Started reimplementing some functions for the backing system

src/backing.c

@@ -0,0 +1,74 @@
+#include "backing.h"
+
+#include <string.h>
+#include <sys/stat.h>
+
+bool is_valid_backing_name(const char* name) {
+	if (name == NULL)
+		return false;
+
+	size_t len = strlen(name);
+	if (len == 0)
+		return false;
+
+	for (size_t i = 0; i < len; i++)
+		if (name[i] == '/')
+			return false;
+
+	if (name[0] < '0' || name[0] > '9')
+		return false;
+
+	return true;
+}
+
+char* get_backing_path(const char* name) {
+	if (name == NULL)
+		return NULL;
+
+	return format("%s/%s", "/var/lib/sandbox/backings", name);
+}
+
+bool backing_exists(const char* name) {
+	if (name == NULL)
+		return false;
+
+	char* path = get_backing_path(name);
+	if (path == NULL)
+		return false;
+
+	// Check if the backing exists
+	struct stat st;
+	if (stat(path, &st) != 0) {
+		free(path);
+		return false;
+	}
+
+	// Free the path, as it is no longer needed
+	free(path);
+
+	if (!S_ISREG(st.st_mode))
+		return false;
+
+	return true;
+}
+
+time_t get_backing_ctime(const char* name) {
+	// As the name starts with the ctime, we can just convert the first part of the name to a time_t
+	size_t len = strlen(name);
+	size_t ctime_len = 0;
+	for (size_t i = 0; i < len; i++) {
+		if (name[i] < '0' || name[i] > '9')
+			break;
+
+		ctime_len++;
+	}
+
+	char* ctime_str = strndup(name, ctime_len);
+	if (ctime_str == NULL)
+		return 0;
+
+	time_t ctime = (time_t)strtoull(ctime_str, NULL, 10);
+	free(ctime_str);
+
+	return ctime;
+}

src/backing.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include "sandbox.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <time.h>
+
+/// @brief Returns whether the given name is a valid backing name. Backing names are valid if they start with a number (used as the ctime).
+/// @param name The name to check.
+/// @return Whether the name is valid or not.
+bool is_valid_backing_name(const char* name);
+
+/// @brief Returns the backing path for the given name.
+/// @param name The name of the backing. Note: This function does not check if the name is valid.
+/// @return The backing path.
+char* get_backing_path(const char* name);
+
+/// @brief Returns the backing path for the given name.
+/// @param name The name of the backing. Note: This function does not check if the name is valid.
+/// @return The backing path.
+bool backing_exists(const char* name);
+
+/// @brief Returns an array of all the backing names, terminated by a NULL pointer.
+/// @return An array of all the backing names. Note: The array must be freed by the caller, including every string in the array.
+char** list_backings(void);
+
+/// @brief Returns the ctime of the backing with the given name.
+/// @param name The name of the backing.
+/// @return The ctime of the backing.
+time_t get_backing_ctime(const char* name);
+
+/// @brief Returns the latest backing's name.
+/// @return The latest backing's name.
+char* get_latest_backing(void);
+
+/// @brief Creates a new backing with the given name from the given source disk.
+/// @param name The name of the new backing.
+/// @param source_disk The source disk to create the backing from. Note: If the source disk has a backing file, it must be a existing sandbox backing disk.
+/// @return Whether the backing was created successfully or not.
+bool create_backing(const char* name, const char* source_disk);

src/sandbox.c

@@ -9,9 +9,5 @@
 #include <stdlib.h>
 
 int main(int argc, char* argv[]) {
-	create_empty_disk("test.qcow2", 1024 * 1024 * 1024);
-	create_backed_disk("test2.qcow2", "test.qcow2");
-	rebase_disk("test2.qcow2", "test.qcow2");
-
 	return 0;
 }