shadow.c File Reference

Implements the user-facing functions of the Shadow library. More...

#include <string.h>
#include "shadow.h"

Macros
#define	SHADOW_NAME_MAX_LENGTH   ( 64U )
	Maximum shadow name length. Refer to https://docs.aws.amazon.com/general/latest/gr/iot-core.html#device-shadow-limits for more details about the Device Shadow limits.
#define	SHADOW_THINGNAME_MAX_LENGTH   ( 128U )
	Maximum thing name length. Refer to https://docs.aws.amazon.com/general/latest/gr/iot-core.html#device-shadow-limits for more details about the Device Shadow limits.
#define	SHADOW_OP_UPDATE_ACCEPTED   SHADOW_OP_UPDATE SHADOW_SUFFIX_ACCEPTED
	The string representing "/shadow/update/accepted".
#define	SHADOW_OP_UPDATE_REJECTED   SHADOW_OP_UPDATE SHADOW_SUFFIX_REJECTED
	The string representing "/shadow/update/rejected".
#define	SHADOW_OP_UPDATE_DELTA   SHADOW_OP_UPDATE SHADOW_SUFFIX_DELTA
	The string representing "/shadow/update/delta".
#define	SHADOW_OP_UPDATE_DOCUMENTS   SHADOW_OP_UPDATE SHADOW_SUFFIX_DOCUMENTS
	The string representing "/shadow/update/document".
#define	SHADOW_OP_DELETE_ACCEPTED   SHADOW_OP_DELETE SHADOW_SUFFIX_ACCEPTED
	The string representing "/shadow/delete/accepted".
#define	SHADOW_OP_DELETE_REJECTED   SHADOW_OP_DELETE SHADOW_SUFFIX_REJECTED
	The string representing "/shadow/delete/accepted".
#define	SHADOW_OP_GET_ACCEPTED   SHADOW_OP_GET SHADOW_SUFFIX_ACCEPTED
	The string representing "/shadow/get/accepted".
#define	SHADOW_OP_GET_REJECTED   SHADOW_OP_GET SHADOW_SUFFIX_REJECTED
	The string representing "/shadow/get/accepted".
#define	SHADOW_OP_UPDATE_ACCEPTED_LENGTH   ( SHADOW_OP_UPDATE_LENGTH + SHADOW_SUFFIX_ACCEPTED_LENGTH )
	The length of "/shadow/update/accepted".
#define	SHADOW_OP_UPDATE_REJECTED_LENGTH   ( SHADOW_OP_UPDATE_LENGTH + SHADOW_SUFFIX_REJECTED_LENGTH )
	The length of "/shadow/update/rejected".
#define	SHADOW_OP_UPDATE_DOCUMENTS_LENGTH   ( SHADOW_OP_UPDATE_LENGTH + SHADOW_SUFFIX_DOCUMENTS_LENGTH )
	The length of "/shadow/update/document".
#define	SHADOW_OP_UPDATE_DELTA_LENGTH   ( SHADOW_OP_UPDATE_LENGTH + SHADOW_SUFFIX_DELTA_LENGTH )
	The length of "/shadow/update/rejected".
#define	SHADOW_OP_GET_ACCEPTED_LENGTH   ( SHADOW_OP_GET_LENGTH + SHADOW_SUFFIX_ACCEPTED_LENGTH )
	The length of "/shadow/get/accepted".
#define	SHADOW_OP_GET_REJECTED_LENGTH   ( SHADOW_OP_GET_LENGTH + SHADOW_SUFFIX_REJECTED_LENGTH )
	The length of "/shadow/get/rejected".
#define	SHADOW_OP_DELETE_ACCEPTED_LENGTH   ( SHADOW_OP_DELETE_LENGTH + SHADOW_SUFFIX_ACCEPTED_LENGTH )
	The length of "/shadow/get/accepted".
#define	SHADOW_OP_DELETE_REJECTED_LENGTH   ( SHADOW_OP_DELETE_LENGTH + SHADOW_SUFFIX_REJECTED_LENGTH )
	The length of "/shadow/delete/rejected".

Functions
static ShadowStatus_t	validateMatchTopicParameters (const char *pTopic, uint16_t topicLength, const ShadowMessageType_t *pMessageType)
	Check if Shadow_MatchTopicString has valid parameters.
static ShadowStatus_t	validateAssembleTopicParameters (ShadowTopicStringType_t topicType, const char *pThingName, uint8_t thingNameLength, const char *pShadowName, uint8_t shadowNameLength, const char *pTopicBuffer, const uint16_t *pOutLength)
	Check if Shadow_AssembleTopicString has valid parameters.
static ShadowStatus_t	containsSubString (const char *pString, uint16_t stringLength, const char *pSubString, uint16_t subStringLength)
	Determine if the string contains the substring.
static ShadowStatus_t	validateName (const char *pString, uint16_t stringLength, uint8_t maxAllowedLength, uint8_t *pNameLength)
	Check if the Thing or Shadow Name is valid.
static ShadowStatus_t	extractShadowMessageType (const char *pString, uint16_t stringLength, ShadowMessageType_t *pMessageType)
	Extract the Shadow message type from a string.
static ShadowStatus_t	extractThingName (const char *pTopic, uint16_t topicLength, uint16_t *pConsumedTopicLength, uint8_t *pThingNameLength)
	Extract the Thing name from a topic string.
static ShadowStatus_t	extractShadowRootAndName (const char *pTopic, uint16_t topicLength, uint16_t *pConsumedTopicLength, uint8_t *pShadowNameLength)
	Extract the classic shadow root OR the named shadow root and shadow name from a topic string.
static const char *	getShadowOperationString (ShadowTopicStringType_t topicType)
	Get the shadow operation string for a given shadow topic type.
static uint16_t	getShadowOperationLength (ShadowTopicStringType_t topicType)
	Get the shadow operation string length for a given shadow topic type.
static void	createShadowTopicString (ShadowTopicStringType_t topicType, const char *pThingName, uint8_t thingNameLength, const char *pShadowName, uint8_t shadowNameLength, char *pTopicBuffer)
	Creates a shadow topic string.
ShadowStatus_t	Shadow_MatchTopicString (const char *pTopic, uint16_t topicLength, ShadowMessageType_t *pMessageType, const char **pThingName, uint8_t *pThingNameLength, const char **pShadowName, uint8_t *pShadowNameLength)
	Given the topic string of an incoming message, determine whether it is related to a device shadow; if it is, return information about the type of device shadow message, and pointers to the Thing Name and Shadow Name inside of the topic string. See ShadowMessageType_t for the list of message types. Those types correspond to Device Shadow Topics.
ShadowStatus_t	Shadow_AssembleTopicString (ShadowTopicStringType_t topicType, const char *pThingName, uint8_t thingNameLength, const char *pShadowName, uint8_t shadowNameLength, char *pTopicBuffer, uint16_t bufferSize, uint16_t *pOutLength)
	Assemble shadow topic string when Thing Name or Shadow Name is only known at run time. If both the Thing Name and Shadow Name are known at compile time, use SHADOW_TOPIC_STR_* macros instead.
ShadowStatus_t	Shadow_MatchTopic (const char *pTopic, uint16_t topicLength, ShadowMessageType_t *pMessageType, const char **pThingName, uint16_t *pThingNameLength)
	Given the topic string of an incoming message, determine whether it is related to an unnamed ("Classic") device shadow; if it is, return information about the type of device shadow message, and a pointers to the Thing Name inside of the topic string. See ShadowMessageType_t for the list of message types. Those types correspond to Device Shadow Topics.

Detailed Description

Implements the user-facing functions of the Shadow library.

Function Documentation

validateMatchTopicParameters()

static ShadowStatus_t validateMatchTopicParameters ( const char *  pTopic, uint16_t  topicLength, const ShadowMessageType_t *  pMessageType  )

static

Check if Shadow_MatchTopicString has valid parameters.

Parameters

[in]	pTopic	Pointer to the topic string.
[in]	topicLength	Length of pTopic.
[in]	pMessageType	Pointer to caller-supplied memory for returning the type of the shadow message.

Returns

Return SHADOW_SUCCESS if the parameters are valid; return SHADOW_BAD_PARAMETER if not.

validateAssembleTopicParameters()

static ShadowStatus_t validateAssembleTopicParameters ( ShadowTopicStringType_t  topicType, const char *  pThingName, uint8_t  thingNameLength, const char *  pShadowName, uint8_t  shadowNameLength, const char *  pTopicBuffer, const uint16_t *  pOutLength  )

static

Check if Shadow_AssembleTopicString has valid parameters.

Parameters

[in]	topicType	Shadow topic type.
[in]	pThingName	Thing Name string.
[in]	thingNameLength	Length of Thing Name string pointed to by pThingName.
[in]	pShadowName	Shadow Name string.
[in]	shadowNameLength	Length of Shadow Name string pointed to by pShadowName.
[in]	pTopicBuffer	Pointer to the topic buffer.
[in]	pOutLength	Pointer to the length of the topic created.

Returns

Return SHADOW_SUCCESS if the parameters are valid; return SHADOW_BAD_PARAMETER if not.

containsSubString()

static ShadowStatus_t containsSubString ( const char *  pString, uint16_t  stringLength, const char *  pSubString, uint16_t  subStringLength  )

static

Determine if the string contains the substring.

Parameters

[in]	pString	Pointer to the string.
[in]	stringLength	Length of pString.
[in]	pSubString	Pointer to the substring.
[in]	subStringLength	Length of pSubString.

Returns

Return SHADOW_SUCCESS if it contains; return SHADOW_FAIL if not.

validateName()

static ShadowStatus_t validateName ( const char *  pString, uint16_t  stringLength, uint8_t  maxAllowedLength, uint8_t *  pNameLength  )

static

Check if the Thing or Shadow Name is valid.

Parameters

[in]	pString	Pointer to the starting of a name.
[in]	stringLength	Length of pString.
[in]	maxAllowedLength	Maximum allowed length of the Thing or Shadow name.
[out]	pNameLength	Pointer to caller-supplied memory for returning the length of the Thing or Shadow Name.

Returns

Return SHADOW_SUCCESS if it is valid; return SHADOW_FAIL if it is not.

extractShadowMessageType()

static ShadowStatus_t extractShadowMessageType ( const char *  pString, uint16_t  stringLength, ShadowMessageType_t *  pMessageType  )

static

Extract the Shadow message type from a string.

Parameters

[in]	pString	Pointer to the string.
[in]	stringLength	Length of pString.
[out]	pMessageType	Pointer to caller-supplied memory for returning the type of the shadow message.

Returns

Return SHADOW_SUCCESS if successfully extracted; return SHADOW_MESSAGE_TYPE_PARSE_FAILED if failed.

extractThingName()

static ShadowStatus_t extractThingName ( const char *  pTopic, uint16_t  topicLength, uint16_t *  pConsumedTopicLength, uint8_t *  pThingNameLength  )

static

Extract the Thing name from a topic string.

Parameters

[in]	pTopic	Pointer to the topic string.
[in]	topicLength	Length of pTopic.
[in,out]	pConsumedTopicLength	Pointer to caller-supplied memory for returning the consumed topic length.
[out]	pThingNameLength	Pointer to caller-supplied memory for returning the Thing name length.

Returns

Return SHADOW_SUCCESS if successfully extracted; return SHADOW_THINGNAME_PARSE_FAILED if Thing name parsing fails.

extractShadowRootAndName()

static ShadowStatus_t extractShadowRootAndName ( const char *  pTopic, uint16_t  topicLength, uint16_t *  pConsumedTopicLength, uint8_t *  pShadowNameLength  )

static

Extract the classic shadow root OR the named shadow root and shadow name from a topic string.

Parameters

[in]	pTopic	Pointer to the topic string.
[in]	topicLength	Length of pTopic.
[in,out]	pConsumedTopicLength	Pointer to caller-supplied memory for returning the consumed topic length.
[out]	pShadowNameLength	Pointer to caller-supplied memory for returning the shadow name length.

Returns

Return SHADOW_SUCCESS if successfully extracted; return SHADOW_ROOT_PARSE_FAILED shadow root parsing fails. return SHADOW_SHADOWNAME_PARSE_FAILED shadow name parsing fails.

getShadowOperationString()

static const char * getShadowOperationString ( ShadowTopicStringType_t  topicType )

static

Get the shadow operation string for a given shadow topic type.

Parameters

[in]

topicType

The given shadow topic type.

Returns

The shadow operation string for the given shadow type.

getShadowOperationLength()

static uint16_t getShadowOperationLength ( ShadowTopicStringType_t  topicType )

static

Get the shadow operation string length for a given shadow topic type.

Parameters

[in]

topicType

The given shadow topic type.

Returns

The shadow operation string length for the given shadow type.

createShadowTopicString()

static void createShadowTopicString ( ShadowTopicStringType_t  topicType, const char *  pThingName, uint8_t  thingNameLength, const char *  pShadowName, uint8_t  shadowNameLength, char *  pTopicBuffer  )

static

Creates a shadow topic string.

Parameters

[in]	topicType	The type of shadow topic to be constructed.
[in]	pThingName	Pointer to the Thing name.
[in]	thingNameLength	The length of the Thing name.
[in]	pShadowName	Pointer to the Shadow name.
[in]	shadowNameLength	The length of the Shadow name.
[out]	pTopicBuffer	Pointer to caller-supplied memory for returning the constructed shadow topic string.

Shadow_MatchTopicString()

ShadowStatus_t Shadow_MatchTopicString	(	const char *	pTopic,
		uint16_t	topicLength,
		ShadowMessageType_t *	pMessageType,
		const char **	pThingName,
		uint8_t *	pThingNameLength,
		const char **	pShadowName,
		uint8_t *	pShadowNameLength
	)

Given the topic string of an incoming message, determine whether it is related to a device shadow; if it is, return information about the type of device shadow message, and pointers to the Thing Name and Shadow Name inside of the topic string. See ShadowMessageType_t for the list of message types. Those types correspond to Device Shadow Topics.

Note

When this function returns, the pointer pThingName points at the first character of the <thingName> segment inside of the topic string. Likewise, the pointer pShadowName points at the first character of the <shadowName> segment inside of the topic string (if the topic is for a named shadow, not the "Classic" shadow.) Caller is responsible for keeping the memory holding the topic string around while accessing the Thing Name through pThingName and the Shadow Name through pShadowName.

Parameters

[in]	pTopic	Pointer to the MQTT topic string. Does not have to be null-terminated.
[in]	topicLength	Length of the MQTT topic string.
[out]	pMessageType	Pointer to caller-supplied memory for returning the type of the shadow message.
[out]	pThingName	Points to the 1st character of Thing Name inside of the topic string, and can be null if caller does not need to know the Thing Name contained in the topic string.
[out]	pThingNameLength	Pointer to caller-supplied memory for returning the length of the Thing Name, and can be null if caller does not need to know the Thing Name contained in the topic string.
[out]	pShadowName	Points to the 1st character of Shadow Name inside of the topic string, and can be null if caller does not need to know the Shadow Name contained in the topic string. Null is returned if the shadow is Classic.
[out]	pShadowNameLength	Pointer to caller-supplied memory for returning the length of the Shadow Name, and can be null if caller does not need to know the Shadow Name contained in the topic string. A value of 0 is returned if the shadow is Classic.

Returns

One of the following:

• SHADOW_SUCCESS if the message is related to a device shadow;
• An error code defined in ShadowStatus_t if the message is not related to a device shadow, if any input parameter is invalid, or if the function fails to parse the topic string.

Example

// Variables used in this example.
 
#define SHADOW_TOPIC_MAX_LENGTH  ( 256U )
 
ShadowStatus_te shadowStatus = SHADOW_SUCCESS;
char * pTopicName; //usually supplied by MQTT stack
uint16_t topicNameLength; //usually supplied by MQTT stack
ShadowMessageType_t messageType;
 
shadowStatus = Shadow_MatchTopicString( pTopicName,
                                        topicNameLength,
                                        &messageType,
                                        NULL,
                                        NULL,
                                        NULL,
                                        NULL );
 
if( shadowStatus == SHADOW_SUCCESS )
{
     // It is a device shadow message. And the type of the message has been returned in messageType.
     // Now we can act on the message.
}

Shadow_AssembleTopicString()

ShadowStatus_t Shadow_AssembleTopicString	(	ShadowTopicStringType_t	topicType,
		const char *	pThingName,
		uint8_t	thingNameLength,
		const char *	pShadowName,
		uint8_t	shadowNameLength,
		char *	pTopicBuffer,
		uint16_t	bufferSize,
		uint16_t *	pOutLength
	)

Assemble shadow topic string when Thing Name or Shadow Name is only known at run time. If both the Thing Name and Shadow Name are known at compile time, use SHADOW_TOPIC_STR_* macros instead.

Parameters

[in]	topicType	Indicates what topic will be written into the buffer pointed to by pTopicBuffer. can be one of: ShadowTopicStringTypeGet ShadowTopicStringTypeGetAccepted ShadowTopicStringTypeGetRejected ShadowTopicStringTypeDelete ShadowTopicStringTypeDeleteAccepted ShadowTopicStringTypeDeleteRejected ShadowTopicStringTypeUpdate ShadowTopicStringTypeUpdateAccepted ShadowTopicStringTypeUpdateRejected ShadowTopicStringTypeUpdateDocuments ShadowTopicStringTypeUpdateDelta
[in]	pThingName	Thing Name string. No need to be null terminated. Must not be NULL.
[in]	thingNameLength	Length of Thing Name string pointed to by pThingName. Must not be zero.
[in]	pShadowName	Shadow Name string. No need to be null terminated. Must not be NULL. Empty string for classic shadow.
[in]	shadowNameLength	Length of Shadow Name string pointed to by pShadowName. Zero for classic shadow.
[out]	pTopicBuffer	Pointer to buffer for returning the topic string. Caller is responsible for supplying memory pointed to by pTopicBuffer. This function does not fill in the terminating null character. The app can supply a buffer that does not have space for holding the null character.
[in]	bufferSize	Length of pTopicBuffer. This function will return error if bufferSize is less than the length of the assembled topic string.
[out]	pOutLength	Pointer to caller-supplied memory for returning the length of the topic string.

Returns

One of the following:

• SHADOW_SUCCESS if successful.
• An error code if failed to assemble.

Example

// Variables used in this example.
 
#define SHADOW_TOPIC_MAX_LENGTH  ( 256U )
 
ShadowStatus_t shadowStatus = SHADOW_SUCCESS;
char topicBuffer[ SHADOW_TOPIC_MAX_LENGTH ] = { 0 };
uint16_t bufferSize = SHADOW_TOPIC_MAX_LENGTH;
uint16_t outLength = 0;
const char thingName[] = "TestThingName";
uint16_t thingNameLength  = ( sizeof( thingName ) - 1U );
const char shadowName[] = "TestShadowName";
uint16_t shadowNameLength  = ( sizeof( shadowName ) - 1U );
 
shadowStatus = Shadow_AssembleTopicString( ShadowTopicStringTypeUpdateDelta,
                                           thingName,
                                           thingNameLength,
                                           shadowName,
                                           shadowNameLength,
                                           & ( topicBuffer[ 0 ] ),
                                           bufferSize,
                                           & outLength );
 
if( shadowStatus == SHADOW_SUCCESS )
{
     // The assembled topic string is put in pTopicBuffer with the length outLength.
}

Shadow_MatchTopic()

ShadowStatus_t Shadow_MatchTopic	(	const char *	pTopic,
		uint16_t	topicLength,
		ShadowMessageType_t *	pMessageType,
		const char **	pThingName,
		uint16_t *	pThingNameLength
	)

Given the topic string of an incoming message, determine whether it is related to an unnamed ("Classic") device shadow; if it is, return information about the type of device shadow message, and a pointers to the Thing Name inside of the topic string. See ShadowMessageType_t for the list of message types. Those types correspond to Device Shadow Topics.

Deprecated:

Please use Shadow_MatchTopicString in new designs.

See Shadow_MatchTopicString for documentation of common behavior.