Function ImHashData

src/imgui/imgui.cpp:2324–2344

Known size hash It is ok to call ImHashData on a string with known length but the ### operator won't be supported. FIXME-OPT: Replace with e.g. FNV1a hash? CRC32 pretty much randomly access 1KB. Need to do proper measurements.

// It is ok to call ImHashData on a string with known length but the ### operator won't be supported.
// FIXME-OPT: Replace with e.g. FNV1a hash? CRC32 pretty much randomly access 1KB. Need to do proper measurements.
ImGuiID ImHashData(const void* data_p, size_t data_size, ImGuiID seed)
{
    ImU32 crc = ~seed;
    const unsigned char* data = (const unsigned char*)data_p;
    const unsigned char *data_end = (const unsigned char*)data_p + data_size;
#ifndef IMGUI_ENABLE_SSE4_2_CRC
    const ImU32* crc32_lut = GCrc32LookupTable;
    while (data < data_end)
        crc = (crc >> 8) ^ crc32_lut[(crc & 0xFF) ^ *data++];
    return ~crc;
#else
    while (data + 4 <= data_end)
    {
        crc = _mm_crc32_u32(crc, *(ImU32*)data);
        data += 4;
    }
    while (data < data_end)
        crc = _mm_crc32_u8(crc, *data++);
    return ~crc;
#endif
}

// 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.