Function ImHashStr

Dependencies/ImGui/src/imgui.cpp:2501–2546

Zero-terminated string hash, with support for ### to reset back to seed value. e.g. "label###id" outputs the same hash as "id" (and "label" is generally displayed by the UI functions) FIXME-OPT: Replace with e.g. FNV1a hash? CRC32 pretty much randomly access 1KB. Need to do proper measurements.

// e.g. "label###id" outputs the same hash as "id" (and "label" is generally displayed by the UI functions)
// 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;
                data += 2;
                data_size -= 2;
                continue;
            }
#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;
                data += 2;
                continue;
            }
#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.