feat: add attribute protocol errors by acouvreur · Pull Request #421 · tinygo-org/bluetooth

acouvreur · 2026-03-16T23:24:20Z

This will allow to return protocol level errors

My goal is to add support for error code extraction from returned errors.

Especially in windows where you only get the async result code (aborted or failure).

I have tested the extraction of the attribute protocol error code successfully but the code is not included in this pull request because it required changes in the winrt-go library.

The errors have been implemented from https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-54/out/en/host/attribute-protocol--att-.html#UUID-eefd3e8d-9b16-3af8-1fb4-fa90f52262e8

Wether or not we actually use them in the code, I thing they are useful just like the generated services and characteristics UUIDs in this repo

This will allow to return protocol level errors

This will be used to retrieve the error details from an error within a AsyncOperationCompletedHandler. Related work: tinygo-org/bluetooth#421

acouvreur · 2026-03-17T00:13:33Z

Note that:

Easy to link with CBGO: https://github.com/tinygo-org/cbgo/blob/f065ac076d9e72deb211ac5caf03591e6e482d19/att.go#L23-L42
Will be linked in windows when feat: generate IAsyncInfo saltosystems/winrt-go#118 is merged I will be able to get the attribute protocol error code

errors.go

FilipVranesevic · 2026-03-17T08:45:39Z

errors.go

+}
+
+func (e *AttributeProtocolError) Error() string {
+	return fmt.Sprintf("ATT error 0x%02X (%s): %s", e.Code, e.Name, e.Description)


fmt on embedded targets can increase the binary size significantly. strings.Builder and hex.EncodeToString would be much more efficient.

Suggested change

return fmt.Sprintf("ATT error 0x%02X (%s): %s", e.Code, e.Name, e.Description)

b := strings.Builder{}

b.WriteString("ATT error 0x")

b.WriteString(hex.EncodeToString([]byte{e.Code}))

b.WriteString(" (")

b.WriteString(e.Name)

b.WriteString("): ")

b.WriteString(e.Description)

return b.String()

it does not look pretty, but the code size and allocation count difference is significant:

strings.Builder

tinygo build -print-allocs=. -size short -target nicenano ./test/main.go:24.1,24.23 1 0 ./tinygo/src/runtime/string.go:76.1,76.45 1 0 ./tinygo/src/runtime/baremetal.go:44.1,44.24 1 0 ./tinygo/src/runtime/slice.go:39.1,39.38 1 0 ./tinygo/src/internal/task/task_stack.go:43.1,43.39 1 0 ./tinygo/src/internal/task/task_stack.go:75.1,75.13 1 0 code data bss | flash ram 7296 116 4736 | 7412 4852

fmt.Sprintf

tinygo build -print-allocs=. -size short -target nicenano test/main.go:36.1,36.54 1 0 test/main.go:34.1,34.19 1 0 test/main.go:24.1,24.79 1 0 test/main.go:25.1,25.23 1 0 test/main.go:24.1,24.79 1 0 test/main.go:24.1,24.79 1 0 /usr/local/go/src/fmt/print.go:509.1,509.63 1 0 /usr/local/go/src/fmt/print.go:881.1,881.34 1 0 /usr/local/go/src/fmt/format.go:539.1,539.21 1 0 /usr/local/go/src/fmt/format.go:211.1,211.28 1 0 /usr/local/go/src/fmt/format.go:150.1,150.28 1 0 /usr/local/go/src/fmt/format.go:75.1,75.34 1 0 /usr/local/go/src/fmt/print.go:147.1,147.36 1 0 /usr/local/go/src/strconv/ftoa.go:287.1,287.22 1 0 /usr/local/go/src/strconv/ftoa.go:268.1,268.22 1 0 /usr/local/go/src/strconv/ftoa.go:166.1,166.18 1 0 /usr/local/go/src/strconv/ftoa.go:147.1,147.18 1 0 /usr/local/go/src/strconv/ftoa.go:119.1,119.18 1 0 /usr/local/go/src/strconv/quote.go:35.1,35.53 1 0 /usr/local/go/src/internal/fmtsort/sort.go:134.1,134.49 1 0 /usr/local/go/src/internal/fmtsort/sort.go:57.1,57.32 1 0 tinygo/src/runtime/string.go:76.1,76.45 1 0 tinygo/src/runtime/string.go:63.1,63.47 1 0 tinygo/src/runtime/hashmap.go:49.1,49.44 1 0 tinygo/src/runtime/baremetal.go:44.1,44.24 1 0 tinygo/src/runtime/slice.go:39.1,39.38 1 0 tinygo/src/internal/reflectlite/strconv.go:239.1,239.35 1 0 tinygo/src/internal/reflectlite/type.go:418.1,418.22 1 0 tinygo/src/internal/reflectlite/value.go:1751.1,1751.35 1 0 tinygo/src/internal/reflectlite/value.go:882.1,882.53 1 0 tinygo/src/internal/reflectlite/value.go:875.1,875.52 1 0 tinygo/src/internal/reflectlite/value.go:273.1,273.61 1 0 tinygo/src/internal/reflectlite/value.go:247.1,247.53 1 0 tinygo/src/internal/reflectlite/value.go:1041.1,1041.53 1 0 tinygo/src/internal/reflectlite/value.go:806.1,806.51 1 0 tinygo/src/internal/reflectlite/value.go:441.1,441.52 1 0 tinygo/src/internal/reflectlite/value.go:650.1,650.54 1 0 tinygo/src/internal/reflectlite/value.go:658.1,658.54 1 0 tinygo/src/internal/reflectlite/value.go:667.1,667.52 1 0 tinygo/src/internal/reflectlite/value.go:598.1,598.53 1 0 tinygo/src/internal/reflectlite/value.go:541.1,541.52 1 0 tinygo/src/internal/reflectlite/value.go:488.1,488.51 1 0 tinygo/src/internal/reflectlite/value.go:630.1,630.55 1 0 tinygo/src/internal/reflectlite/value.go:1163.1,1163.19 1 0 tinygo/src/internal/reflectlite/value.go:1218.1,1218.56 1 0 tinygo/src/internal/task/task_stack.go:43.1,43.39 1 0 tinygo/src/internal/task/task_stack.go:75.1,75.13 1 0 code data bss | flash ram 55288 1508 4744 | 56796 6252

I did not know that, should we add golangci lint with a rule for fmt ?

FilipVranesevic · 2026-03-17T09:33:35Z

errors.go

+	// Name is a short identifier for the error.
+	Name string
+	// Description is the human-readable description from the spec.
+	Description string
+}
+
+func (e *AttributeProtocolError) Error() string {
+	return fmt.Sprintf("ATT error 0x%02X (%s): %s", e.Code, e.Name, e.Description)
+}
+
+// ATT error codes from the Bluetooth Core Specification, Table 3.4.
+var (
+	ErrAttInvalidHandle              = &AttributeProtocolError{0x01, "Invalid Handle", "The attribute handle given was not valid on this server."}
+	ErrAttReadNotPermitted           = &AttributeProtocolError{0x02, "Read Not Permitted", "The attribute cannot be read."}
+	ErrAttWriteNotPermitted          = &AttributeProtocolError{0x03, "Write Not Permitted", "The attribute cannot be written."}
+	ErrAttInvalidPDU                 = &AttributeProtocolError{0x04, "Invalid PDU", "The attribute PDU was invalid."}
+	ErrAttInsufficientAuthentication = &AttributeProtocolError{0x05, "Insufficient Authentication", "The attribute requires authentication before it can be read or written."}
+	ErrAttRequestNotSupported        = &AttributeProtocolError{0x06, "Request Not Supported", "ATT Server does not support the request received from the client."}
+	ErrAttInvalidOffset              = &AttributeProtocolError{0x07, "Invalid Offset", "Offset specified was past the end of the attribute."}
+	ErrAttInsufficientAuthorization  = &AttributeProtocolError{0x08, "Insufficient Authorization", "The attribute requires authorization before it can be read or written."}
+	ErrAttPrepareQueueFull           = &AttributeProtocolError{0x09, "Prepare Queue Full", "Too many prepare writes have been queued."}
+	ErrAttNotFound                   = &AttributeProtocolError{0x0A, "Attribute Not Found", "No attribute found within the given attribute handle range."}
+	ErrAttNotLong                    = &AttributeProtocolError{0x0B, "Attribute Not Long", "The attribute cannot be read using the ATT_READ_BLOB_REQ PDU."}
+	ErrAttInsufficientEncKeySize     = &AttributeProtocolError{0x0C, "Encryption Key Size Too Short", "The Encryption Key Size used for encrypting this link is too short."}
+	ErrAttInvalidLength              = &AttributeProtocolError{0x0D, "Invalid Attribute Value Length", "The attribute value length is invalid for the operation."}
+	ErrAttUnlikelyError              = &AttributeProtocolError{0x0E, "Unlikely Error", "The attribute request that was requested has encountered an error that was unlikely, and therefore could not be completed as requested."}
+	ErrAttInsufficientEncryption     = &AttributeProtocolError{0x0F, "Insufficient Encryption", "The attribute requires encryption before it can be read or written."}
+	ErrAttUnsupportedGroupType       = &AttributeProtocolError{0x10, "Unsupported Group Type", "The attribute type is not a supported grouping attribute as defined by a higher layer specification."}
+	ErrAttInsufficientResources      = &AttributeProtocolError{0x11, "Insufficient Resources", "Insufficient Resources to complete the request."}
+	ErrAttOutOfSync                  = &AttributeProtocolError{0x12, "Database Out Of Sync", "The server requests the client to rediscover the database."}
+	ErrAttValueNotAllowed            = &AttributeProtocolError{0x13, "Value Not Allowed", "The attribute parameter value was not allowed."}
+)
+
+// attErrorsByCode maps ATT error codes to their predefined error values.
+var attErrorsByCode = map[uint8]*AttributeProtocolError{
+	0x01: ErrAttInvalidHandle,
+	0x02: ErrAttReadNotPermitted,
+	0x03: ErrAttWriteNotPermitted,


having global exported variables like this can potentially lead to issues if for example somewhere in the user code these variables were unintentionally mutated.

Maybe the code could be the error type which could be const:

type AttributeProtocolError uint8 const ( ErrAttInvalidHandle = AttributeProtocolError(0x01) ErrAttReadNotPermitted = AttributeProtocolError(0x02) ErrAttWriteNotPermitted = AttributeProtocolError(0x03) ... )

Then have a map from error code to error details:

type errorDetails struct { // name is a short identifier for the error. name string // description is the human-readable description from the spec. description string } // this map can also potentially be a slice var attErrorDetails = map[AttributeProtocolError]errorDetails{ ErrAttInvalidHandle: errorDetails{"Invalid Handle", "The attribute handle given was not valid on this server."}, ErrAttReadNotPermitted: errorDetails{"Read Not Permitted", "The attribute cannot be read."}, ErrAttWriteNotPermitted: errorDetails{"Write Not Permitted", "The attribute cannot be written."}, ... } func detailsFromCode(code AttributeProtocolError) errorDetails { if err, ok := attErrorDetails[code]; ok { return err } ... }

If Name and Description need to be exposed directly, they could be methods on AttributeProtocolError

acouvreur · 2026-03-17T12:42:17Z

@deadprogram @FilipVranesevic

I have removed all fmt usage
I have changed the error to a tyupe uint8
All protocol errors are const
The user can retrieve the error details using Name(), Descriptio() which calls the private function details()

I don't really like the fact that those helper methods must do a map lookup everytime, even though it is a very small map.

What do you think ? Is there some optimization to do ?

Cache the attErrorDetails result
Make the attErrorDetails a pointer to avoid recreating / copying the details everytime ?

This will be used to retrieve the error details from an error within a AsyncOperationCompletedHandler. Related work: tinygo-org/bluetooth#421

feat: add attribute protocol errors

90bfca0

This will allow to return protocol level errors

acouvreur added a commit to acouvreur/winrt-go that referenced this pull request Mar 17, 2026

feat: generate IAsyncInfo

cde2031

This will be used to retrieve the error details from an error within a AsyncOperationCompletedHandler. Related work: tinygo-org/bluetooth#421

acouvreur mentioned this pull request Mar 17, 2026

feat: generate IAsyncInfo saltosystems/winrt-go#118

Merged

deadprogram reviewed Mar 17, 2026

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FilipVranesevic reviewed Mar 17, 2026

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code review

4e7beb9

HattoriHanzo031 approved these changes Mar 17, 2026

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acouvreur added a commit to acouvreur/winrt-go that referenced this pull request Mar 17, 2026

feat: generate IAsyncInfo

d8db2a6

This will be used to retrieve the error details from an error within a AsyncOperationCompletedHandler. Related work: tinygo-org/bluetooth#421

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feat: add attribute protocol errors#421

feat: add attribute protocol errors#421
acouvreur wants to merge 2 commits intotinygo-org:devfrom
acouvreur:add-ble-errors-codes

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-	return fmt.Sprintf("ATT error 0x%02X (%s): %s", e.Code, e.Name, e.Description)
+	b := strings.Builder{}
+	b.WriteString("ATT error 0x")
+	b.WriteString(hex.EncodeToString([]byte{e.Code}))
+	b.WriteString(" (")
+	b.WriteString(e.Name)
+	b.WriteString("): ")
+	b.WriteString(e.Description)
+	return b.String()

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