JD2022-TU1/main/extern/libwebm/custom/mkvparser/ebmlreadhelpers.cpp

#include "ebmlreadhelpers.hpp"
#include "imkvreader.hpp"
#include "memory.hpp"

#include <stddef.h>
#include <assert.h>
#include <limits.h>

namespace mkvparser
{

long long ReadUInt(IMkvReader* pReader, long long pos, long& len)
{
    assert(pReader);
    assert(pos >= 0);

    int status;

//#ifdef _DEBUG
//    long long total, available;
//    status = pReader->Length(&total, &available);
//    assert(status >= 0);
//    assert((total < 0) || (available <= total));
//    assert(pos < available);
//    assert((available - pos) >= 1);  //assume here max u-int len is 8
//#endif

    len = 1;

    unsigned char b;

    status = pReader->Read(pos, 1, &b);

    if (status < 0)  //error or underflow
        return status;

    if (status > 0)  //interpreted as "underflow"
        return E_BUFFER_NOT_FULL;

    if (b == 0)  //we can't handle u-int values larger than 8 bytes
        return E_FILE_FORMAT_INVALID;

    unsigned char m = 0x80;

    while (!(b & m))
    {
        m >>= 1;
        ++len;
    }

//#ifdef _DEBUG
//    assert((available - pos) >= len);
//#endif

    long long result = b & (~m);
    ++pos;

    for (int i = 1; i < len; ++i)
    {
        status = pReader->Read(pos, 1, &b);

        if (status < 0)
        {
            len = 1;
            return status;
        }

        if (status > 0)
        {
            len = 1;
            return E_BUFFER_NOT_FULL;
        }

        result <<= 8;
        result |= b;

        ++pos;
    }

    return result;
}

long long GetUIntLength(
    IMkvReader* pReader,
    long long pos,
    long& len)
{
    assert(pReader);
    assert(pos >= 0);

    long long total, available;

    int status = pReader->Length(&total, &available);
    assert(status >= 0);
    assert((total < 0) || (available <= total));

    len = 1;

    if (pos >= available)
        return pos;  //too few bytes available

    unsigned char b;

    status = pReader->Read(pos, 1, &b);

    if (status < 0)
        return status;

    assert(status == 0);

    if (b == 0)  //we can't handle u-int values larger than 8 bytes
        return E_FILE_FORMAT_INVALID;

    unsigned char m = 0x80;

    while (!(b & m))
    {
        m >>= 1;
        ++len;
    }

    return 0;  //success
}


long long UnserializeUInt(
    IMkvReader* pReader,
    long long pos,
    long long size)
{
    assert(pReader);
    assert(pos >= 0);

    if ((size <= 0) || (size > 8))
        return E_FILE_FORMAT_INVALID;

    long long result = 0;

    for (long long i = 0; i < size; ++i)
    {
        unsigned char b;

        const long status = pReader->Read(pos, 1, &b);

        if (status < 0)
            return status;

        result <<= 8;
        result |= b;

        ++pos;
    }

    return result;
}


long UnserializeFloat(
    IMkvReader* pReader,
    long long pos,
    long long size_,
    double& result)
{
    assert(pReader);
    assert(pos >= 0);

    if ((size_ != 4) && (size_ != 8))
        return E_FILE_FORMAT_INVALID;

    const long size = static_cast<long>(size_);

    unsigned char buf[8];

    const int status = pReader->Read(pos, size, buf);

    if (status < 0)  //error
        return status;

    if (size == 4)
    {
        union
        {
            float f;
            unsigned long ff;
        };

        ff = 0;

        for (int i = 0;;)
        {
            ff |= buf[i];

            if (++i >= 4)
                break;

            ff <<= 8;
        }

        result = f;
    }
    else
    {
        assert(size == 8);

        union
        {
            double d;
            unsigned long long dd;
        };

        dd = 0;

        for (int i = 0;;)
        {
            dd |= buf[i];

            if (++i >= 8)
                break;

            dd <<= 8;
        }

        result = d;
    }

    return 0;
}


long UnserializeInt(
    IMkvReader* pReader,
    long long pos,
    long size,
    long long& result)
{
    assert(pReader);
    assert(pos >= 0);
    assert(size > 0);
    assert(size <= 8);

    {
        signed char b;

        const long status = pReader->Read(pos, 1, (unsigned char*)&b);

        if (status < 0)
            return status;

        result = b;

        ++pos;
    }

    for (long i = 1; i < size; ++i)
    {
        unsigned char b;

        const long status = pReader->Read(pos, 1, &b);

        if (status < 0)
            return status;

        result <<= 8;
        result |= b;

        ++pos;
    }

    return 0;  //success
}


long UnserializeString(
    IMkvReader* pReader,
    long long pos,
    long long size_,
    char*& str)
{
    mem::Free(str);
    str = NULL;

    if (size_ >= LONG_MAX)  //we need (size+1) chars
        return E_FILE_FORMAT_INVALID;

    const long size = static_cast<long>(size_);

    str = static_cast<char*>(mem::Allocate(size+1));

    if (str == NULL)
        return -1;

    unsigned char* const buf = reinterpret_cast<unsigned char*>(str);

    const long status = pReader->Read(pos, size, buf);

    if (status)
    {
        mem::Free(str);
        str = NULL;

        return status;
    }

    str[size] = '\0';

    return 0;  //success
}


long ParseElementHeader(
    IMkvReader* pReader,
    long long& pos,
    long long stop,
    long long& id,
    long long& size)
{
    if ((stop >= 0) && (pos >= stop))
        return E_FILE_FORMAT_INVALID;

    long len;

    id = ReadUInt(pReader, pos, len);

    if (id < 0)
        return E_FILE_FORMAT_INVALID;

    pos += len;  //consume id

    if ((stop >= 0) && (pos >= stop))
        return E_FILE_FORMAT_INVALID;

    size = ReadUInt(pReader, pos, len);

    if (size < 0)
        return E_FILE_FORMAT_INVALID;

    pos += len;  //consume length of size

    //pos now designates payload

    if ((stop >= 0) && ((pos + size) > stop))
        return E_FILE_FORMAT_INVALID;

    return 0;  //success
}

} // namespace mkvparser