keep unnamed sections unnamed on export

add some safety to altering unnamed sections by generating the name from a hash of its type and its option/value pairs

diff --git a/file.c b/file.c
index 4cb18d231fcd3d1d3b743b3b47c28f4f7e184f6d..c6ea7b485343923fda69324b2f124e308c4294aa 100644 (file)
--- a/file.c
+++ b/file.c
@@ -323,14 +323,60 @@ static void uci_parse_package(struct uci_context *ctx, char **str, bool single)
        uci_switch_config(ctx);
 }
 
+/* Based on an efficient hash function published by D. J. Bernstein */
+static unsigned int djbhash(unsigned int hash, char *str)
+{
+       int len = strlen(str);
+       int i;
+
+       /* initial value */
+       if (hash == ~0)
+               hash = 5381;
+
+       for(i = 0; i < len; i++) {
+               hash = ((hash << 5) + hash) + str[i];
+       }
+       return (hash & 0x7FFFFFFF);
+}
+
+/* fix up an unnamed section */
+static void uci_fixup_section(struct uci_context *ctx, struct uci_section *s)
+{
+       unsigned int hash = ~0;
+       struct uci_element *e;
+       char buf[16];
+
+       if (!s || s->e.name)
+               return;
+
+       /*
+        * Generate a name for unnamed sections. This is used as reference
+        * when locating or updating the section from apps/scripts.
+        * To make multiple concurrent versions somewhat safe for updating,
+        * the name is generated from a hash of its type and name/value
+        * pairs of its option, and it is prefixed by a counter value.
+        * If the order of the unnamed sections changes for some reason,
+        * updates to them will be rejected.
+        */
+       hash = djbhash(hash, s->type);
+       uci_foreach_element(&s->options, e) {
+               hash = djbhash(hash, e->name);
+               hash = djbhash(hash, uci_to_option(e)->value);
+       }
+       sprintf(buf, "cfg%02x%04x", ++s->package->n_section, hash % (1 << 16));
+       s->e.name = uci_strdup(ctx, buf);
+}
+
 /*
  * parse the 'config' uci command (open a section)
  */
 static void uci_parse_config(struct uci_context *ctx, char **str)
 {
+       struct uci_section *s;
        char *name = NULL;
        char *type = NULL;
 
+       uci_fixup_section(ctx, ctx->pctx->section);
        if (!ctx->pctx->package) {
                if (!ctx->pctx->name)
                        uci_parse_error(ctx, *str, "attempting to import a file without a package name");
@@ -458,7 +504,9 @@ static void uci_export_package(struct uci_package *p, FILE *stream, bool header)
        uci_foreach_element(&p->sections, s) {
                struct uci_section *sec = uci_to_section(s);
                fprintf(stream, "\nconfig '%s'", uci_escape(ctx, sec->type));
-               fprintf(stream, " '%s'\n", uci_escape(ctx, sec->e.name));
+               if (!sec->anonymous)
+                       fprintf(stream, " '%s'", uci_escape(ctx, sec->e.name));
+               fprintf(stream, "\n");
                uci_foreach_element(&sec->options, o) {
                        struct uci_option *opt = uci_to_option(o);
                        fprintf(stream, "\toption '%s'", uci_escape(ctx, opt->e.name));
@@ -520,6 +568,7 @@ error:
                        UCI_THROW(ctx, ctx->errno);
        }
 
+       uci_fixup_section(ctx, ctx->pctx->section);
        if (package)
                *package = pctx->package;
 

diff --git a/list.c b/list.c
index b644523bc5760c36e3a4cb8cdc11fc625dcf8153..5700605c2d63e727cd6afd6e5e500973e3be7948 100644 (file)
--- a/list.c
+++ b/list.c
@@ -113,18 +113,18 @@ uci_alloc_section(struct uci_package *p, const char *type, const char *name)
 {
        struct uci_context *ctx = p->ctx;
        struct uci_section *s;
-       char buf[16];
 
-       if (!name || !name[0]) {
-               snprintf(buf, 16, "cfg%d", p->n_section);
-               name = buf;
-       }
+       if (name && !name[0])
+               name = NULL;
 
        s = uci_alloc_element(ctx, section, name, strlen(type) + 1);
+       uci_list_init(&s->options);
        s->type = uci_dataptr(s);
        s->package = p;
        strcpy(s->type, type);
-       uci_list_init(&s->options);
+       if (name == NULL)
+               s->anonymous = true;
+
        uci_list_add(&p->sections, &s->e.list);
 
        return s;

diff --git a/uci.h b/uci.h
index 88b5833441b11f0e5f4d05aafdd7510528a4a438..1b6c9fa931bedd5ef10374ad7bb39a5a6f038cc8 100644 (file)
--- a/uci.h
+++ b/uci.h
@@ -290,6 +290,7 @@ struct uci_section
        struct uci_element e;
        struct uci_list options;
        struct uci_package *package;
+       bool anonymous;
        char *type;
 };