diff --git a/src/helpers/nrf52/SerialBLEInterface.cpp b/src/helpers/nrf52/SerialBLEInterface.cpp index 5648707e6..a8b963cf3 100644 --- a/src/helpers/nrf52/SerialBLEInterface.cpp +++ b/src/helpers/nrf52/SerialBLEInterface.cpp @@ -22,6 +22,95 @@ // RX drain buffer size for overflow protection #define BLE_RX_DRAIN_BUF_SIZE 32 +// Maximum BLE device name length that fits in a scan response AD element. +// 31 (BLE_GAP_ADV_SET_DATA_SIZE_MAX) - 2 (AD length + type bytes) = 29 +#define BLE_NAME_MAX_LEN 29 + +static size_t utf8CharLen(uint8_t lead_byte) { + if (lead_byte < 0x80) return 1; + if ((lead_byte & 0xE0) == 0xC0) return 2; + if ((lead_byte & 0xF0) == 0xE0) return 3; + if ((lead_byte & 0xF8) == 0xF0) return 4; + return 1; // invalid lead byte — treat as single byte to avoid infinite loops +} + +// Build a BLE device name from prefix + node name, middle-truncating with +// ".." if the result would exceed BLE_NAME_MAX_LEN bytes. +// Truncation is UTF-8 safe and preserves the beginning and end of the name. +static void buildBLEName(char* dest, size_t dest_size, + const char* prefix, const char* name) +{ + size_t prefix_len = strlen(prefix); + size_t name_len = strlen(name); + + // Fast path: fits without truncation + if (prefix_len + name_len <= BLE_NAME_MAX_LEN) { + snprintf(dest, dest_size, "%s%s", prefix, name); + return; + } + + size_t name_budget = BLE_NAME_MAX_LEN - prefix_len; + const char sep[] = ".."; + const size_t sep_len = 2; + + // If budget is too small for meaningful middle-truncation (need at least + // 1 char + sep + 1 char), just take the head + if (name_budget <= sep_len + 2) { + memcpy(dest, prefix, prefix_len); + size_t i = 0; + while (i < name_budget && i < name_len) { + size_t cl = utf8CharLen((uint8_t)name[i]); + if (i + cl > name_budget) break; + i += cl; + } + memcpy(dest + prefix_len, name, i); + dest[prefix_len + i] = '\0'; + return; + } + + size_t content_budget = name_budget - sep_len; + size_t head_target = content_budget / 2; + size_t tail_target = content_budget - head_target; + + // Walk forward: collect head (complete UTF-8 characters up to head_target bytes) + size_t head_len = 0; + { + size_t i = 0; + while (i < name_len) { + size_t cl = utf8CharLen((uint8_t)name[i]); + if (i + cl > head_target) break; + i += cl; + } + head_len = i; + } + + // Walk backward: collect tail (complete UTF-8 characters up to tail_target bytes) + size_t tail_start = name_len; + size_t tail_len = 0; + { + size_t i = name_len; + while (i > 0 && tail_len < tail_target) { + // Find start of previous UTF-8 character + size_t prev = i - 1; + while (prev > 0 && ((uint8_t)name[prev] & 0xC0) == 0x80) + prev--; + size_t cl = i - prev; + if (tail_len + cl > tail_target) break; + tail_len += cl; + i = prev; + } + tail_start = name_len - tail_len; + } + + // Assemble: prefix + head + ".." + tail + size_t pos = 0; + memcpy(dest + pos, prefix, prefix_len); pos += prefix_len; + memcpy(dest + pos, name, head_len); pos += head_len; + memcpy(dest + pos, sep, sep_len); pos += sep_len; + memcpy(dest + pos, name + tail_start, tail_len); pos += tail_len; + dest[pos] = '\0'; +} + static SerialBLEInterface* instance = nullptr; void SerialBLEInterface::onConnect(uint16_t connection_handle) { @@ -133,8 +222,8 @@ void SerialBLEInterface::begin(const char* prefix, char* name, uint32_t pin_code // Bluefruit.autoConnLed(false); Bluefruit.configPrphBandwidth(BANDWIDTH_MAX); Bluefruit.begin(); - - char dev_name[32+16]; + + // Resolve "@@MAC" now that the SoftDevice is active if (strcmp(name, "@@MAC") == 0) { ble_gap_addr_t addr; if (sd_ble_gap_addr_get(&addr) == NRF_SUCCESS) { @@ -142,7 +231,11 @@ void SerialBLEInterface::begin(const char* prefix, char* name, uint32_t pin_code addr.addr[5], addr.addr[4], addr.addr[3], addr.addr[2], addr.addr[1], addr.addr[0]); } } - sprintf(dev_name, "%s%s", prefix, name); + + // Build the BLE name with middle-truncation if needed to fit within the + // SoftDevice's default 31-byte GAP name limit and 29-byte scan response limit + char dev_name[32+16]; + buildBLEName(dev_name, sizeof(dev_name), prefix, name); // Connection interval units: 1.25ms, supervision timeout units: 10ms ble_gap_conn_params_t ppcp_params;