[wip] add read and write

inc/print.h

@@ -3,6 +3,8 @@
 
 
 #include <stdio.h>
+#include <unistd.h>
+
 #include "config.h"
 #include "color.h"
 
@@ -15,8 +17,10 @@
 
 #if ENABLE_STDOUT == 1
 	#define pr_stdout(...) { printf(__VA_ARGS__); }
+	#define write_stdout(data, size) { write(1, (data), (size)); }
 #else
 	#define pr_stdout(...) {}
+	#define write_stdout(data, size) {}
 #endif
 
 

src/fs.c

@@ -587,6 +587,312 @@ int fs_open(void *d)
 	return 0;
 }
 
+int fs_seek(void *d)
+{
+	int fd = ((int *) d)[0];
+	int offset = ((int *) d)[1];
+
+	if (!fs_file_descriptions[fd].inode) {
+		pr_err("fd %d is not open\n", fd);
+		return 0;
+	}
+
+	struct fs_inode f;
+	read_block(fs_file_descriptions[fd].inode, (void *) &f);
+
+	if (offset > f.size) {
+		pr_err("offset is larger than file (%d > %d)\n", offset, f.size);
+		return 0;
+	}
+
+	pr("Moving rw_offset of fd %d: %d -> %d\n",
+			fd, fs_file_descriptions[fd].rw_offset, offset);
+	fs_file_descriptions[fd].rw_offset = offset;
+
+	return 0;
+}
+
+static void read_fd_block(unsigned int fd, unsigned int block_index, unsigned char *buf)
+{
+	struct fs_inode f;
+	read_block(fs_file_descriptions[fd].inode, (void *) &f);
+
+	if (block_index < BLOCK_ADDRESSES_PER_INODE) {
+		if (f.blocks[block_index])
+			read_block(f.blocks[block_index], (void *) buf);
+		else
+			memset(buf, 0, FS_BLOCK_SIZE);
+	} else {
+		int ext_no = (block_index - BLOCK_ADDRESSES_PER_INODE) / BLOCK_ADDRESSES_PER_INODE_EXTENSION;
+		int ext_offset = (block_index - BLOCK_ADDRESSES_PER_INODE) % BLOCK_ADDRESSES_PER_INODE_EXTENSION;
+
+		unsigned int target_extension_address;
+		unsigned int i;
+
+		// seek to target extension address
+		for (
+			target_extension_address = f.next_extension, i = 0;
+			(i < ext_no) && target_extension_address;
+			i++
+		) {
+			struct fs_inode_extension ext;
+			read_block(target_extension_address, (void *) &ext);
+			target_extension_address = ext.next_extension;
+		}
+
+		if (!target_extension_address) {
+			memset(buf, 0, FS_BLOCK_SIZE);
+		} else {
+			struct fs_inode_extension ext;
+			read_block(target_extension_address, (void *) &ext);
+
+			if (!ext.blocks[ext_offset])
+				memset(buf, 0, FS_BLOCK_SIZE);
+			else
+				read_block(ext.blocks[ext_offset], (void *) buf);
+		}
+	}
+}
+
+static int write_fd_block(unsigned int fd, unsigned int block_index, unsigned char *buf)
+{
+	struct fs_inode f;
+	read_block(fs_file_descriptions[fd].inode, (void *) &f);
+
+	if (block_index < BLOCK_ADDRESSES_PER_INODE) {
+		if (!f.blocks[block_index]) {
+			int new_block = find_free_block();
+			if (!new_block) {
+				pr_err("failed to write to fd=%d block=%d: can't allocate block for writing file data\n",
+						fd, block_index);
+				return -1;
+			}
+			mark_used(new_block);
+
+			f.blocks[block_index] = new_block;
+			write_block(fs_file_descriptions[fd].inode, (void *) &f);
+		}
+
+		write_block(f.blocks[block_index], (void *) buf);
+	} else {
+		int ext_no = (block_index - BLOCK_ADDRESSES_PER_INODE) / BLOCK_ADDRESSES_PER_INODE_EXTENSION;
+		int ext_offset = (block_index - BLOCK_ADDRESSES_PER_INODE) % BLOCK_ADDRESSES_PER_INODE_EXTENSION;
+
+		// treat switch from base inode to inode extension as special case
+		if (!f.next_extension) {
+			int new_block = find_free_block();
+			if (!new_block) {
+				pr_err("failed to write to fd=%d block=%d: can't allocate block for inode extension\n",
+						fd, block_index);
+				return -1;
+			}
+			mark_used(new_block);
+
+			struct fs_inode_extension ext;
+			memset(&ext, 0, sizeof(struct fs_inode_extension));
+
+			f.next_extension = new_block;
+			write_block(fs_file_descriptions[fd].inode, (void *) &f);
+		}
+
+		unsigned int target_extension_address;
+		unsigned int previous_extension_address = f.next_extension;
+		unsigned int i;
+
+		// seek to target extension address
+		for (
+			target_extension_address = previous_extension_address, i = 0;
+			(i < ext_no);
+			i++
+		) {
+			if (!target_extension_address) {
+				int new_block = find_free_block();
+				if (!new_block) {
+					pr_err("failed to write to fd=%d block=%d: can't allocate block for inode extension\n",
+							fd, block_index);
+					return -1;
+				}
+				mark_used(new_block);
+
+				// updating previous inode extension
+				struct fs_inode_extension prev_ext;
+				read_block(previous_extension_address, (void *) &prev_ext);  // read
+				prev_ext.next_extension = new_block;                         // modify
+				write_block(previous_extension_address, (void *) &prev_ext); // write
+
+				// writing new inode extension
+				struct fs_inode_extension ext;
+				memset(&ext, 0, sizeof(struct fs_inode_extension));
+				write_block(target_extension_address, (void *) &ext);
+			}
+
+			struct fs_inode_extension ext;
+			read_block(target_extension_address, (void *) &ext);
+			previous_extension_address = target_extension_address;
+			target_extension_address = ext.next_extension;
+		}
+
+		if (!target_extension_address) {
+			int new_block = find_free_block();
+			if (!new_block) {
+				pr_err("failed to write to fd=%d block=%d: can't allocate block for inode extension\n",
+						fd, block_index);
+				return -1;
+			}
+
+			struct fs_inode_extension prev_ext;
+			read_block(previous_extension_address, (void *) &prev_ext);  // read
+			prev_ext.next_extension = new_block;                         // modify
+			write_block(previous_extension_address, (void *) &prev_ext); // write
+
+			int new_data_block = find_free_block();
+			if (!new_data_block) {
+				pr_err("failed to write to fd=%d block=%d: can't allocate block for data\n",
+						fd, block_index);
+				return -1;
+			}
+
+			mark_used(new_block);
+			mark_used(new_data_block);
+
+			// writing new inode extension
+			struct fs_inode_extension ext;
+			memset(&ext, 0, sizeof(struct fs_inode_extension));
+			ext.blocks[ext_offset] = new_data_block;
+			write_block(target_extension_address, (void *) &ext);
+
+			// writing new data block
+			write_block(new_data_block, (void *) buf);
+		} else {
+			struct fs_inode_extension ext;
+			read_block(target_extension_address, (void *) &ext);
+
+			if (!ext.blocks[ext_offset]) {
+				int new_data_block = find_free_block();
+				if (!new_data_block) {
+					pr_err("failed to write to fd=%d block=%d: can't allocate block for data\n",
+							fd, block_index);
+					return -1;
+				}
+				mark_used(new_data_block);
+
+				ext.blocks[ext_offset] = new_data_block;
+				write_block(target_extension_address, (void *) &ext);
+			}
+
+			write_block(ext.blocks[ext_offset], (void *) buf);
+		}
+	}
+}
+
+int fs_read(void *d)
+{
+	int fd = ((int *) d)[0];
+	int amount = ((int *) d)[1];
+
+	if (!fs_file_descriptions[fd].inode) {
+		pr_err("fd %d is not open\n", fd);
+		return 0;
+	}
+
+	if (amount <= 0)
+		return 0;
+
+	struct fs_inode f;
+	read_block(fs_file_descriptions[fd].inode, (void *) &f);
+
+	if (fs_file_descriptions[fd].rw_offset + amount > f.size) {
+		pr_err("can not read outside of a file (offset %d + amount %d > f.size %d)\n",
+				fs_file_descriptions[fd].rw_offset, amount, f.size);
+		return 0;
+	}
+
+	pr("Reading %d bytes from fd %d (offset %d)\n",
+			amount, fd, fs_file_descriptions[fd].rw_offset);
+
+	unsigned char *read_data = malloc(amount);
+	unsigned int total_read_data_amount = 0;
+
+	// read from first block
+	unsigned char block_buffer[FS_BLOCK_SIZE];
+
+	int block_index = fs_file_descriptions[fd].rw_offset / FS_BLOCK_SIZE;
+	int block_offset = fs_file_descriptions[fd].rw_offset % FS_BLOCK_SIZE;
+
+	read_fd_block(fd, block_index, block_buffer);
+
+	if (block_offset + amount <= FS_BLOCK_SIZE) {
+		memcpy(read_data, &(block_buffer[block_offset]), amount);
+		goto print_read_data;
+	} else {
+		memcpy(read_data, &(block_buffer[block_offset]), FS_BLOCK_SIZE - block_offset);
+		total_read_data_amount += FS_BLOCK_SIZE - block_offset;
+	}
+
+	// read from all next blocks
+	while (amount - total_read_data_amount > 0) {
+		block_index++;
+		read_fd_block(fd, block_index, block_buffer);
+		int bytes_to_read = (amount - total_read_data_amount > FS_BLOCK_SIZE)
+			? FS_BLOCK_SIZE : amount - total_read_data_amount;
+
+		memcpy(&(read_data[total_read_data_amount]), block_buffer, bytes_to_read);
+		total_read_data_amount += bytes_to_read;
+	}
+
+print_read_data:
+	pr("Updating fd %d offset: %d -> %d\n",
+			fd, fs_file_descriptions[fd].rw_offset, fs_file_descriptions[fd].rw_offset+amount);
+	fs_file_descriptions[fd].rw_offset += amount;
+
+	write_stdout(read_data, amount);
+	pr_stdout("\n");
+
+	free(read_data);
+
+	return 0;
+}
+
+int fs_write(void *d)
+{
+	int fd = ((int *) d)[0];
+	char *str = *((char **) d+4);
+	int str_len = strlen(str);
+
+	if (!fs_file_descriptions[fd].inode) {
+		pr_err("fd %d is not open\n", fd);
+		return 0;
+	}
+
+	if (str_len == 0)
+		return 0;
+
+	int block_index = fs_file_descriptions[fd].rw_offset / FS_BLOCK_SIZE;
+	int block_offset = fs_file_descriptions[fd].rw_offset % FS_BLOCK_SIZE;
+
+	unsigned char data_buffer[FS_BLOCK_SIZE];
+
+	if (block_offset + str_len <= FS_BLOCK_SIZE) {
+		read_fd_block(fd, block_index, data_buffer);
+		memcpy(&(data_buffer[block_offset]), str, str_len);
+		write_fd_block(fd, block_index, data_buffer);
+	} else {
+		read_fd_block(fd, block_index, data_buffer);
+		memcpy(&(data_buffer[block_offset]), str, FS_BLOCK_SIZE - block_offset);
+		write_fd_block(fd, block_index, data_buffer);
+
+		read_fd_block(fd, block_index+1, data_buffer);
+		memcpy(data_buffer, &(str[FS_BLOCK_SIZE - block_offset]), str_len - block_offset);
+		write_fd_block(fd, block_index+1, data_buffer);
+	}
+
+	pr("Moving fd %d offset: %d -> %d\n",
+			fd, fs_file_descriptions[fd].rw_offset, fs_file_descriptions[fd].rw_offset + str_len);
+	fs_file_descriptions[fd].rw_offset += str_len;
+
+	return 0;
+}
+
 int fs_close(void *d)
 {
 	int fd = *((int *) d);