Add GATT Peripheral example for ESP32

esp32-ble-peripheral-sdk/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.29)
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(main)

esp32-ble-peripheral-sdk/README.md

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+# esp32-ble-peripheral-sdk
+
+This example demonstrates how to integrate with the ESP-IDF SDK via CMake and how to use the the SDK to advertise as a Bluetooth iBeacon from Swift. This example is specifically made for the RISC-V MCUs from ESP32 (the Xtensa MCUs are not currently supported by Swift).
+
+## Requirements
+
+- Set up the [ESP-IDF](https://docs.espressif.com/projects/esp-idf/en/stable/esp32/) development environment. Follow the steps in the [ESP32-C6 "Get Started" guide](https://docs.espressif.com/projects/esp-idf/en/v5.2/esp32c6/get-started/index.html).
+  - Make sure you specifically set up development for the RISC-V ESP32-C6, and not the Xtensa based products.
+
+- Before trying to use Swift with the ESP-IDF SDK, make sure your environment works and can build the provided C/C++ sample projects, in particular:
+  - Try building and running the "get-started/blink" example from ESP-IDF written in C.
+
+## Building
+
+- Make sure you have a recent nightly Swift toolchain that has Embedded Swift support.
+- If needed, run export.sh to get access to the idf.py script from ESP-IDF.
+- Specify the nightly toolchain to be used via the `TOOLCHAINS` environment variable and the target board type by using `idf.py set-target`.
+``` console
+$ cd esp32-ble-peripheral-sdk
+$ export TOOLCHAINS=...
+$ . <path-to-esp-idf>/export.sh
+$ idf.py set-target esp32c6
+$ idf.py build
+```
+
+## Running
+
+- Connect the Esp32-C6-Bug board over a USB cable to your Mac. Alternatively you can just connect external LED to GPIO pin 8 on any other board.
+- Connect RX pin of USB-UART converter to TX0 pin of your board if you need serial ouput. You may also need to connect GND converter pin to the GND pin of the board.
+- Use `idf.py` to upload the firmware and to run it:
+
+```console
+$ idf.py flash
+```
+
+- Find the peripheral advertised as `ESP32-C6 XX:XX:XX:XX:XX:XX` in a Bluetooth scanner app like LightBlue or nRF Connect. 
+
+![LightBlue](assets/images/lightblue.jpg)
+![nRF Connect](assets/images/nrfconnect.jpg)

esp32-ble-peripheral-sdk/main/ATTAttributePermissions.swift

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+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift project authors.
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+/// ATT attribute permission bitfield values. Permissions are grouped as
+/// "Access", "Encryption", "Authentication", and "Authorization". A bitmask of
+/// permissions is a byte that encodes a combination of these.
+@frozen
+public struct ATTAttributePermissions: OptionSet, Equatable, Hashable, Sendable {
+
+    public var rawValue: UInt8
+
+    public init(rawValue: UInt8) {
+        self.rawValue = rawValue
+    }
+}
+
+// MARK: - ExpressibleByIntegerLiteral
+
+extension ATTAttributePermissions: ExpressibleByIntegerLiteral {
+
+    public init(integerLiteral value: UInt8) {
+        self.rawValue = value
+    }
+}
+
+// MARK: - CustomStringConvertible
+
+extension ATTAttributePermissions: CustomStringConvertible, CustomDebugStringConvertible {
+
+    public var description: String {
+        "0x" + rawValue.toHexadecimal()
+    }
+
+    /// A textual representation of the file permissions, suitable for debugging.
+    public var debugDescription: String { self.description }
+}
+
+// MARK: - Options
+
+public extension ATTAttributePermissions {
+
+    // Access
+    static var read: ATTAttributePermissions                     { 0x01 }
+    static var write: ATTAttributePermissions                    { 0x02 }
+
+    // Encryption
+    static var encrypt: ATTAttributePermissions                  { [.readEncrypt, .writeEncrypt] }
+    static var readEncrypt: ATTAttributePermissions              { 0x04 }
+    static var writeEncrypt: ATTAttributePermissions             { 0x08 }
+
+    // The following have no effect on Darwin
+
+    // Authentication
+    static var authentication: ATTAttributePermissions           { [.readAuthentication, .writeAuthentication] }
+    static var readAuthentication: ATTAttributePermissions       { 0x10 }
+    static var writeAuthentication: ATTAttributePermissions      { 0x20 }
+
+    // Authorization
+    static var authorized: ATTAttributePermissions               { 0x40 }
+    static var noAuthorization: ATTAttributePermissions          { 0x80 }
+}

esp32-ble-peripheral-sdk/main/ATTError.swift

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+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift project authors.
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+/**
+ The possible errors returned by a GATT server (a remote peripheral) during Bluetooth low energy ATT transactions.
+
+ These error constants are based on the Bluetooth ATT error codes, defined in the Bluetooth 4.0 specification.
+ For more information about these errors, see the Bluetooth 4.0 specification, Volume 3, Part F, Section 3.4.1.1.
+ */
+@frozen
+public enum ATTError: UInt8, Error {
+
+    /// Invalid Handle
+    ///
+    /// The attribute handle given was not valid on this server.
+    case invalidHandle                              = 0x01
+
+    /// Read Not Permitted
+    ///
+    /// The attribute cannot be read.
+    case readNotPermitted                           = 0x02
+
+    /// Write Not Permitted
+    ///
+    /// The attribute cannot be written.
+    case writeNotPermitted                          = 0x03
+
+    /// Invalid PDU
+    ///
+    /// The attribute PDU was invalid.
+    case invalidPDU                                 = 0x04
+
+    /// Insufficient Authentication
+    ///
+    /// The attribute requires authentication before it can be read or written.
+    case insufficientAuthentication                 = 0x05
+
+    /// Request Not Supported
+    ///
+    /// Attribute server does not support the request received from the client.
+    case requestNotSupported                        = 0x06
+
+    /// Invalid Offset
+    ///
+    /// Offset specified was past the end of the attribute.
+    case invalidOffset                              = 0x07
+
+    /// Insufficient Authorization
+    ///
+    /// The attribute requires authorization before it can be read or written.
+    case insufficientAuthorization                  = 0x08
+
+    /// Prepare Queue Full
+    ///
+    /// Too many prepare writes have been queued.
+    case prepareQueueFull                           = 0x09
+
+    /// Attribute Not Found
+    ///
+    /// No attribute found within the given attribute handle range.
+    case attributeNotFound                          = 0x0A
+
+    /// Attribute Not Long
+    ///
+    /// The attribute cannot be read or written using the *Read Blob Request*.
+    case attributeNotLong                           = 0x0B
+
+    /// Insufficient Encryption Key Size
+    ///
+    /// The *Encryption Key Size* used for encrypting this link is insufficient.
+    case insufficientEncryptionKeySize              = 0x0C
+
+    /// Invalid Attribute Value Length
+    ///
+    /// The attribute value length is invalid for the operation.
+    case invalidAttributeValueLength                = 0x0D
+
+    /// Unlikely Error
+    ///
+    /// The attribute request that was requested has encountered an error that was unlikely,
+    /// and therefore could not be completed as requested.
+    case unlikelyError                              = 0x0E
+
+    /// Insufficient Encryption
+    ///
+    /// The attribute requires encryption before it can be read or written.
+    case insufficientEncryption                     = 0x0F
+
+    /// Unsupported Group Type
+    ///
+    /// The attribute type is not a supported grouping attribute as defined by a higher layer specification.
+    case unsupportedGroupType                       = 0x10
+
+    /// Insufficient Resources
+    ///
+    /// Insufficient Resources to complete the request.
+    case insufficientResources                      = 0x11
+}
+
+// MARK: - CustomStringConvertible
+
+extension ATTError: CustomStringConvertible {
+
+    public var description: String {
+        return name
+    }
+}
+
+// MARK: - Description Values
+
+public extension ATTError {
+
+    var name: String {
+
+        switch self {
+        case .invalidHandle:
+            return "Invalid Handle"
+        case .readNotPermitted:
+            return "Read Not Permitted"
+        case .writeNotPermitted:
+            return "Write Not Permitted"
+        case .invalidPDU:
+            return "Invalid PDU"
+        case .insufficientAuthentication:
+            return "Insufficient Authentication"
+        case .requestNotSupported:
+            return "Request Not Supported"
+        case .invalidOffset:
+            return "Invalid Offset"
+        case .insufficientAuthorization:
+            return "Insufficient Authorization"
+        case .prepareQueueFull:
+            return "Prepare Queue Full"
+        case .attributeNotFound:
+            return "Attribute Not Found"
+        case .attributeNotLong:
+            return "Attribute Not Long"
+        case .insufficientEncryptionKeySize:
+            return "Insufficient Encryption Key Size"
+        case .invalidAttributeValueLength:
+            return "Invalid Attribute Value Length"
+        case .unlikelyError:
+            return "Unlikely Error"
+        case .insufficientEncryption:
+            return "Insufficient Encryption"
+        case .unsupportedGroupType:
+            return "Unsupported Group Type"
+        case .insufficientResources:
+            return "Insufficient Resources"
+        }
+    }
+
+    #if !hasFeature(Embedded)
+    var errorDescription: String {
+
+        switch self {
+        case .invalidHandle:
+            return "The attribute handle given was not valid on this server."
+        case .readNotPermitted:
+            return "The attribute cannot be read."
+        case .writeNotPermitted:
+            return "The attribute cannot be written."
+        case .invalidPDU:
+            return "The attribute PDU was invalid."
+        case .insufficientAuthentication:
+            return "The attribute requires authentication before it can be read or written."
+        case .requestNotSupported:
+            return "Attribute server does not support the request received from the client."
+        case .invalidOffset:
+            return "Offset specified was past the end of the attribute."
+        case .insufficientAuthorization:
+            return "The attribute requires authorization before it can be read or written."
+        case .prepareQueueFull:
+            return "Too many prepare writes have been queued."
+        case .attributeNotFound:
+            return "No attribute found within the given attri- bute handle range."
+        case .attributeNotLong:
+            return "The attribute cannot be read using the Read Blob Request."
+        case .insufficientEncryptionKeySize:
+            return "The Encryption Key Size used for encrypting this link is insufficient."
+        case .invalidAttributeValueLength:
+            return "The attribute value length is invalid for the operation."
+        case .unlikelyError:
+            return "The attribute request that was requested has encountered an error that was unlikely, and therefore could not be completed as requested."
+        case .insufficientEncryption:
+            return "The attribute requires encryption before it can be read or written."
+        case .unsupportedGroupType:
+            return "The attribute type is not a supported grouping attribute as defined by a higher layer specification."
+        case .insufficientResources:
+            return "Insufficient Resources to complete the request."
+        }
+    }
+    #endif
+}
+
+// MARK: - CustomNSError
+
+#if canImport(Foundation)
+extension ATTError: CustomNSError {
+
+    public static var errorDomain: String {
+        return "org.pureswift.Bluetooth.ATTError"
+    }
+
+    public var errorCode: Int {
+        return Int(rawValue)
+    }
+
+    public var errorUserInfo: [String: Any] {
+
+        return [
+            NSLocalizedDescriptionKey: name,
+            NSLocalizedFailureReasonErrorKey: errorDescription
+        ]
+    }
+}
+#endif