Fix IPv4 byte order handling

[FranciscoMaxwell]

Fixes #521.

Summary

This fixes inconsistent byte-order handling in ColumnIPv4:

• Append(std::string) now stores the network-order value returned by inet_pton without applying a second byte swap.
• Append(in_addr) now stores in_addr::s_addr as-is, matching the platform/network-order representation used by socket APIs.
• At() and operator[] now return the stored network-order representation directly.
• Append(uint32_t) and the vector constructor continue to accept host-order integer values.
• Adds coverage proving string, host-order integer, and in_addr appends serialize to the same bytes.

Testing

• cmake -S . -B build -DBUILD_TESTS=ON
• cmake --build build --target clickhouse-cpp-ut --config Debug --parallel 4
• .\build\ut\Debug\clickhouse-cpp-ut.exe --gtest_filter="ColumnsCase.ColumnIPv4*"
• git diff --check

[CLAassistant]

All committers have signed the CLA.

[slabko]

@FranciscoMaxwell

ClickHouse toString function can be used to check if the value you have inserted is correct. The following code automates this process:

struct sockaddr_in sa{};
char str[INET_ADDRSTRLEN]{};
if (inet_pton(AF_INET, "142.251.142.206", &sa.sin_addr) != 1) {
    (void)fprintf(stderr, "failed to convert ip address\n");
    return 1;
}

uint32_t ip = 0x8EFB8ECE;

// check that this is correct ip in host byte order
uint32_t ip_check = 0;
memcpy(&ip_check, &sa.sin_addr, sizeof(ip_check));
assert(ip == ntohl(ip_check)); // `si_addr` is in network byte order

client.Execute("DROP TABLE IF EXISTS addresses");
client.Execute("CREATE TABLE addresses (desc String, addr IPv4) ENGINE = MergeTree ORDER BY desc");

ch::Block block = client.BeginInsert("INSERT INTO addresses VALUES");

auto col_desc = block[0]->AsStrict<ch::ColumnString>();
auto col_addr = block[1]->AsStrict<ch::ColumnIPv4>();

col_desc->Append("142.251.142.206 using Append(const std::string&)");
col_addr->Append("142.251.142.206");

col_desc->Append("142.251.142.206 using Append(in_addr)");
col_addr->Append(sa.sin_addr);

col_desc->Append("142.251.142.206 using Append(uint32_t)");
col_addr->Append(ip);

block.RefreshRowCount();

client.SendInsertBlock(block);
client.EndInsert();


client.BeginSelect("SELECT desc, toString(addr) FROM addresses");
while (auto block = client.NextBlock()) {
    for (size_t i = 0; i < block->GetRowCount(); ++i) {
        auto col_desc = block->At(0)->AsStrict<ch::ColumnString>();
        auto col_addr = block->At(1)->AsStrict<ch::ColumnString>();
        std::cout << col_desc->At(i) << ": " << col_addr->At(i) << "\n";
    }
}

The implementation in master prints the following when running this code:

142.251.142.206 using Append(const std::string&): 142.251.142.206
142.251.142.206 using Append(in_addr): 142.251.142.206
142.251.142.206 using Append(uint32_t): 206.142.251.142

It shows that Append(uint32_t) is clearly broken in master

After applying your fix it prints

142.251.142.206 using Append(const std::string&): 206.142.251.142
142.251.142.206 using Append(in_addr): 206.142.251.142
142.251.142.206 using Append(uint32_t): 206.142.251.142

Showing that all Append functions are now broken.