const argc, char ***const argv,
+                                  options_t *const opts);
 
-int
+bool
 options_parse(int argc, char **argv, options_t *const opts)
 {
-    options_init(opts);
+    // Skip the executable name
+    --argc;
+    ++argv;
+
+    options_parse_operation(argv[0], opts);
+
+    if (options_is_operation(opts, OPERATION_ID_UNKNOWN)) {
+        return false;
+    }
+
+    if (options_is_operation(opts, OPERATION_ID_BACKUP)) {
+        if (!options_parse_backup(&argc, &argv, opts)) {
+            return false;
+        }
+    } else if (options_is_operation(opts, OPERATION_ID_RESTORE)) {
+        if (!options_parse_restore(&argc, &argv, opts)) {
+            return false;
+        }
+    }
+    return true;
+}
+
+void
+options_usage(int exit_code)
+{
+    printf("Usage: %s [-s SECTOR_SIZE] [-b BUFFER_SIZE] [INFILE] REFFILE "
+           "OUTFILE\n",
+           PROGRAM_NAME_STR);
+    exit(exit_code);
+}
+
+bool
+options_is_operation(const options_t *const opts, operation_id_t operation_id)
+{
+    return (opts->operation_id == operation_id);
+}
+
+const options_backup_t *
+options_get_for_backup(const options_t *const opts)
+{
+    return &(opts->op.backup);
+}
+
+const options_restore_t *
+options_get_for_restore(const options_t *const opts)
+{
+    return &(opts->op.restore);
+}
+
+static int
+options_parse_unsigned(const char *const arg, uint32_t *const value)
+{
+    char *end;
+
+    errno = 0;
+
+    *value = strtoul(arg, &end, 0);
+
+    return ((*end != '\0') || (errno != 0)) ? -1 : 0;
+}
+
+static void
+options_parse_operation(const char *const op_name, options_t *const opts)
+{
+    if (op_name == NULL) {
+        opts->operation_id = OPERATION_ID_UNKNOWN;
+    } else if (strncmp(op_name, "help", OPTIONS_MAX_OPERATION_NAME_LENGTH) ==
+               0) {
+        opts->operation_id = OPERATION_ID_HELP;
+    } else if (strncmp(op_name, "backup", OPTIONS_MAX_OPERATION_NAME_LENGTH) ==
+               0) {
+        opts->operation_id = OPERATION_ID_BACKUP;
+    } else if (strncmp(op_name, "restore", OPTIONS_MAX_OPERATION_NAME_LENGTH) ==
+               0) {
+        opts->operation_id = OPERATION_ID_RESTORE;
+    } else {
+        opts->operation_id = OPERATION_ID_UNKNOWN;
+    }
+}
+
+static void
+options_init_common(struct common_options *const opts)
+{
+    opts->help = false;
+    opts->sector_size = OPTIONS_DEFAULT_SECTOR_SIZE;
+    opts->buffer_size = OPTIONS_DEFAULT_BUFFER_SIZE;
+}
 
+static bool
+options_parse_common(int *const argc, char ***const argv,
+                     struct common_options *const opts)
+{
     int ch;
     char *arg_sector_size = NULL;
     char *arg_buffer_size = NULL;
 
-    while ((ch = getopt(argc, argv, ":b:hs:")) != -1) {
+    while ((ch = getopt(*argc, *argv, ":b:hs:")) != -1) {
         switch (ch) {
         case 'b':
             arg_buffer_size = optarg;
@@ -69,90 +173,94 @@ options_parse(int argc, char **argv, options_t *const opts)
 
         case ':':
             print_error("missing argument for option '-%c'", optopt);
-            return 1;
-
+            return false;
         default:
             print_error("unknown option '-%c'", optopt);
-            return 1;
+            return false;
         }
     }
 
-    argc -= optind;
-    argv += optind;
-
-    if (opts->help) {
-        return 0;
-    } else if (argc < 2) {
-        print_error("missing arguments");
-        return 1;
-    } else if (argc > 3) {
-        print_error("too many arguments");
-        return 1;
-    }
+    *argc -= optind;
+    *argv += optind;
 
     /* Convert numbers in the arguments */
     if ((arg_sector_size != NULL) &&
         options_parse_unsigned(arg_sector_size, &(opts->sector_size))) {
         print_error("incorrect sector size");
-        return 1;
+        return false;
     } else if ((arg_buffer_size != NULL) &&
                options_parse_unsigned(arg_buffer_size, &(opts->buffer_size))) {
         print_error("incorrect buffer size");
-        return 1;
+        return false;
     } else if (opts->sector_size == 0) {
         print_error("sector size cannot be 0");
-        return 1;
+        return false;
     } else if (opts->buffer_size == 0) {
         print_error("buffer size cannot be 0");
-        return 1;
+        return false;
     } else if (opts->sector_size > opts->buffer_size) {
         print_error("sector size cannot larger than buffer size");
-        return 1;
+        return false;
     } else if ((opts->buffer_size % opts->sector_size) != 0) {
         print_error("buffer size is not multiple of sector size");
-        return 1;
+        return false;
     }
 
-    /* Pick the file paths */
-    int last_path_index = argc - 1;
-    opts->out_file_path = argv[last_path_index--];
-    opts->ref_file_path = argv[last_path_index--];
-    if (last_path_index >= 0) {
-        opts->in_file_path = argv[last_path_index];
-    }
-
-    return 0;
+    return true;
 }
 
-void
-options_usage(int exit_code)
+static bool
+options_parse_backup(int *const argc, char ***const argv, options_t *const opts)
 {
-    printf("Usage: %s [-s SECTOR_SIZE] [-b BUFFER_SIZE] [INFILE] REFFILE "
-           "OUTFILE\n",
-           PROGRAM_NAME_STR);
-    exit(exit_code);
-}
+    struct common_options common_opts;
+    options_init_common(&common_opts);
+    if (!options_parse_common(argc, argv, &common_opts)) {
+        return false;
+    }
 
-static void
-options_init(options_t *const opts)
-{
-    opts->help = false;
-    opts->sector_size = OPTIONS_DEFAULT_SECTOR_SIZE;
-    opts->buffer_size = OPTIONS_DEFAULT_BUFFER_SIZE;
+    if (common_opts.help) {
+        opts->operation_id = OPERATION_ID_HELP;
+    } else if (*argc < 3) {
+        print_error("missing arguments");
+        return false;
+    } else if (*argc > 3) {
+        print_error("too many arguments");
+        return false;
+    } else {
+        opts->op.backup.sector_size = common_opts.sector_size;
+        opts->op.backup.buffer_size = common_opts.buffer_size;
+        opts->op.backup.in_file_path = (*argv)[0];
+        opts->op.backup.ref_file_path = (*argv)[1];
+        opts->op.backup.out_file_path = (*argv)[2];
+    }
 
-    opts->in_file_path = NULL;
-    opts->ref_file_path = NULL;
-    opts->out_file_path = NULL;
+    return true;
 }
 
-static int
-options_parse_unsigned(const char *const arg, uint32_t *const value)
+static bool
+options_parse_restore(int *const argc, char ***const argv,
+                      options_t *const opts)
 {
-    char *end;
-
-    errno = 0;
+    struct common_options common_opts;
+    options_init_common(&common_opts);
+    if (!options_parse_common(argc, argv, &common_opts)) {
+        return false;
+    }
 
-    *value = strtoul(arg, &end, 0);
+    if (common_opts.help) {
+        opts->operation_id = OPERATION_ID_HELP;
+    } else if (*argc < 2) {
+        print_error("missing arguments");
+        return false;
+    } else if (*argc > 2) {
+        print_error("too many arguments");
+        return false;
+    } else {
+        opts->op.restore.sector_size = common_opts.sector_size;
+        opts->op.restore.buffer_size = common_opts.buffer_size;
+        opts->op.restore.in_file_path = (*argv)[0];
+        opts->op.restore.out_file_path = (*argv)[1];
+    }
 
-    return ((*end != '\0') || (errno != 0)) ? -1 : 0;
+    return true;
 }
diff --git a/src/options.h b/src/options.h
index 9ffa14f..e162fbe 100644
--- a/src/options.h
+++ b/src/options.h
@@ -27,20 +27,40 @@
 #ifndef OPTIONS_H
 #define OPTIONS_H
 
+#include "operation_id.h"
+
 #include <stdbool.h>
 #include <stdint.h>
 
 typedef struct {
-    bool help;
     uint32_t sector_size;
     uint32_t buffer_size;
-
     const char *in_file_path;
     const char *ref_file_path;
     const char *out_file_path;
+} options_backup_t;
+
+typedef struct {
+    uint32_t sector_size;
+    uint32_t buffer_size;
+    const char *in_file_path;
+    const char *out_file_path;
+} options_restore_t;
+
+typedef struct {
+    operation_id_t operation_id;
+
+    union {
+        options_backup_t backup;
+        options_restore_t restore;
+    } op;
 } options_t;
 
-int options_parse(int argc, char **argv, options_t *const opts);
+bool options_parse(int argc, char **argv, options_t *const opts);
 void options_usage(int exit_code);
+bool options_is_operation(const options_t *const opts,
+                          operation_id_t operation_id);
+const options_backup_t *options_get_for_backup(const options_t *const opts);
+const options_restore_t *options_get_for_restore(const options_t *const opts);
 
 #endif /* OPTIONS_H */
diff --git a/src/resources.c b/src/resources.c
index 65b7f71..0829c7c 100644
--- a/src/resources.c
+++ b/src/resources.c
@@ -26,45 +26,188 @@
 
 #include "resources.h"
 
+#include "print.h"
+
+#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
-void
-resources_init(resources_t *const res)
+static void
+resources_init_for_backup(resources_backup_t *const res)
 {
     res->in_file = NULL;
     res->ref_file = NULL;
     res->out_file = NULL;
+
     res->in_buffer = NULL;
     res->ref_buffer = NULL;
     res->out_buffer = NULL;
 }
 
-void
-resources_free(resources_t *const res)
+static int
+resources_allocate_for_backup(const options_backup_t *const opts,
+                              resources_backup_t *const res)
 {
-    if (res->in_file != NULL) {
-        fclose(res->in_file);
-        res->in_file = NULL;
+    if ((res->in_file = fopen(opts->in_file_path, "r")) == NULL) {
+        print_error("cannot open input file: %s", strerror(errno));
+        return 1;
     }
-    if (res->ref_file != NULL) {
-        fclose(res->ref_file);
-        res->ref_file = NULL;
+
+    if ((res->ref_file = fopen(opts->ref_file_path, "r")) == NULL) {
+        print_error("cannot open reference file: %s", strerror(errno));
+        return 1;
     }
-    if (res->out_file != NULL) {
-        fclose(res->out_file);
-        res->out_file = NULL;
+
+    /* When backing up, the output file is truncated to hold the
+     * new data
+     */
+    if ((res->out_file = fopen(opts->out_file_path, "w+")) == NULL) {
+        print_error("cannot open output file: %s", strerror(errno));
+        return 1;
     }
-    if (res->in_buffer != NULL) {
-        free(res->in_buffer);
-        res->in_buffer = NULL;
+
+    /* The output buffer contains also the offsets */
+    res->out_buffer_size =
+        ((opts->buffer_size / opts->sector_size) * sizeof(uint64_t)) +
+        opts->buffer_size;
+
+    // TODO: separate function
+    if ((res->in_buffer = (char *)malloc(opts->buffer_size)) == NULL) {
+        print_error("cannot allocate buffer for input file data");
+        return 1;
+    } else if ((res->ref_buffer = (char *)malloc(opts->buffer_size)) == NULL) {
+        print_error("cannot allocate buffer for reference file data");
+        return 1;
+    } else if ((res->out_buffer = (char *)malloc(res->out_buffer_size)) ==
+               NULL) {
+        print_error("cannot allocate buffer for output file data");
+        return 1;
     }
-    if (res->ref_buffer != NULL) {
-        free(res->ref_buffer);
-        res->ref_buffer = NULL;
+
+    return 0;
+}
+
+static void
+resources_init_for_restore(resources_restore_t *const res)
+{
+    res->in_file = NULL;
+    res->out_file = NULL;
+
+    res->in_buffer = NULL;
+    res->out_buffer = NULL;
+}
+
+static int
+resources_allocate_for_restore(const options_restore_t *const opts,
+                               resources_restore_t *const res)
+{
+    if ((res->in_file = fopen(opts->in_file_path, "r")) == NULL) {
+        print_error("cannot open input file: %s", strerror(errno));
+        return 1;
     }
-    if (res->out_buffer != NULL) {
-        free(res->out_buffer);
-        res->out_buffer = NULL;
+
+    /* When restoring, the file must be opened for writing and not
+     * truncated
+     */
+    if ((res->out_file = fopen(opts->out_file_path, "r+")) == NULL) {
+        print_error("cannot open output file: %s", strerror(errno));
+        return 1;
     }
+
+    /* Allocate the buffer for data from the input file */
+    /* The input buffer contains also the offsets */
+    res->in_sector_size = sizeof(uint64_t) + opts->sector_size;
+    const size_t in_buffer_sector_count =
+        opts->buffer_size / res->in_sector_size;
+    res->in_buffer_size = in_buffer_sector_count * res->in_sector_size;
+
+    if ((res->in_buffer = (char *)malloc(res->in_buffer_size)) == NULL) {
+        print_error("cannot allocate buffer for input file data");
+        return 1;
+    }
+
+    return 0;
+}
+
+static void
+resources_close_file(FILE **const file)
+{
+    if (*file != NULL) {
+        fclose(*file);
+        *file = NULL;
+    }
+}
+
+static void
+resources_close_buffer(char **const buffer)
+{
+    if (*buffer != NULL) {
+        free(*buffer);
+        *buffer = NULL;
+    }
+}
+
+static void
+resources_free_backup(resources_backup_t *const res)
+{
+    resources_close_file(&(res->in_file));
+    resources_close_file(&(res->ref_file));
+    resources_close_file(&(res->out_file));
+
+    resources_close_buffer(&(res->in_buffer));
+    resources_close_buffer(&(res->ref_buffer));
+    resources_close_buffer(&(res->out_buffer));
+}
+
+static void
+resources_free_restore(resources_restore_t *const res)
+{
+    resources_close_file(&(res->in_file));
+    resources_close_file(&(res->out_file));
+
+    resources_close_buffer(&(res->in_buffer));
+    resources_close_buffer(&(res->out_buffer));
+}
+
+int
+resources_allocate(const options_t *const opts, resources_t *const res)
+{
+    res->operation_id = opts->operation_id;
+
+    if (res->operation_id == OPERATION_ID_BACKUP) {
+        resources_init_for_backup(&(res->res.backup));
+        return resources_allocate_for_backup(&(opts->op.backup),
+                                             &(res->res.backup));
+    } else if (res->operation_id == OPERATION_ID_RESTORE) {
+        resources_init_for_restore(&(res->res.restore));
+        return resources_allocate_for_restore(&(opts->op.restore),
+                                              &(res->res.restore));
+    }
+
+    return 0;
+}
+
+const resources_backup_t *
+resources_get_for_backup(const resources_t *const res)
+{
+    return &(res->res.backup);
+}
+
+const resources_restore_t *
+resources_get_for_restore(const resources_t *const res)
+{
+    return &(res->res.restore);
+}
+
+void
+resources_free(resources_t *const res)
+{
+    if (res->operation_id == OPERATION_ID_BACKUP) {
+        resources_free_backup(&(res->res.backup));
+    } else if (res->operation_id == OPERATION_ID_RESTORE) {
+        resources_free_restore(&(res->res.restore));
+    }
+
+    res->operation_id = OPERATION_ID_UNKNOWN;
 }
diff --git a/src/resources.h b/src/resources.h
index 3c6e768..3cc0dff 100644
--- a/src/resources.h
+++ b/src/resources.h
@@ -27,6 +27,9 @@
 #ifndef RESOURCES_H
 #define RESOURCES_H
 
+#include "operation_id.h"
+#include "options.h"
+
 #include <stdio.h>
 
 typedef struct {
@@ -37,9 +40,35 @@ typedef struct {
     char *in_buffer;
     char *ref_buffer;
     char *out_buffer;
+
+    size_t out_buffer_size;
+} resources_backup_t;
+
+typedef struct {
+    FILE *in_file;
+    FILE *out_file;
+
+    char *in_buffer;
+    char *out_buffer;
+
+    size_t in_sector_size;
+    size_t in_buffer_size;
+} resources_restore_t;
+
+typedef struct {
+    operation_id_t operation_id;
+
+    union {
+        resources_backup_t backup;
+        resources_restore_t restore;
+    } res;
 } resources_t;
 
-void resources_init(resources_t *const res);
+int resources_allocate(const options_t *const opts, resources_t *const res);
+const resources_backup_t *
+resources_get_for_backup(const resources_t *const res);
+const resources_restore_t *
+resources_get_for_restore(const resources_t *const res);
 void resources_free(resources_t *const res);
 
 #endif /* RESOURCES_H */
diff --git a/src/restore.c b/src/restore.c
index 6318766..df58ab8 100644
--- a/src/restore.c
+++ b/src/restore.c
@@ -37,22 +37,21 @@
 #include <string.h>
 
 static bool
-is_reference_file_valid(resources_t *const res, uint32_t sector_size)
+is_input_file_valid(const resources_restore_t *const res, uint32_t sector_size)
 {
-    const long ref_size = file_size(res->ref_file);
+    const long in_size = file_size(res->in_file);
 
-    if (ref_size < 0) {
-        print_error("cannot get size of reference file: %s", strerror(errno));
+    if (in_size < 0) {
+        print_error("cannot get size of input file: %s", strerror(errno));
         return false;
-    } else if (ref_size == 0) {
-        print_error("reference file is empty");
+    } else if (in_size == 0) {
+        print_error("input file is empty");
         return false;
-    } else if ((ref_size % (sizeof(uint64_t) + sector_size)) != 0) {
-        /* The reference file must hold equally sized sectors and the
+    } else if ((in_size % (sizeof(uint64_t) + sector_size)) != 0) {
+        /* The input file must hold equally sized sectors and the
          * offset of each of them
          */
-        print_error(
-            "reference file has size that cannot contain valid diff data");
+        print_error("input file has size that cannot contain valid diff data");
         return false;
     }
 
@@ -66,18 +65,18 @@ is_reference_file_valid(resources_t *const res, uint32_t sector_size)
     uint64_t prev_out_offset = 0;
     bool is_first_reading = true;
 
-    /* Scan the reference file and check  */
+    /* Scan the input file and check  */
     for (;;) {
         uint64_t out_offset;
         /* Read the next offset */
-        const size_t ref_read =
-            fread(&out_offset, sizeof(out_offset), 1U, res->ref_file);
+        const size_t in_read =
+            fread(&out_offset, sizeof(out_offset), 1U, res->in_file);
         out_offset = le64toh(out_offset);
 
-        if (feof(res->ref_file)) {
+        if (feof(res->in_file)) {
             break;
-        } else if ((ref_read != 1U) || ferror(res->ref_file)) {
-            print_error("cannot read from reference file: %s", strerror(errno));
+        } else if ((in_read != 1U) || ferror(res->in_file)) {
+            print_error("cannot read from input file: %s", strerror(errno));
             return false;
         } else if (!is_first_reading && (out_offset <= prev_out_offset)) {
             print_error("a sector offset points behind the previous offset");
@@ -86,8 +85,8 @@ is_reference_file_valid(resources_t *const res, uint32_t sector_size)
             print_error(
                 "a sector offset points past the end of the output file");
             return false;
-        } else if (fseek(res->ref_file, sector_size, SEEK_CUR) != 0) {
-            print_error("cannot seek in reference file: %s", strerror(errno));
+        } else if (fseek(res->in_file, sector_size, SEEK_CUR) != 0) {
+            print_error("cannot seek in input file: %s", strerror(errno));
             return false;
         }
 
@@ -95,13 +94,13 @@ is_reference_file_valid(resources_t *const res, uint32_t sector_size)
         prev_out_offset = out_offset;
     }
 
-    if (ftell(res->ref_file) != ref_size) {
-        /* The reference file must be read completely */
-        print_error("reference file is not valid");
+    if (ftell(res->in_file) != in_size) {
+        /* The input file must be read completely */
+        print_error("input file is not valid");
         return false;
-    } else if (fseek(res->ref_file, 0L, SEEK_SET) != 0) {
+    } else if (fseek(res->in_file, 0L, SEEK_SET) != 0) {
         /* The file must be prepared for the restoring */
-        print_error("cannot seek in reference file: %s", strerror(errno));
+        print_error("cannot seek in input file: %s", strerror(errno));
         return false;
     }
 
@@ -109,28 +108,18 @@ is_reference_file_valid(resources_t *const res, uint32_t sector_size)
 }
 
 int
-restore(const options_t *const opts, resources_t *const res)
+restore(const options_restore_t *const opts,
+        const resources_restore_t *const res)
 {
-    /* Check validity of the reference file */
-    if (!is_reference_file_valid(res, opts->sector_size)) {
+    /* Check validity of the input file */
+    if (!is_input_file_valid(res, opts->sector_size)) {
         return 1;
     }
 
-    const long ref_size = file_size(res->ref_file);
+    const long in_size = file_size(res->in_file);
 
-    if (ref_size < 0) {
-        print_error("cannot get size of reference file: %s", strerror(errno));
-        return 1;
-    }
-
-    /* Allocate the buffer for data from the reference file */
-    /* The reference buffer contains also the offsets */
-    const size_t ref_sector_size = sizeof(uint64_t) + opts->sector_size;
-    const size_t ref_buffer_sector_count = opts->buffer_size / ref_sector_size;
-    const size_t ref_buffer_size = ref_buffer_sector_count * ref_sector_size;
-
-    if ((res->ref_buffer = (char *)malloc(ref_buffer_size)) == NULL) {
-        print_error("cannot allocate buffer for reference file data");
+    if (in_size < 0) {
+        print_error("cannot get size of input file: %s", strerror(errno));
         return 1;
     }
 
@@ -138,18 +127,19 @@ restore(const options_t *const opts, resources_t *const res)
     for (;;) {
 
         /* Read data of the offset and the next sector */
-        const size_t ref_sectors_read = file_read_sectors(
-            res->ref_file, res->ref_buffer, ref_buffer_size, ref_sector_size);
+        const size_t in_sectors_read =
+            file_read_sectors(res->in_file, res->in_buffer, res->in_buffer_size,
+                              res->in_sector_size);
 
-        if (ref_sectors_read == 0) {
+        if (in_sectors_read == 0) {
             break;
         }
 
-        char *ref_buffer = res->ref_buffer;
+        char *in_buffer = res->in_buffer;
 
-        for (size_t s = 0; s < ref_sectors_read; ++s) {
-            const uint64_t out_offset = le64toh(*((uint64_t *)ref_buffer));
-            ref_buffer += sizeof(uint64_t);
+        for (size_t s = 0; s < in_sectors_read; ++s) {
+            const uint64_t out_offset = le64toh(*((uint64_t *)in_buffer));
+            in_buffer += sizeof(uint64_t);
 
             if (fseek(res->out_file, out_offset, SEEK_SET) != 0) {
                 print_error("cannot seek in output file: %s", strerror(errno));
@@ -157,8 +147,8 @@ restore(const options_t *const opts, resources_t *const res)
             }
 
             const size_t out_written =
-                fwrite(ref_buffer, opts->sector_size, 1U, res->out_file);
-            ref_buffer += opts->sector_size;
+                fwrite(in_buffer, opts->sector_size, 1U, res->out_file);
+            in_buffer += opts->sector_size;
 
             if (out_written != 1U) {
                 print_error("cannot write to output file: %s", strerror(errno));
@@ -167,9 +157,9 @@ restore(const options_t *const opts, resources_t *const res)
         }
     }
 
-    /* The reference file must be read completely */
-    if (ftell(res->ref_file) != ref_size) {
-        print_error("reference file is not valid");
+    /* The input file must be read completely */
+    if (ftell(res->in_file) != in_size) {
+        print_error("input file is not valid");
         return 1;
     }
 
diff --git a/src/restore.h b/src/restore.h
index 02d70ff..a6c09d1 100644
--- a/src/restore.h
+++ b/src/restore.h
@@ -30,6 +30,7 @@
 #include "options.h"
 #include "resources.h"
 
-int restore(const options_t *const opts, resources_t *const res);
+int restore(const options_restore_t *const opts,
+            const resources_restore_t *const res);
 
 #endif /* RESTORE_H */