diff options
Diffstat (limited to 'dbus/dbus-message.c')
| -rw-r--r-- | dbus/dbus-message.c | 325 |
1 files changed, 319 insertions, 6 deletions
diff --git a/dbus/dbus-message.c b/dbus/dbus-message.c index a52d7097..1e95bec7 100644 --- a/dbus/dbus-message.c +++ b/dbus/dbus-message.c @@ -21,7 +21,12 @@ * */ +#include "dbus-internals.h" #include "dbus-message.h" +#include "dbus-message-internal.h" +#include "dbus-memory.h" +#include "dbus-list.h" +#include <string.h> /** * @defgroup DBusMessageInternals DBusMessage implementation details @@ -43,17 +48,72 @@ struct DBusMessage { int refcount; /**< Reference count */ - + + unsigned char *header; /**< Header network data, stored + * separately from body so we can + * independently realloc it. + */ + int header_len; /**< Length of header data. */ + + unsigned char *body; /**< Body network data. */ + int body_len; /**< Length of body data. */ + + unsigned int locked : 1; /**< Message being sent, no modifications allowed. */ }; +/** + * Gets the data to be sent over the network for this message. + * The header and then the body should be written out. + * This function is guaranteed to always return the same + * data once a message is locked (with _dbus_message_lock()). + * + * @param message the message. + * @param header return location for message header data. + * @param header_len return location for header length in bytes. + * @param body return location for message body data. + * @param body_len return location for body length in bytes. + */ +void +_dbus_message_get_network_data (DBusMessage *message, + const unsigned char **header, + int *header_len, + const unsigned char **body, + int *body_len) +{ + _dbus_assert (message->locked); + + *header = message->header; + *header_len = message->header_len; + *body = message->body; + *body_len = message->body_len; +} + +/** + * Locks a message. Allows checking that applications don't keep a + * reference to a message in the outgoing queue and change it + * underneath us. Messages are locked when they enter the outgoing + * queue (dbus_connection_send_message()), and the library complains + * if the message is modified while locked. + * + * @param message the message to lock. + */ +void +_dbus_message_lock (DBusMessage *message) +{ + message->locked = TRUE; +} + /** @} */ /** * @defgroup DBusMessage DBusMessage * @ingroup DBus - * @brief DBusMessage object + * @brief Message to be sent or received over a DBusConnection. * - * Types and functions related to the DBusMessage object. + * A DBusMessage is the most basic unit of communication over a + * DBusConnection. A DBusConnection represents a stream of messages + * received from a remote application, and a stream of messages + * sent to a remote application. * * @{ */ @@ -66,15 +126,30 @@ struct DBusMessage */ /** - * Constructs a new message. + * Constructs a new message. Returns #NULL if memory + * can't be allocated for the message. + * * @return a new DBusMessage, free with dbus_message_unref() * @see dbus_message_unref() */ DBusMessage* dbus_message_new (void) { + DBusMessage *message; + + message = dbus_new0 (DBusMessage, 1); + if (message == NULL) + return NULL; - return NULL; + message->refcount = 1; + + /* We need to decide what a message contains. ;-) */ + message->header = _dbus_strdup ("H"); + message->header_len = 2; + message->body = _dbus_strdup ("Body"); + message->body_len = 5; + + return message; } @@ -87,7 +162,7 @@ dbus_message_new (void) void dbus_message_ref (DBusMessage *message) { - + message->refcount += 1; } /** @@ -99,8 +174,246 @@ dbus_message_ref (DBusMessage *message) void dbus_message_unref (DBusMessage *message) { + _dbus_assert (message != NULL); + _dbus_assert (message->refcount > 0); + + message->refcount -= 1; + if (message->refcount == 0) + { + + dbus_free (message); + } +} + +/** @} */ + +/** + * @addtogroup DBusMessageInternals + * + * @{ + */ +/** + * @typedef DBusMessageLoader + * + * The DBusMessageLoader object encapsulates the process of converting + * a byte stream into a series of DBusMessage. It buffers the incoming + * bytes as efficiently as possible, and generates a queue of + * messages. DBusMessageLoader is typically used as part of a + * DBusTransport implementation. The DBusTransport then hands off + * the loaded messages to a DBusConnection, making the messages + * visible to the application. + * + */ + +/** + * Implementation details of DBusMessageLoader. + * All members are private. + */ +struct DBusMessageLoader +{ + int refcount; /**< Reference count. */ + + int allocated; /**< Allocated size of "data" */ + int length; /**< Used size of "data" */ + + unsigned char *data; /**< Buffered data. */ + + DBusList *messages; /**< Complete messages. */ + + unsigned int buffer_outstanding : 1; /**< Someone is using the buffer to read */ +}; + +/** + * The initial buffer size of the message loader. + * + * @todo this should be based on min header size plus some average + * body size, or something. Or rather, the min header size only, if we + * want to try to read only the header, store that in a DBusMessage, + * then read only the body and store that, etc., depends on + * how we optimize _dbus_message_loader_get_buffer() and what + * the exact message format is. + */ +#define INITIAL_LOADER_DATA_LEN 32 + +/** + * Creates a new message loader. Returns #NULL if memory can't + * be allocated. + * + * @returns new loader, or #NULL. + */ +DBusMessageLoader* +_dbus_message_loader_new (void) +{ + DBusMessageLoader *loader; + + loader = dbus_new0 (DBusMessageLoader, 1); + if (loader == NULL) + return NULL; + + loader->refcount = 1; + + /* Header, plus room for averagish other fields */ + loader->allocated = INITIAL_LOADER_DATA_LEN; + loader->data = dbus_malloc (loader->allocated); + if (loader->data == NULL) + loader->allocated = 0; + + loader->length = 0; + + return loader; +} + +/** + * Increments the reference count of the loader. + * + * @param loader the loader. + */ +void +_dbus_message_loader_ref (DBusMessageLoader *loader) +{ + loader->refcount += 1; +} + +/** + * Decrements the reference count of the loader and finalizes the + * loader when the count reaches zero. + * + * @param loader the loader. + */ +void +_dbus_message_loader_unref (DBusMessageLoader *loader) +{ + loader->refcount -= 1; + if (loader->refcount == 0) + { + _dbus_list_foreach (&loader->messages, + (DBusForeachFunction) dbus_message_unref, + NULL); + _dbus_list_clear (&loader->messages); + dbus_free (loader->data); + dbus_free (loader); + } +} + +/** + * Gets the buffer to use for reading data from the network. Network + * data is read directly into an allocated buffer, which is then used + * in the DBusMessage, to avoid as many extra memcpy's as possible. + * The buffer must always be returned immediately using + * _dbus_message_loader_return_buffer(), even if no bytes are + * successfully read. + * + * @todo this function can be a lot more clever. For example + * it can probably always return a buffer size to read exactly + * the body of the next message, thus avoiding any memory wastage + * or reallocs. + * + * @param loader the message loader. + * @param buffer address to store the buffer. + * @param buffer_len address to store the buffer length. + * @returns #FALSE if no buffer can be allocated. + */ +dbus_bool_t +_dbus_message_loader_get_buffer (DBusMessageLoader *loader, + unsigned char **buffer, + int *buffer_len) +{ + _dbus_assert (!loader->buffer_outstanding); + +#define MIN_BUFSIZE INITIAL_LOADER_DATA_LEN + + if ((loader->length + MIN_BUFSIZE) >= loader->allocated) + { + unsigned char *buf; + int new_allocated; + + /* double (and add MIN_BUFSIZE, in case allocated == 0) */ + new_allocated = MIN_BUFSIZE + loader->allocated * 2; + + if (new_allocated <= loader->allocated) + { + /* ugh, overflow. Maybe someone is trying to screw us. */ + /* (we could overflow so far that new_allocated > loader->allocated + * but nothing should break in that case) + */ + return FALSE; + } + + buf = dbus_realloc (loader->data, new_allocated); + if (buf == NULL) + return FALSE; + + loader->data = buf; + loader->allocated = new_allocated; + } + + *buffer = loader->data + loader->length; + *buffer_len = loader->allocated - loader->length; + + loader->buffer_outstanding = TRUE; + return TRUE; +} + +/** + * Returns a buffer obtained from _dbus_message_loader_get_buffer(), + * indicating to the loader how many bytes of the buffer were filled + * in. This function must always be called, even if no bytes were + * successfully read. + * + * @param loader the loader. + * @param buffer the buffer. + * @param bytes_read number of bytes that were read into the buffer. + */ +void +_dbus_message_loader_return_buffer (DBusMessageLoader *loader, + unsigned char *buffer, + int bytes_read) +{ + _dbus_assert (loader->buffer_outstanding); + /* FIXME fake implementation just creates a message for every 7 + * bytes. The real implementation will pass ownership of + * loader->data to new messages, to avoid memcpy. We can also + * smart-realloc loader->data to shrink it if it's too big, though + * _dbus_message_loader_get_buffer() could strategically arrange for + * that to usually not happen. + */ + + loader->length += bytes_read; + + loader->buffer_outstanding = FALSE; + + while (loader->length >= 7) + { + DBusMessage *message; + + message = dbus_message_new (); + if (message == NULL) + break; /* ugh, postpone this I guess. */ + + _dbus_list_append (&loader->messages, message); + + memmove (loader->data, loader->data + 7, + loader->length - 7); + loader->length -= 7; + + _dbus_verbose ("Loaded message %p\n", message); + } +} + +/** + * Pops a loaded message (passing ownership of the message + * to the caller). Returns #NULL if no messages have been + * loaded. + * + * @param loader the loader. + * @returns the next message, or #NULL if none. + */ +DBusMessage* +_dbus_message_loader_pop_message (DBusMessageLoader *loader) +{ + return _dbus_list_pop_first (&loader->messages); } /** @} */ |