Made some small adjustments

src/backing.c

@@ -0,0 +1,221 @@
+#include "backing.h"
+
+#include "container.h"
+#include "disk.h"
+
+#include <md5.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+result_t check_backing_identifier(const char* backing) {
+	// Check that the identifier is not null
+	if (backing == NULL)
+		return failure("Backing identifier cannot be null.");
+
+	// Check that the identifier is the length of a md5 hash
+	size_t length = strlen(backing);
+	if (length != MD5_DIGEST_STRING_LENGTH - 1) // -1 because the string is null-terminated
+		return failure("Backing identifier must be %d characters long.", MD5_DIGEST_STRING_LENGTH - 1);
+
+	// Check that the identifier only contains allowed characters
+	for (size_t i = 0; i < length; i++) {
+		char c = backing[i];
+		if (c >= 'a' && c <= 'f')
+			continue;
+		if (c >= '0' && c <= '9')
+			continue;
+
+		return failure("Backing identifier cannot contain the character '%c' at index %d.", c, i);
+	}
+
+	return success();
+}
+
+result_t check_backing_exists(const char* backing) {
+	// Get the backing path
+	char* path;
+	result_t result = get_backing_path(&path, backing);
+	if (result != success())
+		return result;
+
+	// Check that the backing exists
+	struct stat st;
+	errno = 0;
+	if (stat(path, &st) != 0) {
+		if (errno == ENOENT)
+			result = failure("Backing '%s' does not exist.", backing);
+		else
+			result = failure("Failed to check if backing '%s' exists (%s).", backing, strerror(errno));
+
+		free(path);
+		return result;
+	}
+
+	// Check that the backing is a file
+	if (!S_ISREG(st.st_mode)) {
+		result = failure("Backing '%s' is not a regular file.", backing);
+		free(path);
+		return result;
+	}
+
+	// Free the backing path
+	free(path);
+
+	return success();
+}
+
+result_t get_backing_pool_path(char** _path) {
+	return format(_path, "/var/lib/sandbox/backings");
+}
+
+result_t get_backing_path(char** _path, const char* backing) {
+	// Check the backing identifier
+	result_t result = check_backing_identifier(backing);
+	if (result != success())
+		return result;
+
+	// Get the backing pool path
+	char* pool_path;
+	result = get_backing_pool_path(&pool_path);
+	if (result != success())
+		return result;
+
+	// Format the backing path
+	result = format(_path, "%s/%s", pool_path, backing);
+
+	free(pool_path);
+	return result;
+}
+
+result_t get_backing_default_path(char** _path) {
+	// Get the backing pool path
+	char* pool_path;
+	result_t result = get_backing_pool_path(&pool_path);
+	if (result != success())
+		return result;
+
+	// Format the backing path
+	result = format(_path, "%s/default", pool_path);
+
+	free(pool_path);
+	return result;
+}
+
+result_t remove_backing(const char* backing) {
+	// Check that the backing exists
+	result_t result = check_backing_exists(backing);
+	if (result != success())
+		return result;
+
+	// Get the backing path
+	char* path;
+	result = get_backing_path(&path, backing);
+	if (result != success())
+		return result;
+
+	// Remove the backing
+	errno = 0;
+	remove(path);
+
+	// Check for errors during the removal
+	if (errno != 0) {
+		free(path);
+		return failure("Failed to remove backing '%s' (%s).", backing, strerror(errno));
+	}
+
+	free(path);
+	return success();
+}
+
+bool backing_filter(const char* file) {
+	// Check that a backing with the same name exists
+	return check_backing_exists(file) == success();
+}
+
+result_t list_backings(char*** _backings) {
+	// Get the backing pool path
+	char* pool_path;
+	result_t result = get_backing_pool_path(&pool_path);
+	if (result != success())
+		return result;
+
+	// List the backings
+	result = list_files(_backings, pool_path, &backing_filter);
+
+	free(pool_path);
+	return result;
+}
+
+result_t get_default_backing(char** _backing) {
+	// Get the backing default path
+	char* path;
+	result_t result = get_backing_default_path(&path);
+	if (result != success())
+		return result;
+
+	char* backing;
+
+	// Read the default backing
+	result = read_file(&backing, path);
+
+	free(path);
+
+	if (result != success())
+		return failure("No default backing configured.");
+
+	// Check that the backing is valid
+	result = check_backing_identifier(backing);
+	if (result != success()) {
+		free(backing);
+		return failure("Default backing '%s' is not a valid backing identifier.", backing);
+	}
+
+	// Check that the backing exists
+	result = check_backing_exists(backing);
+	if (result != success()) {
+		free(backing);
+		return failure("Default backing '%s' does not exist.", backing);
+	}
+
+	*_backing = backing;
+	return result;
+}
+
+result_t set_default_backing(const char* backing) {
+	// Get the backing default path
+	char* path;
+	result_t result = get_backing_default_path(&path);
+	if (result != success())
+		return result;
+
+	// If the backing is null, remove the default backing file
+	if (backing == NULL) {
+		errno = 0;
+		remove(path);
+		free(path);
+
+		if (errno == ENOENT)
+			return success();
+		else if (errno != 0)
+			return failure("Failed to remove the default backing file (%s).", strerror(errno));
+
+		return success();
+	} else {
+		// Check that the backing exists
+		result = check_backing_exists(backing);
+		if (result != success()) {
+			free(path);
+			return result;
+		}
+
+		// Write the default backing
+		result = write_file(path, backing);
+
+		free(path);
+		return result;
+	}
+}