varint_safe.h

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// Copyright (c) 2024 Clarisma / GeoDesk contributors
// SPDX-License-Identifier: LGPL-3.0-only
 
#pragma once
 
#include <cassert>
#include <stdexcept>
#include <cstdint>
#include <clarisma/util/Bits.h>
 
namespace clarisma {
 
inline uint64_t safeReadVarint64(const uint8_t*& p, const uint8_t* end)
{
    uint64_t val = 0;
    int shift = 0;
    while(p < end)
    {
        uint64_t b = *p++;
        val |= (b & 0x7f) << shift;
        shift += 7;
        if ((b & 0x80) == 0) return val;
        if(shift > 63)
        {
            throw std::runtime_error("Invalid varint (more than 10 bytes)");
        }
    }
    throw std::runtime_error("Invalid varint (extends past end of buffer)");
}
 
inline uint32_t safeReadVarint32(const uint8_t*& p, const uint8_t* end)
{
    uint32_t val = 0;
    int shift = 0;
    while(p < end)
    {
        uint32_t b = *p++;
        val |= (b & 0x7f) << shift;
        shift += 7;
        if ((b & 0x80) == 0) return val;
        if(shift > 28)
        {
            throw std::runtime_error("Invalid varint (more than 5 bytes)");
        }
    }
    throw std::runtime_error("Invalid varint (extends past end of buffer)");
}
 
inline int32_t safeReadSignedVarint32(const uint8_t*& p, const uint8_t* end)
{
    int64_t val = static_cast<int64_t>(safeReadVarint64(p, end));
    return static_cast<int32_t>((val >> 1) ^ -(val & 1));
}
 
inline int64_t safeReadSignedVarint64(const uint8_t*& p, const uint8_t* end)
{
    int64_t val = static_cast<int64_t>(safeReadVarint64(p, end));
    return (val >> 1) ^ -(val & 1);
}
 
inline void safeSkipVarints(const uint8_t*& p, int count, const uint8_t* end)
{
    while(count)
    {
        if(p >= end)
        {
            throw std::runtime_error("Varints extend past end of buffer");
        }
        uint8_t b = *p++;
        count -= (b >> 7) ^ 1;
    }
}
 
} // namespace clarisma