From 3ee64e5b5dc5ca2f3b37df02523baae0dbf7993b Mon Sep 17 00:00:00 2001
From: hasslesstech <hasslesstech@tutanota.com>
Date: Sat, 26 Apr 2025 22:12:26 +0300
Subject: [PATCH] add truncate

---
 inc/fs.h  |   1 +
 src/cli.c |   2 +-
 src/fs.c  | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+), 1 deletion(-)

diff --git a/inc/fs.h b/inc/fs.h
index 6abd122..74fa310 100644
--- a/inc/fs.h
+++ b/inc/fs.h
@@ -60,5 +60,6 @@ int fs_seek(void *d);
 int fs_read(void *d);
 int fs_write(void *d);
 int fs_close(void *d);
+int fs_truncate(void *d);
 int fs_allow_write(void *d);
 int fs_prohibit_write(void *d);
diff --git a/src/cli.c b/src/cli.c
index d17fa36..5f98a5a 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -19,7 +19,7 @@ static const struct CliCommandEntry cmd[] = {
 	{"ls", 0, NULL, fs_ls},
 	{"ln", 2, (enum CliArgType[]) {STR, STR}, fs_ln},
 	{"rm", 1, (enum CliArgType[]) {STR}, fs_rm},
-	//{"truncate", 2, (enum CliArgType[]) {STR, INT}, fs_truncate},
+	{"truncate", 2, (enum CliArgType[]) {STR, INT}, fs_truncate},
 	{"open", 1, (enum CliArgType[]) {STR}, fs_open},
 	{"seek", 2, (enum CliArgType[]) {INT, INT}, fs_seek},
 	{"read", 2, (enum CliArgType[]) {INT, INT}, fs_read},
diff --git a/src/fs.c b/src/fs.c
index 21abef2..0960f5c 100644
--- a/src/fs.c
+++ b/src/fs.c
@@ -902,6 +902,112 @@ int fs_write(void *d)
 	return 0;
 }
 
+int fs_truncate(void *d)
+{
+	char *fname = *((char **) d);
+	int size = *((int *) ((char **) d+1));
+
+	if (size < 0) {
+		pr_err("file size can not be negative\n");
+		return 0;
+	}
+
+	int file_inode_ptr;
+	{
+		int *r = find_filename_in_directory(fs_cwd_inode_ptr, fname);
+		if (r == NULL) {
+			pr_err("no such file: '%s'\n", fname);
+			return 0;
+		}
+
+		file_inode_ptr = r[2];
+		free(r);
+	}
+
+	struct fs_inode f;
+	read_block(read_inode_ptr(file_inode_ptr), (void *) &f);
+
+	if (size > f.size) {
+		pr("Increasing file size of '%s': %d -> %d\n", fname, f.size, size);
+		f.size = size;
+		write_block(read_inode_ptr(file_inode_ptr), (void *) &f);
+	} else {
+		pr("Decreasing file size of '%s': %d -> %d\n", fname, f.size, size);
+		f.size = size;
+
+		// cleanup
+		int new_block_amount = f.size / FS_BLOCK_SIZE;
+		if (f.size % FS_BLOCK_SIZE)
+			new_block_amount++;
+
+		int blocks_seen = 0;
+
+		// look through base inode blocks
+		for (int i = 0; i < BLOCK_ADDRESSES_PER_INODE; i++, blocks_seen++) {
+			if ((blocks_seen > new_block_amount) && (f.blocks[i])) {
+				mark_free(f.blocks[i]);
+				f.blocks[i] = 0;
+			}
+		}
+		write_block(read_inode_ptr(file_inode_ptr), (void *) &f);
+
+		// look through inode extension blocks
+		struct fs_inode_extension ext;
+		unsigned int next_ext = f.next_extension;
+		unsigned int curr_ext;
+
+		while (next_ext) {
+			read_block(next_ext, (void *) &ext);
+
+			for (int i = 0; i < BLOCK_ADDRESSES_PER_INODE_EXTENSION; i++, blocks_seen++) {
+				if ((blocks_seen > new_block_amount) && (ext.blocks[i])) {
+					mark_free(ext.blocks[i]);
+					ext.blocks[i] = 0;
+				}
+			}
+
+			write_block(next_ext, (void *) &ext);
+			next_ext = ext.next_extension;
+		}
+
+		// look through inode extensions themselves
+		int required_extensions = (f.size - BLOCK_ADDRESSES_PER_INODE) / BLOCK_ADDRESSES_PER_INODE_EXTENSION;
+		if ((f.size - BLOCK_ADDRESSES_PER_INODE) % BLOCK_ADDRESSES_PER_INODE_EXTENSION)
+			required_extensions++;
+
+		next_ext = f.next_extension;
+
+		if (!required_extensions) {
+			// zero base inode next_extension ptr
+			f.next_extension = 0;
+			write_block(read_inode_ptr(file_inode_ptr), (void *) &f);
+		}
+
+		// seek to last required extension
+		for (int i = 0; i < required_extensions; i++) {
+			if (!next_ext)
+				return 0;
+
+			curr_ext = next_ext;
+			read_block(next_ext, (void *) &ext);
+			next_ext = ext.next_extension;
+		}
+
+		// remove next_extension ptr
+		ext.next_extension = 0;
+		write_block(curr_ext, (void *) &ext);
+
+		// erase all extensions after this one
+		while (next_ext) {
+			mark_free(next_ext);
+			read_block(next_ext, (void *) &ext);
+			next_ext = ext.next_extension;
+		}
+	}
+
+	return 0;
+}
+
 int fs_close(void *d)
 {
 	int fd = *((int *) d);