reverse-ramdisk.c: major rewrite, add POSIX code

c-programming/reverse-ramdisk.c

@@ -5,11 +5,12 @@ C programming idea: Handling temporary files like memory allocations (allocating
 
 Warning: The current result is quick and dirty. Not for educational or
 production purposes.
+Warning: The functions are not thread-safe.
 
 GCC/Clang/TCC: Compile with -DTEST to set macro TEST as defined, with -DDEBUG
 to enable debug mode
 
-To-Do: error handling on line 184, function fread()
+To-Do: Add thread-safe versions of functions (use postfix `_r`)
 */
 
 #include <errno.h>
@@ -40,11 +41,19 @@ To-Do: error handling on line 184, function fread()
 	exit(EXIT_FAILURE); \
 } while (0)
 
+#if IS_POSIX
+typedef struct {
+	int ID;
+	char* file_path;
+	int file;
+} TempFile;
+#else
 typedef struct {
 	int ID;
 	char* file_path;
 	FILE* file;
 } TempFile;
+#endif
 
 TempFile* temp_files = NULL;
 size_t num_temp_files = 0;
@@ -74,9 +83,13 @@ int tf_alloc(size_t n, size_t type_size) {
 		return -1;
 	}
 
-	// Open the file
+#if IS_POSIX
+	int file = open(file_path, O_RDWR | O_CREAT);
+	if (file == -1) {
+#else
 	FILE* file = fopen(file_path, "w+b");
 	if (file == NULL) {
+#endif
 		line_fail(-2);
 		return -1;
 	}
@@ -113,7 +126,11 @@ int tf_alloc(size_t n, size_t type_size) {
 int tf_free(int ID) {
 	size_t index = (size_t) ID;
 
+#if IS_POSIX
+	close(temp_files[index].file);
+#else
 	fclose(temp_files[index].file);
+#endif
 
 	// Delete the file
 	if (remove(temp_files[index].file_path) != 0) {
@@ -142,53 +159,105 @@ int tf_free(int ID) {
 int tf_write(int ID, size_t offset, void* data, size_t data_size) {
 	size_t index = (size_t) ID;
 
+#if IS_POSIX
+	// Check file handler for -1
+	int file = temp_files[index].file;
+	if (file == -1)
+#else
 	// Check file handler for NULL
 	FILE* file = temp_files[index].file;
 	if (file == NULL)
+#endif
 		return -1;
 
 	// Set the position
-	fseek(file, offset, SEEK_SET);
-
-	// Write the data to the file
-	size_t bytes_written = fwrite(data, 1, data_size, file);
-
-	if (bytes_written != data_size)
-		return -1;
-
-	if (fdatasync(file) == -1) {
+#if IS_POSIX
+	if (lseek(file, offset, SEEK_SET) == -1) {
+#else
+	if (fseek(file, offset, SEEK_SET) == -1) {
+#endif
 		line_fail(-1);
 		return -1;
 	}
 
+	// Write the data to the file
+#if IS_POSIX
+	ssize_t bytes_written = write(file, data, data_size);
+#else
+	size_t bytes_written = fwrite(data, 1, data_size, file);
+#endif
+
+	if (
+#if IS_POSIX
+		(size_t)
+#endif
+		bytes_written != data_size) {
+		errno = EIO;
+		return -1;
+	}
+
+#if IS_POSIX
+	if (fsync(file) == -1) {
+		line_fail(-1);
+		return -1;
+	}
+#else
+	fflush(file);
+#endif
+
 	return 0;
 }
 
 int tf_read(int ID, size_t offset, void* dest, size_t data_size) {
 	size_t index = (size_t) ID;
 
-	// Open the file in read mode
+#if IS_POSIX
+	int file = temp_files[index].file;
+	if (file == -1)
+#else
 	FILE* file = temp_files[index].file;
 	if (file == NULL)
+#endif
 		return -1;
 
 	// Read the data from the file
 	void* data = malloc(data_size);
 	if (data == NULL) {
+#if IS_POSIX
+		close(file);
+#else
 		fclose(file);
-		line_fail(-3);
+#endif
+		line_fail(-7);
 		return -1;
 	}
 
-	// Initialize the memory in the data buffer
 	memset(data, 0, data_size); // clear destination
-	fseek(file, offset, SEEK_SET); // set position
-	size_t bytes_read = fread(data, 1, data_size, file); // read bytes
+	// Set the position
+#if IS_POSIX
+	if (lseek(file, offset, SEEK_SET) == -1) {
+#else
+	if (fseek(file, offset, SEEK_SET) == -1) {
+#endif
+		line_fail(-1);
+		return -1;
+	}
+
+	// read bytes
+#if IS_POSIX
+	ssize_t bytes_read = read(file, data, data_size);
+#else
+	size_t bytes_read = fread(data, 1, data_size, file);
+#endif
 	memcpy(dest, data, data_size);
 
 	free(data); // Free the allocated memory
 
-	if (bytes_read != data_size) {
+	if (
+#if IS_POSIX
+		(size_t)
+#endif
+		bytes_read != data_size) {
 		errno = EIO;
 		return -1;
 	}