patch-2.4.15 linux/fs/seq_file.c

• Lines: 296
• Date: Sat Nov 17 18:16:22 2001
• Orig file: v2.4.14/linux/fs/seq_file.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.14/linux/fs/seq_file.c linux/fs/seq_file.c
@@ -0,0 +1,295 @@
+/*
+ * linux/fs/seq_file.c
+ *
+ * helper functions for making syntetic files from sequences of records.
+ * initial implementation -- AV, Oct 2001.
+ */
+
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+
+#include <asm/uaccess.h>
+
+/**
+ *	seq_open -	initialize sequential file
+ *	@file: file we initialize
+ *	@op: method table describing the sequence
+ *
+ *	seq_open() sets @file, associating it with a sequence described
+ *	by @op.  @op->start() sets the iterator up and returns the first
+ *	element of sequence. @op->stop() shuts it down.  @op->next()
+ *	returns the next element of sequence.  @op->show() prints element
+ *	into the buffer.  In case of error ->start() and ->next() return
+ *	ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
+ *	returns 0 in case of success and negative number in case of error.
+ */
+int seq_open(struct file *file, struct seq_operations *op)
+{
+	struct seq_file *p = kmalloc(sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+	memset(p, 0, sizeof(*p));
+	sema_init(&p->sem, 1);
+	p->op = op;
+	file->private_data = p;
+	return 0;
+}
+
+/**
+ *	seq_read -	->read() method for sequential files.
+ *	@file, @buf, @size, @ppos: see file_operations method
+ *
+ *	Ready-made ->f_op->read()
+ */
+ssize_t seq_read(struct file *file, char *buf, size_t size, loff_t *ppos)
+{
+	struct seq_file *m = (struct seq_file *)file->private_data;
+	size_t copied = 0;
+	loff_t pos;
+	size_t n;
+	void *p;
+	int err = 0;
+
+	if (ppos != &file->f_pos)
+		return -EPIPE;
+
+	down(&m->sem);
+	/* grab buffer if we didn't have one */
+	if (!m->buf) {
+		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
+		if (!m->buf)
+			goto Enomem;
+	}
+	/* if not empty - flush it first */
+	if (m->count) {
+		n = min(m->count, size);
+		err = copy_to_user(buf, m->buf + m->from, n);
+		if (err)
+			goto Efault;
+		m->count -= n;
+		m->from += n;
+		size -= n;
+		buf += n;
+		copied += n;
+		if (!m->count)
+			m->index++;
+		if (!size)
+			goto Done;
+	}
+	/* we need at least one record in buffer */
+	while (1) {
+		pos = m->index;
+		p = m->op->start(m, &pos);
+		err = PTR_ERR(p);
+		if (!p || IS_ERR(p))
+			break;
+		err = m->op->show(m, p);
+		if (err)
+			break;
+		if (m->count < m->size)
+			goto Fill;
+		m->op->stop(m, p);
+		kfree(m->buf);
+		m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
+		if (!m->buf)
+			goto Enomem;
+	}
+	m->op->stop(m, p);
+	goto Done;
+Fill:
+	/* they want more? let's try to get some more */
+	while (m->count < size) {
+		size_t offs = m->count;
+		loff_t next = pos;
+		p = m->op->next(m, p, &next);
+		if (!p || IS_ERR(p)) {
+			err = PTR_ERR(p);
+			break;
+		}
+		err = m->op->show(m, p);
+		if (err || m->count == m->size) {
+			m->count = offs;
+			break;
+		}
+		pos = next;
+	}
+	m->op->stop(m, p);
+	n = min(m->count, size);
+	err = copy_to_user(buf, m->buf, n);
+	if (err)
+		goto Efault;
+	copied += n;
+	m->count -= n;
+	if (m->count)
+		m->from = n;
+	else
+		pos++;
+	m->index = pos;
+Done:
+	if (!copied)
+		copied = err;
+	else
+		*ppos += copied;
+	up(&m->sem);
+	return copied;
+Enomem:
+	err = -ENOMEM;
+	goto Done;
+Efault:
+	err = -EFAULT;
+	goto Done;
+}
+
+static int traverse(struct seq_file *m, loff_t offset)
+{
+	loff_t pos = 0;
+	int error = 0;
+	void *p;
+
+	m->index = 0;
+	m->count = m->from = 0;
+	if (!offset)
+		return 0;
+	if (!m->buf) {
+		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
+		if (!m->buf)
+			return -ENOMEM;
+	}
+	p = m->op->start(m, &m->index);
+	while (p) {
+		error = PTR_ERR(p);
+		if (IS_ERR(p))
+			break;
+		error = m->op->show(m, p);
+		if (error)
+			break;
+		if (m->count == m->size)
+			goto Eoverflow;
+		if (pos + m->count > offset) {
+			m->from = offset - pos;
+			m->count -= m->from;
+			break;
+		}
+		pos += m->count;
+		m->count = 0;
+		if (pos == offset) {
+			m->index++;
+			break;
+		}
+		p = m->op->next(m, p, &m->index);
+	}
+	m->op->stop(m, p);
+	return error;
+
+Eoverflow:
+	m->op->stop(m, p);
+	kfree(m->buf);
+	m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
+	return !m->buf ? -ENOMEM : -EAGAIN;
+}
+
+/**
+ *	seq_lseek -	->llseek() method for sequential files.
+ *	@file, @offset, @origin: see file_operations method
+ *
+ *	Ready-made ->f_op->llseek()
+ */
+loff_t seq_lseek(struct file *file, loff_t offset, int origin)
+{
+	struct seq_file *m = (struct seq_file *)file->private_data;
+	long long retval = -EINVAL;
+
+	down(&m->sem);
+	switch (origin) {
+		case 1:
+			offset += file->f_pos;
+		case 0:
+			if (offset < 0)
+				break;
+			retval = offset;
+			if (offset != file->f_pos) {
+				while ((retval=traverse(m, offset)) == -EAGAIN)
+					;
+				if (retval) {
+					/* with extreme perjudice... */
+					file->f_pos = 0;
+					m->index = 0;
+					m->count = 0;
+				} else {
+					retval = file->f_pos = offset;
+				}
+			}
+	}
+	up(&m->sem);
+	return retval;
+}
+
+/**
+ *	seq_release -	free the structures associated with sequential file.
+ *	@file: file in question
+ *	@inode: file->f_dentry->d_inode
+ *
+ *	Frees the structures associated with sequential file; can be used
+ *	as ->f_op->release() if you don't have private data to destroy.
+ */
+int seq_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *m = (struct seq_file *)file->private_data;
+	kfree(m->buf);
+	kfree(m);
+	return 0;
+}
+
+/**
+ *	seq_escape -	print string into buffer, escaping some characters
+ *	@m:	target buffer
+ *	@s:	string
+ *	@esc:	set of characters that need escaping
+ *
+ *	Puts string into buffer, replacing each occurence of character from
+ *	@esc with usual octal escape.  Returns 0 in case of success, -1 - in
+ *	case of overflow.
+ */
+int seq_escape(struct seq_file *m, const char *s, const char *esc)
+{
+	char *end = m->buf + m->size;
+        char *p;
+	char c;
+
+        for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
+		if (!strchr(esc, c)) {
+			*p++ = c;
+			continue;
+		}
+		if (p + 3 < end) {
+			*p++ = '\\';
+			*p++ = '0' + ((c & 0300) >> 6);
+			*p++ = '0' + ((c & 070) >> 3);
+			*p++ = '0' + (c & 07);
+			continue;
+		}
+		m->count = m->size;
+		return -1;
+        }
+	m->count = p - m->buf;
+        return 0;
+}
+
+int seq_printf(struct seq_file *m, const char *f, ...)
+{
+	va_list args;
+	int len;
+
+	if (m->count < m->size) {
+		va_start(args, f);
+		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
+		va_end(args);
+		if (m->count + len < m->size) {
+			m->count += len;
+			return 0;
+		}
+	}
+	m->count = m->size;
+	return -1;
+}