// Pure DDK support library routines; no kernel or module-wide state.

#include <ntlite/ddk/pci_caps.h>

KSTATUS NtlPciFindCapability(const NTL_PCI_CONFIG_READER* reader,
                             uint8_t firstOffset,
                             uint8_t capabilityId,
                             uint8_t* outOffset) {
    if (!reader || !reader->Read32 || !outOffset || !capabilityId)
        return NTLSTATUS_INVALID_PARAMETER;

    *outOffset = 0;
    uint8_t current = firstOffset;
    uint64_t visited = 0;

    while (current) {
        if (current < 0x40u || (current & 3u) != 0u)
            return NTLSTATUS_DEVICE_ERROR;

        uint64_t bit = 1ull << (current / 4u - 16u);
        if (visited & bit)
            return NTLSTATUS_DEVICE_ERROR;
        visited |= bit;

        uint32_t header = reader->Read32(reader->Context, current);
        if ((uint8_t)header == capabilityId) {
            *outOffset = current;
            return NTLSTATUS_SUCCESS;
        }
        current = (uint8_t)((header >> 8) & 0xFCu);
    }

    return NTLSTATUS_NOT_FOUND;
}