Revert "maxmind: Simplify our read logic."

This reverts commit 4154e35cde9c863ace57598cabc37034dab2ab1c.

Apparently we do need to call PeekNamedPipe on Windows.

Change-Id: I9c9bbcb56bf1e1c2e6ae240ac5056b8a80674f15
Reviewed-on: https://code.wireshark.org/review/30900
Reviewed-by: Gerald Combs <gerald@wireshark.org>

1 files changed, 28 insertions, 14 deletions

diff --git a/epan/maxmind_db.c b/epan/maxmind_db.c
index 661ed4f663..9170cb23a1 100644
--- a/epan/maxmind_db.c
+++ b/epan/maxmind_db.c
@@ -180,10 +180,23 @@ write_mmdbr_stdin_worker(gpointer sifd_data) {
     return NULL;
 }
 
+static ssize_t mmdbr_pipe_read_one(char *ch_p) {
+    ssize_t status = -1;
+    g_rw_lock_reader_lock(&mmdbr_pipe_mtx);
+    if (ws_pipe_valid(&mmdbr_pipe) && ws_pipe_data_available(mmdbr_pipe.stdout_fd)) {
+        status = ws_read(mmdbr_pipe.stdout_fd, ch_p, 1);
+    }
+    g_rw_lock_reader_unlock(&mmdbr_pipe_mtx);
+    return status;
+}
+
 // We need to read a series of lines from mmdbresolve's stdout. Trying to
-// use fgets is problematic because it blocks on Windows. Doing so in a
-// thread is even worse since it locks the I/O stream and if the main
+// use fgets is problematic because it blocks on Windows blocks. Doing so
+// in a thread is even worse since it locks the I/O stream and if the main
 // thread calls fclose while fgets is blocking, it will block as well.
+//
+// Read our input one character at a time and only after we've ensured
+// that data is available.
 #define MAX_MMDB_LINE_LEN 2000
 static gpointer
 read_mmdbr_stdout_worker(gpointer data _U_) {
@@ -199,17 +212,11 @@ read_mmdbr_stdout_worker(gpointer data _U_) {
     while (1) { // Start of line
         char cur_addr[WS_INET6_ADDRSTRLEN];
         char ch;
-        ssize_t resp_status;
+        ssize_t status;
 
         g_string_truncate(line_buf, 0);
 
-        if (!mmdbr_pipe_valid()) {
-            // Should be due to mmdb_resolve_stop.
-            MMDB_DEBUG("invalid mmdbr stdout pipe. exiting thread.");
-            break;
-        }
-
-        while((resp_status = ws_read(mmdbr_pipe.stdout_fd, &ch, 1)) == 1) {
+        while((status = mmdbr_pipe_read_one(&ch)) == 1) {
             if (ch == '\n') {
                 break;
             }
@@ -217,14 +224,21 @@ read_mmdbr_stdout_worker(gpointer data _U_) {
             g_string_append_c(line_buf, ch);
 
             if (line_buf->len > MAX_MMDB_LINE_LEN) {
-                MMDB_DEBUG("long line. marking invalid.");
+                MMDB_DEBUG("long line");
                 g_string_printf(line_buf, "%s", RES_INVALID_LINE);
             }
         }
 
-        if (resp_status != 1) {
-            MMDB_DEBUG("read error %s. exiting thread.", g_strerror(errno));
-            break;
+        if (status != 1) {
+            if (!mmdbr_pipe_valid()) {
+                // Should be due to mmdb_resolve_stop.
+                MMDB_DEBUG("invalid mmdbr stdout pipe. exiting thread.");
+                break;
+            }
+
+            MMDB_DEBUG("no pipe data");
+            g_usleep(MMDB_WAIT_TIME);
+            continue;
         }
 
         char *line = g_strstrip(line_buf->str);