--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbox.c	Thu Mar 27 09:53:52 2014 +0500
@@ -0,0 +1,206 @@
+/*
+ * Copyright (c) 2014 Sunil Nimmagadda <sunil@nimmagadda.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/queue.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#include "pop3d.h"
+
+static int init(struct mdrop *, size_t *, size_t *);
+static int retr(struct mdrop *, unsigned int, size_t *, size_t *);
+static int update(struct mdrop *);
+
+struct m_backend m_backend_mbox = {
+	init,
+	retr,
+	update
+};
+
+/* 
+ * Parse mbox calculating each message's offset, size and hash.
+ * A message is identified by "From " at the start of a line.
+ * Returns 0 on success with nmsgs and sz populated.
+ */
+int
+init(struct mdrop *m, size_t *nmsgs, size_t *sz)
+{
+	SHA1_CTX	ctx;
+	FILE		*fp;
+	struct msg	*msg = NULL;
+	size_t		i, len;
+	long		offset;
+	char		*line;
+
+	*nmsgs = 0;
+	*sz = 0;
+	if (flock(m->fd, LOCK_EX|LOCK_NB) == -1) {
+		switch (errno) {
+		case EWOULDBLOCK:
+			logit(LOG_INFO, "mbox: locked by other process");
+			return (-1);
+		default:
+			fatal("flock(LOCK_EX)");
+		}
+	}
+
+	if ((fp = fdopen(dup(m->fd), "r+")) == NULL) {
+		logit(LOG_INFO, "mbox: fdopen failed");
+		return (-1);
+	}
+
+	SIMPLEQ_INIT(&m->e.q_msgs);
+	offset = ftell(fp);
+	while ((line = fgetln(fp, &len))) {
+		if ((len > 5) && strncmp("From ", line, 5) == 0) {
+			if (msg)
+				SHA1End(&ctx, msg->hash);
+
+			msg = xcalloc(1, sizeof(*msg), "init");
+			SHA1Init(&ctx);
+			msg->u.offset = offset;
+			m->nmsgs += 1;
+			SIMPLEQ_INSERT_TAIL(&m->e.q_msgs, msg, e.q_entry);
+		} else {
+			if (msg == NULL)
+				fatalx("mbox corrupted: no \"From \" line");
+
+			msg->sz += len;
+			msg->nlines += 1;
+			SHA1Update(&ctx, (u_int8_t *)line, len);
+			offset = ftell(fp);
+		}
+	}
+
+	if (msg)
+		SHA1End(&ctx, msg->hash);
+
+	/* allocate space for nmsgs of struct msg pointers */
+	m->msgs_index = xcalloc(m->nmsgs, sizeof(msg), "make_index");
+	i = 0;
+	SIMPLEQ_FOREACH(msg, &m->e.q_msgs, e.q_entry) {
+		m->msgs_index[i++] = msg;
+		/* calculate mbox size by counting newline as 2 (CRLF) */
+		m->sz += msg->sz + msg->nlines;
+	}
+
+	*nmsgs = m->nmsgs;
+	*sz = m->sz;
+	fclose(fp);
+	return (0);
+}
+
+static int
+retr(struct mdrop *m, unsigned int idx, size_t *nlines, size_t *offset)
+{
+	if (m->msgs_index[idx]->flags & F_DELE)
+		return (-1);
+
+	*offset = m->msgs_index[idx]->u.offset;
+	*nlines = m->msgs_index[idx]->nlines;
+	return (dup(m->fd)); /* imsg closes sender's fd */
+}
+
+/* 
+ * No resource management as this process is blown away
+ * upon success or error.
+ */
+static int
+update(struct mdrop *m)
+{
+	struct msg	*cur;
+	size_t		i, j = 0, len, nlines;
+	char		buf[MAXBSIZE], fn[22], *line;
+	FILE		*tmp_fp, *m_fp;
+	mode_t		old_mask;
+	int		tmp_fd;
+
+	for (i = 0; i < m->nmsgs; i++)
+		if (m->msgs_index[i]->flags & F_DELE)
+			j += 1;
+
+	if ((m_fp = fdopen(dup(m->fd), "r+")) == NULL) {
+		logit(LOG_INFO, "mbox: fdopen failed");
+		return (-1);
+	}
+
+	if (j == 0)
+		return (0);
+	else if (j == m->nmsgs) {
+		if (ftruncate(fileno(m_fp), 0) == -1) {
+			logit(LOG_CRIT, "update: ftruncate failed");
+			return (1);
+		}
+
+		return (0);
+	}
+
+	strlcpy(fn, "/tmp/pop3d.XXXXXXXXXX", sizeof(fn));
+	old_mask = umask(S_IXUSR|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH);
+	if ((tmp_fd = mkstemp(fn)) == -1 ||
+	    (tmp_fp = fdopen(tmp_fd, "r+")) == NULL) {
+		logit(LOG_CRIT, "mbox: mkstemp failed");
+		return (1);
+	}
+
+	umask(old_mask);
+	for (i = 0; i < m->nmsgs; i++) {
+		cur = m->msgs_index[i];
+		if (cur->flags & F_DELE)
+			continue;
+
+		if (fseek(m_fp, cur->u.offset, SEEK_SET) == -1) {
+			logit(LOG_CRIT, "update: fseek failed");
+			return (1);
+		}
+		/*
+		 * "From " line isn't counted in nlines but offset starts
+		 * there, adjust nlines here 
+		 */
+		nlines = m->msgs_index[i]->nlines + 1;
+		while (nlines--) {
+			if ((line = fgetln(m_fp, &len)))
+				if (fwrite(line, len, 1, tmp_fp) != 1)
+					fatalx("update: short write");
+		}
+	}
+
+	fflush(tmp_fp);
+	rewind(m_fp);
+	rewind(tmp_fp);
+	while (!feof(tmp_fp)) {
+		fread(buf, sizeof(buf), 1, tmp_fp);
+		if (fwrite(buf, sizeof(buf), 1, m_fp) != 1)
+			fatalx("update: short write");
+	}
+
+	fflush(m_fp);
+	if (ftruncate(fileno(m_fp), ftello(tmp_fp)) == -1)
+		fatal("update: failed to truncate");
+
+	fclose(m_fp);
+	return (0);
+}
+