protobuf/upb/symtab.c

/*
 * upb - a minimalist implementation of protocol buffers.
 *
 * Copyright (c) 2008-2012 Google Inc.  See LICENSE for details.
 * Author: Josh Haberman <jhaberman@gmail.com>
 */

#include "upb/symtab.h"

#include <stdlib.h>
#include <string.h>

bool upb_symtab_isfrozen(const upb_symtab *s) {
  return upb_refcounted_isfrozen(UPB_UPCAST(s));
}

void upb_symtab_ref(const upb_symtab *s, const void *owner) {
  upb_refcounted_ref(UPB_UPCAST(s), owner);
}

void upb_symtab_unref(const upb_symtab *s, const void *owner) {
  upb_refcounted_unref(UPB_UPCAST(s), owner);
}

void upb_symtab_donateref(
    const upb_symtab *s, const void *from, const void *to) {
  upb_refcounted_donateref(UPB_UPCAST(s), from, to);
}

void upb_symtab_checkref(const upb_symtab *s, const void *owner) {
  upb_refcounted_checkref(UPB_UPCAST(s), owner);
}

static void upb_symtab_free(upb_refcounted *r) {
  upb_symtab *s = (upb_symtab*)r;
  upb_strtable_iter i;
  upb_strtable_begin(&i, &s->symtab);
  for (; !upb_strtable_done(&i); upb_strtable_next(&i)) {
    const upb_def *def = upb_value_getptr(upb_strtable_iter_value(&i));
    upb_def_unref(def, s);
  }
  upb_strtable_uninit(&s->symtab);
  free(s);
}

static const struct upb_refcounted_vtbl vtbl = {NULL, &upb_symtab_free};

upb_symtab *upb_symtab_new(const void *owner) {
  upb_symtab *s = malloc(sizeof(*s));
  upb_refcounted_init(UPB_UPCAST(s), &vtbl, owner);
  upb_strtable_init(&s->symtab, UPB_CTYPE_PTR);
  return s;
}

void upb_symtab_freeze(upb_symtab *s) {
  assert(!upb_symtab_isfrozen(s));
  upb_refcounted *r = UPB_UPCAST(s);
  // The symtab does not take ref2's (see refcounted.h) on the defs, because
  // defs cannot refer back to the table and therefore cannot create cycles.  So
  // 0 will suffice for maxdepth here.
  bool ok = upb_refcounted_freeze(&r, 1, NULL, 0);
  UPB_ASSERT_VAR(ok, ok);
}

const upb_def *upb_symtab_lookup(const upb_symtab *s, const char *sym) {
  upb_value v;
  upb_def *ret = upb_strtable_lookup(&s->symtab, sym, &v) ?
      upb_value_getptr(v) : NULL;
  return ret;
}

const upb_msgdef *upb_symtab_lookupmsg(const upb_symtab *s, const char *sym) {
  upb_value v;
  upb_def *def = upb_strtable_lookup(&s->symtab, sym, &v) ?
      upb_value_getptr(v) : NULL;
  return def ? upb_dyncast_msgdef(def) : NULL;
}

const upb_enumdef *upb_symtab_lookupenum(const upb_symtab *s, const char *sym) {
  upb_value v;
  upb_def *def = upb_strtable_lookup(&s->symtab, sym, &v) ?
      upb_value_getptr(v) : NULL;
  return def ? upb_dyncast_enumdef(def) : NULL;
}

// Given a symbol and the base symbol inside which it is defined, find the
// symbol's definition in t.
static upb_def *upb_resolvename(const upb_strtable *t,
                                const char *base, const char *sym) {
  if(strlen(sym) == 0) return NULL;
  if(sym[0] == '.') {
    // Symbols starting with '.' are absolute, so we do a single lookup.
    // Slice to omit the leading '.'
    upb_value v;
    return upb_strtable_lookup(t, sym + 1, &v) ? upb_value_getptr(v) : NULL;
  } else {
    // Remove components from base until we find an entry or run out.
    // TODO: This branch is totally broken, but currently not used.
    (void)base;
    assert(false);
    return NULL;
  }
}

const upb_def *upb_symtab_resolve(const upb_symtab *s, const char *base,
                                  const char *sym) {
  upb_def *ret = upb_resolvename(&s->symtab, base, sym);
  return ret;
}

// Searches def and its children to find defs that have the same name as any
// def in "addtab."  Returns true if any where found, and as a side-effect adds
// duplicates of these defs into addtab.
//
// We use a modified depth-first traversal that traverses each SCC (which we
// already computed) as if it were a single node.  This allows us to traverse
// the possibly-cyclic graph as if it were a DAG and to dup the correct set of
// nodes with O(n) time.
static bool upb_resolve_dfs(const upb_def *def, upb_strtable *addtab,
                            const void *new_owner, upb_inttable *seen,
                            upb_status *s) {
  // Memoize results of this function for efficiency (since we're traversing a
  // DAG this is not needed to limit the depth of the search).
  upb_value v;
  if (upb_inttable_lookup(seen, (uintptr_t)def, &v))
    return upb_value_getbool(v);

  // Visit submessages for all messages in the SCC.
  bool need_dup = false;
  const upb_def *base = def;
  do {
    assert(upb_def_isfrozen(def));
    if (def->type == UPB_DEF_FIELD) continue;
    upb_value v;
    if (upb_strtable_lookup(addtab, upb_def_fullname(def), &v)) {
      need_dup = true;
    }

    // For messages, continue the recursion by visiting all subdefs.
    const upb_msgdef *m = upb_dyncast_msgdef(def);
    if (m) {
      upb_msg_iter i;
      for(upb_msg_begin(&i, m); !upb_msg_done(&i); upb_msg_next(&i)) {
        upb_fielddef *f = upb_msg_iter_field(&i);
        if (!upb_fielddef_hassubdef(f)) continue;
        // |= to avoid short-circuit; we need its side-effects.
        need_dup |= upb_resolve_dfs(
            upb_fielddef_subdef(f), addtab, new_owner, seen, s);
        if (!upb_ok(s)) return false;
      }
    }
  } while ((def = (upb_def*)def->base.next) != base);

  if (need_dup) {
    // Dup any defs that don't already have entries in addtab.
    def = base;
    do {
      if (def->type == UPB_DEF_FIELD) continue;
      const char *name = upb_def_fullname(def);
      if (!upb_strtable_lookup(addtab, name, NULL)) {
        upb_def *newdef = upb_def_dup(def, new_owner);
        if (!newdef) goto oom;
        newdef->came_from_user = false;
        if (!upb_strtable_insert(addtab, name, upb_value_ptr(newdef)))
          goto oom;
      }
    } while ((def = (upb_def*)def->base.next) != base);
  }

  upb_inttable_insert(seen, (uintptr_t)def, upb_value_bool(need_dup));
  return need_dup;

oom:
  upb_status_seterrmsg(s, "out of memory");
  return false;
}

// TODO(haberman): we need a lot more testing of error conditions.
// The came_from_user stuff in particular is not tested.
bool upb_symtab_add(upb_symtab *s, upb_def *const*defs, int n, void *ref_donor,
                    upb_status *status) {
  assert(!upb_symtab_isfrozen(s));
  upb_def **add_defs = NULL;
  upb_strtable addtab;
  if (!upb_strtable_init(&addtab, UPB_CTYPE_PTR)) {
    upb_status_seterrmsg(status, "out of memory");
    return false;
  }

  // Add new defs to our "add" set.
  for (int i = 0; i < n; i++) {
    upb_def *def = defs[i];
    if (upb_def_isfrozen(def)) {
      upb_status_seterrmsg(status, "added defs must be mutable");
      goto err;
    }
    assert(!upb_def_isfrozen(def));
    const char *fullname = upb_def_fullname(def);
    if (!fullname) {
      upb_status_seterrmsg(
          status, "Anonymous defs cannot be added to a symtab");
      goto err;
    }

    upb_fielddef *f = upb_dyncast_fielddef_mutable(def);

    if (f) {
      if (!upb_fielddef_containingtypename(f)) {
        upb_status_seterrmsg(status,
                             "Standalone fielddefs must have a containing type "
                             "(extendee) name set");
        goto err;
      }
    } else {
      if (upb_strtable_lookup(&addtab, fullname, NULL)) {
        upb_status_seterrf(status, "Conflicting defs named '%s'", fullname);
        goto err;
      }
      // We need this to back out properly, because if there is a failure we
      // need to donate the ref back to the caller.
      def->came_from_user = true;
      upb_def_donateref(def, ref_donor, s);
      if (!upb_strtable_insert(&addtab, fullname, upb_value_ptr(def)))
        goto oom_err;
    }
  }

  // Add standalone fielddefs (ie. extensions) to the appropriate messages.
  // If the appropriate message only exists in the existing symtab, duplicate
  // it so we have a mutable copy we can add the fields to.
  for (int i = 0; i < n; i++) {
    upb_def *def = defs[i];
    upb_fielddef *f = upb_dyncast_fielddef_mutable(def);
    if (!f) continue;
    const char *msgname = upb_fielddef_containingtypename(f);
    // We validated this earlier in this function.
    assert(msgname);

    // If the extendee name is absolutely qualified, move past the initial ".".
    // TODO(haberman): it is not obvious what it would mean if this was not
    // absolutely qualified.
    if (msgname[0] == '.') {
      msgname++;
    }

    upb_value v;
    upb_msgdef *m;
    if (upb_strtable_lookup(&addtab, msgname, &v)) {
      // Extendee is in the set of defs the user asked us to add.
      m = upb_value_getptr(v);
    } else {
      // Need to find and dup the extendee from the existing symtab.
      const upb_msgdef *frozen_m = upb_symtab_lookupmsg(s, msgname);
      if (!frozen_m) {
        upb_status_seterrf(status,
                           "Tried to extend message %s that does not exist "
                           "in this SymbolTable.",
                           msgname);
        goto err;
      }
      m = upb_msgdef_dup(frozen_m, s);
      if (!m) goto oom_err;
      if (!upb_strtable_insert(&addtab, msgname, upb_value_ptr(m))) {
        upb_msgdef_unref(m, s);
        goto oom_err;
      }
    }

    if (!upb_msgdef_addfield(m, f, ref_donor, status)) {
      goto err;
    }
  }

  // Add dups of any existing def that can reach a def with the same name as
  // anything in our "add" set.
  upb_inttable seen;
  if (!upb_inttable_init(&seen, UPB_CTYPE_BOOL)) goto oom_err;
  upb_strtable_iter i;
  upb_strtable_begin(&i, &s->symtab);
  for (; !upb_strtable_done(&i); upb_strtable_next(&i)) {
    upb_def *def = upb_value_getptr(upb_strtable_iter_value(&i));
    upb_resolve_dfs(def, &addtab, s, &seen, status);
    if (!upb_ok(status)) goto err;
  }
  upb_inttable_uninit(&seen);

  // Now using the table, resolve symbolic references for subdefs.
  upb_strtable_begin(&i, &addtab);
  for (; !upb_strtable_done(&i); upb_strtable_next(&i)) {
    upb_def *def = upb_value_getptr(upb_strtable_iter_value(&i));
    upb_msgdef *m = upb_dyncast_msgdef_mutable(def);
    if (!m) continue;
    // Type names are resolved relative to the message in which they appear.
    const char *base = upb_msgdef_fullname(m);

    upb_msg_iter j;
    for(upb_msg_begin(&j, m); !upb_msg_done(&j); upb_msg_next(&j)) {
      upb_fielddef *f = upb_msg_iter_field(&j);
      const char *name = upb_fielddef_subdefname(f);
      if (name && !upb_fielddef_subdef(f)) {
        upb_def *subdef = upb_resolvename(&addtab, base, name);
        if (subdef == NULL) {
          upb_status_seterrf(
              status, "couldn't resolve name '%s' in message '%s'", name, base);
          goto err;
        } else if (!upb_fielddef_setsubdef(f, subdef, status)) {
          goto err;
        }
      }
    }
  }

  // We need an array of the defs in addtab, for passing to upb_def_freeze.
  add_defs = malloc(sizeof(void*) * upb_strtable_count(&addtab));
  if (add_defs == NULL) goto oom_err;
  upb_strtable_begin(&i, &addtab);
  for (n = 0; !upb_strtable_done(&i); upb_strtable_next(&i)) {
    add_defs[n++] = upb_value_getptr(upb_strtable_iter_value(&i));
  }

  if (!upb_def_freeze(add_defs, n, status)) goto err;

  // This must be delayed until all errors have been detected, since error
  // recovery code uses this table to cleanup defs.
  upb_strtable_uninit(&addtab);

  // TODO(haberman) we don't properly handle errors after this point (like
  // OOM in upb_strtable_insert() below).
  for (int i = 0; i < n; i++) {
    upb_def *def = add_defs[i];
    const char *name = upb_def_fullname(def);
    upb_value v;
    if (upb_strtable_remove(&s->symtab, name, &v)) {
      const upb_def *def = upb_value_getptr(v);
      upb_def_unref(def, s);
    }
    bool success = upb_strtable_insert(&s->symtab, name, upb_value_ptr(def));
    UPB_ASSERT_VAR(success, success == true);
  }
  free(add_defs);
  return true;

oom_err:
  upb_status_seterrmsg(status, "out of memory");
err: {
    // For defs the user passed in, we need to donate the refs back.  For defs
    // we dup'd, we need to just unref them.
    upb_strtable_iter i;
    upb_strtable_begin(&i, &addtab);
    for (; !upb_strtable_done(&i); upb_strtable_next(&i)) {
      upb_def *def = upb_value_getptr(upb_strtable_iter_value(&i));
      bool came_from_user = def->came_from_user;
      def->came_from_user = false;
      if (came_from_user) {
        upb_def_donateref(def, s, ref_donor);
      } else {
        upb_def_unref(def, s);
      }
    }
  }
  upb_strtable_uninit(&addtab);
  free(add_defs);
  assert(!upb_ok(status));
  return false;
}

// Iteration.

static void advance_to_matching(upb_symtab_iter *iter) {
  if (iter->type == UPB_DEF_ANY)
    return;

  while (!upb_strtable_done(&iter->iter) &&
         iter->type != upb_symtab_iter_def(iter)->type) {
    upb_strtable_next(&iter->iter);
  }
}

void upb_symtab_begin(upb_symtab_iter *iter, const upb_symtab *s,
                      upb_deftype_t type) {
  upb_strtable_begin(&iter->iter, &s->symtab);
  iter->type = type;
  advance_to_matching(iter);
}

void upb_symtab_next(upb_symtab_iter *iter) {
  upb_strtable_next(&iter->iter);
  advance_to_matching(iter);
}

bool upb_symtab_done(const upb_symtab_iter *iter) {
  return upb_strtable_done(&iter->iter);
}

const upb_def *upb_symtab_iter_def(const upb_symtab_iter *iter) {
  return upb_value_getptr(upb_strtable_iter_value(&iter->iter));
}