[Xen-devel] [PATCH v3 19/31] libxl_qmp_ev: Parse JSON input from QMP

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 tools/libxl/libxl_qmp.c | 98 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index 48dc376307..e4441f76f4 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -1383,7 +1383,9 @@ static int ev_qmp_callback_readable(libxl__egc *egc, 
libxl__ev_qmp_state *qmp,
 {
     EGC_GC;
     ssize_t r;
+    char *end = NULL;
     libxl__qmp_rx_buf *buf;
+    int rc;
 
     /* Check if last buffer still have space, or alloc a new one */
     buf = LIBXL_TAILQ_LAST(&qmp->bufs, libxl__qmp_bufs);
@@ -1425,6 +1427,102 @@ static int ev_qmp_callback_readable(libxl__egc *egc, 
libxl__ev_qmp_state *qmp,
     buf->used += r;
     assert(buf->used < sizeof(buf->buf));
 
+    /* workaround strstr limitation */
+    buf->buf[buf->used] = '\0';
+
+    /*
+     * Search for the end of a QMP message: "\r\n".
+     * - First check if those two chr were received accross 2 read.
+     * - Then, look for them within the newly read data.
+     *
+     * end: This point to the address right after \r\n
+     */
+    if (buf->buf[buf->used - r] == '\n') {
+        /* First new chr read is \n, look if the previous one is \r. */
+
+        if (buf->used - r == 0) {
+            libxl__qmp_rx_buf *prev_buf;
+
+            prev_buf = LIBXL_TAILQ_PREV(buf, libxl__qmp_bufs, entry);
+            if (prev_buf &&
+                prev_buf->buf[prev_buf->used - 1] == '\r') {
+                end = buf->buf + 1;
+            }
+        } else if (buf->buf[buf->used - r - 1] == '\r') {
+            end = buf->buf + buf->used - r - 1;
+            end += 2;
+        }
+    }
+    if (!end) {
+        end = strstr(buf->buf + buf->used - r, "\r\n");
+        if (end)
+            end += 2;
+    }
+
+    while (end) {
+        libxl__json_object *o;
+        libxl__yajl_ctx *yajl_ctx;
+        libxl__qmp_rx_buf *parse_buf, *tbuf;
+
+        yajl_ctx = libxl__json_parse_alloc(gc);
+
+        LIBXL_TAILQ_FOREACH_SAFE(parse_buf, &qmp->bufs, entry, tbuf) {
+            size_t len;
+            char *s;
+
+            /* Start parsing from s */
+            s = parse_buf->buf + parse_buf->consumed;
+            /* Findout how much can be parsed */
+            if (buf == parse_buf) {
+                /* this is the last buffer to parse, stop at end */
+                len = end - parse_buf->buf - parse_buf->consumed;
+            } else {
+                /* parse all the buffer */
+                len = parse_buf->used - parse_buf->consumed;
+            }
+
+            LOG_QMP("parsing %luB: '%.*s'", len, (int)len, s);
+
+            rc = libxl__json_parse_partial(gc, yajl_ctx, s, len);
+            if (rc)
+                break;
+
+            parse_buf->consumed += len;
+
+            if (parse_buf->consumed >= parse_buf->used) {
+                LIBXL_TAILQ_REMOVE(&qmp->bufs, parse_buf, entry);
+                free(parse_buf);
+                if (buf == parse_buf) {
+                    buf = NULL;
+                    break;
+                }
+            }
+
+            /* Last buffer to parse, will call complete */
+            if (buf == parse_buf)
+                break;
+        }
+
+        if (rc)
+            return rc;
+
+        o = libxl__json_complete_parse(gc, yajl_ctx);
+
+        if (!o) {
+            LOGD(ERROR, qmp->domid, "Parse error");
+            return ERROR_FAIL;
+        }
+
+        LOG_QMP("JSON object received: %s", libxl__json_object_to_json(gc, o));
+
+        /* check if there is another message received at the same time */
+        if (buf) {
+            end = strstr(buf->buf + buf->consumed, "\r\n");
+            if (end)
+                end += 2;
+        } else
+            end = NULL;
+    }
     return 0;
 }
 
-- 
Anthony PERARD


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