assimp/code/glTF/glTFCommon.cpp

/*
Open Asset Import Library (assimp)
----------------------------------------------------------------------

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* Redistributions in binary form must reproduce the above
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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*/
#include "glTF/glTFCommon.h"

namespace glTFCommon {

using namespace glTFCommon::Util;

namespace Util {

size_t DecodeBase64(const char *in, size_t inLength, uint8_t *&out) {
    ai_assert(inLength % 4 == 0);

    if (inLength < 4) {
        out = 0;
        return 0;
    }

    int nEquals = int(in[inLength - 1] == '=') +
                  int(in[inLength - 2] == '=');

    size_t outLength = (inLength * 3) / 4 - nEquals;
    out = new uint8_t[outLength];
    memset(out, 0, outLength);

    size_t i, j = 0;

    for (i = 0; i + 4 < inLength; i += 4) {
        uint8_t b0 = DecodeCharBase64(in[i]);
        uint8_t b1 = DecodeCharBase64(in[i + 1]);
        uint8_t b2 = DecodeCharBase64(in[i + 2]);
        uint8_t b3 = DecodeCharBase64(in[i + 3]);

        out[j++] = (uint8_t)((b0 << 2) | (b1 >> 4));
        out[j++] = (uint8_t)((b1 << 4) | (b2 >> 2));
        out[j++] = (uint8_t)((b2 << 6) | b3);
    }

    {
        uint8_t b0 = DecodeCharBase64(in[i]);
        uint8_t b1 = DecodeCharBase64(in[i + 1]);
        uint8_t b2 = DecodeCharBase64(in[i + 2]);
        uint8_t b3 = DecodeCharBase64(in[i + 3]);

        out[j++] = (uint8_t)((b0 << 2) | (b1 >> 4));
        if (b2 < 64) out[j++] = (uint8_t)((b1 << 4) | (b2 >> 2));
        if (b3 < 64) out[j++] = (uint8_t)((b2 << 6) | b3);
    }

    return outLength;
}

void EncodeBase64(const uint8_t *in, size_t inLength, std::string &out) {
    size_t outLength = ((inLength + 2) / 3) * 4;

    size_t j = out.size();
    out.resize(j + outLength);

    for (size_t i = 0; i < inLength; i += 3) {
        uint8_t b = (in[i] & 0xFC) >> 2;
        out[j++] = EncodeCharBase64(b);

        b = (in[i] & 0x03) << 4;
        if (i + 1 < inLength) {
            b |= (in[i + 1] & 0xF0) >> 4;
            out[j++] = EncodeCharBase64(b);

            b = (in[i + 1] & 0x0F) << 2;
            if (i + 2 < inLength) {
                b |= (in[i + 2] & 0xC0) >> 6;
                out[j++] = EncodeCharBase64(b);

                b = in[i + 2] & 0x3F;
                out[j++] = EncodeCharBase64(b);
            } else {
                out[j++] = EncodeCharBase64(b);
                out[j++] = '=';
            }
        } else {
            out[j++] = EncodeCharBase64(b);
            out[j++] = '=';
            out[j++] = '=';
        }
    }
}

bool ParseDataURI(const char *const_uri, size_t uriLen, DataURI &out) {
    if (nullptr == const_uri) {
        return false;
    }

    if (const_uri[0] != 0x10) { // we already parsed this uri?
        if (strncmp(const_uri, "data:", 5) != 0) // not a data uri?
            return false;
    }

    // set defaults
    out.mediaType = "text/plain";
    out.charset = "US-ASCII";
    out.base64 = false;

    char *uri = const_cast<char *>(const_uri);
    if (uri[0] != 0x10) {
        uri[0] = 0x10;
        uri[1] = uri[2] = uri[3] = uri[4] = 0;

        size_t i = 5, j;
        if (uri[i] != ';' && uri[i] != ',') { // has media type?
            uri[1] = char(i);
            for (;i < uriLen && uri[i] != ';' && uri[i] != ','; ++i) {
                // nothing to do!
            }
        }
        while (i < uriLen && uri[i] == ';') {
            uri[i++] = '\0';
            for (j = i; i < uriLen && uri[i] != ';' && uri[i] != ','; ++i) {
                // nothing to do!
            }

            if (strncmp(uri + j, "charset=", 8) == 0) {
                uri[2] = char(j + 8);
            } else if (strncmp(uri + j, "base64", 6) == 0) {
                uri[3] = char(j);
            }
        }
        if (i < uriLen) {
            uri[i++] = '\0';
            uri[4] = char(i);
        } else {
            uri[1] = uri[2] = uri[3] = 0;
            uri[4] = 5;
        }
    }

    if (uri[1] != 0) {
        out.mediaType = uri + uri[1];
    }
    if (uri[2] != 0) {
        out.charset = uri + uri[2];
    }
    if (uri[3] != 0) {
        out.base64 = true;
    }
    out.data = uri + uri[4];
    out.dataLength = (uri + uriLen) - out.data;

    return true;
}

} // namespace Util
} // namespace glTFCommon