add memory-pool based string field management for structures

convert chan_sip sip_pvt and sip_registry structures to use string fields
add 'const' qualifiers to a few API calls that don't modify their input strings
add an asprintf() wrapper to astmm


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@7797 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 288 insertions, 0 deletions

diff --git a/include/asterisk/stringfields.h b/include/asterisk/stringfields.h
new file mode 100644
index 000000000..02811a611
--- /dev/null
+++ b/include/asterisk/stringfields.h
@@ -0,0 +1,288 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2006, Digium, Inc.
+ *
+ * Kevin P. Fleming <kpfleming@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*! \file
+  \brief String fields in structures
+
+  This file contains objects and macros used to manage string
+  fields in structures without requiring them to be allocated
+  as fixed-size buffers or requiring individual allocations for
+  for each field.
+  
+  Using this functionality is quite simple... an example structure
+  with three fields is defined like this:
+  
+  \code
+  struct sample_fields {
+	  int x1;
+	  AST_DECLARE_STRING_FIELDS(
+		  AST_STRING_FIELD(name);
+		  AST_STRING_FIELD(address);
+		  AST_STRING_FIELD(password);
+	  );
+	  long x2;
+  };
+  \endcode
+  
+  When an instance of this structure is allocated, the fields
+  (and the pool of storage for them) must be initialized:
+  
+  \code
+  struct sample_fields *sample;
+  
+  sample = calloc(1, sizeof(*sample));
+  if (sample) {
+	  if (!ast_string_field_init(sample)) {
+		  free(sample);
+		  sample = NULL;
+	  }
+  }
+  
+  if (!sample) {
+  ...
+  }
+  \endcode
+  
+  Fields will default to pointing to an empty string, and will
+  revert to that when ast_string_field_free() is called. This means
+  that a string field will \b never contain NULL.
+  
+  Using the fields is much like using regular 'char *' fields
+  in the structure, except that writing into them must be done
+  using wrapper macros defined in this file.
+  
+  Storing simple values into fields can be done using ast_string_field_set();
+  more complex values (using printf-style format strings) can be stored
+  using ast_string_field_build().
+  
+  When the structure instance is no longer needed, the fields
+  and their storage pool must be freed:
+  
+  \code
+  ast_string_field_free_all(sample);
+  free(sample);
+  \endcode
+*/
+
+#ifndef _ASTERISK_STRINGFIELDS_H
+#define _ASTERISK_STRINGFIELDS_H
+
+#include <string.h>
+#include <stdarg.h>
+#include <stddef.h>
+
+#include "asterisk/inline_api.h"
+#include "asterisk/compiler.h"
+#include "asterisk/compat.h"
+
+/*!
+  \internal
+  \brief An opaque type for managed string fields in structures
+
+  Don't declare instances of this type directly; use the AST_STRING_FIELD()
+  macro instead.
+*/
+typedef const char * ast_string_field;
+
+/*!
+  \internal
+  \brief A constant empty string used for fields that have no other value
+*/
+extern const char *__ast_string_field_empty;
+
+/*!
+  \internal
+  \brief Structure used to manage the storage for a field pool
+*/
+struct ast_string_field_pool {
+	char *base;	/*!< the address of the pool's base in memory */
+	size_t size;	/*!< the total size of the pool */
+	size_t space;	/*!< the space available in the pool */
+	size_t used;	/*!< the space used in the pool */
+};
+
+/*!
+  \internal
+  \brief Initialize a field pool and fields
+  \param pool Pointer to the pool structure
+  \param size Amount of storage to allocate
+  \param fields Pointer to the first entry of the field array
+  \param num_fields Number of fields in the array
+  \return 0 on failure, non-zero on success
+*/
+int __ast_string_field_init(struct ast_string_field_pool *pool, size_t size,
+			    ast_string_field *fields, int num_fields);
+
+/*!
+  \internal
+  \brief Allocate space for field in the pool
+  \param pool Pointer to the pool structure
+  \param needed Amount of space needed for this field
+  \param fields Pointer to the first entry of the field array
+  \param num_fields Number of fields in the array
+  \return NULL on failure, an address for the field on success
+
+  This function will allocate the requested amount of space from
+  the field pool. If the requested amount of space is not available,
+  the pool will be expanded until enough space becomes available,
+  and the existing fields stored there will be updated to point
+  into the new pool.
+*/
+char *__ast_string_field_alloc_space(struct ast_string_field_pool *pool, size_t needed,
+				     ast_string_field *fields, int num_fields);
+
+/*!
+  The default amount of storage to be allocated for a field pool.
+*/
+#define AST_STRING_FIELD_DEFAULT_POOL 512
+
+/*!
+  \brief Declare a string field
+  \param name The field name
+*/
+#define AST_STRING_FIELD(name) const ast_string_field name;
+
+/*!
+  \brief Declare the fields needed in a structure
+  \param field_list The list of fields to declare, using AST_STRING_FIELD() for each one
+*/
+#define AST_DECLARE_STRING_FIELDS(field_list) \
+	ast_string_field __begin_field[0]; \
+	field_list \
+	ast_string_field __end_field[0]; \
+	struct ast_string_field_pool __field_pool;
+
+/*!
+  \brief Get the number of string fields in a structure
+  \param x Pointer to a structure containing fields
+  \return the number of fields in the structure's definition
+*/
+#define ast_string_field_count(x) \
+	(offsetof(typeof(*x), __end_field) - offsetof(typeof(*x), __begin_field)) / sizeof(ast_string_field)
+
+/*!
+  \brief Get the index of a field in a structure
+  \param x Pointer to a structure containing fields
+  \param field Name of the field to locate
+  \return the position (index) of the field within the structure's
+  array of fields
+*/
+#define ast_string_field_index(x, field) \
+	(offsetof(typeof(*x), field) - offsetof(typeof(*x), __begin_field)) / sizeof(ast_string_field)
+
+/*!
+  \brief Initialize a field pool and fields
+  \param x Pointer to a structure containing fields
+  \return 0 on failure, non-zero on success
+*/
+#define ast_string_field_init(x) \
+	__ast_string_field_init(&x->__field_pool, AST_STRING_FIELD_DEFAULT_POOL, &x->__begin_field[0], ast_string_field_count(x))
+
+/*!
+  \brief Set a field to a simple string value
+  \param x Pointer to a structure containing fields
+  \param index Index position of the field within the structure
+  \param data String value to be copied into the field
+  \return nothing
+*/
+#define ast_string_field_index_set(x, index, data) do { \
+	if ((x->__begin_field[index] = __ast_string_field_alloc_space(&x->__field_pool, strlen(data) + 1, &x->__begin_field[0], ast_string_field_count(x)))) \
+		strcpy((char *) x->__begin_field[index], data); \
+	} while (0)
+
+/*!
+  \brief Set a field to a simple string value
+  \param x Pointer to a structure containing fields
+  \param field Name of the field to set
+  \param data String value to be copied into the field
+  \return nothing
+*/
+#define ast_string_field_set(x, field, data) \
+	ast_string_field_index_set(x, ast_string_field_index(x, field), data)
+
+/*!
+  \brief Set a field to a simple complex (built) value
+  \param x Pointer to a structure containing fields
+  \param index Index position of the field within the structure
+  \param fmt printf-style format string
+  \param args Arguments for format string
+  \return nothing
+*/
+#define ast_string_field_index_build(x, index, fmt, args...) do { \
+	char s; \
+	size_t needed; \
+	needed = snprintf(&s, 1, fmt, args) + 1; \
+	if ((x->__begin_field[index] = __ast_string_field_alloc_space(&x->__field_pool, needed, &x->__begin_field[0], ast_string_field_count(x)))) \
+		sprintf((char *) x->__begin_field[index], fmt, args); \
+	} while (0)
+
+/*!
+  \brief Set a field to a simple complex (built) value
+  \param x Pointer to a structure containing fields
+  \param field Name of the field to set
+  \param fmt printf-style format string
+  \param args Arguments for format string
+  \return nothing
+*/
+#define ast_string_field_build(x, field, fmt, args...) \
+	ast_string_field_index_build(x, ast_string_field_index(x, field), fmt, args)
+
+/*!
+  \brief Free a field's value.
+  \param x Pointer to a structure containing fields
+  \param index Index position of the field within the structure
+  \return nothing
+
+  \note Because of the storage pool used, the memory
+  occupied by the field's value is \b not recovered; the field
+  pointer is just changed to point to an empty string.
+*/
+#define ast_string_field_index_free(x, index) do { \
+	x->__begin_field[index] = __ast_string_field_empty; \
+	} while(0)
+
+/*!
+  \brief Free a field's value.
+  \param x Pointer to a structure containing fields
+  \param field Name of the field to free
+  \return nothing
+
+  \note Because of the storage pool used, the memory
+  occupied by the field's value is \b not recovered; the field
+  pointer is just changed to point to an empty string.
+*/
+#define ast_string_field_free(x, field) \
+	ast_string_field_index_free(x, ast_string_field_index(x, field))
+
+/*!
+  \brief Free all fields (and the storage pool) in a structure
+  \param x Pointer to a structure containing fields
+  \return nothing
+
+  After calling this macro, fields can no longer be accessed in
+  structure; it should only be called immediately before freeing
+  the structure itself.
+*/
+#define ast_string_field_free_all(x) do { \
+	int index; \
+	for (index = 0; index < ast_string_field_count(x); index ++) \
+		ast_string_field_index_free(x, index); \
+	free(x->__field_pool.base); \
+	} while(0)
+
+#endif /* _ASTERISK_STRINGFIELDS_H */