1 files changed, 77 insertions, 0 deletions
diff --git a/upb_context.c b/upb_context.c
new file mode 100644
index 0000000..6797cbc
--- /dev/null
+++ b/upb_context.c
@@ -0,0 +1,77 @@
+/*
+ * upb - a minimalist implementation of protocol buffers.
+ *
+ * Copyright (c) 2009 Joshua Haberman.  See LICENSE for details.
+ */
+
+#include <assert.h>
+#include <string.h>
+#include "descriptor.h"
+#include "upb_context.h"
+
+int memrchr(char *data, char c, size_t len)
+{
+  int off = len-1;
+  while(off > 0 && data[off] != c) --off;
+  return off;
+}
+
+void upb_context_init(struct upb_context *c)
+{
+  upb_strtable_init(&c->symtab, 16, sizeof(struct upb_symtab_entry));
+  /* Add all the types in descriptor.proto so we can parse descriptors. */
+  if(!upb_context_addfd(c, &google_protobuf_filedescriptor, UPB_ONREDEF_ERROR))
+    assert(false);
+}
+
+void upb_context_free(struct upb_context *c)
+{
+  upb_strtable_free(&c->symtab);
+}
+
+struct upb_symtab_entry *upb_context_lookup(struct upb_context *c,
+                                            struct upb_string *symbol)
+{
+  return upb_strtable_lookup(&c->symtab, symbol);
+}
+
+struct upb_symtab_entry *upb_context_resolve(struct upb_context *c,
+                                             struct upb_string *base,
+                                             struct upb_string *symbol)
+{
+  if(base->byte_len + symbol->byte_len + 1 >= UPB_SYM_MAX_LENGTH ||
+     symbol->byte_len == 0) return NULL;
+
+  if(symbol->data[0] == UPB_CONTEXT_SEPARATOR) {
+    /* Symbols starting with '.' are absolute, so we do a single lookup. */
+    struct upb_string sym_str = {.data = symbol->data+1,
+                                 .byte_len = symbol->byte_len-1};
+    return upb_context_lookup(c, &sym_str);
+  } else {
+    /* Remove components from base until we find an entry or run out. */
+    char sym[UPB_SYM_MAX_LENGTH+1];
+    struct upb_string sym_str = {.data = sym};
+    int baselen = base->byte_len;
+    while(1) {
+      /* sym_str = base[0...base_len] + UPB_CONTEXT_SEPARATOR + symbol */
+      memcpy(sym, base->data, baselen);
+      sym[baselen] = UPB_CONTEXT_SEPARATOR;
+      memcpy(sym + baselen + 1, symbol->data, symbol->byte_len);
+      sym_str.byte_len = baselen + symbol->byte_len + 1;
+
+      struct upb_symtab_entry *e = upb_context_lookup(c, &sym_str);
+      if (e) return e;
+      else if(baselen == 0) return NULL;  /* No more scopes to try. */
+
+      baselen = memrchr(base->data, UPB_CONTEXT_SEPARATOR, baselen);
+    }
+  }
+}
+
+bool upb_context_addfd(struct upb_context *c,
+                       google_protobuf_FileDescriptorProto *fd,
+                       int onredef)
+{
+  /* TODO */
+  return true;
+}