#include <bson/bson.h>

       MongoDB, Inc

       2009-present, MongoDB, Inc.

1.30.4                                            Jun 08, 2025                                         BSON_T(3)

       The  bson_t  structure  represents  a  BSON  document. This structure manages the underlying BSON encoded
       buffer. For mutable documents, it can append new data to the document.

       The  BSONspecification allows BSON documents to have duplicate keys. Documents are stored as an ordered
       list of key-value pairs. A bson_t may contain duplicate keys. Applications should refrain from generating
       such documents, because MongoDB server behavior is undefined when  a  BSON  document  contains  duplicate
       keys.

          static void
          create_on_heap (void)
          {
             bson_t *b = bson_new ();

             BSON_APPEND_INT32 (b, "foo", 123);
             BSON_APPEND_UTF8 (b, "bar", "foo");
             BSON_APPEND_DOUBLE (b, "baz", 1.23f);

             bson_destroy (b);
          }

       The bson_t structure attempts to use an inline allocation within the structure to speed up performance of
       small documents. When this  internal  buffer  has  been  exhausted,  a  heap  allocated  buffer  will  be
       dynamically allocated. Therefore, it is essential to call bson_destroy() on allocated documents.

          #include <bson/bson.h>

          /**
           * bson_empty:
           * @b: a bson_t.
           *
           * Checks to see if @b is an empty BSON document. An empty BSON document is
           * a 5 byte document which contains the length (4 bytes) and a single NUL
           * byte indicating end of fields.
           */
          #define bson_empty(b) /* ... */

          /**
           * bson_empty0:
           *
           * Like bson_empty() but treats NULL the same as an empty bson_t document.
           */
          #define bson_empty0(b) /* ... */

          /**
           * bson_clear:
           *
           * Easily free a bson document and set it to NULL. Use like:
           *
           * bson_t *doc = bson_new();
           * bson_clear (&doc);
           * BSON_ASSERT (doc == NULL);
           */
          #define bson_clear(bptr) /* ... */

          /**
           * BSON_MAX_SIZE:
           *
           * The maximum size in bytes of a BSON document.
           */
          #define BSON_MAX_SIZE /* ... */

          #define BSON_APPEND_ARRAY(b, key, val) \
             bson_append_array (b, key, (int) strlen (key), val)

          #define BSON_APPEND_ARRAY_BEGIN(b, key, child) \
             bson_append_array_begin (b, key, (int) strlen (key), child)

          #define BSON_APPEND_BINARY(b, key, subtype, val, len) \
             bson_append_binary (b, key, (int) strlen (key), subtype, val, len)

          #define BSON_APPEND_BOOL(b, key, val) \
             bson_append_bool (b, key, (int) strlen (key), val)

          #define BSON_APPEND_CODE(b, key, val) \
             bson_append_code (b, key, (int) strlen (key), val)

          #define BSON_APPEND_CODE_WITH_SCOPE(b, key, val, scope) \
             bson_append_code_with_scope (b, key, (int) strlen (key), val, scope)

          #define BSON_APPEND_DBPOINTER(b, key, coll, oid) \
             bson_append_dbpointer (b, key, (int) strlen (key), coll, oid)

          #define BSON_APPEND_DOCUMENT_BEGIN(b, key, child) \
             bson_append_document_begin (b, key, (int) strlen (key), child)

          #define BSON_APPEND_DOUBLE(b, key, val) \
             bson_append_double (b, key, (int) strlen (key), val)

          #define BSON_APPEND_DOCUMENT(b, key, val) \
             bson_append_document (b, key, (int) strlen (key), val)

          #define BSON_APPEND_INT32(b, key, val) \
             bson_append_int32 (b, key, (int) strlen (key), val)

          #define BSON_APPEND_INT64(b, key, val) \
             bson_append_int64 (b, key, (int) strlen (key), val)

          #define BSON_APPEND_MINKEY(b, key) \
             bson_append_minkey (b, key, (int) strlen (key))

          #define BSON_APPEND_DECIMAL128(b, key, val) \
             bson_append_decimal128 (b, key, (int) strlen (key), val)

          #define BSON_APPEND_MAXKEY(b, key) \
             bson_append_maxkey (b, key, (int) strlen (key))

          #define BSON_APPEND_NULL(b, key) bson_append_null (b, key, (int) strlen (key))

          #define BSON_APPEND_OID(b, key, val) \
             bson_append_oid (b, key, (int) strlen (key), val)

          #define BSON_APPEND_REGEX(b, key, val, opt) \
             bson_append_regex (b, key, (int) strlen (key), val, opt)

          #define BSON_APPEND_UTF8(b, key, val) \
             bson_append_utf8 (b, key, (int) strlen (key), val, (int) strlen (val))

          #define BSON_APPEND_SYMBOL(b, key, val) \
             bson_append_symbol (b, key, (int) strlen (key), val, (int) strlen (val))

          #define BSON_APPEND_TIME_T(b, key, val) \
             bson_append_time_t (b, key, (int) strlen (key), val)

          #define BSON_APPEND_TIMEVAL(b, key, val) \
             bson_append_timeval (b, key, (int) strlen (key), val)

          #define BSON_APPEND_DATE_TIME(b, key, val) \
             bson_append_date_time (b, key, (int) strlen (key), val)

          #define BSON_APPEND_TIMESTAMP(b, key, val, inc) \
             bson_append_timestamp (b, key, (int) strlen (key), val, inc)

          #define BSON_APPEND_UNDEFINED(b, key) \
             bson_append_undefined (b, key, (int) strlen (key))

          #define BSON_APPEND_VALUE(b, key, val) \
             bson_append_value (b, key, (int) strlen (key), (val))

          BSON_ALIGNED_BEGIN (128)
          typedef struct {
             uint32_t flags;       /* Internal flags for the bson_t. */
             uint32_t len;         /* Length of BSON data. */
             uint8_t padding[120]; /* Padding for stack allocation. */
          } bson_t BSON_ALIGNED_END (128);