[Xen-devel] [PATCH v3 16/31] libxl_json: Allow partial parsing

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

This set of function allow to parse a JSON string that is spread accross
different memory location.

This is usefull when a JSON string is received from a remote process,
and in order to avoid using realloc, the message is recorded in multiple
buffers.

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 tools/libxl/libxl_internal.h |   6 +++
 tools/libxl/libxl_json.c     | 100 +++++++++++++++++++++++++++--------
 2 files changed, 84 insertions(+), 22 deletions(-)

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index d9eebfd98b..c87712c83a 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2039,6 +2039,12 @@ _hidden void libxl__json_object_free(libxl__gc *gc_opt,
                                      libxl__json_object *obj);
 
 _hidden libxl__json_object *libxl__json_parse(libxl__gc *gc_opt, const char 
*s);
+/* allow to parse a json string store in multiple buffers */
+_hidden libxl__yajl_ctx *libxl__json_parse_alloc(libxl__gc *gc);
+_hidden int libxl__json_parse_partial(libxl__gc *gc, libxl__yajl_ctx *yajl_ctx,
+                                      const char *s, size_t len);
+_hidden libxl__json_object *libxl__json_complete_parse(libxl__gc *gc,
+                                                   libxl__yajl_ctx *yajl_ctx);
 
   /* Based on /local/domain/$domid/dm-version xenstore key
    * default is qemu xen traditional */
diff --git a/tools/libxl/libxl_json.c b/tools/libxl/libxl_json.c
index b7f9077f0d..3727af34d8 100644
--- a/tools/libxl/libxl_json.c
+++ b/tools/libxl/libxl_json.c
@@ -912,47 +912,103 @@ static void yajl_ctx_free(libxl__yajl_ctx *yajl_ctx)
     DEBUG_GEN_FREE(yajl_ctx);
 }
 
-libxl__json_object *libxl__json_parse(libxl__gc *gc, const char *s)
+/*
+ * Only to use with:
+ * libxl__json_parse_partial
+ * libxl__json_complete_parse
+ *
+ * gc should be the same accross all functions.
+ * NOGC is not allowed unless called from libxl__json_parse()
+ */
+libxl__yajl_ctx *libxl__json_parse_alloc(libxl__gc *gc)
 {
-    yajl_status status;
-    libxl__yajl_ctx yajl_ctx;
-    libxl__json_object *o = NULL;
-    unsigned char *str = NULL;
+    libxl__yajl_ctx *yajl_ctx;
 
-    memset(&yajl_ctx, 0, sizeof (yajl_ctx));
-    yajl_ctx.gc = gc;
+    GCNEW(yajl_ctx);
 
-    DEBUG_GEN_ALLOC(&yajl_ctx);
+    yajl_ctx->gc = gc;
 
-    if (yajl_ctx.hand == NULL) {
-        yajl_ctx.hand = libxl__yajl_alloc(&callbacks, NULL, &yajl_ctx);
-    }
-    status = yajl_parse(yajl_ctx.hand, (const unsigned char *)s, strlen(s));
+    DEBUG_GEN_ALLOC(yajl_ctx);
+
+    yajl_ctx->hand = libxl__yajl_alloc(&callbacks, NULL, yajl_ctx);
+
+    return yajl_ctx;
+}
+
+static void json_parse_error(libxl__gc *gc, libxl__yajl_ctx *yajl_ctx,
+                             const char *s, size_t len)
+{
+    unsigned char *str;
+    str = yajl_get_error(yajl_ctx->hand, 1, (const unsigned char*)s, len);
+    LOGE(ERROR, "yajl error: %s", str);
+    yajl_free_error(yajl_ctx->hand, str);
+    yajl_ctx_free(yajl_ctx);
+}
+
+int libxl__json_parse_partial(libxl__gc *gc, libxl__yajl_ctx *yajl_ctx,
+                              const char *s, size_t len)
+{
+    yajl_status status;
+
+    assert(gc == yajl_ctx->gc);
+
+    status = yajl_parse(yajl_ctx->hand, (const unsigned char *)s, strlen(s));
     if (status != yajl_status_ok)
         goto out;
 
-    status = yajl_complete_parse(yajl_ctx.hand);
+    return 0;
+
+out:
+    json_parse_error(gc, yajl_ctx, s, len);
+    return ERROR_FAIL;
+}
+
+libxl__json_object *libxl__json_complete_parse(libxl__gc *gc,
+                                               libxl__yajl_ctx *yajl_ctx)
+{
+    yajl_status status;
+    libxl__json_object *o;
+
+    assert(gc == yajl_ctx->gc);
+
+    status = yajl_complete_parse(yajl_ctx->hand);
     if (status != yajl_status_ok)
         goto out;
 
-    o = yajl_ctx.head;
+    o = yajl_ctx->head;
 
-    DEBUG_GEN_REPORT(&yajl_ctx);
+    DEBUG_GEN_REPORT(yajl_ctx);
 
-    yajl_ctx.head = NULL;
+    yajl_ctx->head = NULL;
 
-    yajl_ctx_free(&yajl_ctx);
+    yajl_ctx_free(yajl_ctx);
     return o;
 
 out:
-    str = yajl_get_error(yajl_ctx.hand, 1, (const unsigned char*)s, strlen(s));
-
-    LIBXL__LOG(libxl__gc_owner(gc), LIBXL__LOG_ERROR, "yajl error: %s", str);
-    yajl_free_error(yajl_ctx.hand, str);
-    yajl_ctx_free(&yajl_ctx);
+    json_parse_error(gc, yajl_ctx, NULL, 0);
     return NULL;
 }
 
+libxl__json_object *libxl__json_parse(libxl__gc *gc, const char *s)
+{
+    libxl__yajl_ctx *yajl_ctx;
+    int rc;
+    libxl__json_object *o = NULL;
+
+    yajl_ctx = libxl__json_parse_alloc(gc);
+
+    rc = libxl__json_parse_partial(gc, yajl_ctx, s, strlen(s));
+    if (rc)
+        goto out;
+
+    o = libxl__json_complete_parse(gc, yajl_ctx);
+
+out:
+    if (!libxl__gc_is_real(gc))
+        free(yajl_ctx);
+    return o;
+}
+
 static const char *yajl_gen_status_to_string(yajl_gen_status s)
 {
         switch (s) {
-- 
Anthony PERARD


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