[PATCH 6/8] imap-send: change msg_data from storing (char *, len) to storing strbuf

[Michael Haggerty <mhagger@alum.mit.edu>]

struct msg_data stored (char *, len) of the data to be included in a
message, kept the character data NUL-terminated, etc., much like a
strbuf would do.  So change it to use a struct strbuf.  This makes the
code clearer and reduces copying a little bit.

A side effect of this change is that the memory for each message is
freed after it is used rather than leaked, though that detail is
unimportant given that imap-send is a top-level command.

--

For some reason, there is a bunch of infrastructure in this file for
dealing with IMAP flags, although there is nothing in the code that
actually allows any flags to be set.  If there is no plan to add
support for flags in the future, a bunch of code could be ripped out
and "struct msg_data" could be completely replaced with strbuf.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 imap-send.c | 92 +++++++++++++++++++++++++++++++------------------------------
 1 file changed, 47 insertions(+), 45 deletions(-)

diff --git a/imap-send.c b/imap-send.c
index 86cf603..a5e0e33 100644
--- a/imap-send.c
+++ b/imap-send.c
@@ -69,12 +69,7 @@ struct store {
 };
 
 struct msg_data {
-	/* NUL-terminated data: */
-	char *data;
-
-	/* length of data (not including NUL): */
-	int len;
-
+	struct strbuf data;
 	unsigned char flags;
 };
 
@@ -1268,46 +1263,49 @@ static int imap_make_flags(int flags, char *buf)
 	return d;
 }
 
-static void lf_to_crlf(struct msg_data *msg)
+static void lf_to_crlf(struct strbuf *msg)
 {
+	size_t new_len;
 	char *new;
 	int i, j, lfnum = 0;
 
-	if (msg->data[0] == '\n')
+	if (msg->buf[0] == '\n')
 		lfnum++;
 	for (i = 1; i < msg->len; i++) {
-		if (msg->data[i - 1] != '\r' && msg->data[i] == '\n')
+		if (msg->buf[i - 1] != '\r' && msg->buf[i] == '\n')
 			lfnum++;
 	}
 
-	new = xmalloc(msg->len + lfnum + 1);
-	if (msg->data[0] == '\n') {
+	new_len = msg->len + lfnum;
+	new = xmalloc(new_len + 1);
+	if (msg->buf[0] == '\n') {
 		new[0] = '\r';
 		new[1] = '\n';
 		i = 1;
 		j = 2;
 	} else {
-		new[0] = msg->data[0];
+		new[0] = msg->buf[0];
 		i = 1;
 		j = 1;
 	}
 	for ( ; i < msg->len; i++) {
-		if (msg->data[i] != '\n') {
-			new[j++] = msg->data[i];
+		if (msg->buf[i] != '\n') {
+			new[j++] = msg->buf[i];
 			continue;
 		}
-		if (msg->data[i - 1] != '\r')
+		if (msg->buf[i - 1] != '\r')
 			new[j++] = '\r';
 		/* otherwise it already had CR before */
 		new[j++] = '\n';
 	}
-	new[j] = '\0';
-	msg->len += lfnum;
-	free(msg->data);
-	msg->data = new;
+	strbuf_attach(msg, new, new_len, new_len + 1);
 }
 
-static int imap_store_msg(struct store *gctx, struct msg_data *data)
+/*
+ * Store msg to IMAP.  Also detach and free the data from msg->data,
+ * leaving msg->data empty.
+ */
+static int imap_store_msg(struct store *gctx, struct msg_data *msg)
 {
 	struct imap_store *ctx = (struct imap_store *)gctx;
 	struct imap *imap = ctx->imap;
@@ -1316,16 +1314,15 @@ static int imap_store_msg(struct store *gctx, struct msg_data *data)
 	int ret, d;
 	char flagstr[128];
 
-	lf_to_crlf(data);
+	lf_to_crlf(&msg->data);
 	memset(&cb, 0, sizeof(cb));
 
-	cb.dlen = data->len;
-	cb.data = xmalloc(cb.dlen);
-	memcpy(cb.data, data->data, data->len);
+	cb.dlen = msg->data.len;
+	cb.data = strbuf_detach(&msg->data, NULL);
 
 	d = 0;
-	if (data->flags) {
-		d = imap_make_flags(data->flags, flagstr);
+	if (msg->flags) {
+		d = imap_make_flags(msg->flags, flagstr);
 		flagstr[d++] = ' ';
 	}
 	flagstr[d] = 0;
@@ -1356,7 +1353,8 @@ static void encode_html_chars(struct strbuf *p)
 			strbuf_splice(p, i, 1, "&quot;", 6);
 	}
 }
-static void wrap_in_html(struct msg_data *msg)
+
+static void wrap_in_html(struct strbuf *msg)
 {
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf **lines;
@@ -1366,9 +1364,7 @@ static void wrap_in_html(struct msg_data *msg)
 	static char *pre_close = "</pre>\n";
 	int added_header = 0;
 
-	strbuf_attach(&buf, msg->data, msg->len, msg->len);
-	lines = strbuf_split(&buf, '\n');
-	strbuf_release(&buf);
+	lines = strbuf_split(msg, '\n');
 	for (p = lines; *p; p++) {
 		if (! added_header) {
 			if ((*p)->len == 1 && *((*p)->buf) == '\n') {
@@ -1385,8 +1381,8 @@ static void wrap_in_html(struct msg_data *msg)
 	}
 	strbuf_addstr(&buf, pre_close);
 	strbuf_list_free(lines);
-	msg->len  = buf.len;
-	msg->data = strbuf_detach(&buf, NULL);
+	strbuf_release(msg);
+	*msg = buf;
 }
 
 #define CHUNKSIZE 0x1000
@@ -1425,34 +1421,39 @@ static int count_messages(struct strbuf *all_msgs)
 	return count;
 }
 
-static int split_msg(struct strbuf *all_msgs, struct msg_data *msg, int *ofs)
+/*
+ * Copy the next message from all_msgs, starting at offset *ofs, to
+ * msg.  Update *ofs to the start of the following message.  Return
+ * true iff a message was successfully copied.
+ */
+static int split_msg(struct strbuf *all_msgs, struct strbuf *msg, int *ofs)
 {
 	char *p, *data;
+	size_t len;
 
-	memset(msg, 0, sizeof *msg);
 	if (*ofs >= all_msgs->len)
 		return 0;
 
 	data = &all_msgs->buf[*ofs];
-	msg->len = all_msgs->len - *ofs;
+	len = all_msgs->len - *ofs;
 
-	if (msg->len < 5 || prefixcmp(data, "From "))
+	if (len < 5 || prefixcmp(data, "From "))
 		return 0;
 
 	p = strchr(data, '\n');
 	if (p) {
-		p = &p[1];
-		msg->len -= p-data;
-		*ofs += p-data;
+		p++;
+		len -= p - data;
+		*ofs += p - data;
 		data = p;
 	}
 
 	p = strstr(data, "\nFrom ");
 	if (p)
-		msg->len = &p[1] - data;
+		len = &p[1] - data;
 
-	msg->data = xmemdupz(data, msg->len);
-	*ofs += msg->len;
+	strbuf_add(msg, data, len);
+	*ofs += len;
 	return 1;
 }
 
@@ -1504,7 +1505,7 @@ static int git_imap_config(const char *key, const char *val, void *cb)
 int main(int argc, char **argv)
 {
 	struct strbuf all_msgs = STRBUF_INIT;
-	struct msg_data msg;
+	struct msg_data msg = {STRBUF_INIT, 0};
 	struct store *ctx = NULL;
 	int ofs = 0;
 	int r;
@@ -1564,11 +1565,12 @@ int main(int argc, char **argv)
 	ctx->name = imap_folder;
 	while (1) {
 		unsigned percent = n * 100 / total;
+
 		fprintf(stderr, "%4u%% (%d/%d) done\r", percent, n, total);
-		if (!split_msg(&all_msgs, &msg, &ofs))
+		if (!split_msg(&all_msgs, &msg.data, &ofs))
 			break;
 		if (server.use_html)
-			wrap_in_html(&msg);
+			wrap_in_html(&msg.data);
 		r = imap_store_msg(ctx, &msg);
 		if (r != DRV_OK)
 			break;
-- 
1.8.0