Function ImHashStr

src/imgui/imgui.cpp:2352–2388

Zero-terminated string hash, with support for ### to reset back to seed value We support a syntax of "label###id" where only "###id" is included in the hash, and only "label" gets displayed. Because this syntax is rarely used we are optimizing for the common case. - If we reach ### in the string we discard the hash so far and reset to the seed. - We don't do 'current += 2; continue;' after handlin

// - We don't do 'current += 2; continue;' after handling ### to keep the code smaller/faster (measured ~10% diff in Debug build)
// FIXME-OPT: Replace with e.g. FNV1a hash? CRC32 pretty much randomly access 1KB. Need to do proper measurements.
ImGuiID ImHashStr(const char* data_p, size_t data_size, ImGuiID seed)
{
    seed = ~seed;
    ImU32 crc = seed;
    const unsigned char* data = (const unsigned char*)data_p;
#ifndef IMGUI_ENABLE_SSE4_2_CRC
    const ImU32* crc32_lut = GCrc32LookupTable;
#endif
    if (data_size != 0)
    {
        while (data_size-- != 0)
        {
            unsigned char c = *data++;
            if (c == '#' && data_size >= 2 && data[0] == '#' && data[1] == '#')
                crc = seed;
#ifndef IMGUI_ENABLE_SSE4_2_CRC
            crc = (crc >> 8) ^ crc32_lut[(crc & 0xFF) ^ c];
#else
            crc = _mm_crc32_u8(crc, c);
#endif
        }
    }
    else
    {
        while (unsigned char c = *data++)
        {
            if (c == '#' && data[0] == '#' && data[1] == '#')
                crc = seed;
#ifndef IMGUI_ENABLE_SSE4_2_CRC
            crc = (crc >> 8) ^ crc32_lut[(crc & 0xFF) ^ c];
#else
            crc = _mm_crc32_u8(crc, c);
#endif
        }
    }
    return ~crc;
}

// Skip to the "###" marker if any. We don't skip past to match the behavior of GetID()
// FIXME-OPT: This is not designed to be optimal. Use with care.