--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/miscellany/less-177/ifile.c	Mon Apr 18 23:46:02 2005 +0900
@@ -0,0 +1,192 @@
+/*
+ * An IFILE represents an input file.
+ *
+ * It is actually a pointer to an ifile structure,
+ * but is opaque outside this module.
+ * Ifile structures are kept in a linked list in the order they 
+ * appear on the command line.
+ * Any new file which does not already appear in the list is
+ * inserted after the current file.
+ */
+
+#include "less.h"
+
+struct ifile {
+	struct ifile *h_next;		/* Links for command line list */
+	struct ifile *h_prev;
+	int h_index;			/* Index within command line list */
+	char *h_filename;		/* Name of the file */
+	struct scrpos h_scrpos;		/* Saved position within the file */
+};
+
+/*
+ * Convert an IFILE (external representation)
+ * to a struct file (internal representation), and vice versa.
+ */
+#define int_ifile(h)	((struct ifile *)(h))
+#define ext_ifile(h)	((IFILE)(h))
+
+/*
+ * Anchor for linked list.
+ */
+static struct ifile anchor = { &anchor, &anchor, 0 };
+static int ifiles = 0;
+
+/*
+ * Allocate a new ifile structure and stick a filename in it.
+ * It should go after "prev" in the list
+ * (or at the beginning of the list if "prev" is NULL).
+ * Return a pointer to the new ifile structure.
+ */
+	static struct ifile *
+new_ifile(filename, prev)
+	char *filename;
+	struct ifile *prev;
+{
+	register struct ifile *p;
+	register struct ifile *np;
+
+	/*
+	 * Allocate and initialize structure.
+	 */
+	p = (struct ifile *) ecalloc(1, sizeof(struct ifile));
+	p->h_filename = filename;
+	p->h_scrpos.pos = NULL_POSITION;
+
+	/*
+	 * Link into list.
+	 */
+	if (prev == NULL)
+		prev = &anchor;
+	p->h_next = prev->h_next;
+	p->h_prev = prev;
+	prev->h_next->h_prev = p;
+	prev->h_next = p;
+
+	/*
+	 * Calculate index for the new one,
+	 * and adjust the indexes for subsequent ifiles in the list.
+	 */
+	p->h_index = prev->h_index + 1;
+	for (np = p->h_next;  np != &anchor;  np = np->h_next)
+		np->h_index++;
+
+	ifiles++;
+	return (p);
+}
+
+/*
+ * Get the ifile after a given one in the list.
+ */
+	public IFILE
+next_ifile(h)
+	IFILE h;
+{
+	register struct ifile *p;
+
+	p = (h == NULL_IFILE) ? &anchor : int_ifile(h);
+	if (p->h_next == &anchor)
+		return (NULL_IFILE);
+	return (ext_ifile(p->h_next));
+}
+
+/*
+ * Get the ifile before a given one in the list.
+ */
+	public IFILE
+prev_ifile(h)
+	IFILE h;
+{
+	register struct ifile *p;
+
+	p = (h == NULL_IFILE) ? &anchor : int_ifile(h);
+	if (p->h_prev == &anchor)
+		return (NULL_IFILE);
+	return (ext_ifile(p->h_prev));
+}
+
+/*
+ * Return the number of ifiles.
+ */
+	public int
+nifile()
+{
+	return (ifiles);
+}
+
+/*
+ * Find an ifile structure, given a filename.
+ */
+	static struct ifile *
+find_ifile(filename)
+	char *filename;
+{
+	register struct ifile *p;
+
+	for (p = anchor.h_next;  p != &anchor;  p = p->h_next)
+		if (strcmp(filename, p->h_filename) == 0)
+			return (p);
+	return (NULL);
+}
+
+/*
+ * Get the ifile associated with a filename.
+ * If the filename has not been seen before,
+ * insert the new ifile after "prev" in the list.
+ */
+	public IFILE
+get_ifile(filename, prev)
+	char *filename;
+	IFILE prev;
+{
+	register struct ifile *p;
+
+	if ((p = find_ifile(filename)) == NULL)
+		p = new_ifile(save(filename), int_ifile(prev));
+	return (ext_ifile(p));
+}
+
+/*
+ * Get the filename associated with a ifile.
+ */
+	public char *
+get_filename(ifile)
+	IFILE ifile;
+{
+	if (ifile == NULL)
+		return (NULL);
+	return (int_ifile(ifile)->h_filename);
+}
+
+/*
+ * Get the index of the file associated with a ifile.
+ */
+	public int
+get_index(ifile)
+	IFILE ifile;
+{
+	return (int_ifile(ifile)->h_index); 
+}
+
+/*
+ * Save the file position to be associated with a given file.
+ */
+	public void
+store_pos(ifile, scrpos)
+	IFILE ifile;
+	struct scrpos *scrpos;
+{
+	int_ifile(ifile)->h_scrpos = *scrpos;
+}
+
+/*
+ * Recall the file position associated with a file.
+ * If no position has been associated with the file, return NULL_POSITION.
+ */
+	public void
+get_pos(ifile, scrpos)
+	IFILE ifile;
+	struct scrpos *scrpos;
+{
+	*scrpos = int_ifile(ifile)->h_scrpos;
+}