Inital import

Still far from useable

1 files changed, 311 insertions, 0 deletions

diff --git a/editor.c b/editor.c
new file mode 100644
index 0000000..77a16c7
--- /dev/null
+++ b/editor.c
@@ -0,0 +1,311 @@
+#define _BSD_SOURCE
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include "editor.h"
+
+typedef struct {
+	size_t len, pos;
+	char *content;
+} Buffer;
+
+typedef struct Piece Piece;
+struct Piece {
+	Piece *prev, *next;
+	char *content;
+	size_t len;
+	// size_t line_count;
+	int index;
+};
+
+typedef struct {
+	Piece *piece;
+	size_t off;
+} Location;
+
+typedef struct {
+	Piece *start, *end;
+	size_t len;
+	// size_t line_count;
+} Span;
+
+typedef struct Change Change;
+struct Change {
+	Span old, new;
+	Change *next;
+};
+
+typedef struct Action Action;
+struct Action {
+	Change *change;
+	Action *next; //, *prev;
+	time_t timestamp;
+};
+
+struct Editor {
+	Buffer buf;
+	Piece begin, end;
+	Action *redo, *undo, *current_action;
+	size_t size;
+	bool modified;
+	struct stat info;
+	int fd;
+	const char *filename;
+};
+
+static void span_init(Span *span, Piece *start, Piece *end) {
+	size_t len = 0;
+	span->start = start;
+	span->end = end;
+	for (Piece *p = start; p; p = p->next) {
+		len += p->len;
+		if (p == end)
+			break;
+	}
+	span->len = len;
+}
+
+static void span_swap(Editor *ed, Span *old, Span *new) {
+	/* TODO use a balanced search tree to keep the pieces
+		instead of a doubly linked list.
+	 */
+	if (!old || old->len == 0) {
+		/* insert new span */
+		new->start->prev->next = new->start;
+		new->end->next->prev = new->end;
+	} else if (!new || new->len == 0) {
+		/* delete old span */
+		old->start->prev->next = old->end->next;
+		old->end->next->prev = old->start->prev;
+	} else {
+		/* replace old with new */
+		old->start->prev->next = new->start;
+		old->end->next->prev = new->end;
+	}
+	ed->size -= old->len;
+	ed->size += new->len;
+}
+
+static void action_push(Action **stack, Action *action) {
+	action->next = *stack;
+	*stack = action; 
+}
+
+static Action *action_pop(Action **stack) {
+	Action *action = *stack;
+	if (action)
+		*stack = action->next;
+	return action;
+}
+
+static Action *action_alloc(Editor *ed) {
+	Action *a = calloc(1, sizeof(Action));
+	if (!a)
+		return NULL;
+	ed->current_action = a;
+	action_push(&ed->undo, a);
+	return a;
+}
+
+static Piece *piece_alloc() {
+	static int piece_count = 3;
+	Piece *p = malloc(sizeof(Piece));
+	if (!p)
+		return NULL;
+	p->index = piece_count++;
+	return p;
+}
+
+static void piece_init(Piece *p, Piece *prev, Piece *next, char *content, size_t len) {
+	p->prev = prev;
+	p->next = next;
+	p->content = content;
+	p->len = len;
+}
+
+static Location piece_get(Editor *ed, size_t pos) {
+	Location loc = {};
+	// TODO: handle position at end of file: pos+1 
+	size_t cur = 0;
+	for (Piece *p = ed->begin.next; p->next; p = p->next) {
+		if (cur <= pos && pos <= cur + p->len) {
+			loc.piece = p;
+			loc.off = pos - cur;
+			return loc;
+		}
+		cur += p->len;
+	}
+
+	return loc;
+}
+
+static void change_add(Action *a, Change *c) {
+	c->next = a->change;
+	a->change = c;
+}
+
+static Change *change_alloc(Editor *ed) {
+	Action *a = ed->current_action;
+	if (!a) {
+		a = action_alloc(ed);
+		if (!a)
+			return NULL;
+	}
+	Change *c = calloc(1, sizeof(Change));
+	if (!c)
+		return NULL;
+	change_add(a, c);
+	return c;
+}
+
+void editor_insert(Editor *ed, size_t pos, char *text) {
+	Location loc = piece_get(ed, pos);
+	Piece *p = loc.piece;
+	size_t off = loc.off;
+	Change *c = change_alloc(ed);
+	/* insert into middle of an existing piece, therfore split the old
+	 * piece. that is we have 3 new pieces one containing the content
+	 * before the insertion point then one holding the newly inserted 
+	 * text and one holding the content after the insertion point.
+	 */
+	Piece *before = piece_alloc();
+	Piece *new = piece_alloc();
+	Piece *after = piece_alloc();
+
+	// TODO: check index calculation
+	piece_init(before, p->prev, new, p->content, off);
+	piece_init(new, before, after, text /* TODO */, strlen(text) /* TODO */);
+	piece_init(after, new, p->next, p->content + off, p->len - off);
+
+	span_init(&c->new, before, after);
+	span_init(&c->old, p, p);
+
+	span_swap(ed, &c->old, &c->new);
+}
+
+bool editor_undo(Editor *ed) {
+	Action *a = action_pop(&ed->undo);
+	if (!a)
+		return false;
+	for (Change *c = a->change; c; c = c->next) {
+		span_swap(ed, &c->new, &c->old);
+	}
+
+	action_push(&ed->redo, a);	
+	return true;
+}
+
+bool editor_redo(Editor *ed) {
+	Action *a = action_pop(&ed->redo);
+	if (!a)
+		return false;
+	for (Change *c = a->change; c; c = c->next) {
+		span_swap(ed, &c->old, &c->new);
+	}
+
+	action_push(&ed->undo, a);
+	return true;
+}
+
+Iterate copy_content(void *data, size_t pos, const char *content, size_t len) {
+	char **p = (char **)data;
+	memcpy(*p, content, len);
+	*p += len;
+	return CONTINUE;
+}
+
+int editor_save(Editor *ed, const char *filename) {
+	size_t len = strlen(filename) + 10;
+	char tmpname[len];
+	snprintf(tmpname, len, ".%s.tmp", filename);
+	// TODO file ownership, permissions etc
+	/* O_RDWR is needed because otherwise we can't map with MAP_SHARED */
+	int fd = open(tmpname, O_CREAT|O_RDWR|O_TRUNC, S_IRUSR|S_IWUSR);
+	if (fd == -1)
+		return -1;
+	ftruncate(fd, ed->size);
+	void *buf = mmap(NULL, ed->size, PROT_WRITE, MAP_SHARED, fd, 0);
+	if (buf == MAP_FAILED)
+		goto err;
+
+	void *cur = buf;
+	editor_iterate(ed, &cur, 0, copy_content);
+
+	if (munmap(buf, ed->size) == -1)
+		goto err;
+	if (close(fd) == -1)
+		return -1;
+	return rename(tmpname, filename);
+err:
+	close(fd);
+	return -1;
+}
+
+Editor *editor_load(const char *filename) {
+	Editor *ed = calloc(1, sizeof(Editor));
+	if (!ed)
+		return NULL;
+	ed->begin.index = 1;
+	ed->end.index = 2;
+	piece_init(&ed->begin, NULL, &ed->end, NULL, 0);
+	piece_init(&ed->end, &ed->begin, NULL, NULL, 0);
+	if (filename) {
+		ed->filename = filename;
+		ed->fd = open(filename, O_RDONLY);
+		if (ed->fd == -1)
+			goto out;
+		if (fstat(ed->fd, &ed->info) == -1)
+			goto out;
+		if (!S_ISREG(ed->info.st_mode))
+			goto out;
+		// XXX: use lseek(fd, 0, SEEK_END); instead?
+		ed->buf.len = ed->info.st_size;
+		ed->buf.content = mmap(NULL, ed->info.st_size, PROT_READ, MAP_SHARED, ed->fd, 0);
+		if (ed->buf.content == MAP_FAILED)
+			goto out;
+		Piece *p = piece_alloc();
+		piece_init(&ed->begin, NULL, p, NULL, 0);
+		piece_init(p, &ed->begin, &ed->end, ed->buf.content, ed->buf.len);
+		piece_init(&ed->end, p, NULL, NULL, 0);
+		ed->size = ed->buf.len;
+	}
+	return ed;
+out:
+	if (ed->fd > 2)
+		close(ed->fd);
+	free(ed);
+	return NULL;
+}
+
+static void print_piece(Piece *p) {
+	fprintf(stderr, "index: %d\tnext: %d\tprev: %d\n", p->index,
+		p->next ? p->next->index : -1, 
+		p->prev ? p->prev->index : -1);
+	fflush(stderr);
+	write(1, p->content, p->len);
+	write(1, "\n", 1);
+}
+
+void editor_debug(Editor *ed) {
+	for (Piece *p = &ed->begin; p; p = p->next) {
+		print_piece(p);
+	}
+}
+
+void editor_iterate(Editor *ed, void *data, size_t pos, iterator_callback_t callback) {
+	Location loc = piece_get(ed, pos);
+	Piece *p = loc.piece;
+	Iterate cont = callback(data, pos, p ? p->content : NULL, p ? p->len - loc.off : 0);
+	if (p)
+		pos += p->len - loc.off;
+	while (p && (cont = callback(data, pos, p->content, p->len)) == CONTINUE)
+		p = p->next;
+}