libc/system_properties/prop_area.cpp - platform/bionic - Git at Google

 /*
  * Copyright (C) 2008 The Android Open Source Project
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *  * Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *  * Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in
  *    the documentation and/or other materials provided with the
  *    distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */

 #include "system_properties/prop_area.h"

 #include <errno.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <sys/cdefs.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/xattr.h>
 #include <unistd.h>

 #include <new>

 #include <async_safe/log.h>

 constexpr size_t PA_SIZE = 128 * 1024;
 constexpr uint32_t PROP_AREA_MAGIC = 0x504f5250;
 constexpr uint32_t PROP_AREA_VERSION = 0xfc6ed0ab;

 size_t prop_area::pa_size_ = 0;
 size_t prop_area::pa_data_size_ = 0;

 prop_area* prop_area::map_prop_area_rw(const char* filename, const char* context,
                                        bool* fsetxattr_failed) {
   /* dev is a tmpfs that we can use to carve a shared workspace
    * out of, so let's do that...
    */
   const int fd = open(filename, O_RDWR | O_CREAT | O_NOFOLLOW | O_CLOEXEC | O_EXCL, 0444);

   if (fd < 0) {
     if (errno == EACCES) {
       /* for consistency with the case where the process has already
        * mapped the page in and segfaults when trying to write to it
        */
       abort();
     }
     return nullptr;
   }

   if (context) {
     if (fsetxattr(fd, XATTR_NAME_SELINUX, context, strlen(context) + 1, 0) != 0) {
       async_safe_format_log(ANDROID_LOG_ERROR, "libc",
                             "fsetxattr failed to set context (%s) for \"%s\"", context, filename);
       /*
        * fsetxattr() will fail during system properties tests due to selinux policy.
        * We do not want to create a custom policy for the tester, so we will continue in
        * this function but set a flag that an error has occurred.
        * Init, which is the only daemon that should ever call this function will abort
        * when this error occurs.
        * Otherwise, the tester will ignore it and continue, albeit without any selinux
        * property separation.
        */
       if (fsetxattr_failed) {
         *fsetxattr_failed = true;
       }
     }
   }

   if (ftruncate(fd, PA_SIZE) < 0) {
     close(fd);
     return nullptr;
   }

   pa_size_ = PA_SIZE;
   pa_data_size_ = pa_size_ - sizeof(prop_area);

   void* const memory_area = mmap(nullptr, pa_size_, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
   if (memory_area == MAP_FAILED) {
     close(fd);
     return nullptr;
   }

   prop_area* pa = new (memory_area) prop_area(PROP_AREA_MAGIC, PROP_AREA_VERSION);

   close(fd);
   return pa;
 }

 prop_area* prop_area::map_fd_ro(const int fd) {
   struct stat fd_stat;
   if (fstat(fd, &fd_stat) < 0) {
     return nullptr;
   }

   if ((fd_stat.st_uid != 0) || (fd_stat.st_gid != 0) ||
       ((fd_stat.st_mode & (S_IWGRP | S_IWOTH)) != 0) ||
       (fd_stat.st_size < static_cast<off_t>(sizeof(prop_area)))) {
     return nullptr;
   }

   pa_size_ = fd_stat.st_size;
   pa_data_size_ = pa_size_ - sizeof(prop_area);

   void* const map_result = mmap(nullptr, pa_size_, PROT_READ, MAP_SHARED, fd, 0);
   if (map_result == MAP_FAILED) {
     return nullptr;
   }

   prop_area* pa = reinterpret_cast<prop_area*>(map_result);
   if ((pa->magic() != PROP_AREA_MAGIC) || (pa->version() != PROP_AREA_VERSION)) {
     munmap(pa, pa_size_);
     return nullptr;
   }

   return pa;
 }

 prop_area* prop_area::map_prop_area(const char* filename) {
   int fd = open(filename, O_CLOEXEC | O_NOFOLLOW | O_RDONLY);
   if (fd == -1) return nullptr;

   prop_area* map_result = map_fd_ro(fd);
   close(fd);

   return map_result;
 }

 void* prop_area::allocate_obj(const size_t size, uint_least32_t* const off) {
   const size_t aligned = __BIONIC_ALIGN(size, sizeof(uint_least32_t));
   if (bytes_used_ + aligned > pa_data_size_) {
     return nullptr;
   }

   *off = bytes_used_;
   bytes_used_ += aligned;
   return data_ + *off;
 }

 prop_trie_node* prop_area::new_prop_trie_node(const char* name, uint32_t namelen,
                                               uint_least32_t* const off) {
   uint_least32_t new_offset;
   void* const p = allocate_obj(sizeof(prop_trie_node) + namelen + 1, &new_offset);
   if (p == nullptr) return nullptr;

   prop_trie_node* node = new (p) prop_trie_node(name, namelen);
   *off = new_offset;
   return node;
 }

 prop_info* prop_area::new_prop_info(const char* name, uint32_t namelen, const char* value,
                                     uint32_t valuelen, uint_least32_t* const off) {
   uint_least32_t new_offset;
   void* const p = allocate_obj(sizeof(prop_info) + namelen + 1, &new_offset);
   if (p == nullptr) return nullptr;

   prop_info* info;
   if (valuelen >= PROP_VALUE_MAX) {
     uint32_t long_value_offset = 0;
     char* long_location = reinterpret_cast<char*>(allocate_obj(valuelen + 1, &long_value_offset));
     if (!long_location) return nullptr;

     memcpy(long_location, value, valuelen);
     long_location[valuelen] = '\0';

     // Both new_offset and long_value_offset are offsets based off of data_, however prop_info
     // does not know what data_ is, so we change this offset to be an offset from the prop_info
     // pointer that contains it.
     long_value_offset -= new_offset;

     info = new (p) prop_info(name, namelen, long_value_offset);
   } else {
     info = new (p) prop_info(name, namelen, value, valuelen);
   }
   *off = new_offset;
   return info;
 }

 void* prop_area::to_prop_obj(uint_least32_t off) {
   if (off > pa_data_size_) return nullptr;

   return (data_ + off);
 }

 inline prop_trie_node* prop_area::to_prop_trie_node(atomic_uint_least32_t* off_p) {
   uint_least32_t off = atomic_load_explicit(off_p, memory_order_consume);
   return reinterpret_cast<prop_trie_node*>(to_prop_obj(off));
 }

 inline prop_info* prop_area::to_prop_info(atomic_uint_least32_t* off_p) {
   uint_least32_t off = atomic_load_explicit(off_p, memory_order_consume);
   return reinterpret_cast<prop_info*>(to_prop_obj(off));
 }

 inline prop_trie_node* prop_area::root_node() {
   return reinterpret_cast<prop_trie_node*>(to_prop_obj(0));
 }

 static int cmp_prop_name(const char* one, uint32_t one_len, const char* two, uint32_t two_len) {
   if (one_len < two_len)
     return -1;
   else if (one_len > two_len)
     return 1;
   else
     return strncmp(one, two, one_len);
 }

 prop_trie_node* prop_area::find_prop_trie_node(prop_trie_node* const trie, const char* name,
                                                uint32_t namelen, bool alloc_if_needed) {
   prop_trie_node* current = trie;
   while (true) {
     if (!current) {
       return nullptr;
     }

     const int ret = cmp_prop_name(name, namelen, current->name, current->namelen);
     if (ret == 0) {
       return current;
     }

     if (ret < 0) {
       uint_least32_t left_offset = atomic_load_explicit(&current->left, memory_order_relaxed);
       if (left_offset != 0) {
         current = to_prop_trie_node(&current->left);
       } else {
         if (!alloc_if_needed) {
           return nullptr;
         }

         uint_least32_t new_offset;
         prop_trie_node* new_node = new_prop_trie_node(name, namelen, &new_offset);
         if (new_node) {
           atomic_store_explicit(&current->left, new_offset, memory_order_release);
         }
         return new_node;
       }
     } else {
       uint_least32_t right_offset = atomic_load_explicit(&current->right, memory_order_relaxed);
       if (right_offset != 0) {
         current = to_prop_trie_node(&current->right);
       } else {
         if (!alloc_if_needed) {
           return nullptr;
         }

         uint_least32_t new_offset;
         prop_trie_node* new_node = new_prop_trie_node(name, namelen, &new_offset);
         if (new_node) {
           atomic_store_explicit(&current->right, new_offset, memory_order_release);
         }
         return new_node;
       }
     }
   }
 }

 const prop_info* prop_area::find_property(prop_trie_node* const trie, const char* name,
                                           uint32_t namelen, const char* value, uint32_t valuelen,
                                           bool alloc_if_needed) {
   if (!trie) return nullptr;

   const char* remaining_name = name;
   prop_trie_node* current = trie;
   while (true) {
     const char* sep = strchr(remaining_name, '.');
     const bool want_subtree = (sep != nullptr);
     const uint32_t substr_size = (want_subtree) ? sep - remaining_name : strlen(remaining_name);

     if (!substr_size) {
       return nullptr;
     }

     prop_trie_node* root = nullptr;
     uint_least32_t children_offset = atomic_load_explicit(&current->children, memory_order_relaxed);
     if (children_offset != 0) {
       root = to_prop_trie_node(&current->children);
     } else if (alloc_if_needed) {
       uint_least32_t new_offset;
       root = new_prop_trie_node(remaining_name, substr_size, &new_offset);
       if (root) {
         atomic_store_explicit(&current->children, new_offset, memory_order_release);
       }
     }

     if (!root) {
       return nullptr;
     }

     current = find_prop_trie_node(root, remaining_name, substr_size, alloc_if_needed);
     if (!current) {
       return nullptr;
     }

     if (!want_subtree) break;

     remaining_name = sep + 1;
   }

   uint_least32_t prop_offset = atomic_load_explicit(&current->prop, memory_order_relaxed);
   if (prop_offset != 0) {
     return to_prop_info(&current->prop);
   } else if (alloc_if_needed) {
     uint_least32_t new_offset;
     prop_info* new_info = new_prop_info(name, namelen, value, valuelen, &new_offset);
     if (new_info) {
       atomic_store_explicit(&current->prop, new_offset, memory_order_release);
     }

     return new_info;
   } else {
     return nullptr;
   }
 }

 bool prop_area::foreach_property(prop_trie_node* const trie,
                                  void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
   if (!trie) return false;

   uint_least32_t left_offset = atomic_load_explicit(&trie->left, memory_order_relaxed);
   if (left_offset != 0) {
     const int err = foreach_property(to_prop_trie_node(&trie->left), propfn, cookie);
     if (err < 0) return false;
   }
   uint_least32_t prop_offset = atomic_load_explicit(&trie->prop, memory_order_relaxed);
   if (prop_offset != 0) {
     prop_info* info = to_prop_info(&trie->prop);
     if (!info) return false;
     propfn(info, cookie);
   }
   uint_least32_t children_offset = atomic_load_explicit(&trie->children, memory_order_relaxed);
   if (children_offset != 0) {
     const int err = foreach_property(to_prop_trie_node(&trie->children), propfn, cookie);
     if (err < 0) return false;
   }
   uint_least32_t right_offset = atomic_load_explicit(&trie->right, memory_order_relaxed);
   if (right_offset != 0) {
     const int err = foreach_property(to_prop_trie_node(&trie->right), propfn, cookie);
     if (err < 0) return false;
   }

   return true;
 }

 const prop_info* prop_area::find(const char* name) {
   return find_property(root_node(), name, strlen(name), nullptr, 0, false);
 }

 bool prop_area::add(const char* name, unsigned int namelen, const char* value,
                     unsigned int valuelen) {
   return find_property(root_node(), name, namelen, value, valuelen, true);
 }

 bool prop_area::foreach (void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
   return foreach_property(root_node(), propfn, cookie);
 }
	/*
	* Copyright (C) 2008 The Android Open Source Project
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in
	* the documentation and/or other materials provided with the
	* distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
	* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
	* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
	* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
	* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
	* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*/

	#include "system_properties/prop_area.h"

	#include <errno.h>
	#include <fcntl.h>
	#include <stdlib.h>
	#include <sys/cdefs.h>
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <sys/xattr.h>
	#include <unistd.h>

	#include <new>

	#include <async_safe/log.h>

	constexpr size_t PA_SIZE = 128 * 1024;
	constexpr uint32_t PROP_AREA_MAGIC = 0x504f5250;
	constexpr uint32_t PROP_AREA_VERSION = 0xfc6ed0ab;

	size_t prop_area::pa_size_ = 0;
	size_t prop_area::pa_data_size_ = 0;

	prop_area* prop_area::map_prop_area_rw(const char* filename, const char* context,
	bool* fsetxattr_failed) {
	/* dev is a tmpfs that we can use to carve a shared workspace
	* out of, so let's do that...
	*/
	const int fd = open(filename, O_RDWR \| O_CREAT \| O_NOFOLLOW \| O_CLOEXEC \| O_EXCL, 0444);

	if (fd < 0) {
	if (errno == EACCES) {
	/* for consistency with the case where the process has already
	* mapped the page in and segfaults when trying to write to it
	*/
	abort();
	}
	return nullptr;
	}

	if (context) {
	if (fsetxattr(fd, XATTR_NAME_SELINUX, context, strlen(context) + 1, 0) != 0) {
	async_safe_format_log(ANDROID_LOG_ERROR, "libc",
	"fsetxattr failed to set context (%s) for \"%s\"", context, filename);
	/*
	* fsetxattr() will fail during system properties tests due to selinux policy.
	* We do not want to create a custom policy for the tester, so we will continue in
	* this function but set a flag that an error has occurred.
	* Init, which is the only daemon that should ever call this function will abort
	* when this error occurs.
	* Otherwise, the tester will ignore it and continue, albeit without any selinux
	* property separation.
	*/
	if (fsetxattr_failed) {
	*fsetxattr_failed = true;
	}
	}
	}

	if (ftruncate(fd, PA_SIZE) < 0) {
	close(fd);
	return nullptr;
	}

	pa_size_ = PA_SIZE;
	pa_data_size_ = pa_size_ - sizeof(prop_area);

	void* const memory_area = mmap(nullptr, pa_size_, PROT_READ \| PROT_WRITE, MAP_SHARED, fd, 0);
	if (memory_area == MAP_FAILED) {
	close(fd);
	return nullptr;
	}

	prop_area* pa = new (memory_area) prop_area(PROP_AREA_MAGIC, PROP_AREA_VERSION);

	close(fd);
	return pa;
	}

	prop_area* prop_area::map_fd_ro(const int fd) {
	struct stat fd_stat;
	if (fstat(fd, &fd_stat) < 0) {
	return nullptr;
	}

	if ((fd_stat.st_uid != 0) \|\| (fd_stat.st_gid != 0) \|\|
	((fd_stat.st_mode & (S_IWGRP \| S_IWOTH)) != 0) \|\|
	(fd_stat.st_size < static_cast<off_t>(sizeof(prop_area)))) {
	return nullptr;
	}

	pa_size_ = fd_stat.st_size;
	pa_data_size_ = pa_size_ - sizeof(prop_area);

	void* const map_result = mmap(nullptr, pa_size_, PROT_READ, MAP_SHARED, fd, 0);
	if (map_result == MAP_FAILED) {
	return nullptr;
	}

	prop_area* pa = reinterpret_cast<prop_area*>(map_result);
	if ((pa->magic() != PROP_AREA_MAGIC) \|\| (pa->version() != PROP_AREA_VERSION)) {
	munmap(pa, pa_size_);
	return nullptr;
	}

	return pa;
	}

	prop_area* prop_area::map_prop_area(const char* filename) {
	int fd = open(filename, O_CLOEXEC \| O_NOFOLLOW \| O_RDONLY);
	if (fd == -1) return nullptr;

	prop_area* map_result = map_fd_ro(fd);
	close(fd);

	return map_result;
	}

	void* prop_area::allocate_obj(const size_t size, uint_least32_t* const off) {
	const size_t aligned = __BIONIC_ALIGN(size, sizeof(uint_least32_t));
	if (bytes_used_ + aligned > pa_data_size_) {
	return nullptr;
	}

	*off = bytes_used_;
	bytes_used_ += aligned;
	return data_ + *off;
	}

	prop_trie_node* prop_area::new_prop_trie_node(const char* name, uint32_t namelen,
	uint_least32_t* const off) {
	uint_least32_t new_offset;
	void* const p = allocate_obj(sizeof(prop_trie_node) + namelen + 1, &new_offset);
	if (p == nullptr) return nullptr;

	prop_trie_node* node = new (p) prop_trie_node(name, namelen);
	*off = new_offset;
	return node;
	}

	prop_info* prop_area::new_prop_info(const char* name, uint32_t namelen, const char* value,
	uint32_t valuelen, uint_least32_t* const off) {
	uint_least32_t new_offset;
	void* const p = allocate_obj(sizeof(prop_info) + namelen + 1, &new_offset);
	if (p == nullptr) return nullptr;

	prop_info* info;
	if (valuelen >= PROP_VALUE_MAX) {
	uint32_t long_value_offset = 0;
	char* long_location = reinterpret_cast<char*>(allocate_obj(valuelen + 1, &long_value_offset));
	if (!long_location) return nullptr;

	memcpy(long_location, value, valuelen);
	long_location[valuelen] = '\0';

	// Both new_offset and long_value_offset are offsets based off of data_, however prop_info
	// does not know what data_ is, so we change this offset to be an offset from the prop_info
	// pointer that contains it.
	long_value_offset -= new_offset;

	info = new (p) prop_info(name, namelen, long_value_offset);
	} else {
	info = new (p) prop_info(name, namelen, value, valuelen);
	}
	*off = new_offset;
	return info;
	}

	void* prop_area::to_prop_obj(uint_least32_t off) {
	if (off > pa_data_size_) return nullptr;

	return (data_ + off);
	}

	inline prop_trie_node* prop_area::to_prop_trie_node(atomic_uint_least32_t* off_p) {
	uint_least32_t off = atomic_load_explicit(off_p, memory_order_consume);
	return reinterpret_cast<prop_trie_node*>(to_prop_obj(off));
	}

	inline prop_info* prop_area::to_prop_info(atomic_uint_least32_t* off_p) {
	uint_least32_t off = atomic_load_explicit(off_p, memory_order_consume);
	return reinterpret_cast<prop_info*>(to_prop_obj(off));
	}

	inline prop_trie_node* prop_area::root_node() {
	return reinterpret_cast<prop_trie_node*>(to_prop_obj(0));
	}

	static int cmp_prop_name(const char* one, uint32_t one_len, const char* two, uint32_t two_len) {
	if (one_len < two_len)
	return -1;
	else if (one_len > two_len)
	return 1;
	else
	return strncmp(one, two, one_len);
	}

	prop_trie_node* prop_area::find_prop_trie_node(prop_trie_node* const trie, const char* name,
	uint32_t namelen, bool alloc_if_needed) {
	prop_trie_node* current = trie;
	while (true) {
	if (!current) {
	return nullptr;
	}

	const int ret = cmp_prop_name(name, namelen, current->name, current->namelen);
	if (ret == 0) {
	return current;
	}

	if (ret < 0) {
	uint_least32_t left_offset = atomic_load_explicit(&current->left, memory_order_relaxed);
	if (left_offset != 0) {
	current = to_prop_trie_node(&current->left);
	} else {
	if (!alloc_if_needed) {
	return nullptr;
	}

	uint_least32_t new_offset;
	prop_trie_node* new_node = new_prop_trie_node(name, namelen, &new_offset);
	if (new_node) {
	atomic_store_explicit(&current->left, new_offset, memory_order_release);
	}
	return new_node;
	}
	} else {
	uint_least32_t right_offset = atomic_load_explicit(&current->right, memory_order_relaxed);
	if (right_offset != 0) {
	current = to_prop_trie_node(&current->right);
	} else {
	if (!alloc_if_needed) {
	return nullptr;
	}

	uint_least32_t new_offset;
	prop_trie_node* new_node = new_prop_trie_node(name, namelen, &new_offset);
	if (new_node) {
	atomic_store_explicit(&current->right, new_offset, memory_order_release);
	}
	return new_node;
	}
	}
	}
	}

	const prop_info* prop_area::find_property(prop_trie_node* const trie, const char* name,
	uint32_t namelen, const char* value, uint32_t valuelen,
	bool alloc_if_needed) {
	if (!trie) return nullptr;

	const char* remaining_name = name;
	prop_trie_node* current = trie;
	while (true) {
	const char* sep = strchr(remaining_name, '.');
	const bool want_subtree = (sep != nullptr);
	const uint32_t substr_size = (want_subtree) ? sep - remaining_name : strlen(remaining_name);

	if (!substr_size) {
	return nullptr;
	}

	prop_trie_node* root = nullptr;
	uint_least32_t children_offset = atomic_load_explicit(&current->children, memory_order_relaxed);
	if (children_offset != 0) {
	root = to_prop_trie_node(&current->children);
	} else if (alloc_if_needed) {
	uint_least32_t new_offset;
	root = new_prop_trie_node(remaining_name, substr_size, &new_offset);
	if (root) {
	atomic_store_explicit(&current->children, new_offset, memory_order_release);
	}
	}

	if (!root) {
	return nullptr;
	}

	current = find_prop_trie_node(root, remaining_name, substr_size, alloc_if_needed);
	if (!current) {
	return nullptr;
	}

	if (!want_subtree) break;

	remaining_name = sep + 1;
	}

	uint_least32_t prop_offset = atomic_load_explicit(&current->prop, memory_order_relaxed);
	if (prop_offset != 0) {
	return to_prop_info(&current->prop);
	} else if (alloc_if_needed) {
	uint_least32_t new_offset;
	prop_info* new_info = new_prop_info(name, namelen, value, valuelen, &new_offset);
	if (new_info) {
	atomic_store_explicit(&current->prop, new_offset, memory_order_release);
	}

	return new_info;
	} else {
	return nullptr;
	}
	}

	bool prop_area::foreach_property(prop_trie_node* const trie,
	void (propfn)(const prop_info pi, void* cookie), void* cookie) {
	if (!trie) return false;

	uint_least32_t left_offset = atomic_load_explicit(&trie->left, memory_order_relaxed);
	if (left_offset != 0) {
	const int err = foreach_property(to_prop_trie_node(&trie->left), propfn, cookie);
	if (err < 0) return false;
	}
	uint_least32_t prop_offset = atomic_load_explicit(&trie->prop, memory_order_relaxed);
	if (prop_offset != 0) {
	prop_info* info = to_prop_info(&trie->prop);
	if (!info) return false;
	propfn(info, cookie);
	}
	uint_least32_t children_offset = atomic_load_explicit(&trie->children, memory_order_relaxed);
	if (children_offset != 0) {
	const int err = foreach_property(to_prop_trie_node(&trie->children), propfn, cookie);
	if (err < 0) return false;
	}
	uint_least32_t right_offset = atomic_load_explicit(&trie->right, memory_order_relaxed);
	if (right_offset != 0) {
	const int err = foreach_property(to_prop_trie_node(&trie->right), propfn, cookie);
	if (err < 0) return false;
	}

	return true;
	}

	const prop_info* prop_area::find(const char* name) {
	return find_property(root_node(), name, strlen(name), nullptr, 0, false);
	}

	bool prop_area::add(const char* name, unsigned int namelen, const char* value,
	unsigned int valuelen) {
	return find_property(root_node(), name, namelen, value, valuelen, true);
	}

	bool prop_area::foreach (void (propfn)(const prop_info pi, void* cookie), void* cookie) {
	return foreach_property(root_node(), propfn, cookie);
	}